Struggling to put the power down

[R34NeoLover]

Hey all, so i have an r34 gt-t making 300+rwkw, and the rear wheels seem to give way when on full throttle, around 4k+ rpm, when boost is on, i just break traction and start sliding to the left.

My setup:

Tyres:

front: bridgestone potenza re003 235/40/18

Rear: bridestone potenza re003 245/40/18

 

Suspension: bc br coilovers.

 

When the car was making 200rwkw, it was booked in for a wheel allignment and suspension setup specifically for the race track winton, so the rear coilovers are pretty stiff.

 

Could it be because my rear suspension is setup pretty stiff? Could it be because 245/40/18 isn't going to cut it? I have purchased 265/35/18 nangkang ar1s semi slicks for sandown in 2 weeks, i am unsure if those tyres will solve my problem, atleast on the race track.

 

Should i purchase larger and better tyres for the rears? Should i take it to a suspension specialist to adjust the suspension for this kind of power? Should i do both?

 

Any help is appreciated thank you.

 

[GTSBoy]

4 minutes ago, R34NeoLover said:

Rear: bridestone potenza re003 245/40/18

Well, there's your problem.....

Very ordinary tyre for that duty.

But....there are many other things you would probably benefit from changign also.

5 minutes ago, R34NeoLover said:

Could it be because my rear suspension is setup pretty stiff?

Yes.

6 minutes ago, R34NeoLover said:

Could it be because 245/40/18 isn't going to cut it?

Yes. Bigger would be better. 245s might be OK with more sticky rubber.

6 minutes ago, R34NeoLover said:

Should i take it to a suspension specialist to adjust the suspension for this kind of power?

Alignment for circuit track will not necessarily be ideal for drag launches.

Spring rates and damper rates for circuit will not necessarily be helpful for drag launches.

Subframe alignment (or lack thereof) can be set to benefit lateral grip or to benefit launch grip. Can't be both. At least the R34 has got less anti-squat than the older (R32) rear ends do. But it can still be improved for launch.

 

[Duncan]

Surely if you wanted 300+ in a rwd car it was because you *didn't* want rear traction?

Unless the rear wheels are tramping when they spin, the shocks and springs won't make any difference to your straight line, in gear traction. Wheel alignment can, if you want to minimise wheelspin in a straight line you could go for as little camber as possible (will depend on your ride height and if you have any aftermarket arms or bushes), and 0 static toe. However, this would increase the likelihood of loosing traction at full throttle in corners - trade off....

What will make a difference is tyre quality and width but even then it is likely any tyres will spin in 1st and probably 2nd with that sort of power. Good semi slicks are noisey and tramline on the road but will give you maximum chance of traction (again, a trade off). You should be able to fit 10" wheel (285/295 tyres) with the right offset.

You should probably just have a low/hi boost switch and leave it in low for normal driving, because everything I've suggested above will make your car harder to live with for 99.9% of day to day driving.

[R34NeoLover]

Wow thanks for the quick responses!

The wheels and suspension were put in place to handle 200rwkw, but after 2 or so years, i just wanted more power, as i do sandown track days every now and then.

 

I think eventually when these potenza re003s wear out, ill upgrade to a better tyre, probably something like a michellin ps4s or there abouts, in the 265/35/18 size, i drive pretty sensible on the streets, so i am not too worried about traction on the streets, i rarely go above 5k rpm anyway.

 

Now i did purchase nangkang ar1 semi slicks for sandown, 245/40/18 fronts, 265/35/18 rears. I am hoping these alone will fix the problem, but after reading your responses, think I'll get it booked in for a wheel allignment and suspension setup for this kind of power.

 

 

 

Edited January 13, 2021 by R34NeoLover

[admS15]

I have around the same power. I have 265/35/18 on all corners. Yokohama Ad08r street and nankang ar1 for track. Track grip is pretty good, a little throttle control is required on 2nd gear corners otherwise flatout is fine.

On the street 265 Ad08r is still not enough with stiff coilovers to grip in 1st,2nd and sometimes 3rd. Your re003 have no chance. The only thing that improved grip immensely in the lower gears was stock rear shocks when i was troubleshooting other issues. This also has adverse effects on handling so is only good for drag racing though.

My next move to find more grip will be 295 wide 18's.

I have a proper diff too btw, helps but still need more.

[R34NeoLover]

4 minutes ago, admS15 said:

I have around the same power. I have 265/35/18 on all corners. Yokohama Ad08r street and nankang ar1 for track. Track grip is pretty good, a little throttle control is required on 2nd gear corners otherwise flatout is fine.

