Projekt Kastor

[Rusty]

Ideally needs to be bolt on, which could be interesting. Old Scirocco brace went from wishbone to wishbone and had longer bolts for the wishbones!

[Rusty]

Managed to get out for a run down some proper roads and the difference is certainly there. Car feels sharp and the steering has a little more weight and self-centring. Still a few things left to do and a full alignment but as it stands, I'm looking forward to Combe more than normal

Nice when lots of small upgrades start to add up

[my2000apb]

any suggestions for good suspension design reading? in particular stuff related to mcphearson design

[afterburner]

Rusty: your subframe mounts have a 7.5mm offset, right?

[Rusty]

Yes, I think that's right. Could take it up to about 10mm. Could combine nicely with a 9mm offset top mount. Special top mount could see 12mm but gets a bit complex. Potentially an additional 3.5 degrees of castor.

[afterburner]

Well, as I have now two B4s I'm planning on going to the extreme with the one that I'm not keeping in OEM+ condition, so planning on cutting the turrets. I will make some solid subframe mounts with the maximum allowable offset, because I'd be able to compensate with the newly positioned top mounts. If I have enough room in the new turrets I'm also considering putting the solid subframe mounts in reverse and then switching the ball joints to give me even more (around 20mm) of offset in the ball joint position

How does this concept sound to you? Not done any actual measurements yet, just collecting ideas, as I'm almost finished restoring the garage and putting the project car in for surgery

034's subframe mounts have two positions, one at 12mm, I guess that's the maximum offset you could achieve? But now when I think about it... maybe that's with 12mm bolts. The 14mm ones would probably only go to 10-11mm before hitting the wall.

[Rusty]

The bolts are M12 or M10. If you're going extreme, then weld in some plate and tube to give the maximum offset and to lift the subframe a few mm to improve the wishbone angle.

Can't remember the bore of the subframe mounts but 10-12mm sounds about the most you could achieve.

Switching the balljoints sounds like an interesting idea and will give a lot more castor. Dont' forget that the front wheels are driven, so unlike BMWs and Mercs, which have 9+deg castor, you don't want to go too mad.

Clio sports have around 3 degrees of castor on a FWD car. Might be worth looking at other sporty options but 6-7deg sounds along the right lines with sticky tyres, less on street rubber where the reduction in contact patch with steering on could make traction worse.

If you can relocate the subframe pickups for the wishbones upwards, that will help some too.

[Error404]

Mr Crossfire is the man to talk to about this as he has done a motion study on the front suspension and also chopped his turrets out to fit camber/castor plates. IIRC he said around 9deg caster was the point at which you ceased to develop positive camber on compression. As you say though Andy, traction will become an issue before then I would think.
A good chunk of static -camber and 5 to 6 deg caster should be an excellent compromise. I was looking at a TT-RS front setup the other day

[afterburner]

Oooops, my bad, yes, the bolts are 10 and 12mm, not 12 and 14... Numbers tend to slip my mind nowadays...

About the wishbone angle - I'm putting weld-on ball joint extenders to my hub carriers, so the angle is not such a problem.

Am I right in thinking that more caster actually works better with high-profile tires than with low-profile ones? That's why the Clio, for example, having low-profile tires doesn't need as much caster, the tire itself doesn't deform as much.

My project is more of a gravel/snow rally type car with actually lifted suspension with a lot of travel. The car won't see any track usage. I'm planning on using 16" tires for more rim protection and because of tire/rim availability. That's why I think that in my case I will benefit from having as much caster as possible, unlike track driven cars. Again, any thoughts on that?

BTW - about the CV joints. On one of my cars I have shortened the steering arms by removing 12mm from them for more lock and faster steering. Before doing it I measured the limits of the CV joints and they could actually take some more, but I wanted to be on the safe side. That means that on a stock setup they could take a lot of angle before being damaged, actually.

[hiloran]

I moved top bearing as close to firewall as possible. For some reason didn´t want to cut firewall. Laser cut adjusting plates 30€ bearings+top nuts+housings 120€. Still going to put offset bushings. Should be good increase in castor. You need to have coilovers to get advantage from this

[afterburner]

So, this happened today...

[Audi_CQ]

I moved top bearing as close to firewall as possible. For some reason didn´t want to cut firewall. Laser cut adjusting plates 30€ bearings+top nuts+housings 120€. Still going to put offset bushings. Should be good increase in castor. You need to have coilovers to get advantage from this

This will get you a lot of caster without a doubt.
One disadvantage will be increased weight on front wheels and for an Audi that's not a good thing

[Rusty]

Why did you slot them?

[afterburner]

I wanted them finely adjustable, because of the adjustable top mounts I'm planning on mounting. Couldn't trust even the original position of the wheels. As I have more lock on the steering even with the original mounting points the wheels were touching the arch liners on the front on full lock and some compression. So I decided to get the guess work out of the equation and have them adjustable. Of course this raises concerns on how secure the front subframe will be now, but I believe the danger comes from side to side movement (like in hitting a curb ) more than longitudinal movement, and the slots are longitudinally cut, so I feel safe enough.

[Rusty]

Finally got the cast wishbones and new lower ball joints on, so it's ready for tracking next Tuesday at a place in Bristol I've not been before... Hopefully, that'll be all sorted for Combe and then I can sort some poly bushes and the V.2 top mounts, with a little more offset. I may also get some extreme spec offset subframe mounts too. The current ones fit well, so I'll run a Bach of them at some point