Handling can be a little scary

[thegman]

Hi Chaps

I have had my S4 Elan for a several months now and in general the handling is very impressive in terms of over/under steer balance. However the car has a tendency to bump steer and a reluctance to re-centre when pressing on. The car accelerates and brakes true but on encountering any change in road surface it tends to want to change direction. This means lots of steering input to correct and can be unnerving!

Car was rebuilt not long ago on a Spyder chassis and has adjustable suspension. No idea it the geo was setup professionally.Its sitting on 15inch wheels. No play in steering so no reason to think it is the rack.

Any ideas where should I start?

Thanks

[Certified Lotus]

I don't know anything about spider chassis, but the original chassis had shims below the steering rack mounts to off-set the bump steer problem. Some where on this site is a detailed explanation on how to measure for it.

[theelanman]

those are big wheels for an Elan.......
they were originally on 13"...and if your a 2 seat elan - 155 wide tyres........
I think if your at 15" then you've lost all tolerance of sidewall deflection........
Id try some 13 or 14" rims if someone can lend you a set just to see.......

[Elan45]

Ah, but it is the rack! It has to be the rack's vertical location. Do you have the factory shop manual? There are a few pages devoted to bump steer and rack height. My S3-SS Elan had bump steer on its old original frame, but when corrosion forced me to change it 30 years ago, I spent a good bit of time making sure the rack height was correct to reduce bump steer to a minimum and I've not been bothered by it since.

Roger

[nigelrbfurness]

I would have a play with the tyre pressures first before you start the process of checking the steering geometry. Given that you have none-standard tyre sizes and adjustable suspension, there are a lot of variables to play with. Is the suspension equally hard side to side, for example? I would start from scratch with the damper adjustment, setting them mid-way between fully hard and fully soft, then make sure tyre pressures are equal across the front tyres - start with around 22lbs/sq in (standard is around 18-19 on 155r13) and take it out for a drive on your favourite bumpy road, gradually reducing the tyre pressures and noting the results. When you find the best tyre pressure, start on the dampers - one click harder each side and see if it gets worse or better. I'd bet you that softer dampers will give you better results.

I've had far more Elans with bump-steer problems attributable to old or just bad tyres and incorrect pressures than rack height setting. If you can't dial out the bump-steer completely that way then you will have to look at the steering geometry.

JMO.

[reb53]

As this is a new car to you, ( I'm assuming you haven't owned an Elan before), I'm not 100% sure it isn't behaving as Elans do.
They do tend to be nervous on poor surfaces and need, as they say in horsey circles, a "loose rein".

Before embarking on a long , and no doubt expensive, journey of experimentation with all the components of your car that affect handling, why not find a long term owner close to you who could take it for a drive ?

Ralph.