Sebring: GTS Impressions

[redrumm3]

I just returned from my first track session with the GTS at Sebring. The event was two days and one night session on Saturday night. I want to preface my thoughts here by saying that I have not been on track with a “street” car in some time. I race a BMW E36 M3 regularly and it has considerably more downforce, tires and suspension and less weight than the GTS. That being said I thoroughly enjoyed the car and it is superfast for a street legal car.

Tires: I will start by saying that BMW’s recommendation for tire pressures is way too high for the Cup2’s. I started the first session at their recommended pressures and I found the car to be moving around a lot. I continually adjusted them down throughout the weekend and settled at 36 psi (F) and 38 psi (R) hot. I still think this is too high but going lower caused the front tires to roll more on the sidewall than I liked. I think the sweet spot is more like 32 psi (F) and 34 psi (R) hot but the car does not have enough camber to run the tires that low. After two and one half days running on the track the tires are used up. I did get some minor blistering on the outer edge of the front tires, again from the lack of camber. The tires were really good for the first 5-6 laps, but began to fall off after that. If there is a weak spot in the car, I think it is the tires. The car can definitely use more tire.

Suspension: I ran the car in the street setup, as delivered from the dealer, throughout the weekend. I didn’t make any adjustments to the compression or rebound on the shocks. My intent was to get a baseline to work from in the future. The car was a little softer and had a little more roll in it than I would have liked. The car also has a lot of weight transfer under braking in this setting. Sebring is a rough circuit and that is why I elected to go with the street setting. Knowing what I know now I would have run the car in the race setting. I think the car will have more speed in the race setting and will be a little better balanced, have less weight transfer under braking and be more planted. Overall the car handles really well with good grip and balance. There is some understeer in the car, more than I personally prefer, mostly in the slow corners but it is easy to control with the throttle. My guess is that the car will be a little more neutral in the race setting. I am going to have the alignment checked and I will post the results and then lower the car to the race setting and do the same. I also intend to put the car on some scales and properly corner weight the car.

Aero: I ran the car in the race setting with a fully extended splitter and the wing in positon two. Ultimately, I changed the rear wing to position three. My purpose for doing this was to try and settle the rear end under hard braking and plant the rear end under the fast sweeping corners. I think it was helpful and I didn’t notice any decrease in top speed. It’s hard for me to be objective here since I am used to running a car with a lot more downforce.

Brakes: Phenomenal! I pounded on them hard all weekend. They took everything I could throw at them. Never any fade throughout any session. The car is sensitive to trail braking and the rear end is a little unstable under hard braking. I can attribute this to the braking zones at Sebring being rough and the fact that the car was in the street setting. I would expect any issues here to be eliminated in the race setting and with the proper shock settings. I can’t say enough good things about the brakes.

Software Settings: Turn off MDM and DSC. They are useless on the track and way too intrusive. I played around with the shift and steering settings all weekend until I found settings I was comfortable with. I won’t go into detail here because I think there is going to be a lot of personal preference in this area, but I was able to find settings I really liked on the car that suited the feel I was looking for. Also, I think this is an area where the car gets a bad rap, unfairly. You can truly tailor the car to suit your driving style and needs, but without sufficient seat time pushing the car near its limits that is difficult to do. I doubt many reviewers of the car have had the opportunity to do this.

Seats: The seats are not sufficient for this car on the track. The car clearly needs the European seats and harnesses. Too bad we didn’t get them. With the high limits of the car, it was a constant struggle to keep myself in position. Enough said.

Fuel: The car is thirsty, a full tank lasted 50 minutes max. I did get some fuel starvation near the end of each session on the long right hand corners, but the tank was nearly empty. At the track the water tank lasts one fuel tank.

Overall: The car is very rewarding to drive on a race track. Once dialed in it is well balanced, easy to drive and Superfast, and it can hang with any street car out there. I’ll post video and images to prove that once I get them edited. According the my MLaptimer I was able to get down to a 2.26.3 with a top speed of 148mph and the car pulled over 1g in the corners. I am happy with those numbers considering it was my first weekend in the car. More seat time in the car and adjustments to the suspension will ultimately result in a faster lap. There is more speed to be found in the car.

[VCP]

Well explained. This speaks volumes. "You can truly tailor the car to suit you driving style and needs, but without sufficient seat time pushing the car near its limits that is difficult to do. I doubt many reviewers of the car have had the opportunity to do this."

