Steering Advice Would be Appreciated

[BITTEN]

We drove our Cobra for the first time on Friday at Wakefield and the day went really well. The engine and gearbox were wonderful.
I've put a few pics in the gallery.

The steering however lacked feeling and down the straight the car 'floated' and felt really uneasy.

Until we can have it registered it is set up as a track car as follows:
Camber 3 Deg neg
Caster 1 Deg +ve
Toe 0.8mm neg

The steering rack is a manual rack off a small Subaru and has 3 joints from the column to the rack which isnt ideal but need to clear the exhaust with a gentle curve.
18x8.5 front & 18x9 Rear wheels/Tyres

We would be interested in any expert advice.

[Merv and Sharon]

I am not sure what suspension set up you have, but these earlier threads had some settings.

Wheel alignment

Harrison: Commodore adjustable radius rods

The amount of Camber you have at the rear seems good for track use, but that could be a different matter on the road. I seem to recall that most folk on here have a good deal more caster (6-8 positive) than you have (although I don't).

That steering set up may be more of an issue.

[ICETOO]

I was going to say if you miss everything your half way there...but that would not add real value or be helpful...so i won't

[OZVENOM]

You would find it more stable with a lot more caster it loads the steering and help keep it straight. 3-4 degs would be good.
camber for the street .75 - 1 deg
For the track up to 3.5 deg.
In prefer toe in of about 2-3 mm total.
some times a cobra might need toe out to help with turn in.
good luck and enjoy your beast.
Oz.

[Tenrocca]

Steering Advice - Stay on the black stuff. Advice I should follow myself.

Love the look of your car - any indication of times?

[boxhead]

Scotty beat me too it.
I was going to say go for a degree or 2 more Caster, and up around 2mm toe in total.

I have a jag front end.
I run (from memory)
2 neg camber left wheel 2.5 right wheel (helps prevent pulling due to camber on road)
3 pos caster
2mm total toe in.

Here is a pic I snapped last Friday driving home for lunch. (allegedly)

With one hand on the wheel and one on the camera.
Aussie Mike, I love the bump steer kit for the back.

[Towmaster]

Ur running a bit low on fuel boxy....

[CHANMADD]

More caster, as above. I like 1.5 neg camber all around. A lot of guys grab the steering wheel very tightly on these cars. There is always a bit of chassis flex and one should hold the wheel lightly so that it can "dance" a bit in your hands.

[john chesnut]

I agree, more caster is the place to start. And, are all of those u joints in proper phase?

[sambo]

With 2 or 2.5 degrees neg camber and 95% of time spent on the road, would we notice much increased wear on the inside edges?

[BITTEN]

Originally Posted by john chesnut

I agree, more caster is the place to start. And, are all of those u joints in proper phase?

Thank you everyone for your comments. I understand that it is too much camber for the road but until it gets thru rego, it is a track car.
Unfortunately it may mean major surgery on the guard to get more caster so we might leave that as a last resort.

I'd like to understand more about John's question of u joint phasing?

As for track times, we were running in the engine, brakes, gearbox and checking that everything was bolted with clearance so no lap times. The current light steering situation and overall sensitivity wouldnt allow a pushed run anyway.

[Merv and Sharon]

An adjustable Z arm may allow more caster. Another thread is available on that.

[sambo]

Merv, I'm a little puzzled as to why you need to resort to those adjustable Z arms. I dialled 5-6 deg positive caster into my front end last weekend and the wheels are still closer to the front of the wheel arch than the back, when viewed side on. There's a good inch of spacer tube on the back of the top A-arm, which I could trim to lay the top arm back even further. I went from 0.5 deg to 5 deg with only about 5mm of shims on the front spacer. What I'm saying is that my kit has way more adjustment than I need and that's with a power rack where I'll end up with about 7 or 8 degrees eventually. Does it have something to do with correcting geometry for bump steer?

[Merv and Sharon]

No I did not wind up doing that Paul. After some more alignment work I got it just perfect. I was thinking that Rotax with his different geometry might need more adjustment potential.

[sambo]

Great news Merv. I'm surprised at how nicely these things drive.

[muzzza]

Rotax98

You may have a compatability issue with Subaru rack. If inboard upper / lower and rack joints are not all in sync. you will induce bump steer in almost every situation, regardless of camber caster and static toe settings.

Muzzza