Going Wider Rims & Tires... Ideal Size for Handling & Looks?
 

Hi Everyone!

I have a 2018 BMW X2 (front wheel biased X drive aka it is only AWD at standstill and when it detects slippage)--yes, not exactly the right place to post this, but the X2 forum is literally dead. So I thought I'll have a better response here!

Anyways, I'm planning on getting aftermarket wheels to widen the stance as well as improve handling. I've started doing some research on whether wider stance (or tires) would provide better handling. And to be honest, there are proponents of both sides. Since this is going to be a street car (with spirited driving) and not a track car, I thought even if I'm wrong and wider stance doesn't improve handling, the effects should be minimal.

The stock wheels that came with my X2 is a squared setup: front and Rear: 19x8.5 +35 || 225/45/19

I'm looking to get a wider stance look for the rears and have decided on either a 19x10 or 19x10.5 on 295/35/19 tires. This should put me at less than 1% difference compared to my stock setup.

My question is, should I be going for a squared setup with this? I've never seen anyone do a squared setup with a 295 wide tire in the front.

What would be the pros and cons of this setup in terms of handling?

If I were to go with staggered setup, what width should I go in the front? I'm thinking 255/40/19.

Of course, I don't want to sacrifice handling for looks at all. My primary focus is to improve handling (or at least not make it worse than stock). Any input / advice is appreciated! https://f30.bimmerpost.com/forums/im.../happyanim.gif

What's an X2?

Laff..... Can't give you any specific sizing advice that works for your X2 but you did say "AWD", yes? I'm pretty sure it's still a big deal (but maybe not as it's been five years since I was actually in the tire biz) that you should not mix tire sizes on AWD vehicles due to the high possibility of accelerated drivetrain wear. In addition, staggered sizing on AWD (as on Z cars with VDC - vehicle dynamic control, but with more far reaching circumstances) can "trick" the car's computer into thinking one or more wheels are spinning and therefore apply the AWD and/or slippage controls (traction control or other). So, unless the vehicle is equipped with a staggered setup as factory, don't deviate unless the manufacturer specifies an optional stagger fit. Pretty sure this caution is in your service and/or owner's manual.

This is the same rationale that stipulates that when one or two tires are worn more than the others, ALL FOUR need to be replaced to maintain equal diameter, hence, circumfrence. That's how tight the tolerances can be on AWD.

Thanks, I did not know that... Good info. I went to Tirerack and only see squared setup in 18", 19", and 20", so I'm assuming I can only go with squared...

If that's the case, what's the widest tire I can go for this car without sacrificing handling and acceleration too much? What would I need to determine that?

Was really hoping I can fit a 295 in the rear but given it's AWD, there's no way I can do 295 all around

OK, before going and splurging on a set of gumballs, take a step back and see what you're working with first. Does you car have the standard or Sport suspension? You mention 19" wheels and it appears that's what comes as part of the Sport suspension but.... it may be just the 19" wheel option without active suspension.

In any event, what I'm getting at is that you should take a look at what specific sizes the Sport setup has. Wheels wider? Tire size different? If yes, this might be your answer.... mimic the factory sport suspension specs. If you already have the Sport package, I'd ask the BMW dealer.... or more specifically, the Parts Dept.... "What OE accessory wheels are OK and available for my X2 with Sport package (or with whatever you have)?" Finding specs on those can also help you determine alternative sizes if such sizes are offered by BMW, maybe an M-spec or somesuch which may be larger.

Now here's the caution I have for you.... whatever you opt for, whether it's a mild upgrade to, say, a 255 square setup or somehow get all the way up to that 295 size, you WILL pay a weight penalty. This may negatively affect your performance, and any gain from the sticky rubber will be lost in steering response and overall suspension feel. UNLESS... you're able to shed weight off the wheels to compensate for the increased tire size and weight. Read: forged, lightweight wheels.

Also, if upgrading to such wheels/tires, you now know you have to do all four and do the math to get the tire closest to the OE diameter to avoid the usual issues with too tall or too short tires.

