merlinextraligh

^ IMHO those pressures are way higher than necessary. With 28mm tires I’d bet you’d have no issues at 100 psi.

you can obsess about this way too much, particularly if you slavishly follow on line calculators.

we often ride without having checked pressure for several days, which results in pressures we’ll below what was originally spec’d. Point being you don’t have to hit a precise number.

All the calculators, all our posts on here are just data pooints to consider.

that said, the easiest way to do this is to ride the lowest pressure that doesn’t 1) result in tires squirming, or 2) pinch flats.

If either 1 0r 2 is happening you might need to raise your pressure. If your ride is uncomfortably Harsh you might want to lower it. Other wise, just ride.

Skytour

As turns out, likely not too far off from those values. We had lower pressures than thought. When pumping to such high pressures, there is always that hiss as the pump chuck is removed from the valve stem. That releases 10 psi. So where we thought we were running at 120 front and 130 rear, the tires actually have 110 front and 120 rear. Will monitor 24 hr air loss. We often ride two days before a refill and be interesting to see actual pressures on the 2nd day. May unknowingly already be in the 100-110 psi range.

TobyGadd

Wait, I didn't think it was possible to over-obsess about ANYTHING bike-related.

This is spot-on advice.

Different road conditions, rim widths, tire models, team weights, riding styles, etc. make it nearly impossible to blindly follow online calculators or random advice on the internet. Put in some air, and then ride up and down your street. If the pressure is too low, the tires will squirm, and the bike will ride like a wet noodle--so add 2-5 pounds and try again. Too much air, and you'll unnecessarily feel every little bump. The tricky part may be getting the ideal pressure to avoid pinch flats if you aren't getting much squirm and you like riding with lower pressure. But if do you get pinch flats, simply increase the pressure 2-5 pounds at a time until you don't get more. Just be really careful about pushing the maximum pressure on the sidewall (especially if you have heat-inducing rim brakes!) or you may end up with an "explosive decompression"--which could make for a very bad day. As you gain more confidence with the feel and performance of your bike, you can always tweak your pressure to fine-tune your experience.

TobyGadd

Depending on how you read tire pressure, be careful about calculating how much air is lost due to "hissing" when attaching or detaching a pump that has a hose. I've found that removing a pump actually releases far less air from the tire than it seems to, since most of the hissing comes from air in the pressurized hose, not from the tire. Likewise, a lot of pressure can be lost into the hose when the pump is re-attached--making the pressure a fair bit lower on the pump's gauge that it actually was before the pump was attached.

In short, if your pump has a hose, the best way to verify pressure is to use a low-volume pressure gauge that doesn't bleed much air when it's attached or removed.

antmaster5000

What do you guys think for 26" tires? I am 150lbs and stoker is 140. We are riding a pretty heavy touring tandem w/ couplers + frame bags (estimated like 40-50lbs?).

For the last year we've been running our 26x1.9 tires at ~65psi and it has been fine. This is also the max psi on the tires. Over the past few weeks we have had the WORST luck with flats. Ran over some glass that has contributed to at least 5 different flats (I keep picking out what I find) as well as 3 pinch flats. I'm fairly sure that I am installing the tubes correctly- I've been an avid cyclist for 10+ years and have probably installed hundreds of tubes and have never experienced this many pinch flats in a row.

Do you think it is due to low PSI? Tire pressure calculators put us at around 60 PSI, but honestly I am just tired of changing flats. I have them up to 80 right now (which also makes me concerned about going above the max) and they lasted fine on a 40 mile ride. I guess I am trying to figure out if this is a string of bad luck + user installation error or if it is a psi issue.

TobyGadd

Pinch flats are pretty much only caused by underinflation. The exception would be if you are really careless about riding over sharp edges (which is unlikely for someone with your experience). Puncture flats have nothing to do with pressure though, so I wouldn't let their frequency determine your pressure.

Sounds like you've already answered your own question though. 80 pounds is probably a good pressure for your weight, riding style, and surface conditions. If you never get a pinch flat with that pressure, but the ride is too harsh, you could try going to 75 or lower.

RoulezTandem

Our custom welded steel etandem weighs 100# pounds with bafang middrive and battery and trip gear.
Grosses 400# with water and riders.

Roughly 65 psi on 26x2 Schwalbe Marathons and flat resistant inserts on steel rims for strength.

Strictly rail trails typically 8mph to max 15 mph.
One catastrophic blowout where tyre centre shredded, no clear reason. Otherwise they handle bedrock and large gravel just fine after forty 10 to 40 mile trail rides in many suburban and wild places from Tennessee to Newfoundland.

Just tried the various calculators listed in this thread: four sites wildly different results. 26 to 42 to 69#. Will stick to 65 rear 60 front.

jmitchelltfo

Sram has a great app to get you in the ballpark for tire pressure. Just enter the pertinent info and you can adjust the pressure based on your observations.

There can be some substantial differences based on rim width, hooked/hookless, tire casing, and tubed/tubeless.


SRAM | AXS