Fat tires vs Skinny, High vs Low Pressure:

[keithsly]

There are also studies that have shown that a 700 x 25 is faster than a 700 x 23 but racer types won't go bigger than a 23c on the road. The 23's FEEL faster I guess??



http://schwalbetires.com/bike_tires/off-road_tires

Honestly I have both 700 x 23s and 700 x 25s and run them on the same bike (my fixie)...

1. I don't notice a difference between faster or slower on rides...
2. If I have the legs that day I'm fast no matter what tires I'm on !!
3. If you end up flatting because you go to low on PSI then it doesn't matter rolling resistance or wattage or anything... That's why race time it's best to find the right PSI for you, your bike, tire setup and such so you make it the end of most races.. Momma always said you can take air out of your tires but putting it to the right PSI out on the trail is a BEAR !!

Aren't they just trying to sell tires ??

I do like the look and concepts behind their cross tires.

 

[BiknBen]

Someone on here is bound to buy a MTB powertap rear wheel. My bet is that it will be Jim or Ben.

I'm putting my money on Jim. I'm not interested.

 

[jdog]

I have a PowerTap MTN hub on my list of next thing to buy. Using it on the road and for cross has made a HUGE improvement!! However, claiming a 50W increase is actually very bad, that means you're using more power, and we all know using more power is bad. As Normy-poo said, the goal is to use less power and get more speed. Also, just as a side note, the is absolutely NO way anything you will ever do to your bike will ever give you ANY wattage increases.

-Jim.

Good stuff here Jim.

being that you are a skinny tire lover, do you have any thoughts on this report??


J_

 

[clutch]

Well...you won't see wattage gains, you'll see faster speeds at the same wattage. The tires won't actually make you produce more wattage, it will just (theoretically) translate more watts to making you go forward. So fewer of the watts will be lost. Or something like that.

The test rides were run at a "constant" speed of 5.9 mph in order to "eliminate air resistance [sic]". So over the length of his 500 yard grass test track he use 50watts less energy in the best configuration than in the worst configuration. Personally, I don't know anyone who runs 57 psi like in his worst configuration. Also, other than people who race hidden valley, I don't know of too many people doing a lot of riding on grass either.

I'd like to read the actual study, but this document is just a translation of a summary that was put into a German bike magazine.

It's hard to say whether I trust his results or not without seeing the entire methodology. Was he the only rider? Was the test double blind? How many times did he perform each test? Was the test randomized to eliminate the effect of a fatiguing rider? Just too many questions..

 

[warcricket]

the pugsley is a speed demon

 

[Steve Vai]

Good stuff here Jim.

being that you are a skinny tire lover, do you have any thoughts on this report??


J_

A) I don't agree with the patch explanation. You can't run two different width tires at the same psi, skinnier tires require more pressure to maintain the same "feel"...An extreme example would be to put 50psi in a 29x2.4 and then in a 700x23, the 700 feels almost flat whilst the 29 will feel rock-hard, it's not apples-to-apples.

B) There's no way riding on gravel can be that much more effort than grass. In 'cross you go from one to the other and there is very minimal, if any, perceived effort change, yet alone a 100 watt increase!!

Something I can do is actually test the wattage to psi on the cross bike because I'm running my PowerTap on it. I normally run my tires around 35-40psi (700x34) and average just over 300 watts, next time I'll lower my psi and see if that number goes up.

As another note, a few months back when I attended a power training seminar with Hunter Allen, he went over several tricks to do with your bike to get a few watts, 8-10 MAX, if there was a way to get a 50watt savings, I'm sure he would have mentioned it:hmmm:

-Jim.