Over-inflate by a few psi?



Reference to car tires and recommended pressures is a good one, but of course the manfacturers have a much better idea of what the "vehicle" weighs than they we do for bikes. And rather than provide just one recommended pressure, some cars specify a range of pressures based on load and speed. EG, the New Beetle turbo had a set of pressures on the placard for full/light loads on the and under/over 100 mph speeds. The rear pressures varied quite a bit with light to full load, ie, from 28 to 38 psi.

For bikes, I've seen a chart of weight vs recommend pressure vs tire width, maybe from Conti? IIRC, on 23mm tires, the 120 psi max is recommended for riders over 180 lbs. My GP4000s box says 110 psi is the recommended pressure for 23mm. I've read that 25 mm tires will have lower rolling resistance for riders over 180 lbs, even while running 10-20 psi less, but have never tried them personally. I'm 190 lbs currently, and run 100 psi front, 110 rear. I like the increased grip and "roadholding" feel on fast descents that the reduced pressure gives, as well as the reduction in cuts/punctures.
 
Quote:Originally Posted by jojoma .

A mechanic once told me that about 4 psi are lost when removing the pump head. Is this true? My Michelin Pro3 race have a max of 120psi. I usually go to about 118 and call it quits. To get to 120psi, should I go to 124psi??/img/vbsmilies/smilies/confused.gif
 
The newest research uses surfaces that is realistic, more like tarmac, than the steel rollers they used to use. I'm speaking from experiance too- over 35 years and I've ridden with and worked with national team coaches, Team mechanics wtih Giro experince, national champions and have had state/district champions ask me to help ge tready for olympic trials. I now weigh well over 200 lbs ( Ihad to spend 2 summers and a apirng onmy back and my wife bakes) and still inflate my tires so there is a little "give" mayb einflate "hrd" or full pressure on a smooth tracxk
 
I weigh 120lb and inflate my road (23mm) tires to 95-100psi for most occasions (including races). I raced once with tires inflated to 120psi and the course had a technical decent, and I absolutely hated it. I could feel the difference in "grippiness" and never felt totally confident on that decent at race pace.
 
Calico, agree that over-inflation will work against roadholding and stable steering on decents, particularly if you have less-than-smooth road surfaces to negotiate. There are still a few riders I know who insist on going to max pressure and over, thinking that they are saving watts when all they are doing is reducing the roadholding and making technical descents more hazardous.

At 120lbs, believe you could go with 85-90 psi in front on 23s without any significant penalty in rolling resistance or problems with pinch flats. You might like the handling feel even better at those lower pressures.