JPBNY

Does anyone know the spring rate for the Bilstein Turbo Cup rear coilovers that were used on the factory cup cars they have blue paint dots but no spring rate on them.Also are the front matching springs still available or does anyone have a set for sale?

ehall

I believe they were 400# and did use t=bars. (I KNOW they used T-bars)

ehall

Fronts were 375.

ehall

springs can be bout a e shox for between 55.00 and 75.00 bucks.

Oddjob

The springs used on the Turbo Cups and Club Sports will be pretty difficult to find. I dont think you can find any new sets from vendors any longer, but may be able to find someone selling them in classified ads here or the PCA site. And sorry, Im going to hang onto the set that I have.

Ive seen various sources claiming the fronts to be around 180-410 lb/in progressive. The rears also have the tapered wire diameter, so they are somewhat progressive, though I dont believe they are as progressive as the fronts. My guess is that the max rate is probably between 250-300 lb/in. An owner of an Escort car told me he thought they were around 270 lb/in. With the stock setup (front and rear cup springs, koni dbl adj, 25.5 t-bar, 30mm front bar, 21mm rear bar), the car definitely oversteered. He put on a 19mm rear swaybar, then swapped out the rear springs to 200 lb/in springs to get the rear end under control.

I have seen an Excellence article on the Canadian cup car where the owner states he and another Cup expert tested the front rate at 200-370 and the rears at 180-460 lb/in. I think that is likely a mistake or a typo (reversed). The car would be absolutely undriveable (oversteer) with a rear spring rate that high and t-bars installed.

pete95zhn

I tend to believe this Excelence article and claim that these are wheel rates...
Me and my friend have coil-overs of these wheel rates on our cars,with 968 M030 staibilizers,and this friend of mine did 8min 36 sec lap at Nurburgring. Pretty fast time for uncontrollable oversteer...

Oddjob

The fronts are about 90% effective, so if you believe the article implies a front effective rate of 370 lb/in, then the spring rate is 410. The rears are approx 55% effective, so a 460 lb/in rate would require a 840 lb/in spring. Even if you think the printed rate is including torsion bars (25.5mm Tbar =175 lb/in), that would still be a 520 lb/in spring.

So you claim to have a well handling car with 400 lb/in front springs and 850 lb/in rear springs? You're kidding, right?

ehall

Hey Oddjob, wouldn't the valving have a signigicant impact in balancing those rates? The front valving on the Cup coil overs is 600/180, and 565/218. Were the stock cup cars not equipped with bilsteins?

Oddjob

Shock valving does have a significant/important effect on handling, but you cannot use it try to balance out spring rates that are dramatically mis-matched. The damping rates need to be matched to spring rates - meaning a soft shock wont work with a stiff spring or vise versa. So the suspension is all designed to work together. It wont be effective to put very stiff dampers on the front in order to offset very stiff springs in the rear.

The Euro and Canadian Turbo Cups came with Bilstein, the US Club Sports ('87-'88 S's and '87 Turbo's for the SCCA Escort Series, and the '91 S2's for the Firehawk Series) came with the double adjustable Koni full race struts and rear coilovers. They all used the same front and rear springs.

front spring: 951 343 531 32
rear spring: 951 333 531 32

Parts still show up in the PET price list - not in the illustrations, so you could call a dealer, but with other motorsports parts Ive tried to source, they will likely be n/a.

I have never come across any info on the valving rates for the original bilstein suspension on the factory turbo cups. But I would be surprised if it differs much or any from the numbers that you post, which is the standard valving on the current bilstein setups available from various sources (some call them "Turbo Cup", other vendors call them "Escort").

Jason at Paragon probably knows or has a very good idea what the range of adjustable valving on the original Club Sport koni dbl adjustable setup was. Paragon "came across" some sets of original rear coilovers over a year ago, and now are having them made new, so Im guessing they are using the original valving.

pete95zhn

Full coil-over,no t-bars,no kidding.

JPBNY

Ok I have the wire size of the rear coilover springs they start at the top at 10.56mm and shrink down to 8.36mm at the bottom of the spring .The part number on the rear coilover is 951-333-032-33 is this a true "cup car"part? The front struts have the following part numbers 951-343-032-35 and 951-343-031-35 the fronts are green and the rear are a gold tone. The rear springs due have a blue paint mark on them.I do not have the front springs so I am trying to find the rear spring rate so I can buy the correct front rate spring.

Oddjob

Those part numbers are the correct factory numbers for the genuine Turbo Cup suspension, they match two different part number lists I have for both '88 Euro and '88 Canadian Turbo Cups.

My front springs have 2 blue dots (which just means the second tolerance group) and my rear springs have a single blue dot. I already mentioned what I believe the rates to be, but since there is some speculation and disagreement on this topic, the only way you would probably feel confident is to determine the rate for yourself.

You could take them to a shop that does shock rebuilding and see if they could test spring rate, contact porsche motorsport north america and give them the part number to see if they can research a spring rate for you (probably not, but might be worth a call or email), or try to test them yourself by measuring compression with various amounts of weight (which will be complicated by the progressive nature of the spring). Could also send Sebastian at Asarus.com an email and see if he has ever come across factory documentation on the spring rates.

Are you going to be using 25.5mm rear torsion bars? What sway bars, what tire size/widths? - all have a factor in what you want for the front spring rate.