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Old 29 Jun 2015, 06:52 (Ref:3554655)   #1
Al Weyman
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What are the negative effects of tracking change during travel of suspension?

I have just discovered due to a bent centre link on the Camaro causing the steering arms and lower wishbone to not align correctly on one side that I am getting over an inch change in the tracking from ful droop to static ride height. Just wondering what would be the effect of this on track as its been like this for many years? I could have asked effects of bump steer but felt that's the result not what's specifically happening..
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Old 29 Jun 2015, 19:21 (Ref:3554772)   #2
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There are 2 types of bump steer , one from soft or worn joints which allow the wheels to move out of alignment . And the main one which is where suspension movement affects the steering giving unwanted tracking variations .

It sounds like you have one where one side of the steering alters the tracking with suspension movement .

The worst one I have come across was about 40mm of tracking movement from suspension travel , & that made the car very twitchy & difficult to control , excessive tyre wear , erratic breaking & not very nice at all .

Normally a few mm of variation is about the best that can be got [ depending on car etc ] , but if you have 1" then it would be a lot better if you can dial that out .
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Old 29 Jun 2015, 22:29 (Ref:3554800)   #3
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Al most cars will alter between max and minimum travel but it's unusual to actually get full movement especially on a race car with stiff springs and shocks. Incidentally I used 600 lb front springs on the Anglia.
Unless the design is sophisticated in the first place and presumably you want to keep it how it was made, as long as every thing is in order the only way to stop it is to limit the movement .
Alternatively with the springs removed and the car on a trolley jack or a wheel free ramp it can be possible to reshape/redesign the steering arms to limit bump/rebound.
Most road saloon based race cars have lowered suspension that can cause problems because the steering angles were not designed to be run in that position.
I don't know what type of suspension you have on your car but when it's at its loaded static ride height what angle are the lower arms in relationship to the ground ?
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Old 2 Jul 2015, 17:37 (Ref:3555421)   #4
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Originally Posted by GORDON STREETER View Post
Alternatively with the springs removed and the car on a trolley jack or a wheel free ramp it can be possible to reshape/
Rather carefully I would suggest!

If forged then after heat and application of a large err, "Reshaping Hammer" then they can break: rather suddenly..........

As happened to me..........

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Old 2 Jul 2015, 22:30 (Ref:3555493)   #5
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Rather carefully I would suggest!

If forged then after heat and application of a large err, "Reshaping Hammer" then they can break: rather suddenly..........

As happened to me..........

A good point, however I have successfully done this admittedly on lightweight cars but not "extreme" reshaping and not using a hammer.
Most steering arms don't tend to be made out of an "inflexible material" as they could break quite easily given the constant punishment they are given (especially on the crap roads around my area in the UK) !!!!!
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Old 5 Jul 2015, 08:48 (Ref:3555874)   #6
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Originally Posted by Al Weyman View Post
I have just discovered due to a bent centre link on the Camaro causing the steering arms and lower wishbone to not align correctly on one side that I am getting over an inch change in the tracking from ful droop to static ride height. Just wondering what would be the effect of this on track as its been like this for many years? I could have asked effects of bump steer but felt that's the result not what's specifically happening..
For a couple of years the corolla had over half an inch of bump steer on both sides. After getting it down to around 1-2mm the result was around 0.25 seconds faster.

The best way to describe it is it is like replacing totally worn out bushes and joints. The car was much easier to place in a corner, felt more predictable and generally inspired more confidence, hence I felt I could push closer to the limit.

Keep in mind that my cars lap times where almost totally dictated by rear end grip, this was a good improvement for a weekends work and a couple quid.
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Old 7 Jul 2015, 21:49 (Ref:3556625)   #7
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Tracking change make the tire to a small amount slip sideways, which means that the tire does not grasp fully the road. This grip loss must be deducted from the otherwise available grip the car needs to maintain itself in its proper track on the circuit. It therefore becomes slightly worse overall grip. Now I speak only about the handling and omits the second load situations.
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Old 12 Jul 2015, 11:23 (Ref:3557785)   #8
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Wouldn't it depend it it is toe ing in or out and what your car needs (I.E. it could be a positive)
And it is only on droop? Nothing on bump?
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Old 28 Jul 2015, 13:45 (Ref:3561953)   #9
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Well I replaced the centre link and completely dialled out all the tracking variation between full droop and static ride height and went back to Brands at the weekend. The car felt a fair bit more stable in the corners especially the left handers where I was getting a fierce wobbling and understeer. I arrived late for qually so only got 3 minutes or three laps so never got going then for the race I was getting baulked and boxed in as started from the back and I am not the most pushy of drivers so never got a decent lap time in but I matched the Speedfest times and with a lot less drama so I recon it would have been worth a good second or two although in fairness I did do some other tweeks. .
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