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      12-19-2016, 06:34 PM   #1
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Question F31 340i M / Break-In finally over -> Handling has to be optimized

Hi,

i just finished the break-in for my 340i M Touring RWD and gave it a go on the Autobahn and backroads and everywhere. The car is good, the engine is phenomenal (i seriously didnt expect it to be THAT good) but (and that was something that i felt immediately from the beginning) the handling and steering is not up to par.
The steering lacks confidence and feedback, the overall ride is bumpy (especially on the Autobahn) and the front axle feels kinda nervous and understeering at the same time. Whereas the rear axle is more or less planted with the expected coming loose now and then giving summer tires, 40i and RWD.

The setup:

FA: Bridgestone Potenza S001 RFT 225/40 R19
RA: Bridgestone Potenza S001 RFT 225/35 R19

Wheels are the (very heavy) M403.

I already put some thought into it and have some ideas but wanted to get some input from you folks here.

So what adjustments and different setups would you suggest?

Cheers

ImI
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      12-19-2016, 09:36 PM   #2
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Do you have the adaptive suspension? I find handling pretty decent with that setup, but the steering is really twitching (especially around 12 o'clock when driving straight).

Another user had said he put in M3 lower control arms and that really improved the steering response.
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      12-19-2016, 09:50 PM   #3
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Get rid of those tires first.
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      12-19-2016, 09:59 PM   #4
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Quote:
Originally Posted by Wires View Post
Do you have the adaptive suspension? I find handling pretty decent with that setup, but the steering is really twitching (especially around 12 o'clock when driving straight).

Another user had said he put in M3 lower control arms and that really improved the steering response.
Yeah, i have the adaptive suspension. Especially on the Autobahn at above 180km/h the front feels very light.

Nice hint with those M3 arms. Not the first thing i would consider but definitely good to know.
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      12-19-2016, 10:08 PM   #5
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Quote:
Originally Posted by cncmastr View Post
Get rid of those tires first.
Ok, my plans so far:

- Getting rid of the rims as they are VERY heavy which costs some acceleration also.

- Getting rid of the tires.

The rims will most likely be 19' BBS CH-R or OZ Ultraleggera 18 or 19'. Both weigh around 22lbs.

Tires i'm heading for MPSS or Pirelli P-Zero, which will bring an additional 6lbs in weight savings.

BUT, and here i am unsure: what specs to go?

I could imagine going square 245/35/19 on 8.5 rims.

I could imagine going 255/35/19 RA and 235/40/19 FA.

I could imagine going 245/35/19 RA and 235/40/19 FA.

I could imagine going square 235/35/19 on 8.5 rims.

And even some 18' combinations sound about right.

Basically i want to go as narrow as possible on the back and as wide as possible on the front to get as less understeer as possible, while still having no issues with too much spin on the rear axle.
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      12-19-2016, 10:52 PM   #6
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If you're actually looking to reduce rotational mass significantly get forged wheels especially if you're going to pay BBS prices.

I suggest upgrading to Bilstein B6 damptronic shocks before wheels. Or Dinan Shockware. You could pair either upgrade with stiffer, lowering springs

In general though the adaptive suspension has gotten pretty good reviews but maybe the wagon throws off some of the balance of the saloon
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      12-19-2016, 10:54 PM   #7
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It's the springs on the wagon. Do you have xDrive?

With respect to tire sizes staggering them will either reduce or induce under steer.
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      12-20-2016, 03:20 AM   #8
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Definitely square since you want to save weight.

8.5x19" with 245 tires is a nice setup for F30/F31.

245/35-19, 1% shorter than OEM size
or
245/40-19, 2% taller than OEM size

Personally I recommend 245/40, corrects the speedo and fills the wheel gap a bit better.
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      12-20-2016, 01:44 PM   #9
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Yes, going square on 245 R19 sounds good to me.