On the street 265 Ad08r is still not enough with stiff coilovers to grip in 1st,2nd and sometimes 3rd. Your re003 have no chance. The only thing that improved grip immensely in the lower gears was stock rear shocks when i was troubleshooting other issues. This also has adverse effects on handling so is only good for drag racing though.

My next move to find more grip will be 295 wide 18's.

I have a proper diff too btw, helps but still need more.

Nice to see someone in a similar boat to me. Good to hear the nangkangs should be fine, i am yet to use them on the track, but if you say they dont break traction or even slightly fish tail down the straights, at this power, then that makes me more confident.

At 200rwkw the rears would fish tail abit coming out of a corner, but that was easy to work around, so i am not expecting it to have 100% grip around the whole track, just mainly hoping it will be fine down the straights.

[admS15]

Will be fine down the straight unless your diff is single pegging.

[GTSBoy]

Yeah - the diff. Something I thought about and forgot to get to mentioning. If the diff is a stock VLSD, forget about it. You need a proper mech 1 or 1.5 way.

[R34NeoLover]

Yeah i am still running stock diff. You think the stock diff will still be an issue at the track?

[GTSBoy]

The stock viscous diff is a piece of crap. No good at 200rwkw, let alone 300.

Although, if your car is an S2 with a helical diff.....then helicals are a good thing. Not ideal for the track, but should be good. But there are only probably about 10 cars in Australia with stock helicals (at least that's what it seems like).

[R34NeoLover]

Nah its a series 1

 

i probably should upgrade it, but i know next to nothing about diffs, is there one that does well at the track and is comfortable enough to use on the streets?

 

also i should mention the wheel allignment setup has negative camber i think, around the 1.5 mark, cant quite remember the specs as the allignment was done 2 years ago.

[Dose Pipe Sutututu]

Nismo GT Pro 1.5way LSD

[Murray_Calavera]

Get the diff and report back. You'll probably find the diff is enough to keep you happy once it's in. 

[R34NeoLover]

1 hour ago, Dose Pipe Sutututu said:

Nismo GT Pro 1.5way LSD

Thanks for the reply. Do you happen to know how this would affect driveability? I don't know much about diffs, i just remember reading something about some of the harsher diffs making the car a pig to drive?

[Dose Pipe Sutututu]

Will chatter and knock on u turns, however if it's too aggressive you can alter the engagement and also add friction modifiers too.

A bit of a compromise, but if you want fast lap times, and being able to put power down then you need a proper diff.

[R34NeoLover]

30 minutes ago, Dose Pipe Sutututu said:

Will chatter and knock on u turns, however if it's too aggressive you can alter the engagement and also add friction modifiers too.

A bit of a compromise, but if you want fast lap times, and being able to put power down then you need a proper diff.

Hmm, now that i think about it, the diff does make clicking noises sometimes during low speed turns, feels slightly rough when revs drop down low while turning, then accelerate, and makes a slight rotating whine when in 5th gear at 80kph. I should probably get it checked out, unless those are normal characteristics of a series 1 r34 diff? All those things may or may not be diff related, i honestly wouldn't have a clue.

 

I am attending a sandown trackday in less then 2 weeks, ill see how i go with the nangkang ar1s, if i still have issues, i guess ill be looking at a possible diff upgrade in future.

Edited January 13, 2021 by R34NeoLover

[GTSBoy]

You need to 100% know what diff is in the car before you change anything. Do not buy a thing until you know what centre you have, what stub axles, etc.

[Kinkstaah]

All of the advice above is valid.

Consider a 1 way diff instead of a 1.5 way if you're shopping Nismo. I had a rare working viscous center and honestly it was nothing but a downgrade to go a mechanical diff.

Note: Rare working VLSD, and I suspected it would stop working plenty fast.

300kw and full throttle in 1st/2nd gear is just not a thing in a Skyline on road tyres. You must learn to threshhold accelerate 😛 You can make it 'better' (bushings, diffs, tyres, turbo choice/how boost gets ramped in) but it'll never be fully eliminated.

The best answer for this is boost by gear which is an option on most modern ECU's if you want to just plant your foot in any gear with no consequences 😛

[Duncan]

Since you wanted more power mostly for track use and the power is a pain on the street, adjustable boost level is a smart answer.

Then, you aim for a wheel alignment that is a mid point between street and track use. This means a little camber (-1 to -0.5) and probably 0 toe at the rear, and at the front as much caster as you can get, a little toe out and medium camber (will depend on how much adjustment your bushes and arms have). You should also upgrade sway bars, and if your shocks are shot you could look at upgrading them to something street/track suitable.

Yes a good diff will help a lot on the track but really not on the street.

[niZmO_Man]

What's the specs of your wheels?