Bike ?weaving? under heavy braking on track

[cropsprayer]

My bike seems to have developed a weave from side to side under heavy braking on track. I know a certain amount is expected as the rear wheel lifts and I?m used to that but mine seems to have got noticeably worse all of a sudden to the point I am not braking as hard as I could and would like to.

ive tried adding a bit more preload to the front forks but doesn?t make a difference. Any ideas?

 

[alex]

Increase rear rebound to slow the weight transfer forwards.

- Alex

 

[Zxcv12]

My bike seems to have developed a weave from side to side under heavy braking on track. I know a certain amount is expected as the rear wheel lifts and I’m used to that but mine seems to have got noticeably worse all of a sudden to the point I am not braking as hard as I could and would like to.

ive tried adding a bit more preload to the front forks but doesn’t make a difference. Any ideas?

What tyre pressure are you using on the front? And what tyres/condition?

 

[cropsprayer]

I’ve used both supercorsas and the 2018 compk slicks for the last couple
of events I’ve done and had the issue with both. I run 30/31 hot for supercorsas and about 28/29 hot for the slicks.

 

[r25sti]

have you checked the headstock bearings and steering damper.

 

[alex]

You're weaving cause you're braking harder with increased confidence.

Try to remove weight from the bars (grip the tank) and aim to reduce weight transfer speed.

Compression front, rebound rear. Its a seesaw. Just note what you change under braking can change corner exit behaviour too...

Try braking with only one hand on the bars, the harder you can do it in a straight line the better you're supporting your weight elsewhere.

- Alex

 

[bmwbadboy]

I think what Alex saying is what you should do.

I would also put a zip tie on a front leg at 25mm from bottom and check if you bottom out on front (meaning zip tie goes down to below 10mm)

All in all it sounds like suspension issue.

Sent from my Pixel 2 XL using Tapatalk

 

[cropsprayer]

I use the stock steering damper and just have it wound fully on but not checked it or the headstock bearing so I’ll take a look. Is there an easy way to test the headstock bearing?

 

[cropsprayer]

I did try that before increasing preload on the front as they were getting to within about 5mm of bottoming out. Now about 10mm after adjusting.

 

[bmwbadboy]

What's the wear pattern on rear tire after sessions where you push hard ?

 

[cropsprayer]

have you checked the headstock bearings and steering damper.

I use the stock steering damper and just have it wound fully on but not checked it or the headstock bearing so I’ll take a look. Is there an easy way to test the headstock bearing?

 

[soofsayer]

I use the stock steering damper and just have it wound fully on but not checked it or the headstock bearing so I’ll take a look. Is there an easy way to test the headstock bearing?

If the headstock bearing is worn/loose you get a little bit of play. You would notice it if you were riding the bike and braking and getting a torque wrench like clicking sensation through the bars. Tbh I have had headstock bearing issues in the past and it did not cause any degradation to braking or weaving, so I doubt that is that issue. Most likely suspension setup.

 

[cropsprayer]

What's the wear pattern on rear tire after sessions where you push hard ?

I seem to get pretty even wear to be honest especially when compared to some of the rears I see with tyre tear etc. I always buy new rather than try and save money using scrubs.

 

[r25sti]

I use the stock steering damper and just have it wound fully on but not checked it or the headstock bearing so I?ll take a look. Is there an easy way to test the headstock bearing?

i had a knackered gpr steering damper once and that caused weaving all the time and not just under braking. i would also try winding the damper out some, you shouldnt need it fully wound on. i dumped the oe for an ohlins. as you have said its an issue thats developed so i would look for something that has failed. could be warn bushes or even oil in the forks.
get someone to pull the bike up onto the stand to check the head stock bearing or use a abba type stand. once the fronts off the ground grab the bottom of the forks and move back and forth to see if theres any movement. also steer back and forth to feel for notches.

 

[alex]

The steering damper should be as, off, as possible.

Fully wound on may be interfering too much. (MCT set mine at 7 out from max).

The bike will correct a wobble if your shoulders and grip are relaxed enough to allow it.

10mm is better so the preload was needed.

- Alex

 

[cropsprayer]

i had a knackered gpr steering damper once and that caused weaving all the time and not just under braking. i would also try winding the damper out some, you shouldnt need it fully wound on. i dumped the oe for an ohlins. as you have said its an issue thats developed so i would look for something that has failed. could be warn bushes or even oil in the forks.
get someone to pull the bike up onto the stand to check the head stock bearing or use a abba type stand. once the fronts off the ground grab the bottom of the forks and move back and forth to see if theres any movement. also steer back and forth to feel for notches.

Thanks very useful info and I will try this. I see Alex has also said I have the steering damper set incorrectly so definitely one to look at and I have thought about switching to an aftermarket version but pretty expensive!

 

[cropsprayer]

The steering damper should be as, off, as possible.

Fully wound on may be interfering too much. (MCT set mine at 7 out from max).

The bike will correct a wobble if your shoulders and grip are relaxed enough to allow it.

10mm is better so the preload was needed.

- Alex

i think it has 9 clicks of adjustment full to full so I am way off then! Why should it be fully off though just for my knowledge?

 

[r25sti]

i think it has 9 clicks of adjustment full to full so I am way off then! Why should it be fully off though just for my knowledge?

you shouldn't need a damper at all, its just there for that just in case moment. if the bike is set up spot on and your not fighting the steering then you wouldn't really need one. defo worth winding it nearly off and giving it ago.

 

[alex]

They said to me if you need one something else is wrong. Its there to smooth out, not restrict.

- Alex

 

[Ma Salope]

Hi I had the same on my 2011 on track, fitted Ohlins cartridge kit and all the weaving stopped. You prob need heavier springs in forks. But my advise it go for a cartridge kit with springs for yr weight .