Tubulars vs Clinchers…

15 Apr
Corsa Tyre

Vittoria Open Corsa EVO CX II - Fine Italian Racing Rubber

Okay I’ll admit it… I’m an internet addict! More specifically I’m an internet cycling and triathlon forum addict. I read TriTalk, Slowtwitch and Cycling News on at least a daily basis. The number one topic that comes up time and time again is the now infamous Tubulars vs Clinchers. I have posted and will probably continue to post on the subject as surprise I have an opinion. Of course I think it’s the right one :-).

So I’ll weigh in here with my opinion and if nothing else then at least I can copy and paste it into my posts on forums in the future. Hopefully someone will stumble across this at some point and be able to make an informed choice too. I’m an engineer by training so at least vaguely understand the science behind it rather than the years of hearsay that gets bandied about.

This gets lengthy so by all means skip right down to the conclusion!

So lets start by defining what a Tubular and a Clincher tyre is:

Tubular Tyre (from Wiki):

A tubular tyre, referred to as a tub in Britain, a sew-up in the US, a single in Australia, or just a tubular is a bicycle tyre that is stitched closed around the inner tube to form a torus. The combination is then glued (sometimes with two-sided tape) onto a specially designed rim, referred to as a “sprint rim” in Britain, and just a “tubular rim” in the US, of a bicycle wheel.

Clincher Tyre (from Sheldon Brown):
Conventional tyres used on 99% of all bicycles are “clincher” type, also known as “wire-on.” They consist of an outer tyre (the “casing”) with a U-shaped cross section, and a separate inner tube. The edges of the tyre hook over the edges of the rim, and air pressure holds everything in place.

One of the major things that influences this discussion is the Rolling Resistance of the respective tyres.

Rolling Resistance (Crr)

The rolling resistance of a tyre can be thought of as how much energy it takes to propel it across the ground. The more energy it take the harder you have to work! This energy can be expressed in Watts (W) or also as it’s coefficient of rolling resistance (CRR). Crr also can be used to calcuate how much energy you need to propel the tyre or how much time it can take to move from point A to point B on a bicycle. The lower (smaller) the number for Crr the better. You can find the most extensive independent list of the Crr of tyres at Bike Tech Review. From this you can make a choice based on your own personal needs and budget. Typically tyres with higher levels of puncture resisitance are lower down the list and slower than full on racing tyres. These test are done on a set of smooth metal rollers and the data then adjusted for a smooth road. There has been some more testing done on typical road surfaces and you can reliably multiply the Crr and Watts by about 1.3 as a rule of thumb.

My own choice is a pair of Vittoria EVO Open Corsa CX II clincher tyres. I have a 20mm front and a 23mm rear. They are fairly high up the list, have some puncture protection and roll really well.

Watts (W)

Watts is simply a measure of the energy needed to propel a bicycle at a given speed hence how much work you have to do. Much of the work that you have to do when riding a bike is in overcoming the wind resistance that you the rider create, it’s something like 75-80%. The rest of it is made up of the wind resistance of the bike and wheels, mechanical losses in the drivetrain and overcoming the rolling resistance (Crr) of the tyres. As a rule of thumb either working 10 watts harder or saving 10w in wind resistance will save you 40 seconds over the course of a 40km (25mile) time trial, or a standard distance triathlon bike leg.

Inner Tubes

Part of the reason that tubular tyres are typically thought to have a lower Crr is that the good ones have latex tubes inside them. These are thinner and lighter than the black butyl rubber ones that most people are familiar with. They are also much more elastic and conform better to the shape of the road thereby reducing Crr. The downsides to latex is that it is more porous than butyl and tyres need to be pumped up more frequently. You can however buy latex inner tubes for clincher tyres. They are a bit of a pain to fit but save about 3-5 watts per wheel depending on the road surface. That’s a significant amount as outlined above.

For example using the Bike Tech Review data above we can look at the data for Vittoria Corsa tyres

Vittoria Open Corsa CX II Clincher (with latex inner tube) – Crr = 0.00250, Watts = 12.3
Vittoria Open Corsa CX II Clincher (with butyl inner tube) – Crr = 0.00307, Watts = 15.1
Vittoria Corsa CX II Tubular – Crr = 0.00254, Watts = 12.5

As you can see by adding a latex inner tube to a good racing clincher tyre you can bring down the Crr to that or lower than that of an equivalent tubular. However that statement is only true if the tubular is properly glued to the rim…

Gluing Tubulars

Tubulars need to be glued to the rim of the wheel. Alternatively they can be attached via double-sided sticky tape. To gain the best possible Crr the tubular tyre needs to be properly glued to the rim to the extent that it becomes virtually impossible to remove the tyre from the rim if a puncture occurs during a race. This is fine if you have a team car following you with spare wheels or that if you puncture you’re out of contention anyway but not so good if you’re trying to finish. If you don’t believe me then read the pdf at the Bike Tech Review link above or even better go to Gluing Tubular Tyres and read the links there. Al Morrison who has conducted the tests at Bike Tech Review states that he believes that an lightly glued or taped tyre will add 0.0004 to Crr. So lets go back to our example tyre and see what effect that would have.

