North American Turbocoupe Organization



motorsport c springs .. how bad are the rear springs?
svo_thunderchicken Offline
Senior Member
#11
ok i might have a answer to the "rear c kit springs are too light" question. Yes, the rear c springs are too light... in the beginning... let me explain.

Our cars come with pacific rate springs, meaning the spring rate is the same throughout its motion. Now the rear c springs are progressive, they start out light, and progressivly stiffen up to its maximum rating as its compressed. So the c spring starts out light, but ends up right at the end.. thats why its TOO low.. but if we were to space it up to make up for the bad start, then it still should work fine, but actually a pretty stiff ride
84 TC Silver 5 speed - PE EEC, Big Vam, RR cam, 35lb injectors, E6 swap, T3 60 Trim, 87-88 intercooler and hood, BOV, K&N Cone Filter *under constrution*
http://www.cardomain.com/ride/2298891/1

87 TC Black 5 Speed - Stock IHI, BCS Bypassed
http://www.cardomain.com/ride/2390431
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Chuck W Offline
Posting Freak
#12
Ok, I posted this in the Fox spring thread, but I'll put it here in the chance that someone will find it in a search.

The load rating for the C-kit rears is only
587#....
Stock Tbird spring rear load ratings are from about 830-940#......
That is a difference of about 300# per spring, or 600# total for the pair. Doesn't sound like a close match to me.
Those springs are really only suitable for Fox Mustangs...and barely at that.
83 TC Clone, 85 Mercury LTS, 97 Volvo 850 T5 Turbo, 78 Volvo 240, 93 F150
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svo_thunderchicken Offline
Senior Member
#13
chuck w... what would happen if i used c rear springs with adjustible che lowers? i know your answer but ill ask anyways
84 TC Silver 5 speed - PE EEC, Big Vam, RR cam, 35lb injectors, E6 swap, T3 60 Trim, 87-88 intercooler and hood, BOV, K&N Cone Filter *under constrution*
http://www.cardomain.com/ride/2298891/1

87 TC Black 5 Speed - Stock IHI, BCS Bypassed
http://www.cardomain.com/ride/2390431
Reply

Chuck W Offline
Posting Freak
#14
Look at the load rating and you tell me....

I guess if you always took a healthy poop before you drove the car and never carried more than a napkin in the trunk you'd be ok......

It's not the height....it's the fact that they are just too light for the car.
83 TC Clone, 85 Mercury LTS, 97 Volvo 850 T5 Turbo, 78 Volvo 240, 93 F150
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svo_thunderchicken Offline
Senior Member
#15
ok no more talk of rear c springs. im going to order some suspension techniques 83-88 rear springs post to lower it 1.5" and see what they do... 75 bucks and they will have them in stock at the first of april. Im going to measure them, pic them, and test them in both my stock 84 and 88 and post results... they are load rated for a thunderbird.. but i dont have the specs
84 TC Silver 5 speed - PE EEC, Big Vam, RR cam, 35lb injectors, E6 swap, T3 60 Trim, 87-88 intercooler and hood, BOV, K&N Cone Filter *under constrution*
http://www.cardomain.com/ride/2298891/1

87 TC Black 5 Speed - Stock IHI, BCS Bypassed
http://www.cardomain.com/ride/2390431
Reply

turbo d Offline
Member
#16
Alright, I'll bite. Chuck, I understand that you are probably very tired of this whole spring discussion, but I've been mulling this over.. I know the whole load rating concern, but what about using these springs designed for a stang (c-springs/eibachs) in a TC thats been lightened, say under 3000lb race weight? Isn't a fox body heavier then that?
You can't tell me that the front/rear weight distribution is that much different in a tbird than a 'stang.

I understand the problem with a stock/heavy 3500lb TC, but is there really that much more weight on the axle of a 3000lb TC vs. a foxbody? I know the back window is hefty, but shy of going to lexan and a fiberglass trunklid, there's nothing else I can remove from that end.

My plan is to finish the eibach/5 lug conversion in my car, get the adj, rear control arms, then take and weigh my car using the 4wheel independent weight scales.

Not trying to argue or piss anyone off, just looking for some opinions. btw, my 88tc is basically gutted, won't ever have a back seat, or carry groceries, and I like a firm ride, but not a kidney buster. It's basically a race car that will see some street use, not the other way around. I just want it dropped low, and be able to carve some corners.
Darrell
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svo_thunderchicken Offline
Senior Member
#17
im going to help chuck out.. if you car is lighter than usuall, rear springs that are not rated at the load of the car COULD work.. but for how long? The spring would not be designed for the load cycle our cars would put it through and result in premature spring saging and failure. Higher load rated springs use thicker bar diamater to hadle the stress of a heavy car. So the answer to your question is...

yes, they will work but for how long? who knows but it wont look pretty when it stops..

Correct me if you need to chuck w (rear spring god)
84 TC Silver 5 speed - PE EEC, Big Vam, RR cam, 35lb injectors, E6 swap, T3 60 Trim, 87-88 intercooler and hood, BOV, K&N Cone Filter *under constrution*
http://www.cardomain.com/ride/2298891/1

87 TC Black 5 Speed - Stock IHI, BCS Bypassed
http://www.cardomain.com/ride/2390431
Reply

JohnL Offline
Senior Member
#18
Well, this is interesting, I think the Tbird springs are made for just what Chuck hit on, carrying a bunch of luggage back there, and I know for me, usually it doesn't have anything back there, but sometimes I have to carry a lot as in the back seat and trunk full of stuff.

Fox mustangs carry around less sheet metal and almost 10 less gallons of gas at a full tank (about 60 pounds right there). Add in ABS, PRC, and amplifier and it's starting to get pretty heavy. Not to mention all the wiring for all that stuff, the extra overhang that a TC has compared to a Mustang, I'm sure there's lots more I'm forgetting.

I've seen some people using C springs all around but I don't know how. The only good solution I can think of is putting airbag helpers in both sides, but I don't know if this is an acceptable use of the airbags (the kind the drag springs come with).
John Lewis
88 TC, 87 XR, 84 SVO
Currently deciding which is worth my time.
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