TR3 Rack & Pinion "vague" steering

[Philippe_TR3a]

Bonjour at All,

 

I have made a Rack & Pinion change on my TR3A after a chassis to body complete restauration. It is a Moss brand new steering (coming from a TR7 I think). All the bushes, ball joints, etc... are new.

 

The steering is very light now (too much?) and it is OK in the straights and in manoeuvres, but I found the steering "vague" at the start of the corners and I feel uncomfortable with the car.

 

Please note I have probably a little bit too much toe in.

 

Have you encountered such problem and is there any solution about that?

 

Thanx in advance

[stuart]

Bonjour at All,

 

I have made a Rack & Pinion change on my TR3A after a chassis to body complete restauration. It is a Moss brand new steering (coming from a TR7 I think). All the bushes, ball joints, etc... are new.

 

The steering is very light now (too much?) and it is OK in the straights and in manoeuvres, but I found the steering "vague" at the start of the corners and I feel uncomfortable with the car.

 

Please note I have probably a little bit too much toe in.

 

Have you encountered such problem and is there any solution about that?

 

Thanx in advance

 

You do need to ensure that the steering arms are as close to the disc back plate as possible. Some of the kits say swap them side for side and use different spacers to get them as far out as possible and then alter the track rod lengths to suit. This reduces bump steer. Get your tracking correct and check your tyre pressures aren't too high as well.

Stuart.

[Kevin in CT]

Hi Philippe- As Stuart said, proximity of the outer ball joints to the brake disks is v. important. In fact, when I installed the Revington TR R&P kit on mine, they advised leaving the brake rotor 'backing plate' off, as it interferes with the proper positioning. How much toe-in are you running? Best, Kevin

[Philippe_TR3a]

Bonjour to all,

 

Thanx for your comments. I will try to reduce the toe-in and reduce also the front tyre pressure (2.0 bars for the moment).

 

Regarding the position of the steering arms, they are very close to the disks (and I have removed the disk backing plates).

 

Philippe

[stuart]

Bonjour to all,

 

Thanx for your comments. I will try to reduce the toe-in and reduce also the front tyre pressure (2.0 bars for the moment).

 

Regarding the position of the steering arms, they are very close to the disks (and I have removed the disk backing plates).

 

Philippe

 

2bar is way too high no wonder its difficult to handle! Try around 24PSI or its metric equivalent

Stuart.

[Ian Vincent]

I'm not being a smart**se here Stuart but 2 bar is only 29 psi. Would that much be enough to ruin the handling?

 

I have a vested interest here because I will be fitting a R & P set up and I have been told to watch out for bump steer.

 

Rgds Ian

[Steve Knight]

Could be nothing to do with the rack. Play in the wheel bearings cause a vague feeling. Too much toe in or castor (or high tyre pressures) gives more instant turn-in - could be described as vague. Is it just vague compared with the OE heavy set up. Dial in some toe out - that will stiffen up the steering !! Girls usually like a Fiat girly button to give lighter ( un-feeling ) steering - its all they ever want. A steering geometry expert may well see that the R/Pinion does not work the same way as worm and roller( is it ? ) Many of these accessories and shinny add-ons are not engineered to replace the original; track & steering arm height and length, plus overall geometry may only work ( properly ) with the original steering box. Not to say its unsafe, it just doesn't have quite the same feel. How long did it take manufactures to get power assistance to feel right ?

[stuart]

I'm not being a smart**se here Stuart but 2 bar is only 29 psi. Would that much be enough to ruin the handling?

 

I have a vested interest here because I will be fitting a R & P set up and I have been told to watch out for bump steer.

 

Rgds Ian

 

What I said about getting the steering arms out to the maximum will make a world of difference to "Bump steer" for a start and too high a pressure even by 5 psi also makes quite a difference on the skinnier tyres we run compared to modern wide low profile rubber. I havent driven a Moss kit set up so I dont know what they handle like but the TR Bitz one is excellent. I believe that uses a modified TR7 rack whereas the Moss one uses a modified Mini rack.

Stuart.

[BrianC]

I'm not being a smart**se here Stuart but 2 bar is only 29 psi. Would that much be enough to ruin the handling?

 

29 psi at the front certainly ruins the handling on a TR3A with original steering setup, so I can't imagine it would be too clever with R&P either.

