SRAM HRD Brake Bleeding Guide

Dr David’s guide to bleeding SRAM hydraulic brakes. Having read and tried a variety of methods this is my refined method. SRAM HRD is a closed hydraulic system so all air needs to be expelled. Holding the lever against the bars is important as it empties the master cylinder of fluid and any trapped air.

You will need a SRAM bleed kit plus DOT 5 fluid. Workshop tissue/kitchen roll.

Read through the process fully before starting. Ensure hoses with clamps are secure on the syringe and the clamps will close.

Fill one syringe half full of fluid for the CALLIPER.

Hold with nozzle uppermost. Tap to move air bubbles to the nozzle. Expel all air.

Apply clamp. Pull back on plunger a few times to suck all air from the fluid. Tap syringe. Open clamp and expel the air. Close clamp.

Remove pads. INSERT Bleed block. Unscrew CALLIPER port screw.

Open clamp. Attach the HALF full syringe to calliper. Keep it nozzle downwards at all times.

Remove LEVER bleed port screw. Attach empty syringe to LEVER port. Open clamp.

Push HALF the fluid from CALLIPER syringe.

Discard fluid in LEVER syringe then fill ¼ full with fresh fluid. Use the process above to remove all bubbles from the syringe.

Screw syringe back on LEVER port and push a small amount of fluid from the CALLIPER syringe to the LEVER syringe. Close the LEVER syringe clamp.

Pull in brake lever and hold with strap.

Gently pull CALLIPER syringe (holding syringe with nozzle downwards) to remove air. Then gently apply pressure on CALLIPER syringe to “pressurise” system.

Repeat until no more bubbles.

Remove strap from lever but (VERY IMPORTANTLY) hold lever against bars.

Gently push fluid from CALLIPER syringe while slowly releasing leaver.  Do not force syringe. You should feel the pressure from the calliper syringe pushing the lever out.

Remove CALLIPER syringe and quickly screw in bleed screw.

Open LEVER syringe clamp. Gently pull back on syringe to remove air.

Gently apply pressure to plunger to “pressurise” system.

Pull in and let go brake lever 10 times or more. Gently pull back on syringe until no more bubbles. Repeat the above until no more bubbles.

Gently “pressurise” the system again.

Remove syringe (don’t apply clamp) and screw the bleed screw into the pool of fluid.

Clean up immediately before fitting brake pads.


DOT 5 brake fluid is corrosive. It is neutralised with water. Have plenty of towels to hand to mop up spillage. Wash with plenty water when the job is complete.

Observe the SRAM recommended torque for the bleed screws and calliper pad screw.   

Test braking efficiency before going for a ride.

Download as pdf: SRAM HRD Bleed Guide

Dr David’s pre-ride checklist

Dr David’s pre-ride checklist

Pre-ride – a quick safety check.

  • Brakes – pads – check wear and central on rim/rotor, adjust cable if required
  • Wheels – check for trueness, bearings not worn or loose, quick release is tight
  • Tyres – check for damage, objects in tyre and pump to correct pressure
  • Chain – check wear, damage and clean it then lubricate
  • Cables – check wear, fraying and function

Less often – identify issues early before expensive repairs!

  • Headset – smoothness, play
  • Pedals – tightness, clean, adjust
  • Cleats – wear, tightness
  • Wheels – check spoke tension
  • Bolts – steerer, handlebars, seat post, saddle, brakes, bottle cages, mud guards, gear mechs , jockey wheels, chain rings
  • Gears- check indexing, cassette and chain ring wear, hangar for alignment. Jockey wheel wear
  • Lube – brake pivots and adjusters, quick release, gear mechs, gear cable adjusters
  • Saddle bag – check contents are not absent, damaged or rusty!

Tools required

  • Hex /Torx keys
  • Chain wear tool
  • Rags – especially old socks!
  • Lubricants
  • WD40 or GT85 to clean with

Dr David’s how to’s

Check brake pad wear – pads usually have grooves moulded into them. When they have worn away to a flat surface it is time to replace, especially if less that 2mm of pad left. Visually check the whole length of the pad on both upper and lower surfaces. Remove the wheel to get a better look if required.

Check Rim brake pad alignment – Look from the side and ensure all of the pad contacts the rim braking surface when the brake is applied. Adjust by slightly loosening fixing bolt and twisting to correct angle. Warning – brake pad overlapping the rim can rub the tyre and cause a blow out!

Periodically remove the pads and check for metal and grit embedded into the brake pad. Remove fragments with something pointed like a penknife tip. 

Use the cable adjuster to ensure you can apply full pressure to the brake lever without it touching the handlebars. Before you reach the limit of the threaded adjuster use the cable clamp to pull through some cable.

