S13/s14 Subframes/roll Centre/squat - Best Option For Grip

[No Crust Racing]

S13 which is about to get some Cusco Caster arms, Freshly painted R32 LCA's with new inner bushes and Nagisa Roll Centre adjusters up front. (has coil overs, and adjustable camber and toe arms in the rear). Also have Whiteline 27mm adjustable front swaybar and R32 GT-R rear.

What's the best option for the back? Was going to get solid subframe bushes as they apparently raise the subframe up and help fix Roll Centre in the rear (GKTech kit or something similar). It was suggested I go S14 rear subframe as it apparently has better geometry. that apparently means adding some spacers to rear toe arms as the mount on the S14 subframe is wider, but apparently everything else is the same, which is odd as I thought the S14 subframe was wider by 10mm each side or something, which would mean swaybar doesn't fit?

Thoughts? Just add subframe bushes or worth swapping subframes? I was looking at Skyline rear calipers also, ditching drum handbrake and buying inline hydro handbrake or not running one at all.

If the S14 frame is wider, that means needing spacers up front.

Edited May 9, 2015 by ActionDan

[sweefu]

I thought the S14 subframe was wider too.

Just a word of caution - I would advise against an inline hydro handbrake, they are crap and make bleeding the brakes very difficult (which will be even more annoying given you are racing - bleeding more often).

R chassis rear brakes are a good upgrade though.

Sorry, not much help, just thought I'd chime in about the inline hydro.

[No Crust Racing]

Good to know, thanks for the tip.

[bcozican]

I did my s14 rear subframe on r32 gtst but they the same as s13 cradles

S14 subframe is approx 5 - 10mm wide a side, I dont know if your std s13 arms will fit though. I had adjustable rear camber arms up top but at first everything else I used was standard s14 stuff down low (ie: toe arms and rear LCA's)

You will need offset solid bushes as you said, and I needed a S14 back plate for my diff to fit it in (shorter), also 3 out of 4 cars I have helped with doing this to have needed the rear chassis rail slightly 'massaged' up about 5 - 10 mm to clear the subframe

Im trying to get my memeory on now to back when i forst did it with standard gear but im pretty sure sway bar mounts were fine

Its 'easy' if you get the right bits and put in the time etc... but its also not as easy as you might think time wise always took longer than we thought haha

[No Crust Racing]

I have adjustable camber and toe arms.

More interested in if this is a worth wile swap or if I'm better off just throwing in the solid subframe bushes to the standard subframe and working with whatever roll centre improvement that gives (as it changes height by 10mm)

So I'd need S14 LCA's also? And you think S13 (in my case R32 GT-R) swaybar, mounts and endlinks fit?

[bcozican]

I did find improvements for rear grip by doing the swap as have others I know have done it ... without all the swanky xyz gear to measure actual improvement at our level of racing you'll have to go off other peoples opinions and evidence though unfortunately

Ive had it for so long now I have to try and remember the changes from one to the other but I do remember the difference going from one to the other

I think s13 rear LCA's would be same length as r32 ones? if so id see if you can source some std s14 LCA's - shouldnt cost much

This is going by memory but im pretty sure when I first put in the s14 cradle I didnt have to adjust anything to do with my swaybar ..I did have whiteline sway and endlinks though that did have some adjustment in it...maybe someone else can confirm there ?

[GTSBoy]

5-10mm of sideways angle in an ARB end link isn't going to make it stop fitting. ARBs are pretty forgiving in that regard.

[Roy]

Having done a cradle swap i have formed the opinion that provided your S13 cradle is free of damage/cracks then just modify the std cradle pick up point. Far simpler and cheaper. Things like exhaust brackets, handbrake cable mounts etc all need to be changed if you are doing the later model cradle (i did R33 into R32)

Also...i think you will find the track increase is in the wheel offsets...not the actual suspension. Well at least that is the case for R32 GTSt and R32 GTR and R33s too. The wider track of the GTR is from wheel offsets of 17x9 +30 vs 16x8 +30

[warps]

Just a word of caution - I would advise against an inline hydro handbrake, they are crap and make bleeding the brakes very difficult (which will be even more annoying given you are racing - bleeding more often).

Not true

Make bleeding a little more fiddly, but hardly very difficult. If you know how to bleed brakes, you know how to bleed hydro h/b's. People have been running them successfully for decades.

Yes, there are better hyd handbrake options, but inline systems aren't the evil that people make them out to be.

[-oliveR]

^ Warps is correct.

I have a PBM inline hydro in my car and I do not have a problem with bleeding the brakes. The only downside is you cant use the hydro and the foot brake at the same time. Other than that it is great.

S14 subframe swap will need offset subframe bushes as its 10mm wider each side.

