coryf

Do you have the specs of current the track alignment? Was the weather similar to November? Same set of tires from before? (with a winter of storage) One hole of rear bar shouldn't change the car from a noticeable under steer to a big over steer. It sounds like there are a few other things contributing to the handling change.

Bob Rouleau

How about the rear wing, is it shimmed to 8 degrees? I found that helped in the fast corners. FWIW, most car setup gurus suggest that we use the minimum roll stiffness to maximize weight transfer and grip. If you prefer oversteer, then YMMV

SH || NC

I know that there are about a 1000+ different variables to this question, and I know I could have changed the bar when I was at the track, but I was lazy and after my off, I wasn't at 100%.

• Front Camber; -2.8° per side
• Front Toe (Out); 1.0mm per side
• Front Caster: stock
• Rear Camber; -2.4° per side
• Rear Toe (In); 1.75mm per side
• Rake; factory
• Lowered 10mm
• Weather in November was much cooler
• Same tires; maybe ~10 more heat cycles on them (~30 total); pressures were about the same

The biggest thing contributing to the handling change was most likely the nut behind the wheel but figured I’d thrown this out there anyway.

I attended an event in March with this exact setup at CMP, and it was a blast; made improvements almost everywhere on track. Although, I was a little squirrelly there as well in a few spots I could trail brake without the rear end slipping and I was getting on the throttle almost pre-apex in some spots without much drama.

Changed the bar, went to VIR.

Yep; have been at 8* since I installed the wing. I am most definitely going back to the softer setting!

Mr Michael B

Thank you.

I have run the car with the soft bar (4 or 5 years ago?), but quickly exceeded its advantage and moved on to the stiffer setting. The laps times continued to drop to the point today that I am at.

When I started club racing in 1990 (yes, 21 years ago) I formed a style that I ran with for years & still use today. That included nice stiff bar settings. Then when racing SCCA with my Pro license that same style gave me the opportunity to secure poles, still standing lap records and wins in a rear engined tube chassis racer - for years. I could never accept under-steer and found that firm rear bar (reducing that) to my liking (and additionally demanding all of the braking to be done in a straight line). I think my forte (then & now) was getting on the power early as the car insisted just for the grip required to keep the rear in place. I would often (and still do) be 100% throttle at turn in - making for an exceptional track out and exit speed (if it stuck ). I find that to still be the case with the 911 chassis - Continuing my favoritism of the stiff rear bar setting.

I remember a guy at Charlotte Motor Speedway SCCA National telling me that I passed him "sideways" through the banked turn at speed. He studied my bar settings after that race in impound thoroughly (I garnered 1st - he 3rd) and at the next outing he adapted. Another guy at the Runoffs at Mid-Ohio took a photo of my adjustments, yet he claimed he was set stiffer (it must have been my rain settings!)

But that's my style. Still when I instruct & train I understand student limitations and we adjust the bar settings to suit. But if I am doing the driving on a track day (or even dabbling in my current Spec Miata) that bar is set stiff. And it yields better lap times - at least for this racer.

997gt3north

I watched the video. I have no idea if what I'm about to say has any merit but here is what it looked like to me - your whole car seems to lack grip. I have driven VIR a few times on different tires (I have a 997gt1.mk1). To me, following you drive, pretending it was me in the car, it almost looks like you had very little grip and that you constantly had to wait, you couldn't push very hard as the car (front and rear - looked more front to me) had low grip - it wouldn't turn in when you wanted - it was gently sliding everywhere.

The car seemed pretty neutral to me. If it was me, I would slap a new set of tires before I made any changes.

I could be totally wrong but it looked like a very slippery track, low grip tires, over inflated tires kind of track session. I looked at all your speeds in corners and it just seemed like you lacked grip given your speed - i.e. you should have been 5-10mph higher - but the car wasn't sticking.


When I first drove my 997gt3.mk1 at VIR with the ****ty OE spec MPSC+ tires (235/305) your video was exactly how I felt - I tried to turn the car in 4/5/6 and it just wouldn't turn - I had to wait, wait - this is exactly what I saw in your video.

To me, it looks like you need more front tire with stick to be faster.

Your 235/315 setup, unless that front 235 is more like a 255, isn't a setup that I could be fast with. I think gt3s respond far better with as much front tire jam'd in there as possible.



please disregard my observations if you disagree

LVDell

Scott and I have talked at length about the "why" and "what" to learn from this experience. If you watch the video enough, it becomes very clear what happened and why. As a point of reference, the track was VERY slick and slow for the event.

