POWER STEERING

[Stag76]

TR7 Steering effort seems to be related to the caster angle...those with positive caster tend
to have heavier steering than those with 0 caster angle. I think this is why we get varying
results from fitting needle-roller swivel bearings...some report a big improvement, while others
say there is little or no difference.

As there is no adjustment for camber or caster, with the geometry depending on the "K" member,
suspension bushings and accuracy of mass-produced body shells, there are always differences.
Those cars with less caster angle seem to be more prone to wheel wobble.

When I fitted PAS, I made saddles that moved the sway-bar forward by 10mm, giving approx 2.5 degrees
positive caster. This made a quantum improvement in the tracking, and removed all traces
of wheel-wobble. The heavier steering was masked by the PAS...it was almost impossible
to turn the wheels when stationery without the motor running.

[Hasbeen]

You are so right about higher caster angles accentuating any wheel wobble Stag.

When I first started driving the Formula 1 Brabham Repco it had a terrible wheel wobble, shaking the whole nose of the car, particularly under brakes. It was so bad that one knowledgeable spectator could see it from 75 yards away, & asked me about it.

It was so bad the shaking was I believe, shaking the blood out of my hands, making them go numb. I was coming down Conrod straight at about 180 MILES/hour, steering one handed, the other down beside the seat, to try to get some feeling back into it.

We spent hours replacing stuff to try to stop the shaking. We finally discovered a mechanic had accidently put 6 degrees of caster on the front at the rebuild before the season. With that back at 2 degrees, all wheel wobble/shaking disappeared.

I am surprised less caster made the steering heavy. One of the effects of caster is self centring of the steering. Non power steering Toyota Camrys had steering which became very heavy as the lock was increased due to this self centring effect of caster.

Hasbeen.

[kstrutt1]

Ive had roller bearings on mine for 25 years (ford fiesta parts), when it was on standard wheels and tyres it was ok but on 195/50 15's its pretty heavy at parking speeds, above 10mph its fine. My wife used to use it every day, she won't drive it now so we are looking at a corsa based set up which can be switched off and on.

[Beans]

Only problem I have ever head with the original steering rack is
that it needs a lot of steering input (lots of 'wheel turning).
Especially on the many really sharp bends/corners in this part of the world.

That problem was solved many moons ago on 't Kreng.
I fitted a quick rack to that car with about one turn less from lock to lock.
Brilliant to drive as long as there is a hint of speed.
But with wider and softer tyres it is a real wrestle at low speeds.

So the combination of quick rack and PAS is in my opinion the ideal combination.
As others have already mentioned the original steering should be pretty light if everything is as it should be.
Fitting (E)PAS to the original steering rack seems a waste of money and time to me

[Rich K]

I agree with Beans in that if you are going to take the time and expense to fit power steering you should do it in tandem with a quicker rack to reduce the amount of steering input required. The original manual rack is a compromise with 3.9 turns lock to lock in order to make the steering effort acceptable at low speeds. Back in the day my brother had a TR7 equipped with a quick manual rack and although the steering was heavy at parking speeds, it was a far superior experience on the open road.