05-08-2021, 10:23 AM | #23 |
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Hey guys, awesome thread. Exactly what I've been looking for. I have a set of PS4S on a M5C with a little over 5K miles on it. I've done about 4 track days so far and noticing the grip levels changing throughout the day and overall as the tires get more worn. I've done some reading on heat cycles and tire pressures but still feel like a dumb shit. Can anyone else tracking on these tires suggest the best cold pressures to start, what pressures I should look to maintain by bleeding throughout the day, and how many track events I can expect before they're done?
Also, I have been looking for replacements and considering some of the tires mentioned above by others but I can't seem to find any that fit the 789M wheels. For those who have switched tires to something more appropriate for track, did you have to get a new set of wheels and tires? If so, any suggestions for something that is reasonably priced and most bang for buck? Also what sizes fit on this car? Thanks in advance. |
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05-08-2021, 12:33 PM | #24 |
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Glad this was useful!
ABenChod I've been doing track days for about 20 years, going all the way back to my 2005 E60 M5 (also no MDM, sideways everywhere ) which had a terrible braking setup so I had to get upgraded hoses, fluid, pads and do some cooling work. BlueSteel13 Agreed on my last car, C7 RS6, I had Motul RBF600, so might do the same here, or go for the SRF. unfoundnemo Yeah spot on. Even when the tyres were actually way over the right pressure, I was getting low pressure warning lights. Didn't affect anything, and I had the Michelin sensors double confirming the actual pressures and temperatures. I know what everyone means about MDM - it's a lot of money to put into a wall. When I used to track my 650s, I'd keep the stability control on but that's because it's RWD and mid-engined and it's specifically tuned to be fastest with it on - when you put a McLaren into track mode it will switch off traction control but leave the stability control on, and it doesn't ever cut in, it just subtly manages the momentum of the car. I found with the M5 MDM that when powering out of slow corners, it would aggressively cut the power rather than just softly limit it, whereas in those same corners with traction fully off the car would power out and would quite happily be balanced as long as you were managing it on the steering. This might be an incorrect view, but for me knowing where the limits of the car are is more important so that I don't accidentally go beyond them. Once you're beyond them physics takes over, and no MDM will save you. But I'll give MDM another go on my next track day next month and see. Powerslide Yeah I didn't quite trust the app to start at the very low pressures it suggests, each time I came in it would tell me to reduce by 8 PSI which would means starting cold on something like 20 PSI. I think the car shouldn't really do more than about 20 mins out there, including a cooldown lap, and the trackdays I do are open pit lane all day, so I managed to get it to a point where half way through the first lap I'd be in the green, and about 15 minutes in I'd be in amber, so I'd push for a few more minutes and then start the cooldown. At the top of amber or into red, and the tyres just go - it's like floating around all over the place. And yes, no comparison in terms of feel to the M2. Haven't driven one myself but there were about 10 at the track day I was on, including CSs. But not a single one could keep up - as shawnhayes says, the M5 totally keeps up in the corners, and as soon as you're through onto the straight it's like you have a rocket booster. DJspecv Check out the Michelin Connect app. You can use it even if you don't have the Cup2 Connects with the sensors, and it'll tell you optimal recommended tyre pressures for your tyres. Question to the group. Has anyone managed to source and fit the M Performance pads which apparently exist. My dealer is totally lost - trying to fob me off with a carbon ceramic retrofit which is absolutely not what I'm after. I'm in the UK so I can't get any of the aftermarket stuff that you guys in the US have, and Pagid don't seem to have done the RS29s/RSL29s based on their website and dealers, so I think the best option I'm going to have is to fit the M Performance pads, but I'm struggling to get the dealer to know what I'm talking about. |
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05-08-2021, 01:26 PM | #25 | |
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Apparently this is how to get them. The part number is 34-10-8-092-822 - apparently. I got the tip from a user in this thread... https://f90.bimmerpost.com/forums/sh....php?t=1738603 Shawn |
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05-08-2021, 01:40 PM | #26 | |
