Bike Forums

Bike Forums (https://www.bikeforums.net/forum.php)
-   Fatbikes (https://www.bikeforums.net/forumdisplay.php?f=336)
-   -   can i put 30 pounds of air in fat bike tires (https://www.bikeforums.net/showthread.php?t=1158311)

windhchaser 10-18-18 06:03 PM

can i put 30 pounds of air in fat bike tires
 
i think it says 15 pounds or some low number that cant be correct

HerrKaLeun 10-18-18 08:35 PM

typically limited to 20 psi. riding pressure is only 3-10 psi anyway.
30 psi would be very hard.
30 psi is for MTB with 2.x tires, if even that.

DeadGrandpa 10-18-18 08:49 PM

I have a 29+ bike with 3 inch wide tires. 30 pounds gives you a bouncy ride and I don't recommend it. At 14 pounds pressure I get grip in the corners of both singletrack and forest service roads, steep inclines, whatever you can roll over from washboard to roots, chunk or whatever. 13 pounds isn't quite enough. 16 is too much.

5teve 10-19-18 09:22 AM

Fat bike tires/rims are designed for much lower pressure than that. I've never run more than 10-11psi in mine. I think 30psi would very possibly damage your rims or tires.

GrainBrain 10-19-18 09:24 AM

Go ride your bike windy!

At about 15psi.

Post ride pictures!

buffalo4life 10-23-18 06:06 PM

I rode my fatbike on the MUP today and took the tires up to about 12 psi for making some speed!

Shimagnolo 10-23-18 06:19 PM

The limitation is probably to prevent damaging the rims.
The larger the tire, the greater the outward force on the rim, at the same pressure.

I was once running some 2" tires that advertised a 65psi max on the sidewall.
After breaking the second perfectly good Mavic rim, I realized that was simply too much for the rims, and settled on lower pressures.

Lengthy discussion of hoop stress here: https://www.velonews.com/2017/03/bik...buildup_433214

unterhausen 10-23-18 07:05 PM

forget where, probably on the FB FB group, I recently saw a blown out tire and destroyed rim at some pressure lower than 30psi. That's what I like to run in my gravel bike 38mm tires, so yeah, it's too high for a fat bike tire.

rm -rf 10-23-18 08:09 PM

This is windhchaser's "blog", there's a ton of separate threads. Most of them in foo.

30 psi on a 5 inch tire is like 150 psi in a 25 mm road bike tire. That's extremely overinflated, enough to damage the tire and rim. Not to mention that it's terrible for comfort and handling.
See this article on "hoop stress", needed air pressure is proportional to the tire width. (like Shimagnolo posted above.)

prj71 10-24-18 09:05 AM

Depends on what the tire allows which is stated on the side of the tire. That varies with every manufacture and the type of tire produced.

I used my Specialized Fat Bike for a gravel race once and aired up the tires to 25 psi, which is the max stated on the sidewall.

Hypno Toad 10-25-18 07:16 AM


Originally Posted by windhchaser (Post 20623224)
i think it says 15 pounds or some low number that cant be correct

Why do you want 30 psi?

This thread I started a couple years ago might help understand fatbike tire pressures: https://www.bikeforums.net/fatbikes/...ned-photo.html

I race my drop-bar Pugsley on gravel grinders, and I don't go above 15 psi (I was the second fastest fatbike of 30 registered for the 2018 Filthy 50):

https://cimg1.ibsrv.net/gimg/bikefor...1089d84505.jpg
Photo credit - https://markmanoutdoorphotography.com/

footnote/details: tires are Panaracer Fat-B-Nimble 26 x 4.0, rider is 170 lbs (likely 200+ lbs in this pic with all the water/ice/snow/limestone dust).

baj2 10-31-18 10:46 AM


Originally Posted by windhchaser (Post 20623224)
i think it says 15 pounds or some low number that cant be correct

What size tire? I have two sets of 4.8" x 26", one is 15psi max, the other is 20 psi max. Either gets to be a rough mtb trail ride above 8-9psi. I've gone below 2psi for deep snow riding.

Speedway2 11-08-18 06:18 AM

I've mainly owned bikes with tires recommending 100-120psi.

When I (recently) bought my first fat tire bike (4"x26") the recommended max pressure on the tire was 20psi. I scratched my head and thought it must have been a mistake because at 20psi the tire felt "soft".

After searching the internet for answers (and reading this thread) I'm keeping my tires under 20.....

MarcusT 11-09-18 12:39 AM


Originally Posted by windhchaser (Post 20623224)
i think it says 15 pounds or some low number that cant be correct

My tires give 30 psi as the max, one day the trail I was riding had been washed out and I had to take a very long detour on paved road. Not sure if I put in 30 psi, but it was close, because it was the end of a long ride and I wanted to get home a fast as possible. No problems, no damage, it was a little bouncy though.

daoswald 11-09-18 02:04 AM


Originally Posted by windhchaser (Post 20623224)
i think it says 15 pounds or some low number that cant be correct

You would need tires with a capacity of 371 liters to put 30 pounds worth of air in them.

lmtada 11-10-18 06:54 PM

12 lbs in Mine.

baj2 11-11-18 01:57 PM


Originally Posted by daoswald (Post 20655077)
You would need tires with a capacity of 371 liters to put 30 pounds worth of air in them.

PSI is pounds/square inch = force density, not a weight. If it was a weight few would be able to lift their road bikes with two 100+lb tires.

The best way I've found to think about tire pressure is this. The air pressure in your tires is supporting the weight of you, your bike, and your gear. The tire will deform on the bottom based on the pressure in the tire and the weight it's supporting. If you are 180lbs, have a 35lb fat bike and 10 lbs of clothing and gear, that's 225lbs. Roughly speaking, if your tires have 10psi in them they will deform to create 22.5 inch^2 of ground contact to support that weight. If you run 5psi the tires will deform to create 45 inch^2 of ground contact.

If you are riding on loose or new snow, the lower the pressure you can run in your tires, likely the better your bike will perform. It varies with snow conditions of course. The pressure in your tires (PSI) roughly equates to how much force your tires are putting on the snow/inch^2. The example above is basically me when I ride in the winter, so at 2psi my 4.8" tires are getting flat enough on the bottom to create a total of ~112.5 inch^2. And yes, the tires look ridiculous and it is a heck of a lot of work to pedal, but it's pretty impressive when you are grinding your way through 10" of fresh snow.


All times are GMT -6. The time now is 04:37 AM.


Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.