Wheel and Tire Science seems like Black Magic

[Gilligan]

I am oblivious to what to do to replace the TRX wheels on my 1987 L6. My tires have dry rot and need to be replaced. My mechanic can get the TRX tires for $225 each but I keep hearing that I shouldn't stick with the TRX spec.

If I replace the wheels my mechanic says that I need to be really careful about which ones I choose and that not just anything will work. He was a little vague with this.

Getting to the point, If I like a set of wheels how do I know if they will work on my car or not? I see people with 16", 17" and even saw some 19" wheels on their 6's. Some wheels are 7.5" wide, some are 8" wide - how wide should I go?

I'm not sure I understand what "offset" is, but it takes spacers to fix if the offset is not correct. Is the standard offset for a 635CSi 15mm (I read this somewhere)? Does using spacers cause any problems?

I've read this from the John G. Burns website:

Early Sixes have 14" alloys. These gave way to the new TRX style. Good in their day but expensive and outdated now. Best idea is to run 16" wheels and 225/50ZR16 tyres all round, I like Fulda Extremos. Wheels from any five bolt BMW fit except the E36 three series (wrong offset). New E39 five series wheels need a hub ring to fit but the offset is OK.

Does this rule still apply - can I use wheels from newer model BMW's?

How do I figure what tire size I should use, depending on the wheel size?

Any help to alleviate my ignorance is appreciated. Thanks,

Gilligan

[KC Ron Carter]

Replacement of the TRX is mandated since the availability of TRX is limited and the reason to keep them is not a real deal.

So the next is what size to get.

The suspension is a big factor in any car.

The TRX is crossed to a little over 15 inches.

Increasing the size will cost you gear ratio and performamce.

Yep bigger wheels run slower.

Here are the OE sizes and offsets.

E24 6x14" = 22mm

6.5x14" = 22mm

7x14" = 18mm

7x15" = 20mm

165TR390 = 22mm

195TR415 = 19mm

I use a 225.60x15 on my tow mule and it works just fine.
It is a 23 mm offset and with that size tire no rubbing.

I used the Bilstein Sports and the second spring perch up on the rears.

That gave me an effective drop of 1.5 in the front and 1.7 in the rear. The tire size is very important in any suspension setting and mine are the Yokahama 225.60x15. I also have the complete Paul Gray synthetic bushings in the front.

Here is my close up picture and I have hand space all around and no rubbing ever. I have the tirerack hub centric spacers on these wheels since the hub size on the later models is larger. These are the BMW OE wheels, e39 using a spacer to make them fit, and are polished and not chromed.

http://members.roadfly.com/kcroncarter/e34wheel.JPG

I have made a couple of road trips and after the longest, 3,000 miles, I was up and working on toy projects the next day.

I would buy this same set up again.

http://members.roadfly.com/kcroncarter/635.JPG

Later,
Ron Carter

[jklnhyde]

Gilligan, listen to the Skipper. I pondered for over a year on what wheel/tire combo to throw on my 635. Anything smaller than a 17" didn't show enough wheel to fill the well, and 19"s would leave a sidewall shorter than penny. After looking at hundreds of 6-series on the internet and in person, I decided on 18" x 7.5" smoke silver Alpina replicas with hubcentric adapters and with the correct offset that still gave me a DEEP wheel look. The tires are the biggest that can be fitted without messing with the fenders or asking for a weird wheel offset- 245/40-18 Falken ZIEX 512. There is NO chance of rubbing, even with a lowered car like mine. The tread is aggressive and has a rim-protector strip in case you get too close to a curb, they are about average in price and HOLY SMOKES they stick!! Wear factor is so-so, but I only take the shark out on weekends. Suggestion: look at many sites with cars that have a variety of wheel/tire combos. You'll find one to your liking.
Note- I kept my TRX wheels with brand-new 390's just in case! I will e-mail you a pic or two if you'd like; it looks tough!

[jklnhyde]

I'm pretty sure the bolt pattern for the 6-series is 5 bolts on 120mm circle, same as many GM products...Hmmm, Corvette, Camaro/Trans Am wheels are kinda' nice and plentiful...
With short sidewalls, expect a stiffer ride, but if your car is not lowered it should'nt be noticeable. Oh and watch those potholes!
R.

[Makr]

http://www.roadfly.org/bmw/gallery/photos/photos-03-2004/8-4344259.jpg


Here is a picture of my sixes. They both have 16" wheels, 225-50-16 tires. Both of these cars have been lowered. I think I would have gone with 17" or 18" now, but I remember going from the 14" to the 16" on the rubinrot car, it was a shocking difference, so much wheel. Neither one of these use spacers. They will rub the fronts in the right situation on the older car, not on the newer one, as the e28 based car got a little bigger fender flair, so you should not have a problem with yours. I don't remember what the offset is.

The five spoke wheels are stacked, if you would like to make a deal, let me know. I also have 5 trx tires mounted that are in pretty good shape, one has never seen the ground, they are just in the way for me, so if you want to keep your car just going for now.

[jklnhyde]

Check this out:

[Makr]

I like those.