Stability Under Brakes And Car Walking Around

[Roy]

Fark you fan boy!

Im going to drop the car off for a check of the suspension and comment on how the car walks around at high speed and needs steering input to keep the thing striaght...and get him to increase toe in to about 2mm either side.

[djr81]

The other fun thing some aligners do is confuse per side with total. So I asked for 2mm rear & got 2mm per side.

So I just write down 1mm toe in per side rear etc.

Do the same for the front too as most shops don't understand toe out or why anyone would want it.

To be honest I found that 2mm per side rear toe just made the thing bump steer at the back. But maybe that's just me.

[MBS206]

Roy:

2mm is a fair amount of toe in practice.

My wheel aligner (Who does race cars) was telling me that a change in 0.5MM is a HUGE change in characteristics.

Get your toe set to 0, or a max of 0.5MM toe in and go from there.

[Roy]

Roy:

2mm is a fair amount of toe in practice.

My wheel aligner (Who does race cars) was telling me that a change in 0.5MM is a HUGE change in characteristics.

Get your toe set to 0, or a max of 0.5MM toe in and go from there.

Hmmm. so many different opinions.

I have SK sayign a bit of toe in at the rear and the guys that do my wheel alignments...guys who have won basically every tarmac rally in the country, prepare a lot of serious track and tarmac rally cars and do lots of wheel alignment work on Skylines.

So i hear you , but im reluctant to go against what they are telling me. What else is doen to your car suspension wise...and do you track it?

[MBS206]

Put it this way.

4MM in my opinion and experience will have the car doing what it's doing now but worse.

Just straighten it up and go from there...

Either that, or slide under the car (Leave it on the ground) and measure what the settings are from there!

When the tyres become unwaited, your toe tends to head more towards toe out btw, so if you're running 2mm toe out at the moment, under hard braking and weight shift, with the rear lifting say 2 inches, you'll be headed for around 1-2 mm more toe out the set standard.

And 4mm toe out will be VERY hard to control!

Plus, c onsidering you don't know what your current starting point is, other then 2mm rear toe, you can't really say, give it 2 mm more rear toe, as that could end up at 0 toe over all, or 4mm toe in!

See your issue?

Edit: I can understand, and if I was in your boat, I'd probably go with your guys points of view.

A touch of toe is a helper, but 2mm personally would be my max.

As for track, haven't hit a circuit yet, only skid pan.

I'm going from info my wheel aligner is giving me (He sets up an array of cars, all the way through to James Harrigans race cars... ) and from experience I've had with changing the setup whilst on the street etc.

Personally, maybe you're best setting it to 1mm toe in, and make SURE it's 1mm toe in.

Personally, I'd be sending it back to standard settings and adjusting one thing at a time.

Edited April 4, 2007 by MBS206

[Roy]

Well just had a chat with the wheel alignment guys and they confirmed that +2mm toe is toe in. Looking back through my last bunch of alignments i have always ran 2mm total toe in at the rear so it doesnt look to be the toe settings in the rear

[phunky_monkey]

Hey Troy, have you thought about the effects that the new diff may be having on your car under brakes? The problem never occurred before the fitment of the mech. diff...

[Roy]

Yeh thought about it. But would a diff really do that to the handling under brakes?

[phunky_monkey]

Cheers for the compliments Dane!!! I hope you enjoyed the drive... I wouldn't trust too many 180sx owners driving my car!!!!

Sydneykid, how would you compare your Bilstein kit to Tein RA/RS's??

Surprised you let a 180sx owner drive your car, let alone a commo driver! haha

[Rowdyr32]

Bris after driving behind your car it seemed way to stiff. It doesn't squat at all out of corners really or even body roll that much. I have never been in your car before around corners but going on my old gtst I alway though I needed some a/m swaybars and softer rear spring to get some of the power down. Also you may have a blown rear shock because when I smashed the gtr I had no rear end grip at all and anything I did just unsettled the rear of the car (it felt like a water bed- all over the place all the time). After driving my car at Sandown again after repair it still felt terrible. Now with the new shocks it's really balanced and hard to believe its the same car.

Could you raise the rear of the car to gain more rear end taction out of corners or back off rear swaybar insead of tightening front? Into corners I don't know enough yet.

Did it feel different though turn 1 vs turn 12?

Just messing around with the car a little made me understand how raising the rear or stiffening/loosening swaybars can effect grip and traction. Just moving the rear swaybar from hardest to middle changed the car from an understeering pig to almost right

SAU Vic needs to have a suspension tuning day!