Seth Thomas

Really trying to add to this conversation but I am not agreeing with you guys on this or seeing the same thing in the video. Maybe you guys can help me out with where you see the front end losing grip in the video because I am not seeing it. I see the wheel turn, it points, and it stays in the line of steering input throughout the turn. It does this in 4,5,6 and in South Bend. It understeers in Oak Tree but that is because the line taken.

996FLT6

^ I don't see front stepping out either. Looks like rear is stepping out ESP with the countersteering scott is doing in certain parts of track and it's not countersteering because of understeer- car doesn't look like it's plowing- looks neutral to me. Mike

himself

Seth,

Just as a point of reference, where do you generally set your sway bars (GT3 and Bimmer)? [if it is possible to generalize].

-td

SH || NC

The front didn't feel like it was washing out anywhere really (it felt better than November), just the rear end felt skittish.

What I may do is render my November lap side-by-side with my May lap.

November
http://www.vimeo.com/17098077

Great info guys; thanks.

997gt3north

Because you said this, I made myself re-watch the video again - I also reread what I wrote to make sure it came across as I meant it to come across. I stand by what I said, but I will repeat specifically again what I was seeing.

To me the car basically appears neutral but this specific session reminded me of my first time at VIR with my GT3 on the OE N Spec MPSC+ tires with the big front rain channels. When I was going through 5 and 5a I wished that day I had more front end grip as the car just didn't have the front grip to really be on it - you had to go 85% as the front was just not gripping like the rear - when I watched the video again, this is exactly what I see - the car is working but the front is lacking some grip - this is why I also said it appears 'similar' to a hot greasy track / driving with over inflated hot tires.

My point was that I think given the tires of this specific car are not new, in fact they have many heat cycles on them, that the owner might consider putting 4 new tires on the car before making a statement that putting the rear bar to mid made the rear end snappy - it may have well done.

I can state from first hand experience, backed by Pro David Empringham driving my car on a day that my R888 started to go and again with a set of fresh tires, that setting up a car or making a definitive opinions about a setup on 'old tires', especially in a 911 that generally goes through rears faster than fronts, might work, or it might lead to entirely the wrong change. David thought my car, and it was, was dangerously loose, and it needed to be way tighter in order to go faster so he recommended doing so. I had heard about the R888s going off, especially in the rear, so I decided to put on a new set. I was lucky to run into David again shortly afterwards when he was working with a cup client and had him re-evaluate the car - he said the car was now perfectly neutral - and I gave him fully permission to test it out as I really wanted to make sure about my setup. So, my lesson is never try and set up a 911 with older tires or make definitive statements about the setup if the tires are old - put a fresh set on and then judge.

To the driver on the video, your 2:14 is nice and smooth for someone who was not 'confident' about the car - my comments were only an opinion to the extent that they can be of any use.

Since I do not use the tires in question, or drive a 996gt3, is the preferred setup for 996gt3 really running a 235/315? On the 997gt3, 255/315 seems to make the car very neutral and definitely gives the front better grip which can be exploited in sections like VIR 4, 5, 5A.

SH || NC

Cheers, I appreciate the feedback! The November event, I was more confident; the May lap didn't feel as good.

The NT01 setup is either a 245+315 or 235+315. The 245 rubs a little at full lock, so I am running the 235s up front for now.

I could go with 9" fronts, get new wheels and offsets to support more rubber, but I'm not ready for that yet.

Re: 5, 5a, 6, 6a: I really tip toe through this section; this will be one of the last sections I try to make up time on at VIR; its very tricky to me and lots of opportunities for bent metal.

997gt3north

Our camber, caster toe settings are actually very, very similar. I also have the RS wing - I run mine at 12% - my home track is Mosport so I use it to glue the rear end for turn #4 - but I found it also worked very well at VIR up the esses.

I'm not sure if your car has an upgraded LSD, I think it may from previous readings, but on my car pre my Guard upgrade and post the upgrade, I found that 5a,6,6a definitely felt much more planted after the upgrade. Especially in that section with the curbs and dirt, having the diff truly lock, dramatically to me anyways, changed the feel of the rear 'hooking up' - my confidence then grew about going WOT just at 5A apex and not worrying about the rear - to me it was a huge difference.

This again is why your video stuck with me - as I didn't in this section feel you were nervous about the rear (maybe you were) it looked more greasy and that you had to kinda go 85% through there - and thus my comment about front end / overall grip.

i say try some 245/35/18, 315/30/18 Kumho V710s

back to work


paul

996FLT6

For 6gt3 fitment 245(square) and 305(square) for kuhmos. Mike

SH || NC

I still have a brand new set of NT01s