Opinion 88M6 - New Michelin TRX 240/45VR415 or Wheel Swap to standard 16/17s &Tires?

[maxg765]

Hello Forum Friends,

Your opinion is appreciated. Time for some new tires. While there is plenty of tread on my current stock TRX tires, they are somewhere between 16 to 18 years old, plus two tires have nails, still hold air but requiring repair.

As we know TRX is that non standard bastard wheel size of 16.3 inch using specific TRX tires that was used back in the 80s by some marques such as BMW and Ferrari. Can you say Sony Betamax.

I have two options:
A
Buy a new set of Michelin TRX GT 240/45VR/415 (These cost $474 a tire) keeping my original 1988 M6 wheels thus remaining completely stock
B
Source a set of wheels either BBS RS 001, RC 090 or Alpina in 16 or 17 inch (still torn on which size but do not want this thread to become a debate over BBS vs Alpina or 16 vs 17 inch).

Info on the car to aide in your mindful opinions
1988
M6 E24
Color is Salmon Silver on Black interior
Aprox 68000 miles (109500 Kilometers)
Completely stock

At first glance Option A, the TRX tires appear to be the expensive option at $1896.00 plus shipping fees for four tires. I am not sure if the spare is also a TRX, if so then I would also replace it bringing the price to $2370 for five tires plus freight.

Option B would require sourcing a set of wheels and tires. I do not know which tire size or brand to use since I do not have the wheels yet and have not gone down this rabbit hole but sure there is plenty of info to be found. There is the other issue with option B in that I do not have any leads on a set of refinished or needing refinishing Alpina or BBS wheels. My guess is 16 or 17 inch tires will run $1500 to $1800 for a set of five with the spare. Then there is the need to source one of those three wheel options.

Your thoughts please

Thank you in advance

Max

[jbd5015]

The TRX option is a bummer as the tire tech is OLD, even if the rubber is new. Unless you are entering the car into concours events I think the TRX is obsolete.

If you are more concerned about performance and safety vs originality, Id say the 16/17" wheel replacement would be the wiser choice. You can get a modern tire that provides better grip and safety than the TRX design.

No doubt both options are expensive, but when you need to replace the tires on the 16/17" option, itll be way less exspensive.

17's are the popular size on these cars to give it a more modern look, but the 16's will ride more like the stock set-up. 225/45R17 is a definite fit. I think Bob put a chunky 235/50R17 without much issue, but I cant quite remember. Ive got nothing for you on the 16's.

Play around on a tire size calculator to get an idea of size options, or check mye28.com for wheel fitment info.

Good luck!

[wfwright2]

You will need to check, but the spare will probably be a TRX of the smaller diameter, although my M6 (three owners before me) had a 415 spare in the trunk when I got it.
The most appropriate 16 inch tire is 225/50 which matches the diameter/circumference of the original. I have mounted 225/55 that I had mounted for prior owned 535is and 635csiA with only having to remember that the speedometer reads a bit higher than original but more accurate in real life. I do like the look of more tire side wall on these cars however.
I have BBS on M6 now without the bolts that the two/three piece wheel that the original had, so is close to the original look. BBS RX223 a 16x8 with an 15mm offset and use the appropriate 72.8 mm mounting ring.
The e28 M5 which is essentially the same chassis as our e24 used a BBS 16 in wheel in 7.5jx16 with ET20 offset. BMW pn 36112225518 at about $450 each some online sources.


Sent from my SM-T377V using Tapatalk

[JimPA]

I’m no longer an M6 owner. Both mine had TRXs that I did not keep. I agree with Jeff that TRX is a concours-only choice. If that is the only use the car gets, great.

Otherwise, I would get a set of 16s or 17s, for all other uses. I used 17” RC 090, which requires hub rings, on the 2nd M6 and was happy with the setup. Although it’s been awhile since I bought tires for those wheels, I recall they were noticeably less expensive than what you estimated.

[e24mpwr]

I agree with Jeff also.

Beyond the fact that that's crazy money for tires, they're not even good tires. Put your TRX's away for posterity and decide what 16" or 17" wheel makes you like your car better. I promise you'll like how it drives far better...

[SoCalE21]

I had the same issue, twice.
On my first car I replaced with 16” BBS RS.
second car did BBS RA.
Both were staggered 7s and 8s.
I love both those, as they are period correct, we’re a top shelf upgrade in the 80s, and look right.
not a fan of the 17” Style 5, the lips don’t look right.

