Suspension Advice Needed

[Rush]

I would like to upgrade the suspension in my car. If I recall correctly, when I bought it in 89-ish the guy told me the springs were cut (front & rear) and it does have clapped-out air shocks in the rear. When I did my build I put new KYB strut inserts up front. I know very little about suspension but I feel like coilovers are really something I don't need since, for my driving, it'd be a set-and-forget deal & the total adjustability would be a waste of money, honestly. I don't track the car and rarely drive aggressively. I do want a nice positive feel so it's not squishy but I'm not looking for a covered wagon feel, either.

I think I would be happy putting in proper (maybe adjustable) shocks in the rear and new, proper rate, lowered springs all around. I have read and read and really all I've learned is the springs for the rear need to be 2.50". With basically no information I'm having a heck of a time looking up springs & stuff. Eiback seems to have a good reputation, but their website is per application & I can't find the 510.

I'd appreciate some education, suggestions, and part numbers if you've got 'em!

72 2 Door
L-16 mild performance, I guess you could call it
4 speed
Front and rear sway bars
13" wheels

This is how to car sits right now (sans the stripes. Valance & bumpers added )

[Not Now]

Datsun Garage sells some Vogtland lowering springs. Never tried them before, but they are a well known brand in the German car community. Rear shocks I have had good luck using the KYB AGX from a 1982-1992 Camaro. Koni also make a spot shock for the rear of the Camaro, I'm going to try those at some point.

[Rush]

I'll take a look there for the springs. Thanks!

I contacted Eibach, and told them what I had, they told me they didn't have springs for my application. Ummm. Ok then. Typical of someone who only knows strictly per application, not experience or size.

I installed a set of KYB AGX shocks yesterday! What a difference!
I did have to slightly clearance the mount so I could have the dial facing outward because otherwise it'd hit my exhaust & I didn't really want to bash in my new custom-made exhaust for clearance.

Ratty clapped out old air shock:


New AGX:

[bertvorgon]

Funny, I as going to type a reply this morning, as I had been thinking about your question.

Others have answered some so I will leave it at that. Not sure what you meant on the "2.50"?

The stock springs can be cut of course, one has to make sure you have NOT lost travel..and could hit the bump stops. Especially on the REAR. Do not hesitate to cut an inch off the rear bump rubber!

The front bump rubber, if you put it back on, we cut down to 1/2" thick.

As you have anti-roll bars, that is a good thing, that helps the MOST with cut springs in terms of body roll control. The cut springs MARGINALLY increase the spring rate. STOCK spring rate for example was 89.5 lbs/inch at the front and 357.2 at the rear. My 73' came with 95 lbs/inch.

I figured out that Pete Brock of BRE / Interpart, fame actually used the FACTORY taxi springs for the Interpart suspension package he put together in the early 70's, painting them ORANGE. The reality, as tires got better, as his(factory) spring rate was only 116 Lbs/inch and 357 for the rear. While this helped from stock, it was in no way near what was really needed to fully control body roll on an aggressively driven car, specially in true Solo and race use.

SO...on I/ we went to really find what spring rate truly worked. I guess my cautionary tale for you, as much as you maybe want to lower the car more, is TRAVEL needs to be considered, so you NEVER hit the bump stops except under the most EXTREME bump.

The other issue too, becomes as springs get firmer, the shock needs to be able to control that. Likely where you are at, at this point, is to KNOW how much more you could cut the spring(s)or, buy shorter springs and still have adequate travel. Also, as you might lower the car, will the shock itself not run out of travel. With our race lowered cars we needed a much shorter shock at the rear and of course the fronts have shortened struts, with an appropriate shorter shock.

I'm sure you read the suspension thread, as a refresher we run 300 lbs/inch at the front and 1,200 lb's/inch at the rear. You could ASK the company, what is their spring rate?

Not sure what your FRONT ant-roll bar diameter is, but big is better to an extent. None of us here run a rear bar, just FYI. A big/bigger anti-roll bar decreases body roll onto the loaded front tire, so in a lot of ways it does decrease understeer, by decreasing the weight transfer to that corner of the car.

Better handling...do not EVER underestimate what a true performance tire can give, I'm sure you understand that.

Anyhow, hope my rambling maybe helped a tad.

[Rush]

Thanks, Keith!