Check Disc brake pad wear – Remove the wheel and inspect the pads using a torch. There should be 1mm of pad viewed from all angles.  DO NOT USE THE BRAKE LEVER WITH THE WHEEL OUT!  Check  pad wear against manufacturers guidelines. (Shimano“…if the brake pads are worn down to a thickness of 0.5 mm, or if the brake pad presser springs are interfering with the disc brake rotor, replace the pads”.  SRAM – “Inspect your brake pads regularly to ensure that the overall thickness of the individual brake pads measures at least 2.5mm thick including the pad’s backing plate. When a rotor measures less than 1.55mm thick it needs to be replaced.)

Check disc brake lever travel and feel – As disc brake pads wear, cable operated brakes need adjustment. Hydraulic brakes are self-adjusting.  I you need to pull the leaver all the way to the handlebars to stop, you will either need to adjust the cable or for hydraulic brakes they need bleeding (and fluid change).  The feel should be firm not spongy!

Check wheels for true by simply spinning and looking for any side to side movement. Easiest seen between rim and brake pads. If there is a more than a few millimetres of sideways deflection the rim may rub on the brake pads. For disc brake wheels hold a plastic tyre lever against the forks 1-2mm away from the wheel rim and check.  If the rim is bent it will need truing at a LBS (Local Bike Shop).

The wheel should spin freely without any roughness or grinding noises. This could indicate bearings in need of service.  Also lift bike and try to move wheel in a side to side movement to check for play in the bearings. Most wheel bearings are easy to adjust with the correct tools. Or visit LBS.

Ensure the wheel quick release is tight and also not seized.  Typically you finger tighten the quick release screw side while the handle is in line with the axle. You should then be able to push the lever through 90 degrees to clamp closed. Lubricate the QR with winter chain oil and apply a smear of grease to the axle and threads and springs. Periodically remove through axles and lubricate according to the manufacturer’s guidance.

Check tyres for damage and wear. Damage may be obvious like cuts and woven carcase showing or may be a subtle deformity that is only obvious by spinning the wheel. Visually check the tyre. Remove any stones or glass from the tread. This is best done when both inflated and deflated – when you can pinch the tyre to expose the flint/glass. Deep cuts will require a new tyre. Check for wear. If you see any tyre carcase change the tyre!

Tyre pressure.  Most people have their preferred pressure.  Tyres are marked with a min and max pressure. Stay within the manufacturers recommended range. Typical 25mm tyre pressures would be around 85lbs/psi (5.8Bar) to 100lbs/psi (6.8Bar) depending on rider weight. See this Schwable chart.

tyre pressure chart
Schwable tyre pressure chart

Chain wear creeps up on us! Invest in a chain wear tool (less than £5) and use it. By changing your chain at 0.75% wear it is possible to get 2-3 chains per cassette. Let your chain wear get beyond 1% and you will automatically be changing both chain and cassette at the same time (expensive!).

By regularly cleaning your chain (using an old sock and toothbrush) it will last longer as will the front chain rings and cassette. While cleaning, check for any broken or stiff chain links.

Lubricate with proper chain oil with wet lube in winter and dry lube in summer. The part of a chain link that needs the oil is between the rollers. Apply oil to the edge of each roller so that capillary action pulls it where it is required. See Dr David’s chain faq.

Jockey wheels – these should rotate freely and not wobble about. They tend to get a build-up of caked-on oil and dirt. Clean them!  If they are stiff they can be taken apart, cleaned and lubricated. Wobbly bearings need replacing!

rear mech
Rear Mech

Cables wear over time. Visually inspect. Check for smooth function. Replace if worn/frayed. Keep them clean especially around rear dérailleur. A light coating of oil or grease helps prevent rust. Damaged cable outers let in water.

David’s BIG TIP!  For bikes with external cabling it is easy to clean and lubricate the rear gear cable.… Change into largest rear sprocket.  With rear wheel stationary push gear lever as if changing to small sprocket. This will slacken off the gear cable. Now release the cable from the guide on the chain stay. Clean the gear cable all the way up towards the cranks. Now slide the cable outer up the cable and clean the exposed cable. Slide the outer up and down a few times and keep cleaning. Lubricate with DRY chain lube. Replace the cable in the guide and finally turn the pedals. Smooth gear changes restored!

Headset play may manifest as juddering when the front brake is applied or a rattle over rough road surface. On modern bikes the steerer tube is held in place by bearings top and bottom that are held under mild compression. As you can imagine the bottom bearing gets a hammering over rough roads and spray. The top bearing gets wet from sweat and rain! Check for smoothness when turning the handlebars, any grinding or uneven rotation suggests worn bearings. Check for play by applying the front brake and gently rocking the bike forwards and back while looking and feeling for any movement or clicking. Adjustment or bearing replacement entails using a torque wrench. Ask a friend or visit LBS.

Pedals do actually wear out! The bearings may wear or become stiff, the spring-loaded mechanism wears, so does the platform and also under the hoop at the front. If your new cleats are wobbly it’s probably time for new pedals!  Routinely check the tightness of the pedal axles (remember that pedal threads are different from left side and right side. The right side pedal (as you look at it from the outside) has a right-hand thread (removes ant-clockwise, installs clockwise). The left side pedal has a left-hand thread (removes clockwise, installs anti-clockwise). Clean and lubricate your pedals.

