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      06-15-2019, 01:26 AM   #1
Conte_81
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M235i Xdrive Drag Race Tips?

Hi All,

I have 2015 M235i. Car has Pure Stage 2 turbo, downpipe/intercooler/intake and a Remus axleback.

The car was tuned and made 406hp and 390tq at the wheels. My goal is to break I to the 11's. I ended up at 12.1 in the 1/4mi.

What else can I do? I've tried both launch control and brake boosting with DTC and DSC on/off.
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      06-15-2019, 01:01 PM   #2
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Quote:
Originally Posted by Conte_81 View Post
What else can I do?
Reduce the car's weight somehow, some way.
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      06-15-2019, 02:44 PM   #3
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You can probably shave down that 60ft to 1.6 with AWD. I cut a 1.8 60ft with a rwd 340i on runflats so you should be able to lose a couple tenths with some more practice. Have you tried lowering tire pressure? Taking out the rear seats and a more aggressive tune will also help. Keep going, you're close!
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      06-15-2019, 05:37 PM   #4
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higher tire pressure may help since the launch is not an issue with xdrive.
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      06-17-2019, 01:02 PM   #5
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We have made two runs in our M240I x drive in the high 11 with a trap speed of 110 - it is all about 60 FT time and the DA- both of our 11 runs had 60ft 1.65 and 1.69 - we are consistently in the low 12 - Our car is Dinan stage one and a dinan CAI on Michelin Super sport tires
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      06-17-2019, 03:06 PM   #6
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I've done quite a few passes and there isn't too much magic for the x-drive cars. 11's with launch control or left foot braking with mods in the sig.

A Pure turbo stage 2 should have no issue getting into the 11's and I would expect your trap speed to be significantly higher. As others have said your 60' times are soft. I'm typically in the 1.6's. I would start with getting the tune looked at. Something seems off.

I haven't tried it yet, but I hear meth is your friend.
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      06-18-2019, 07:24 AM   #7
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Coming from a '17 m240i that had sport DP, CAI, and JB4 map 5 so take this however.

I upped from the 225/245 setup to 235/265 setup. Did a 1/8th drag and did it in 7.76 even with the wider tires and tire prep on the track, still spun off the line. Tires were sticking to the track, but when you're putting that much power down, even xDrive doesn't work wonders. Granted, I was on Conti DWS06 19" tires at the time.



What dropped my 0-60 and even my 1/4 mile time on Dragy was going to 18" MPS4S 235/265. Broke into the 11s on the street with dragy just by switching my wheels/tires. I'd start there honestly.
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      06-18-2019, 07:37 AM   #8
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I did 3.6s 0-60mph on the streets just by going from 19s Conti DWS06 to 18s MPS4S. Dragy was 12.1s with DWS06, down to 11.9s with the MPS4S. Wheels/tires play a big roll with launch. If you check my video below, played at .5 playback speed, you can see I launch before the green, but wheel spin keeps me in place for that split second before the green shows. xDrive with the wrong tires will kill your times.

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      06-18-2019, 07:59 AM   #9
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Quote:
Originally Posted by Joe240 View Post
I did 3.6s 0-60mph on the streets just by going from 19s Conti DWS06 to 18s MPS4S. Dragy was 12.1s with DWS06, down to 11.9s with the MPS4S. Wheels/tires play a big roll with launch. If you check my video below, played at .5 playback speed, you can see I launch before the green, but wheel spin keeps me in place for that split second before the green shows. xDrive with the wrong tires will kill your times.
slow the video down and your car is moving before the green haha. that 11.9 could be artificial but regardless, nasty times for FBO.

i couldnt get better than 12.6s on FBO BM3 AGG e30 OTS with OEM wheels and MPS4S stock tires (225/245). my 0-60ft was something like 2.0s at best. Start seems to be the make or break it.

for RWD people make the front tires super high PSI and rears like 30 or less even. for xdrive maybe run less than 30 all around. Also take out the rear seats, thats 50lbs lol.
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      06-18-2019, 08:10 AM   #10
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Quote:
Originally Posted by jdag001 View Post
slow the video down and your car is moving before the green haha. that 11.9 could be artificial but regardless, nasty times for FBO.

i couldnt get better than 12.6s on FBO BM3 AGG e30 OTS with OEM wheels and MPS4S stock tires (225/245). my 0-60ft was something like 2.0s at best. Start seems to be the make or break it.

for RWD people make the front tires super high PSI and rears like 30 or less even. for xdrive maybe run less than 30 all around. Also take out the rear seats, thats 50lbs lol.
I wasn’t running meth nor PS2 turbo so wasn’t FBO. Just needed wider tires and even then I would still spin on the streets. Never got time to do a drag run on the track with the MPS4S, but I probably would’ve red lighted using the same technique I did with the DWS06.

