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Author Topic: Fun & Games with ball joints - more camber & castor on a Mk1 golf chassis?  (Read 561 times)

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Offline smellyermaa

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I've been rebuilding the front end of the daily hack Audi 80 TDI for the last few weeks - wings, bumper, bonnet all repaired or replaced, and freshly repainted.

It's also had the subframe and wishbones off, both repainted, and wishbones poly bushed, ball joints, etc…. and that's what got me thinking.

The bottom ball joints on the Audi are offset, and longer than the Mk1 Golf / Scirocco ones. They're a 19mm pin rather than 17, but I was thinking they could be a fairly easy way of getting more castor and camber angle. The holes sort of line up, but the wishbone would need a bit of modding to hold it properly - extending round the sides of the new ball joint, and maybe a little strengthening. The ball joint hole in the bottom of the hub could be bored out to 19mm without a problem, I think.

Here are a couple of pics to explain. It's using the wrong wishbone, but if it was on the other side it would work - I just grabbed the first one that came to hand. You'll see the offset I think and get the idea.

Wishbone with Mk1 golf wishbone, and audi ball joint next to it. Offset is about 20mm


The holes are close enough that they could be made to line up I think.


So I wondered if anyone else has looked at different ball joints on the Mk1 wishbones? Did you find any that gave the right fit and extra castor, and fitted as well or better? I think they might be a little taller as well, so there could be an additional benefit in a slight extension to the ball joint.

Still need to do some more measuring up. I didn't have much time on Sunday as I had to go on a biz trip.

Thoughts? Cheap and cheerful way of improving the handling, tried it and it didn't work, or an accident waiting to happen?
« Last Edit: March 25, 2014, 03:37:21 pm by smellyermaa »

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Offline Tim Moll

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Good find and similar effect to what I've done on the racecar.....can't comment on durability/reliability but will be able to in the next month or so as first race of the season is 26th April  :o






Offline smellyermaa

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I knew I'd seen something similar, but couldn't remember where.

I'm no engineer, but I'm thinking that moving the ball position relative to the wishbone is going to create more of a twisting load on the wishbone and the ball joint plate, which they're not really designed to take.

Instead of the spring pushing down and the loads from the weight of the car on the road pushing up through the ball joint in line - in the centre of the wheel, I think they might be offset with the balljoint out of line with the spring load - is that the King Pin Axis? (probably using the wrong terms but hopefully you know what I mean)….



So the force of the spring is still on the centre of the wheel, but the upward force is more towards the back of the wheel.

I don't know if it's strong enough or going to bend when you go bouncing over a kerb at high speed. I was thinking I would need to strengthen the wishbone around the balljoint to help, with the audi ball joint, although on the other hand it's designed for a car that's 50% heavier than the A1 chassis. The advantage of your solution is you're using the standard pin size and don't need to modify the hub.

I guess you'll find out the first time you take it out testing - I'm sure that's a better guide than my guesswork!

Offline Smudge

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If you are worried about the additional forces on the wishbone you would be better off moving the position of the rear wishbone bush. On the mk2 you can use eccentric rear wishbone bushes. On a mk1 could it be fairly easy to move these around on the chassis? Maybe add a new stud to mount them? You only need to move it 10-15mm.
See my MK2 Golf 16v in the members section.


Offline smellyermaa

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Surely if you move the rear mount, you need to move the front one as well, which is a bit more involved?

I think I'd rather beef up the wishbone around the new joint and see how it goes.

If I misunderstood feel free to correct me!

Offline Smudge

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I'm only talking of using the front mount as a pivot and arching a circle out from its centre, moving the rear mount along this arch line a few mm will increase caster, there should be enough flex in the front bush to allow thus movement which will be a small amount at the front bush.
See my MK2 Golf 16v in the members section.


Offline smellyermaa

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Ah, I see what you mean - interesting idea.

Depends on the bushes I suppose. I'm not sure it's a good idea to put constant stress on them though - that's why you normally fit wishbones, and then torque them up with the wheels back on the ground - wishbone sitting in the natural position to minimise stress on the bushes.

I'll need to check regs to see what I can get away with, and if it's not allowed for classic touring cars, it's just a neat idea to try out on the trackday car.



Offline Smudge

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Something like this.





You can see from the drawing that the front bush is only twisted very slightly.

12mm of movement in the LBJ equates to around 1.5 degrees of caster. STD a mk2 a Golf only has around 1.5 degrees of caster, which is not good!


« Last Edit: March 28, 2014, 09:09:24 pm by Smudge »
See my MK2 Golf 16v in the members section.


Offline Topsonedp

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Resources for research for excellent content to the great success of it.

Offline Jon Olds

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Good info, food for thought
Jon

 

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