All in all, I'm *GUESSING* (since I really don't know what works on your car) that there's a good compromise setup that will help you garner more performance (and looks) without the downsides I mention. Would surmise that means something maybe an inch to inch+half wider and tires maybe 30mm wider max (to go with the inch wider wheels) and an aspect ratio lower (say, from 45 to 40 as example) to keep height OK.

Good luck! Sorry couldn't offer specific figures but hey, we're tawkin' foreign cars here. Hahahahaha.

Learned quite a bit from your posts--did not know about staggered setup potentially damaging differentials until you mentioned it.

So if I were to go with staggered setup, it can be done as long as the OD of the tires are within 1% delta? So I should look at 1.) overall circumference and 2.) revs/mile of the two tire sizes?

I have stock suspension (non active), and this car gives 19" and 20" wheel options, but both utilize 225mm wide tires.

Let's say I go with a staggered setup with 255mm wide tires, this wouldn't cause any issues with my diff. But what added benefits would a wider tire have vs. narrower one, everything else being equal (unsprung weight)?

When deviating from the manufacturer’s specifications for tire size and wheel offset, your best advice comes from owners who have tried the variations.As Mic mentions, you need to keep with an all-square setup with AWD. Mic is also correct when he states you must replace tires as a full-set of 4 (or at least match 4 tires with identical wear). I have a Jeep Commander (which has all time 4WD) and have learned this lesson. This is another reason you want to keep and all-square setup: You can rotate identical tires which is something you cannot do with a staggered setup.I doubt you will be able to go much wider than 245. Going with a wider tire may result in fender interference (rubbing) and restricted turning or even interference at the front. If the AWD BMW is front wheel drive biased, you may need to use FWD offset vs. greater offset of RWD.I use a tire shop that is knowledgeable about wheel offset and tire size. They also have “test setups” that allow you to see the appearance and evaluate problems before you buy.

Hey Spike, I thought it's ok to go with staggered setup on AWD as long as the overall circumference between front and rear is the same? I thought the issue with diffs and even trannys being damaged is from the front and rear having different revolutions per mile, which causes the diff to think the car is slipping? If front and rear have almost the same revolutions per mile (I think I heard within 1%), it would be fine?

Thanks for replying by the way!

I’m guessing, but I believe the typical AWD system sends power to the wheel(s) that have traction when it detects a slipping wheel. The torque is similar to all the wheels. My Jeep with QuadraTrak requires 4 identical tires.This is quite different in a Porsche 911 Carrera 4 that runs with 245/35-20” (overall diameter is 26.8) and 305/30-20” (overall diameter is 27.2). Not only are the tires much wider in the rear, but the overall diameter varies front to rear. The AWD 911 Carrera 4 is predominantly RWD (80% of the torque going to the rear wheels) and has an elaborate and expensive system that divides the torque front to rear and side to side while taking the different tire sizes into account.

I am not sure what type of system is in your BMW. If the car came with identical tires (BMW specs?), that is probably what you need. I suppose you could go wider (if that fits inside the fenders without rubbing).

Thanks Spike. I did find that certain trims come with staggered AWD. I checked the circumference different and it was like 0.4%.

Also, in terms of whether my new setup 19x10 ET35 285/35/19 rear will fit the X2, would this be the correct way of measuring?

I took a ruler and taped it on my rear fender hanging straight down to the center caps. Then I took another ruler and measured the gap between the outer rim of the wheel, and it was 19mm.

Attachment 455462

The wheel fitment tool below shows current vs. new wheel dimensions and its difference. If I were to mount 19x10 ET10 285/35/19 on my rear, it will poke out 44.1mm more than before. Since I found that the gap between the outer rim of my wheel and the fender was only 19mm, I could potentially have rubbing issues (or just aesthetically displeasing to have wheels sticking out of fender).

Attachment 455463

Now my question is... To fix this and make the rear sit flush, I pretty much increase the offset to +35 instead of +10 right? If so, that would make the new wheel be 19.1mm closer to the strut. Next, I'd measure the gap between my current 225mm wide setup to the suspension strut to make sure it has more than 19.1mm clearance?

If this checks out, does that mean the 19x10 ET 35 285/35/19 will fit my rear without rubbing issues?

Thanks :happyanim: