Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

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iamcreepingdeath
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Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by iamcreepingdeath »

I did a lot of searching, and there seems to be very little information on the fitment of 16x8 ET0 wheels on the E28, even though I know it has been done, as I have seen a few fleeting examples on the internet.

Here are the only examples I have been able to find:

viewtopic.php?t=115116

viewtopic.php?t=128850

So I have a set of 16x8 ET0 and ET16 Trans Am GTA wheels that I am about to put tires on, and I am a bit worried about the rear fitment with the ET0 wheels and 225/50 tires. Anyone have experience with this specific fitment? I have also already rolled the fenders, and it is sitting on coilovers.

Thanks
BMWCCA2
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by BMWCCA2 »

Not judging but just wondering why you'd want to even attempt to put zero-offset wheels on a stock E28?

In one of your links, Moosehead even questions if the bolt circle is the same as an E28.

With all the nice E39 7.5 x 16" wheels available out there, it looks like this a bit too much to take on for benefits I fail to see. :dunno:
iamcreepingdeath
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by iamcreepingdeath »

The benefits are simple: The wheels look awesome. Best looking wheel I have ever seen.

Regarding the bolt pattern and center bore, those have been taken care of (A friend has a CNC mill).

Also, why are you wondering why I would attempt to put zero offset wheels on an E28?

Here are some pics:

Image

Unsure as to why this pic is sideways, but you get the idea:
Image
iamcreepingdeath
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by iamcreepingdeath »

BMWCCA2 wrote: Feb 18, 2021 11:25 AM With all the nice E39 7.5 x 16" wheels available out there, it looks like this a bit too much to take on for benefits I fail to see. :dunno:
Also a side note, E39 wheels require ridiculously thin hubcentric rings, which are a PITA
Mike W.
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by Mike W. »

16X7.5 with 20 offset and 225/50 rubs under extreme conditions with stock springs. With your proposed setup you would be moving the edge of the ~15 MM further out. That's ~5/8 of an inch, which is a lot of fender rolling. And the point where they tend to rub is not at the top where rolling is easier, but in back where there's more metal there. Can it be done? Well, give me a torch and a sawzall and... :cool: But easily? I dunno, I kind of doubt it. And if you have lowering spings you would need to roll them even more.
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by Shawn D. »

Mike W. wrote: Feb 18, 2021 1:52 PM With your proposed setup you would be moving the edge of the ~15 MM further out.
Make that 20mm.
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by Shawn D. »

These wheels will not only put the tire 3/4" further outboard, that means the scrub radius is being changed for the front suspension. This can have negative effects on driving dynamics, including an increased tendency to pull on uneven surfaces or during braking.
iamcreepingdeath wrote: Feb 18, 2021 12:00 PM The benefits are simple: The wheels look awesome. Best looking wheel I have ever seen.

Regarding the bolt pattern and center bore, those have been taken care of (A friend has a CNC mill).

Also, why are you wondering why I would attempt to put zero offset wheels on an E28?

Here are some pics:

Image

Unsure as to why this pic is sideways, but you get the idea:
Image
Looks as if he only took care of the bore, not the bolt pattern. 0.65mm off in diameter isn't much, but 0.32mm over a ~10mm distance (the bottom of the lug to the hub) is a 2° angle.
Mike W.
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by Mike W. »

Shawn D. wrote: Feb 19, 2021 5:07 PM
Mike W. wrote: Feb 18, 2021 1:52 PM With your proposed setup you would be moving the edge of the ~15 MM further out.
Make that 20mm.
Nope, 15. 10MM for the change from 20 to 10 offset, then since tire section width changes .4" or 10MM for every half inch of wheel width change, another 5MM totaling 15MM.

Edit. Somehow I misread ET0 as ET 10. So it would be 25MM further out, or a full inch.
Last edited by Mike W. on Feb 23, 2021 9:27 PM, edited 1 time in total.
iamcreepingdeath
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by iamcreepingdeath »

Shawn D. wrote: Feb 19, 2021 5:12 PM These wheels will not only put the tire 3/4" further outboard, that means the scrub radius is being changed for the front suspension. This can have negative effects on driving dynamics, including an increased tendency to pull on uneven surfaces or during braking.

Looks as if he only took care of the bore, not the bolt pattern. 0.65mm off in diameter isn't much, but 0.32mm over a ~10mm distance (the bottom of the lug to the hub) is a 2° angle.
Front wheels have ET16 offset, so not an issue for the front. This is only an issue in the rear, as the rear wheels have a ET0 offset.

I also took care of the bolt pattern. I bored down the countersinks of the lug seats to match a 120mm bolt circle.
iamcreepingdeath
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by iamcreepingdeath »

Update:

Mounted tires on the wheels and slapped em on the car. As you can see, the wheels rub the fenders. I have rolled the fenders already to the max I am comfortable with.

