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

[Roy]

You can change the bias by putting a higher coeffecient friction pad in the rear

[MBS206]

Rowdy.

Generally, I've been advised, to get good braking across front and rear, to run a higher temp set of pads in the front, then in the rear.

And also, if you really want to, run solid rotors in the rear, and run slotted and ventilated rotors in the front.

Generally brings the rear pads efficiency up a little bit more compared to the fronts.

But, the true way to adjust brake balance, is by adjusting either caliper sizes, or getting a brake bias adjuster.

[Roy]

Bias adjuster is poo. The true way is get a decent pedal box...but bias adjusters do a similar thing...just not optimally

[Duncan]

The brake balance front to rear won't change how much the front of the car dives, that is caused by the total braking force not the front/rear split, and the front alignment and suspension.

All you need for brake balance is both front and rear tyres getting to lock up at exactly the same time. its that easy lol

If you want an effect where the tail is looser under brakes you should start with toe out in the rear. Softer front springs, rear brake bias and 2 way diffs are all just ways to bastardise your rear end handling to make it lock up....just does not make sense for that purpose.

Certainly in some cars like light fwd you might want the tail to swing mid corner but not in a big rwd, you are better of keeping it tidy, late brake and apex and then on the gas hard.

Yes the semis are worth 3-5 seconds depending on the track, and also they will last much better than road tyres on the track too - with roadies you always want to push them to hard so you end up chewing them to peices, especially on the outside edges.

If you want cheap semis look outside the bridgestone and dunlops, maybe try falkens, toyos etc, they are about half the price. Also stick to smaller rims 16 or 17 they get much more expensive in larger sizes

[djr81]

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?

You need to differentiate the cars handling characteristics during the three (four if you want to be pedantic) sections of a corner.

1. Braking prior to the corner.

2. Turn in.

3. Mid corner.

4. Power down/corner exit.

If you trail brake during turn in you will reduce your understeer markedly. This is not a function of brake distribution (front/rear) as the pedal effort used is quite small. In an understeering biased car (read GT-R) it may have the effect of reducing your speed during part 3 (ie mid corner) of the turn. Done properly it will reduce the time spent at low TPS & hence allow the important bit, ie power down to happen earlier. You can then carry more speed down the following straight which is important as it has more of an effect on your lap time than apex speed.

You use trail braking to transfer weight onto the front tyres & hence allow them to develop more grip. You shouldn't be trying to unsettle the rear as this will simply lose you time.

In any case mucking about with brakes, toe settings & small adjustments in camber will not solve a fundamental issue with the ride height & rake angle. You need to sort this first as some settings can markedly change the behaviour of the car in the different parts of the corner.

[Snowman]

Rowdy - we are currently looking into getting a lazer temperature gauge for the clubs use. This will also help find out if there are any major set-up issues.

[Rowdyr32]

Snowy I forgot we have one at work. One of the guys dragged it out today when we were in testcell. I'll bring it along to the next track day. It would be really interesting to see the difference between all the cars and the speeds they're doing.

[Sydneykid]

You need to be carefull when using laser pyrometers, they measure the skin temperature (ie; the tread surface). This is affected by stuff like the run down pit lane. For example, if you have lots of negative camber, the skin on the inside of the tyre will stay hot while the skin on the outside will cool down rather rapidly. That's why race teams use probe style pyrometers which enable us to read the temperature just below the skin, which doesn't cool down as quickly.

Regardless of which type of pyrometer you use, make sure that you don't slow down on the in lap if you want representative temperatures. Come it hot, then measure and then go out for a cool down lap.

Cheers