Single leaf rear springs. (longish post)

[Alvin]

owned
-who will fork over $500 for pair of leaf springs? besides race-car drivers?
-who here will continue to make these from scratch when there is one on ebay?
-who made the part on Ebay?
-someone down under is laughing at this thread
The saga continues...

[duff me]

I wonder if these guys could make some comparable springs.
http://stores.shop.ebay.com/KennysRodan ... mit=Search" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

I don't know the exact specs, but they make a few that look similar.

[windy311]

http://cgi.ebay.com.au/Datsun-Parabolic ... 7C294%3A50" onclick="window.open(this.href);return false;

[ttyR2]

These guys have some, haven't a clue if the spring rate is right for the Roadster, or if the length is right: http://www.speedwaymotors.com/Chrysler- ... ,4850.html" onclick="window.open(this.href);return false;

[Daryl Smith]

Took a ride in a '68 2000 Solex car Saturday with the composite fiberglass springs. I was very impressed. The car had "Mike Young" uprated front springs and the composites were rated at 150 in/lbs, riding on 205/45/16 tires with adjustable shocks.
The ride was better than my stock sprung '66 with 185/65/15 tires (nice ride on a road which would rattle your teeth in my car), and the owner was very happy with the cornering performance as well.
I am looking into the composite springs with every intention of buying a set. I don't see a downside yet. Lighter, better response, available with whatever spring rate you want, and easier/cheaper than re-manufactured Volvo springs......
The leaves in my car are sagging and you can see where the lower leaves have worn into the leaf above it.......I'd rather replace it with something designed to work better, and drop the weight in an area which will do a lot to improve the handling at the same time.

[SLOroadster]

I'm not sure you want to pull that much weight out of the back of the car unless you can pull and equal amount out of the front. Its your car, do what you like, but I'm really not sure making that large of a weight bias change will do good things. Heck I'd love to pull more weight off the car, but I don't have any idea where to pull it from the front of the car to balance the weight back out. Yes, in the case of an overgrown battery, moving it to the trunk will change the problem, but create a potential different one. In my case, a 10lb sack of four will not cover the missing 40lbs of spring.

I'm still working on getting a set of the Volvo springs and duplicating them. I will know more from the reproduction standpoint by the end of the week. Right now I'm looking at the feesability of doing a production run. Its no more than exploratory at this point.

Will

[ttyR2]

Anyone know what the F/R weight distribution is on a stock Roadster?

[Tomakze]

Where would you go to acquire composite springs? weren't we just discussing "the cost prohibitive composite springs" and how "making a die would cost 15-16k"?

[GeoffM]

Where would you go to acquire composite springs? weren't we just discussing "the cost prohibitive composite springs" and how "making a die would cost 15-16k"?

There's carbon fibre composite and then there's fibreglass composite.

[Daryl Smith]

"I'm not sure you want to pull that much weight out of the back of the car.........I'm really not sure making that large of a weight bias change will do good things."

I'm not sure either Will, so why don't we look at some #'s and see what we come up with instead of just saying 'I'm not sure....'

1) Stock springs measured (by me) at ~22 lbs each. 44 lbs total.
2) Modified Volvo springs at ~11 lbs each, 22 lbs total (from previous posts)
3) Composite springs at ~7.5 lbs each, 15 lbs total. (approx. from claims on websites)
4) Stock battery probably 35-40+ lbs. (guess?)

A) By removing the stock springs and replacing with the Volvo, we are removing ~22 lbs.
B) By removing the stock Springs and replacing with the Composites, we are removing ~29 lbs.
C) By moving the battery to the trunk or parcel shelf area, you move that weight to a lower center of gravity area, as well as changing the weight bias slightly front to back.
D) Most people who replace thier batteries to drop wieght will still be in the neighborhood of 25+ lbs.

