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Skinny Tires suck while at least on a MTB. - Page 2

post #31 of 52
Quote:
Originally Posted by epic View Post
Guys, they measured the amount of power used with an SRM.It's not just theory, they have results.
I don't disagree with their data comparing low vs. higher pressure in the same wide tire. I was only questioning their data on the narrow tire vs. wide tire issue, because the study design is definitely flawed by using the same pressure in both. Narrow tires need to run with higher pressures, by design, but they didn't test it at a higher pressure, they tested it at a the same low pressure as the wider tire. The results for that particular comparison are therefore meaningless.
post #32 of 52
Thread Starter 
Quote:
Originally Posted by exracer View Post
I don't disagree with their data comparing low vs. higher pressure in the same wide tire. I was only questioning their data on the narrow tire vs. wide tire issue, because the study design is definitely flawed by using the same pressure in both. Narrow tires need to run with higher pressures, by design, but they didn't test it at a higher pressure, they tested it at a the same low pressure as the wider tire. The results for that particular comparison are therefore meaningless.
they ran a 2.1 at 60 psi ran a 2.4 at 60 psi and ran 2.1 at 21psi and a 2.4 at 21psi. and alot of pressure in between. it also seems that they used the same tread design.

The lowest rolling resistance was on 2.4 at 21psi. even when you take into account the extra weight of the 2.4 is still requires a lower wattage to pedal.

in fact the 2.4 at 21 psi requires 50 less watts to pedal than a 2.1 at 60 psi on a grassy surface.
post #33 of 52
I think this study is a lot like comparing a full suspensions climbing ability to a hard tail.

A car, truck, or motorcycle with suspension will outclimb a comparable vehicle with no suspension.

In theory at least, a full suspension MTB should out climb a hardtail.

Most cyclists will agree they would rather ride a hard tail, for its climbing ability over a full suspension. I agree with this.

For overall comfort and ride I chose a full suspension.

I also agree that my fat tires will out perform a skinny one over the terrain I like to ride.

I disagree that a fat tire will roll easier than a skinny one at the tire pressure they are intended to run at.
post #34 of 52
Thread Starter 
Quote:
Originally Posted by Johnnys Zoo View Post
I think this study is a lot like comparing a full suspensions climbing ability to a hard tail.

A car, truck, or motorcycle with suspension will outclimb a comparable vehicle with no suspension.

In theory at least, a full suspension MTB should out climb a hardtail.

Most cyclists will agree they would rather ride a hard tail, for its climbing ability over a full suspension. I agree with this.

For overall comfort and ride I chose a full suspension.

I also agree that my fat tires will out perform a skinny one over the terrain I like to ride.

I disagree that a fat tire will roll easier than a skinny one at the tire pressure they are intended to run at.
http://forums.epicski.com/showthread.php?t=72159

over there for the HT vs FS

as for the fat tires rolling easier this is indisputable, it was measured scientifically
post #35 of 52
I suggest you read this...

http://en.wikipedia.org/wiki/Rolling_resistance

and this...

http://www.energy.ca.gov/2006publica...006-003-FS.PDF

From Sheldon Brown
Rolling resistance does decrease theoretically with any increase in pressure, but with modern, high-quality tires the rolling resistance at CORRECT inflation pressure is already so low that the infinitesimal reductions gained are more than outweighed by the trade-offs.

A common debate among cyclists centers on the issue of whether a wider tire has more or less rolling resistance at the same pressure. The constant pressure is proposed because it appears more scientific to eliminate this as a variable, but this is not realistic in practice. The short answer to this question is that, yes, a wider tire of similar construction will have lower rolling resistance than a narrower one at the same pressure. This fact is, however, of no practical value. If you are comparing two tires of similar construction, with the same load, and the same pressure, either the wider tire is overinflated, or the narrower tire is underinflated!



This is not new, interesting, but not new. A lot of variables they tried to minimize but they still account for a 'real world' difference. Wind resistance, tire tempeture, deflection over irreguar surfaces, tread thickness, etc.

