My Diff Is Single Spinning?

[carltonmaurice]

I took my car to the Collie Motorplex and the inside tyre went from as new to down to the wear markers in 30 laps.

It is lighting up in 3rd and leaving black marks on the corners. Car is R33 series 1 RB25det, with coil overs.

I thought all turbos were limited slip?

What can I do to get power to the ground?

A mechanical diff was quoted at $1800

Advice would be appreciated.

[djr81]

Well trying some throttle control could be a start.

Diffs wear out. The viscous type (Which you may well have) aren't great for track work. But yeah a mechanical will sort your issue or atleast get both wheels spinning. Just don't get too aggressive an LSD they are just plain annoying and don't do anything for the handling.

The other thing to note is the corner exits at Collie are bumpy due to the track degrading over the years. Depending on how hard your spring rates are you may well struggle for traction irrespective of your LSD type. So what coilovers do you have?

[carltonmaurice]

Car is actually a 180 with R33 transplant including full rear cradle. Was told the coilies are Godspeed, and yes they are a bit hard. Would spin in 3rd at the usual corner with the dip, one after that, and even after the chicane, before the sharp one at the start of the front straight. Has 308hp atw, best lap was 56.41. I will back the rear springs off 10mm before I go out again for CAMs training day this Sunday. Should I bother changing the diff? Can get one for $250

[Kinks]

If you are just flogging the inner edges of the rears you are running too much camber

If one wheel is spinning up a lot then you are applying too much throttle too early in the corner, or your rear swaybar is too stiff. The swaybar reacts to the outer corner compressing by trying to raise the inner corner. The stronger this effect is the less weight is applied to the inside tyre and the more it will want to spin. Soften the swaybar.

[carltonmaurice]

Had a wheel alignment the day before, camber is correct. Was wearing evenly across the whole tyre.

The sway bar is stock R33 that came with the R33 cradle.

Tyres are Potenzia RE55S, and I had 30psi cold in them.

This Sunday I will back off the rear springs 10mm and run 26psi cold.

Is this the right thing to do?

Second gear is only good for short shifting as it just lights up.

Boost comes on at 3000rpm, Hiflow R34 turbo.

Cheers for the advice, keep it coming.

[djr81]

If you are just flogging the inner edges of the rears you are running too much camber

If one wheel is spinning up a lot then you are applying too much throttle too early in the corner, or your rear swaybar is too stiff. The swaybar reacts to the outer corner compressing by trying to raise the inner corner. The stronger this effect is the less weight is applied to the inside tyre and the more it will want to spin. Soften the swaybar.

Problem with softening the rear bar is it will induce more understeer which an S chassis with an RB will have in abundance.

[djr81]

Had a wheel alignment the day before, camber is correct. Was wearing evenly across the whole tyre.

The sway bar is stock R33 that came with the R33 cradle.

Tyres are Potenzia RE55S, and I had 30psi cold in them.

This Sunday I will back off the rear springs 10mm and run 26psi cold.

Is this the right thing to do?

Second gear is only good for short shifting as it just lights up.

Boost comes on at 3000rpm, Hiflow R34 turbo.

Cheers for the advice, keep it coming.

You should be aiming for a hot running pressure not a cold set. RE55's from memory like a number in the low 30's hot.

If you have hard springs and soft anti roll bars you need to get some new sway bars and check what your springs are.

When you say back off the rear springs by 10mm do you mean ride height or preload?

[carltonmaurice]

Preload. Springs had 235kg on them, I think.

[djr81]

Preload. Springs had 235kg on them, I think.

Err don't think that number is correct.

In metric units its kg/mm which is usually a number between 3 and 10 at the top end (Which is still hard) or 20 for an insanely stiff spring.

For imperial it is pounds per inch which is metric x 55, so a 5kg/mm spring is 275lb.

Edited August 24, 2015 by djr81

[carltonmaurice]

Yer, I am probably wrong, will check tonight.

Sorry if this is turning in to an S chassis conversation, wanted to know about the R33 diff.

Anyone tell me what pressure to run in the R55s tyres hot for the track?

[djr81]

Yer, I am probably wrong, will check tonight.

Sorry if this is turning in to an S chassis conversation, wanted to know about the R33 diff.

Anyone tell me what pressure to run in the R55s tyres hot for the track?

A hot pressure between 30 and 35 pounds is where you would want to be.

Question: Can you fit a GTR mechanical centre to the replace the viscous stuff in the GTST diff or do you have to replace the whole diff? The point being a GTR centre may be a cheaper way of fixing it than buying a Nismo part. You can buy new shims from Nissan to tighten the GTR diff up.

[KiwiRS4T]

A hot pressure between 30 and 35 pounds is where you would want to be.

Question: Can you fit a GTR mechanical centre to the replace the viscous stuff in the GTST diff or do you have to replace the whole diff? The point being a GTR centre may be a cheaper way of fixing it than buying a Nismo part. You can buy new shims from Nissan to tighten the GTR diff up.

GTR has 6 x 1 bolts on the half shafts (GTST has 5 x 1) so you would need to use the half shafts as well - although i think they will bolt up to your existing hubs, If you can get the whole rear end c/w brakes that would be easier of course but maybe not cheaper than getting a Nismo diff.

Have you confirmed that you do not have an LSD (jack up the car and turn one side by hand - the other should turn the same way for an LSD) or that it is not functioning properly (put your left hand side of the car in the loose and do a launch or perhaps something more scientific!)?