MTB tire pressure calculators?

[Quattro Pete]

I realize this is one of those "play by ear" or "play by butt" type of questions to a large extent, but I just need a general ballpark idea. I've seen calculators that spit out results based on rider's weight, wheel size, tire width, terrain, etc. Here is one example:

http://mtb.ubiqyou.com/

However, my bike's tires are actually narrower than the options given here. I've got 26x1.75 in the back and 26x1.5 tire in the front, not a very aggressive tread pattern. I weigh about 150 lbs and ride a mix of paved and unpaved but fairly smooth trails.

Max PSI listed on the tires is 65, and I typically just inflate them to that and when they drop noticeably, I pump them up again. Alas, 65 is probably too much here. But on the other hand, I don't want to be too low either. Any suggestions?

 

[IndyIan]

Get bigger tires?

I guess you must be on smooth terrain most of the time, so 55-65psi with those tires sounds reasonable to maximize roll.
With my XC bike 100mm fork hardtail, I run 35-40psi rear, and 30-35 front with 2.1 tires. My freeride 130mm fork, hardtail, 2.5 gets about 25-30 front and 30-35psi rear.
The low end pressure is for smooth offroad and high end is for rocky trails to avoid pinch flats.
If I go for a road/gravel road ride I would go up another 5 psi.

 

[AZjeff]

Max pressure with narrow, mild tread tires on any kind of dirt or gravel is asking to take soil samples. Somewhere in your max to min variation you should be able to notice a sweet spot where it rides nice and rolls well. Measure pressure there and keep it at that. More work than your present method, might not be worth it to you. Curious about your different size tires, can't remember a bike being spec'd like that. You're not heavy enough to need a larger rear tire.

 

[Quattro Pete]

Originally Posted By: AZjeff
Curious about your different size tires, can't remember a bike being spec'd like that. You're not heavy enough to need a larger rear tire.

IIRC, this bike (cheap Schwinn Sidewinder) originally came with 2" or 2.1" tires, but because I'm doing more pavement riding than off pavement, I decided to go for something narrower. The current setup is only temporary until that rear tire wears out, and then I'll put on a matching 1.5" tire on there as well.

The 1.5" tire is this one: http://amzn.com/B002KVORD8

Now that I'm reading the description, it says 50 PSI max. I'm going to have to take another look at the actual tire to see what it says on the sidewall, but likely even 50 is too much in my case.

 

[Surestick]

What are you trying to accomplish? More grip? more comfort? Better rolling?

My go-to setting for off-road is to get the pressure to the point the side knobs are just barely touching. It's generally a good starting point.

If you're riding on the road give that a try then add five psi.

 

[Stregone]

Keep going lower until you notice too much rolling resistance (totally up to you how much comfort vs rolling resistance you want), you can feel the tire getting 'squirmy', or you start getting pinch flats.