Help in understanding Tasmin suspension, please.

[calgarytrainnut]

Hi,

I was asking the following over on the Wedge forum but figured some of you would have experience of this as well. Rear of my car is stock and may have had some interesting servicing of the alignment in its past. I'm in Western Canada so a TVR is a bit of strange critter to service.

Looking to the collective wisdom again as I burned out my rear tires in only 4,000 miles. Old tires that came with the car ('86 US spec 280i) showed no abnormal wear pattern but I hardly put any mileage on those before replacing last year.

So 2 new tires on the rear and had the shop run the car up on the alignment rack. Oy! Specs are in the computer at the corner shop but the tech has no idea how to adjust the rear; thinks it's all fixed (yes, I know better hence my questions below). I also have the alignment specs that are posted on PH. I've seen the pretty picture of the bad news on the alignment computer and this is the info from the printout:

Lt rear camber -2.6 deg, 0.55" toe
Rt rear camber -1.8 deg, 0.00" toe

Lt frt caster 5.4 deg, camber -0.9 deg, toe 0.05"
Rt frt castor 4.6 deg, camber -0.7 deg, toe -0.10"

Someone in the car's past has set it up to dogleg down the road except the right rear is pushing straight ahead. Bye, bye rubber.

Tires have changed from 205 to 195 as that's what's available over here. They are 14's.

On to the nitty gritty. Starting at the rear, castor first. Shims at the discs; 0.25 deg per 0.020" shim (approx). That's easy. The trailing arm shims. What are they (as I think mine are gone)? How thick is each? How far will each shim push the toe out; there must be a ratio of washer x" moves the toe y"? As the castor shims are always added in first how does that change the toe? What is the diameter of the bolt at the front of the trailing arm that goes through the shims?

Cheers!

Michael

[77racing]

Hi Micheal,

Not many people coming on this forum any more I,m afraid. NTEL on here would be the man to help but he has retired from racing this year. Try sending him a PM. If I was you I would also post up on the classic forum. Good luck cracking car you have there and rare as you say.

[calgarytrainnut]

Thanks. I also swung by one of the local shops at noon today, who specialize in British, are knowledgeable about Jag rear ends, and set up race and rally suspensions. And I'd buy the read end shims and nuts from him anyways. He took one look and went oh. Car is heading to his shop on Monday for a few days. It's only money and I have a fence to build, a timing belt to replace on the daughter's Golf, etc. which is probably a better use of my time than to spend a day stringing the car 20 times as I adjust everything. If someone had known the ratios I would have had a go this weekend with a lot less stringing. But the snow possibly starts flying in about 6 weeks around here so hire a professional sounds prudent so I can rip out into the mountains a couple more times without worries. The Icefields Parkway is a mere 180 km from my back door.

Cheers!

Michael

[Graham]

Hi, My race tasmin had the trailing arm suspension but we modified it so the trailing arms and the link bars were both adjustable so shimming was not really used other than for a bit of camber.

Our settings would be a bit extreem for road use too.

we also modified the back end to coil over suspension.


one thing though keep an eye on the hub nuts as they are not handed so one can come undone



G

[calgarytrainnut]

Thanks Graham. I did a lot of reading up on here to figure out the little beast. She's in nice shape overall. Those nuts were one of the first things I found out about. Check every time the rear wheels are off. And while your settings for racing are a tad extreme for the street, you know what each tweek does. Car will be good in a week. Works out I was burning 100.00 a day just in rubber when on a road trip. And no, I was not getting pitched all over the road.