bigcoupe.com

Dear Big Coupers,

Please help me retain what sanity I have left and tell me how to get this problem fixed.......my coupe is an '88 635CSi...149K miles.Tires 8K on rear and brand new on front.

Wheels: BBS Type 5 17" 2 piece rims
Tires: Michelin Pilot Sport A/S 3+ 235/45R17 V Rated

Problem: Smooth as silk until 76 mph and above....on all types of roads.

Tried solutions:
Rims have been swapped everywhere front to back. At present, vibration is in steering wheel at 76mph and up.
Rims "serviced" and tested by a rim expert outfit here in New Hampshire. Declared straight and true.
2 road force BMW dealers tests.......2 new tires (Michelin Pilot Sport A/S 3+ 235/45R17 V Rated).........3 different "expert" wheel balancers.

Drive shaft was replaced (was causing vibration felt in rear)......even at low speeds so this was a very valid repair that was needed.
Front end components thoroughly checked and inspected...front end is aligned.

BBS Rims are in great shape and rim tester wise....they appear perfect accept for dings, scratches and scrapes that have been put on them, by service techs, from changing them around and putting on a couple of new tires that did not solve the problem.

Any war stories out there that can get me on the right path would be appreciated. This problem is driving me nuts and costing me a fortune.
Thanks!! Max

Ahhh.
Frustrating.

I've heard even something simple like torquing up wheel nuts can make a difference.

Just a simple thing to establish is the style 5 2 piece wheels are predominantly e39 with the slighly larger bore spacing. Hubcentric rims are needed from 74.1mm to the 72.56mm

Which BBS 17" wheel are you using?? e38 rim? BBS Rs?

Like said already....


Most e39 bbs 17" rims that fit this car had a bigger hub 74mm.

Make sure you are using Hubcentric 72 to 74mm rings and they fit well.

Spigot rings

Back in town and pleased to see 3 suggestions to remedy my steering wheel shaking issue. Very grateful to Pod, brickwhite and GazM3. I am researching the exact rim model and also looking into spigot rings and hubcentrics.......new terms for me. Will post results for others who may have issues.
Thank you very much for responses....makes a hell of a lot of sense.
Cheers, Max

Max, if you have true style 5 wheels, these are intended for E39 fitment and you WILL need a set of hubcentric or spigot rings

Please refer to this thread for in-depth information, sources, etc.

viewtopic.php?f=4&t=3358

Just Google 74.1 to 72.6 hub centric rings. Many tire dealers have them (Pep Boys, Discount Tire, etc.) or order them from eBay, Amazon or other on-line source. They're cheap. Plastic is usually less than $10, metal less than $20. I've used both. Can't say I prefer one over the other. The plastic ones are easy to use, but easy to damage, too. One advantage is they don't corrode onto the hub. The metal (usually aluminum) are more rugged, but they do corrode (even when protected by grease/anti-seize) and are really difficult to remove from the hub even when not corroded in place.

FWIW I think it possibly isn't from a usual cause of wheel imbalance, unless that imbalance is massive. Most imbalances excite the uprights to wobble in a certain way which is at lower speeds, usually at 60mph or less (although that could vary with the stiffness of the upper tca bushings I suppose). In the front wheels this causes the steering to shake and you can feel it through the steering wheel. It changes quite a lot (at constant speed) in a long sweeping bend as the front wheels go in and out of phase with one another.

By contrast I have had only one thing excite a vibration at 75mph plus, and that was a tyre that was falling apart. Turns out that the radial plies had begun to fail in a set of very low profile rear tyres. These tyres manifested no sidewall bulge at all (as would be obvious in the event of similar failure of higher profile tyres) , but eventually manifested a flat spot on the tread. The flat spot looked for all the world like I'd locked up the rear wheels; there was noticeably less tread in that area than elsewhere.

When the wheels were spun by hand (car on axle stands) the worn area looked like a flat spot in the tread. This area held its shape because of air pressure but wasn't correctly restrained and was centrifuged out at speed. There was usually a speed at which the vibration wasn't too bad but above that speed the vibration became worse and worse. Over time the speed at which the vibration set in got lower and lower.

BTW in my case it is possible the tyres were of defective manufacture from day one. But at the mileage I did, it took several years before I realised the true nature of the problem. The fact that I couldn't rotate wheels around (it was a staggered set) didn't help. The tyres were warranted against manufacturing defects for five years; it took slightly over five years to find the true nature of the problem....

So anyway, that the vibration sets in at high speed like mine did makes me suspicious that the tyres themselves are faulty and are changing shape at speed.

cheers

Wow! I can not tell you all how much I appreciate the response....I wish I could buy you all a beer!!
GazM3
brick white
Pod
Grnshrk
Horn Hospital
and Brucey

I bought 4 new hub centric rings from ECS ($10.23 plus shipping) and installed yesterday, torqued the wheel bolts and bingo...smooth as glass at 76 and beyond the wild blue yonder!! I could not believe my senses when I felt no steering wheel vibrations. I drove around and tried different interstates, major roads and anywhere I could drive 80-85 mph!!!

I am sure some of the other work helped (rim straightening, uneven tire, drive shaft) but any sucess was being masked by these damn rings.....one of the rings is a mismatch and thinner measured by caliper (see photo).....no idea when or how that happen but point is, "It ain't no more!!" Since I have gotten so much help and information from this site. My many year restoration would have been so much more difficult without it and due to the fact that I can't buy you guys a beer....I made a donation to the site.....hope it helps to keep it running. No doubt I will be back for more info!!

Thanks to all, Max

Good on you Max. Yes, very helpful people here !