Scallyk9

This is my first post and visit to what appears to be a great and knowledgable website. A yank from the USA West Coast has a question. I'm a twenty year Merkur XR4Ti owner (two of them) and have only used them as daily drivers until now. I'm currently starting a restoration on my current one and it seems that my Merkur really wants to be a Cosworth. Not many real Cosworths make it across the pond, but many of the parts do. Trouble is sorting out what they are. I'm building the car for the road and the occasional slalom or track day, so I wish to improve the suspension but still keep some road comfort and clearance.

I have access to some genuine Sierra Cosworth (3 door) rear springs but no idea of real specifications or what to expect from them. They are roughly 300mm long by 125mm diameter unloaded compared to stock XR4Ti springs at about 380mm and similar diameter. Although not side by side, the material thickness appears thinner on the stock Merkur one. The Cosworth springs are black, look almost new, and have 3 identifying painted dots on each (pink, green, and red). Can anyone one help me to know what I might have here? The differential mount, dampers, and bushings will all be upgraded.

daviddunlop83

iTrader: (7)

Welcome to PF

If the 3 door springs fit in, why not get a set of:- LEDA springs - Ahmed Bayjoo spec

http://www.randbmotorsport.co.uk/sho...?ProductID=291

Instead of the old standard cosworth ones. The standard ones arent the best but a set of koni shocks and those springs would be better.

The standard springs are crap and i changed mine to the above and was good for everyday use etc. You can get either road or track ones

tabetha

Those paint marks indicate std 3 door(cossie) springs, some of these despite what ford say were also fitted onto xr4i.
I've used the ahmed spring combo, and it is very good, personally I prefer AVO/chassis dynamics std ride height ones for the cossie.
You can find the rate easily with some bathroom scales, put spring on vertically, take a ruler to side, scribe mark at 0 load and another at 1" compression, then apply a known load such as weights till you get the 1" mark lined up, see what weight you have.

tabetha

Scallyk9

Thanks for the info and the clever spring rate approximation technique. Unfortunately, I don't have these springs in hand to try it and the owner knows noting as to rate. He acquired them years ago and never used them. By std 3 door (cossie) springs, I suppose that means compared to RS springs. My guess is that the Merkur XR4Ti is heavier than the Cossie models, and that the Merkur was sprung light for a softer ride in our market. I've read that the "progressive" springs used in the Merkur went from 250 to 500 lbs/in with about 250 used up when it lowered off the jack to static height. What I am now trying to determine is whether the 3 dr Sierra Cossie springs (which I can acquire cheaply) would be stiffer than Merkur stock. The Cossies are about 3.5 inches short and of thinner diameter stock. I'm guessing that they would be and may use them as a starting point...maybe more spring sets to come.

I had not heard of the ahmed springs but do know of some cars with AVO springs and more with Eibachs. The Ahmed spec LEDO springs might be ridiculously expensive to ship.

tabetha

Do you have any local GI's you know ?, as base dependant you'd be amazed what kit they have!!
The merkur would no doubt be much more softly damped than the eu cars, but would expect spring rates to be quite near.
I'll ask a buddy about the spring rate for the 3 door cos, and merkur, he's a GI but well into his racing stuff, would be surprised if he can't find out in a day or two, so long as he's not somewhere secret as he doesn't tell me jack!!
tabetha

Scallyk9

Thanks to all who answered my first post. Surprisingly, it would appear that the US market XR4Ti was not so much more softly sprung than the eu models, at least not the 3 door Cosworth Sierra. That is, until you take into account that the Merkur was considerably heavier at over 2900 lbs. curb weight.

I was able to get some spring rate numbers from a local rally suspension guru. He spec'd the Escort Cosworth at 353.4, the 4dr Sapphire Cossies at 290.7 and the Sierra Cosworth at only 268 (all in lb/in). The XR4Ti is harder to rate as it was a progressive spring specified at 257/503 lb/in much of which was taken up at the softer end just by lowering the car off the jacks. As the STA design greatly affects the numbers at the wheel, the wheel sees only 42% of the spring rate. The Merkur XR4Ti basically only "saw" around 105lb/in at the wheel, and the 3dr cosworth would only give me 268 x 42% = 112.6 lb/in. I'll pass on these.

It is interesting that the stock rear Merkur springs are very close to front springs on earlier model Camaros. These progressive springs became so popular for circle track racers, that they are currently produced by a company called Hypercoil (and probably others) in various heavier rates and marketed by numerous specialty retailers. This includes at least one specialized to Merkurs in the US.