R33 Gtst Handling Advice

[White GTS-T]

A negative figure denotes toe out.

[r33_racer]

Good to know that its the right way then. Heading in the right direction.

[Littlehorn]

With those alignment settings you usually want 2-4mm toe out on the front, are you saying have 2.8mm of toe out or toe in?

That is 2.8 toe out on front, and 2.5 toe in on the rear.

Up to now i haven't really been considering where the weight comes from just any weight loss is good. Just considering whether keeping a more even Front Rear weight balance might have a positive effect on handling. But having a read around, as with anything it seems there are pros and cons.

[toppertee]

With those spring rates I would be dropping the rear sway bar off totally. If it does roll a little then stiffen up the front bar, though I doubt it will.

Run about -1.0 rear camber with about 3-4mm toe in overall.

There is also an inherent flaw in the rear end design of the r33's when the tire travels from a drooped state to loaded state, the toe essentially becomes dynamic rather then staying at what you set it too statically when doing a wheel alignment.

Plus 1,

After having all sorts of oversteer problems, removed the aftermarket sway bar. Much better. Found it a really hard thing to do. Goes against, what I though I should have done.

[Touge Kyousou]

One thing that's been skimmed over - tire pressures ?
Maybe have a look at the wear of your tires and also their condition/age and look at trying out different pressures ? Along with suggestions in the thread as the time gap wouldn't just be tires.

[Touge Kyousou]

You also mentioned there are other cars with similar power to weight etc, but not the cars themselves ? They might just be cars with better balance and chassis from factory...33 isn't the most suited to circuit

P.s. Your car looks so much fun to drive, exhausting, but fun!

Once i got my car sticking a bit better, it was less fun to drive haha

Edited July 6, 2014 by Touge Kyousou

[Littlehorn]

Plus 1,

After having all sorts of oversteer problems, removed the aftermarket sway bar. Much better. Found it a really hard thing to do. Goes against, what I though I should have done.

Interesting might give this a try next time i get a test day down at Hampton Downs.

I must admit the logic of how a sway bar never quite made sense to me. I would think that increasing the weight of the rear sway bar means that the tyre on the inside or the unloaded tyre is being compressed by the sway bar so therefore getting better road contact. Doesnt this mean better rear end grip, Im obviously missing something here.

One thing that's been skimmed over - tire pressures ?

Maybe have a look at the wear of your tires and also their condition/age and look at trying out different pressures ? Along with suggestions in the thread as the time gap wouldn't just be tires.

Tyre wear after alignment changes deffinitely looks more even i will post temps below.

You also mentioned there are other cars with similar power to weight etc, but not the cars themselves ? They might just be cars with better balance and chassis from factory...33 isn't the most suited to circuit

P.s. Your car looks so much fun to drive, exhausting, but fun!

Once i got my car sticking a bit better, it was less fun to drive haha

Other car i was talking about is an S14 Silvia, running about 220kws but not as heavily stripped as mine, so it is probably a little lighter and a little less power.

And yes it is alot of fun and tiring particularly since the power steering stopped working properly when i removed the hicas computer.

So a reasonably successful track day at Pukekohe this weekend. The car deffinitely felt more stuck, the front end was very solid the rear is still a decent bit more lose it just seems to get very light in higher speed corners.

Unfortunately not the best comparison because a different track but i am hoping to leave the settings as is and get down to another Hampton Downs track day for better comparison.

I had a play with the pressures and to me it seemed more sticky as i reduced the pressures, so hear are the results:

Front 34psi hot

Temp from inner on the left side

63, 54, 48

Rear 34psi hot

Temp from inner on the left side

61, 53, 45

So as you can see it looks like less camber would be desirable for this track, I am picking that at Hampton Downs these temps will look more even as the track is less bumpy and has a more grippy surface.

I am just in the process of loading up video will post up this afternoon, but in conclusion it would seem that there has been a reasonable improvement (about 2 seconds part of that is driver confidence) but on this track the camber is to high. Oh and did i mention the car doesnt like bumps which im pretty sure this is down to the lower ride height, it seemed a little more unsettled than last track day through turn 1 which is very bumpy.

Here is a pic of how it looks through turn 1

and a decent pic of the car

Edited July 7, 2014 by Littlehorn

[zebra]

tidy car.

[Plattsy]

that isnt stock height man.

[Littlehorn]

that isnt stock height man.

It was at 350mm, now at 340mm.

That pic was also taken coming out of a left hander so a little bit of compression on the right side.

Another interesting thing to note, is that i alwasy seem to lap faster after about 7 or 8 laps, maybe these tyres are just towards the harder end of the spectrum, anyone used the FZ-201s before do they come in different rubber hardness?

[hrd-hr30]

Interesting might give this a try next time i get a test day down at Hampton Downs.

I must admit the logic of how a sway bar never quite made sense to me. I would think that increasing the weight of the rear sway bar means that the tyre on the inside or the unloaded tyre is being compressed by the sway bar so therefore getting better road contact. Doesnt this mean better rear end grip, Im obviously missing something here.

A sway bar simply wants to return to its original position. In a corner, it will resist the outside wheel being compressed, and on the inside it will also resist the wheel drooping, meaning less weight on the inside wheel. Both of those things increase the tendancy to oversteer, and give you less exit traction.

I ran my 180SX with no rear swaybar. With 6.25kg rear springs, you don't need a rear swaybar IMO.

