R32 Gtr: I Need To Improve My Turn In/ Corner Speed

[Rowdyr32]

I missed out getting an alignment before heading up to NSW due to work.

I just did the trak day at wakefield and had massive understeer problems as the car just wouldn't turn in at all. I lowered the car at Wakefield 5mm on front strut and 10mm on rear strut and the car seemed a lot more settled at the end of the straight. Also backing the front swaybar off one notch from hardest helped.

I had an alignment after and found out that the car was all over the place. For example rear toe +5.8 and -1.7mm. This was the third time driving the gtr and first time with non blown stock lowered shocks. I know I have heaps to learn about driving at the tracks but I have a quick question after reading through a old Beer Barron thread.

The end result is got were after alignment:

front camber: 3.5 deg neg. Good for EC and PI but would be to much for most tracks I guess.

front caster: 5 degrees

front toe: -0.5mm each side

rear camber: 2 deg neg. This was to much for even EC. Will set it to -1.5deg and try that.

rear toe: +1mm each side

front sway bar: one off hardest (mine is the 3 hole type)22mm

rear sway bar: medium (also 3 hole type)

The car handled a lot better at EC and I could hold a lot more corner speed but the car just understeered a little to much and had bad turn in. I know my tyres are at least 2.5 year old falken rt215's and lack grip. The best hand timed lap I got was a flat 1.52 and I know there would easily be a flat 1.48-1.49 in there if the car could carry a little more corner speed with the current tyres/brakes. Still have to measure ride hieght after I empty the car out.

Question is will increasing the toe out front and rear to 2mm each side help turn in and corner grip.

[salad]

increase your castor, try 7deg if you can

make your rear bar harder.

and what ride height are you running?

[Duncan]

Well I think you need to start with some proper track tyres and then see how you go f mthere

Road tyres are endlessly frustrating at track speeds.

Maybe also try turning into corners a little later and see if that helps

[Rowdyr32]

I tried going into corners later but I was also going slower. I'm after overall increased corner speed. I agree with the street tyres but they have to do until they run out of tread.

I don't want to run more caster and risk uni lives and as for running the rear bar stiffer I think it would just make the car slide in the rear more on accel out of corners and not really improve turn in. It felt good when on full power out of corners but I had to brake really late into the corner to make the rear unsettle and them gas it really hard. I want a more balanced package. If it didn't understeer into the corner it should be setup right for the way out.

[Roy]

Seriously...scratched record...what you describe is how most GTRs i have driven handle. Scotsmans is the only car i have drive (albeit) briefly that handled really nicely. Maybe see what he has done to his or get Racepace/Techsport to have a look at it. (And that shouldnt sound like i have driven lots of GTRs, i havent)

What shocks have you got these days...and 1:52 on hack rubber is pretty good

[Rowdyr32]

The car has some circuit valved shocks from sydneykid. It could possibly do with some softer springs for the street tyres but I don't really know. Chris told me that after racepace put a lot extra caster into snowys car it made it handle like his. But I think they actually move the castor mount position on the chassis and modify cusco upper mounts. This is what I understood from my conversation. When I asked Chris all he knew was that if you give RP $800 to adjust the suspension they'll make a r33 gtr handle awesome.

The car is the best handling car I have owned to date now but I know there are a few little things I could do to make it go quicker around corners. I know if I braked harder and linked all of the corners together right in one lap it could have done a 1.50ish time but I'm still learning how to drive gtrs. I have all the power I need for a reliable engine. I bought some spacers from UAS to run 324mm rotors and some ds3000 pads so the suspension is the only thing I need to correct to make the car do the times I want out of it.

I just wanted to know if anybody has run with toe in and then gone to go out and what was the result in how the car handled.