[RSheiman]

Replace and since the TRX rims are paperweights, keep them and then pass to the next owner in case they want all original. That's what I did.

[Bert Poliakoff]

Replace and since the TRX rims are paperweights, keep them and then pass to the next owner in case they want all original. That's what I did.

They make great hose reels

[TimU]

Save a 75% cost per tyre and replace the TRX rims with 16 or 17" wheels of your choice.

If you're wanting a good standard:

Diameter: 15, 16 or 17 inch rim
Width: 8, up to 9 rear
Offset: ET23 or down to ET15
Stud pattern: 5x 120

Here's some extra info I collected from somewhere:
-------------------

The size of the original rims and tires that came from the factory:

Width x Diameter - Offset(mm)
Stock wheels = 6" or 6.5" x 14" - ET22 with a 205/70 - 14 tire that has a diameter of 25.30"
TRX (165mm x 390mm) = 6.5" x 15-3/8" - ET22 with a 220/55-390 tire that has a diameter of 24.88"
TRX (195mm x 415mm) = 7.6" x 16-3/8" - ET19 with a 240/45-415 tire that has a diameter of 24.84"

The typical replacement rim is:

7" or 7.5" x 16" - ET20 or less with a 225/50-16 tire that has a diameter of 24.85"
7.5" or 8" x 17" - ET20 or less with a 235/45-17 tire that has a diameter of 25.32"

The Tire diameters range from 24.8" to 25.4" .

The rears have plenty of space and can take an 8", 9" or even a 10" rim with the proper offset and tires of 255 or 265.
It is the front that is the most critical and 8" is generally the largest without a spacer or a small ET.

The larger the rim and tire the more stress that is put on the front suspension and the more likely to introduce a shimmy into the front unless the front suspension is tight.

Most BMW's use a 5 x 120mm bolt pattern and are "hub centric", i.e. they are centered by a lip on the hub, not the bolts.

They all have the same size hole (72.56mm) with the single exception of the larger whole in the e39 which will still fit fine, but they will need hub centering rings (not spacers), $15 from Discount tire.

Most after-market rims have hub rings also. The 3-series rims generally won't fit because the offset is too high, running around ET40/48 and the 7-series with an ET of 23 will need a hub centric spacer of 5-10mm

[e24mpwr]

Great and helpful post Tim!

[maxg765]

Hello All,

The info and insight was much appreciated. Thanks to everyone for taking the time to share your knowledge and thoughts. Wanted to share what was decided. After some searching while trying to steer clear of a few scammers, I’ve decided I just don’t have the luxury of time or patience to continue searching for a proper set. One day it will eventually be a set of period correct 16” three piece BBS or Alpina’s.

The last set of TRX’s lasted 16 years. For now, I decided to bite the bullet and went with a new set (August 2022 production) of the TRX GT 240/45/415, the original set/size to the M6. I also ordered a new TRX spare size 390/55/415. Even though the spare in my car looks new, has never been used, or probably never out of the car it is 34 years old.

Unfortunately and annoyingly the warehouse shipped the wrong size of 240/55/415 in place of the 45 profile ordered. Probably the spare being 390/55 profile threw them off when pulling the tires. Next week they pick up the incorrect set and reship the proper size. I know not many go the TRX route. I did not want to modernize the look of car or just buy anything quickly. Although more costly per tire the end result for the whole setup was still less than what a wheel and setup would be out the door. After the install and getting the car serviced (looks like I need a new master cylinder) I’ll share my experience of what it’s s like driving on a fresh set of TRX’s that are’t dried out due to age.

Again, thanks all for sharing your knowledge, it will come in handy when i do find the right set of BBS or Alpina’s.

Max

[DesktopDave]

Thanks for the follow up, I'm definitely here for updates! I've never been in a car with actual fresh TRX, I've heard they're actually pretty decent tires when they're new.

I usually prefer the 7x16" style 5 as installed on the E38 7-series, since they're cheap and have a lot of decent tire choices. 225/50 R16 is an ideal size for the E24 AFAIC. Nice ride, decent handling.

I also tried out a set of the two-piece BBS RC090. A buddy was selling a curbed up set and didn't mind if I took them out for a spin. They do look much nicer than the one-piece style 5, fit perfectly with proper spacers. They look great. Perfect stance, filled out the wheel wells perfectly, updated the E24's look nicely. They were wrapped with some quite sporty 235/45 R17 Pilot Sports. Handled beautifully, as you might expect, and they are great tires. Sadly, they were not a good fit with my Bilstein Sports and lowering springs. Harsh, darty ride, busy, lots of tramlining. Fun for a short spin but tiring on the highway. Definitely not my idea of Grand Touring...not in the E24 spirit IMHO.

