General suspension questions

[Jezza_hr]

Hey guys, I'm trying to gather some suspension info if you're willing to help out?

I've been running quite a stiff set up on the 86 since I first got it and I'm looking to soften up and heighten the ride a bit for road use as it doesn't get enough track action to warrant the intensive spring rate that it's running and it's getting to a point where I think other components of the car are taking a beating as a result.

Now, my only real gripe is, I don't know what spring rates on there, although I would hazard a guess by how little play there is in each corner it's running the popular 8kg front and 6kg rear spring rates. I would like to aim to 6 front and 4.7 rear with some added height to reduce the skittish behaviour and grounding I sometimes get at the lowest point of the manifold. But it's the question of where to start.

My car is running a front coilover conversion (supposedly TRD but I see no mark to resemble this) and uprated springs and separate shocks at the rear (These do look like TRD). Now, I would like to keep the coilover conversion at the front and adjust them appropriately to gain the right ride height, comfort and performance but I need to make sure the springs at the back are running an appropriate ride height to maintain an equal balance throughout. I also want to be able to adjust the corner weight appropriately to make sure everything seems to match up, although I'm guessing this is a little bit more difficult when only running coilovers at the front?

I have been looking at the TRD 4.7kg springs for the rear as the appropriate ones for the job (correct me if you think there is anything better value out there, otherwise let me know of the cheapest place to get a set of TRDs if you know of a place) but I don't know where to start to get springs for the front coilovers. Are they pretty much all of the same diameter or is that wishful thinking? I also seem to be having trouble finding them being sold separately from an entire coilover set.

Any help with these questions, as always, would be greatly appreciated. I also wouldn't mind hearing other peoples set ups to get a feel for the best road performance, if you care to share?

[NoHachi]

Hiya,

Dunno what would be the best setup for you (everyone is different), but here is what I did.

Rates:
I set the springrates to match those of the faster cars on the nordschleiffe. After some calculating that comes to 5.8kg/mm and 4.5kg/mm. Close to the rates you mention, but with some more room to firm things up for ultra-smooth tracks with stiffer swaybars. 6/4.7 should be fine.
You'll have to measure the inner diameter of your springs, depending on what it is you can find your springs cheapest at Faulkner or Rally Design:
http://www.dfaulknersprings.com
http://www.rallydesign.co.uk/
No TRD logo, thus less then a quarter of the price. Good enough for plenty of racers to use them. dFaulkner might be able to do you a rear set as well, otherwise go TRD if you must.
You'll need approx 9" free length at the front.

Height: You can keep your coilovers at the front no probs. With these rates your total stroke will be approx 100mm front, 120mm rear. So 5 to 6cm's either way. When the time comes to change the springs, remove springs from the struts (or car in the rear) and put everything back on the car. Put a jack under your wheel and jack the wheel up until the wheel hits the inner fender. Do some hammering for clearance (if you want to do this), jack wheel up until it hits again. Also make sure its set close to the camber you plan on running. This is max possible compression travel
Now measure the distance from the top of the wheel arch to the hub centre of your wheel and scribble it on a piece of paper (we'll call it M1).
Drop the jack down untill the wheel is hanging in the air freely. Again measure between hub and arch and make a note. This is max rebound travel (M2).
Subtract the first measurement from the last and you have total available travel dictated by your chassis.
max.travel = M2-M1
If your car is anything like mine it'll have close to 100mm of travel (no coincidence that that is the same amount of travel that the springs allow, usually you plan them so they use all available travel at max lat.accel.).

A good starting point for height is to use around 60% of total travel for bump and 40% for rebound. That way, when you are cornering at max lateral acceleration. The suspension is fully compressed, but you still have around 10% of travel left to absorb road irregularities (warning -> this leads to grip..if you want it to slide, go ahead and set things at 50%). So take 60% of total travel and add it to your first measurement.
height = M1+0.6*max.Travel

After that, throw the springs on and drop the car onto the ground. Measure the distance between hub and arch and adjust the spring perches until the car is close to the variable "height" all around.
My guess is that TRD did their home work and the rear springs will be close to the sweet spot.
From that height you can start making small changes so that the corner weights are in the ballpark and the car has a bit of aerodynamic rake (lower front then rear).