[salad]

From SK himself

Run it at 355 mm centre of wheel to guard at the front and 345 mm at the rear. Use a 24 mm solid front adjustable stabiliser bar on the softest setting. A 24 mm solid rear adjustable stabiliser bar on the middle setting. The rear spring rate needed is ~250 lbs per inch (4.5 kg/mm), the front is ~400 lbs per inch (7.2 kg/mm). Set the rear subframe alignment bushes to the "all round setting". Try for 6.5 degree of positive caster on the front, with 3.5 degrees of negative camber and 2 mm of toe out each side. On the rear, 1.5 degrees of negative camber with zero toe out.

Then adjust the camber for even tyre temps. If it needs more than 4 degrees negative camber on the front, then you don’t have enough bump valving in the shocks.

Once you achieve even tyre temps, then you can adjust the stabiliser bare to achieve the handling balance you like. If it still understeers on corner entry, try another 2 mm of toe out on the rear. If you get mid corner understeer and the front tyre temps are even, then increase the rear ride height, 5 mm is usually enough. If it power oversteers and the rear tyres temps are even, then back off the rear bar I hole. If it still power oversteers then change the rear subframe setting to “max traction”.

[Sydneykid]

Sorry I didn't make it down to Wakefield, I had a stinking head cold on Monday and missed a day, so work was piled up like crazy for Wednesday.

Add to the above kindly posted by salad.

Try the front bar on full soft and the rear bar on full hard. That should cure the mid corner understeer. If it still has corner entry understeer, try 3 mm of toe out on the front and 2 mm of toe out on the rear. You maye find that amount of rear toe out a bit unsettling under brakes, some drivers don't like the nervousness it causes.

If it still understeers, then you have a tyre problem that no amount of suspension tuning will fix.

cheers

[Rowdyr32]

Is this 3mm each side or overall for the front toe? All in all the car was good and I didn't really have a chance to adjust much. I will slowly try different adjustments but the only problem I have is most of it will have to wait for track time because there's not good corners in my area.

[MBS206]

SydneyKid, would you not agree that lowering the rear, more then the front will induce understeer.

Every car I've found, that if you drop the rear more then the front, you induce understeer.

Would it be more advisable to raise the rear back to it's original position and leave the front DOWN the 5mm from original...

So hence, the guy has made the setup worse by is lowering abilities.

The ride height front to rear, and overall is as important to the setup as is the toe/camber/caster afterall.

[Duncan]

....then you have a tyre problem that no amount of suspension tuning will fix.

I still strongly beleive this is your main problem - there is no point trying to fix handling on the track until you start with a good platform....you will probably find you don't have an understeer problem at all once you put good track tyres on it

[MBS206]

I still strongly beleive this is your main problem - there is no point trying to fix handling on the track until you start with a good platform....you will probably find you don't have an understeer problem at all once you put good track tyres on it

I'm in total dis-agreeance here.

What you're doing by putting on a stickier tyre, is making the whole lot of the car grip harder.

Whilst it grips harder, you FEEL like you're pushing the car as hard as it can, BUT when it comes unstuck, its going to come unstuck in much the same fashion, as it did with shit tyres, BUT, you'll be doing a great deal of knots/hour more then the shit tyre.

Sort the suspension out on a low grip tyre. It'll tell you EXACTLY what's wrong in the setup. Once the car is handling how you want, wack on some REALLY grippy tyres.

Slam it round the track as quick as possible then. You'll find you'll do a quicker lap time, on the grippy tyres AFTER running on bad tyres tuning the suspension, then what you will by wacking on some uber grippy tyres and doing the same amount of laps.

The uber grippy tyres still have the exact same suspension setup, meaning the cars characteristics, are at a higher level, but the coefficient of friction has been improved dramatically, Hence, a greater force is required to break the grip, hence, a higher speed is required, but you'll still reach it. At a higher speed, and you'll understeer.

Sort the suspension out so it doesn't understeer, then wack the grippy tyres on.

[Roy]

Yeh makes sense, but then you consider what happens when you have more grip. More roll, more dive under brakes on turn in...the whoel dynamic of the car can be changed. Best bet is live with it until you end up getting the rubber you are going to be running then get it sorted for those tyres.

