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Discussion Starter #1
I'm in the process of ordering some custom rims for my M5 and wanted some community input.

Before everyone jumps and tells me to use the search feature, I have. I've spent more hours than I'd like to admit reading through countless old and not so old threads in order to figure out exactly what offsets and tire sizes I would need to run the rim sizing I want.
I am not interested in rolling the fenders, but I am ok with very slight rubbing on liners over heavy dips or at full steering lock, but I don't want to come close to rubbing the sidewall lettering off the tires or making holes through the plastic liners, or rubbing on the struts.

The rim/tire sizing I have settled on is as follows:

F 20x10 255/35/20
R 20x11 295/30/20


As for offsets I have compiled a few from past posts that were relevant to my interest and had full specs on their setup while mentioning how much they were rubbing, if at all.

Car 1
F 20x10 et 0 255/35/20 (rubbing)
R 20x11 et 16 285/30/20 (significant rubbing)

Car 2
F 20x10 et 3 255/35/20 (some rubbing)
R 20x11 et 22 295/30/20 (some rubbing)

Car 3
F 20×10 et 10 255/35/20 (no rubbing) (very close to strut, might actually touch)
R 20x11 et 28 295/30/20 (no rubbing)

Car 4
R 20x10.5 25 295/30/20 (rubbing)

Car 5
R 20x11 et 25 295/30/20 (rubbing)

All this being said, going back to my original choice on rim and tire sizing it seems that the optimal fitment with the lowest risk of rubbing is:

F 20x10 ET 5 255/35/20
R 20x11 ET 28 295/30/20


Would appreciate some input from those of you who have experimented with aggressive, flush fitments.

Regards,
 

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What I'm running and no rubbing whatsoever. Corner corner balanced on MCS 2WNR coilovers.

DINAN LTW
19x9 ET18, Yoko AD08R 275/35/19
19x10 ET25, Yoko AD08R 305/30/19

Macht Schnell 15mm spacers (front only)


941091

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Rear will be your problem - even a 9.5 wide ET17 wheel will rub in the back and there's no amount of trimming to make it work. If you're gettin custom sizes, why not get something that actually fits?

I've got weissach gold HRE P40s that ET27 and 10.5 in the back, clear the wheel well during the entire suspension travel.
941120
 

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Discussion Starter #4
I have a 9.5 ET16 at the back currently and I'm not rubbing.

My proposed 11 ET28 is only 5mm more aggressive than the 10.5 ET27 you are running.

Are you running a 295? I plan to as well, so my sidewall will be slightly more stretched than yours, gaining a little more clearance.

The gold HREs work well with Silverstone (y)

Rear will be your problem - even a 9.5 wide ET17 wheel will rub in the back and there's no amount of trimming to make it work. If you're gettin custom sizes, why not get something that actually fits?

I've got weissach gold HRE P40s that ET27 and 10.5 in the back, clear the wheel well during the entire suspension travel.
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Get ready for a long post! I'm in the process of rebuilding my 3 piece wheels for max aggressiveness lol I been at home like a mad scientist, here's some info, I hope you can understand what I'm trying to say. Please use a wheel and tire calculator online to visualize these sizes and offsets. Your vehicle contact points in the front are all related to outer sidewall corner, don't push it further than me!

Current setup
20x9.5 et0 255/35 (1meat)
20x11 et15 285/30 (square)

Every tire brand has a different sidewall, I like Michelin they're slim vs pirelli Toyo etc..
Tried this setup with H&R sport springs and with KW V3 they fit fine. In your description you said you were ok with slight rub on full dip, that's this. Everyone's going to have a different opinion on what's acceptable. If I hear my **** rub more than once in a day I have a problem, I don't, I actually like the rub it confirms I'm right where I need to be, I've slowly pushed my wheels out until I found the rubbing edge. What I have learned about fender liners is theyre bullshit and you can use a heat gun and push them with a hammer or something into a shape you like, even cut it. But don't worry, it's not necessary. The problem in our cars is not the fender liners, the problem is at the connection of fender and bumper front and back. You can't pull or move that without cutting. The fender's round curve is good they don't get in the way, rear is actually rolled from factory, you can do a pull but it won't pull out much anyway. At which point you see it's the connection at the bumper causing problems with the sidewall of the tire.

I installed my kwv3 with no springs and compressed the wheel and turned looking for rubs in the tight spots. Here's what I've found out.

