Real Racing - Chatter issue - seeking advise

BowHunter · Apr 22, 2015

Hey Guy's,

I have some front end chatter - with the following charastics:
- Midcorner - lean above 50 deg
- far less at corner entry and/or on the brakes
- disappear as soon i get on the throttle

Relevant Bike setup (app 4000 kms old:
Std swingarm
Ohlins FGR fork - mountet in OEM 1199 std tripleclamps ( adapters on top to reduce diameter to the FGR diameter
24 deg inserts with new bearings
Bridgestone V02

I have tried the following - witch change the bikes behavior, but none effect on the chatter:
Ride height +/- 15 mm in small increments
Front compression and rebound - more and less
Front spring preload

Rear compression and rebound - more and less
Rear spring preload

New wheels
New tyres
Dunlop KR 108 UK tyres

Double and triple check on bike assembly - ie front end, wheels, frame/engine, Swingarm.

Could it be related to:
- Flex on the tripleclamps - any suggestions on brand to try, ie IMA, CNCRacing ?
- Swingarm bearings
- Real wheel bearings

bjorgens · Apr 22, 2015

What hot pressure are you running in the front? According to Dunlop rep over here. the recommendation when one gets front charter is to go UP in pressure... Counterintuitive, but the explanation was that at lower pressures, the contact patch is too large and therefore unable to release quickly enough. The result is grip, break free, grip, break free... OE Chatter. Raising the pressure reduces the momentary contact patch but increases the rolling contact patch because the tire isn't breaking free as often

I can follow the logic, but I always ran my ntec a ( UK and U.S. ) a little under the Dunlop recommendations of 33 psi hot off warmers.

Something to consider anyway

Cheers
B

fireman1251 · Apr 22, 2015

I get chatter with Dunlops, not with Pirelli's SC1.

BowHunter · Apr 22, 2015

Hi folks,

I used the Bridgestone V02 - @ 32 PSI hot
After changing to Dunlops KR106, I tested with my normal pressure - 32 PSI, tried to increase this to 36 PSI and lowered to 29 PSI - changed the steering a bit - no real effect on the chatter.

A bit more info - I use a 9,5 and 10,0 spring in the fork - and are app 98 kgs total with gear.

I will source a set of Pirellis for the next test - worth a try aswell- thanks

bjorgens · Apr 22, 2015

Check out Evol technology. They are developing some triples where flex can be tuned. Interesting notion... This picture on a motoamerica 675R. I have not seen in person.

Thamer · Apr 22, 2015

What's regular steering like...meaning when not really hard on the throttle and not greater than 50% lean?

I would think it could be steering bearings, not to say the triples per say. I would also check the triples really well if you have had a fall in recent past. these triples break/crack easily.

good luck and let us know what you find.

Gecko · Apr 22, 2015

Did you check the steering bearings play by retightening the steering nut?

BowHunter · Apr 22, 2015

Steering bearings are new this winter, and have beeb checked quite some times. i even increased torque from 25 nm to 35 nm just to test, no difference

weagi · Apr 22, 2015

Had the same problem with front end chatter initially thought it was a warped disc but realised it occurred only at hard breaking points so not a warped disc,eventually cured the problem by fitting slightly harder springs 10.25 (I'm about 84kg).
Try winding up the compression this may reduce the chatter.

Kraai · Apr 22, 2015

I would change to 10,5 springs and reduce your preload, this should resolve the issue. How is the wear on your front tyre?

ScrapperX · Apr 22, 2015

I'm not sure how you ride but from the description above it sounds like you got to much low speed compression dampening or incorrect oil height. The reason I say that is because it happens in mid corner and goes away when you get on the throttle.

1) I would first check the oil height and If its correct, then decrease compression gradually until the chatterering stops.

2) Your front and rear suspension should be in the middle of the stroke working together in unison. If you got too much squat in the rear it could be causing your front end to chatter too. Check your rear suspension.

Real Racing - Chatter issue - seeking advise

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