JZ
post #36 of 52
Quote:
Originally Posted by Johnnys Zoo View Post
Most cyclists will agree they would rather ride a hard tail, for its climbing ability over a full suspension. I agree with this.
I don't.
post #37 of 52
Quote:
Originally Posted by Johnnys Zoo View Post
This is not new, interesting, but not new. A lot of variables they tried to minimize but they still account for a 'real world' difference. Wind resistance, tire tempeture, deflection over irreguar surfaces, tread thickness, etc.

JZ
We aren't talking about 1 or 2 watts here. It's a significant difference that they are measuring. Anyway, run whatever tire you want at whatever pressure you want to. It's not worth arguing about.
post #38 of 52
Quote:
Originally Posted by Johnnys Zoo View Post
IRolling resistance does decrease theoretically with any increase in pressure,JZ
Only on roads. Once you are on gravel, the curve inverts. Read the article Bushwacker cites. It is dead on.

http://www.bicicletta.co.za/Download...llustrated.pdf

I've been telling friends their tires were too hard for years. This year I'm running 2.5's at about 20 psi on my 29'er and just gliding over stuff.
post #39 of 52
I'm not arguing, just trying to make a point. BWPA probably thrives on this....

The study is really not scientific. Its not been critically reviewed for one. That is essential for any 'scientific' study. The parameters were never defined. They measured watts, probably with one of those hub mounted generators. Those devices are for calulating human output. It wasn't designed for this type of testing. They aren't really intended to test machines. They should have used a dynamometer. Given a torque curve readout. Why 80 something trials? Why did they pick this number? If I remember my stats right it takes 286 trials to be considered a true test. Did they average the trails? Use linear regression? Why did they chose only one speed? Why did they use only 2 pressures?

Any tire that I've ever used had a certain performance zone that it worked well with. Everyone here has spouted out there preferred tire pressures.

A tire is essentially a spring. It is an air and elastomer spring. Springs have rates of asorption for impact. How can you determine what the optimal rate of the spring is using two pressures?

It is not a great study.

For what its worth my hard tail has been gathering dust. My Hi Fi Pro with 2.25 IRC Mibros performs well in all conditions at low tire pressures. Would it be faster at 20lbs pressure? Nope. Would it perform well at 60 lbs? Nope. The answer is somewhere in between.
post #40 of 52
I think it depends on the rider, the trail, and the bike. 2.4 is big for a trail bike, but there are plenty of larger tires. If the largest was the fastest XC rides would be on 3" tubless tires, but they aren't. Besides what about tread design, and casing type (1ply, 2 ply, etc...) these are pretty important too. This discussion seems like an over simplification.
post #41 of 52
Quote:
Originally Posted by Johnnys Zoo View Post
For what its worth my hard tail has been gathering dust. My Hi Fi Pro with 2.25 IRC Mibros performs well in all conditions at low tire pressures. Would it be faster at 20lbs pressure? Nope. The answer is somewhere in between.
Can you prove that in a peer reviewed and statistically relevant study? Nope. Do you even have one data point? Nope.
post #42 of 52
Quote:
Originally Posted by newfydog View Post
Can you prove that in a peer reviewed and statistically relevant study?
Yeah, because nothing that hasn't been proved in a peer reviewed and statistically relevant study can't be true.
post #43 of 52
Bottom line, as I stated in my original post, is that people really need to test different combinations of tires and pressures to figure out what works best for them under different conditions and trail characteristics. Find out the different combinations that you like best.

I have about 10 different tire types and two different widths that I use, and I change them and the pressures quite often depending on the trail characteristics as well as weather conditions. Having the ability to do this is essentially like having a full set of clubs in your golf bag. Limiting yourself to one tire, pressure, and width is like playing a round of golf with a single club... and unless you're 'Tin Cup Costner' using trusty #7, you're cheating yourself out of optimum performance.
post #44 of 52
Quote:
Originally Posted by billyymc View Post
Yeah, because nothing that hasn't been proved in a peer reviewed and statistically relevant study can't be true.
Easy billy, I was just poking fun and suggesting that in my zoo, whats good for the goose is good for the gander. Read a couple of posts up and you'll see:

"The study is really not scientific. Its not been critically reviewed for one."

