RAM Cobra IRS view

[Antony]

I have just been in contact with Realm engineering and they are going to send me some information on the Ram SC, what I would like to see is how the chassis and the rear end has been fabricated, so if someone has a picture(s) of this it would be much appreciated!

I am intending on using an alloy Ford Thunderbird IRS diffhead that I have from my last project, and fabricating double wishbones and running the T/Bird alloy uprights and CV units, it may not be that major to alter the chassis for the head, but as the Jaguar has the axle as the top arm, it will be interesting to see where the chassis goes to fit and make a top wishbone, I have a computer program to work out all the roll centres etc.

Having said all that as he stumbles blindly, what do the race guys here use for the rear ends?
My first car had an E type rear end with konis etc and it was wishy washy on fast turns, but I am sure a Jag rear end is good for road use!

[russell_ram]

Ant,

I have a load of build pics at home, I'll dig some out later. There is plenty of chassis around the Jag diff on a RAM chassis - modifying it to take another IRS should not prove too tricky.

Having said that, there is nothing wrong with the Jag rear end - except maybe the torsional stiffness of the lower arm, but then probably not an issue unless at 11/10's.

Later Aston Martin DB7 (which uses an XJS rear end complete) lower arms have the triangulation to the inner pivot discussed elsewhere as standard, giving slightly improved fore/aft stiffness - a useful mod to older units especially if they've been narrowed by cutting and shutting at the inner end.

Your Jag handling issues probably have more to do with the fact that the whole rear end is rubber mounted in an E-type than any inherent fault with the Jag IRS as we use it in Cobra replicas.

If you're drag or circuit racing then probably what you actually want, of course, is a decently located solid axle!!!

Russ

[Antony]

Russ,

That would be great to see some picts!

On my first car the diffhead was solid in the chassis, and I remember the whole wheel going backwards and forwards on take off, something to do with the radius arms having a tie rod on one end and urethane bush on the other. The Jaguar factory radius arms had to much compliance. Having said that I was a bit green back then on suspension issues!

I am into circuit racing and road use only, not drag racing, so am out for handling, I like the Jaguar diff which is very strong and very good for most applications. As I have a T/bird alloy head with Eaton Carbon fibre positraction, all new parts I would like to use it but I dont want to reinvent the wheel, if you guys are having good success with the Ram on the Jaguar setup, then I may just sell off the Ford diff.