Jonathan Bond wrote:
>
>
> G.T. wrote:
>
>> Ken wrote:
>>
>>> "G.T." <
[email protected]> wrote in
news:[email protected]:
>>>
>>>> I'd go with the 1 1/4. The only benefit of narrow tires is the ability to run 110 psi and up.
>>>> At a given pressure fatter tires have less rolling resistance (due to less hysteresis).
>>>
>>>
>>>
>>>
>>> While that partially is true, it is not a valid argument. If two tires have identical
>>> construction, except that one is wider, you should *not* run them at the same pressure.
>>
>>
>>
>> Why not? If the max pressure on a 1" tire is 140 psi and it's 100 psi on a 1 1/4" tire but you're
>> only planning on running 100 psi why can't you run the 1 1/4" at 100 psi?
>>
>>> The narrower tire will have a higher optimal pressure and thus a lower rolling resistance. The
>>> wider tire will weigh more and roll slower, but give you a plusher ride, especially on rough
>>> roads.
>>>
>>
>> And the wider tire has less rolling resistance at the same pressure just like I said (due to less
>> hysteresis). The wider tire will roll faster than the skinnier tire at the same pressure. Did you
>> read what I said? "At a given pressure fatter tires have less rolling resistance".
>>
>> Greg
>>
>
> Not sure if I can get my head around that one. You're saying that if I had a 1 meter wide tire,
> and a 1cm wide tire (assuming smooth tread), then the 1 meter wide tire will roll faster, not
> taking int account weight and momentum? The tire is going to have a larger contact patch, which
> means more deformity of the tire with the surface its on, which means more energy loss (hence more
> hysteresis). Granted, it'll have massive grip, but not sure if I agree with your statement. I'm
> probably wrong, and would love to be proved so, but I can't get my mind around that one.
>
I interchanged "less rolling resistance" and "rolling faster" because I was talking about tires of
only 1/4" difference in width and assuming they would be constructed similarly. A 1 1/4" wide tire
at 100 psi (if it's rated for 100 psi) will roll faster than a 1" wide tire at 100 psi if they are
constructed similarly. This is tires 101.
http://draco.acs.uci.edu/rbfaq/FAQ/8b.14.html
The reasons narrower tires usually have less rolling resistance is that they are usually constructed
differently than wider tires. If you take a Conti Grand Prix 25mm and a 20mm and inflate them to 95
psi the 25mm is going to be faster. This isn't specifically mentioned in the r.b.t. FAQ but this has
been discussed at length on r.b.t. I was schooled on this long ago.
Greg
--
"Destroy your safe and happy lives before it is too late, the battles we fought were long and hard,
just not to be consumed by rock n' roll..." - The Mekons