[dh3622]

Great report card; well done, factual. Good job!!

[heckyeahbro69]

Next time you go, let me know. I'd love to run with a gts on track even though you went 3 seconds faster then I've gone. I was fighting a bad off power push though.

[robbys3m3]

Great writeup! Can't wait to see your car in person someday

[vladberca]

Great review! Much better than the nonsense from most of the magazines!
Waiting for the clips, too!

[mu2002cs]

Thanks! Your observations are consistent with my experiences at COTA. Some further thoughts:

1) My Cup tires lasted 350 miles. COTA is very smooth and the tires were mounted on the carbon fiber wheels. But, at the end of 3 days, they were trash

2) I also ran the "street setup" on the suspension. I have since removed the spacers and re-aligned. For the next track session, will dial in a couple of degrees of camber.

3) As stated, the brakes are incredible! I was surprised at how well they slowed the car at 146 mph (my conservative top speed on the back stretch, with 10 days of ownership!)

4) I installed a 5 point "G Force H-Strap" harness. Can't even imagine driving the GTS on the track without it. While this harness is not optimal, it's the best you can do with the stock seats.

Overall - an awesome car that tests my skills. I have done 3 back road tours in the car. What a blast on the back roads.

One last note. I mounted Michilen A/S 3s on the Orange wheels and put the Cup tires on the Carbon Fiber Wheels. This gives me more flexible driving capability.

[jml]

Might as well put a shell in it. The Euro seats seem to be ruffling some features at the NA office w/r to warranty. When I was first inquiring about the car about a year ago, I was assured the seats would be available, then that turned into availability as an after-sale option, and now it's turned into "voids warranty". There are some really nice options in micro-fiber from Recaro and Status.

I saw your G-force setup at COTA and I think you might want to consider how safe that would actually be in an accident. Maybe ask HMS for their opinion to make sure you'd not be better off with the 3-point. They do consultative work for a few major racing sanctioning bodies. Having been in a very bad accident recently, I'm a bit overly sensitive to safety belts.

[mu2002cs]

Originally Posted by jml

Might as well put a shell in it. The Euro seats seem to be ruffling some features at the NA office w/r to warranty. When I was first inquiring about the car about a year ago, I was assured the seats would be available, then that turned into availability as an after-sale option, and now it's turned into "voids warranty". There are some really nice options in micro-fiber from Recaro and Status.

I saw your G-force setup at COTA and I think you might want to consider how safe that would actually be in an accident. Maybe ask HMS for their opinion to make sure you'd not be better off with the 3-point. They do consultative work for a few major racing sanctioning bodies. Having been in a very bad accident recently, I'm a bit overly sensitive to safety belts.

We made quite a few inquiries before choosing this setup. The crotch strap is not ideal as it's too far forward. However, it does keep the belts snug around the hips. The important part about this setup is proper installation and use of the H-Strap....keeps the harness from slipping off your shoulders. Obviously, the Euro GTS seats are ideal.

[johnr265]

redrumm3, just curious what you ended up liking with the throttle, steering and shift maps?

Also, for you and mu2002cs, do you plan to add more camber to the front and if so, how (still unclear to me that it is adjustable from the factory). Makes no sense to just accept destroying the outer edge of the front tire. Not only do you go through tires faster but you drive slower because of less contact patch.

[Paul-Bracq-BMW]

Originally Posted by redrumm3

Tires: I will start by saying that BMW’s recommendation for tire pressures is way too high for the Cup2’s. I started the first session at their recommended pressures and I found the car to be moving around a lot. I continually adjusted them down throughout the weekend and settled at 36 psi (F) and 38 psi (R) hot. I still think this is too high but going lower caused the front tires to roll more on the sidewall than I liked. I think the sweet spot is more like 32 psi (F) and 34 psi (R) hot but the car does not have enough camber to run the tires that low. After two and one half days running on the track the tires are used up. I did get some minor blistering on the outer edge of the front tires, again from the lack of camber. The tires were really good for the first 5-6 laps, but began to fall off after that. If there is a weak spot in the car, I think it is the tires. The car can definitely use more tire.

Looks like Captain Unknown GT4 did his Nurburgring laps with 2.3 bar (33 Psi) front and 2.1 rear (31 Psi) hot pressure as did Sport Auto Magazine...