I'm not really looking to lower the car any more than it is. If it happens to go a bit lower with the new setup, that'd be ok but I'm not looking to be in the weeds; our roads are way too crummy for that! I don't know how much was cut from my springs but I don't seem to smash down or bump off anything in the suspension so I'm guessing it's ok.

I now have new strut inserts up front and the AGX in the rear so I hope they will accommodate a new set of springs. I mostly want to renew the ride because those 52 year old springs have probably seen better days.

I have read nearly all of the suspension thread to try to glean some info that would be useful for my situation. So much has to do with coilovers, it's sort of irrelevant to me.

What I meant about the 2.5 is the ID of the front springs. So what I think I've learned is that I can go with 8" long springs, front & rear; with the front being 2.5" ID and the rears being 3" ID and the front rate maybe 275 and the rear about 950? If those specs are about right, I can order per size from Eibach but they're listed as "coilover springs" and I don't know if that's different than "regular" springs.

My front sway bar is 1.25 maybe? I'd have to measure again. The rear is 3/4 & I just put new brackets & bushings on it last night. One bracket has been missing probably the entire time I've had my car so I'm curious if it'll feel any different now that it's actually doing something back there being fully mounted. I'm installing new torsion rod bushings today, so I'll take it for a spin later. IF it's not snowing!

[bertvorgon]

2.5 ID? Seems too small to me on a stock strut?!

if in reality 275 and and 950...that would be ok I guess.

Specialty's "street" suspension was 200 and 900 if I remember right.

My front bar is 1 1/8"......

Not sure I can comment on the free spring length...the HARD suspension free length was 12.99 for what that is worth. So if spring rate is 275...that would theoretically work as the spring would have less compression and not drop car in relative lowering, if that makes sense..

[Rush]

I thought I read 2.50" ID. I'll try to find it again; maybe it was talking about a coilover. I should have measured when I had the struts apart.
200 & 900 combo must be a good one if that's what they designed. Maybe I'll go with that. I just don't want it to ride like a bag of oatmeal (or a skateboard). Ugh. This is difficult.

I just took the car for a drive after the sway bar bracket and new torsion rod bushings. It feels good and seems to have eliminated the slight sag I had on the left side rear. I have some weird sort of soft tick noise on the passenger rear when I hit bumps. It sounds like when the tires throw a tiny pebble into the wheelwell except it perfectly coincides with bumps. So, something is loose but I can't find anything in the wheel, wheel well, or even the trunk. NO clue what that can be but it's driving me nuts! My car has no clunks, rattles, squeaks, etc. so this is especially annoying.

So the stock front spring was 13" & 89.5?

[bertvorgon]

Yes, "free height" was 13" and spring rate was 89.5 inch/lbs, very soft considering what it took to really make a 510 handle.

Re your noise..just double check that the shock bushings really do separate the shock body from the mounting pin, IE in the center of the 2 bushings where they meet, that they could NOT be hitting the steel mounting "pin"..this would be the bottom mount.

This picture, if you can relate, is my 1972 sedan at Boundary Bay airport. It has the BRE/Mulholland suspension in it, which is the 116 inch/lb springs. THAT amount of body roll was unacceptable, exacerbated by race slicks due to increased stick..loading, on the right front tire. The anti-roll bar was not all the big, all things again considered. By the early 80's, by extension, we had to go way higher on spring rates and roll control.

So, you can see why the spring rate(s) got upped to the levels we now consider normal for a performance suspension, ever more so as today's street legal race tires have more grip than could be imagined in the 70's and 80's.

[Rush]

Rad pic! I bet it felt like it was going over!

I'll check the shock mount. Thanks!

[Not Now]

200/900 is a good spring rate combo. If I'm trying to make a comfortable yet fun to drive 510, I'm usually in the 200-260 in the front and 800-900 in the rear. For the rear spring you can use a 3in ID coilover spring and cut one of the ends off. Fits perfect in the back of the 510. There is a fun article in Motor Trend called Datsun 510 Rally Beater, he goes into more detail about this. The last 510 I build I used a 400Ib 16in long spring and cut in half which gave me 2 800lb 8in springs. At least I think it was 16in long, its been awhile. It did sit a little lower than I liked so I ran a urethane spring spacer. As for the front I'm no help, I always convert it to a coilover.

[Rush]

Thanks so much for the info, NN!