
Racer 'unstable' Under Hard Braking !
#1
Posted 06 May 2012 - 10:48 AM
My 1330 racer seems to be unstable when braking hard. That is only at the two corners that I enter at full speed that is approximately 110 mph (not true) That is when braking between the 100 and 50meter mark from the corner.
Some specs:
I have the hard/soft combo tie rod bushes from minispares
Tie rods are modified standard ones to allow to be adjustable. The adjustable part screws in over the tie rods is double the thickness of the standard rods, and the original rods was tapped to fit. (see if I can post a picture tomorrow)
Cones are however old ones (pre 80's)
New set of lower arm niches for change camber
Shocks are gaz adjustable, running on 22 of the 32 clicks at the front. The back is much much softer.
Brake bias at back is nearly nothing (as I rolled my previous car due to back wheel locking up)
Running yoko A008's at 1.7/1.8 bar right around.
I know that I will be told to replace the cones and the tie rods and will appreciate those comments (as i am planning to do it in about two months time, but i would have then competed in two more races) although I will also like to know what else must be checked or looked at.
Also, thinking ahead on my side -
Can it be that the back of the car is to light, lifts and then get unstable?
Can the camber toe and caster setting influence it. Caster to max not to touch STD body work, toe out and 1/16th, camber about 2.5/3deg
Will the ride height play any role in it ?,
#2
Posted 06 May 2012 - 11:01 AM
back to basic tyre pressures, and wheel balance?
which track are you unstable at?
#3
Posted 06 May 2012 - 11:05 AM
you know what happens on a bike when the front brake is applyed to much!

#4
Posted 06 May 2012 - 11:28 AM
#5
Posted 06 May 2012 - 01:36 PM
#6
Posted 06 May 2012 - 01:54 PM

rear toe settings can effect it, too much toe out/not enough toe in will make it squerm.
if the front is set too soft then it will pitch too far forward and lift the rear up more, but id suggest leaving that for optimum cornering over braking.
and again id say like everyone else brake bias, if the fronts dont want to lock up then move it forward slightly, you might be suprised at how far forward it goes before the fronts lock.
hope ive helped! :)
#7
Posted 06 May 2012 - 01:58 PM
#8
Posted 06 May 2012 - 02:08 PM
Its not clear if hes referring to a judder or a balancing problem
#9
Posted 06 May 2012 - 03:17 PM
my racer was running 5 deg caster
and yes maybe to much braking on the front
#10
Posted 06 May 2012 - 03:22 PM
Thanks so far ..
Just to answer some questions, and explain my brake setup.
By unstable I am trying to explain the feeling of the back of the car 'stepping' out under hard braking, to the one side and it feels like to the right first. It feels like if the back is trying to come around ( the same feeling I had when my brakes locked up last time) Naturally I correct it and then it starts moving left to right, until I get of the brakes. you can say the back of the car is swaying, if it is the correct word to use.
At this stage my front brakes Is not locking up. I have a single master cylinder with Cooper s setup with a single line and pressure regulator on the back subframe. The brakes at the back are adjusted so that when the car is on the jacks, and the brake is applied, the back wheel can just, just be turned by hand, as per bill sollis' book.
Can it be that the grip on the back tyres are not as good as it should be ? It seems that the a008's rubber might be a bit on the hard side !
Edited by Sputnik, 06 May 2012 - 03:31 PM.
#11
Posted 06 May 2012 - 03:55 PM
#12
Posted 06 May 2012 - 04:42 PM
I'd advise a good geometry check to make sure all is equal side-to-side as a start.
#13
Posted 06 May 2012 - 04:57 PM
#14
Posted 06 May 2012 - 05:16 PM
#15
Posted 06 May 2012 - 05:21 PM
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