Datsun Roadster Forum-311s.org

SLOroadster wrote: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.

I'm not an expert either, but I'd be careful about being even that low. Your points about roll center are on the ball, but if the lower arm is horizontal at rest, that means when you go into "bump", the arm is going to be travelling straight away to a situation where it's pivoting "up". This is a damn hard issue to talk about without diagrams, isn't it?

Thing is, if you take the typical stock setup, the lower arm points up to the center of the car. Try this: draw a right angle triangle along the arm, up to the center of the wheel, and back across to the pivot point. Then draw a similar triangle within that - but where the spring is located. There's a ratio of wheel movement to spring movement, which is steadily decreasing (or rather, getting closer to 1:1) as the lower arm gets closer to horizontal. This ratio then starts to *increase* again as the arm passes horizontal and swings up - every mm the spring compresses the wheel can move more and more. This means that your effective spring rate at the wheel (which is where you're in contact with the ground) is now decreasing with every mm travelled, whereas before you got the arm horizontal, the spring rate was increasing. This is another reason why if you lower the car excessively, you need ridiculously high spring rates to compensate. Suspension setup is always a compromise.

Cheers,
Steve

Ok guys, I will have the lone set of these springs in North America in the very near future. I have already been in contact with a manufacturer who says they can reproduce/duplicate them. I don't have a price yet, but I'm doing my best to keep them as cheap as I can. I will test the ones I have before sending them off to the company. I'm looking for about 50 people who are seriously interested. I'm doing my best to make this happen please PM me if interested.

Will

What is the measurement from center bushing to center bushing on a roadster ?

Chris

"...measurement from center bushing to center bushing...."

Shortest route: 46.75"
Long route (along the length of the spring): ~ 47.6"

I am putting an order together for the Composite Leaf springs through Flex-a-Form. Price is $425 US set, $375 set if we get more than 8 sets ordered. they will likely be ordered at 150 lbs/in rating, unless through discussion it seems softer might work better.

I will post to the list when the Measurements etc. have been finalized with Flex-a-form.

I strongly suggest you read through the links/discussion in this thread so you know what you are getting before you order.

Please let me know if you would like a set.

Hmmm, the Composite Leaf Spring Project. Sounds like a Sierra Club thing...
Darryl, how difficult is it to install this product? Are modifications necessary?
I kind of scanned the thread, but was wondering.

Linda

Linda,
We are doing our best to make it an easy, straight forward, bolt in swap.
Scott up here who has them in his car had a few minor glitches which we will try to rectify.
If there happen to be any 'gotchas' I will make it very clear what needs to be done.

I should have my springs in hand Tuesday or Wednesday of next week. I'm hoping to get them on the car and race it the following Sunday (the 9th). Hopefully I will have a glowing positive review by late Sunday night.

Will

Will you be changing shocker valving as well?

Cheers,
Steve

Damper valving will stay the same for now. I have the fronts set full stiff, the rears full soft. I have a second set of mostly dead Konis ( mounting posts are stripped and bent, but they still seem to work.) that I might be able to pull apart. I wonder what oil they use?

Will

Just so everyone knows, The springs Will and I are working toward, tho different, will work for all 1500, 1600, and 2000 models.

Daryl, How does 150 Lb/in compare to comp leaf springs?

Will, what you were discussing with the negative arch is usually solved with reversed spring eyes to increase arch but not increase ride height, but I'm sure you or the spring maker came up with that already. Is the rate on the tapered leaf progressive rising, or is it the same through the travel?

I won't know if I need a set until the engine is in the 64, hopefully this week.

I think the single leafs are a straight rate, but I'm not sure. I haven't heard back from the guy who made them. I'm hoping to put them on the car Thursday or friday. Not sure if I'm going to run the traction bars or just put the torque rod back in. I'm hoping to have race/test results by this time next Sunday. I'll post initial driving thoughts as soon as I have them on the car.

Will

"How does 150 Lb/in compare to comp leaf springs?"

I don't know what the comp spring rate is????
I don't even know what the stock spring rates are for sure. I have read that the rears were 150 lbs/in but don't know if that was the early or late springs which were softer. I have seen mentioned that the stock fronts were 525 lbs/in on one website (and had an email confirming this), but on another site it said they were 700 lbs/in.
I have not seen a spring rate in the Clymer manual, old Rallye catalog or Scott Sheelers books. So If you know the stock rates please enlighten us!!

Scott, who has the composites in his car @ 150 lb/in with Mike Young front springs (860 lb/in?), thought they were a bit stiff when he first put them in, but is quite happy with them now with his shocks adjusted.

At this point I don't know how they will be with the shocks available to us. I believe I have KYB shocks in my car now and don't expect to be changing them till they're worn out.

Daryl Smith wrote:"How does 150 Lb/in compare to comp leaf springs?"

I don't know what the comp spring rate is????
I don't even know what the stock spring rates are for sure. I have read that the rears were 150 lbs/in but don't know if that was the early or late springs which were softer. I have seen mentioned that the stock fronts were 525 lbs/in on one website (and had an email confirming this), but on another site it said they were 700 lbs/in.

I think you'll find that the 525lb/in figure is correct. Lou once mentioned to me, IIRC, a number around 550. I'd guess that the 700lb figure would be the Nissan Competition springs. As my first post mentioned, my fronts now are 780 lb/in.

Cheers,
Steve