Hi all, looking for guidance please,

I own a 1980 XJS 5,3 V12. (Pre HE)

The car has had a nut and bolt restoration, ( everything is new, bushes to brake lines, engine - Fuel tank. you get the idea…)

I have only just started to drive the car, and find that the steering is very light, think floaty, not very precise and in my opinion, down right dangerous. I will not drive the car above 50mph.

I have had, steering geometry checked and confirm it is within manufacturer tolerance.

I have noticed that the wheels and tyres fitted are not from the original car, in fact they are from a 87 HE , 235, 60 15,I inflated these to 30PSI.

Could the fact i have a pre HE car on HE wheels and pressures be the reason for the woefull steering?

The rack, control valve ( also seen this described as a tower ) and all bushes are also brand new, (the rack is fully reconditioned by experts, as is the pump, the steering rack slipper is correctly adjusted).

Can I add a sports pack type control valve to my existing rack to change the dynamics and feel? if so where do I get one of these ?

Can I add an HE steering rack control valve to my rack, again hoping for better control, and less floaty feeling.

Or can I add a steering rack pressure adjustable pressure reducing valve to my existing set up to lower the pressure and therefore floaty rack feel ?

Or should I swap back to original period wheels and tyres ?

As point of interest, the car has also has brand new top and bottom ball joints, these are a little stiff, but are non adjustable, though I would mention it incase anybody else found a problem with their steering after install of new ball joints,

Or, and this is a final or, have I simply realised the Pre HE steering rack which was designed for different size and profile wheels on post HE wheels and tyres is by default, horrible???

 

How did it drive before the restoration? I don't think the wheels/tires would make much difference. I have read there is a bracket at steering rack that is sometimes forgotten and could cause additional slop, I have no experience with this however.

 

Floaty before the restoration im afraid,

 

The factory steering rack bushings are rubber, and steering load can cause them to deflect in the steering direction creating some lag and vagueness. Replacing those with polyurethane bushes makes a huge improvement in steering feel. See if changing to poly makes a difference for you.

 

Thanks Mac, Poly bushed all round.

 

Are you 100% sure the rack bushes are poly and in fact have been fitted and all three mounting bolts are in place (two on the rack tower end, one on the other end)?

Floaty steering can be induced by the rack mountings, the stub axle being loose, loose unadjusted wheel bearings, or by the wishbone mountings and rubbers. Also the lower column unit may well be faulty, this piece:
https://parts.jaguarlandroverclassic.../brand/jaguar/
It has an integral lower UJ-type affair and a replaceable upper UJ. This is a likely candidate and worth removing and carefully checking.

I suppose it is just possible the front subframe is not mounted securely too.
Get the car on a 4 post lift with swivel plates under the front tyres and engine off with someone on the steering wheel, see where the movement is.

 

Check the tire rating max psi. Even back in '87 the recommendation was 36 psi for that size tire. Tires today have a max of 44 psi with some up to 51. That 30 psi seems low.

 

We swap wheels back and forth all the time. It’s not wheels.
The Jaguar is over boosted in the power steering department. Racers use a modulator valve to decrease the amount of steering boost.
Rob Beere Racing ( in England) used to be my source for full kits to just install. But rumor had it they are no longer in business.
You might check with BILL TERRY JAGUAR and see if he has another source. It’s not that hard to make your own valve.

Since it’s a basic GM power steering pump, you might look for a bigger diameter pump pulley and see if that reduces the over boosted feeling.

 

If you don't find any significant play in the steering system, you might check that the rear suspension is set up properly. Looseness in the rear subframe mounts, radius arms, shocks etc can lead to floaty steering.

HTH, Dave