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PostPosted: Sat Jun 22, 2013 12:09 am 
rBoTM Winner
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For years I have used 100psi for 700x 23c clincher tires but recently I have read this may be too much and that slightly less pressure, 80psi, might actually be faster. Thoughts?

(I weigh 170lbs so the weight per wheel is about 80lbs)


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PostPosted: Sat Jun 22, 2013 12:53 am 
Dirt Disciple
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Location: Stroud
I inflate mine to around 90 PSI for a 700c x 23 this is around the 6-7 bar mark. I used to just gauge it by pushing down on the tyre! :P
James.


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PostPosted: Sat Jun 22, 2013 2:13 am 
r.B.o.T.M. & P.o.T.M. Winner
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Veloflex Masters at 110psi


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PostPosted: Sat Jun 22, 2013 2:56 am 
Old School Grand Master
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Hi Steven,

I just bought a new pump and it appears that my previous one may have been reading a bit off! I have pumped up a pair of 700 x 23c to 120psi (with the new pump) and they are just about right for smooth surfaces, i dread a section of raod nearby where i expect that my teeth (the few i have left) will rattle out!

Richard


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PostPosted: Sat Jun 22, 2013 7:32 am 
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Location: No brakes? Way to commit soldier.
I think I read recently that a slightly softer tyre rolls faster, can't remember where. Something to do with conforming to the shape of the road rather than bouncing around on top of it I think. Might be wrong.


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PostPosted: Sat Jun 22, 2013 4:13 pm 
rBoTM Winner
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Russell, you are exactly right, at least according to the research of one man here in the US. His name is Jan Heine and he publishes a magazine called Bicycle Quarterly. His real world research, actual bikes on real roads, found that there was less rolling resistance from wider tires and less pressure. A synopsis is here

http://www.bikequarterly.com/images/BQTireDrop.pdf


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PostPosted: Sun Jun 23, 2013 2:50 am 
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I pump my 700 x 23c tyres up to 110psi at the back and 100 at the front. I do them about once every 7-10 days and they have usually dropped to about 80psi by then. Running them at 80psi is noticeably softer, but they regularly clunk the rims on the appalling roads around here. On my other commuter I recently swapped to 25c tyres. The extra 2mm doesn't sound much but they protect the rims a lot better and I run them at 100psi at the back and 90psi front. The speed/effort difference wasn't even noticeable but the ride is significantly more comfortable and the rims don't hit at all even if I run over a pothole by mistake.

On my old 27 x 1-1/4" I ran 90 at the back and 80 at the front on what is basically a 32mm wide tyre. Again, I don't think I noticed any significant difference in speed or effort on commuting, but I do know I miss (and yearn for) the silky smooth silent ride they gave.


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PostPosted: Sun Jun 23, 2013 1:34 pm 
Devout Dirtbag
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Location: Bangor - NI
100psi on 700x23 Schwalbe blizzard sports.

Have never tried lower pressures, but interesting theory re' rolling resistance.

N


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PostPosted: Sun Jun 23, 2013 5:03 pm 
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lewisfoto wrote:
Russell, you are exactly right, at least according to the research of one man here in the US. His name is Jan Heine and he publishes a magazine called Bicycle Quarterly. His real world research, actual bikes on real roads, found that there was less rolling resistance from wider tires and less pressure. A synopsis is here

http://www.bikequarterly.com/images/BQTireDrop.pdf

That's not what the article says. His words are: Our tests of tire resistance have shown that tire resistance is high at very low pressures. As pressures increase, tires roll faster, but the performance levels off at a certain pressure. Beyond this point, higher inflation brings only negligible performance improvements.

It doesn't say that a wider tyre with less pressure made less rolling resistance.


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PostPosted: Sun Jun 23, 2013 7:40 pm 
rBoTM Winner
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Apologies for that I posted the link to give an example without being specific. I subscribe to Bicycle Quarterly and there is a loooooong article on tire pressure and tire width. The conclusion that they came to over the course of many teats over many different surfaces is that a narrow high pressure tire is faster on a perfectly smooth surface like a velodrome, but that on roads the high pressure tire was equal on a mostly smooth road and slower on a rough road.


Last edited by lewisfoto on Sun Jun 23, 2013 8:02 pm, edited 1 time in total.

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