911

We all suffer from understeer, and there are several ways to deal with this, but nobody talks about dialing in max positive CASTER into the front strut. Maybe this is because the stock top mount cannot be moved to achieve this, but looking at the Whiteline site, their project car has'max Caster'
The famous ALK aims in this direction but pits the wishbone in bind.This friction is made worse when you fit Powerflex bushes at the wishbone front.
I have fitted the little known MRT top mounts which allow massive caster AND camber adjustment all in one. A very simple design and it has worked a treat on my V3 STi.
Any thoughts?
Obviously, the pos caster brings in large neg camber on turn-in of the front wheels, and keeps static camber to a minimum for max grip on accelleration and braking.
Graham

Claudius

Excellent stuff Graham!

I'd like to do that, too. Where did you get the top mounts you mentioned?

JIM THEO

What about front ride height when cornering as max caster change roll center and do you have more dive when apply the brakes?
I believe that is extreme to use all the available caster front but this is personal opinion, I like always the middle settings.
JIM

911

The car brakes very straight, and hardly lifts on hard accelleration from a standing start or any on/off throttle at speed.
The mounts came from Town End Garage, or MRT direct, and were about £140 the pair. They have a solid spherical ball bearing in the housing as they are motorsport grade. There is a road spec too.
When I had the suspension set-up I asked for max Caster and camber, and the technician set the slide plate in this way. The advantage is that I can slide the ball joint to reduce the caster or camber to suit. The normal pillow blocks you can get only allow adjustment in one plane, usually camber. Really is worth looking at Whiteline and MRT sites. The set up on the car looks a little 'extreme', but the negative camber will help get the car round the tight bends of a hill Climb at race speeds! The car is arrow straight at 120 Km/hour.
Graham.

MarkT

Is this a road car?
ie are there any side effects of solid top mounts - noise, harshness etc.
Also will a spherical bearing last long on the road - designed to be changed quite often - eg rallying/racing
Road spec may be better.
Thinking of getting some so any thoughts helpful.
Mark.

[Edited by MarkT - 3/3/2003 12:11:43 PM]

Claudius

Thanks for that, 911. Found them on the MRT Site.

How do they work though?

911

Yes, the car is on the road, driven 3000 miles a year, but is used for serious hill climb competition work. It is a bit harsh and compared to my Audi A4 rough around the edges...Wear and tear is all part of running a modified car, so is no worry to me. On a good A road it is superb, better than my tweeked 911!
The mounts work very simply. Take off the Scooby top mount and bolt on the part you see in the MRT picture. Bolt it all in but finger tight. The plate with the bearing in it has 3 slots which corresond to the 3 bolts. The slots are very large, about 55mm wide. To adjust the mounting for camber/caster the slotted plate can be slid about to set the angles you need, and then the 3 bolts tightened so clamping the bearing plate in position. Realy is simple! Wish I had a digital camera to show you them in the car and the position set by Coordsport when thet aligned it all.
Graham

Claudius

Sorry for not getting back to you earlier, 911

Thanks for the explanation; that's not what I meant though I understand how you can slide the top of the damper around in the mount. I suppose you have to do this on a laser alignment thing then? What I meant is how can you adjust the castor and camber without graduation on the top mounts (looks like there isnt any)?

Can you confirm these mounts need adjusting on a laser alignment machine and cannot be precisely adjusted without it?

911

Yes, these mounts do not come with any graduations in either caster or camber planes. The initial setting is by laser, and to re-adjust from there would be very inaccurate with out using a laser again. 'Normal' top mounts only allow adjuctment for camber so making it simple to provide adjustment to a graduation. Always a down side isn't there!
Having said that, the mount has been set with the sliding plate hard against the static plate. This is to set maximum caster. The edge it is hard against is normal to the cenre line of the car so I could add graduations along that edge, say at 1.0mm intervals, mark a reference line in the sliding plate, and this would allow re adjustment at the racetrack. May be worth doing this come to think about it....hope this helps, sorry I misunderstood your question.
Graham.

Danny Fisher

I have a set of the HKS top mounts for sale if interested. Cost £180 new, looking for £100 + p.p.

Dan

Claudius

I have seen top mounts that are castor and camber adjustable with graduations, I think, but I'm not 100% sure. HKS / Cusco etc are camber adjustable with graduations, correct?

911

Yes, you are right, but I'm sure they only have graduations in one plan. Some time ago I emailed an American outfit who sold HKS top mounts, they told me they were handed to the car, BUT, if you fitted the left to the right and vica versa, they gave a small amount of positive caster increase as you increased the neg camber. Hope that made sense! I presume the slots were not normal to the centre line of the car but at an angle of about 15 deg. This didn't seem enough to me so I went the MRT route.
Graham

911

You always will get a rattle or two from spherical bearing top mounts. I have run these in my hill climb 911 Porsche for 8 years now and after 24000 miles, just oil every month!
The NVH is worth it for the performance. Rare to find anyone talking about caster on a Scooby, but Prodrive can't be wrong? I will be racing the car in anger in a months time....hope the understeer will be gone. Race speeds so much higher than a quick blast down a country lane!
Graham

MarkT

How much camber can u put on with these top mounts & how much is sensible on road ?
They look interresting.
Cheers
Mark

911

Coordsport managed 4 deg positive caster and 3.5 deg neg camber. the car also has the ALK fitted so looks a bit knocked knee'd, but drives very directly and no tramlining etc. All settings on Whiteline web site!
Graham

MorayMackenzie

Prodrive Group A pillowball topmounts make a big improvement to steering feel and dynamic camber through increased positive castor. Have had them on the car since 2000, IIRC, and they still seem to be working fine, abeit the occasional slight rattle inherent with the design.

[Edited by MorayMackenzie - 3/10/2003 1:16:25 PM]