People under estimate the importance of wheels/tires. Wheels can be heavy and 2lbs per wheel and 1lb per tire is still 12lbs if I sprung weight. Make that tire compound softer and you can launch better. What also helped with the change is MPS4S set was a fraction shorter than the DWS06 (18s vs 19s) which also helps with acceleration times at the cost of top end speed.
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      06-18-2019, 08:13 AM   #11
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Here's my draggy times with the MPS4S this was on the street, not strip, and I still had wheel spin. But again, this was quicker than what the DWS06 did on the strip with tire prep. If putting down >400hp at the crank, gotta go wider wheels and softer compound with these cars.
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      06-18-2019, 08:30 AM   #12
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https://www.2addicts.com/forums/show....php?t=1528593

Honestly, I don't think you need more grip with xdrive car for drag race.

I've done launch with winter tire, it still doesn't slip.

Also, wider tire does not always help the launch grip. (unless the tire pressure lowered way down)
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      06-18-2019, 08:35 AM   #13
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But you stated in your post that you’re bone stock. Regardless of winter tires or not, xDrive m240i dynos around 300hp at the wheels go FBO and you’re easily 70-100ho over that at the wheels. Trying doing a quarter with that and you will have wheel spin.

Also, the difference between 245 and 265 is almost a full 1”. And if you consider proper wheel width sizes for mounting as well, that can equate to over an inch in contact patch. Yes, tire pressure also plays a factor, but with consistent air pressure between the 2, the wider tire will provide more grip
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      06-18-2019, 08:52 AM   #14
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Quote:
Originally Posted by Joe240 View Post
with consistent air pressure between the 2, the wider tire will provide more grip
it will provide more lateral grip for sure, but not necessarily more longitudinal grip. (again, depends on pressure and compound)

With same vehicle weight and same tire pressure, wider tire just change the shape of contact patch. With lower pressure, yes it will have more contact patch area.
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      06-18-2019, 09:00 AM   #15
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Quote:
Originally Posted by TajoMan View Post
it will provide more lateral grip for sure, but not necessarily more longitudinal grip. (again, depends on pressure and compound)

With same vehicle weight and same tire pressure, wider tire just change the shape of contact patch. With lower pressure, yes it will have more contact patch area.
Wider tire on same width wheel, yes. Wider tire on correctly sized wider wheel, contact shape stays the same. That’s why manufacturers have a recommended wheel width for each tire (and that changes per tire as well
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      06-18-2019, 10:08 AM   #16
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This thread takes me waaay back to when dragging was THE street scene (not really my scene, but you can't help but have a lot of it rub off). The launch is about 90% of your time (or what you can change and improve), and there are tons of details regarding tire setup, pressures, etc. Definitely tire-specific/car setup specific. You can probably get apps that let you practice your tree-timing, and those would be quite worthwhile. It also can help to get your tune set to optimize launch torque vs. mid-run (I know many soften the low end so they don't break out as badly at launch, but DK how that works on an xdrive).


Quote:
Originally Posted by Joe240 View Post
Wider tire on same width wheel, yes. Wider tire on correctly sized wider wheel, contact shape stays the same. That’s why manufacturers have a recommended wheel width for each tire (and that changes per tire as well
This is incorrect. Size of contact patch is a function of weight and psi (so lower psi gives bigger patch, among other benefits). Wider tires mostly give more rubber overall, so on a racetrack there is more resistance to heat and wear. Wider rims mean better-supported sidewalls (not always a good thing in the drags), and more weight. Tire width isn't that big a deal - I've seen a car on much narrower dedicated drag tires regularly eat the lunch of more powerful cars on wider street tires. Rotating weight, especially on driven wheels, is a big deal. And, if permitted, tire prep sprays can also be a help (to e/t but your wallet).
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      06-18-2019, 02:22 PM   #17
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Lot of info all good but after many too many years and 1000's of passes on both the 1/8 and 1/4 in cars as fast as mid 9 - Track prep - Weather - make a huge difference at any time on any car - watch any drag racing show - it is all about getting off the line and maintaining traction - cars like the X drive BMW automatic pretty much point and shoot cars - I prefer brake boost but launch control is fine if you are not worried about RT - these little coupes are great to about 800 ft and then unless you have turbo upgrades erc they just do not have the HP at the big end
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      06-18-2019, 02:23 PM   #18
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Quote:
Originally Posted by Maynard View Post
This is incorrect. Size of contact patch is a function of weight and psi (so lower psi gives bigger patch, among other benefits). Wider tires mostly give more rubber overall, so on a racetrack there is more resistance to heat and wear. Wider rims mean better-supported sidewalls (not always a good thing in the drags), and more weight. Tire width isn't that big a deal - I've seen a car on much narrower dedicated drag tires regularly eat the lunch of more powerful cars on wider street tires. Rotating weight, especially on driven wheels, is a big deal. And, if permitted, tire prep sprays can also be a help (to e/t but your wallet).
Actually I am correct. My original comment suggested wider wheels & tires to accommodate a better launch, and my comparison for my sake on the m240i was going from DWS06 (all season tires) to MPS4S (summer tires) and I had mentioned using a softer compound tire as well (all season isn't as soft as summer). I had also mentioned that I went from 19" all season tires to 18" summer tires. I didn't mention how the thicker sidewall does help with launch because it allows for more flex in the sidewall, thus increasing grip for launch. I agree, tire pressure and softer tire compound do play a roll in launch capabilities, as well as the vehicle itself and the driver. However, I am correct in saying that increased tire width on a properly sized wheel will indeed increase the contact patch of the tire. What classifies a "properly sized wheel" is the manufacturer.