Cleats. A not uncommon sight on our roads is cleat bolts and washers! Check the cleat bolts for tightness. Check your cleats for wear. Some brands do have wear indicators. If the cleat feels sloppy in the pedal or looks visibly tatty then replace it.

Wheels – check spoke tension especially if the wheel creaks or twangs while cycling. Also, if the wheel is not true (see above). Pluck every spoke to check they all make a similar note. Loose spokes will rattle or play a lower note. If you have a spoke key, try tightened by ear while making sure the wheel is not buckling. If in doubt see your LBS.

Bolts – steerer, handlebars, seat post, saddle rails, bottle cages, brakes, brake pads, chain rings, mud guards and dérailleurs. Steerer and stem bolts usually have the correct torque setting engraved on the stem. Similarly, the seat post bolt. It is worth investing in a low range torque wrench. You can buy reasonably priced tools pre-set at 5Nm/6Nm. Work your way along the bike checking tightness of all bolts. See pic.

Torque wrench

Gears– If your gears are working well and the cable is not damaged or worn then leave the gears alone!  Visually check the cassette teeth and chain ring for wear. Symptoms of wear are chain jumping and problems changing gear. Visible signs of wear are elongation of the valley between the teeth (B) and, typically on chainrings, sharpening of the teeth (A). By this stage you will require new chainrings and chain and probably cassette – Ouch! See images (X= relatively normal tooth – note relatively long flat top).

cassette teeth
chainset tooth profile

Poor gear changing may indicate a bent rear dérailleur hanger. To correct this, you need an alignment tool or see me!

Lubricate check-list. Brake pivots and adjusters, quick release mechanism, front and gear mechs (parallelogram and cage pivots see diagram), gear cable barrel adjusters, clean and lubricate cable guide under the bottom bracket.

Saddle bag – check contents are not absent, damaged or rusty! Friction between contents can wear holes in inner tubes (from my own experience!). Inner tubes perish. Tools get rusty. Pop some nitrile gloves in there and have clean hands after the next “mechanical”!!

Prevent seized components – every 6 months or so.

Seat post and clamp. Take out your seat post (having wrapped some tape just above the clamp to mark the position) and lubricate with carbon paste for carbon post or frame, grease for aluminium. Don’t forget to lubricate the clamp and bolt.

Handlebar and steerer bolts. These are subject to sweat and rain so remove one at a time, clean, lubricate and replace to correct torque.

Don’t ignore cable adjusters (inline and down-tube), skewers, bottle cage bolts. 

Pedal off – Pedal on!

Pedals take a lot of abuse (weather and crud from the road) and are designed to last for many miles. They are rarely removed before they wear out unless removing for transportation. When it comes to removal many get confused as the left pedal has a “left handed” thread i.e. it tightens anti-clockwise.

Alway use plenty of grease when fitting pedals.

Don’t leave it until the last moment if you need to remove pedals e.g. fitting in a bike box. You may require a lot of force and a large spanner/hex wrench. The weeny multi-tool may not be be up to it.

Don’t forget to pack the tool in the bike box to re-fit the pedals!

Shimano pedals typically use a a 15mm spanner or/and 6 or 8mm hex. Look pedals use 8mm hex.

The image and download below should help.

How to install detailed maps on an older Garmin – for (almost) free!

Maximise the functionality of your Garmin for navigation

This applies to the Garmin Edge 520/705/800/810 GPS devices

I recently helped out one Dittons Velo rider to install a map on her Garmin 810 before a trip to Mallorca. Whilst there, she intended to explore unknown countryside and hills. On her return she loaded a UK map. In three years of Garmin ownership, she admitted that she had never seen a decent map with road names on her Garmin!

If you’re a Garmin user (see list above), it’s likely you’re using the device with it’s very basic map. If all you ever want to do is record an activity – where you have been,  speed and other statistics – then it’s absolutely fine and you can stop reading now!

However, if you want to use your Garmin to navigate a route (there are plenty to download from the DV web site!) you’re going to need a better map; one with road names and more details!


openstreetmapbasemapAs shipped, the above Garmin units come with a “basemap” installed. If you zoom in to the map you see very few details apart from some main A-roads and rivers (compare the images)! On those devices apart from the 520 you can add a detailed map via a micro SD card (see image below).  Newer devices including the 820, 1000 and 1030 have a navigable Europe map factory installed. For 520 instructions see below.

The good news is that maps are easily available: options include purchasing maps on an SD card or via download, from Garmin for £35 (as of November 2018) or Ordinance Survey  1:50k Full Country SD Card for £109.99!

The Free map option…

Alternatively, if you have a microSD card with a capacity of 1GB or larger (I found one in an old phone), you can install the incredible and free OpenStreetMap map
You can buy an 8GB SD card for under £4 online – it doesn’t need to be a digital video, high speed SD etc card.

