GEOMETRY EXPERTS

Here is the question

after setting preloads on the bike, everything is much better than stock

but on straight líne, Under hard acceleration on 4th and 5th

i get some inestability, the bike moves like a snake

I was thinking on going 1 teeth down on the back sprocket, especially to move the rear tire a bit backward and also make the gearing a bit less responsive

what do you guys think

i already have 1 teeth down on the front, do the gearing is already shorter than stock

Lengthening the wheelbase will help. If you are happy with the amount of drive, I would keep the gearing the same and lengthen the chain.

Measure your ride height before making the adjustment. After adjusting, measure the ride height again. Due to the eccentric hub, they may change. Either add/remove preload from the shock, or adjust the shock length, to get the same ride height.

Easier, is to adjust shock and fork damping.
Try +4 clicks on shock comp damping.
This will slow the rate of 'squatting' under hard acceleration. It will marginally reduce edge grip. Stopping the bike from squatting will keep it stable.

Try -4 clicks on fork rebound damping.
This will allow the forks to extend quicker, as the bike pitches backwards under acceleration. Keeping the front wheel in contact with the ground will keep the bike more stable. If you reduce rebound too much, when you release the brakes on corner entry, the front of the bike will lift too quickly and make turning the bike harder.

If you are on the standard bike, the shock spring is quite soft for track use, and this could be changed to a 10/10.5/11Nm spring.

Try the damping changes first, if no benefit, try the wheelbase, if still struggling, try the damping with the wheelbase, and finally try the spring.

Thanks for the advise man

RickD996 said:

Lengthening the wheelbase will help. If you are happy with the amount of drive, I would keep the gearing the same and lengthen the chain.

Measure your ride height before making the adjustment. After adjusting, measure the ride height again. Due to the eccentric hub, they may change. Either add/remove preload from the shock, or adjust the shock length, to get the same ride height.

Easier, is to adjust shock and fork damping.
Try +4 clicks on shock comp damping.
This will slow the rate of 'squatting' under hard acceleration. It will marginally reduce edge grip. Stopping the bike from squatting will keep it stable.

Try -4 clicks on fork rebound damping.
This will allow the forks to extend quicker, as the bike pitches backwards under acceleration. Keeping the front wheel in contact with the ground will keep the bike more stable. If you reduce rebound too much, when you release the brakes on corner entry, the front of the bike will lift too quickly and make turning the bike harder.

If you are on the standard bike, the shock spring is quite soft for track use, and this could be changed to a 10/10.5/11Nm spring.

Try the damping changes first, if no benefit, try the wheelbase, if still struggling, try the damping with the wheelbase, and finally try the spring.

Click to expand...

rick

one question

does making the rear wheel backward

LOWER THE REAR HEIGHT?

o raises it?

Sounds like the shock is in the bottom of the stroke in which there is no way for it to absorb any other stresses. So everything that happens in the rear just goes right from the rear through the chassis to the bars. Not knowing any other details of the bike, might start with preload and/or spring rate if everything else is to remain constant. Just my two pennies...

RODOLFO said:

rick

one question

does making the rear wheel backward

LOWER THE REAR HEIGHT?

o raises it?

Click to expand...

It depends on where you start from with the eccentric hub! The only way to tell is to measure.

I'm not sure if the hub can just be continously rotated, or whether it has restricted range, say 90 degrees, or 180.

Thanks guys

well i think there is just one way to find out

today i changed the rear sprocket to 1 teeth down from stock on the back

aleady had one teeth less on the front

(Also for general information 2 teeth down is as low as you can go without cutting the chain, i found out the hard way)

15/40

the rear wheel is almost all the way back

will test it out on the canyons this saturday and on the track néxt weekend, to see how it performed

How much do you weigh? Sounds like the bike is under sprung.

jmhamilton68 said:

How much do you weigh? Sounds like the bike is under sprung.

Click to expand...

hi man

i am 170 without gear

How did you get along with your changes RODOLFO?

I have been getting more confortable with the bike

I have done a few things

first i went less preload on back

Softer damping on rear shock, as bike was way hard and unstable on bumps

Also extended the rear shock 4 turns

this, and being more gentle with the throttle has helped alot (i came from an R6, were it is all or nothing)

also put on a set of pirelli TD, best tires for street/track i have used