LSD and Radial Tyres - Experiences

[Oneball]

I'm at a bit of a loss, since fitting Yoko A008R to my car to do some hillclimbs (I usually run Dunlop CR65 X-plies in historic racing) my car has become uncontrollable under power in a straight line.

On the road I would describe it as downright dangerous. I've been through everything and keep coming back to it being the nature of the diff.

I've got an Minispares Evo Race LSD 35/90 ramps, does anyone have experience running one of these on radial tyres either on the hills or road, if so have you got any stability issues?

Video here from Shelsley, you can see how much it moves around on the final straight.

https://photos.smugmug.com/photos/i-VXV ... b-1280.mp4

Thanks Tim

[Spider]

I've no experience with that particular diff, however long ago, I did run a Sailsburry for a short time.

Looking at the Video, it really is like a mad women !

I know you've looked at everything, but the thing here after seeing the Vid that leaps out at me is the Front End Toe Angles. They maybe set where you've always had them, but it may need a little less or even some Toe In.

[Oneball]

I've no experience with that particular diff, however long ago, I did run a Sailsburry for a short time.

Looking at the Video, it really is like a mad women !

I know you've looked at everything, but the thing here after seeing the Vid that leaps out at me is the Front End Toe Angles. They maybe set where you've always had them, but it may need a little less or even some Toe In.

To be honest, I've not tried toe in, messed with camber (0 to -2.5), caster (4 to 7.5), ride heights (absolute minimum to almost stock), damper settings, fixed play in a rose joint, new dampers (one was sticking a bit in rebound), removed the ARB, tyre pressures from 24 to 42 and changed to softer front cones, but not tried any toe in. Good call Spider.

[mk1]

I use this diff & have used it with A008's, A0032's & Avons.

I have never experienced the sort of issue you describe & use suspension settings similar to those you describe. Have you experienced this more than once? Could it be down to track / road conditions?

[Oneball]

Thanks Mark, I first experienced it a Shelsley last month, but when tested on the road it does it all the time with the Yokos on. With crossplies it's noticeable but not an issue. The thing is I can't work out if it's always been there and I've just not really noticed it or if it's new. To put it into perspective at full throttle in second on a straight bit of road it'll get a wheel across the centreline before I've corrected it.

I've been through everything, (one radius arm nut did up by 1/6 turn, not sure if that'll make a difference), ride heights and corner weights spot on, geo all set, with a touch of toe in on the front. I'm at Prescott on Saturday so will see how it goes.

Apart from an engine rebuild and the Yokos, the only thing I've changed from last year is a new steering rack, the old one was a Minispares quick rack and this one is a quick rack from Moss, maybe that's the issue but a quick measure showed them to be similar. If it's any other car I'd have bunged another rack in to see, but these are such a !!!!

[wantafaster1]

Rims aren't wide enough.

[mk1]

Agreed, they are a pain to do.

If I was you, I think I'd give it a while & see if you get used to it / it settles down.

It may just be that you are getting more grip with the radials so you notice it spinning up more than with the CR65's. I have had issues like this before & it usually transpires that it is me "overthinking" the issue.

[Oneball]

I don’t think a wider rim would make a difference.

Thanks Mark, will see what it’s like at the weekend and take it from there.

Tim

[GraemeC]

with a touch of toe in on the front.

That could be your problem. Toe out on the front and toe in on the rear (or certainly no more than parallel if you like it lively).

Also, what shocks?

[Oneball]

with a touch of toe in on the front.

That could be your problem. Toe out on the front and toe in on the rear (or certainly no more than parallel if you like it lively).

Also, what shocks?

The toe in was to stabilise it. I usually use a touch of toe out on the front but having a little toe in helped.

Anyway, went for a drive this afternoon and confirmed it’s not right so changed the rack for a standard mk2 one. 4 hours for a rack change isn’t bad. It’s made it so much better you can use full throttle on the road without fear of a head on accident. Whether that’s due to a slightly different inner joint position on the Moss quick rack or just the extra leverage provided by the standard one I don’t know. Happy now.

Thanks for the suggestions

Tim

[Spider]

The toe in was to stabilise it. I usually use a touch of toe out on the front but having a little toe in helped.

Anyway, went for a drive this afternoon and confirmed it’s not right so changed the rack for a standard mk2 one. 4 hours for a rack change isn’t bad. It’s made it so much better you can use full throttle on the road without fear of a head on accident. Whether that’s due to a slightly different inner joint position on the Moss quick rack or just the extra leverage provided by the standard one I don’t know. Happy now.

Thanks for the suggestions

Tim

Tim, do you know what steering arms are fitted (MKI or MKII) and are the the same ones on the left and right sides?

It may also be worth checking them as they can get bent.

It maybe bump-steer.

[Oneball]

They’re the mk2 ones. I fitted them 10 years ago but double checked last week in case I got it wrong. They don’t appear bent. So fingers crossed.

It probably is bump steer, I’ve not actually taken a cone out and measured, it’s more that others don’t seem to have an issue

[Catmint]

Just a thought - what are the internal splines like in the end of the steering column - if they are worn then it can cause random movement on the road even if the bolt is tight - found this out the hard way, it got very entertaining on the M1 once

[IanD1965]

Had this a long time ago and it was the steering rack u bolts that were loose. Worth a look?

[MiNiKiN]

Late reply (make it a zombie thread )
It too could be that the steering rack was a bit stiff around the centre (straight) position - this would make you easliy over-correct on the steering wheel, resulting in this wiggly drive line.

[Oneball]

I chased my tail for ages, completely screwed the set up, had various trips into the scenery and have binned the Yokos and put everything back to how it was, including a new quick rack. Everything was good at Brands, admittedly on Dunlops, but if I was using radials again I’d go with Avons.