Spring Rates on a Datsun 510 ITC

[Stan]

Hey guys,

I recently purchased a '72 510 ITC car and am wondering what spring rates you guys recommend for it. My car has springs, but I'm not sure what rate they are, or what rate I should expect to use.

TIA, Stan

[Harry]

I'd call who you got it from and ask him what the spring rate are. Does the car have coilovers in the front? If you lucky the rate may be on them.
I use a pretty darn light setup on my 510. I use 165# Carrera up front and on the rears I use the stock front springs out of a early Datsun 2000 Roadster cut to achieve the 5" ride height. I had to find a new set when they add the driver to the car. A lot of guys I've talked to use the racing (862#) springs for the front of of the Roadster in the rear of the 510 with about 225# up front.
I'm like you I'd like to get some input from all over on this post.
Harry

[Stan]

I dug through the paperwork that came with the car after posting my question and found that it has 250# in the front and 850#. This sounds way off to me. I looked at the BMW guys on this list, and they are running from 550# front and 250# rear to 500# all around. These numbers sound much more reasonable to me, but I'm interested in what anybody else in running in their RWD IT car.

Thanks! Stan

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Stan
1972 Datsun 510 ITC
1995 Ralt RT-41 FA
RPS Motorsports

[Knestis]

This is going WAY back in my memory (pre 5.25" floppy!) but I seem to remember that "in the olden days" 510s had to use really stiff rear springs to control the wacky motions induced by that semi-trailing arm arrangement that they have.

The thinking was that any potential benefit of a more pliable rear end were offset by the toe/camber changes that resulted over anything like reasonable travel.

It is never going to be as simple as looking to other makes/models of car - sorry!

(Big FWIW.)

Kirk

[Stan]

While you're right that one can't blindly follow the example of a different make/model, in the absence of reliable, specific information about one's car, looking at similar cars is a good place to start. I looked at the early BMWs since they have similar layouts and use similar technologies.

Kirk mentions using stiff springs to control the "wacky motion" of the 510's rear suspension in one paragraph, and then suggests they're used to eliminate camber/toe changes with displacement in the next. These are two very different situations. One is a bushing material issue, while the other is a geometry problem. I'll have to get the car up on jack-stands and run the rear through its range of motion to get a picture of its toe and camber profiles. While I'm there, I'll take a good look at the bushings.

Anybody else have any experience or thoughts they can share?

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Stan
1972 Datsun 510 ITC
1995 Ralt RT-41 FA
RPS Motorsports

[eh_tony!!!]

Stan, Had a 510 for a few years down here in SEDIV. One of the first things we did wa to burn out the rubber rear subframe bushings and use metal bushings in place., Second was to slot the inner suspension arm mount. FOr the suspension, we used 300zx shocks in front, 510 in back (konis). Don't remember spring rates, but I think that the front springs were cut 300zx units. Watch you front spindles, they tend to bend if gator teeth are abused.

[benedash]

Stan.....
Been racing a 510 for about 6 years now....
Looking at changing my springs right now (or at least for next season) Would love to open up a conversation adn explain my theories etc etc. Basically the car has been running on 850's (rear) for about 4 seasons. I feel these are weak and need replaced adn would like to go stiffer. My brother, who also co-drives (another class) feels that the springs need to go softer. Swapped in an old set of 800's for the last race of the season and we both gained about 4/10's hmmm.... colder or just a better setup. Talked to other dimers and have heard from 850 -1000 in the rear.
Email me at [email protected] to chat.

Hank Bene

[Stan]

Thanks Tony and Hank!

I talked to the guy I bought the car from and he told me that much of the present 510 "knowledge base" derives from work that Cook Motorsports (Northern California) did for Datsun back in the 70's. Their setup, with soft front and stiff rear springs, has apparently become something of the gospel in 510 circles.

I am curious, though, how your times compare to other dimers in your areas, guys? Harry, how about you? Sounds like your setup is a bit softer than the usual. Your times comparable, all things considered? Any strange behavior or "whacky motion" to report?

And Tony, I take it that "gator teeth" are curbs...?

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Stan
1972 Datsun 510 ITC
1995 Ralt RT-41 FA
RPS Motorsports

[This message has been edited by Stan (edited December 27, 2001).]

[EDP]

Stan,
Nissan comp rear springs were 770 lbs. I had a ITC 510 in NER 10 years ago. We used the 770 rears and 350 fronts 2 1/2" coils.
Used the 1 1/8" BRE front and 3/4" BRE rear sway bars. The car was fast. I sold the car in 1992 and it went from the eastcoast to the westcoast. Never seen it since. Used alot of DP racing parts form CA. You can buy the rear crossmember pre slotted.

Ed

[Stan]

Thanks Ed!

350/770 is a long way from what I would expect, but it certainly sounds better than the 250/850 my car has.

Any idea where to get those pre-slotted rear cross-members (in case mine isn't slotted)?

Thanks!

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Stan
1972 Datsun 510 ITC
1995 Ralt RT-41 FA
RPS Motorsports

[Stan]

Has anyone here actually tried spring rates closer to that seen on other front engine, rear drive cars? Say around 450/300 front rear? If so, please tell us how well it worked.

TIA,

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Stan
1972 Datsun 510 ITC
1995 Ralt RT-41 FA
RPS Motorsports

[EDP]

Originally posted by Stan:
Thanks Ed!

