mpruden

I've retired my 993 from track duty, and switched to a BMW E46 330.

At Thunderhill West T7, T9, and T10 are 2nd gear hairpins all in quick succession.

I know I must be "missing something" because I can't get the car to rotate no matter how much brake I hold into the corners.

Are there any tricks to attacking hairpins like these? Is it line problem, a vision problem, a brake release problem, etc?

This link should put you right at the hairpins at 10:10. Ignore any other shenanigans you may see

EDIT - looks like Rennlist doesn't embed YouTube with a bookmark. Hairpins without traffic start at 2:30 and roughly ever 1:30 after that...

dgm8138

Do you by any chance have a speed trace from AIM or anything besides Harry's? I've learned through comparison that Harry's is....a toy really.

My guess w/out a speed trace based on the language you used in the description of the problem ('no matter how much brake I hold in the corners') is that it is a brake release problem. Too much brake in a corner will rob the car of front lateral grip (think of the tire lateral g vs. long g curve).

I can't pick up the pitch motion of your car well enough from your video, but someone else may be able to! So...in that case...ignore what I've said.

moveswiftly

I agree. While trail braking into a corner will help, too much trail brake is counterproductive.

Kevin Fennell

It looks to me like maybe you are too slow at the point where it is time to be turning in, for the trail braking to work there, you need to be going fast enough for it to cause some weight transfer.

Another way to put this is you are braking at the normal spot you would as if you were going to release the brake and then turn in, but you are holding the brake through turn in which is just slowing you down and maybe causing understeer?

Veloce Raptor

Tough to tell, but IMO over slowing prior to turn in. Remember, the instant you begin turning the wheel, your speed drops even more due to tire scrub. So don't over slow with the middle pedal prior to turn in

mpruden

re:Harry's - Yeah, a real data system is on the list, just been prioritizing tires and brakes

I am using a nice external GPS unit in the interim. A speed trace should be very accurate. Let me try to get one out of this app and post it.

That being said, I think you guys are on to something - I'm too slow going in to the corners. Rotation under braking used to be (too) easy in the 993. In this car, I really struggle with it.

Could it be that I'm just so far under the grip limit of the rear tires at turn in, that I can't get the rear to lighten up enough to rotate?

fleadh

Can't say anything about the technique without looking at data traces, but from the video your car has tons of understeer -- everywhere.

-mike

mpruden

Here's the speed trace from those 3 hairpin corners.

jdistefa

Car understeers. In addition to hairpin(s), look at T4 where you are consistently adding input after apex due to poor turn-in/rotation.

I would assess and adjust your setup first. Do you have baseline alignment numbers? Tire? Adjustable shocks/sways?

Get that stuff right and then work technique and - agree with Dave - corner entry speed. Until then any discussion of technique must assume a degree of compensation for less than perfect car setup.

mpruden

I hear you. It certainly feels like it understeers. This is my first front engine track car, so it's tough to know how the car should behave.

The car has MCS single adjustable non-remote reservoir shocks. Adjustments are 9 clicks from softest in the front and 7 from softest in the rear.

Sways are adjustable as well (2 sets of holes in each bar). Both are in their stiffest setting.

Tires are a square setup 255/40/17" Hankook RS4s. 35-36PSI.

I could soften the front sway bar and firm up the rear shocks a few clicks. That should help w/balance, correct?

Veloce Raptor

Soften front shocks too

rlm328

Review this write up it is pretty good.

http://speed.academy/how-to-fix-unde...-setup-tuning/

Keep notes and only change one thing at a time. Note what it does to the over all handling.

jdistefa

Yup.

You need to know your rake and alignment as well.

Decrease understeer / increase rotation with:

- more rake
- zero (or +) front toe
- less rear toe
- increase front camber (up to a point)
- more rear brake bias

333pg333

Cure that understeer and it will give you access to apexes. It will then allow you to time your braking points much more accurately.

mpruden

Seems unanimous - more a car weakness than the nut loose behind the wheel. Not what I was expecting, but I guess it's good news?

Assuming dry weather, I'll soften the front bar at home on the lift, then head to Laguna (for the first time) in a couple weeks.

I'll make shock adjustments a little bit at a time and track the results. Thanks for the feedback all!

Edit - I'll also go for more negative camber at my next alignment. I'm at roughly 2 degrees, where the guys that race these are at more like 4.