Rear bump steer WILL be an issue if you have adjusted camber wth a camber arm and have the stock 'traction' arm. Sorting that out is a time consuming process but makes a big difference. The car won't be so twitchy and will be alot more settled.

I'd suggest making those two changes and the car wil be transformed.

I'd also try 2 or 3 psi lower hot pressures. I ran the FZ201 at 31-32psi hot on my 1250kg 180SX. I also run 32psi hot on my1530kg Soarer with Nitto NT01s.

edit - yes FZ201s come in Medium and Soft. I used mediums. They did change their compounds a while ago though. The original ones were faster/softer. That's the only reason I didn't buy them again for the Soarer. The original FZ201s were great bang for buck. The later ones are not much good.

Edited July 7, 2014 by hrd-hr30

[Littlehorn]

Here is the footage, https://www.youtube.com/watch?v=C1uOcw1aLUc a little hard to tell how handling has been affected from this footage. The main corner where you want lateral grip is the last corner coming onto the front straight (with the big green brdge over top) this is where i can often feel the rear starting to drift and that wall is awfully close.

I ran my 180SX with no rear swaybar. With 6.25kg rear springs, you don't need a rear swaybar IMO.

Rear bump steer WILL be an issue if you have adjusted camber wth a camber arm and have the stock 'traction' arm. Sorting that out is a time consuming process but makes a big difference. The car won't be so twitchy and will be alot more settled.

I will deffinitely play with removing the rear bar, and will have a look into the rear traction arms as a next step.

I'd also try 2 or 3 psi lower hot pressures. I ran the FZ201 at 31-32psi hot on my 1250kg 180SX. I also run 32psi hot on my1530kg Soarer with Nitto NT01s.

Yes i actually realised only in the last session that my pressure gauge was out by about 2 psi when compared to a mates good quality one so will deffinitely go down 2-3 psi and try.

edit - yes FZ201s come in Medium and Soft. I used mediums. They did change their compounds a while ago though. The original ones were faster/softer. That's the only reason I didn't buy them again for the Soarer. The original FZ201s were great bang for buck. The later ones are not much good.

So this could be an issue. Tyres should last longer though. will have a look at the sidewall see if there is any markings about the compound.

[Duncan]

On pressures, I'd run them at 32 normally as well (have used both softs and hard FZ201 before with great results)

However, if you are getting faster towards the end of the session that says that they are working better as they get hotter/higher pressure. Or maybe you just get more confident with more laps

[toppertee]

^^^^

So true, big heavy, slide around.

One thing in motor sport, I've learnt, I'm not going to be the quickest.

But...There a very few things in life better than an, RB25 on full boost, going sideways. It's the most fun car I've ever driven!

[r33_racer]

As I was saying earlier on, I found the traction arms is what causes the dynamic toe problem with r33's. I had to modify an adjustable one in order to get enough range so I could tune it out so it stays at what we set it at statically. From memory I had to shorten the links threaded body by about 1/2" overall (1/4" each end) so the toe would stay fixed no matter what arc the rear wheels traveled through. That fix and the removal of the rear sway bar made a remarkable difference in rear end grip.

That is something to look at also. Our rear end grip issue has been abit of struggle as we run alot more horsepower then most, however our 33 also weighs about 1600kg with driver and fuel....

[Littlehorn]

As I was saying earlier on, I found the traction arms is what causes the dynamic toe problem with r33's. I had to modify an adjustable one in order to get enough range so I could tune it out so it stays at what we set it at statically. From memory I had to shorten the links threaded body by about 1/2" overall (1/4" each end) so the toe would stay fixed no matter what arc the rear wheels traveled through. That fix and the removal of the rear sway bar made a remarkable difference in rear end grip.

Ok so here is a pic of my rear suspension.

Lower arm is standard but the 2 upper arms are adjustable.

So as the rear suspension compresses does the wheel toe in or out more?

However, if you are getting faster towards the end of the session that says that they are working better as they get hotter/higher pressure. Or maybe you just get more confident with more laps

There is probably an element of this! The car has only recently been sorted after a few issues with gearbox etc. so i havent had a lot of consistent seat time recently.

[r33_racer]

We found on our car that it would toe out under droop, and toe in under compression. We were setting toe in at about 4mm overall and as we lifted the car and the wheel would droop the toe was going to +13mm toe out from the static -4mm toe in. Its a huge change, obviously the car wont change that much on the track as both wheels dont extend into full droop while racing, but ideally you dont want any change at all. So the short arm at the front had to be modified inorder to get enough adjustment so we could get the settings to stay where we wanted. However your ikeya formula arms may have more adjustment then ours. We have some cheap items on our car. You will find out if you can cure it or not when you start adjusting it all.

We never really noticed it or checked to see what was happening in this regard until Glen Seton pointed it out to us, apparently its a common problem with most OEM IRS setups or atleast that is what he has found when setting up alot of road car turn race car suspensions for circuit work.

[hrd-hr30]

what you are talking about is called bump steer

Edited July 8, 2014 by hrd-hr30

[r33_racer]

That sounds like it. To be honest I don't know all the proper terminology, it's good someone does! Makes it easier to explain more accurately what I'm trying to describe.

[Littlehorn]

Cheers guys my terminology understanding is also pretty lacking, but i understand now. However it looks like something that would be fairly difficult to eliminate short of building custom pickups and having both arms the same length and mounted parallel.