How to correct roll center on a R34 GTT?

[Dose Pipe Sutututu]

Looks like you've got most of the bases covered, one mod I've done to date (dare say it's the best handling mod I've done) was to shift the subframe up closer to the chassis.

This allows the arms in the rear end to sit more like how Nissan intended.

My LCA now actually slightly point downwards, where as before they were parallel to the road surface.

Overall gains so far, much more traction, no need to run 4mm total toe in anymore.

[Murray_Calavera]

Did you use these?

https://au.gktech.com/solid-subframe-bushes

[Dose Pipe Sutututu]

24 minutes ago, Murray_Calavera said:

Did you use these?

https://au.gktech.com/solid-subframe-bushes

These ones, they're a little more forgiving than alloy.

https://au.gktech.com/polyurethane-rear-subframe-bushes

[Duncan]

I'm not sure if you mentioned, but a good mechanical limited slip diff will make a big difference in a 2wd r chassis.

Also, it would be worth posting up you ride height (centre of wheel to guard) front and rear and also your alignment, plus any specific issue you have noticed (turn in understeer, mid corner understeer, corner exit oversteer, instability in a straight line etc etc)

[Murray_Calavera]

1 hour ago, Duncan said:

I'm not sure if you mentioned, but a good mechanical limited slip diff will make a big difference in a 2wd r chassis.

Also, it would be worth posting up you ride height (centre of wheel to guard) front and rear and also your alignment, plus any specific issue you have noticed (turn in understeer, mid corner understeer, corner exit oversteer, instability in a straight line etc etc)

100% agree with this. A proper diff would be at the top of my list of priority mods. 

[r34.bryan]

16 hours ago, Dose Pipe Sutututu said:

Looks like you've got most of the bases covered, one mod I've done to date (dare say it's the best handling mod I've done) was to shift the subframe up closer to the chassis.

This allows the arms in the rear end to sit more like how Nissan intended.

My LCA now actually slightly point downwards, where as before they were parallel to the road surface.

Overall gains so far, much more traction, no need to run 4mm total toe in anymore.

Wow didn't know this was a thing... perhaps this could be my solution! Since I wanted to renew all bushings anyways. I will take a better look at this mod. Thanks a lot @Dose Pipe Sutututu !

 

7 hours ago, Duncan said:

a good mechanical limited slip diff will make a big difference in a 2wd r chassis.

Good that you mention it, I'm currently saving up for one. After doing my research I think I will get the Nismo GT LSD Pro 1.5 way.

 

7 hours ago, Duncan said:

Also, it would be worth posting up you ride height (centre of wheel to guard) front and rear and also your alignment, plus any specific issue you have noticed (turn in understeer, mid corner understeer, corner exit oversteer, instability in a straight line etc etc)

Since I can't access my car right now I will measure it once I get the opportunity + alignment settings. Corner exit is not really stable, my guess is maybe the LSD will fix that.

[Kinkstaah]

18 hours ago, Dose Pipe Sutututu said:

These ones, they're a little more forgiving than alloy.

https://au.gktech.com/polyurethane-rear-subframe-bushes

Dumb question

Are these just pineapples by a different name (intended function).
Sell them to me. Axle tramp and my R34 are an iconic combo.

[Dose Pipe Sutututu]

56 minutes ago, Kinkstaah said:

Dumb question

Are these just pineapples by a different name (intended function).
Sell them to me. Axle tramp and my R34 are an iconic combo.

Not at all, pineapples are garbage as you move the subframe even further away from the chassis.

These are replacement subframe bushes

 

[Dose Pipe Sutututu]

4 hours ago, r34.bryan said:

I think I will get the Nismo GT LSD Pro 1.5 way.

Good choice, don't be like me and get a KAAZ 2 way lol..

It's so aggressive, I had to get diff place to reduce the initial clamp.

My friends with Nismo diffs in their Silvias behave so much better.

[Kinkstaah]

1 hour ago, Dose Pipe Sutututu said:

Not at all, pineapples are garbage as you move the subframe even further away from the chassis.

These are replacement subframe bushes

 

Depends on how you set them up!

(though most people do it for max squat, which is as you have described).

Something to consider next time the subframe is out, which realistically is hopefully fkin never...

[Duncan]

Yeah pineapples are a simpler and more adjustable solution than changing the subframe bushes which is a big, subframe out job.

Pineapples let you change the angle of the subframe to improve (or worsen if you are a hectic drifter) the rear traction.

Replacement subframe bushes might or might not have the same geometry as standard, or might also change the angle as pineapples can, it is worth checking before installing.

Raising the subframe is a good way to lower the car without wrecking the roll centre geometry (back to OP's question) but space there is very tight depending on the chassis and setup (eg ATTESSA pump on top)

[Dose Pipe Sutututu]

16 minutes ago, Kinkstaah said:

Depends on how you set them up!

(though most people do it for max squat, which is as you have described).

Something to consider next time the subframe is out, which realistically is hopefully fkin never...

DOOOOOOO IT..

I took mine out (again) and this time welded up the cnut with the GKtech brace kit and powder coated it.

I regret spending money on it, however the car does handle and hook up much better. In other news, out for more testing at Eastern Creek GP Circuit, aiming 1m50s this time round (will be 2nd time out on that circuit).

[r34.bryan]

On 1/22/2023 at 2:29 AM, Dose Pipe Sutututu said:

This allows the arms in the rear end to sit more like how Nissan intended.

Is there also a kit that does the same but on the front subframe? Or did you only do the rear end?

Also, taking out the subframe(s) sounds like a good opportunity to get some Spoon rigid collars, I do need to do some more research on them tho.

[Dose Pipe Sutututu]

2 minutes ago, r34.bryan said:

Is there also a kit that does the same but on the front subframe? Or did you only do the rear end?

I only did the rear as that was the area that gave me the most grief on the track, probably doesn't help I have a fair whack of power only out of two wheels.

Front end wise, I don't really have an issue with poor turn in, once again my car isn't that low so the control arms are ever so slightly pointed downward thus the tie rods aren't in a funny position to cause bump steer.

I do run 7° of castor, I wanted to run a bit more but already the tyres are a bit too close to the guards on lock (running 265/35/18 all round).

[r34.bryan]

On 1/23/2023 at 11:46 AM, r34.bryan said:

Is there also a kit that does the same but on the front subframe?

Is the front subframe even mounted with bushings? can anyone confirm it?

I can't even find normal bushings to replace the oem ones. (if there are any)

[GTSBoy]

3 hours ago, r34.bryan said:

Is the front subframe even mounted with bushings? can anyone confirm it?

I can't even find normal bushings to replace the oem ones. (if there are any)

No. So changing the height of the front subframe is a nonsense. And anyway, the only way that it is ever changed in practice is to space the front subframe down, to allow more room under the bonnet for taller engines (ie, RB30 blocks in R32s). This is the opposite of what's being talked about here.

[r34.bryan]

21 minutes ago, GTSBoy said:

No. So changing the height of the front subframe is a nonsense.

Clear, thanks.

[Duncan]

Yes, this is why at the front extended ball joints are the best option available for addressing bump steer, but again you just wreck the handling if you go too low anyway