Now for the questions, conjecture, and just plain guessing......
1)The difference between steel and composite monoleaf is ~7 lbs.....Will it really make that much difference which one you choose? It would seem that even moving an 11 lb. battery to the back would negate that difference, and be an improvement in F/R balance.
Difference between stock and either monoleaf would be more of a concern........if not moving the battery........ Is it a concern if not racing?
2)Either monoleaf will be an improvement on the stock leaf springs. They are said to react faster and keep the wheels on the road where they should be. The composites drop more weight and because of this and supposedly faster reaction time anyway, should have a slight edge as far as keeping the wheel on the road. My feeling is that this should far outweigh any weight concern in the difference we are looking at here. Is that loss of weight going to make a huge difference in traction? Would someone who isn't racing and pushing the limits of the car all the time notice anything besides an improvement in the ride?

I will be the first to say that I know NOTHING about suspension setup, yet. I will say it is very hard to find definitive info on the stock setup (spring rates - still trying to confirm these). I often see it stated that you want a 'stiff' front end with the comp sway bar and a 'soft' rear setup without a sway bar. How 'soft' is 'soft'? What spring rate should we be shooting for? Would 135 lb/in be better for an otherwise stock suspensioned car? Less?

Personally I see no need to lower the car, I'm not racing, but I do enjoy some very 'spirited' driving and some of the roads would not be kind to the undercarriage of a lowered car. I would prefer to keep the stock rated springs up front if possible.

So, by all means, PLEASE, poke holes in my thoughts/ideas. Point me to some info I can use.
Bring some more #s to the discussion.............

As far as someone down under having a good laugh at this thread, I highly doubt it. There is some really good info here and the potential for further improvements to be made. I really want to thank Steven for starting this thread and Dave and the other Ozzies for adding to the discussion.

[fj20spl311]

I agree that a street car doesn't need to be lowered. I do like stiffer springs both front and rear.

[st3ph3nm]

Now for the questions, conjecture, and just plain guessing......
1)The difference between steel and composite monoleaf is ~7 lbs.....Will it really make that much difference which one you choose? It would seem that even moving an 11 lb. battery to the back would negate that difference, and be an improvement in F/R balance.

Absolutely. IIRC, the roadsters are 55/45% front to rear - it may be a smaller difference than that. Supposedly, 50/50 is ideal, but maintaining a *little* more weight at the front isn't a bad idea, IMHO, for improved turn in.

Difference between stock and either monoleaf would be more of a concern........if not moving the battery........ Is it a concern if not racing?
2)Either monoleaf will be an improvement on the stock leaf springs. They are said to react faster and keep the wheels on the road where they should be. The composites drop more weight and because of this and supposedly faster reaction time anyway, should have a slight edge as far as keeping the wheel on the road. My feeling is that this should far outweigh any weight concern in the difference we are looking at here. Is that loss of weight going to make a huge difference in traction? Would someone who isn't racing and pushing the limits of the car all the time notice anything besides an improvement in the ride?
<snip>
Personally I see no need to lower the car, I'm not racing, but I do enjoy some very 'spirited' driving and some of the roads would not be kind to the undercarriage of a lowered car. I would prefer to keep the stock rated springs up front if possible.

Entering a whole new kettle of fish, here. In general, a lower centre of gravity will improve mid corner speeds, but there's a limit to how low you can go before ruining effective spring rates.
Even if you're not into spirited driving, I can't tell you strongly enough how much a stiffening of the front *in relation* to the rear (and this is a game that's all about the entire system, not one end by itself) will improve the overall ride. If you *are* interested in spirited driving, getting that front/rear balance right makes a big difference. It's a win/win.

As for weight balance, there's a big difference to be made in changing the ride heights at the rear. Lou keeps a bunch of lowering blocks that have been made up at about 2-3mm differences, for corner weighting the competition cars. It's really interesting watching the difference in weight bias you get from raising and lowering the ride height.

The real key to good handling is diagonal weighting - front left to rear right and vice versa. If you can get those diagonals the same, then the car will feel much more balanced, and be far more predictable than before. At the end of the day, even Carol Smith (I *strongly* recommend his books if you're interested in improving handling) biased his designs for driver feel and confidence, rather than outright corner speed.

As far as someone down under having a good laugh at this thread, I highly doubt it. There is some really good info here and the potential for further improvements to be made. I really want to thank Steven for starting this thread and Dave and the other Ozzies for adding to the discussion.

