Custom control arms

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mat_GTI-R's picture
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Québec

Jan 23, 2008
Custom control arms

Hello, just wondering if it would be possible to have custom front control arm fabricated in order to move the balljoints forward a bit .... an inch or so? Why? To fit larger wheels/tires without having to cut the firewall. I wouldn't mind cutting the rear fenders or the front bumper... but the firewall... :-\

I know it can be done, but can it be done without having to modify other major suspension components? This would also result in more aggressive caster angle...

Pulsar666's picture
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Erik
laval

Jun 10, 2012

more caster is not a problem, but the rest of the geometry will be a problem if not done right.

mat_GTI-R's picture
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Québec

Jan 23, 2008

That's what I'm asking... Can I move the balljoint forward an inch and then do a proper alignment and done? Or will I encounter any problems with the axles, tie rod ends or struts...

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Nicholas Chu
Vancouver

Jan 24, 2008

how big of a tire are u trying to stuff? or what is your end goal you're after?

to be honest i think a 225 - 245 r comp is enough tire, the key is getting the right spring rates, caster, and roll center correction.

redrilling and cutting the hole on the stock shock tower and using the gc top hat will give you the camber and caster you need.  i was running 4+ degrees of caster, with greater than -3 neg camber.  I was also running 600 front 700 rear springs and altho on the street the car was acceptable, its not something i want to do everyday.  key is correct suspension setup. and the 2 way rear diff, boy does that make a difference.  

using a roll center balljoint will correct the shitty camber curve (which gains positive camber by the way once you're lowered).  i never got around to installing this but i have roll center correcting ball joints to go with my bumpsteer kit.  this will be the biggest fix for the poor handling.  as you will be into gaining negative camber again and increased roll resistance.

i was extremely competitve autox locally in raw time on skinny 195 r1r's on the stock turbo.  i am just too cheap to pony up money for hoosiers on my non competitive autox car.

 

anyways good luck, i might be out of the gtir game in a weeks time.  its been fun

 

Lynx's picture
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London Ontario

Dec 23, 2009

are you already running caster bushings?  Thats essentially what that system does.  pivots the control arm forward to allow for more caster.  The difference in what your suggesting is the pivot.  I can't imagine anything else being a problem other than the front axles.  You will have to take the spring off the shock and see how far you can go and still have the sliding joint in the axle meshing properly.

Unfortunately mchpherson strut suffers from bad dynamic camber curve.  Ideally you would adjust the suspension so that the LCA is pointing towards the ground and have the maximum compression of the suspension(in a turn) bring you to the point where the LCA is parallel with the ground.  This gives to a camber curve that is more negative as the car rolls and will result in the tire remaining more level with the tarmac instead of rolling over.

 

The other thing that you must consider other than length of axles is the pivot point of the suspension while turning and the scrub radius.  Lots of scrub and the car will really wrestle with you when fighting for grip especially over bumps.  The tires will also have a tendancy to toe in on acceleration and out on decel unless every bushing you have in there is solid.  You are essentially providing the tire with more leverage to turn around the steering axis.

 

At the end of the day you are really limited with what you can do to fix the GTiR suspension because from the start it is designed to work within tight parameters.  Also If modform can fit 255/50R17 I can't imagine ever needing to go bigger on an AWD sub 2600 lb car.