End result: Still an utterly stiff ride..nowhere near wallowy or slow reacting. However the car now rides over sharp road irregularities instead of crashing over them. Its not exactly slammed, but not quite back at stock height either. Small price to pay.
Haven't taken it to the track yet, but my guess is it will be much easier to drive. She communicates a lot more (old setup was 9k/7k dorifto). On bumpy tracks like the ring its no contest: the forgiving setup is faster for everyone except the people with thousands of laps under their belt.

[Jezza_hr]

Nohachi that's brilliant, you answered most, if not all my questions in a rather straightforward logic, I applaud you sir and thank you

[Jezza_hr]

Looking about it would seem the TRD springs are a fair old drop (2.25" - 2.50" If I'm not mistaken) and I would rather have something between 1.5" and 2" preferably. What drop are you running Nohachi and would you recommend it?

Also if you have the specifications (ID and length) of the rear springs you use it would also be of help to get the right idea.

[NoHachi]

Dunno about the drop since I've never actually seen a hachi at stock height. I could go and measure the hub to arch distance though. You won't have much use for my rear spring setup because I'm running the t3 coilover rear. Makes spring selection a lot cheaper.
Ask Mux what he had on his car. It was similar to mine but with a stock rear spring setup.

[Jezza_hr]

Thanks again for the assistance fella. I've spoken with Mux and will be moving on from here :wink:

[Mux213]

Just for others who may be interested. I'm far from an expert so take this advise as its given, just my personal opinion.

My setup was 6.25 front, 4.5 rear with stock sway bars and fully adjustable shocks, and I loved it. My personal "feeling by ass" opinion is that anything over that for our light little cars will just end up bouncing all over the place unless you're on a smooth race track which may be the only place going stiffer makes sense (and I've learned that Holland seems to be the only place in the world that may have roads smooth enough to make this acceptable on a road car).

If possible I'd actually go slightly lower and in that contradict what most people seem to be saying, something like 5kg front, 3.5 to 4kg rear and compensate with adjustable sway bars and adjustable shocks depending on whether you are out on the race track, want to do some drifting or are just cruising with the family on the open road.

Having stock sway bars btw for me was simply that I hadn't gotten to that upgrade and they were on the top of my list. Being taken out by Adam over the weekend and him telling me about his experiences with his adjustable sway bars made me appreciate what a proper upgrade this is for your car and it was very interesting to hear what happened to his car when his setup was made to stiff.
Both me and Djexor had a similar experiences with our HTS shocks, setting them anything over half their stiffness and the car would noticeably start loosing grip on anything but a smooth surface.

There is a reason that cars have springs and shocks and its not all comfort, handling isn't about getting the stiffest setup you can find. Its all about finding a balance and keeping in mind what your road conditions are.

So far my two cents.

[Jan Pedersen]

I use 6/5.1 kg/mm with TRD adjustable dampers. This works great for me. Full soft for road and harder on track depending on surface and weather. Grip is good and comfort isn't too bad imo.

[Jezza_hr]

Without being able to try multiple combinations, it's not going to be easy to know my ideal setup, therefore I'm willing to go with recommendations and searching around 6kg/4.7kg seems to be the frequently used combination for a road/track set up. My only dilemma at the moment is finding the right springs for the rear.

On my previous AE86, I was using 40mm drop Fensport springs, which were comfortable enough but probably not quite low enough in my opinion (although we are talking 4 years ago on a car with standard anti roll bars) so I wouldn't mind 50mm drop springs which wouldn't be as dramatic a drop as TRD's supposed 2-2.5" drop, which is what I believe I'm running right now.

If anyone knows of a 50mm drop rear spring with a 4.7kg rate, please do share, it would be of great help.

[Mux213]

Don't forget that the fensport ones (if they are the ones I have in mind) are progressive springs so that gives an entirely different feel all together.

Sourcing springs is the difficult bit these days. In that way I love nohachi's approach and I believe Jamiemirror goes the same route with his, get coilovers with standard diameter springs and suddenly the whole world opens up with cheap springs so you can mix and match springrates to your hearts content.

Actually, can't believe I forgot about those, contacting Jamiemirror defo is an idea, no idea if he's still fabricating but he was working on a whole bunch of suspension parts the last time I talked to him and seeing he is in Europa shipping should be loads cheaper too.