A 33 GTR swaybar will fit onto an S14 subframe, 32 are a little too short from memory.

[No Crust Racing]

Might just go with subframe bushes then, sounds like the easier option.

If that doesn't get the LCA's parralell I'll have to bring the ride height back up a little. With the swaybar in there that shouldn't matter too much body roll wise.

[bcozican]

If you want rear lca's level can mod your current s13 subrame by changing the pick up point ( as Roy pointed out) I have done this to my s14 subframe and created a 'ladder' system for the front pick up point with various level adjustment in it??

Is this what you and others mean ?

Also cheap otion for the front for width is s14 or r333 front Lca's also about 10 - 15mm wider per side

[No Crust Racing]

I hadn't considered that.

I'm getting R32 LCA's as I found some with new inner bushes and RCA's already pressed in. I will stick with S13 subframe and either get solid bushes or the nolathane ones with the spacers that allow the anti-squat characteristics to be changed.

http://www.nolathane...des/50-9154.pdf

Not solid but allows me to change angle and get more anti-squat. I don't know if it changes sub frame height though and the goal was to improve roll centre.

[warps]

How do you go with anti-squat on a circuit car? I know that the gravel cars do what they can to eliminate it, as it compromises traction in the loose stuff (they rely on squat to get weight transfer over the back). Is this the same on tarmac, or does it not matter as much?

[No Crust Racing]

I am only going off what I read, it's the other way around. You want a little more anti-squat to improve grip on tarmac.

[No Crust Racing]

As below - which is why I am also looking to change sub frame height to improve roll centre.

"The amount of weight, or load, transfer that occurs during acceleration is determined by three things: 1. the magnitude of the accelerating force, which cannot necessarily be changed with the same motor/gear combination; 2. the length of the wheelbase-again not a variable; 3. the height of the center of gravity of the car. The last item is influenced by A/S, and load transfer is affected by it.

A higher center of gravity means more weight is transferred during acceleration off the corners. If the car squats during acceleration, the rear becomes lower, and the overall center of gravity is then lower in the car. A lower center of gravity means less weight transfer and less vertical load that is applied to the rear tires upon acceleration. By using A/S to keep the rear of the car from squatting, the center of gravity remains higher, and therefore more weight will be transferred to the rear tires."

[warps]

I can see the reasoning behind that, but it still seems counter intuitive to me in that you are artificially loading up the rear end to prevent it from squatting. I think that the benefits of higher COG will be offset by the artificially hard rear suspension due to the AS. I know for certain that in a gravel car you want the rear end fairly soft, and when the first S13 rally cars were being built, there was a lot of concern about the anti squat in S14's, hence a reluctance to go to S14.

Not sure whether it's the lack of grip overall on gravel, or the rougher surface demanding a more supple suspension setup, but there isn't any proven benefit of AS on gravel that I'm aware of. If it has been shown to work on tarmac, then fair enough - hence my original question.

[No Crust Racing]

I am in no way qualified to answer that properly.

I am simply reading/taking advice from people far more qualified than me.

This all started when I added sway bars to my car and found the whole setup to be too stiff, I went fast enough but it was burning up the outside edge of front and rear tyres faster than it ever has, despite what would be considered "adequate" camber. I thought drop spring rates but was advised against that.

The suggestion was, get some caster up front, and raise the vehicle to improve roll centres. The alternative is get some RCA's up front and change subframe height in the rear to improve roll centres without raising the car - which is already not "that" low as it's not a fully sik drifter.

[warps]

Yeh I'm far from an expert as well - probably know just enough to be dangerous.

Was just interested to hear opposite strategies between gravel and tarmac. They certainly have their differences, so it's feasible that what works for one doesn't work for the other. Gravel also has other limitations to the suspension design (essentially the best rally setups are quite soft, with lots of suspension travel - always try to keep 4 wheels on the ground). On smooth tracks, a lot of that doesn't matter.

[wht510]

Rightyo...

You've lowered your car and this is the reason why you are investigating this?

By placing the RCA's on the front, you will be raising the roll centre back up to where it was close to when factory.

By physically raising the rear end, you will not be changing any geometry (which will be good for camber/toe curves staying close to factory) and effectively raising the roll centre back close to factory.

If the roll centre(s) are set too low, there is usually more body roll and you have to set stiffer springs or bars which can be a compromise. If you are going to uprate your suspension and run harder springs, the slightly lower roll centres wont matter as much.

Lower roll centres and stiffer bars usually increases the corner weight (more weight transfer) and therefore makes you a little faster in the dry but slides easier in the wet.

Roll centres too high usually causes jacking and minimal body roll and can make the cars suspension hard to tune.

Just remember load will transfer quicker where the roll centre is higher. This can help tune understeer/oversteer depending on what you want and where your COG is.