To install the map you simply need to download the map as a gmapsupp.img file and copy it to the microSD card in a folder named Garmin (there is not enough free space in the main memory). Make sure your computer is set to show file extensions.

sd slot

There are detailed instructions available to follow on the internet e.g.

You can even create custom maps at or download a range of ready-made maps for free at

The Edge 520 has no Micro SD slot and not enough internal memory to add a gmapsupp.img file. A hack is to replace the gmapbmap.img (Garmin base map) file found in the Garmin folder with a gmapsupp.img file that you then rename to gmapbmap.img after saving a backup of the original Garmin gmapbmap.img file.

If you are lucky enough to travel abroad to cycle, simply download and install a gmapsupp.img file for the destination country before you travel (remember to change it back on return to the UK!).file structure

With a 16GB microSD card I keep a number of gmapsupp.img files on the card and simply rename them when required (see screenshot). Note the current gmapsupp.img file in use is a custom area of South of England only.

Happy navigating!

David Matthews

November 2018

SRAM Front Derailleur with YAW setup guide: by David

After struggling while setting up my gears on two bikes with SRAM Force 22, I had to resort to searching the web for guides. Having realised it’s easy when you know how I’ve put together this guide on how to set up the SRAM front derailleur…Success guaranteed!

You will need 4mm and 2.5mm hex (allen) keys. Familiarise yourself with the various bolts (see below) before starting.

Step 1: Height of the front derailleur: Ensure cable anchor bolt is loosened. With chain on the small ring adjust the height of front derailleur so that the outer plate of the derailleur cage clears the tallest tooth of the large chain ring by 1-2mm (loosen front anchor bolt and use a coin or the guide line – as indicated in the illustration to the right).  Use the inner limit screw to position the outer derailleur plate.

Step 2: Turn the inner limit screw (the one nearest the bike frame) while pedalling until the chain shifts up into the large chain ring. If necessary undo the outer limit screw a few turns.

Step 3: Alignment – To properly align Front Derailleur, line up the hash marks at the front and rear of the derailleur cage  (see illustration to the left) with the centre of the large chain ring teeth (even easier if done before fitting the chain).

Use the inner limit screw to make lateral adjustments and the front anchor bolt to make rotational and height adjustments.

Step 4: Set outer limit. Shift into smallest rear cog. Adjust the outer limit of the front derailleur by turning inner limit so there is a 1mm clearance between outer plate and chain. Now turn outer limit screw clockwise until you just feel resistance.

Step 5: Anchor the front derailleur cable. Screw in the the barrel adjuster (often in the cable at the handlebars) to slacken the cable. Make sure the the changer is in the large chain ring position before pulling cable tight and anchoring the cable with the anchor bolt. Take up any slack in the cable using the barrel adjuster.

Step 6: Set inner limit. Use the shifter to release the cable tension by downshifting, as you would for a shift into the small chain ring. Shift the rear derailleur into the largest cog. Back off the inner limit screw while pedalling, to shift the chain down. Continue to back off the inner limit screw until chain noise disappears then turn screw another 45 degrees.

Step 7: Check to see that the derailleur is shifting properly and make small adjustments as necessary to dial in the shifting. Use barrel adjuster as necessary.

Step 8: Install chain watcher so that it is as close to the chain as possible when the chain is in the small chain ring up front and the large cog in the back without the chain watcher actually touching the chain. Slacken the fixing screw slightly and tweak the adjuster screw while applying inward pressure on the watcher then tighten fixing screw. Caution – it may move a little while tightening the fixing screw.

Front derailleur bolts and chain watcher fixing

chain watcher fixing
front mech screws


Having seen a number of methods online, the above is a distillation of a few of them. If seeing a video helps, this GCN video is the closest to the method I describe above.

If you wish to print off a set of these instructions to make it easier in the workshop, you can download this PDF: SRAM FD setup Version 4

Updated May 2020

Preparing for the Prudential RideLondon-Surrey 100

RideLondon training tips by Gerda Mathews

I hope you’ve all applied for the Prudential RideLondon-Surrey 100 for 2018….?

I entered the ballot last year for the first time and got accepted for this year’s ride and it was an awesome experience. Not only because of the closed roads and great support along the route (especially in Esher – thanks DV!), but also because I had trained hard for it. The training made it an enjoyable rather than a painful experience. Considering that I only joined the club in August two years earlier, with a hybrid bike and needed to be rescued by one of the social ride leaders a few times; plus I only starting riding my first road bike in Dec 2015. So all in all, I was very pleased with being able to ride 100miles in a pretty decent time.  I would not have achieved this without the support of the club!

This blog is about how I approached my training and how I managed to achieve my target (well almost; I’m still annoyed about missing my target by just 1 min 57 secs!).