His post here: http://f80.bimmerpost.com/forums/sho....php?t=1311130

[mu2002cs]

Originally Posted by johnr265

redrumm3, just curious what you ended up liking with the throttle, steering and shift maps?

Also, for you and mu2002cs, do you plan to add more camber to the front and if so, how (still unclear to me that it is adjustable from the factory). Makes no sense to just accept destroying the outer edge of the front tire. Not only do you go through tires faster but you drive slower because of less contact patch.

The race team suggested 2 degrees to start. You are correct, the outer edge is toast while the inside is not too bad.

[CanAutM3]

Good objective review, I can relate to that . Thanks for sharing.

I wonder why BMW did not make the front camber adjustable on a track focused car such as the GTS . I actually think they should make it more adjustable even on the standard M4.

It will be fun to follow your evolution as you progressively tune/optimize the car. Please keep us posted .

[redrumm3]

Originally Posted by johnr265

redrumm3, just curious what you ended up liking with the throttle, steering and shift maps?

Also, for you and mu2002cs, do you plan to add more camber to the front and if so, how (still unclear to me that it is adjustable from the factory). Makes no sense to just accept destroying the outer edge of the front tire. Not only do you go through tires faster but you drive slower because of less contact patch.

I don't have the benefit of my setup sheets in front of me so I am going to have to be general in my comments. I started in the least aggressive maps for each and moved to a more aggressive one until I felt it was too aggressive and then backed off. My intent was to find throttle, shift and steering settings that weren't too aggressive and still allowed me to keep the car balanced.

As an example, I found that the upshift on one section of the track, a fast left hand sweeper, could be too aggressive and unbalance the car. It would cause some wheel spin, so I backed it off so that I could keep my foot planted in the throttle throughout the turn.

[redrumm3]

Originally Posted by Paul-Bracq-BMW

Looks like Captain Unknown GT4 did his Nurburgring laps with 2.3 bar (33 Psi) front and 2.1 rear (31 Psi) hot pressure as did Sport Auto Magazine...

His post here: http://f80.bimmerpost.com/forums/sho....php?t=1311130

I am aware of Captain Unknown GT4's tire pressures and I am not suggesting that the pressures I was running are optimal, merely that throughout the weekend that is where I ended up with mine. I believe the optimal pressures for the Cup2's are lower than what I was running, but I could not run them any lower given the lack of camber the car has in the front end and the track temp and ambient air temp that day.

Also, the tracks in Europe are vastly different than what we have here in the US. I have hundreds of laps on the Nurburgring and Spa and there is no comparison to Sebring. Generally speaking, the European tracks are faster and more sweeping than what we have here in the US. US circuits are shorter, slower and don't flow like the European tracks and place different demands on the tires and setup. I have no doubt you can run lower pressures on the European circuits.

Different track, day, setup, temps therefore different tire pressures.

[redrumm3]

Originally Posted by johnr265

redrumm3, just curious what you ended up liking with the throttle, steering and shift maps?

Also, for you and mu2002cs, do you plan to add more camber to the front and if so, how (still unclear to me that it is adjustable from the factory). Makes no sense to just accept destroying the outer edge of the front tire. Not only do you go through tires faster but you drive slower because of less contact patch.

Going from the street setup to the race setup will probably give you some more camber just because of the change in suspension geometry, but it will not be enough. The camber on the front by itself is not adjustable on the GTS. I am going to have to go to some adjustable camber plates for the front struts to get the necessary camber.

[redrumm3]

Originally Posted by CanAutM3

I wonder why BMW did not make the front camber adjustable on a track focused car such as the GTS .

Good question.

[Captain Unknown GT4]

Glad to get some owners feedback rather than those magazine, thanks Redrum.

Hope not to offend anybody, as my english is poor my wrighting is often interprent in a direct way.
First of I think tires will have a harder time if one drive high street setting on the average modern GP track layout. More roll and pitch and not that sweetspoot camber and toe. What ever the data show in that case a forum member check alignment vs street and track, the big difference is there..Instant one notice from the drop only to track(no alignment is in need) setting that now car is way more aggressive in turn in, it tramline way more on street and it work tires much better on GP track layouts..all in all big difference vs streetsetting driven on GP track layouts.

What ever sebring ruff and bumpy tarmac it should sit low track setting on that track layout. Rebound and compression etc should be ok as well in stock track setting, if so take it from there and change that(rather than have the high setting in car)
High softer street setting will give tires far from optimal performance on a GP track. Thats Only for street, and Nurburgring wich is the mother of all streets.