I think it is a decent study. You could move in a ton of other equipment, run it 286 time and my gut feeling is you would still find that on rough gravel roads fatter softer tires are faster. Bushwacker gets out and rides, and concurrs.
post #45 of 52
Quote:
Originally Posted by newfydog View Post
Easy billy, I was just poking fun and suggesting that in my zoo, whats good for the goose is good for the gander. Read a couple of posts up and you'll see:

"The study is really not scientific. Its not been critically reviewed for one."

I think it is a decent study. You could move in a ton of other equipment, run it 286 time and my gut feeling is you would still find that on rough gravel roads fatter softer tires are faster. Bushwacker gets out and rides, and concurrs.
Was just bustin your chops Newfy. I don't read most of this stuff, just find it amusing. FWIW, I'm going to let some air out of my tires this weekend and see how it feels.
post #46 of 52

***Hippoopo(critical)thetical Tire Experiment***

Actionoffroad.com

Mowak Tires
A couple guys decided to end the notion that high tire pressure was the fastest tire pressure to use.


The experiment proceded as such; An off road vehicle was obtained for the purposes of this reasearch.

3 sets of tires were obtained; summer tread, all terrain, and snow tires.

It was deemed that 3 obstacle courses were to be run. Brick pavers, gravel, and mud pit.

Tire pressure of 15lbs and 60lbs were chosen.

Efficiency was to be measured with the Unum E. Ammeter.

We ran 103 trials because thats when we ran out of Yeunglings.

As you can clearly see from our data, 18.8 charging amps was the highest figure obtained.

From this data we can logically deduce that ALL OFF ROAD TIRES SHOULD BE RUN AT LOW PRESSURE TO OBTAIN MAXIMUM SPEED.



post #47 of 52
Dude, give it a break. Spend as much time on your bike as designing your posts.
post #48 of 52
Quote:
Originally Posted by newfydog View Post
Only on roads. Once you are on gravel, the curve inverts. Read the article Bushwacker cites. It is dead on.

http://www.bicicletta.co.za/Download...llustrated.pdf

I've been telling friends their tires were too hard for years. This year I'm running 2.5's at about 20 psi on my 29'er and just gliding over stuff.
It's not just true off road. Unless the road surface is billiard table smooth a softer tire with more air volume will also help
there. 650B x 38 Trimelines roll fast and comfortable. Most of my road bikes are 28mm or BIGGER. Sadly tubulars bigger than 25mm are now all but extinct, which is a damn shame if you never tried them.
post #49 of 52
The big sew-ups were pretty nice. I recently saw Del Mondos, the tire of choice for Paris Roubaix for years has one of the lowest measured rolling resistances.

By first race was a time trial, back when we time trialed on regular bikes. I rode with Schwinn LeTour 27 x1 1/4' clinchers and finished second, just behind the state champion. Everyone said I'd kick ass on skinny sew ups, and it was frustrating when I finally got some real racing wheels and didn't go any faster.
post #50 of 52
Thread Starter 
Quote:
Originally Posted by newfydog View Post
Dude, give it a break. Spend as much time on your bike as designing your posts.
I honestly think JZ spend more time on his bike than anyone else here....

but yeah that post was funny. Yeunglings is the best macro brew in america and JZ would be an awesome guide over in West Virginia.
post #51 of 52
"Yeunglings is the best macro brew in america" Nuff said.
post #52 of 52
Thread Starter 
ha so I had to do it, its just sport, but I got 2nd on 2.4 inflated to 20psi in the front and 2.1 inflated to 25 psi in the rear.

ghetto tubeless non UST tires.

http://forums.epicski.com/showthread.php?t=72764

results

http://www.westlibertycycles.com/mom/results.htm

so either I am right or am I pretty good rider, maybe both?

absorbtion in action

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