88_WRC_Replica

I’ve some how gone and built a very tail happy little monster which is fine for the slow stuff, but is down right terrifying at speed.

I’m running a standard rear bar and 850lb springs which keep the car at standard ride height. There is no warning what so ever at the moment this car brings new meaning the phrase snap oversteer. I was out this weekend for a tuning session at a track where there are two areas where I’m flat in 4th, possibly 5th but I’m not there yet.

To break it down I have two problems

1) Under heavy breaking the car feels like it wants to swap ends and did twice in the flat 4th section. (I have video of the car pitched forward under heavy breaking and just as I feed in a little steering or any correction as the rear goes light it’s a twitch and I’m around.

2) When quickly transitioning from one corner to the next the car feels like it’s on tip toes just about to spin and I’m only pushing maybe 60%.

3) Power oversteer out of a corner even running 235 R compound tires the car will not put the power down it just wants to sway from one side to another usually until I let off to shift. Running LSD and only 280HP at 18PSI.

I was told by a marshal and other racers who helped push me out of the bog at the end of the straight that my car was sitting far too high in the rear and needed to be lowered. Ther informed me that all of my problems were due to the center of gravity being too high.

Questions:
1) How much fuel to you run at the track. ( I was running ½ tank since I was worried about the pump pickup.)

2) Are you running conventional springs or coilovers?

3) Do you know the approximate height of the car.

Since I can’t run coilovers on the rear due to the placement of our rear brake caliper I’m stuck with linear rate springs. Since I can’t get custom wound springs made I’m stuck running a 8.5”x10”x Xlb spring. I’m thinking of getting a set of 700lb springs this week to see if they make any difference in the feel. What I’m gaining in lowered CG I’ll be loosing in stiffness.
FWIW I’m running Leda Coilovers on the front with a 300lb spring.

I’m also going to add a better F/R brake bias controller I’m thinking even thought I’ve never seen it on film that the rears may be getting too much brake enhancing my light feel.

Not having the level of support that you boys enjoy in the UK trying to make this car a track terror in a good way is proving hard on my bank balance and harder still on my Ego.


Comments, suggestions and feedback greatly appreciated.

Simon

STUCOS

iTrader: (8)

ok mate.i think half your problem would be rear to hard,i run 300lb fronts on my 3dr and 220 rear but i am on coilovers all round,i find the rear of mine a bit skippy,and i am going to change to 180lb on rear,try putting up a post for marco polo he is a bit more clued up on it

cheeRS stu

foreigneRS

850 lb / in rear springs does sound massively too hard to me, especially when combined with just 300 lb / in fronts.

what's your thinking behind this, as i guess if anything the weight bias is towards the front axle?

i suppose that with 850 lb springs, you would need massively different damper rates, more like tarmac rally spec.

i prefer to run reasonably soft springs and more anti roll bar, particularly if the car is used on the road too. to increase the stiffness of the standard rear anti roll bar, you need to either shorten the lever arms or thicken up the bar by welding a tube around it, or both.

88_WRC_Replica

Thanks for the suggestions guys!

I run the 850's because the few people who race these cars over here use between 850 and 1300lb springs. Not wanting to go massively stiff I figured the 850 would be a safe start.

I've decided to have my spax sport springs that I was using measured to see how hard they are. Since they are only 2000miles old I'm hoping they haven't deformed too much.

Having never tracked this car before I had no start point other than buying a set of sport springs. I'm also considering buying an entire rear subframe from a RS and just bolting it in with a set of coilovers. Although that would have to wait until the winter now.

I should know if a few days when I get back from Colorado what the test out like.

Porkie

iTrader: (1)

850's!!! at the REAR???????????

markk

iTrader: (2)

your about 550lb too hard for the rear of a three door for tarmac spec , even worse if your not using pukka dampers ,

the dampers your using - well your not actually using them at all with 850 lb springs , they just wont be valved to take that sort of pressure , the spring rates are directly proportionate to the weight of the car , and foooookin ell 850lb at each side of the rear

when i run tarmac spec , at the rear i use 260/90 damper ratings (iirc) and a 12inch spring with a rating of 500lb(to prevent squat), at the front i used 360/120 with a 9inch spring and 360lb spring and no roll bars, thats is a good balance of smooth but no body roll or rear squat (or the very minimal req) but with very predictable handling ,

no for a bit of road and track i may use slightly diff to that , but also look at the rest of your susp geometry , its vital for stability at all speeds , i could go on for ages but heres a small bit of help ! !

hth


mark

Danny B

how are you working out the spring rate? if you have hydralic bendh press available and some corner weights then simply use one of the scales put the spring on and zero the guage(set to lbs) then compress the spring 1 inch, this will give the correct pressure in lbs.

what is the total weight of the car as this is very important when selecting the correct spring rate for a car, I'd guess and say you need to be running around 420 front/300lbs rear weight dependant.
Hope this helps.

