Single leaf rear springs. (longish post)

[Daryl Smith]

About 1/2" lower than stock, slightly stiffer front springs, revalved shocks to match.....
Hard to beat a sorted setup. Too bad it's not local.

I've never seen Bilstiens mentioned in the threads for shocks before..........Just Konis and KYBs...

[st3ph3nm]

Yes, Lou Mondello is putting the kit together - sadly, he's not online. He's a big fan of the Bilsteins, due to the experience of Horton Poulter's tarmac rally SSS Bluebird (411). Bilsteins have a thicker body, hence more oil, and therefore better heat absorbtion qualities than just about anything else on the market. So on a long stage, he was finding that the Konis would fade out, whereas the Bilsteins just keep going strong.

I doubt, though, that you'd notice a difference from the Koni unless you were doing long stints at competition speeds.

Cheers,
Steve

[Skyman]

Kyle, what shocks do you have? I went to the GR2's and it made a world of difference.

I'm running new KYB's. They seem more like a dampener, than a gas type shock.

Kyle

[RC240z]

now if we could get double adjustable Bilsteins :):)

[fixitman04]

The guy who built Phil Brook's car is the one making the springs, and modifying the Bilstein shocks. A friend of his is selling the stuff. His name has been mentioned several times in this post. I'd say the whole 9 yards is worth the $$$$, too bad the shipping is going to cost about $500 or so.

Will

how much were the rear springs alone? i already have a set of comp fronts , i was thinking it was going to be a lot with shipping included. that is why i said it would be pricy.

i only want to set my suspension up once, especially the paying for it part

[SLOroadster]

Wait till I take mine off again and take them to the company. The goal is to make them less than the current cost of the stock springs. If you already have the front comp springs, these should work nicely. As soon as I have a cost, I will let everyone know. I'm also going to try and offer these springs to any of the 510 wagon owners out there as well. I just need to find them.

Will

[Daryl Smith]

I ordered a set of composite springs today. 180 lb/in. Expect to see them in 2-3 weeks.

Comments and questions from Greg Burrows:
"Got out my How to make your car handle book by F Puhn, and he has a chart showing how to select spring rates based on sprung weight per wheel and desired suspension natural frequency. He says a race car should be around 2 cycles per second, a typical soft sedan is about 1 cycle per second. The chart he has is limited, but just guessing at what sprung weight per wheel is on a roadster in the rear (400lbs or so?) it doesn't look like we would want to go more than 150lbs on the springs. That caculates out to a frequency of 1.9. I wish I could do math, but I suck, as he has the formula in the book but I can't figure out how to use it (the chart only shows spring rates in 50lb increments, so 100lbs, 150 then 200 etc.). Read my Rallye book last night and he confirmed the Koni shocks were very stiff even on the loosest setting."

Anybody have a handle on the equation/numbers we should be using to calculate this out?

Thanks

[dbrick]

Best I can do is offer to loan a copy or make scans of the book. My math skills have fallen into doubt latley .

http://www.amazon.com/How-Make-Your-Car ... 0912656468

[Gregs672000]

ok guys, I emailed Daryl on this but don't know when he will post. Figured out how to do the math. Here is the formula: Take the spring rate and divide it by the sprung weight of a rear wheel (corner, axle, whatever... half the weight of the rear part of the car), take the square root of that and multiply it by 3.13... that will give you the frequency. For example, assuming 450lbs per rear wheel, using a spring rate of 180lbs, that calculates out to a frequency of 1.97. A 150lb spring will give you 1.8 frequency. A comp spring of 207lbs gives 2.12. Remember, I am assuming a weight of 450lbs (the manual says 1003lbs for the rear I think) and just took off 100lbs (50lbs per side) for unsprung weight... could be a lot more. Then again, I have a roll bar and the battery in the back (but no spare tire). I would be fine with a frequency of 1.97, especially if it rides like a softer spring while giving me the control of a stiffer spring. Heck, I've had comp springs on my car for the past 24 years!
Greg

[st3ph3nm]

I ordered a set of composite springs today. 180 lb/in. Expect to see them in 2-3 weeks.

Comments and questions from Greg Burrows:
Read my Rallye book last night and he confirmed the Koni shocks were very stiff even on the loosest setting."

Thanks

The settings that Koni used are not ideal for the Datsun Sports Roadster. Ideally, you need to get them re-valved - and essentially swap the valving from front to rear. Then you can get some compliancy back into the rear end, and less diving at the front. I think you'll find this will improve the roadster's handling even without changing the springs.

Cheers,
Steve

[gboone]

I see there's 9 pages on this topic and I don't have time to read all the posts, but want to express my interest in the rear composite springs. I may be a party to a group buy, but ones that are close to comp springs but with a somewhat less spring rate.
Gary

[Daryl Smith]

Going to be another week plus before my composite springs arrive. I will post here and the email list when they arrive and are installed, with measurements for ride height etc. so it should be easy to order with higher/lower ride hieght and stiffness if wanted.

I've been trying to find some more in depth info on the monoleaf springs, but so far am coming up empty........

[406dewey]

I am responding to the questions about corner weights of our roadsters. I just weighed mine 2 weeks ago and got the following weights.

Empty With driver
LF 597 664
RF 541 548
LR 508 592
RR 503 543
Total 2152 2347

I have several mods worth mentioning that have impacted weight; electric fan and oil cooler mounted in front of the radiator, full roll bar with partial roll cage, battery mounted in the left rear of trunk. Weight discrepancy from individual to total weight is due to decimal round off of individual weights.
Hope this helps, Dewey

[Gregs672000]

So, based on the figures provided, it seems reasonable that the rear sprung weight is somewhere around 450lbs per corner, so as I said, a 180lb spring will have a frequency of 1.97... pretty stiff but about what I would like... near the 2.0 that Puhn says is a start for a race car.

Now, I need to wait for Daryl to get his ride height posted once his springs are delivered and mounted. Then it's buy time for me. My frame is currently 3.5 inches off the ground (with 21inch tall wheels/tires... 195 55/14s) and sagging rear comp springs. I would like it up about 1 inch or so from that. Anyone have measurements of what their car is, stock or otherwise? What size tire/wheel combo?

[Daryl Smith]

Composite Springs arrived today!
According to my digital bathroom scale (which measured a new stock spring at 22 lbs) these springs weigh in at 7.1 lbs each!
Have some work to do tho, the supplied bushings are too wide and made for a 1/2" bolt whereas ours are 12mm.........

Scott said something about a Jeep bushing, which I am going to look into, But I'm open to other suggestions.......................

Will try to get some pictures up later tonight.