Well, a search that took over 20 years has concluded with a purchase... 1993 850Ci. I am the 5th owner (according to the Autocheck). A California/Florida vehicle, with a great deal of service records documented and provided with purchase. The car ran like a bat out of hell while driving the 1400 miles from Orlando to bring it home to Oklahoma. While some "TLC" will be needed, mostly cosmetic, there is one question I cannot seem to put my finger on. During the trip home, the vehicle ran phenomenal at highway speeds. However, it seemed to "shake" or "shimmy" quite a bit between ~50&65mph. The steering wheel shook a bit, and the front end was noticeably shaking. Once below 50 or over 70, it was smooth as could be! There are aftermarket ASA 18" wheels on it, and I'm wondering if they may be the culprit. Any ideas? Pictures to come soon... So excited to own this beautiful machine!!!!! ;-)
Contrats on the new ride and yes it is most likely the wheels are possible bent or unbalanced. Also check the tires for any weir wear patterns.
Mileage? Yep, start with tires - if they've been on there awhile, then the problem might evidence itself in an uneven tread-wear pattern. Check tire pressures & make sure they're all the same. Plus wheel balance & trueness as Charlson suggests. Review your records for front suspension maintenance - if control arms, front shocks, any front or or strut-mount bushings, ball joints, tie rods, steering components, etc. have been serviced or replaced. Realoem.com might be handy for reference - http://www.realoem.com/bmw/partgrp.do?model=EG13&mospid=47335&hg=31 http://www.realoem.com/bmw/partgrp.do?model=EG13&mospid=47335&hg=32 Congrats on the E31 acquisition!
Thank you both for the replies... I'm thinking of returning to the vehicle to the original "throwing star/turbine" 16" wheels. However, it appears that the 235/50/16 tire is no longer produced. Am I going to see a significant difference if I use the available 245/50/16? As for the "rumble", it looks as though the previous owner did not install the appropriate spacers when upgrading to the 18's. Will I be alright driving on these for a little while longer until I can replace with the 16's, or a different wheel with the right spacers installed? The car has 118,821 miles.
I had a similar problem. I had a mild Shimmy around 50 mph, so my first thought was wheel balance. Had that done. Test drive, and the Shimmy was almost violent. Could not drive the car over 49 mph, the shaking was so bad. Then I found out about centric rings. Apparently, aftermarket wheels don't have the same diameter inside where they mate with the car's hub and since BMW doesn't use lugs, the wheels don't seem to center. Measure the inside of the wheels and the outside of the hub, if they don't match you need centric rings. There are literally hundreds of them on ebay, you just need to know the 2 sizes. They come in both plastic and aluminum. Get plastics at first to make sure it solves the problem. They are $5 or $6 a set. Aluminum are in the $15 - $20 range.
Well, that's enough mileage to start showing an uneven treadwear pattern if there's some issue along those lines, such as an alignment problem. Presumably the tires haven't been rotated fronts-to-rear-&-vice-versa; if so, the fronts should have even treadwear across the tread width, and the rears likely would show a little more wear on the inner shoulder due to the neg. camber in the rear suspension. Uh, yeah - hub-centric wheels or adapters; that's such a given I tend to forget to consider something so essential for aftermarket wheel fitment. http://www.tirerack.com/wheels/tech/techpage.jsp?techid=91& http://www.tirerack.com/wheels/tech/techpage.jsp?techid=103¤tpage=91 118K is enough mileage for other front suspension components to have experienced wear - it may be advisable to check your control arms, bushings, etc. If you read this (http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=46), you'll know everything needed to decipher a tire size description. A 245 is 10mm wider than the o.e. 235; if whatever tire you stick on there is actually close to 245, it should be a seemingly nominal 5mm wider inboard & outboard. The wider tire but same aspect ratio means you'd have slightly more sidewall height, so the overall rolling diameter would be larger - probably not a rubbing problem given the o.e. size is likely a conservative fitment, leaving room for such a nominal larger fitment. Basically, you'd have more tire filling the wheelwells. With a larger rolling diameter, you're doing less tire rpm's, so the speedo would read slightly lower for the same speed compared to o.e. (ie: you're actually moving at a faster speed than indicated on the speedometer); given that most BMW speedo's seem to be calibrated to show higher than actual speed, you might end up with the speedo showing closer to actual speed. More rolling diameter is a slight change in rear gear ratio, in effect you'd lose a bit of accelerative capability as the engine would be at a lower rpm for any given speed comparatively. However, you'd stand a chance to have a really nominal improvement in gas mileage, assuming that's not eclipsed by a particularly sticky/grippy tread compound - increase in mpg might most likely be observed in longer highway cruising (minus a multiplicity of gas-guzzling full-throttle stabs). More sidewall height, though nominal, might mean slightly better protection against bent rims from pothole & other impacts, and if the sidewall construction isn't overly stiff, slightly better bump absorption, translating into softer bump impact felt while driving. One nominal, probably barely-noticed-if-at-all for street driving tradeoff might be a slight reduction in immediacy of steering response, depending on stiffness of sidewall construction. You can use this to get a more graphic representation comparing tire sizes: http://www.rimsntires.com/specspro.jsp If you don't have the correct hub-centric adapters so the aftermarket wheels fit correctly, and you don't have some correctly-fitting wheels to throw on there, you should get the right adapters for your current wheels like extra-extra asap. I think the hub's function is more to center a wheel than support it, but it surely helps to keep a wheel from shifting due to road bumps & impacts. The lug bolts do the job of clamping the wheel on - I have to guess it's a little tricky to try to get a wheel bolted down in place and perfectly centered by lug-bolt tightening only. At a minimum, I'd think that would only stand a chance with the car up enough so that lug bolts might be tightened with the wheel completely off the ground. As for how safe, I don't know since I've never done it, call someone at the tire rack and they might have a better answer as to how advisable that is. Some hub-centric adapters for your current wheels are probably your fastest immediate solution - if you don't have all the specific wheel information, you may need to measure the wheel's centerbore, which might take calipers to get an exact measurement, so you can get the right adapters. Unless you were buying some other aftermarket wheels right away, it may be that it takes awhile to source some o.e. wheels you're considering at a (relatively) reasonable price.
Awesome MG... Very much appreciated. Yes, it may be a while before I am able to seek out the OEM wheels for this beauty, so the hub centric is most likely the culprit, and I will look into that soon.
Congratulations of the purchase of your 850ci. I also recently bought mine in Florida. Mine has BMW 18" M-Parallel wheels. The wheels and tires are wider in the rear than in the front. We'll be removing them soon to check things over and I'll let you know about what we find, spacers etc. in case the information might be useful. David
Had a rotate & balance done... Seems to have cured the vibration. Still a little leary about the aftermarket wheel size. During the rotate/balance, was informed the appropriate spacers/hub centrics were installed. However, the receipt the previous owner provided me shows that the tires were purchased 12/2008 @ 113,712 miles. Car now, after drive home from Orlando, has 119,018. Only ~6000 miles on tires, but they're 7 years old and have sat for a while until I purchased the vehicle. New issue in new thread to follow.
