Effects of gearing on geometry

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robfromga
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Effects of gearing on geometry

Post by robfromga »

Coming for a roadbike/trackbike background, small changes in gearing make huge changes in performance. Just the same on a dirtbike. But I havent found any info on the gearing/geometry relationship.

As you bring the rear wheel in, say with a larger rear sprocket, you shorten the wheelbase. Allowing the bike to wheelie easier, but also turn in better. Also smaller sprockets, with a given chain length make the wheelbas longer, adding stability, but making the bike harder to turn?

One would be good for wide ass open dunes, the other for tight 1st gear singletrack. Also does anyone mess with the length of the fork tubes in the triples? A mm or 2 of raised height makes massive differences in the trackbike world, how about on the 500?

Ive got some really tight trails near my house and have been fooling the gear combo so that Im not constantly on the clutch. Im not a fan of the 13t sprocket. I think its too small and too tight for a motor with that much snap. Ive run a 14 with a 49,51 and I just got a 53 to try for today. All those changes got me thinking, with the chain Im running(116 links i think?) it pulls the wheel in pretty dam close, shortening the wheelbase and that would make it turn in better.

Thoughts? Sure I could run a 15x49 and cut the chain, but thats the easy way :roll: Does any of this tweak the big bikes turning?
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2strokeforever
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Post by 2strokeforever »

im no expert but i know it changes the preload/? even when the axle is in the same spot...
but i wouldnt be able to notice the diffrence
the 450 will have less power and will be harder to start, and will be heavier, but to make up for it it will require more maintenance.
4stroke=dead fish
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NightBiker07
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Post by NightBiker07 »

yes, it will change the things you mentioned. but unless you are a pro rider tearing it up on a MX track, you will never tell the difference. dirt bikes bounce around so much anyways that the changes wont seem like such a huge impact, where a streetbike is almost always on smooth surfaces where you could feel the effects of such small changes.
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Roostius_Maximus
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Post by Roostius_Maximus »

I drop the fork tube 6mm from the top of the tube nut on the gen3, on the 87-88 bikes 4mm below the cap
the gen 4 we run at the tube nut, makes it better wfo
We try to run a smaller sprocket set on the older bikes, non-oring chain and an aluminum rear sprocket.
On the 87-88 bikes you can really make that bike a turd in the bush with the for tubes up, 12mm thru the tripple works good, gets the bleeder tight to the handlebar
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seanmx57
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Post by seanmx57 »

When I'm running at southwick or a sandy practice track I run the rear wheel as far back as I can. Having different chains helps quite a bit for playing with things as you know.

TIght riding, MX or ST I like to keep the rear wheel as far forward as I can, turns better. If there is money on the line I get more picky about it, but for messing around it gets to be a bit of a waste.

I don't ride a 500 without a stabilizer if things are gonna be fast, too many religious experiences
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