Rolling resistance vs. power transfer

Triathlon Forum
1

I was just wondering which sucks up more energy. Noodling around on low pressure lower RR tires or pumping them up for better power transfer. Am I way off base?

2

There seem to be some assumptions built into this question that aren’t true, so I don’t know how to respond.

3

I think I’m trying to ask whether there is better power transfer on a high pressure tire, like 220psi tubular as opposed to a 130psi clincher. If there is, is this amount significant? Is it greater than the difference in rolling resistance between the two?

4

Lets not beat around the bush here; Tufo makes horrible tires. Just because you can inflate tire to 220 psi, doesn’t mean it is faster.

http://ddata.over-blog.com/xxxyyy/0/02/72/10/tubular-specs.html

That is Tufo’s at a “normal” PSI. I will have to find the data, but I have seen that there is not a dramatic improvement for them at much higher pressures. Don’t buy into the hype, and get clinchers.

http://ddata.over-blog.com/xxxyyy/0/02/72/10/clincher-specs.html

5

“Tufo makes horrible tires.”

this is a false statement !
they are great training tires
they are round ,not lumpy around the presta valve, long lasting ,tough ,and don’t flat often.

I would race on other tires if I had more money

Dirt

6

I wasn’t even thinking Tufos. I was talking about good tires like Dugasts or something. Or the same tire compared against itself at different pressures.

7

As far as i know, only Tufo has a pressure rating that high. All the other high end tubulars i have come across have a ~8-10 bar recommended PSI rating, which equates to about 145PSI. By the way, Lance Armstrong used to run his rear at 10bar in the rear and 8.5bar in the front when he was doing TTs in the TdF.

8

That seems to point towards my theory. I just used 220psi as an example not as an actual number. Rolling resistance seems to be minimally different between tire makes. Many of the pros run tubulars and there must be a reason. Does anyone know why for sure? Has anyone ever spoken to a pro mechanic or rider? Is it just sponsorship?

9

That seems to point towards my theory. I just used 220psi as an example not as an actual number. Rolling resistance seems to be minimally different between tire makes. Many of the pros run tubulars and there must be a reason. Does anyone know why for sure? Has anyone ever spoken to a pro mechanic or rider? Is it just sponsorship?

If you mean that Crr is minimally different between the best tubulars and clinchers is small, you’re right. If you mean between different brands, you’re completely and utterly wrong. The biggest differences are 15-20 watts.

Pro cylists use tubulars for a number of reasons:

  • Tradition & superstition
  • They don’t need to change tires during races
  • The very best tubulars, properly glued, do roll as fast as the best clinchers
  • Non-puncture flats almost never occur. Around a third of the flats on my training clinchers are from something other than punctures (i.e. pinches, rim tape failure, or the tube rubbing on something inside the rim.)

I think the importance of pressure has been overstated. For a given tire, it actually takes a fairly large change in pressure to make a big difference. Here are some numbers I got for different pressures on a Vittoria KS clincher. This was with a butyl tube too. The differences are smaller with latex tubes. In rough figures, the difference between 120 and 90 psi is barely over two watts at race speeds.

psi Crr
120 0.00421
100 .00436
90 0.00445
80 0.00458
70 0.00474
60 0.00490

–jens