Compression Struts / Anti-Roll Bar

[Roy Kemp]

Hi chaps,

I've just bought a pair of compression struts for the front of my Escort-based S3 Phaeton.

For those of you who have done this conversion, do you just bin the ARB altogether, or have you modified it with drop links and retained it for use as a pure anti-roll device now that it doesn't control axle location?

Thoughts?

Cheers

[Adrian Southgate]

So you bought the compression units that go behind the TCA. I reckon try em with no ARB and see what happens, you can always add the arb back into the equation later.

[1u78f7ifsodyj]

As the anti-roll bar was designed for an Escort which weighs about a ton it must be far too stiff for a lightweight Dutton, and apart from the locating function it is probably quite unnecessary.  

[Roy Kemp]

There is this on Pistonheads... thinning of the ARB. 

https://www.pistonheads.com/gassing/topic.asp?h=0&f=30&t=14...

But I guess you guys are right. Try without and see how it goes.

[Steve and Matt Pegrum]

We've had good results with replacement fabricated lower wishobones to replace the escort TCA and removed the ARB altogther.

Had to add an extra chassis bracket each side and drill out the TCA mounting hole in order to use Locost style brackets/bushes. Considered Tension struts (not compression as they're the wrong way round) but thought they're way too expensive for what they are and also has advantage of not welding onto the TCA for the spring mounts either.

Adjusted the Caster angle while we were at it to be ~8deg for added feel - esp with PAS

Never had it on the track so can't compare too much but it made it to Stoneleigh and back no dramas

The front also tips up better than before

[Roy Kemp]

Cool - compression struts are the ones that go rearwards from the TCA - does this not make them similar to your locost TCAs which go to a bracket behind the hub? Your solution looked very interesting.

When you say the front "tips up", do you mean transfers the weight over the front under braking, or am I misunderstanding?

[1u78f7ifsodyj]

Design of anti-roll bars is not simple - interesting to read up on.  Small alterations to mountings, leverage and diameter/cross sectional area (hence thinning as described on the Pistonheads post). - can make a lot of difference.  It would be interesting to hear what other people have done.

 

[Roy Kemp]

Just a bit of advice, the car really needs to lose those crappy bike shocks. There is literally no suspension travel. Going to look at Protech dampers - can anyone advise on what might be a good spring rate for a Phaeton that goes Autotesting? 

[Adrian Southgate]

i would assume that keeping a maximum contact patch at all times is going to be the desired result so super stiff is not going to be ideal on a light car. if you bin the arb its going to lean a bit too. i would think about 150 and work up ward. if you use 1.9 inch springs  and they are too soft you can always sell them on to people with road cars.

[Roy Kemp]

Just looked at the price of the Protech stuff with bump & rebound adjustment... might have to ask for an extra paper round!

[Big Vern]

Maximum contact patch under all conditions is only really possible with camber compensation. That would be a lot of work but possible on the front but impossible with a live axle on the rear.

If you are not using the front arb then you have only the springs for roll control. Thus you would have to start with something like 300lb/in and maybe work up from that. If you can make and fit some sort of adjustable front bar then you could go down to maybe 225ib/in. You can use softer springs with preload but it doesn't really help much in roll.

As for wheel frequency you will often hear banded about its not really going to apply much to autotesting since there's not much high speed straight line driving.

Personally I would want to use some sort of ARB to control roll then play with spring rates, you may find you need to change springs depending on the type of auto testing you are doing.

Grass was always about best traction since only road tyres used to be allowed. Tarmac much more about roll control.

You might even want to experiment with a rear bar on tarmac to get the rear to slide. Are you still allowed limited slip diffs?

[Roy Kemp]

Hi Vern, thanks for all the info. Yep, there's a salisbury locker in the back which makes the car inherently understeery anyway. But give her a nip of the handbrake and she'll spin all day long.

[1u78f7ifsodyj]

You need to know your current spring rates first.  If there is no suspension travel, why not?.