Any idea where to get those pre-slotted rear cross-members (in case mine isn't slotted)?

Stan,
I will look around for a phone number on the rear crossmember. May take a day or two.
I have a CRX in ITC now, but I think that the 510 is a better car. Here I New England a rust free 510 days are long gone.
They are great little cars, plus alot of the B sedan stuff (look in the old "How to hotrod a Datsun" book) is close to the IT cars now.

Ed

[ronpapworth]

Hi Stan,
Just read thru the posts and not sure if I can help, but will toss my 2 cents in. I have built an 87 300zx into an ITS car and am running 450 up front and 350 rear. These rates were suggested by a car builder out of atlanta and seem to give the car a real good feel compared to stock. My car is a pig, over 3000 lbs, and I don't think the 510 is that heavy, but we have a similar rear suspention. By lowering the car you create that nasty negative camber in the rear. The bad part is under breaking, that negative camber lifts up and causes a shift to almost positive camber, under stock conditions. You can imagine what that poor tire patch is going thru. Rule #1 in a Z has always been "finish your breaking before you turn" because of that. I find with 450# up front(stock is around 160-180#) that the front end doesn't dip as much under braking which prevents the rear from picking up. Oh, here is a link for slotting that crossmemeber before I forget...
http://www.nexcent.net/datnet.org/link_0001.html

There are a few pages of people who modify the heck out of these cars. Hope this helps.

[badal]

Stan,
Design Products in Huntington Beach, CA does the crossmembers. 714-892-1513.

What is wrong with your current set-up? Does it push? Loose? Bottom out?

450/330 would be a disaster. It would be 4 times stiffer than stock up font and softer in the rear.


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"Bad" Al Bell
ITC #3 Datsun 510
DC Region MARRS Series

[Stan]

Thanks Guys!

Thanks for the info sharing. I just recently purchased this car and haven't had it on the track yet. However, I did talk to the seller, who said that the car drives fine on the straights, but he reports sawing the wheel constantly in the turns - which tells me something is amiss in his front/rear balance (250/850 spring rates).

I took a quick look at the rear setup and see what Hank and others were talking about with the spring locations needing a conversion factor (since they're not acting at a 1:1 ratio). Sounds like Ed's numbers of 350/770 are about right on the mark.

I checked...the rear crossmember is slotted...and I have the adjustable front and rear anti-roll bars...

This is gonna be fun...

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Stan
1972 Datsun 510 ITC
1995 Ralt RT-41 FA
RPS Motorsports

[Stan]

Al,

Thanks for writing such a great response. Sorry I didn't reply in kind...but let me make amends by answering your questions directly.

The car isn't too far off the pace. In September it ran less than a second off the ITC record at Thunderhill (with a self-decribed "middle of the pack" driver). However, the guy I bought it from says that the front of the car rocks mildly from side to side (causing him to "saw" the wheel) through turns. This sounds to me like there is an imbalance in the spring rates causing the front to oscillate in turns as the imbalance causes the front to first load then unload. He feels this and counteracts with steering wheel inputs. Since he owned and raced the car for 6 years and never changed the springs in that time, I suspect he simply got used to it and drove around it.

I am interested in what spring rates you run in your car (since we'll never meet in combat, so to speak... ) If you are so inclined, please write me offline at [email protected] - I will keep any info you wish to share with me strictly confidential.

Looking under the car, I now understand why the rear springs are stiffer than normal, and will confirm the conversion factor by measuring the moment arms. So yes, 450/300 won't work. I agree. But I think 250/850 is off by enough of a margin that it can be improved upon.

Thanks again!

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Stan
1972 Datsun 510 ITC
1995 Ralt RT-41 FA
RPS Motorsports

[EDP]

Originally posted by badal:
Stan,
Design Products in Huntington Beach, CA does the crossmembers. 714-892-1513.

Hey Al,
That the number. What happened at the ARRC this year?

Ed Pacitto

[badal]

Stan,
Just to set your mind at ease, the Factory Racing suspension system sold by Nissan Comp has rates of 218/778.
I use 225/approx 900 (cut roadster comp frnt springs.
I'm not sure this is ideal, but it seems to work OK.
As far as the oscillations you describe, I would look for:
-Front sway bar binding on frame.
-Struts bottoming out/hitting bumpstops
-Loose/worn/bent parts
-Drunk driver

I'm at [email protected]

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"Bad" Al Bell
ITC #3 Datsun 510
DC Region MARRS Series

[Stan]

Thanks Al!

I'll check out those issues you mention, particularly the last...!

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Stan
1972 Datsun 510 ITC
1995 Ralt RT-41 FA
RPS Motorsports

[Harry]

Stan, I'd take Al's advice. The spring rates you have are fine. The difference in the front to rear rates is because the rear springs are located furthur inward away from the wheel centerline thus changing the amount of leverage required to equal the same rate as the front spring located closer to centerline of the wheel. Fine tune with adjustable shocks and adjustable anti-sway bars. I've never had any "wacky action" in the rear due to the "exotic" semi-trailing arm rear suspension. It's was good enough for BMW.
As far as lighter spring rates, it comes down to a drivers preference. Lighter springs have some advantages and disadvanages. I'm sure others can post data on using different spring rates for different types of tracks.

Harry