18x9.5 +22 on FRONT and rear..

[nekky]

Hey guys.. Currently own an E92 335i but if the sale goes through this week, will be picking up an 07 M Coupé.

I really, really want to run white TE-37s on the car. 18x9.5 +22 is my ideal size, squared.. Yes, the Z4MC is a sports car, but I will not be tracking the car and want to run a somewhat "stanced" setup for day-to-day use. Please don't flame! I am a purist at heart, but there are no tracks nearby (central Canada).

Anyone at all have experience with running an 18x9.5 +22 up front? I know the rears will fit, but I don't want any scrubbing in the front and would like to keep fender modification to a minimum.

I know it's a longshot, but if anyone has a pic, that'd be excellent obviously.

I'm thinking a 225/40/18 MIGHT fit up front, but that's for you folks to educate me on. In the rear, I think a 265/35/18 would be correct, no? Again, *no tracking* the car, and a 265 will provide me enough grip for day to day douchebaggery.

Thanks in advance, errbahdy!


The car is Monaco Blue, btw

[The HACK]

Anytime you mess with the front wheel offset and width enough to throw off the scrub radius, you will adversely affect the steering feel and handling of the car.

Factory front wheel is 8.5" wide and 42mm offset. Plug it into a calculator before you commit to "squaring" your set-up with such a dramatic change in size and offset.

[ZStig]

I'm running 265/35/18s on 18x9 up front, -28 offset, -2.5* camber. No issues. Steering feels great. Understeer vastly improved over stock

[nekky]

Thanks, Roffle!

Newbie question, but are you running camber plates? How much camber do these run stock? ( no I have not searched thankyaaaaa )

[l4zy]

You will have to run camber plates or get a shim kit from turner motorsport to run enough camber. Stock specs is around -1 degrees. Sounds like your car is gonna look . Be sure to post up some pics!

[nekky]

Thanks l4zy!

Yeah.. I've been doing a bit of foraging around here and don't see any Monacoblau cars at all! Seen maybe one so far and it was a roadster to boot. Plus they only sent 1815 (or so) Z4Ms to NA total so figure it must be quite rare no matter which way you look at it..

I think white wheels on a dark car will set of nicely. Then just RPi exhaust and suspension of some sort and I'll be done pretty much. Car only has about 30k miles on it so it should be clean. Gonna go check it out more in depth tomorrow.

[ZStig]

Originally Posted by nekky

Thanks, Roffle!

Newbie question, but are you running camber plates? How much camber do these run stock? ( no I have not searched thankyaaaaa )

You need "camber bolts" to run more than -1.5* camber up front.
http://www.turnermotorsport.com/p-42...-bolt-kit.aspx

[The HACK]

Originally Posted by Roffle Waffle

I'm running 265/35/18s on 18x9 up front, -28 offset, -2.5* camber. No issues. Steering feels great. Understeer vastly improved over stock

Give this article a quick read...

http://www.hrsprings.com/technical/scrub_radius

And use this picture as a referece:



Ideally our type of MacPherson Strut design would perform best with a small to moderate amount of NEGATIVE scrub angle. By adding significant amount of offset and pushing the wheel away from the hub, the end result may be a net ZERO or even positive scrub angle which would result in poor steering response and poor tire contact patch upon cornering.

One of the ways to address this is to increase the steering angle inclination by adding camber on the king-pin side, which on the MZ4 is possible via the addition of camber bolts. However, if the camber is only adjustable via the top mount, adding camber isn't going to increase SAI and therefore additional offset can and most likely WILL result in poor handling characteristics.

If you're using camber bolts, you lucked out in that the addition of the bolt and the addition of offset "offset" (no pun intended) each other. However, if you had kept a smaller offset it can potentially increase the negative scrub radius and result in BETTER steering feel than what you currently feel, and potentially a much better handling car.

FOR EXAMPLE. I run both 245/45/18 on both my street tire (Falken RT-615K) and my R-Comp (Nitto NT-01) on two different tires, the street tire sits on 18"x8.5" replica with 38mm offset, while the r-comp rides on 18"x8" OEM wheel with 42mm offset. The two tires aren't actually THAT far apart, the RT-615K is technically an R-comp as well, but the way both tires behave is night and day. The OEM wheel retain factory scrub radius (actually increases from the factory negative scrub because I have camber bolts installed still) and the handling and steering response is phenomenal. The aftermarket rims, not so much. There's definitely less grip up front despite both being pretty good R-comps, and far less confidence inspiring despite a very minor change in offset.