Also my 2 cent is that sport auto did get the tire pressure right, they drive same pressure on ring as they did on 2.6km GP track hockenheim. I did use that pressure instant and It is sweetspoot. But what also is importent Is to check tire inside temp as cup tire work optimal between 70-90 degrees. Also its not easy to keep whitin this range if wrong Bar pressure as well high street setting, tires will be overheating.

Not only will you see this as computer screen will show 90+ degrees up to 100+. This is the reason bits come lose from tire, they overheat. If you get above 90 degrees it no ide to keep driving-stop and re-think whats going on. Drop car to track-then instant on GP track it will work tires overal better. Check pressure. I would say you start to high, and not sure how many laps you made prior to you settle for your pressure, also I would say what you then settle for was to high as that was 36 front and 38psi rear. Thats to high and if you settle for this that mean you drive to many lap even higher prior to this?

Its very easy to wear these tires out premature if going a few to many lap on wrong pressure.

One must see to it to stay between 70-90 degrees in tires, if you cant do that wich is cup tires optimal temp then stop and rethink as somthing is wrong. Could be drivingstyle, outside to high sunny temp, but most likely wrong street setting on track. Combined with wrong pressure. Its a front engine car, front tires should have higher pressure than rear.

This is what to many magazines done wrong I am sorry to say. Still as you did its ok to try street setting on that track, but its a costly test as tires wear out faster. Track setting will solve everything and please just try the pressure I drove, wich also sport auto drove. My tires have no need for more camber, sweetspoot wear front and rear. Sure SPA and Nur might be as well more kind to tires than your track Sebring?! But they are simular lenghts and overal fast tracks? (SPA and Sebring.)

Originally Posted by Paul-Bracq-BMW

Looks like Captain Unknown GT4 did his Nurburgring laps with 2.3 bar (33 Psi) front and 2.1 rear (31 Psi) hot pressure as did Sport Auto Magazine...

His post here: http://f80.bimmerpost.com/forums/sho....php?t=1311130

[WestBankM4]

Great insight and nice report OP. Very good thread, I'm enjoying it.

[johnr265]

OK, here's my current understanding of things. Thanks to IND for doing a significant amount of legwork so far.

No recent BMW has come from the factory with adjustable front camber and it would appear that while early on there was a KW fitment with camber plates, BMW may either have felt it wasn't weather proofed enough or potential spring noise was unacceptable as an OEM fitment and they went with a fixed strut top. -2 may be enough for a long "street/track high speed course" like the 'ring but for most US tracks, which are tighter/smaller, more camber is necessary to not destroy the outer edge of the tire. Remember, it is not just about wear rate being too fast but grip being sacrificed at the limit (and I strongly believe that if you improve the grip up front, the understeer mentioned above will go away). Lowering to track height helps with certain aspects of the geometry but does not fix the lack of front camber. A car this heavy with the engine in the front and sticky tires should probably be running at least 3 degrees of camber up front. Time will tell the actual best number. So far, -2 in the rear seems pretty good.

The guys at IND reached out to KW and they are all on board with an OEM level camber plate that will be better weather proofed than their current aftermarket one. It likely won't be available until early next year but KW will design it and IND will purchase and distribute (and then we can buy)

[redrumm3]

Originally Posted by johnr265

.

The guys at IND reached out to KW and they are all on board with an OEM level camber plate that will be better weather proofed than their current aftermarket one. It likely won't be available until early next year but KW will design it and IND will purchase and distribute (and then we can buy)

Good info, thanks for the research.

[Paul-Bracq-BMW]

Originally Posted by redrumm3

I am aware of Captain Unknown GT4's tire pressures and I am not suggesting that the pressures I was running are optimal, merely that throughout the weekend that is where I ended up with mine. I believe the optimal pressures for the Cup2's are lower than what I was running, but I could not run them any lower given the lack of camber the car has in the front end and the track temp and ambient air temp that day.

Also, the tracks in Europe are vastly different than what we have here in the US. I have hundreds of laps on the Nurburgring and Spa and there is no comparison to Sebring. Generally speaking, the European tracks are faster and more sweeping than what we have here in the US. US circuits are shorter, slower and don't flow like the European tracks and place different demands on the tires and setup. I have no doubt you can run lower pressures on the European circuits.

Different track, day, setup, temps therefore different tire pressures.

Thanks for explaining. Cheers!