Hi, I've been looking into IRS set-ups there isn't allot of info out there so how have forum builders solve IRS with chain driven diffs.

I am planing a chain drive diff arrangement and as these are off set to the off side of the car most IRS setup have small diff area and longer wishbones I need a larger diff area and smaller bottom bone!

So is there any problems in following IRS plans but having the bottom rear bone made shorter so the rear "diff area" is now a little bigger is make room for the offset chain diff?? the top bone is ok so will there be any affects?

Thanks all

Changing the length of only one arm will wreck the dynamic setup. If everything is changed by the same amount, and i mean percentage here, everything should stay the same.
I'm sure someone witha greater knowledge of this than me will be along shortly though

Have you considered redesigning the lower bone to allow clearance for the diff but keeping the length the same?
As said above changing the lenght of one bone will seriously alter the characteristics, and I think you will also find that altering both in the same ratio will will be almost as bad.
If you really want to go down the self design route, (and I'd be the last to discourage you, it's what I'm doing) I'd suggest you read Competition Car Suspension by Alan Stanniforth and How to Build and Modify Sportscar and Kit Car Suspension and Brakes by Des Hammill.

Have Fun

Mick

I would say the same as above. Two great books and a god point. Its difficult. Although i think the best way is to get good with gad and draw it out then test each design.

How offset will the diff actually be??

Have you mocked the setup up yet to see what is what? This sounds like one of those problems that I always fret about at the "thinking" stage, that disappears when you actually start to lay bits out??

The comment about chaning them by the same percentage could be misleading as you will need also to change the hieght of the uprights, the verticle spacing between the uppper and lower wishbone pivots on the chasis and the distance from the centre line. Having done all of that the roll centre will then stay in the same position.

Sorry. Meant to say you have to change everything to make it work. Good point well made there.

Is it raelly all that difficult?

I have decided to make my own IRS and front. Read a lot.

This is what I think:
There are things you must try to get controlled.

Bumpsteer at front
Place of your static roll-centre
stay with ET 20-45 by using the cortina/taunus uprights at front.
try to get some camber 0.5 degr at 1 inch compresion.
As non of the kit-carmanufactures have the same suspension and set-up. I don't believe it will result in such terrible driving behavior.

As the wheeltravel is about 3-4 inches i don't think that a shorter or longer upper or lower wishbone will result in bad grip etc.

What think the seniors among us?