I'm still running 8x17" wheels now (E39 540i M-Tech style 66), but with 225/50 tires. The taller/skinnier tires are a slight improvement, and I really like the look, but it's still too firm and darty. I'll be going back to 225/50 R16 on 7x16" wheels, with some moderate 15mm spacers to get just the right look.

[maxg765]

It is my understanding if using the E28 M5 as a bench mark the ideal 16” wheels sizes would be 16”x7.5j ET20. 5x120 bolt.
Can someone educate me on how the following size wheels would affect the car and what would be required to fit them properly. I am not a fan of staggered setups for practicality reasons of rotation but have come across a nice looking set in the following sizes. 16 x7 and 16 x8, 5 x120, ET24 5x120 bolt. I know the narrower front rim would cause the tire to sit more narrow than on a 7.5” rim. Does this 7” front size work for the M6? Does the ET24 work fro all four corners with 7” upfront and 8” rears? Naturally just came across a set yesterday that I think I like.
I’m still putting the fresh set of TRX’s on and will share my experiences but end goal would eventually be a 16” setup.

Thanks

Max

[maxg765]

Save a 75% cost per tyre and replace the TRX rims with 16 or 17" wheels of your choice.

If you're wanting a good standard:

Diameter: 15, 16 or 17 inch rim
Width: 8, up to 9 rear
Offset: ET23 or down to ET15
Stud pattern: 5x 120

Here's some extra info I collected from somewhere:
-------------------

The size of the original rims and tires that came from the factory:

Width x Diameter - Offset(mm)
Stock wheels = 6" or 6.5" x 14" - ET22 with a 205/70 - 14 tire that has a diameter of 25.30"
TRX (165mm x 390mm) = 6.5" x 15-3/8" - ET22 with a 220/55-390 tire that has a diameter of 24.88"
TRX (195mm x 415mm) = 7.6" x 16-3/8" - ET19 with a 240/45-415 tire that has a diameter of 24.84"

The typical replacement rim is:

7" or 7.5" x 16" - ET20 or less with a 225/50-16 tire that has a diameter of 24.85"
7.5" or 8" x 17" - ET20 or less with a 235/45-17 tire that has a diameter of 25.32"

The Tire diameters range from 24.8" to 25.4" .

The rears have plenty of space and can take an 8", 9" or even a 10" rim with the proper offset and tires of 255 or 265.
It is the front that is the most critical and 8" is generally the largest without a spacer or a small ET.

The larger the rim and tire the more stress that is put on the front suspension and the more likely to introduce a shimmy into the front unless the front suspension is tight.

Most BMW's use a 5 x 120mm bolt pattern and are "hub centric", i.e. they are centered by a lip on the hub, not the bolts.

They all have the same size hole (72.56mm) with the single exception of the larger whole in the e39 which will still fit fine, but they will need hub centering rings (not spacers), $15 from Discount tire.

Most after-market rims have hub rings also. The 3-series rims generally won't fit because the offset is too high, running around ET40/48 and the 7-series with an ET of 23 will need a hub centric spacer of 5-10mm

Hi Tim (or others)

Would you be able to advise on offset.
Found a set of wheels I like (naturally just after ordering new TRX tires…) but I am unsure on the offset compatibility.
I see on your post you wrote ideal setup are 7" or 7.5" x 16" - ET20 or less with a 225/50-16 tire

Staggered
Front 16x7j ET24 tires 205/55/16
Rear 16x8j ET 24 tires 225/50/16

Would an offset of ET24 be bad vs ET20?

Thank you

Max

[e24mpwr]

Hi Tim (or others)

Would you be able to advise on offset.
Found a set of wheels I like (naturally just after ordering new TRX tires…) but I am unsure on the offset compatibility.
I see on your post you wrote ideal setup are 7" or 7.5" x 16" - ET20 or less with a 225/50-16 tire

Staggered
Front 16x7j ET24 tires 205/55/16
Rear 16x8j ET 24 tires 225/50/16

Would an offset of ET24 be bad vs ET20?

Thank you

Max

I don't think ET24 will work.

What wheels are they?