[MBS206]

Yeh makes sense, but then you consider what happens when you have more grip. More roll, more dive under brakes on turn in...the whoel dynamic of the car can be changed. Best bet is live with it until you end up getting the rubber you are going to be running then get it sorted for those tyres.

Usually a small tweak here, a small tweak there, gets the car back exactly how you want it. And then again, driver behaviour changes, so in the end, he may like the car to understeer, I know some people who do like this, whilst others prefer the car to majorly oversteer, particularly on throttle (Just how they corner)

But generally, it's easier to sort out suspension, on something that will let go easily.

Effectively, you'd rather test out how your new intake valve on an indoors fire works when being lit with soft wood, as it lights up easier, but in the end, you'll use hard wood.

The reason, it gets to your testing point quicker, and easier, kinda.

But the same "reasoning" can be bought across in my personal opinion.

But remember, everyone drives there car differently, and hence, we all set them up differently.

My biggest theory, is that the ride height is fuxored, secondly, it's AWD, prone to understeer, thirdly, front toe is incorrect.

For grip, you want toe in (Grip mid corner) but you loose responsive ness,

Toe out gives you responsive ness, but reduces mid corner grip.

If my memory serves me right (As I talk in 3mm toe in/out not +3mm), positive toe, is toe out, hence, a very responsive ride, BUT no mid corner grip.

And I'd be running as a tester, 0 rear toe, and upto 1mm maximum toe in. (WRX are renowned for having sideways issues if they run any more then 1mm toe out on the rear)

But where I start my setup at, I hand it to my wheel alignment specialist, he's worked on enough race cars suspension wise, I'm just going off what he has told me.

[Sydneykid]

SydneyKid, would you not agree that lowering the rear, more then the front will induce understeer.

Every car I've found, that if you drop the rear more then the front, you induce understeer.

Would it be more advisable to raise the rear back to it's original position and leave the front DOWN the 5mm from original...

So hence, the guy has made the setup worse by is lowering abilities.

The ride height front to rear, and overall is as important to the setup as is the toe/camber/caster afterall.

I gave him the ride height recommendations, as long as he stuck within them, ride height won't be the cause of his understeer. If he has lowered the rear bleow those recommendatioons then that would be a problem.

Cheers

[Sydneykid]

I'm in total dis-agreeance here.

What you're doing by putting on a stickier tyre, is making the whole lot of the car grip harder.

Whilst it grips harder, you FEEL like you're pushing the car as hard as it can, BUT when it comes unstuck, its going to come unstuck in much the same fashion, as it did with shit tyres, BUT, you'll be doing a great deal of knots/hour more then the shit tyre.

Sort the suspension out on a low grip tyre. It'll tell you EXACTLY what's wrong in the setup. Once the car is handling how you want, wack on some REALLY grippy tyres.

Slam it round the track as quick as possible then. You'll find you'll do a quicker lap time, on the grippy tyres AFTER running on bad tyres tuning the suspension, then what you will by wacking on some uber grippy tyres and doing the same amount of laps.

The uber grippy tyres still have the exact same suspension setup, meaning the cars characteristics, are at a higher level, but the coefficient of friction has been improved dramatically, Hence, a greater force is required to break the grip, hence, a higher speed is required, but you'll still reach it. At a higher speed, and you'll understeer.

Sort the suspension out so it doesn't understeer, then wack the grippy tyres on.

The problem with GTR’s is that they are so god damn nose heavy. They work the front tyres hard under brakes. Then they are reluctant to turn in, so you work the front tyres hard up to the slip angle limit. Then they have mid corner push, which further raises the tyre skin temperature. On corner exit they transfer some power to the front wheels further increasing the load on them and exacerbating the tread overheat problem.

