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Author Topic:   TIRE SIZE = RPMS
dirtTurd
Dirt Maniac

Total posts: 115
posted October 26, 2005 09:15 AM  
I RUN UMP TIRE 27.5 HOW MUCH WILL RPMS CHANGE IF I GO TO 26.5.

THANKS

Fastride 38
Dirt Maniac

Total posts: 125
posted October 26, 2005 09:25 AM  
I wouldn't think enough to really notice....There is a rpm to tire size calculation in the tool box area. You might try that and see. Never mind it wants a MPH. Unless you know just how fast you are going...LOL

[This message has been edited by Fastride 38 (edited October 26, 2005).]

[This message has been edited by Fastride 38 (edited October 26, 2005).]

wfoondirt
Dirt Forum Champ
Total posts: 505
posted October 26, 2005 11:12 AM  
Rpm is inversely proportional to tire size so:

new rpm = (old tire rollout/new tire roll out) * old rpm

ie. (89/84)*7500 = 7946

This stands true from my exprience also. I usually saw a 300-500 rpm increase going from a 27.5 to a 26.5.

dirtTurd
Dirt Maniac

Total posts: 115
posted October 26, 2005 01:09 PM  
THANKS GUYS...WONDER THE EFFECTS ON HANDLING WILL IT BE THE SAME??

wfoondirt
Dirt Forum Champ
Total posts: 505
posted October 26, 2005 01:27 PM  
Your going to give up a little contact patch and it may lower the cg a little. But otherwise there's not any substantial change.

Some people claim the 26.5 have a flatter cross section than the 27.5 but I just consider that voodoo.

[This message has been edited by wfoondirt (edited October 26, 2005).]

fastow
Dirt Maniac

Total posts: 168
posted October 26, 2005 08:32 PM  
What about the difference in unsprung rotating wieght. I would think that would be worth a mention anyway.

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