When I got the email to tell me I was successful for the Prudential RideLondon-Surrey 2017, I thought: ‘I have plenty of time for training’ so I didn’t really start with the training plan provided by the organisers (which I should have!). So, February and March came and went and I continued to do the regular Saturday rides with the club. At the start of May I rode in the May Flyer with a group from the club and got a pretty good result but was in real pain: I suffered cramp in my legs and was left feeling quite exhausted after only half the distance. This was my wake up call; if I wanted to achieve my 5hr target in the RideLondon I had to up my game!

However, half of May went by and I still had not done additional training, but then I started to do a few extra sessions: a Wednesday evening training loop with Dittons Velo (thanks guys for dragging me round!) and some spinning classes. In early June, I asked David one of the stronger DV riders if he would ride with me once a week for some speed sessions. I did get better but by mid June I still felt I was lagging. I panicked and did the thing I thought was not possible: I over-trained and actually found myself getting slower!!

After talking to David, my training buddy, he advised to have at least one day a week without exercise. I cut one session out and started to see the benefit from this.

I stuck with my schedule for the rest of June and July. I also did a few sportives, even did one on my own to make sure I had done a 100mile ride before the end of July . I also made sure I did some great rides with the club.

The night before the RideLondon, when I eventually arrived at my hotel (after getting totally lost from Waterloo to Stratford in the pouring rain!), I drank a lot of water to ensure I was properly hydrated, I ate a Nutella sandwich and eventually went to bed.

The morning of the ride I drank more to ensure I was well hydrated, plus I ate granola with yoghurt and one banana. I took a Nutella sandwich with me which I ate while queuing at the start, had another half banana and drank another bottle of water.

For the ride itself I carried with me

  • 6 gels (I used 4)
  • some small flapjacks
  • some cashew nuts (for the salt)
  • some peanut butter sandwiches (cut in mouth size chunks)
  • half a banana (which I didn’t eat!)
  • some Trek Protein Energy Chunks
  • two large bottles of water (with electrolyte tablets)

On reflection, I took too much food and would take less next time. The drink was just about enough but only because I was well hydrated the day before and before the start.

[Note from DV: as a rule, we would normally recommend drinking more water on a hard ride; typically, one bottle per hour]

Sleep is also important but that part went wrong: I couldn’t sleep on the two days before the race and two days after the race. I think excitement and nerves played a big part.

Thank you to everyone in the club for their support and help with my training – I couldn’t have done it without you all.

Dr David’s Secret Sauce

Following from the previous blog post on hydration, energy and salt strategies…

A rough guide to using maltodextrin powderwitches-and-brew

Maltodextrin is ideal for adding to your water bottle as a relatively pure and cost-effective source of energy during a ride. It can be flavoured with your favourite squash with some added salt or used with electrolyte tablets (which could be flavoured).

Maltodextrin is a high Glycemic Index (GI) polysaccharide that is soluble in water and not sweet. It provides a fast acting energy source and is rapidly absorbed and less likely to cause nausea than glucose or sucrose.  It is relatively cheap and used in the food industry. The maximum GI is 100.

Most energy gels contain a mix of sugars including glucose (GI=100), fructose (GI=25) and maltodextrin (GI=100) plus flavours and other additives.

Cost compared to commercial gels

In terms of the cost per gram of pure energy, Maltodextrin costs only 1/10th to 1/20th the price of gels!  (Maltodextrin = 0.27p/g; Wiggle gel =2.1p/g; SIS Go = 4p/g)

Cost compared to commercial powders

SiS Go Energy powder £26: 50g per serving, giving 47g carbs (1.6Kg, gives 32 servings of 50g = 81.25p/serving of 47g carbs = 1.73p/g), meaning Maltodextrin costs a mere 15% of SIS Go Energy powder.



sucralose-3d-ballsMaltodextrin Powder

Each 39g/scoop  (3.8 kcal /g) = 150kcal

2 scoops per 750ml bottle = approx 10% (300kcal)


Typical Usage


Try to drink 500ml of fluid (an energy drink or fruit juice) 45-60mins before exercise.

If you’re having breakfast before the ride, make sure it’s at least 1hour before – porridge is always a good choice. Don’t drink large quantities otherwise you’ll be stopping every 5 minutes for a nature break.


During exercise

popeye-spinachIdeal is around 60g low GI carbs (288 Kcal) per hour and 600mg Sodium.

That might look like this:

Summer drinks 5% (1 scoop) plus Sodium 700mg (2g salt)

Winter drinks 15% (3 scoops) plus Sodium 500mg (1.3g salt)

Drink 625-1250ml per hour (one to two bidons per hour…yes, that much!) – depends on weather, the person, how hard you’re riding.


Post exercise

When you get off the bike, you will be in energy deficit so I recommend you consume 75g High GI carbs (330kcal) immediately after the ride and another after 1hour to make up deficit of calories. Also protein is essential to rebuild damaged muscle fibres.



1litre of sweat contains up to 1g of sodium (=2.6g of table salt). Sweat loss can be 500ml – 1L per hour

Table salt contains 387mg/g. So 1 teaspoonful = 6g = 2300mg

Energy gels generally contain 22-30g carbs which is 80-115kcal plus Sodium 10-40mg. So 2-3 gels per hour will supply the maximum calories one can absorb but not enough Sodium.

