luke2152
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| posted on 8/6/15 at 10:53 AM |
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car steering under power
Have just had my mazda based gbs zero set up by procomp. They did the best they could with the limited adjustments available (none on the rear and
camber on the front). Vastly improved I might add but there is a serious problem with the handling. When hard on the power the car pulls to the
right and when I come off the throttle it pulls left. This effect feels like it's coming from the rear end. Its enough that it's difficult
to keep car in one Lane when coming off throttle at fairly high speed. Steering is generally quite light and nervous anyway.
Of course I've been on phone to procomp and they suggest it's maybe due to the high amount of rear toe in (5.5mm and not adjustable) and
suggested dropping the back a little to give more castor and stability.
Just wondering if anyone else has any thoughts and suggestions.
Cheers,
Luke
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JAG
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| posted on 8/6/15 at 11:38 AM |
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The only time I've come across this phenomenon I/we found a broken suspension linkage on the rear axle.
This was allowing the rear wheel's to move independently under acceleration and lift off and was giving the rear wheel steering that you
describe.
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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Dick
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| posted on 8/6/15 at 11:40 AM |
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Check the wheel base side to side
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keithjardine
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| posted on 8/6/15 at 02:38 PM |
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Are you running a LSD?
Are tyre pressures uniform across the axle?
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theconrodkid
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| posted on 8/6/15 at 03:06 PM |
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i had that on my 5,tyre pressure was down just a couple of pounds on one rear wheel,it dont take much !.
why cant the rear toe be adjusted,cant the bolt hole be elongated ?.
who cares who wins
pass the pork pies
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luke2152
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| posted on 8/6/15 at 03:31 PM |
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Jag - not sure exactly what your describing - do you mean on a live axle? As this is an IRS rear end. Regardless I'll have another check to
make sure everything is moving freely.
Dick - The wishbones are equal length and equal distance from centre. The driveshafts are 40mm different in length by design which could cause a bit
of torque steer but they are very heavy duty so I wouldn't think much at all.
Keithjardine - I have a helical lsd and I'm going to recheck my tyre pressures although I did this not long ago.
conrodkid - The mx5 hub can't be shimmed as the upright bolts straight through the wishbone rather then the hub bolting to the upright.
Also noticed one of my cv joints is buggered but I don't think that would be the cause as its still holding together? Will get it sorted this
weekend anyway.
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ian locostzx9rc2
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| posted on 8/6/15 at 04:43 PM |
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I think you may have found the problem worn cv joint .torque steer from the rear due to cv joint worn .
[Edited on 8/6/15 by ian locostzx9rc2]
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big-vee-twin
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| posted on 8/6/15 at 05:24 PM |
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First thing I would do is check tyres.
Had this on my tin top and it was a faulty tyre.
If you think its at the rear swap tyres over side to side and if it does the same but in opposite direction its a tyre. If nothing changes put them
back on the correct side and check front.
By process of elimination you will find the tyre.
If no difference at all then look for something more mechanical like cv joint, brakes etc..
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
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theconrodkid
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| posted on 8/6/15 at 07:01 PM |
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where the wishbone goes onto the chassis,elongate the holes there
who cares who wins
pass the pork pies
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britishtrident
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| posted on 8/6/15 at 07:37 PM |
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quote:
Originally posted by ian locostzx9rc2
I think you may have found the problem worn cv joint .torque steer from the rear due to cv joint worn .
[Edited on 8/6/15 by ian locostzx9rc2]
That isn't possible.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 8/6/15 at 07:49 PM |
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The most likely cause is the thrust line of the rear axle is skewed, to one side, you would need to make the rear toe adjustable to fix it.
However one other thing you could check is the wheel offset is the same also the tyre size and if the tyres are an asymmetric design or have rotation
direction arrows they are fitted correctly.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Dick
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| posted on 8/6/15 at 08:53 PM |
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u2u sent
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big_wasa
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| posted on 8/6/15 at 08:59 PM |
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The top bushes in the rear mx5 uprights are very soft.
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ian locostzx9rc2
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| posted on 25/6/15 at 09:26 PM |
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Did you fix the problem ?
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luke2152
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| posted on 25/6/15 at 09:58 PM |
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Problem solved as of today. Big_wasa was on the money it was just soft squishy bushes in the mx5 uprights. Replaced with harder poly ones and
problem gone.
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