Now, that's probably not the greatest example because, I still firmly believe the NT-01 is a better tire. However, data does speak for itself. While the tire sizes are identical, the end result is I always end up with higher pressure up front in the Falken RT-615K while the NT-01 would return with identical tire pressure front and rear after a heated session, indication there's more slip going on with the street set-up.

If y'all take nothing away from this post, I hope you take away this point. The way our front suspension works is voodoo magic. Every little change will affect the way it handles and not aways in a way you assume will work. Sometimes throwing a bunch of changes up front will yield positive results, sometimes it won't. I'm just saying, that keep in mind what offset changes alone will do to the suspension and how it works, and adjust OTHER parameters accordingly to maintain optimum performance. DON'T just blindly throw wider tires or wider wheels and insane offset because it looks cool, do some calculation with offset calculators, find out where your scrub radius is, and DO IT RIGHT.

[RADRACR]

Hack, so in general, what you're saying is we want camber bolts 90% of the time when we add offset up front? What about rear?

[The HACK]

Originally Posted by aestheticstorm

Hack, so in general, what you're saying is we want camber bolts 90% of the time when we add offset up front? What about rear?

The issue here is directly related to the wheels that steer a car, so unless it's a 4 wheel steering vehicle, steering angle inclination and scrub radius has little to do with the rear wheels.

In general, what I am saying is measure, test, and adjust. The issue with camber bolt is that it brings the top of the wheel/tire closer to the strut and you lose clearance, so there are cases where camber bolts aren't ideal, especially if you intend to run super wide tires up front.

So the real problem with tinkering with the front suspension is, it's all inter-related. If you add camber bolts, you may want to alter the offset to allow more clearance inside, but by doing so you may potentially increase the scrub radius enough to impact steering and grip up front.

Ultimately, the added grip with wider tires up front may trump the smaller effect of poor scrub radius and allow you to go faster. That's why I always say, suspension tuning is a series of finding compromises. My current compromise seems to be 245/40/18 tires up front with -2.5 degrees of negative camber, slight (1/16 total) toe-out, with 2 washers on the camber bolt and ~stock-ish ride height, and factory off-set. This seems to work very well for me after about 20 days worth of tinkering on the track.

[johanness]

Originally Posted by l4zy

You will have to run camber plates or get a shim kit from turner motorsport to run enough camber. Stock specs is around -1 degrees. Sounds like your car is gonna look . Be sure to post up some pics!

I got -1.5* with the pins pulled (stock) and -2.0* with my H&R springs.

OP, I'm hoping that'll be enough to fit my 18X9.5et35 fronts I've just ordered. If not, then I'll buy the shim kit and dial in another half a degree. I was told this should fit without any rubbing issues (245/40/18)

[SmartBastard]

Originally Posted by The HACK

Anytime you mess with the front wheel offset and width enough to throw off the scrub radius, you will adversely affect the steering feel and handling of the car.

Factory front wheel is 8.5" wide and 42mm offset. Plug it into a calculator before you commit to "squaring" your set-up with such a dramatic change in size and offset.

If I'm not mistaken the factory front is 8" and 42mm offset.

I'm picking up ARC-8 9" with 42mm offset, which means it should go both out and in 13mm. Is that the right way to go to not screw my handling?

[Beedub]

i honestly don't get this trend for ever wider rims/tyres..... the car can behave beautifully on a proper setup well within the arch space contraints and look perfect too, fitting these hugely wide front and rear tyres is completley pointless imo...... i expect to be flamed for this but i dont see the point..... running a setup just for the stance that will ruin the performance/handling aspect of things is about as far away from ///M as it could be!!! I think a Golf with 22" wheels may be more suited to you, drop it on it stomach, camber the fuck out of it and revel in the shit ride but great looks!!!

now wheres the hiding behind the couch smiley??

[bucko521]

Originally Posted by Beedub

I think a Golf with 22" wheels may be more suited to you, drop it on it stomach, camber the fuck out of it and revel in the shit ride but great looks!!!

now wheres the hiding behind the couch smiley??

LOL....I have to agree somewhat..I like an aggressive look on a car, nice wheel stance, and a slight edge to a wheel setup. But if you want to make a 'ricer', then go buy one of those as well, and "go to town"



BTW... ..here it is ===>

[Beedub]

Originally Posted by bucko521

LOL....I have to agree somewhat..I like an aggressive look on a car, nice wheel stance, and a slight edge to a wheel setup. But if you want to make a 'ricer', then go buy one of those as well, and "go to town"



BTW... ..here it is ===>

arhh ther it is... thanks...