[maxg765]

I don't think ET24 will work.

What wheels are they?

Hi

They are genuine Alpina 16”. Production year 1986 by Ronal. The set is with the center caps. Coming off an E28 Alpina. Seller has two sets. One open lug and this set. Both exactly the same staggered size, tires and offset. He’s decided to keep the open lug set as originally the Alpina came with the open lug set. I would have thought that E28 and E24 sharing same chassis would allow for same setup but I am very much not knowledgeable on the mechanics for wheel fitment past the 16” vs 17” and style. Would very much love to grab these if they work. Committed to buying them even though just bought new TRX tires as always wanted Alpina’s.

Max

[DesktopDave]

I'd guess it would work out OK. Regardless of fit, I'd definitely grab a set of genuine Alpina anything if it came along, especially wheels. Nice style, high quality, an OEM plus reversible upgrade that's completely authentic. Are you 100% sure those wheels all share the same offset? Alpina commonly ran unusual specs back in the day, I'd double-check to be sure. I'd be really surprised if anything that fit an E28 wouldn't fit the facelift E24.

It's easy enough to fit small spacers on the car to suit, 5mm is a commonly available size. However, those short spacers don't usually have a hub extension. I've used H&R hubcentric spacers in the past, but only 10mm & larger parts have a spigot. Of course, you'll also be looking at extended lug bolts. I've been strongly tempted to upgrade to wheel studs the next time I space my wheels out.

I'd be reluctant to stagger a street-driven E24 though, even an M6. I do think it looks cool. However, the M6 is a bit nose heavy, and rear camber is problematic on all the semi-trailing arm BMWs. Rear lowering springs makes it even worse, the rear end gets downright spooky in the wet. The rear camber isn't great even on a stock E24, it tends to wipe out the inner tire shoulders quite rapidly. I've been surprised by the amount of wear from my mild 1.5" drop rear springs. I'm planning on some camber compensators to make it work.

[maxg765]

I'd guess it would work out OK. Regardless of fit, I'd definitely grab a set of genuine Alpina anything if it came along, especially wheels. Nice style, high quality, an OEM plus reversible upgrade that's completely authentic. Are you 100% sure those wheels all share the same offset? Alpina commonly ran unusual specs back in the day, I'd double-check to be sure. I'd be really surprised if anything that fit an E28 wouldn't fit the facelift E24.

It's easy enough to fit small spacers on the car to suit, 5mm is a commonly available size. However, those short spacers don't usually have a hub extension. I've used H&R hubcentric spacers in the past, but only 10mm & larger parts have a spigot. Of course, you'll also be looking at extended lug bolts. I've been strongly tempted to upgrade to wheel studs the next time I space my wheels out.

I'd be reluctant to stagger a street-driven E24 though, even an M6. I do think it looks cool. However, the M6 is a bit nose heavy, and rear camber is problematic on all the semi-trailing arm BMWs. Rear lowering springs makes it even worse, the rear end gets downright spooky in the wet. The rear camber isn't great even on a stock E24, it tends to wipe out the inner tire shoulders quite rapidly. I've been surprised by the amount of wear from my mild 1.5" drop rear springs. I'm planning on some camber compensators to make it work.

Hi Dave

Thank you for taking the time to share your knowledge. Much appreciated. My M6 is is 100% stock including still having the rear SLS suspension. I don’t drive it much, hard, or track it thus think I’d be ok with a staggered setup and nose heavy nature. Looks like the only real way I’ll 100% know if these Alpina’s will fit is to physically try it. So…I officially pulled the trigger on them. They are packed up and ready to be shipped, hopefully going out tomorrow. I’ll be sure to post some pics. I’m still taking delivery of the new TRX tries and will be sharing my opinion of what it’s like to drive on a fresh set. The TRX’s and Alpina’s should both be arriving next week.

Thank you to everyone on here for taking the time to help out with sharing your knowledge and opinions.

Max

[maxg765]

Well… still waiting for the replacement new TRX tires. Sent back the incorrect sized set last week, FedEx confirms delivery. Appears “they” forgot to send the replacements.

Max

[1986series6]

Max,

I would like you to reconsider the TRX tires. At almost $2000 for a set of tires, for a little more money
you can purchase a nice set of wheels and modern tires that are superior hands down.

You put out this post and asked the question and the response has been don't do it.

If your going to have the car judged at a National Meet, you have no choice.
If your not going to have it judged, there should be no choice.