NUTS RuS

iTrader: (35)

850 sounds massivly too high for track. May work well on oval circuits where there isnt much braking or weight transfer going on.

Sounds also to me that there maybe some tracking issues with both the front and rear toe needing to be checked. Sounds like the back is towing in too much ??

Fastmaul

I think he needs a 850 lb spring cause he's fat! trying to keep this alive for you simon
thanks guys for helping him out!

88_WRC_Replica

Mark thanks so much for the information it's filling in some of the blanks for me. My biggest problem is that I can't get custom wound springs, so I end up running a "short track" spring. The springs are 5"x9.5" x 850lb. My concern with running a shorter spring was that if they were short they may become loose as the control arm unloads. By running a stiffer spring I knew they would never allow that much roll.

To say the least it's a pretty poor system.

Since I'm away on business this week my brother is getting the spax springs that I used to use measured for me which are 5x10". I'm expecting them to be around 500lbs but I'll have to wait and see.

Thanks again for your assistance, it's a great help.

88_WRC_Replica

Danny Initially I was working them out by measuring the spring width number of full coils etc. I then found a local racing shop that had a compression tester.

Sad to say I don't know the weight of the car it's never been tested but it's fully gutted and changed so I'm expecting around 2700lbs but I really don't know. I did try a set of 200 lb springs this winter but the car sagged so far the wheels were rubbing on the aches. Not really understanding where I should run I started too listed to what others where using hence my 850lb springs. I'll be having the car corner weighted before my first session on Sunday.

88_WRC_Replica

They car was aligned back in May and set to stock spec's, I didn't want to mess around with toe until I got used to how the car was going to feel. Normally I would toe out the rear a little to help the car rotate but it's not a problem at the moment.

Thanks for the suggestion!

88_WRC_Replica

Har har har, fat but not merry.

Thanks for the help Erik!

88_WRC_Replica

Can I ask what you run in the rear?? What system workes for all that power??

Thanks

Simon

RichardPON

I would also say it would be worth lowering the back as well, if it sits up quite high.

Running standard ride height and too hard a spring at the rear used to cause me to fight to keep the car in a straight line under braking.

I got the same effect last year when I ran slicks suspension settings with road tyres, and it was all over the place!

I think the advice given is pretty sound - for reference, I run 390 at the front, and 200 rear.

Azrael

I wonder what springs I run :-(

Anybody knows what rate are Lesjofors lowering springs for Escos?

88_WRC_Replica

A 200 in the standard location or 200 on a coilover?? If it's in the standard location then our cars are much more different that I thought.

Fastmaul

RichardPON

Sorry - that'd be 200 coilover rates...........

88_WRC_Replica

Ah that's what I thought....

Maybe I should just swap my brake caliper location and run a coilover setup.

Fastmaul

Simon, what rear calipers do you have?? the cossie set up, or the Tbird conversion?

markk

iTrader: (2)

i also run probably higher than std height !!! just to throw a spanner in !!!

88_WRC_Replica

It's the SS Brakes conversion kit so I'm guessing it's the Tbird. I've emailed DG about making me a bracket to relocate them higher so I could run a coilover.

Tony Ryan

Its not unusual to have Race spec RS 500's running on VERY hard springs , i know of a Circuit car that uses 1350lb rear springs in a GpA mod in the std place ! To say that it doesn't corner well is an understatement tho , and its based on stopping the car from bottoming out under acceleration/power and cornering !
Without giving the whole game away the key to suspension is not in the spring rate or the damper but a combination of Anti -roll bar and these other two . If you start to get technical and pre-load the ARB as part of the suspension then you can increase spring rate but only accordingly with damper and spring settings . Ina nutshell for track use ( i know fuck all about road cars ) a damper that is a strong as can be ( suited to the individual corner weight of the car ) combined with a relatively soft spring and a massive anti -roll bar will give the most predictable handling. If you have a spring too hard for the damper it does 2 things ; bounces on the spring , and bends the damper tube through coil binding .
I ran 500-600lb springs on the rear of my Sapphire and it handled well , if you add an Escort Cosworth ARB then it helps but moves the axle around on the diff mount ! The front came on 900lbs springs and after testing i found 700lb worked the best, the dampers were a good quality Koni coilover on the front & a telescopic on the rear. However when you use a rear coilover ,the fulcrum point is moved by over 50% so you should reduce the spring weight accordingly until you settle on what you like !
Hope that helps

Fastmaul

I've heard of people having trouble mounting coilovers with the ss/tbird calipers.