Board logo

bump steer
joolsmi16 - 18/6/10 at 09:46 PM

Hi all, my F27 is suffering with bump steering apart from moving the rack up/down is there anything else I can try first??

Cheers

Jools

jack_t - 18/6/10 at 09:50 PM

increase castor angle

matt_gsxr - 18/6/10 at 09:53 PM

You can get some bump steer if the rack isn't centralised (i.e. left-right). But that doesn't help you really.

I managed to sort mine out by elongating the steering rack holes and sliding the rack down a bit (this lowered it and moved it forward) by a few mm.

I used a laser pointer on the wheel, took off the sping/damper and moved it up and down by hand until the laser spot moved up and down (on the distant fence). Quite a pain in the bum, but gratifying once it is right. Be aware that adjusting one side of the rack affects both wheels in opposite senses so the process is a bit iterative.

Matt

whitestu - 18/6/10 at 09:57 PM

I've just sorted the bump steer on my Indy. Get the suspension settings as you want and then adujust the rack position to dial out bump steer.

I used a laser on a wheel with a vertical line on the gararge wall, and moved the car up and down on a jack with the shocks disconnected.
If the laser tracks the vertical line then no bump steer [mine didn't to start with].

Caster won't affect bump steer.

stu

joolsmi16 - 18/6/10 at 10:55 PM

Thanks all, will have a look to see if I can move the rack to dial it out..

Bluemoon - 19/6/10 at 10:28 AM

quote:
Originally posted by joolsmi16
Thanks all, will have a look to see if I can move the rack to dial it out..


Yep, job on my list two, will do as Stu above.. Not to hard to do, just need a bag of spaces (washers I guess) and patience!

Dan

RazMan - 19/6/10 at 12:11 PM

quote:
Originally posted by whitestu
Caster won't affect bump steer.


Just a thought here - if moving the rack forward / backward affects bump steer then surely rotating the uprights to give more / less castor will affect bump steer as the trackrod ends will be moved with the uprights, changing their orientation with the rack.

Does that make sense?

whitestu - 19/6/10 at 09:23 PM

quote:

Just a thought here - if moving the rack forward / backward affects bump steer then surely rotating the uprights to give more / less castor will affect bump steer as the trackrod ends will be moved with the uprights, changing their orientation with the rack.

Does that make sense?


It does make sense, but unless you have changed / modified the wishbones castor isn't adjustable on an Indy and also, getting rid of bump steer usually involves lifting the rack [or at least it did for me]. Changing castor will move the pivots backwards or forwards.

However changing castor will move the pivots up / down very slightly and lifting the rack will move things very slightly forwards.

Stu