So next step: I am going to shorten the rear wheelbase, and I have an idea as to how to do it, so stay tuned! Also, I should start a build thread...

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Here are some closeups of rear wheel arch:

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Here is a comparison of E38 style 5 (16x8, ET23, with 10mm spacers), compared to the trans am wheel (16x8 ET0, no spacer):

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stuartinmn
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by stuartinmn »

Clearance issues notwithstanding, but they are good looking wheels.
iamcreepingdeath
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by iamcreepingdeath »

stuartinmn wrote: Feb 23, 2021 4:54 PM Clearance issues notwithstanding, but they are good looking wheels.
That's why I'm working hard to make 'em fit!
tn535i
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by tn535i »

How will you narrow the track? Relocate the trialing arm mounting points? or modify the trailing arm itself, subtract from inside and add to outside? I could see this working but make sure you don't create an issue with the drive axle.

fwiw you can widen the rear track on an e30 by switching from std hubs to ix hubs in the rear. My son did that so that the project e30 looks staggered even though it has the same wheel and tire all around. I don't think there is any parts swap like that out there for an e28 to do the opposite.
iamcreepingdeath
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by iamcreepingdeath »

tn535i wrote: Mar 03, 2021 4:47 PM How will you narrow the track? Relocate the trialing arm mounting points? or modify the trailing arm itself, subtract from inside and add to outside? I could see this working but make sure you don't create an issue with the drive axle.

fwiw you can widen the rear track on an e30 by switching from std hubs to ix hubs in the rear. My son did that so that the project e30 looks staggered even though it has the same wheel and tire all around. I don't think there is any parts swap like that out there for an e28 to do the opposite.
This is all very experimental, but I am pretty sure it's gonna work beautifully.

So I moved each trailing arm inboard by 10mm. As you can see, the inner sleeves of the stock bushings protrude out of the inboard side by 10mm.

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So I shaved 'em off.

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I drilled out some nuts I had laying around that were 10mm thick, and used them as spacers. Here is a test fit on a spare subframe I have lying around.

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So I slapped a trailing arm back in the car (didn't install CV axle or hook up coilover) so I could test wheel fitment. The wheel fits perfectly now.

Here are some before/after pics from the test fit.

before:
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After:
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Before:
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After:
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Before:
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After:
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I also articulated the trailing arm to see where the tire begins to rub. It went up quite a ways before it even began to rub, much farther than it should in normal driving situations.

Here it is where the tire just begins to contact the inside of the wheel well.
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I then installed the CV to see if it would bind, as the trailing arm had moved in 10mm. At the shortest point, the CV axle baaaarely reach full compression, which I didn't like. So to remedy that, I machined a few mm off of a few surfaces, to give the CV axles a few more mm of margin. I don't have post-machined pics unfortunately (not sure why I forgot to take them) but here are the surfaces I machined.

I took 3mm off of this surface (the diff output flange), and I also removed the grease cap from one side of the CV, and filled this output flange with grease, so it essentially "became" the new grease cap itself, thus removing a further 1mm of the thickness of the original grease cap.
Image
iamcreepingdeath
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by iamcreepingdeath »

I also took 3mm or so off of this surface from the hub flange. This allows the hub flange to sit closer to the hub.

Image

Over all, this gives "back" about 6-7mm of the 10mm that the CV axle "lost" so to speak when I moved the trailing arm in.

What this means is that the stock pitman arm "dogbone" thing no longer will work, of course. What this did was provide additional lateral control to the trailing arms, so lateral load isn't being entirely being directed through the trailing arm mounting ears (like it is in E30s). So, I will be making my own lateral load arms, and they will be much longer than the stock ones. The stock ones, as the trailing arm articulates, forces the trailing arms side-to-side, which to me is no benefit for anything. The longer lateral arms will do the same job of taking all lateral loading, but won't yank the trailing arms back and forth as the suspension articulates.

It will be set up something like this (after my parts arrive):
Image
Mike W.
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by Mike W. »

Well, I question your engineering but I give you full points for both creativity and determination. You don't just like those wheels, you must really, really, really like them to go thru all this.
iamcreepingdeath
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by iamcreepingdeath »

Mike W. wrote: Mar 04, 2021 2:12 PM Well, I question your engineering but I give you full points for both creativity and determination. You don't just like those wheels, you must really, really, really like them to go thru all this.
What exactly are you questioning? Please do challenge me.
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by Mike W. »

Well, the rubber bushings in the trailing arm allow it to move around some, I think it's going to shift, rub and perhaps bind some at times against the subframe brackets that it's attached to. And while it might work ok, a nut, without full contact is a poor substitute for a regular spacer, it might wear into the bushing hub. Also I don't think you quite follow what the dogbones are supposed to do, "The stock ones, as the trailing arm articulates, forces the trailing arms side-to-side, which to me is no benefit for anything." Which is what they're supposed to do, they control toe to control oversteer. That said they weren't used on '82s, nor I don't think on some lower end euro models suggesting they're not essential, but many have reported the rear end feeling much better with new ones.

