Hi all,
I am looking for some set up info for a Datsun 1600 race car running 15x8's (225/50/15) with:
Rear: R180 3.9 locker, Datsport adjust rear crossmember, 100lb springs and old shockers, Wolf Creek axles
Front (pic attached): T3 coilovers and camber tops, Nissco adjustable front control arms, Nissco adjustable Castor rods, all New Nolathane bushes everywhere, whiteline
swaybar, whiteline strut brace etc

I would like to know as a set of data:
- optimal ride height front / rear (ideal roll centre?)
- camber / castor / toe in / out front & rear
- best springs / shockers combination (incl rates and settings etc)

Any information or advice is appreciated that will get this puppy to steer (SR20DET w / 240rwkw).

Thanks !!!!

Got a photo of the current ride height? What are you running in the car (interior?) Do you have a cage?
What will the car be used for?
What tyres are you running (are they semi's or full slicks?)

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

Hi - ride height photos attached (15 x 7's with 195/55/15's).
Interior is only bare minimum left i.e. dash, door skins etc. Full Meridian MS steel cage with carbon fibre race seat.
Car is for Improved Production circuit racing
Tyres will be Yokohama AO48's 225/50/15 on 15 x 8's with -4mm offset

is that helpful?

Yes it helps.
Got a few more questions:

What camber/caster and toe are you running at the moment? Looks like you are running around 3-4deg neg at the front. What about the rear.
How close are the bump stops on the shocks you are running or that is, how much suspension travel do you have before you hit the bump stops?
You may be bottoming out your suspension around a corner and loading up specific wheels in the process.

When you say the car is not turning in, is that under power or brakes? Can you provide some scenarios or corners on race tracks (sandown for example)
What does the car do? Do you understeer, or does the back end come around? Do you have any photos of the car in action? (do you lift inside wheel for example)
Do you run a rear sway bar?

There are heaps of variables which would make the car not turn in. Tyre pressures spring rates etc. etc.
I would be running at least 270 or 300lbs/" on the front if you have 1100's on the rear.

2mm toe out on the front
-3 or -4 deg neg camber for front depending on track conditions
2.5 to 3.5 castor (depending on what you can run the more the better!)

2mm toe in on the rear
and as close to 0 deg neg on the rear. Some like to run slight negative (0.5), but this depends on tyre temps etc.

This is what I could remember off the top of my head.

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

I run 4.5 neg camber on the front, 3.5 caster (the most I could get without modifying the guard) and zero toe. Front sway bar is 22mm (from memory). I'm not sure that the toe I run is ideal, it tends to dart around under heavy braking. I run 375lb front springs and Tokico Prodra-G green rally shocks - maybe a little stiff, although I think if I went softer or lowered it more, I'd have issues with it hitting the front bumpstops (which it tends to do on one particularly bumpy righthander at Wakefield Park). I've cut down the bumpstops to give as much travel as possible with the 240K struts.

Rear is 1.5 neg camber and I can't recall the toe. Rear springs are cut down 750lb springs (from memory), so probably ends up somewhere between 800-900lb, and Tokico Prodra-G Gold rally shocks. I also run a rear sway bar. It doesn't run an adjustable rear.

Ride height looks to be similar to yours, and I run the same size tyre (195/55/15). Yours doesn't seem to have quite as much front camber ? I found that winding up the camber and caster really made it turn in nicely.

I quite like the way mine handles now (although its taken a while to get there), the only complaint is that since I fitted the rear sway bar when it does let go at the rear, it lets go very quickly and is a bit difficult to catch. Previously, it tended more to understeer and lifting the inside front wheel, but progressed to oversteer more "gently". Next mod is heavier rear springs and remove the sway bar to see if that helps. It is definitely quicker with the rear sway bar, but just feels a bit more "on the edge".

I don't have a side-on shot handy, but here is how it currently sits. The last shot shows it cornering nice and flat, prior to installing the rear sway bar it would have been lifting the inside front in that spot, especially under power when the outside rear squatted down badly.

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1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

One of the questions your problem raises for me is - Is the front wheel offset really -4mm? The original wheel offset for stock Datsun 1600 steering geometry is +20mm. The standard rim is offset 20mm outward of its hub centre line. It appears there is little clearance between your tyre and your spring, which looks like it is a 65mm diameter, so -4mm offset may be possible.

If you have a -4mm front wheel offset, your front track width would be 48mm less than a stock 1600? (tyre centre to tyre centre) Is this correct? Your track would be increased from this base figure if you have extended lower radius arms to give more negative camber.

These changes can play havoc with steering geometry and you may have significant bump or roll steer. Bump or roll steer will cause the car to feel unstable under braking, cornering, or driving over bumps such as raised concrete edge strips.

To check for roll or bump steer, remove the spring and move the suspension up and down through its full travel at straight ahead, and turned in each direction. If your wheel changes direction as it travels up or down facing any of the directions, you have bump steer.

