Re: Nobody knows about RR

[Dave Thompson]

Ivar Hesselager wrote:
> I thougt that makers of bicycle tires would have experimentally or
> scientifically based knowledge as a foundation of their production.
> Therefore I directed my question about rolling resistance to
> Continental Tires
> - and the production manager kindly sent me a reply that is
> surprisning as well as interesing.
> The question was:
>
> It has been experimentally established that a 25 mm tire produces less
> rolling resistance than a 23 mm tire of the same model, and with
> identical pressure.
> But how does a comparison between the two tires i.e. 25 and 23 mm -
> each with the recommended pressure (6,5 bar resp. 7.5 bar) come out?
>
> This will be the relevant comparison if you give SPEED priority to
> comfort and tracking.
> Nobody in this newsgroup of bicycle connoisseurs had been able to
> deliver an answer to my question, but a few indicated, that the
> difference in RR between the two tires would be very small and the
> answer thus unimportant.
>
> That did not satisfy my curiousity however, so I sent the question to
> Continental Tires - since it is their 4-Seasons 25 mm I have chosen
> for my long distance speed riding.
> Here is Continental's quick and kind reply:
>
> "The discussion about the differences in rolling resistance between
> 23-25mm tires is somewhat theoretical.
>
> Practically you recognize the better damping and cornering
> characteristics of the 25mm tire.
>
> By experience I can tell you that you won´t be any slower with a 25mm
> tire but have a more enjoyable ride if you prefer to go on backroads
> or even try some field roads.
>
> Wolf vorm Walde
> Product Manager Bicycle Tires"
>
> Thank you for that opinion. I will still be looking for facts.
> I trust, that if mr Walde knew of ane measurable difference, he would
> be willing to tell me about it. Therefore he and Continental Tires
> don't know of a difference. And if they don't know, most likely
> nobody knows. I find that surprising and interesting.
>
> It is obvious that if you give priority to comfort and tracking, you
> should prefer af 25 mm to a 23 mm.
>
> But even if you give priority to speed, the 25 mm tire appears to be
> the better choice. But nobody knows.
>
> Here is an uncovered field for an engineer student or for a bicycle
> magazine to look in to.
>
> Ivar of Denmark
Here's something from Continental regarding folling resistance, with graphs
and numbers. http://www.cyclingnews.com/tech/?id=2005/features/conti_tech As
you can see, the differences are small at best.

 

[[email protected]]

Dave Thompson writes:

> Here's something from Continental regarding rolling resistance, with
> graphs and numbers.

http://www.cyclingnews.com/tech/?id=2005/features/conti_tech

> As you can see, the differences are small at best.

It's too bad these articles are accompanied by horrible graphics. The
cross section of the tire on a rim is nowhere near a realistic
representation of a tire and rim while the contact patches of the
narrow and broad tire could have been real tire imprints from an inked
stamp pad.

These quirks are bad for credibility. If they can't show a relatively
accurate drawing, is anything else they put forth equally approximate?
What are the green lines in the contact patch diagram?

At least their explanation makes sense, but do the numbers?

[email protected]

 

[Jens]

Here, as elsewhere, Conti goes with the claim that the Conti Comp
slightly outperforms the GP3000. But the GP3000 has execrable rolling
resistance -- it takes almost 10 watts more to roll at 40kmh than a
Michelin pro light. So all Conti is saying is that their $100 tubular
outperforms one of the slowest clinchers on the market.

-jens