9/16/15 3:28 PM

Last year I moved from 23 mm Vred TriComps to 25 mm Michelin Pro Optimum tires. I'm still playing around with pressures, with maybe a little more emphasis on comfort rather than maximum performance.

I found some interesting recommendations in the Bicycle Quaterly archive.
See: http://www.bikequarterly.com/images/TireDrop.pdf

My bike and I together weigh almost exactly 200 lbs. I also was able to verify their suggested weight distribution figures of 40% front and 60% rear for a road bike. Using a bathroom scale, I'm 80 lbs front and 120 lbs rear.

Per their chart for a 25 mm tire, I should be running 70 psi front and 108 psi rear. I was astonished by the 38 psi difference.

I also note that the Michelin tires are rated at 73 psi min and 109 psi max. Dunno if I want to be operating at both extremes.

Have any of you used such a large differential?

9/16/15 4:07 PM

No, I've never used such a large difference front/rear. For my road bike with the Schwalbe 28s I normally use, I use 65 front and 75 rear. My bike and I weigh about 160...

9/17/15 5:41 AM

...I run 70-72 front and 80-82 rear, at my weight of ~175# (~195# total with me, clothing and bike).

9/17/15 7:16 AM

23mm tires right now,

85/95 PSI works for me, 167# for me and 16# for the bike. My roads won't let me go any lower.

9/17/15 9:46 AM

Brian like the cush at those pressures. ;)

I am about 215 lb. now.

Over a few setups here, mostly wide rims. I run 23fr/25bk GP4KS w/latex tubes 85/87lb. Still have wheels with both 23s with latex tubes 85/95lb. A tubeless road 23C setup I run the same [barely 23mm on wide rims] and they ride just as nice. All Season 28s Conti x2 bikes. On the tandem get 95/105, which surprises me works with our weight. The All seasons on the Paramount 80/85.

The road mode of the new green machine has 27mm Paves I run @ 85/90.

Wide rims make a 23=24.8 a 25=27.8.
Certain tires feel better @ a little more pressure to me. Vitts generally and the Fusion II tubeless 23s.

Yada

9/17/15 12:22 PM

I have always wondered if those pressure graphs should be a linear straight line or if they should start to curve towards the two ends.

I run Mich. Pro 25c on my single. 170# plus 20# for a rolling weight of 190#. Typically I run 95psi front and rear. Probably a hold over from the thinner tire days but am happy with those pressures. Feel pretty comfortable and while I could probably go lower with the front tire for me the comfort comes from the rear tire as the front floats over stuff a bit more.

9/17/15 12:43 PM

I also run 95 front and rear with Schwalbe 25s. I weigh about 185, don't know what my bike weighs. At my age (now Medicare eligible!) one number is easier to remember.

9/17/15 12:44 PM

The Michelin casing for 25C is more like 28-9mm. My old 25C Axial Pros on Pacenti SL23 rims are 29mm after some swelling. I still have 3 of those NOS laying about.
Not the best rolling tires though...

All I would say is you will get a better ride and less cuts if you back it down. Dare i say less incursions of flints and glass into the tire/tube [read:flats]

9/17/15 2:58 PM

After many years of 23mm (true measure) tires at 110#, the last few I have gone to Michelin 25s -- that measure out to about 28mm wide. I also now use much lower pressures, as suggested by this calculator that supposedly calculates pressure for each tire for a 15% drop in tire height. At 190# for me and bike, I run about 70 F/90 R. Much nicer ride and no pinch flats so far. As best I can tell, no change in rolling resistance either.

http://www.biketinker.com/tire-pressure-calculator

[sorry, just tried the calculator and it does not work the way it did the last time I used it. Was based on that same Bicycle Quarterly story....]]

I am sure I would like the new tubeless tires too, if I could ever get around to the doing the effort to change.

Last edited by BobB on 9/17/15 3:09 PM; edited 1 time in total

9/17/15 3:08 PM

"I am sure I would like the new tubeless tires too, if I could ever get around to the doing the effort to change."

I had the DA tubeless wheels for 3 seasons using with tube. Just was not paying 100+ a tire.

But I got a used set for 40.00 and liked them in a major way. Now I replaced those Hutch Atoms for new Fusion III for 107.00 pair shipped. Read what you will into that, but I think if you had some extra coin and felt like treating yourself.. Or fending off that new bike. ;) I do not see how one would not be pleased based on what I am experiencing for two seasons now.

But I may feel differently after a big enough cut to paint me and the bike with goo, And go through the cleaning and tubing, then the cleaning and cleaning when I got it all home...

Probably going to get some Secteur 28C tubeless at some point, but reading the ride quality is not quite there. But that could mean they may wind up more durable too...
But I have 3 27mm Pave CGs to go through for off season use still...

9/18/15 2:23 PM

I'm riding Bontrager R4 320's. I weigh low 190's alone, so my bike is carrying about 210-215 pounds when loaded with me, seat pack and a bottle.
The tires are 700x25 and I run 80 in the front and 85 in the rear. No pinch flats all year, have not noticed I work any harder keeping up or on the front during group rides.
IMO everyone should be on 700x25 tires with about 80-90 psi.

9/19/15 8:04 PM

I agree that a very small f/r differential best balances the risk f/r of pinch-flatting.

I run only a couple of pounds less on 25's here, 79/82psi or so, and at only 140#, but the foothills roads here have "features" and small rocks that can't be seen while in a paceline.

I do like the way lower pressures increase tread life and maintain grip when cornering over un-seen gravel. The smooth ride is just added gravy. I don't feel that lower pressures slow me down, and actually find myself riding past others as road conditions deteriorate.