Another newbie: Gearing question


Larger diameter tire like adding teeth to the rear sprocket??

You have it backwards... It's the other way around..

Consider the extremes: Install a rear tire the diameter of a roller skate wheel (assume 2-inches.. It will have to spin really fast just to cover a foot (realistically impossible since the rear sprocket would be touching the ground, lets ignore that).. That's Low gearing!!! Top of fifth should get you 6.11mph . Now imagine that you install a tire with a Diameter of 10 feet. Each single rotation of the tire equals 34.4 feet traveled per rotation. Ignoring that it'd never fit in the swingarm, your top speed in the top of fifth gear is 341.95mph.

Basically, Larger diameter rear tire equals gearing up, since the distance traveled per rotation is higher.

If you want to gear down, using the thin rear sidewall technique, get a 110/80-18 or a 100/80-18 rear tire. Translated it means that the sidewall is 80% as tall as the tire is wide No sidewall would be something like a 100/0-18 (The knobs would be right on the rim.). a 5.10-18 tire is very close to a 120/100-18 tire when measured. :lol:



Yeah , I am a little backwards sometimes :applause:

Will a 10 foot diameter fit in my swingarm :banghead:

Original Post:

"On order is Big Gun Quiet Series full exhaust, Dynojet Intake Kit, Baja Kit Smog Removal, K&N Filter, front/rear Trakmaster 760 Tires and a 13T titanium front sprocket from Sidewinder."

Thanks all for info.

Parts all here, install manana.

The overiding opinion against 13T front has not swayed my decision, gonna find out.

Mickey XR650L,

You will like the 13-tooth in tight trails.

Stock 15/45 at 6500 rpm is about 100.2mph in fifth gear

With a 13-tooth rear (13/45) 6500rpm in fifth will give you 86.84 mph.

I've ridden an XR600 with a 13-tooth front sprocket. The trranny felt like it had motocross ratios. Very nice on the track, yet still faster than any motorcrosser at 7500rpm in fifth.

..and if you don't like it, you can always switch it back. :banghead:

Installed mods and bike runs great, sounds great.

More power everywhere much smoother delivery with a pretty good kick

thru top revs (no tach, I guess in the 4,000 to 5,500rpm's)

Idle without smog stuff much lower and bike is running noticeably cooler.

LotsofBikes you are right; The 13t front is low, but I LIKE IT! 5th gear power is very cool. :applause:

Not offroad yet but looking forward to time off in October.

New knobbies on street makes for carefull riding; no high speed runs as of yet but am sure 85mph is reasonable.

Overall recomend the mods installed to anyone.:banghead:


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