Machining things down to give clearance to the half shafts I don't really have a problem with although I wouldn't exactly describe it as best practices. BMW often overengineered things so I think you'll be ok there as long as you aren't going to a high output turbo build. I would have used RTV to seal the CVs to the flanges, but that's trivial and insignificant.

Now, I'm not predicting anything catastrophic will happen, but I suspect it might not handle as well and you might get grinding noises. Do keep an eye on those trailing arm mounts though, just in case.
iamcreepingdeath
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by iamcreepingdeath »

Mike W. wrote: Mar 04, 2021 5:33 PM Well, the rubber bushings in the trailing arm allow it to move around some, I think it's going to shift, rub and perhaps bind some at times against the subframe brackets that it's attached to. And while it might work ok, a nut, without full contact is a poor substitute for a regular spacer, it might wear into the bushing hub. Also I don't think you quite follow what the dogbones are supposed to do, "The stock ones, as the trailing arm articulates, forces the trailing arms side-to-side, which to me is no benefit for anything." Which is what they're supposed to do, they control toe to control oversteer. That said they weren't used on '82s, nor I don't think on some lower end euro models suggesting they're not essential, but many have reported the rear end feeling much better with new ones.

Machining things down to give clearance to the half shafts I don't really have a problem with although I wouldn't exactly describe it as best practices. BMW often overengineered things so I think you'll be ok there as long as you aren't going to a high output turbo build. I would have used RTV to seal the CVs to the flanges, but that's trivial and insignificant.

Now, I'm not predicting anything catastrophic will happen, but I suspect it might not handle as well and you might get grinding noises. Do keep an eye on those trailing arm mounts though, just in case.

True, the shaved down parts of the trailing arms will rub against the mounting tabs. For now, i'll keep that section greased the best I can. I also did grind down the OD of the TA bushings to allow the cut part of the inner sleeve to stick out a little. It may help some. Also, the lateral arms I am adding will be adjustable, so I can apply some preload on the trailing arms pulling them outboard slightly, which should minimize contact on the flanges. I'll keep an eye on it and see how it fares.

Also, how do the stock dogbones control toe? toe and camber only change with trailing arm articulation, as the TAs pivot on fixed axes. This is the whole reason aftermarket companies sell eccentric bolt kits to add toe and camber alignability. The only movement the TAs can make off-axis is entirely within the flex of the factory rubber bushings.

Regarding the "spacer" nut, what else is it supposed to contact besides the inner sleeve of the factory bushing? I guess I am not picturing what you mean by the "bushing hub". Is that the "inner sleeve" I am referring to?

Regarding machining flanges, I agree, I would have rather not. My longer term solution is to find out if some other BMW CV axle shafts (just the shafts themselves) from maybe an E30, E21, E12, etc will work with the E28 CV joints to create a shorter overall CV axle. If that fails, aftermarket splined shafts can be had at any length needed to create any length E28 CV axle. Also, I did do RTV sealer, as well as extra grease.

I ought to create a build thread for my E28 at some point.

Pic of the CV axles RTV'd and bolted to diff output flanges.
Image
tn535i
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by tn535i »

I don't see anything really wrong with what you've done. You've already lowered the car 'too far' to hope to have ideal suspension geometry ;) so why not :laugh:. You see the purists would scoff at the wrong offset, wrong camber, wrong ride height, wrong looking wheel from a Pontiac :shock: but this is your thing not mine.

So back to some engineering points... The trailing arm pivot must be tightened in place with the car at ride height so as NOT to twist the bushing and prematurely wear it. The nut while not ideal should keep it from rotating once tight, a spacer of the same inside diameter and equal or greater outside diameter would be better. Actually an OD as big as the entire bushing would be ideal I think. I assume you used a lathe to turn the axle parts. Why not make a better spacer? If you made these you could even incorporate a thrust washer to put on either side of the bushing to take up that sideways movement and prevent contact with the mounting tabs, maybe Delrin? On the axle parts I hope you dialed the face in flat before turning in order to keep everything on the proper plane. It might set up some weird vibrations in the CV's if you did not. I don't see why the ball end link cannot perform the same function as the dogbones but a thrust bearing/washer/thing might be easier.

Nice time to change the subframe mounts while all this is apart. Those look like OE style not one of the stiffer designs. You might want them stiffer with so little movement before rubbing.

