Early vs Late Front Suspension and Steering

[ukkid35]

This is just my attempt to understand changes, and may well be incorrect, I'm looking for someone to confirm or deny:

Early Cerbs (up to 28/03/01)

Steering rack bar H0610 - 602mm
Track rods H0290 - 336mm
Lower suspension arm C0189/C0190
Upper wishbone C0194/C0195

Later Cerbs (29/03/01 - 20/01/02)

Steering rack bar H0740 - 665mm
Track rods H0738 - 306mm
Lower suspension arm C0189/C0190
Upper wishbone C0933/C0934

Very late Cerbs

Upper wishbone C0944/C0945


Why do I care? Because I've just bought a rack with a 665mm rack bar and I would like to make it work in my car.

Both racks are centred:

Edited by ukkid35 on Wednesday 13th March 22:14

[plasticman]

Not sure of the exact dimensions but sounds about right to me . To my knowledge the early cerbs and tuscans had the same length rack as the griff even though they had wider wishbone mounting points . The new rack you have will give less bumpsteer due to the trackrod having a similar arc to the wishbone .

[jamieduff1981]

Interesting. I've noticed some bump steer on my '99 which I wouldn't miss if it went away. What's different about the upper wishbones?

[Jhonno]

There is a bump steer kit I believe Jamie.. Raises the rack, lowers the ball joint iirc.

[Brummmie]

I have the later rack on mine, but having the pivot points further out makes the angle from the bar to the track rod end more acute and more bump steer occurs, i noticed this when i swapped, however if you mod the track rod ends so they bolt the other way up, all of the suspension/rack pivot points are are more inline, so less susceptible to geometry changes through arc.
So really you need to do both to get the benefits, mine drives like a "normal" car, before a B road was terrifying!!

[cshaw600]

What mods need to be done to position track rod ends upside down cheers

[camel_landy]

Brummmie said:

...however if you mod the track rod ends so they bolt the other way up, all of the suspension/rack pivot points are are more inline, so less susceptible to geometry changes through arc.

Hmmmm...

M

[jamieduff1981]

Jhonno said:

There is a bump steer kit I believe Jamie.. Raises the rack, lowers the ball joint iirc.

I've got it - the raised rack certainly. The front end still tucks in if you drive over an undulation on the road mid bend though. It's subtle and not really frightening on mine, but if you're paying attention (when does one not when driving a Cerb!?) it's still there.

It doesn't really bother me that much but if there's a further improvement to be made for reasonable effort/cost when it's time to rebuild mine I'll do it.

[firewallguy]

Bump steer is definitely the worst thing about my Cerb, anything other than a well surfaced A road or motorway is hard work.
My company diesel Evoque is quicker cross country :-(

[Vee8ight]

Something that has been on my mind, are these cars that suffer from bump steer, lowered or don't have stock suspension on them?
Reason why I ask is, my car is standard and an early one too, and I get hardly any bump steer, it is standard ride height and no mods to front suspension or rack etc.

[plasticman]

I measured it on my griff years ago and found it to be pretty good so did not change anything . I have not meassured it on a late T car and wonder if anybody has . Looking at it I would not have thought it would be far out.

[Luckyone]

I was confused by all the threads on bump steer a while back as I'd never noticed any. So I measured our 98 "GT" it had just the slightest amount of tow out on droop, which is meant to help turn in.
I think with all things TVR it’s quite possible it depends on what parts they had in the factory when it was made…

[ukkid35]

Recon Steering Rack from Bell Hill cost £700, now fitted and working well with no obvious leaks and no play. I am very relieved, however only time will tell.

The hydraulic fittings are very different to my old rack, even though the casting numbers are the same, strange. However the flexi lines made it far easier to fit. I fed one under and one over the coolant rail, what routing do others use?

Edited by ukkid35 on Saturday 16th March 21:03

[ukkid35]

I don't have pic with the original rack to compare side by side, but you can see the two suspension pivot points on the left, and the track rod ball joint is now further out, and not on a line drawn between the two bolts. Whereas I think with the original rack it would have been.

[ukkid35]

I wasn't aware of any bump steer before I changed the rack, now it's definitely there. I can certainly feel a little kick going over bumps.

The worst thing is that the car was very nervous on the (slightly bumpy) main straight at the 'Ring, and I definitely don't remember it feeling like that in October with the old rack. I've made no other changes to suspension or steering.

At least the car was ready for the Spa/Ring trip, but it looks like I need to find short rack bar.

[GT6k]

You could of course just cut the end off to match the original length

[ukkid35]

GT6k said:

You could of course just cut the end off to match the original length

And drill and tap the ends, without marking the section where the hydraulic seals operate. Too much to go wrong for me.

[pmessling]

I brought the longer ones by mistake whilst doing my chassis work last year, but needed the shorter so cut them down on the car and threaded the remainder of the bar.

[Brummmie]

Have you flipped the track rod ends, and raised the rack? You need to do this.

[Basil Brush]

I swapped my early Tuscan over to the wider rack, but I also swapped the top wishbones for the later set up.

Flipping the rods on mine gave too much bump toe out so I've swapped back to Rover SD1 TREs. Measuring the bump steer, I ended up lifting the rack on 8mm spacers which gave me slight (c.1mm) toe out at 1 inch bump.