Definitely not having a laugh. Look, if shipping wasn't the issue that it is, I imagine I'd have ordered a pair of fibreglass springs. As it was, the Volvo setup worked out cheaper, especially because Lou was interested in the experiment (my car was the guinea pig), and did some of the work in his own time.

Cheers,
Steve

[GeoffM]

I agree that a street car doesn't need to be lowered. I do like stiffer springs both front and rear.

The only reason I'll lower the front of mine is to get rid of the saggy bottom look of the stock stance and also close up the front wheel gap. Esthetics really.

[Daryl Smith]

The only reason I'll lower the front of mine is to get rid of the saggy bottom look of the stock stance and also close up the front wheel gap. Esthetics really.

A set of 185/65/15's or 195/55/16's will close that gap without lowering!

[SLOroadster]

I'm by no means a wiz with messing with suspension geometry, but I do know the roadster can be improved. If you over lower a car you can drop the roll center below ground level and that is bad. To compensate for it you need stupid high spring rates. A quick way to tell if your front suspension is off, is to look at how the lower A arms sit with regards to the ground. Make sure the surface is level. If your lower A arm points upward toward the center of the car, the roll center is too high (or at least could be better) if the a arm slopes downward toward the center, your car is over lowered and the roll center is too low, likely below ground level. If the lower a arm sits horizontal to the ground, you are set. Its a quick and easy way to eyeball the setup. There is a formula to find exactly where it is, but you need to take a few measurements, and do some figuring. The rear is more difficult, but I think the roll center is located where ever the highest for/aft pivot point is, so in otherwords its near the torque rod pickup point on the top of the axle. That is a bad thing. Too tall of a roll center causes excessive body roll. I'm not positive on the rear roll center location. I do know that a panhard rod lowers the roll center quite a bit. This brings in another variable. Its called roll couple. Its a line drawn front to rear through the 2 roll centers, I think (again not positive so correct me if I'm wrong) you want the roll couple to be close to horizontal, perhaps just sloping toward the front.

A perfect example of a bad suspension geometry is my Alfa. The front roll center is below ground requiring 1300# front springs, and the rear is way high, causing lots of body roll and brake dive (a different factor dealt with on the front end. The roadster has lots of "anti-dive built in") the rear springs on my Alfa are 180#.

Also a suspension system must move in order to work correctly. If you make the car so stiff that it has no suspension movement, it will skip around and not stick well (sound like anyone's roadster I know? ) This also happens if you compress the suspension and hit the bumpstops causing instant infinite spring rate. I think this could be an issue with the comp springs, however I've heard that just rearching the springs will fix the problem quite a bit. Apparently the flat comp springs run into strange issues when the compress and flex backward (springs don't like that.) I'm not sure what exactly happens with the spring rate, but it does something funky.

So based on that, we know that the spring must have a positive arch to work correctly. That means that it must have enough arch to make it through full travel without going to a negative arch, and should stop when its about flat. That also means that without doing lowering blocks, the stock ride height is where you want to be with the back end. Now to lower the roll center there are a couple of options, either a Watts Link, or a Panhard rod. The Watts link is a better solution, but the panhard works. Now for most people stock is fine, but for those of us who like to wring that last 0.001 seconds out of the car, we need to get creative and run the watts link or panhard. They also serve another purpose. They locate the rear end from side to side. To lower the center of gravity, you need lowering blocks.

The Volvo springs are parabolic, and should (as Steve said) act more like a coil spring than a stock leaf spring. The spring its self is thin on the ends and gets thicker as you get toward the center.

I have a manufacturer who is willing to look into the possibility of reproducing sets of these springs, I just need to have one in hand (working on that.) The tentative production run is 50 sets, but nothing is set in stone, and there are no prices yet. At this point they aren't sure they can do a parabolic leaf spring, but they are willing to explore the idea. At this point, I'm willing to possibly spend the $ on the ebay set to get my hands on some. They are about what the vendors are charging for NOS '66 springs. Shipping will hurt, but sometimes pain is involved with winning.

Will