High GI carb intake after exercise stimulates Insulin release that encourages muscle growth and thus strength! 

Useful links for further information:




Cycling hydration: it’s not all about water and coffee

Hydration, energy, salt and food strategies for longer, harder rides

by our own Dr. David 


Water: am I drinking enough? Probably not…underwater-cycling

Roughly 60% of the human body is water, so to guarantee peak performance on the bike it is important to maintain the balance. During exercise your body loses water in the form of sweat (mainly), urine and water vapour through breathing (ask a dog!). Evaporation of sweat from the skin is the main way your body sheds heat. Without that cooling the increase in your core body temperature (from heat generated by your working muscles) would kill you fairly rapidly.

To determine your sweat rate, weigh yourself before and after a typical 1 hour ride without a drink (naked, dry with empty bladder before and after). Most riders will typically lose 500-1000 ml per hour.  If you’re at the upper end of this range, it might not be practical or necessary to try and replace it all but you should aim for a minimum of 75%.

Surprisingly small fluid losses can significantly affect your performance. A 2% drop in body weight due to sweating (1.6 kg for an 80 kg rider) will impair performance noticeably. Studies carried out in cool laboratory environments have shown a 5% decrease in VO2 max with a 3% decline in body weight through dehydration. At 5%, heat exhaustion can become an issue and your capacity for work will drop by up to 30%. Hit 7% and you’ll start experiencing hallucinations and, at 10%, circulatory collapse, heat stroke and even death become possibilities.

The physiological reasons for performance losses due to dehydration are:

  • Reduction in blood volume
  • Decreased skin blood flow
  • Decreased sweat rate
  • Decreased heat dissipation
  • Increased core temperature
  • Increased rate of muscle glycogen use
  • Decreased digestive function

So, what does all this mean I should do…?

In the hour leading up to a long ride sip 500-750 ml (one full bidon*) of fluid (* bidon = your water bottle)

Drink at least 500ml (one bidon) per hour on the bike. Don’t wait until you’re thirsty but drink but little and often right from the start of your ride. Aim to take 2-3 good sized gulps from your bottle every 10-15 minutes right from the moment you set off. You’re not drinking for that moment but to ensure your body stays properly hydrated 10-20 miles down the road.


During heavy exertion calorie consumption can range anywhere from 600 to 1500 kcal/hour. Energy consumption will vary depending on many factors e.g. the size of athlete, intensity of exercise, climatic conditions and level of fitness.

It has been shown that an average athlete can only readily absorb (process) between 200-600 kcal/h resulting in a negative energy balance. For longer rides, it makes sense to combine drinking with calorie intake. Remember, for a sportive or long training ride, you’re aiming for 0.5-1g of carbohydrates per kilogram of bodyweight per hour and should aim to spread that over 2-3 micro feeds every 20-30 minutes.

500 ml of typical sports drink mixed at 6% will give you 30 g of carbohydrate which, for an 80 kg rider requiring 40-80 g per hour, is a decent and easy to take on proportion of that energy requirement.

Energy gels generally contain 22-30g carbs which is 80-115 kcal. So 2-3 gels per hour will supply the maximum calories one can absorb but may cause nausea.

Maltodextrin is a non-sweet high GI sugar ideal for supplying energy during cycling. I’ll share more thoughts on the use of maltodextrin in my next blog along with recipes for making up some lower-cost energy drinks.


Much has been made about combining fructose with other high GI sugars e.g. glucose and maltodextrin in energy drinks and bars. One study suggested a benefit but this has not been substantiated. In fact fructose is much harder to digest and may slow stomach emptying and actually reduce energy absorption!

My simple advice to get the energy you need on the bike

  • Use both energy gels AND energy in your drink (don’t just carry water in your bidon) 

Ideas for consuming adequate energy during a longer ride: bike-overloaded
The following are examples of how to take on 60-80g of carbs per hour

  • 400 ml of energy drink mixed at 5% solution (35 grams) + one energy bar (35 grams) = 70 grams
  • 800 ml of energy drink at 6% solution = 70 grams
  • 3 energy gels (25 grams each) = 75g
  • 3 bananas (25 grams each) = 75g (you’d need a big pocket in your jersey!)

You can neither carry nor digest 10-12 bananas in one 3-4 hour ride….so, a mixture of the above options is possibly the best strategy e.g. two full bidons of energy mix, a banana or two, plus a handful of gels. Take a few electrolyte tablets then add them to your water when you refill the bidons at the half-way cafe stop.

Salts: when do I need them, and how should I get them?


Sodium concentration in sweat varies from person to person but is typically 1g/litre. Sodium loss will vary depending on many factors e.g. the size of athlete, intensity of exercise, climatic conditions and level of fitness. Sweat loss can be between 500ml – 1L per hour (500mg – 1000mg of sodium) – you can generally expect to lose more in summer, less in winter.

