Bike ?weaving? under heavy braking on track

[alex]

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 .

Think he's just bottoming out too fast?

- Alex

 

[cropsprayer]

Think he's just bottoming out too fast?

- Alex

Sorry for another question on this Alex but your previous post said to add some rear rebound which I get will slow the weight transfer forward and hence stop the front diving so quickly. If I add more compression to the front would that not have the same effect? If so how do you decide best which adjustment to make where?

like I say apologies for the additional question it will just help me with my understanding more on the suspension side. Also just for info I have ?hlins front and rear suspension on the bike.

 

[bmwbadboy]

Sorry for another question on this Alex but your previous post said to add some rear rebound which I get will slow the weight transfer forward and hence stop the front diving so quickly. If I add more compression to the front would that not have the same effect? If so how do you decide best which adjustment to make where?

like I say apologies for the additional question it will just help me with my understanding more on the suspension side. Also just for info I have ?hlins front and rear suspension on the bike.

if you want to stop weight transfer to front, you want to do both. in addition to that, you want to increase comp in rear as well.

also, I would zero (or decrease) preload on rear.

btw, front zip tie should be in region of 15-20mm, not 10.

 

[alex]

Increasing rear rebound slows the action of the rear shock expanding. Which stops the rear ejecting you out of the seat...and therefore the weight of the bike forwards.

Obviously this won't stop weight transfer but it may allow you to get more braking done before bottoming because you come in flatter and you keep the rear on the deck longer.

(Which mode disables the combined front and rear brake btw? Anyone? Slick only or Slick and Race).

Compression on the front slows the dive but if the springs aren't hard enough then nothings gonna stop you hitting the bottom.

Preload is best for trying to stop the forks smashing flat with the springs you have. Bottom is 8mm above casting. I would aim for 15mm above for a safety margin for the 'oh f**k' moments.

Every adjustment is a trade off.
Change one thing per test.

What do you weigh kitted and what are the spring rates fitted?

- Alex

 

[bmwbadboy]

In addition to what Alex wrote above,

the best indicator of whats wrong or whats not wrong, is not your human senses, but the tires (especially if you're running slicks).

Look at tire wear after every session and if they dont look like a sandy beach sand, immediately question your suspension/pressure settings.

 

[DrIoannis]

Do you have ABS on while you are in the track? If you do then turn it off and try again. I turn ABS off in the track because I had the same feeling you describe.

 

[Ma Salope]

Do you have ABS on while you are in the track? If you do then turn it off and try again. I turn ABS off in the track because I had the same feeling you describe.

Will have nothing to do with ABS, it's down to set up.

 

[cropsprayer]

Increasing rear rebound slows the action of the rear shock expanding. Which stops the rear ejecting you out of the seat...and therefore the weight of the bike forwards.

Obviously this won't stop weight transfer but it may allow you to get more braking done before bottoming because you come in flatter and you keep the rear on the deck longer.

(Which mode disables the combined front and rear brake btw? Anyone? Slick only or Slick and Race).

Compression on the front slows the dive but if the springs aren't hard enough then nothings gonna stop you hitting the bottom.

Preload is best for trying to stop the forks smashing flat with the springs you have. Bottom is 8mm above casting. I would aim for 15mm above for a safety margin for the 'oh f**k' moments.

Every adjustment is a trade off.
Change one thing per test.

What do you weigh kitted and what are the spring rates fitted?

- Alex

The bike had the Ohlins front forks when I bought it and the springs fitted are set for 84KG to 89KG without gear. I'm 80KG without gear. It say the springs are 10.5/11.0 Nmm springs.

 

[cropsprayer]

In addition to what Alex wrote above,

the best indicator of whats wrong or whats not wrong, is not your human senses, but the tires (especially if you're running slicks).

Look at tire wear after every session and if they dont look like a sandy beach sand, immediately question your suspension/pressure settings.

Thanks, my tyre wear has always been good on this bike and no 'bands' or chewed up rubber like I see running through other peoples. I have an Ohlins rear shock that I bought new and Harris set it with 'standard track settings' which I have never altered. Mainly because I don't like messing with something that I thought wasn't giving me an issue when I am far from being a suspension expert

 

[fast_ryan]

Suspension Setup

...'standard track settings' which I have never altered. Mainly because I don't like messing with something that I thought wasn't giving me an issue when I am far from being a suspension expert

Suspension setup is a continually evolving process. The bike will behave differently as your pace increases so you can never just rely on ?standard track settings?. All they provided you with is a base setting from which to work from and improve. The next time you are on track just speak to the suspension technician there and they should be able to help translate your ?feeling? on the bike into meaningful adjustments which will help you.

 

[alex]

Re: Suspension Setup

Suspension setup is a continually evolving process. The bike will behave differently as your pace increases so you can never just rely on ‘standard track settings’. All they provided you with is a base setting from which to work from and improve. The next time you are on track just speak to the suspension technician there and they should be able to help translate your ‘feeling’ on the bike into meaningful adjustments which will help you.

+1 to that, each track is different, some have big stops others not so much...

 

[cropsprayer]

Re: Suspension Setup

+1 to that, each track is different, some have big stops others not so much...

Thanks guys makes sense and I’ve done this before but I tend to use NoLimits and these days they no longer have Parkitts along to euro or U.K. events. If you ask anyone in the garage everyone is an expert on how many clicks of this that and the other you must have!!

 

[DrIoannis]

Will have nothing to do with ABS, it's down to set up.

I had this feeling with stock suspension and full Ohlins setup. As soon as I deactivate the ABS this feeling disappears. He can try it and see how it goes. It is not a problem with ABS which makes a very good job, but the rear gets lighter in braking and combined brakes engage the rear brake which gives this feeling.

 

[cropsprayer]

I had this feeling with stock suspension and full Ohlins setup. As soon as I deactivate the ABS this feeling disappears. He can try it and see how it goes. It is not a problem with ABS which makes a very good job, but the rear gets lighter in braking and combined brakes engage the rear brake which gives this feeling.

I’ll try it as I do leave on and run in Race or Slick mode.

 

[Oli]

... (Which mode disables the combined front and rear brake btw? Anyone? Slick only or Slick and Race). ...

The combined brakes are only deactivated in Slick Mode or the Slick ABS setting within User Mode


- Oli

 

[alex]

Ressurecting this.

At Portimao braking for T5 I have been suffering a lot, actually collided with another rider (both stayed upright, no real damage).

All attempts to haul down from the top of 3rd (16/43) ~130>50mph and 2nd gear have the same result.

Symptoms: Moderate front brake applied. Bike weaves under braking. Bike does not slow down anywhere near as fast as some others.

I am in USER: Race ABS atm

I think the rear ABS is causing the front to release because the rear brake is applying and the unloaded rear is skipping and locking over the bumpy surface.

Today I will switch to SLICK ABS and pray I don't do an endo...

Will report back, from A&E later lol

- Alex

 

[Oli]

I don?t think the weaving is due to the ABS setting, IMO it is a hydraulic issue, perhaps some additional compression damping at the front and rebound at the rear will help control the weight transfer better when you hit the brakes?

- Oli

 

[alex]

Its the bumps...

- Alex

 

[fast_ryan]

USER Mode: ABS

I am in USER: Race ABS atm

Put the ABS in SLICK, or turn it off altogether, on track and the front and rear feeling under braking is much better especially over uneven surfaces.

 

[alex]

Its now arrow straight
Pulled up in a shorter distance in a 2 lap test too.
Being careful to incrementally test front end grip.
Might try backing it in now (I jest)...

V02's went on yesterday for a session. Now for a full day.

Suns out time for a lap record...

- Alex