[johanness]

Originally Posted by Beedub

i honestly don't get this trend for ever wider rims/tyres

It's not for you TO get.

Originally Posted by bucko521

But if you want to make a 'ricer', then go buy one of those as well, and "go to town"

Yah, TOTALLY rice:


(thx colakitty for pic)

[bucko521]

Originally Posted by johanness

It's not for you TO get.



Yah, TOTALLY rice:



gfy

Wow....

Wasn't implying anything other than if you want a "too fast too furious" type of car...then go build one. The pic I posted works for some people...I prefer the clean look....that is all. BTW...nice car.

Sheesh.... makes you wonder why people think BMW owners are ......s!!

Have a nice day!

[Beedub]

Originally Posted by johanness

It's not for you TO get.



Yah, TOTALLY rice:


(thx colakitty for pic)

This is the internet, a public forum, i am just expressing my views.....

lol.......... johanness....... being loud, outspoken and foul mouthed..... ill just answer with F@#k off.......

the silver TI is lovely.....

[Finnegan]

Okay, here's what I'm taking away from this, some of which seems obvious, some not. Sometimes putting things in writing helps me think through it! I trust The Hack will tell me where I've messed up. And Hack, thank you for taking time to explain these concepts and to lay out the issues. I again realize how little I know and how much there is to understand.

• Staying with stock offsets for the front wheels in particular is highly desirable given changes to scrub radius that will result with different offsets. Even small changes (Hack's example of 4mm difference can measurably change handling changes).

• There's a reason the BMW engineers selected the stock offsets: it results in the correct math for good and safe handling.

• Moving from negative to zero or positive scrub radius with a McStrut is profoundly affects the car's handling--potentially introducing unpredictable and dangerous handling characteristics. This isn't about "looks"--which are subjective anyway--dramatically changing the offset can become a safety issue.

• Changing to lower offset than stock can be neutralized to some small degree by other changes to the suspension (steering angle inclination "SAI") by using camber washers not via camber plates. (Washers affect the kingpin side of camber, unlike camber plates, which do not.)

• How much change in offset can be neutralized? Given The Hack's 4mm difference example, where he's running -2.5 with camber washers, vs. -1.0 stock negative camber, I'd say it's there's not much room to change offset and retain a close to stock scrub radius.

• A wider wheel with the same offset as stock will not change the scrub radius (assuming the tire's sidewall height stays very close to stock as well). This limits how wide you can go and retain clearance. With stock offsets, camber plates are a viable option to increase negative camber and clearance from the strut, since there's no need to dial the scrub radius back into spec.

• Asking what others are running needs to take into account other suspension modifications they have (lowering, camber bolts, camber plates, caster, wheel height, tire sidewall height, tire type since sidewall flex can affect scrub radius as well).

Bottom Line: There's a hell of a lot going on with a lot of variables involved. If you're going to mess with this, do the math!

[johanness]

Originally Posted by Beedub

i expect to be flamed for this

Don't cry about a response when u get one if you're expecting it

Originally Posted by Beedub

the silver TI is lovely.....

But

Originally Posted by Beedub

fitting these hugely wide front and rear tyres is completley pointless - running a setup just for the stance that will ruin the performance/handling aspect of things is about as far away from ///M as it could be!!!

245/275 tire-combos aren't pushing the envelope and don't do anything u mentioned

[Beedub]

Originally Posted by johanness

Don't cry about a response when u get one if you're expecting it

But

245/275 tire-combos aren't pushing the envelope and don't do anything u mentioned

Lol who's crying?? Lol.....

245 on a 9.5" rim??? far from ideal...

Anyhow your boring me now..... Back to the thread.

[beta]

245/275 is definitely not pushing it

- Keeps the diameter very close to stock 1.77% for the back, 1% for the front.

- Maintains the staggered setup. The rear tires are still 30mm wider than the front, however the front tires are bigger proportionally. For a rear tire of 275 width, the front tire proportional to 225/255 would be 242.6. So by making it slightly wider at 245 you dial out some understeer.

- fits without rubbing, even on coilovers (at max height, not sure if it would rub if you lowered it).

Finnegan, adding to what you posted, if you lower the car at all you get a ton of camber for free. At max height on kw v3s I'm at -2.5+ camber up front without any other modifications.