So if you are using well worn tyres, there is simply not enough tread on the carcass and they overheat badly after only a couple of laps. A newer tyre (not a brand new tyre), by virtue of its increase ability to handle and dissipate heart, is far more capable of sustaining the desired line.

Then we have the “R” type tyres, which are by design. able to handle higher temperatures. Plus they don’t generate as much heat due to their ability to handle more extreme slip angles.

Tyre tread overheat induced understeer can be cured by very small decreases in temperature. As little as 5 degrees can make a noticeable difference. This then brings the poor overworked front tyre on a GTR back to similar temperatures to the rear tyres. Hence restoring the handling balance, not dramatically altering it.

In summary, it would be simplistic to say that going to “R” tyres would still show up the same handling imbalance. The statement “if it understeers on crap tyres then it will still understeer on good tyres” is hence not always correct. In fact most times it is incorrect when it comes to cars with large weight imbalances front to rear.

cheers

[ferni]

Interesting read, all so complicated.

[djr81]

Interesting read, all so complicated.

Personally I am a big fan of the massive shudder the R spec tyres give when you have gone too far past their optimum slip angle. Off to see the dentist now to get the fillings put back into my teeth. Sweet.

[MBS206]

The problem with GTR’s is that they are so god damn nose heavy. They work the front tyres hard under brakes. Then they are reluctant to turn in, so you work the front tyres hard up to the slip angle limit. Then they have mid corner push, which further raises the tyre skin temperature. On corner exit they transfer some power to the front wheels further increasing the load on them and exacerbating the tread overheat problem.

So if you are using well worn tyres, there is simply not enough tread on the carcass and they overheat badly after only a couple of laps. A newer tyre (not a brand new tyre), by virtue of its increase ability to handle and dissipate heart, is far more capable of sustaining the desired line.

Then we have the “R” type tyres, which are by design. able to handle higher temperatures. Plus they don’t generate as much heat due to their ability to handle more extreme slip angles.

Tyre tread overheat induced understeer can be cured by very small decreases in temperature. As little as 5 degrees can make a noticeable difference. This then brings the poor overworked front tyre on a GTR back to similar temperatures to the rear tyres. Hence restoring the handling balance, not dramatically altering it.

In summary, it would be simplistic to say that going to “R” tyres would still show up the same handling imbalance. The statement “if it understeers on crap tyres then it will still understeer on good tyres” is hence not always correct. In fact most times it is incorrect when it comes to cars with large weight imbalances front to rear.

cheers

Ah, that's fair enough then.

Just a thought I had, would it be an idea, to add in a brake balance, dial in more rear wheel brake force. From what I've seen/read, when running more rear brakes, yes, the back tyres can become very easy to lock, but when you hit the corner, as you're not loading the front end up as much (You're just putting the weight there, you're not asking the tyre to attempt to slow down as much) you have alot more available grip, and when you start to turn in, since the back end is doing most of the braking it is more "twitchy" and alot more ready to comply with a turn in command (But do it too early and be warned of alot of sideways action)

Do you think this would work?

I'm just bouncing ideas now off you SK...

[Rowdyr32]

I believe I don't have enough rear brake bias. After a whole day at the track there was hardly any rear pad dust and I'm only running el cheapo pads. I think it is time for a big bleed first. I put the abs back in and bled it but maybe in needs some more bleeding.

What you are saying makes sense. It could help stop a little of the weight transfer to the front and there for take some weight of the front tyres. Good idea. I have never had a problem with the rears locking.

One of the really quick Vic guys drives his car fast by braking a little later into the apex to unsettle the rear of the car so he can drive out fast without power understeer. And he is fast!

There is no way of putting more rear bias into a gtr though unless you change the master cylinder right? Anyway I won't be doing this. Hopefully some good pads will sort this area out.

Keep your suggestion and opinions coming in. All of your tried knowledge is better than my theory's atm.

What is the general time increase with running semi's over average street tyres? Am I right in guessing 2-3 secinds a lap on a 1.30ish circuit?