Steering Silentblocs

[Charlie D]

Hello All,

Just taken my 3a around the block for the first time in 40 odd years. Nice feeling of achievement, but I’d forgotten how difficult the car was to drive. Main problem is that the steering seems to have a mind of it’s own. I’ve read dozens of pages of advice in the archives of the forum and I’m sure that I’ll get it sorted eventually.

However there is one thing that intrigues me.

I know that both Moss and Revington do their own version of the Silentbloc bushes at the end of the central arm (drag link), but my query concerns the original bushes.

In the Silentbloc the pin does not move freely inside the outer part. It is bonded to it with the rubber. This means (I think) that if you hold the outer part solid and twist the pin it will return, when you let it go, to the original place. (I see it a bit like Indespension rubber suspension units used on small trailers as springs.)

Does this not mean that, as long as the bushes have been tightened up with the front wheels in the straight-ahead position, they have some effect on the “Self centering” of the steering? (I believe that the 2/3/3a has no caster angle so there is no self-centering in the normal sense of the word.)

If that is so then if the bushes were tightened up with the wheels on full lock the spring action of the Silentbloc would try to pull the steering over to that side.

Was the Silentbloc intended to offer some degree of self-centering, an if so the “Improved “ versions would not have the same ability.

How do people with the improved bushes find self centering (If indeed it exists)?

Charlie.

[Lebro]

I agree with your analysis of how the original bushes work, & yes they should be setup in the straight ahead position.

There will always be a fair degree of self centering even with the new non rubber bushes & zero castor angle.

However increasing the castor angle will increase the self centering effect.

I have changed to the stainless steel pin in a PTFE bush type, & together with a number of other changes I now find my steering very direct.

The only remaining issues is the heavyness at low speed.

Bob.

 

[RogerH]

1 minute ago, Lebro said:

I agree with your analysis of how the original bushes work, & yes they should be setup in the straight ahead position.

There will always be a fair degree of self centering even with the new non rubber bushes & zero castor angle.

However increasing the castor angle will increase the self centering effect.

I have changed to the stainless steel pin in a PTFE bush type, & together with a number of other changes I now find my steering very direct.

The only remaining issues is the heavyness at low speed.

Bob.

 

Hi Bob,

  don;t go slow.

 

Roger

[Lebro]

[Hamish]

20 minutes ago, RogerH said:

Hi Bob,

  don;t go slow.

 

Roger

Works for me 

[RogerH]

[Hamish]

1 minute ago, RogerH said:

Roger made me do it officer !!

[John McCormack]

14 hours ago, Lebro said:

I agree with your analysis of how the original bushes work, & yes they should be setup in the straight ahead position.

There will always be a fair degree of self centering even with the new non rubber bushes & zero castor angle.

However increasing the castor angle will increase the self centering effect.

I have changed to the stainless steel pin in a PTFE bush type, & together with a number of other changes I now find my steering very direct.

The only remaining issues is the heavyness at low speed.

Bob.

 

I have the Revington spring loaded top and bushes on my daily driver TR2. My steering is very good. A bit heavy at parking speed but nothing untoward, I have 165 tyres which helps steering at low speed.

My long door TR2 steering has the Revington box top but with silentbloc bushes. 165 tyes on the steel wheels. The steering appears noticeably lighter than on the other TR2 but I need to get it on the road more to really know. 

[Drewmotty]

Early cars in particular are very sensitive to steering alignment and tend to wander a lot if the tracking is toe out or close to zero. 

Whats it like at higher speeds on a straight road?

Edited July 5, 2019 by Drewmotty

[John McCormack]

29 minutes ago, Drewmotty said:

Early cars in particular are very sensitive to steering alignment and tend to wander a lot if the tracking is toe out or close to zero. 

Whats it like at higher speeds on a straight road?

You are right on the toe out and wander. I was driving the car I'm restoring and noticed the steering being a bit vague but light. When we did the wheel alignment it had 1/8"toe out. It now has 1/32"toe in. I haven't driven it yet after the alignment but the mechanic tells me the steering is very good.

The next dry day here is next Tuesday so I will drive it home then, about 20kms including a short section at 80km/h,  and report back.

[Charlie D]

Thanks all for the comments.

I haven’t tried the car at more than 50 at the moment. I feel there is more that I need to do to get it feeling a bit better first. The Revington top plate arrives today so I’ll see what happens when I fit that. I've heard both good and bad reports...

I’ve already changed the idler as the one I had originally fitted had a bit of play in it. The replacement seems almost as good as new as far as wear is concerned BUT when I fitted it I was on full lock to the left and when I took it for a test drive I “Thought” that it pulled to the left, hence my question about tightening up in the straight ahead position.

I will also check the toe in. I used the method of measuring from rod end to rod end (7 point something inches.)  I remember Don Elliot seemed to believe in that method. I’ve never really understood how you can measure toe in with a bit of string between the inside of the wheels. Whenever I’ve tried it the engine seems to get in the way (Although that may well be a subject for another thread…)

Drew said: “Early cars in particular are very sensitive to steering alignment”

Mine is a ’59 so not early by a long way. Any idea what was different with the front suspension between early and late cars?

Charlie

[Lebro]

I have a home made version of the Revingtons sprung loaded adjustment pin, the advantage of that is when driving in a straight line it should eliminate all play in the worm / peg part of the steering box. when cornering the load is all on one side on the "peg" so the modification has no effect. I also have 165 profile tyres on 4½" rims.

Bob.

[Drewmotty]

By early I meant sidescreen/worm and peg cars. 

The Revington top plate can work wonders if the worm is well worn in the straight ahead position but won’t make much difference if the worm is ok. It won’t make it worse so worth a try. 

I did a rough set of the tracking by cutting a  stick to just fit between the sidewalls at the front of the wheel and checking it against the distance at the rear of the front tyres at the same height to give a minimal clearance. I thought it was a rough set to get me to the alignment shop but possibly by luck it turned out to not require further adjustment. 

[Charlie D]

Thanks for that Drew. I used the method you mentioned and found that with a stick just fitting at the front of the wheels there was no way it would fit at the back. I know it’s no way accurate, but I’m guessing it was more than ¼ inch toe OUT !

Spent half an hour to get it to where it was definitely toeing in by a bit (made sure that the ball joint to ball joint distance was the same on both sides) and took it for a drive.

It’s a different car….

Amazing what a simple adjustment can make.

I actually feel safe in it now.

 

I’ll fit the Revington top plate in a few days as there is some play in the steering (I did not expect the tracking to make any difference there.)

Bob,

I’ve read before that you made your own top plate. Now seeing the real thing I realize it would not be that difficult. I admire your trust in your engineering. I just felt that I’d pay the money for peace of mind.

I’ll also re-do the Silentbloc that I tightened up in the full lock position. Looking close at it I can see why I put it on full lock. It’s not easy to get a spanner to it in the straight ahead position. I would not be surprised if most people who replace them do them on full lock.(Of course, with the modified versions it would not make a difference.)

Thanks again everyone for all the help.

 

Charlie.