1 litre of sweat contains up to 1g of sodium (= 2.6g of table salt).

Table salt contains 387 mg/g. So 1 teaspoonful = 6g = 2300mg

Energy gels generally contain carbs plus sodium 10-40mg. So 2-3 gels per hour will supply the maximum calories one can absorb but not enough sodium (30-120mg).

Table salt, electrolyte tablets or food will be required to replace sodium loss. Electrolyte tablets typically supply 250 -360mg sodium.

My advice

  • Use both electrolyte tablets and carbohydrates in your water
  • Consider eating salty snacks on long rides


Magnesium: do I need it?

Magnesium seems to be “en vogue” with promises of increased performance and reducing cramp. While many studies on magnesium supplementation and exercise have been carried out, the results have been inconsistent and may indicate that there is nothing to be gained by supplementing an already magnesium-sufficient diet.  But for those already deficient in magnesium increasing magnesium in the diet may improve performance.

My advice

  • There is no hard evidence for consuming magnesium during exercise



The exact reason for cramping is still unknown. Many people blame inadequate hydration or electrolyte levels and, although some studies have shown that consuming a 6% carbohydrate sports drink can help prevent them. Regular training does improve the time before the onset of cramp.

My advice

  • Ensure adequate fluid and energy intake. Nothing beats regular training to help endurance!


Protein: can I digest it during a ride, or is it only for recovery?

During a long ride at high-intensity your body burns glucose from its glycogen stores (and digestion) as the preferred energy source. When this is depleted (mine lasts approx. 2 hours at anaerobic threshold) it will look to other sources of energy i.e. fat and protein. These both require a lot more oxygen to obtain the energy from the longer molecules.  Recent research on 10 trained cyclists performing an 80K trial showed that riders drinking carb-only did just as well as those drinking carb-protein drinks, and both groups did better than those consuming flavoured water!

If you’re on a long ride where you’re also eating, you’ll be taking in protein already so it’s unnecessary to also have protein in your drink.

My advice

  • Save protein for your recovery drink
  • There is nothing to be gained from consuming drinks containing protein during a ride


Fats and fibre

The pies and sausage rolls in the farm shop may look like a good source of energy when you are feeling the hunger pangs after riding over the North Downs but they take a long time to digest and will actually slow down the absorption of the carbs you need to get you home. The same applies to fruit and muesli bars.

My advice

  • No meat pies. A jam sandwich would be better
  • Not too many bananas


Caffeine: to caffeinate, or not to caffeinate, that is the questioncoffee-beans

Caffeine improves carb burning. Researchers found that riders who drank a caffeinated sports beverage burned the drink’s carbs 26 percent faster than those who consumed a non-caffeinated sports drink, likely because caffeine speeds glucose absorption in the intestine.

Also worth noting that the stimulant doesn’t worsen the effects of summertime heat. In fact, caffeine makes you feel better. Numerous studies have shown that it lowers your rate of perceived exertion while improving your strength, endurance and mental performance.

My advice

  • Drink coffee!
  • Stop for coffee!

My next blog will be a recipe for making your own cost-effective cycling drinks using maltodextrin.

Enjoy your cycling

Some links if you wish to read more on the topic


Disclaimer: Please note the information in this article has been researched in good faith or from my experience and is for guidance only and not medical advice.

David Matthews – Nov 2016

Roll on: Part 2 of EVERYTHING about Tyres

This is the second part of the two part FAQ feature on bike tyres from Dr David
If you haven’t read the first one, I recommend you see it here before reading this second installing episode…
By the way, some people have responded to ask: so which tyres do I buy? As before, we’re not telling you the right brand, but if you want to know a selection of what we use, contact us and we will drop you a list

Click to see a larger version of this graph

Rolling resistance Some tyres roll faster than others and sometimes you can feel the difference. As stated in the previous blog, the faster you go the more wind resistance is the overriding factor slowing you down. As the drag due to wind resistance increases with the square of the velocity, the frictional losses of bearings, chain and tyres pale into insignificance. But why waste 40 watts on inefficient tyres? Tyre construction and pressure play an important part. Fine flexible tyres that deform easily are more efficient than thicker walled tyres. Extra puncture protection layers may also increase rolling resistance.

The Coefficient of rolling resistance (Crr) has been studied and quoted by numerous web sites and manufacturers. The study methods are never the same but there are some group tests. Looking at this chart you could lose 20 watts per wheel by using a GP3000 rather than an Open Corsa Evo CX!

Softer rubber compounds generally grip better than hard. But who wants a tyre that is super grippy and only lasts 500miles? One solution is to have a harder compound in the centre of the tyre and soft compound on the sides of the contact area to give grip in the bends e.g.Vredestein Fortezza TriComp. There are dual and tri compound tyres available especially as winter tyres. Continental promote their “Black Chilee” compound which seems to come out well in tests but there are others.