Vittoria Corsa CX II Tubular (properly glued) – Crr = 0.00254, Watts = 12.5
Vittoria Corsa CX II Tubular (lightly glued) – Crr = 0.00294, Watts = 14.4

A fairly significant difference of 1.9W per wheel! So what does that mean, remembering that we can multiply results by 1.3 for typical real world road surfaces and using our rule of thumb for Watts and time savings of 10W = 40s over a 25m TT.

Standard Triathlon or 25 mile TT = 1.9 x 2 x 1.3 = 4.95W = 20 seconds slower
Ironman Triathlon (112 miles) = 90 seconds slower

There is an additional problem with replacing tubular mid race – tubular glue takes 24 hours to cure. This means that the tubular will be very poorly adhered to the rim making the Crr even worse and the rider would be have to be very cautious whilst cornering and braking. Loosing even more time than stated in the example above.

Weight

One of the arguements you will typically hear for tubulars is that they are lighter and therefore faster than clinchers. Typically tubular wheels are lighter than an equivalent clincher wheel sometimes by up to 300-400g. Lets look at some popular wheelsets (weight given is for both front and back wheels):

Zipp 404 Tubular – 1278g
Zipp 404 Clincher – 1658g
Zipp 404 Carbon Clincher – 1557g

HED Jet 6 Clincher – 1849g
HED Stinger 6 Tubular – 1440g
HED3 Clincher – 1903g
HED3C Tubular – 1615g

So then lets look at the weight of the wheel tyre combo using the Vittoria Corsa as it’s available in both Clincher and Tubular variants and adding inner tubes and rim tape in the case of clinchers. I’ll use the Zipps for the example.

Zipp 404 Tubular – 1278g
Vittoria Corsa Tubular x 2 – 490g
Tubular Glue – 40g
Total Weight – 1,808g

Zipp 404 Clincher – 1658g
Vittoria Corsa Clincher x 2 – 390g
Latex Inner Tube x 2 – 150g
Total Weight – 2198g

On the face of it the tubular combo is around 400g lighter, however add in the weight of a spare tubular at around 245g and it looks a little different. If you want to carry a couple of spares then the clincher combo is now lighter than the tubular! Remember also from our examples above that if the tubular is glued lightly to allow removal mid race then it’s Crr suffers and the equivalent clincher tyre is faster. How much faster does saving 300 grams make you? Well, given a lightly glued tubular and a clincher with latex tube some analysis has been done to show that this makes no difference until sustained gradients of over 8% are encountered. Unless most of your race is going uphill or it’s an uphill TT then overall the clincher will be faster due to it’s performance on the flat sections and downhill.

Conclusion

For the vast majority of age-group athletes tubulars simply do not make sense. A good modern clincher tyre with a latex inner tube has a similar rolling resistance to a properly glued tubular. If a tubular is glued properly to benefit from the lowest possible rolling resistance then it is not practical to remove the tyre from the rim in the event of a puncture. If the tubular is lightly glued to allow removal during a race then the rolling resistance suffers and an equivalent clincher with latex inner tube is faster by around 20 seconds over 25 miles and 90 seconds for an Ironman. The weight difference between a clincher wheel and a tubular wheel can be negated if the rider on tubulars is carrying spares and even given a 300g weight difference a clincher wheelset is faster than a lightly glued tubular wheelset for gradients up to around 8%, with most races being not exclusively uphill so this will be more than negated by the clinchers performance on the flat and downhill.

If you are a front of race athlete looking for marginal gains and where a puncture would mean that you are out of contention by all means run properly glued tubulars. Everyone else should be on clinchers and using latex inner tubes when racing.

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One Response to “Tubulars vs Clinchers…”

Trackbacks/Pingbacks

  1. Best Clincher Tires / Tyres « Running With The Black Dog - May 27, 2011

    […] having another look at what a clincher tyre is or if you have time have a quick read of my post on Tubulars vs Clinchers which explains most […]

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