[Philippe_TR3a]

Bonjour to All

 

What I can add is that, with the previous steering (original one), when I lifted the car, the wheels remained parallel.

With the new steering, the wheels, when lifted, are open of almost 1° per side... but I followed the mounting instructions!

 

Someone told me about a antiroll bar, clever idea?

[Kiwifrog]

Bonjour to all,

 

Thanx for your comments. I will try to reduce the toe-in and reduce also the front tyre pressure (2.0 bars for the moment).

 

Regarding the position of the steering arms, they are very close to the disks (and I have removed the disk backing plates).

 

Philippe

 

Phillipe

Recommended tyre pressure in the Front is 1.5 bar for the front tyres and 1.7 for the rears. I used to run 1.5 All round on my TR4 and found the steering perfect that is rack and pinion as well. At 2 bar your tyres at the front are very over inflated

 

Cheers

 

Alan

[tr3aproj]

Bonjour to All

 

What I can add is that, with the previous steering (original one), when I lifted the car, the wheels remained parallel.

With the new steering, the wheels, when lifted, are open of almost 1° per side... but I followed the mounting instructions!

 

Someone told me about a antiroll bar, clever idea?

 

It appears after reviewing your album that the tie rod lever is not close enough to the brake disc to eliminate bump steer. I will try to add a photo of my front suspension with the Revington TR modification.

Regards,

Robert

[Philippe_TR3a]

How to transfigurate a car (a TR3 in that case)?

 

I reduced the pressure of the front tires from 2.0 bars to 1.7 bars and the steering was transfigurated!

 

That's remember me a discussion with a friend involved in F1 where he told me that the tire "suspension" was 50 % of the whole suspension effect.

 

Robert, my rod levers are at the same location that yours (spendid car!).

 

Thanx to all

[jean]

Philippe, I have the same steering conversion as Robert on my TR3A ( Revington ) Must say on my car the steering arms are even closer to the disks, about 5mm.

I don't know if you have changed the lower trunions from the original 0 deg to 3 deg. As far as I noticed, in addition to toe in, castor angle does also highly improve steering stability.

You might notice that Robert's front suspension is fully modified to late TR4/TR6 specifications. Rack and pinion alone might produce a lighter steering action, but will not improve handling

[tr3aproj]

Philippe, I have the same steering conversion as Robert on my TR3A ( Revington ) Must say on my car the steering arms are even closer to the disks, about 5mm.

I don't know if you have changed the lower trunions from the original 0 deg to 3 deg. As far as I noticed, in addition to toe in, castor angle does also highly improve steering stability.

You might notice that Robert's front suspension is fully modified to late TR4/TR6 specifications. Rack and pinion alone might produce a lighter steering action, but will not improve handling

 

 

The TR3 suspension was originally designed for bias ply tires which function best with +1.0 degree of camber. Radial tires function better with -1.0 to -1.5 degrees of camber. Since I switched to radial tires for the restoration I decided to go ahead with the Revington modification that changes the camber to negative, provides 3 degrees of castor and reduces or eliminates bump steer. I struggle with safety vs originality with the restoration. I am keeping the original steering box to maintain self cancelling turn signals and horn. However the modifications to the suspension should eliminate much of the quirkiness of the steering. I am debating on whether to switch to a dual braking system with vacuum assist for safety or maintain the original brake system. At this point I am thinking to stay with the original braking system. If anyone has the dual system I would be interested in your impressions.

Robert

[TR 2100]

If anyone has the dual system I would be interested in your impressions.

Robert

 

Robert,

 

I have the dual system on my 4 but not having driven a 3 for some time,

I can't really give a worthwhile comparison.

General (expert) opinion is that TR3 and TR4 brakes don't need a servo

if they are in good condition.

 

For dual braking, the pedal pressure depends on the size of the master

cylinders. They need to be quite small diameter, then the braking effort

is similar to the standard set-up. Again, no servo is needed, which is

fine with me 'cos I think servos are messy.

 

If you wish, PM me with your email address and I'll send some photos of

my setup. It's a neat setup and even uses the TR3 style combined fluid

reservoir.

 

AlanR

[jean]

If you can lay your hand on a TR6 pedal box you might consider converting it to a dual TR6 braking/clutch system which will also provide you servo power

I have seen it on several Sidesceen cars and I would consider it in case of a restoration.