Cycling News tire test

[fa63]

There was a good discussion on the forum recently on the Wind Tunnel Aero testing that Cycling News did. It seems like they have now tested a bunch of tires for their rolling resistance using "a simulated tarmac surface based on a scan of a Paris street" and at speeds that most mortals can achieve (9 m/s or 20 mph and 11 m/s or 25 mph, roughly). All were 28 mm (printed) width tires, except a couple that weren't available in that size (Specialized Turbo Cotton, Challenge Criterium RS, Conti Aero 111), and in that case they used the closest available size. The test pressure was 73 psi (except the Specialized Turbo Cotton which is 26 mm so they inflated that to a slightly higher pressure). Below is a summary of the results, with rolling resistance given in terms of Watts (per tire).

It would have been interesting to test something like the Conti Gatorskin to see perhaps what the "worst-case" scenario might look like But alas, the difference at ~20 mph between the worst performing tire (Pirelli P Zero Race 4 Season) and best performing tire that many use for daily riding (Continental GP5000 S TR) is about 11 Watts per tire, or roughly 22 Watts for the pair (I know weight distribution on a road bike isn't perfectly 50/50 front/rear, but close enough).

I was also surprised the Vittoria Corsa Pro Control did relatively poorly.

And of course, it doesn't matter how fast your tire is if a) you don't care and b) it is so fragile that it flats constantly In this case though, something like the Continental GP5000 comes out looking pretty good as it is a good balance between performance and durability -- I have been riding them for years and while not as supple as Vittorias, I can't remember the last time I flatted on them (I use TPU inner tubes).

[echappist]

Thanks for posting.

What is particular interesting is that some tires that were comparable to cohorts at one speed are slower at higher speeds (see GP5000 AS TR vs its immediate neighbors on the chart)

[Mikej]

Weren’t Veloflex always the fastest? Not included?

[fa63]

Not sure; I agree it would have been interesting to see how they did. The Veloflex Record TLR 25 mm is the second fastest tested tire on Bicycle Rolling Resistance, right behind Vittoria Corsa Pro Speed TLR 28 mm.

Originally Posted by Mikej

Weren’t Veloflex always the fastest? Not included?

[jadmt]

did they do any tube vs tubeless comparisons or tpu vs latex or butyle

[fa63]

They did, just on one tire though. Here are the results for Continental GP5000 S TR at 20 mph:

Latex tube: 9.6 W
Tubeless: 10.0 W
TPU tube: 11.9 W
Butyl tube: 13.9 W

Originally Posted by jadmt

did they do any tube vs tubeless comparisons or tpu vs latex or butyle

[jadmt]

Originally Posted by fa63

They did, just on one tire though. Here are the results for Continental GP5000 S TR at 20 mph:

Latex tube: 9.6 W
Tubeless: 10.0 W
TPU tube: 11.9 W
Butyl tube: 13.9 W

that begs the question would a gp5000 tube type tire show better results than a gp 5000 tr if running a tube?

[fa63]

According to Bicycle Rolling Resistance's data, a tube-type GP5000 with a latex tube should be just about as fast as the TR version running tubeless.

Originally Posted by jadmt

that begs the question would a gp5000 tube type tire show better results than a gp 5000 tr if running a tube?

[Spdntrxi]

there is no way 2 Michelin powercup TLR are 20 watts slower then 5000STR...

says my aerosensor

[fa63]

That was noteworthy indeed; that tire did pretty well when Bicycle Rolling Resistance tested it (although he tests at 8 m/s or 18 mph).

Originally Posted by Spdntrxi

there is no way 2 Michelin powercup TLR are 20 watts slower then 5000STR...

says my aerosensor

[jadmt]

Originally Posted by fa63

According to Bicycle Rolling Resistance's data, a tube-type GP5000 with a latex tube should be just about as fast as the TR version running tubeless.

good info

[Mark McM]

Originally Posted by fa63

According to Bicycle Rolling Resistance's data, a tube-type GP5000 with a latex tube should be just about as fast as the TR version running tubeless.

It should be noted here that Bicycle Rolling Resistance tests tubeless tires with only a minimal amount of sealant (20 ml for road tires), which is less than most riders use (typically 30-40ml). BRR has also tested the rolling resistance with different amounts of sealant, and found that rolling resistance increases with the amount of sealant. Which means that we can extrapolate that if the GP5000 S TR has the same rolling resistance with a latex tube as it does with 20ml of sealant, then this tire will have less rolling resistance with a latex tube than it does with the usual amount of sealant people tend to use.

[NHAero]

So RR doubles when speed goes from 9 to 11 m/s? Why?

[fa63]

Rolling resistance equation is:

RR (Watts) = Crr x Speed (m/s) x Load (N)

So it is a linear function of speed to begin with, and on top of that, Crr also goes up slightly with increasing speed (mainly due to hysteresis):

https://www.bicyclerollingresistance...crr-speed-test

You can also think of Crr as having two components: static Crr (which is not dependent on speed) and dynamic Crr (which is dependent on speed). The Crr in the equation above is a lumped value representing the combination of these two.

[Mark McM]

Originally Posted by NHAero

So RR doubles when speed goes from 9 to 11 m/s? Why?

Interesting question. Rolling losses have to main components - hysteresis losses (in the tires) and suspension losses (due to vibration). One might expect that the hysteresis losses would increase nearly linearly with speed, but do vibration losses also increase linearly, or do they increase at a higher rate with speed?