Single leaf rear springs. (longish post)

[Daryl Smith]

In case anyone else is wondering, Yes, I do have my composite leaf springs installed. I'm running with the standard replacement KYB gas shocks and everything seems just fine, thankyou very much!
I haven't done any racing or autocrossing, but in some mildly spirited driving I was very happy with both the ride and handling. Other than being a lot smoother riding than the old worn leaf springs there didn't seem to be much to talk about. Smooth, solid, and lighter.

As far as the debate between composite and steel, I am firmly on the side of composite for at least a few reasons:

1) Safety - as much as some people seem squeamish about something as weak as fiberglass holding the a$$ end of your car up, everything I've read (on the internet no less) points to it being SAFER than the steel monoleaf. This is not a new technology. Corvettes have been using composite monoleaf springs since the mid '80s. There are many other vehicles which use/have used them from the factory.
They are made for pickup trucks, 4x4s, all the way up to the big rig 18 wheelers....as well as in many forms of racing. If it's good enough for them, it's good enough for me.

2) Weight - Losing weight is good for both gas milage and acceleration. While Will may have a point as far as the wieght balance of the car, a few things I've pointed out before, such as moving the battery to the back, etc. can help the weight balance. On the other side, will you be racing or pushing your car to the limit? If not, even with everything else stock, I doubt you would notice anything other than the better ride in everyday driving. If you are racing, and need to add weight, you can corner weigh your car and put the weight where it will do the most good! Moving the battery from the engine bay to the parcel shelf/trunk WILL help balance the car, as will removing the stock 4/7 blade fan and shroud and installing a lighter electric fan, remove those heavy stock metal horns and put in a new LOUDER lighter plastic one..........
Remember Colin Chapman - "Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere".

??Did I read somewhere that you want to eliminate as much unsprung weight as possible? And the leaf springs are counted as approx. 50/50 sprung/unsprung wieght??

3) Ride height - With the eyes 'reversed' on the springs, my car sits pretty much level with the stock front springs. No lowering blocks required.

4) Choose your spring rate - Match the stock springs or go right up to 200+. I'm happy with the 180 lb rate on mine, but I'm no expert.......

As far as the actual performance/handling/ride it's likely they are comparable, tho the composite is supposed to have an edge in reaction time, it's probably not noticeable to most people. To be fair, it's not easy to compare unless you've tried them both.

So, like everything else on the car, this can be a game of compromises. Consider your options - newly manufactured stock style leaf springs (easy bolt in, what the car was made for), steel monoleaf (modified 28[?] yr old Volvo spring?), or made to order fiberglass composite leaf spring.

Of course, I'm biased. I am not by any means trying to hurt anyones business. If it wasn't for Stephen bringing up the monoleaf dicussion, we wouldn't still be at it 28 pages later and trying to decide what is better. It probably should come down to the individual and what the use of the car is.

[Garm]

Great post Daryl. This whole discussion has been worthwhile for me.

I'll only take issue with Colin Chapman, not you. Adding power doesn't add weight on my projects, and the "slow in, fast out" approach to racing the line is benefited greatly by power gains (assuming traction/contact patch/etc. is handled properly). So I see power as nearly a universal benefit, and losing weight 100% a universal benefit.

OK.... back to the springs...

[gboone]

I haven't read all 28 pages of this topic but need to bring up a potential problem of bad driveshaft alignment caused by changing springs. When the arch of the spring is changed, it can change the angle of the pinion shaft. This is because the angle of the spring where it mates to the axle housing determines the angle of the axle and pinion. The pinion shaft needs to be parallel with the tranny output shaft. I'm using flatter than stock spring and found that it significantly lowered the pinion flange. I remedied this by installing beveled lowering blocks. It's worth a look if you change springs. Bad driveshaft alignment causes vibration and shortens U-joint life. Here's a good article on the subject:
http://www.hurst-drivelines.com/files/U ... 111606.pdf" onclick="window.open(this.href);return false;

[imag]

For anyone who is still interested in this thread: I got the composite springs - 220 lb/in - and I have to agree that they are awesome. We just got through a day of road rallying and they are miles better than the steel comp springs. I cannot wait to pair them with the new Konis.

For reference, we had ours made with the standard low profile form, not the extremely flat profile (which was actually designed to be a transverse leaf). Because we are doing road rallying with occasional dirt roads thrown in, FlexForm recommended that we have go with the standard curve, as composite springs are apparently not designed to be compressed much past flat.

With both eyes reversed, I think our ride height is about at stock. Obviously, lowering blocks and/or the flat profile could bring that down for track use. If anyone is considering the switch, I highly recommend it. I really appreciate this thread and the folks who paved the way.

[Gregs672000]

Awesome man, glad it is working out! Post some pics of the rallyes when you're out and about! Maybe a set of konis will be in the budget for next yr, if they're still around.

[imag]

Awesome man, glad it is working out! Post some pics of the rallyes when you're out and about! Maybe a set of konis will be in the budget for next yr, if they're still around.

Thanks so much for your help! Advice from you and gboone was instrumental in getting the right spring setup for the car. We had one shot, and I think we nailed it. Really appreciate the replies.

I will have to start a thread on the rallies. I am already on that group purchase for the new Konis; I can't wait for them to show up!

[Gregs672000]

Awesome man, glad it is working out! Post some pics of the rallyes when you're out and about! Maybe a set of konis will be in the budget for next yr, if they're still around.

Thanks so much for your help! Advice from you and gboone was instrumental in getting the right spring setup for the car. We had one shot, and I think we nailed it. Really appreciate the replies.

I will have to start a thread on the rallies. I am already on that group purchase for the new Konis; I can't wait for them to show up!

Happy to try and help... that's what we're here for! Ya, I was thinking about MY budget for Koni shocks for next year... will be watching for posts from you about how you like them!