Solid Axle vs IRS Rear Suspension

[tommurphy73]

I have been toying with changing my solid axle rear suspension on my mark2 escort to IRS as it is currently undergoing a full restoration. I want to do this withour cutting into the car too much. The car will have rear turrets when finished. It would be very difficult to fit wishbones as I think this would reqire a lot of cutting for clearance. I was thinking of fitting struts from a front wheel drive car and a differential from a rear wheel drive car like a Ford Sierra or a BMW. The struts would mount onto the car using a long bottom track control arm and one link going forward to the existing leaf spring mount. The would be one further link to the steering arm which would be in parralel with the track control arm. The advantage of this setup is it is fully independant and could be adjusted for toe in an camber. It is easy to fit different rate coil springs to change the ride height and handling. It should be much more comfortable and also give better handling. By the way the car will be used on the road and possibly for one or two track days. Has anyone done anything like this or have any ideas on the pros or cons of such a setup.
The attached image is from another forum but gives an idea of the type of setup I am talking about.




Regards
Tom

[Al Weyman]

Can't get on the site Tom but personally speaking it seems a hell of a lot of work for what may be little gain, dial a bit of toe in and camber on the existing axle may be a better way to go as i have never heard of RWD Escorts being anything but very competitive in the handling department. As a matter of interest and dont laugh, years ago i built a mini front subrame into a Hillman Imp HotRod with a MiniFord engine/gearbox set up a midships and talk about understeer, all the way into the first iron post on the first corner at the first race at Harringay. :-)

[terence]

Originally Posted by tommurphy73

I have been toying with changing my solid axle rear suspension on my mark2 escort to IRS as it is currently undergoing a full restoration. I want to do this withour cutting into the car too much. The car will have rear turrets when finished. It would be very difficult to fit wishbones as I think this would reqire a lot of cutting for clearance. I was thinking of fitting struts from a front wheel drive car and a differential from a rear wheel drive car like a Ford Sierra or a BMW. The struts would mount onto the car using a long bottom track control arm and one link going forward to the existing leaf spring mount. The would be one further link to the steering arm which would be in parralel with the track control arm. The advantage of this setup is it is fully independant and could be adjusted for toe in an camber. It is easy to fit different rate coil springs to change the ride height and handling. It should be much more comfortable and also give better handling. By the way the car will be used on the road and possibly for one or two track days. Has anyone done anything like this or have any ideas on the pros or cons of such a setup.
The attached image is from another forum but gives an idea of the type of setup I am talking about.




Regards
Tom

Why? You can play about till your hearts content with what youve got and it will still give better handling. The body was designed for it after all.

[greenamex2]

I have a RWD Toyota Corolla GT which has a 5 link (although rather poorly implemented) rear set up. It works fairly well and over the winter I will take the opportunity to correct it's remaining faults with a watts linkage and equal length parallel arms.

Have you considered this route as kits for your car, it would be a lot easier?

Alternatively have a look at a de dion setup (see Caterham). This gives most of the benefits of IRS (including adjustability if designed correctly) but would be much easier to implement.

[R59]

I'd go for a proper 5-link conversion, and get those links as long as possible, and parallel. 1deg neg, 10min toe in.

Rob

[greenamex2]

The rear links on the Corolla are pointed inwards a tad, presumably to keep the axle parallel in roll.

Any comments?

[zefarelly]

I read somewhere that Jim Clark had a Lotus Cortina with an Elan style Independant rear suspension, I always wondered what it would be like, the great man himself said the Cortinas handled better as time went on but the fun factor was greatly reduced

so I'll leave mine std and contiunue to learn the tail out opposite lock technique

[retro_msport]

At no time has a IRS setup on an Escort with the same power as a live axled one beaten the live axled when linked properly.

Ricky Hutchings Cossied Mk2 didnt fair that well at Brighton this year, using the BMW rear, he has the option to change back to conventional 6 link.

Some may say i'm biased towards 6 links as I spend all week fitting them, but i would gladly fit a IRS design if it worked. At the end of the day its all work wether its IRS or Live.

The only IRS that i would be looking at is upper and lower wishbones with possibly the BMW diff or a Hewland in the middle of long wishbones. Much shell cutting would be needed ie, the chassis rails will need moving a lot. But then i allready move these on my 6 links to allow an axle centerline to lowest part of the car of 300mm.

[Anuauto]

Originally Posted by zefarelly

I read somewhere that Jim Clark had a Lotus Cortina with an Elan style Independant rear suspension

...and its registration is recorded on the new Cortina thread in the "Chassis Archive" section of the forum!

[zefarelly]

Originally Posted by Anuauto

...and its registration is recorded on the new Cortina thread in the "Chassis Archive" section of the forum!

the trainspotters thread ?

[R59]

The very first Lotus Cortina's fitted with "A-Frame" IRS?? which they ditched when they couldn't get it to work properly (not that it ever stopped Jim Clarke from going fast in it!).

[zefarelly]

it was an A frame bolted to the underside of the dif casing, and front leaf hangers, still a rigid axle though, I think Chapman pilfered the odea from from someone elses design. they did refine it and it does work, the main problem was putting high loads through a tin plate diff housing, distorting it and loosing oil until the diff went bang.

at least all the cars behind spun off !!!