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Hard question. Here's the main problem - 4800 pound car. So, pick your poison - start out at a tire pressure that's too high, and the tires get up to 42 psi when you run more than 40 minutes continuously. Ever been ice skating? That's what it's like when you get there on OEM tires. OR.... Start out at 20 psi like the Original Poster posts suggest which comes from the Michelin Connect App, and SLOWLY get the tires up to temp and pressure that's appropriate. Then the TPMS system will bitch at you incessantly. These are the choices. Unfortunate. I'm willing to live with either. Car is great either way unless you're trying to win a wheel to wheel race. Having run those tires, I suggest the following approach - run them at recommended starting pressure on track until you get them to 40 psi. Come in. Get all pressures FAST (TPMS can be used, but purists don't recommend). Adjust pressures in each tire individually so that your target hot pressure is no more than 37 for EACH tire. Ideally, after 25 minutes of hard track, each tire will be at 37 and STAY THERE. Depending on track, this will be a RIDICULOUSLY sounding low pressure for each tire cold. For mine, for VIR, this results in left front cold - 26, right front cold - 30, left rear cold - 28, and right rear cold - 31 STILL with this, after 35 minutes of HARD running, I can get the left front up to 41 psi and STUPID HOT TPMS temperature. This sounds nuts, I know. However, this is the best approach I've found for this car. Durability depends on your style and how hard you're driving. I've gotten three events (six full track days) and to and from each event out of the 4S's like this. Shawn |
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05-08-2021, 01:52 PM | #27 | |
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Good luck. Shawn |
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05-10-2021, 05:03 PM | #28 |
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Thanks for the replies and additional info!
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05-13-2021, 09:20 AM | #29 |
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Crack Resistant Windshield Glass
2 track days and replaced the windshield due to rock chip.
What's the answer? Stronger, chip resistant glass, chip resistant film similar in theory to PPF? |
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05-13-2021, 10:00 AM | #30 | |
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Both cracked at the top making long lines spanning ¾ of the windshield… My guess is that there is something with the steel A pillars and the carbon roof not handling stress the same way. Also temperature expansion is not the same. Never had that problem with my 2016 M4 though… The 3rd one survived the 1st track day
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06-02-2021, 06:29 AM | #31 |
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I just did a track day at Grattan, a very technical track and agree completely. Although I am doing some upgrades it is fantastic right out of the box. I had the fastest top speed and was among the faster lap times against track spec Porsches, Jags, etc. Thanks for sharing.
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06-29-2022, 08:13 PM | #32 |
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I want to change the fluid to Castrol SRF. How much do I need to buy?
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07-01-2022, 02:02 AM | #33 | |
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07-03-2022, 12:25 AM | #34 |
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Oldschool thread. Glad it's still helpful. I'm about to kick off my 2022 season, a bit later than usual.
"Ring taxi" official bmw endurance pads still going strong. Extremely worthwhile purchase for anyone tracking, highly recommend, direct from BMW so super easy. Castrol SRF you need 2 liters (I underbought first time). |
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07-04-2022, 11:03 PM | #35 | |
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07-05-2022, 09:41 AM | #36 | |
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07-06-2022, 11:30 AM | #37 | |
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Glad to know you're still tracking this beast. The number of "it's not a track car" comments I got were stupid. Shawn |
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07-06-2022, 11:49 AM | #38 |
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Does the F90 have front brake vent grates like the G80? I was at the track and this guy pulled his but I didn't see any
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07-06-2022, 12:18 PM | #39 | |
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07-06-2022, 01:10 PM | #40 |
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07-06-2022, 01:14 PM | #41 |
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The ABS controller can. That's the way the ABS and the DSC work on the F90. It controls yaw with individual braking.
The 2018 was WAYYYY heavy using the rear brakes in M-sport mode. The only way to keep it from doing that was DSC off, and full DSC off may be "fun" but it isn't so much "safe" in a big heavy car that can reach 160mph pretty quickly. The 2022 is MUCH better at keeping the car fully controlled while not overusing the rear brakes. Shawn |
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07-06-2022, 01:15 PM | #42 | |
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07-06-2022, 01:22 PM | #43 |
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On the early cars, it's called "M-dynamic" mode.
I don't remember what it is on the LCI cars, but mine engages when I hit the M2 button and it takes everything to track mode. It's engaged by hitting the DSC button. DSC "off" is press and hold. And car goes nuts with warnings. Shawn |
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07-06-2022, 01:24 PM | #44 | |
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