Lets take a look at the good ol' Tirerack website on this matter:
https://www.tirerack.com/tires/tiret...jsp?techid=199

"Because the width of the rim will influence the width of the tire, a standard rim width for every tire size is assigned and must be used."

When looking at tires, lets say the 265/35ZR18 MPS4S that I was running in the back, Michelin states a Measured Rim Width of 9.5" and a section width of 10.7" (referring to the link above, the section width is ONLY met when mounted on the standard rim width for that tire size (in this case, 9.5"). HOWEVER, the tire can be mounted on wheel widths ranging from 9" to 10.5"

Back to another article on Tirerack regarding Rim Width Range:
https://www.tirerack.com/tires/tiret...jsp?techid=198

"The width of the rim will influence the width of the tire. A tire mounted on a narrow rim would be "narrower" than if the same size tire was mounted on a wide rim."

That link also has a nice little chart to give you an idea (relatively) how wheel width affects section width. But, in essence it is like this: if you have to pull in the sides more, then you have to get the extra length from the section width. This is done by pulling part of the contact patch in to the center of the tire so it can be mounted on the wheel. This causes a "Bulge" look on the tires. Putting a tire on a wider wheel than the measured rim width will cause the sidewalls to start impedding on the section width, which means it is now part of the contact patch.

YES: Lowering the air pressure of a tire that is the same width mounted on the same width wheel will increase the contact patch. Softer compound tires will increase launch capabilities. Larger sidewalls allow for more flex to increase launch capabilities [why dragsters use such large sidewalls (yes at a lower PSI as well)]. Camber and Toe configuration of the suspension will affect contact patch. Weight of a vehicle plays into the width of contact patch.

There are a ton of factors that can play into the launch capabilities of a vehicle. HOWEVER, if all other variables are kept the exact same, increasing tire width by mounting it on the appropriately sized wheel WILL increase grip because it will have an increased section width. If going to purchase new tires, then ensuring it is a softer compound, as well as wider and mounted on the correct width wheel would be a good starting point for lowering your 60ft times (again, keeping all other variables the same meaning driver and launch technique) and your 1/8 and 1/4 times (other variables come into play once in motion).
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      06-18-2019, 02:43 PM   #19
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Just a quick note to add what I said above - The M240I x drive is not built to be a drag car - it does well but it really shows off on a road course - Also if you read the owners manual you will see it says don't use launch control with out sufficient time between runs - there is a reason for that as high rpm launches put abnormal strain on the transmission etc - so launch at about 2500 rpm use sport plus and have fun - If you want 11 all day get a Redeye or Mustang GT if you want 10 off the showroom floor get a RS3 or a GTR
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      06-18-2019, 02:49 PM   #20
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https://ls1tech.com/forums/cadillac-...alignment.html

As you see in the picture from above link, wider tire (even with properly wider rim) does not necessarily have bigger contact patch.
It just changes the shape of contact patch. (elongated more on sideway)

Contact patch area is solely function of weight of the car and tire pressure. (within reasonable tire width of course. not talking about bicycle tire like width)

As mentioned above, proper rim witch is for optimal sidewall support.
The Tirerack article just says 'tire width' not 'contact patch'.
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      06-18-2019, 02:53 PM   #21
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https://www.tirerack.com/tires/tiret....jsp?techid=10

This is basically what I am talking about.

https://en.wikipedia.org/wiki/Contact_patch

This also says 2 major functions are the load and pressure.
(it also says that the relationship is not linear)
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      06-18-2019, 02:58 PM   #22
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Quote:
Originally Posted by TajoMan View Post
https://www.tirerack.com/tires/tiret....jsp?techid=10

This is basically what I am talking about.

https://en.wikipedia.org/wiki/Contact_patch

This also says 2 major functions are the load and pressure.
(it also says that the relationship is not linear)
Thanks everyone, some good tips and tricks for me to try out. Appreciate all the insights.
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