I am planning to get a Box from AC Schnitzer that raises HP to 380. Question is: Will this setup handle the power?
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      12-20-2016, 09:08 PM   #10
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Sorry, I missed the wagon aspect. Not sure how that changes the weight balance.

Square setup will give the best handling, and reduce understeer. If you are running summer tires, you shouldn't have an issue with traction with a square setup.

I put the Active Autowerke on my 340, but winter Pirelli's just don't cut it for traction. It'll break the tires loose at 70kph during the 2-3 upshift if you are hard on the throttle.
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      12-20-2016, 10:24 PM   #11
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What about going square with 245/40/18? Could steering and traction actually be better with those then 19s?
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      12-21-2016, 01:00 PM   #12
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Quote:
Originally Posted by ImI View Post
Yes, going square on 245 R19 sounds good to me.

I am planning to get a Box from AC Schnitzer that raises HP to 380. Question is: Will this setup handle the power?
Good plan. Some have fit 255 all around an F30 chassis, but that might be difficult to get the exact offset to do it.

Quote:
Originally Posted by ImI View Post
What about going square with 245/40/18? Could steering and traction actually be better with those then 19s?
It's likely both straight line traction and ride will be slightly better with a little more sidewall. 18's will also be a little lighter. IMO, it's the preferable wheel size for all around performance.

Also, with 18's you will have more options for tire sizes and they will all be a lot cheaper.
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      12-21-2016, 01:17 PM   #13
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I have a 340xi with adaptive suspension, though an F30. I was seriously disappointed with the OEM suspension. Very floaty, did not inspire confidence at all. Particularly after the MPPSK, the suspension just felt way outclassed by the engine and brakes.

So far I have done KW Street Comfort Coilovers, Dinan sway bars, and Bimmerworld rear subframe bushings. I was running staggered MPPSs on the OEM 397 wheels, those are seeing winter duty now and in summer I'll get a square 19" setup. I have been thinking 255/35/19 all around but I need to research the fitment more.

I've been very impressed with how this has transformed the car so far. I am not ready to 100% endorse this setup as I'm getting some creaking from the rear that really bugs me, and I haven't had time to take it back into the shop or call KW to diagnose. But the car is much flatter and more planted through the corners, and the ride is still actually quite compliant for an aftermarket setup. Squat and dive are greatly reduced as well, which has improved the driving experience more than I expected. Getting on/off the throttle and brakes is just a lot smoother. Overall, this seems like a great setup for a sporty daily driver; for heavy track use you'd probably want a stiffer coilover setup.

Not sure how much this applies to you, as I imagine the RWD adaptive M-Sport suspension is much better than on my xDrive. I knew from the getgo that I would need coilovers and swaybars to be happy with the car. Unfortunately the swaybar install is quite expense as the subframe has to be dropped.

The path you are on sounds right to me, start by getting a square setup of lighter wheels and non runflat performance tires. From there I would normally say springs/shocks or coilovers, then swaybars, then other stuff like control arms or an LSD. If you go the suspension route you have to decide if you want to keep your adaptive, which reduces your options (Dinan Shockware + springs, or some expensive coilover options from KW). I ended up getting rid of my adaptive (coded it out) and have been happy with that decision.
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      12-25-2016, 07:28 PM   #14
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thank you for your input, much appreciated! i am really looking forward to change that setup and get rid of about 30kgs weight. 18x8.5 OZ Ultraleggera 245/40 ET32 would be perfect, but not sure if available. so far i only found 8x18 and not 8.5x18.

recently i thought that driving in comfort mode on the Autobahn seems to give better traction compared to the sport mode which would be some kind of ridiculous. but i have to check it out further.
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      12-26-2016, 03:09 AM   #15
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Quote:
Originally Posted by ImI View Post
18x8.5 OZ Ultraleggera 245/40 ET32 would be perfect, but not sure if available. so far i only found 8x18 and not 8.5x18.
You dont need 8.5" wheel width for 245 tires.

Square 8x18" wheels with 245/40 tires will fit just fine!
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