The other steering problem you will have is if you mean by a "locker" diff - it is welded. A welded diff centre will give you understeer under power in turns, if you have a well sorted suspension that puts the maximum amount of rear rubber on the road in a turn. Rally cars dont suffer this problem as much as they run on dirt/gravel, so they have a lot less grip. An LSD is better - but $$$.

Another check to make is how much suspension travel you have when cornering. If the struts are bottoming this will throw you around on undulating surfaces.

Hope all these responses your getting will get you going fast - good luck.

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RichardC
SSS016

Will try to answer the various replies all here in bullet point.

The photos do not show the new set up. My description and questions are based around a suitable set up given the specs I have mentioned i.e. the -4mm offset wheels (-ve offset makes the track wider) are not shown in the photos but are coming and will live under flared guards.

- no rear bar (yet but it probably will happen)
- the car does not have a bump steer issue
- the car does have a locked diff (welded) but I dismiss this as a handling issue as I know of other cars that are very quick that have a locked diff

Dave - thanks for the set up info - will transfer some of that knowledge.

SR20Datsun:
- do not have current specs as I am waiting for an alignment
- suspension travel will change with new wheels so not sure (the car is very stiff and shows no signs of hitting bump stops)
- not turning under power i.e. coming on to the front straight at Phillip Island it pushes (understeer) badly and the back will want to come around if pushed
- no rear sway bar (yet)

The photos I have all show the car without load although I am told there is a lot of pitch and roll (front to back) under brakes as seen over Lukey Heights at Phillip Island.

Again - thanks for the feedback.

That reminds me - one thing I didn't mention is that I run 15x6 +30 offset rims. This offset was needed to get the rims in under the guards due to the LCA's having around 35mm welded into the length. In the past, I have tried more camber (with 10mm longer LCA's), but this was with different wheels / tyres / struttops so its hard to compare. Current camber is set at the maximum I could get with my tyre / strut combo (and without flaring the guards). The current wheels are chosen to pull the tyre in as close to the strut tube as possible, but I still don't have much guard clearance. I'm interested how you're going to fit your wheels / tyres under the guards ? Or are you running flares ?

And I run bumpsteer spacers (as you seem to by the pics), which cured a bumpsteer issue mine had.

Ohh, and I run a clutch-type LSD.

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1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

This is what i run

Rear
1100 lb rear springs
No rear bar
Tokico Prodra-G Gold shocks
-1 camber
8mm total toe in

Front
275 lb coilover springs
70 lb keeper springs
40mm roll center spacers
-3.5 degrees camber
0 degrees toe
22m adjustable bar on the softest setting

The car does not handle right.
Still understeers. That why i added so much toe in on the rear.

I think it has something to do with the roll center on the rear. With the low 1100lb springs the trailing arm angles up quite a lot.
Does anyone know how to calculate the roll center of a semi trailing arm system??
My next mission will be to try and raise the rear crossmember up as far as possible and relocate the trailing arm mounts up to get the arms as close as possible to horizontal at normal ride height.

My brother now owns the second fastest zed in aus(he did not build it). It uses quite an interesting suspension theory.
It runs super super stiff springs all round a standard front swaybar and no rear bar.
I think it runs 900lbs rear and 800lbs front springs rates.

I think i might try this on my 1600 soon. Im going to get custom 1500-1600 lb rear springs made and run 400-500 lbs in the front.
To get semi trailing arm suspensions to work the thery has always been to get them as close to horizontal as possible and stiffen with heavy springs to limit travel and prevent excessive camber/toe changes.

My 1600 height

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Circuit Race 1600 in the build

Id love to see a pic of the car with the 8's on it

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Here's a basic way of calculating roll centre for the rear end.

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

I have unknown front springs (ex rally car), 24mm front swaybar, RCAs, koni front shocks, T3 caster rods. -3.5deg camber, +4, 4.25deg caster (more on passenger side- guards are cut) and 1mm toe out.

Rear is datsport arc and 1100lb springs, no rear swaybar. 2mm toe in, -1.5deg camber. Wheels are 14x7 3p all round with 195/55R14 tyres. I also have a 1.5way clutchpack LSD (KAAZ).

Handles alright on track but sucks at khanas...


You're doing it wrong Lampy, the smoke is supposed to come off the REAR tyres

I put some 15x8 +0 Superlites with 195/50R15s on mine a few days ago, rear end was fine, but front hung out of the guards about an inch. Pity, because they looked awesome!

haha the old l20b is lacking in the grunt department for that kind of fun stuff

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Circuit Race 1600 in the build

Thanks for all that guys - I will post some pics when the new set up is on the car and will keep coming back for info on this thread and will post what I learn from the work that is coming up on mine.

Would like to hear more about shockers and shocker rates that you guys are using with those springs too....

Cheers