The rear wheel tucks rim, even if you run stretch tires you can't go wider than the fender, it has to tuck in. On the inside of the wheel, it contacts the shock body first. I'm not sure how thick the original shocks are but with my V3 I can clear 12.5 from shock to fender.
When I say square tire setup it refers to sidewall stretch, each stage pulls sidewall in for more clearance, sidewall angle, pulls bead away from rim wall. About 1/4 inch each stage, Great if you want to run poke. 1 starts to show rim peeking out looking head on, 2 you legit see rim, 3 it starts to separate tire from rim for the stance boy look, 4+ is show car stuff. All of these make your sidewall stiff and uncomfortable. Grip is best at 1meat but some autocrosses like 1stretch for more predictable feel. I don't mind extra in front for better grip and comfort. Don't forget about the understeer! This is all personal preference, some are disgusted by stance cars. I don't think a M5 should have it's handling ruined with stretched wheels or airbag suspension. My opinion. I do like that stuff, just not here. Building wheels I did have a hard time picking between the two styles.

On to the front. Stock suspension cleared my new proposed wheel size but I noticed the KW V3 also cleared it, however, only if they are adjusted high. Since the coilovers are adjustable 3/4 of the adjuster available position gets blocked by tire, it needs about half an inch. Thus I can only run the wide wheels with the car adjusted "high", or use a half inch spacer to clear the spring and adjuster. Which would make the 20x 11 wheel poke past the fender, which would force me to run stretch, which I don't want for performance. The front fender doesn't need to tuck rim but the tire must tuck in where the fender and bumper meet up. Regarding fender liner, On full lock left and right things aren't as bad as half turn, you can imagine the tire arc, it extends furthest when halfway turned. It starts grazing the liner at the last half inch before bump stop, at which point it's just rubbing liner not hurting anything. Another rub is on the fender at dip for example when turning left the driver side inside of the fender towards the door like 1 or 2 o clock position rubs. But when do you have the steeringwheel turned one whole rotation and fully slammed suspension? It just doesn't happen in the real world. The inside wheel would never be slammed taking a turn like that.

So I'll say max front, from shock to poke fitment is 11.5 inches. Cancel the poke because you would have to run at least a stage 2 stretch (275/30 or 265/35) to clear the .5 inch of rim poking out (remember the fender/bumper connection) that leaves 11inches max, flush without poke, it fits on stock shocks. If you plan on getting KW V3 and slamming it low (which hurts your suspension geometry and roll center) you will need to cut another half inch off the inside bringing you to 10.5 inches. KW adjustment goes from 15-40mm drop. From eyeballing I should be 1/4 of the way from top setting me about 20+mm lower than stock ride height, like Dinan springs. I had H&R sport springs they lower it 30+mm and I broke my front bumper many times and ruined my under tray, ripped bumper backing out of parking spots, pulling into parking spots and contacting the curb. The possibilities for destruction are endless.
In the front I'm doing 20x11 with 285/30 which is square and sits flush. It clears, may need slight fender rolling turning fully slammed low on inside wheel, may not. When it's done I'll let you know again what problems I had and where. I also have Dinan fixed camber caster plates they add .7° camber and 1° caster. They reduce understeer and give maybe 1/4 inch more clearance on top of the wheel, not sure. Next will be installing dinan FRC (front sway bar) and rear sway. So hopefully this will ride awesome.
Lowered, Not slammed, camber plates, coilovers, wide rubber, adjustable sways, square front tire, stage 1 stretch rear tire

New setup
20x11 et -4 285/30/20 (square)
20x12.5 et21 305/30/20 (1 stretch)

Mods
Dinan fixed camber plates
Kw V3 coilovers

What kind of suspension do you have? What's your future plans? Wheels come after suspension but maybe this will help you. Lmk what needs clarification lol

I don't think you will be able to fit any more than a 285 in the front. In the rear it may be possible to get 315 on a 12 having 1/2 inch less lip than my 12.5 but in my opinion this car needs more front tire not rear tire.

Anyways parts are on order waiting for everything to arrive and assemble.


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This pic shows how low I can adjust the Front. Stock perch curves around the tire. This is 20x9.5 et15 255/35/20 I ran this with 15mm spacer because it was quite tucked in the outside, being a stage 1 meaty setup it would give a friendly fender liner rub on the top corner on hard hits. Now removing the 15mm spacer and going from 3.5" lips to 5" outer lip

New setup adds +17mm scrub compared to the factory setup. Steering shouldn't feel too weird, I have had +15mm additional scrub before via spacers. Felt fine. Again preference, more scrub more effort more feedback from bumps and tendency to change the cars direction when something hits outside of tire. So I've heard. None of those was noticeable I just thought my car looked cooler, I learned all this later in life.
Being low makes you think your handling better but you're not. You're getting to the bump stops faster at which point your maxed out, what they don't tell you selling springs is that roll center gets pushed much lower than where your center of gravity gets lowered. Making a big shift in body weight when making turns, bottoming out suspension faster on the outside wheel. So it may lower the center of gravity but ruin the genius suspension geometry used to keep things flat around corners.




Here's some good info about tire stretching.



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