I notice one of the Poncho wheels under the sill while it's on jack stands. Good practice as a safety net but I would use something I didn't want damaged if it really did fall. fwiw I think the wheels look like several others that are variations on some of the older BBS designs. All pretty classic IMO.

Keep us posted !
iamcreepingdeath
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by iamcreepingdeath »

tn535i wrote: Mar 04, 2021 7:17 PM I don't see anything really wrong with what you've done. You've already lowered the car 'too far' to hope to have ideal suspension geometry ;) so why not :laugh:. You see purists would scoff at the wrong offset, wrong camber, wrong ride height, wrong looking wheel from a Pontiac :shock: but this is your thing not mine.

So back to some engineering points... The trailing arm pivot must be tightened in place with the car at ride height so as NOT to twist the bushing and prematurely wear it. The nut while not ideal should keep it from rotating once tight, a spacer of the same inside diameter and equal or greater outside diameter would be better. Actually an OD as big as the entire bushing would be ideal I think. I assume you used a lathe to turn the axle parts. Why not make a better spacer? If you made these you could even incorporate a thrust washer to put on either side of the bushing to take up that sideways movement and prevent contact with the mounting tabs, maybe Delrin? On the axle parts I hope you dialed the face in flat before turning in order to keep everything on the proper plane. It might set up some weird vibrations in the CV's if you did not. I don't see why the ball end link cannot perform the same function as the dogbones but a thrust bearing/washer/thing might be easier.

Nice time to change the subframe mounts while all this is apart. Those look like OE style not one of the stiffer designs. You might want them stiffer with so little movement before rubbing.
Yep! I have Powerflex race poly subframe bushings on their way to my house!

The faces of the diff flanges are dialed in flat, I checked w/ a dial indicator. I most definitely plan to make my own spacers and thrust washers when I get a chance (I don't own a lathe, I have to use a buddy's shop when available).

If I wanted ideal suspension geometry, I'd buy a Corvette, and I wouldn't even glance at a car with trailing arms (which are a terrible idea), but unfortunately, I love E28s!! :D
iamcreepingdeath
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by iamcreepingdeath »

tn535i wrote: Mar 04, 2021 7:17 PM I notice one of the Poncho wheels under the sill while it's on jack stands. Good practice as a safety net but I would use something I didn't want damaged if it really did fall. fwiw I think the wheels look like several others that are variations on some of the older BBS designs. All pretty classic IMO.

Keep us posted !
Ha! Safety, he says...

That wheel is down there because I kicked it out of the way as I walked by!
Mike W.
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by Mike W. »

iamcreepingdeath wrote: Mar 04, 2021 5:48 PM
True, the shaved down parts of the trailing arms will rub against the mounting tabs. For now, i'll keep that section greased the best I can. I also did grind down the OD of the TA bushings to allow the cut part of the inner sleeve to stick out a little. It may help some. Also, the lateral arms I am adding will be adjustable, so I can apply some preload on the trailing arms pulling them outboard slightly, which should minimize contact on the flanges. I'll keep an eye on it and see how it fares.
Good. That would be my biggest safety concern. You might want to consider beveling the outer edge of the trailing arm ear so it's not a sharp edge on the mounting flange.
Also, how do the stock dogbones control toe? toe and camber only change with trailing arm articulation, as the TAs pivot on fixed axes. This is the whole reason aftermarket companies sell eccentric bolt kits to add toe and camber alignability. The only movement the TAs can make off-axis is entirely within the flex of the factory rubber bushings.
It has to do with the flexing of components, especially the TA bushings which is only semi fixed due to the rubber, but also compensates for how the semi trailing arm changes toe as it pivots thru it's range of motion. I'd have to have it in front of me to see it well enough to explain it. Significant, but not necessarily a deal killer.
Regarding the "spacer" nut, what else is it supposed to contact besides the inner sleeve of the factory bushing? I guess I am not picturing what you mean by the "bushing hub". Is that the "inner sleeve" I am referring to?
Yes. While I've certainly used nuts as spacers before, in that location I see the potential for wear and then play.

I'm more a skeptic than a purist. It is an interesting experiment that I wish you luck on, no sarcasm, I mean it. I think it will handle worse, but depending on how much and how hard you (do or don't) push it, it may be a non issue. But do please keep an eye on the TA mounting ears, that would make me nervous.
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Re: Specific wheel/tire fitment: 16x8 ET0 w 225/50/16

Post by tn535i »

I'm also a skeptic bordering on cynic and I wasn't referring to you(Mike) specifically as a purist just in case you thought that. I will be optimistic here and say with a little attention to some details this will turn out OK. It will deviate from what BMW intended but not so bad that it will be unsafe like some junk I've seen done. It's not what I would do but that's not the point.
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