Cranky's Corner

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Tire pressure

Inspired by this post over at PedalWORKS I decided to do some experimenting with my own tire pressures.

Previously in my 25mm tires I had been running 90psi in the rear and 85psi in the front. Now this clearly goes against the tires minimum recommend pressure of 102psi but it is comfortable and I have never had any ill effects doing so. Interestingly enough the pressure calculator recommends 82psi in the rear and 62psi in the front for my weight on the bike. 62psi seems way too low for me so for the first test I inflated the rear to 82 psi and the front to about 75 as that was as low as I was comfortable going.

To do my testing I picked a loop around my town that could provide me varied testing surfaces (smooth, bumpy, flat, climbs). With the tires inflated to 82r/75f I set out on my course. To be honest I didn’t notice all that much comfort from my usual pressure nor did I feel like I was at a disadvantage either with lower air in the tires – meaning it didn’t seem to give me any additional rolling resistance.

With that subjective test complete I decided to go the opposite way and I pumped the rear tire up to 102psi (the recommended minimum printed on the tire) and put he front to about 95psi and set off on the same course. The bike certainly felt fast but within 20 minutes my lower back was sore and that became tiring so all speed went out the window. So I stopped burped some air out of the tires a couple of times front and rear and continued to do my loops. I was completely going on feel now and what I ended up with I really liked. It still seemed fast but not so harsh to aggravate my lower back. So when I got home I checked the pressure in each tire and the rear was at 90psi exactly and the front was around 80psi. Not very far off from my original numbers I started with.

But of course I was not done yet… that 62psi recommended pressure was still in the back of my mind. I still couldn’t bring myself to go that low but I dropped the front tire al the way down to 70psi now and left the back at 90 since that does seem to be my sweet spot and set off on my loop once again. Ok that sucked… it was very comfortable up front but honestly it felt like I was peddling through mud. It was just 5psi lower than the first test I did but there was definitely a difference.The tire visibly didn’t seem like it was compressing a lot but I certainly felt it at the pedals, most notably on the climbs. Perhaps because I’m putting more weight on the front of the bike when I’m climbing? I don’t know but I probably won’t be running that pressure again.

In conclusion this just shows you can’t go by a chart and pick pressures, but you really need to go out and do some experimenting. It’s very easy to inflated your tires to 100psi and then over the course of the ride keep tweaking the pressures until it feels good. And it seems, at least for me, there is about a 5psi margin of error for feeling good and feeling like you are riding on flats. With all that said for dry riding I will be staying with 90psi in the rear and go closer to 80psi in the front, and in the wet I’ll drop the pressures by 5psi to stay in my sweet spots.

3 Comments

  1. I’ve read that post over at PEDAL WORKS before and I never even bothered testing it… I was worried more about pinch flats but even ignoring that, I won’t ride below 95 front and 100 back for 24’s… They swear up and down the science says there’s no difference but anyone who rides fast knows there is. 60-80 pounds for a skinny tire is just silly.

    Just my two pennies.

    • I agree to an extent as a lot has to do with tire composition and rider weight. i.e. a light rider with a stiff tire will need less pressure than a heavier rider with more supple tires. I believe my Mavic’s to have a softer sidewall (hence the over compensating min pressure) but at my lightish weight (152) 100psi is still way too much. It would probably be fine if I was riding 1hr crits but not so much for long endurance rides. I also found the lower pressures better for cornering, more surface area gripping the road.

      • Ah, but I ride Specialized Turbo Pro tires… They have a tread for cornering that works excellently. You can have the better roll with excellent cornering. Now, that said I used to be a max pressure kind of guy. I knocked the 125 down to 100 psi and found that to be my fair compromise. Any lower and I can feel it – what the science says on a steel roller is different from the road. I also agree that the tire type matters but I definitely have to defer to feel.

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