Understeer at Winton Raceway

Sirois · Postby **Sirois** » Wed Feb 13, 2019 1:40 pm

And what should I look for as far as a G plotting device?

It doesn't need to be anything too fancy, rather just something that can tell me whether I have more grip or not after a change

Magpie · Postby **Magpie** » Wed Feb 13, 2019 3:37 pm

Sirois wrote:And what should I look for as far as a G plotting device?

Unless you already have some form of data collection this can wait. Harry's Lap Timer can do a friction circle, is cheap and from anecdotal evidence (from others) accurate.

http://hpwizard.com/gg-diagram.html

http://trackdayzone.com/articles-general/driving-technique/717-the-friction-circle

Sirois · Postby **Sirois** » Wed Feb 13, 2019 5:00 pm

Interesting and rather surprising read.

So a well set up car should be able to have similar G forces under braking as it does through corners?

The available grip I have during braking far exceeds that of cornering, by multiple times (feel only, nothing scientific to back it up).

Even grip from acceleration feels better. I have never tried launching it but even flooring it in 1st gear gives no indication of nearing wheelspin (the car should do a high 13 second quarter mile).

Magpie · Postby **Magpie** » Wed Feb 13, 2019 8:05 pm

I say it is a setup issue. I cannot brake as well as I can corner (yet).

These are my AR-1's after many track sessions, I will tally the laps up soon. They are rotated often to keep the wear even.

What I plan to use on Saturday

Sirois · Postby **Sirois** » Wed Feb 13, 2019 9:05 pm

Mine look nothing like that.

The fronts are actually completely smooth, they don't even look worn but they are when I look at the tread depth.
And those little NANKANG imprint on the outer edge of the tread is still there.
The rears have a bit more of that rough look that you get from tyres after they've been on the track but nothing too severe.

How much droop is a good amount to have?
And as far as bump travel I will aim to get it hitting bumpstops just before the wheel would hit the inner guard (so max possible travel).

Sirois · Postby **Sirois** » Wed Feb 13, 2019 9:10 pm

I've also ordered 2X Nitto NT01s in 225/45/15 for the front.
One of my front tyres was a bit damaged so it was best I change it out anyway.

rascal · Postby **rascal** » Thu Feb 14, 2019 6:57 am

Sirois wrote:I've also ordered 2X Nitto NT01s in 225/45/15 for the front.
One of my front tyres was a bit damaged so it was best I change it out anyway.

I’d be ordering 4x, given they will be different grip level to the rears.

I’ve run with mismatched fronts/rears before (same tyre/size but two were heat cycled out) and car balance is horrible with no amount of adjustments could fix the either chronic understeer or chronic oversteer, depending on where I put the ‘bad’ ones..

Sirois · Postby **Sirois** » Thu Feb 14, 2019 12:48 pm

Yes ideally they would be, but at this stage the rears are in really good condition and I am chasing a front end grip issue.

I'll see how I go in the next track outing (hopefully pretty soon) and if needed I'll change them for the time after.

Sirois · Postby **Sirois** » Thu Feb 14, 2019 9:06 pm

I measured my droop and bump travel

Front droop: 60mm
Front bump: 55-60mm of shock travel to the bumpstop. Being a MacPherson strut this should be pretty close to wheel travel as well. There's no indication of hitting the bumpstops.

Rear droop: 55mm
Rear bump: It was hard to measure due to the motion ratio of the multilink suspension but it must be 80mm+

Are these a good starting point for the track, or should I allow more bump, less droop?