Lightweight tyres will accelerate better but generally are less robust and wear out faster. Not all lightweight construction will have a lower Crr though.
Winter tyres. The rain and wind spread all sorts of rubbish onto the roads so puncture resistance is essential. Various manufacturers have their own solutions including Kevlar, Duraskin, V Guard etc. When the rain comes we want grip so a good compromise is dual or triple compounds.

Butyl vs. latex inner tubes
As the tyre rolls it deforms which affects its rolling resistance. The inner tube has to be deformed as well and there is friction between the tube and the tyre. More flexible and lighter latex tubes are more efficient and produce a lower Crr by 10% but this is dependent on weight. Latex tubes are more porous so go down faster. They are also more prone to failure due to contamination with oil etc and they have been known to explode!  Read about the myths of punctures.
Some say they are more comfortable.

Wrapping up
It is all a matter of compromises. A few points stand out though:

  • 25mm is the way to go unless you are time trialling
  • Use the spreadsheet to work out ideal pressures
  • Do not over-inflate tyres
  • If your ride is uncomfortable and you are vibrating then they are overinflated
  • Some tyres roll faster than others
  • If you keep getting punctures it is time to try another tyre
  • Use tyres that you are comfortable with and have confidence in.

References/ further reading:

2014: will it be a Goodyear? EVERYTHING about bike tyres

Dr. David continues his series of useful tips on keeping your bike in tip-top shape. This article covers everything you need to know about bicycle tyres and is being published in two installments. Here is the first:

Welcome to my cycle tyre FAQ Part 1

First thing to say is, I’m not going to recommend any specific tyres. We all have our favourites!

Tyre pressure – is higher better?
Yes and no!

On a smooth surface in a lab, higher  pressure can mean faster but the benefits get smaller the higher you go, especially over 130psi (pounds per square inch). Lower pressures are more comfortable and by allowing the tyre to squash more provide a larger surface area in contact with the road and hence more grip. As the rolling resistance of a tyre is mostly produced by the friction in deforming the sidewall then underinflated tyres waste energy. Some people have studied the ideal pressure for performance and grip and came up with the 15 percent rule.

Download the Bike Tyre Pressure Calculator – (created by Bike Tinker)


How much pressure?
100psi means that the air in the tyre is exerting an outwards force of 100lbs per square inch. So if you load that wheel with 100lbs the tyre will deform to a contact area of 1 square inch to carry the load. A lower pressure of 50psi will require 2 square inches to support the 100lbs load. That’s why giant mining earth moving trucks have very large tyres which spread the many tonnes over a large area. Too low a pressure will mean pinch or “snake bite” punctures.

The weight of a cyclist is more over the rear wheel so that needs to be a higher pressure than the front. Time trial bikes move the rider forwards and may put more weight on the front wheel. If necessary weigh the front and back wheels with you in your riding position.

It seems that to go faster, you need high pressures. Track bikes may use in excess of 220psi on the smooth wooden velodrome but road tyres often have a maximum recommended pressure of 120-135 psi. On uneven roads, high pressures make the tyre roll up and down every little bump effectively going up and down tiny hills and shaking the bike. This uses energy and slows you down. Having some give in the tyre and smoothing out the rough road surface improves rolling resistance. Importantly, added to this is the effect on the power source (cyclist) that vibration drains power sometimes by hundreds of watts (the tank driver effect).
See this article for more on tyres and pressure.

23mm v 25mm which is faster?
For the same tyre pressure a 25mm tyre has less rolling resistance. Seems a bit odd, but true. The slimmer the tyre the longer the contact patch and the more of the sidewall is deforming and therefore wasting your energy. But the faster you go the more wind resistance becomes the dominant force you have to cycle against. So a narrower tyre gives less wind resistance especially on the front. Also, 23mm tyres can be run at higher pressures. In general 25mm is a better all-round tyre.


TPI – is higher better?
High threads per inch is often seen as a mark of a better tyre. The carcase is made up of woven material which is then impregnated with rubber. Cheap tyres will have fewer, thicker, fibres probably of nylon while lighter expensive tyres will have a very fine weave often made of cotton. Lightweight cotton is less resistant to sidewall punctures but is lighter and more flexible and hence faster. Thicker nylon is much more resistant to wear and punctures. Finer more flexible tyres roll faster due to less energy wasted in deforming the tyre.

Most racing tyres are smooth and some winter tyres have a tread. For riding on a road tread is not required for grip. Obviously off-road tyres need a knobbly style tread to grip earth and mud. Car tyres are wide and have a flat radial tread formed by steel belts. They need tread to allow water to escape from between the tyre and a wet road to prevent aquaplaning. Bicycle tyres are narrow and cut through the water so a tread is not required. As with many things, Sheldon Brown’s site has some useful information on this.
Smooth tyres roll better than coarse treaded ones.

The next part of Dr. David’s tyring blog will reveal the truth about rolling resistance, the choices of compound and weights for a tyre, and inner tube choices —