Tire Pressure Settings.

Strouble

Strouble

PR Addict
Been a while since I have been on a bike and was riding mostly woods. Use to keep my psi around 12-13. What is a good psi for motocross with a track in good shape?
 
Thanks man. I was thinking about starting at 14 and working from there. Moto is a little different from woods. Can't wait to shred! Brap!
 
There's some cool theories behind tire pressure.

Some put 17-20lbs of air in front and back during mud races. (Windham) Others run low air pressure.

On a normal day I run 13 in the front, 12 in the back. But it's really whatever you feel is right for you?
 
it is best to calibrate tire pressure based on rim "clean" vs. PSI... this is the most accurate method of obtaining the best traction levels. I was always taught to look for 4-5 of rim clean of which will vary from front to back depending on skill level and riding style.
 
YZ125 said:
it is best to calibrate tire pressure based on rim "clean" vs. PSI... this is the most accurate method of obtaining the best traction levels. I was always taught to look for 4-5mm of rim clean of which will vary from front to back depending on skill level and riding style.
Click to expand...

I don't understand "clean?" Explain please...
 
MXCrusader617 said:
I don't understand "clean?" Explain please...
Click to expand...


Rim clean is a phrase that refers to the sidewalls' tendency to roll over the edge of the rim. A properly inflated tire will flex around the sidewalls and actually scrape the very top of the rim edge clean. If you don't see a shiny strip of polished aluminum around the top edge of the rim, you have too much air pressure.
 
More good info: Tire pressure is an extremely important yet often overlooked chassis setup as 90% of riders do not set their motorcycle tire pressures properly! The majority of riders just set their tire pressures somewhere between 12-15 psi, and never really give it much thought. Too much motorcycle tire pressure will tend to make the suspension feel stiff, and too little will make the bike wallow and push.

There is only one method to deciding the proper motorcycle tire pressure and it is called RIM CLEAN. There must be up to a 4-5mm maximum clean strip on the outside of the rim where it contacts the tire. During use the tire rolls over the rim somewhat, keeping this part of the rim clean. ALL off-road motorcycle tires are designed to work this way, front and rear. “D” shaped rims will require less rim clean for obvious reasons.

The motorcycle tire pressure is adjusted so that the proper amount of rim clean is visible. The tire pressure will differ dramatically from tire to tire, tube to tube, bike to bike, rider to rider, and track to track. A soft carcass tire with a stock tube may require 16 psi in order to have the proper rim clean. A hard carcass tire with a heavy duty tube, may only require 6psi.

It is very easy to run the wrong tire pressure, but most people don’t know how to calibrate it. If you have the proper amount of rim clean, and your buddy has the exact same bike/tires/tubes but he has no rim clean, you theoretically have say 10% MORE TRACTION! Tire pressure (psi) is only a number, and that number is used to calibrate the rim clean.
 
YZ125 said:

Rim clean is a phrase that refers to the sidewalls' tendency to roll over the edge of the rim. A properly inflated tire will flex around the sidewalls and actually scrape the very top of the rim edge clean. If you don't see a shiny strip of polished aluminum around the top edge of the rim, you have too much air pressure.
Click to expand...



http://www.google.com/url?sa=t&rct=...sQMNoIzMLV0PqoIygeeR2Dg&bvm=bv.62922401,d.aWc

Here is a link to the MXA Article that YZ 125 is quoting verbatim.
 
Wow! Looks like some testing will be done. That's pretty interesting. Surprised I have never heard of run clean before. Thank you!
 
Ok, let me see if I can complicate this further... :eek:
Rim clean is only a good visual to verify inflation if, and only if, you understand the tire construction, compound hardness, soil makeup (% of clay, silt and sand) compaction levels and moisture content of said soil. Rim clean is in a nut shell, is showing how much the sidewall is flexing. As you can imagine, all of the above factor into this equation + the infinite variables on rider ability and ever changing track conditions.
I spent 3 month, one afternoon, doing tire testing back in the day trying to simplify this process. Higher clay content (most of Ohio and the Midwest for that matter) most people will get better "feel" from a soft compound tire. Soft compounds allow the knobs to flex, grabbing the soil more then ripping through it. Problem is, not all tire companies use the same compound on the sidewall as they do the tread area (again, matter of fact, few do). We will assume they do...
So, soft compounds will flex more, allowing for more shoulder roll, resulting in more rim clean. Reducing the inflation for this tire will not necessarily equal more or less grip but will dramatically effect rim clean. Once you have all those factors determined, then you can determine inflation. Until they go out and disk and water...then, start all over again.
Or, just set it at 13 and forget it.

One other thing. I completely disagree with the lower inflation in sand and mud. I ALWAYS went higher. As much as 20 or 22. In those conditions you do not want the tire flexing. You are trying to dig through and not grip. It would be like trying to shovel snow with a handle made of Jell-O.

Just my 2 cents
 
I check tire pressure once in the morning and run 12 or 13lbs depending on dry or wet conditions. Don't forget to check your fork pressure on the stand. I'm at 34lbs. Check and forget it. haha
 
The only thing you check is whether the mountains on your coors light is blue or not.
Get real duuude
 
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