[Roy]

Agree, my brother is coming down from Sydney and i plan on taking him to Winton so he can have a drive. I want to tweak the swaybars a little and try a few different things. You just dont get the chance to at sprints.

So the plan for Anzac day at Sandown is soften rear swaybar and try another 1mm total rear toe in.

[Rowdyr32]

I find the same at track days. By the time I get the car ready the week before you don't really want to crawly around under it and stay dirty for the whole day. If you do want to try something like increasing ride height or back off or on swaybars let me know. If you do I will orgainse something to lay on and car ramps. That kind of stuff really interests me but I'm the same as you and don't get enough time in the car to have it going as quick as it does in its corrent state and understand how to drive it at its optimum into and through corners at the track and then to try something else and see how it goes. Just look at our track times at PI. Each session was faster and faster. I also think the saybar option is the easiest way to go and costs nothing as a bonus for the benifits that can be gained. DO you have circlip or threaded height adjustment. Let me know when your going to Winton. I'll come along to to platy with my susp. There must be a few seconds in my car susp setup atm also.

Sydneykid what ride height did you use on your track gtst and what were the spring rates?

[T04GTR]

what sort of rake angle are you running. i found my 32 used to feel dodgy with the front to low.

[Roy]

Dont understand what you mean by rake angle. Isnt that a bik term? A friend is always talking about it with regards to the trail bikes he builds / restores?

Rowdy, it will be Friday the 29th June that i head to Winton. But i will call you as i may have something better sorted as a friend will be doing a shakedown of his race car in a few weeks and it will be good if tag along with him to Calder on a Wed. he has all the gear and very experienced with building and racing cars....plus he will have everything we need to play

[Cubes]

I remember reading Gary mentioned lowering the car lower than ~350mm? threw out suspension angles?

Something along those lines.

[BRUNSKIGTST]

whats toe in and toe out mean by anychance i new and learning, my car is in pannel shop fitting gtr rear quarter pannels on gtst ^^ so im here learning about new stuff

[Cubes]

Poor GTR's.

[salad]

350/340 for GTS-t/GT-t

355/345 for GTR for drive shaft angles

[djr81]

Dont understand what you mean by rake angle. Isnt that a bik term? A friend is always talking about it with regards to the trail bikes he builds / restores?

Rowdy, it will be Friday the 29th June that i head to Winton. But i will call you as i may have something better sorted as a friend will be doing a shakedown of his race car in a few weeks and it will be good if tag along with him to Calder on a Wed. he has all the gear and very experienced with building and racing cars....plus he will have everything we need to play

Roy rake angle can be best understood by referring to the difference in front & rear roll couple & particularly the jacking effect of the rear suspension. But more easilly by referring to the front ride height relative to the rear ride height, ie nose down versus nose up etc.

Having adjusted mine a few times I can make the following observations:

A nose down car will turn in very well but then tend to wash out through the corner.

A nose up car will not turn in well enough.

A car with the proper rake angle will have a good match between the balance on turn in and the balance at the apex of the corner. So you don't for example, turn the thing in only to find yourself understeering & missing the apex of the corner by a foot because the front end has lost interest.

Hope that makes sense.

[Sydneykid]

On the F3 a 0.5mm toe change is a lot. Our driver can report accurately on small toe changes repeatedly.

But, on a Skyline it gets lost in the slop, tyres, bushes, mount flex, chassis twist etc.

There is no way I can feel 0.5 mm toe change on any of our race Skylines (they have 6 to 12 point roll cages and lots of seam welding) and over the years I have developed a good feel for small changes. On a high mileage road car with no cage, you would be lucky to feel 1 mm toe change.

Toe in a “stabilising” setting. On a rear wheel drive Skyline with reasonable power, toe in is a perquisite. It helps overcome the power oversteer. Plus, under brakes, R32/33/34’s toe out. So the toe in is there to offset that.

Note I am talking about 2wd Skylines here, GTR’s (and other 4wd Skylines/Stageas) sometimes need toe out to overcome their poor turn in. The inability to get enough caster on them being a contributor to that.

I use different spring rates for different tracks and different tyres. For example road tyres don’t like spring rates over 300 lbs/inch, “R” type tyres tolerate up to 400 lbs/inch and slicks are OK over 450 lbs/inch. Note that is the effective spring rate at the tyre, which in all cars is not always the rate of the spring itself (leverage and movement ratios apply). As for tracks, Philip Island, being high speed and relatively smooth, needs (and can tolerate) a higher spring rate than, say, Oran Park.

I also use large amounts of anti roll, anti dive and anti squat so I can run supple spring rates for better tyre contact. I also have double adjustable shocks so I can use bump valving as well.

cheers