Own a C320 (2001), sport package. Purchased January 2008 with low mileage 67K kms. Now has 120k Kms. Travelled to Florida twice: 2008 & 2009 winter. Car loaded with rear (under bumper, towing type, 1 1/4") hitch bike rack + two bikes = combined cantilever weight approx. 100 lbs. Interior weight front had approx. 350 lbs front driver & passenger. Rear seats folded down & with trunk space had approx. distributed another 350 lbs. (golf clubs, clothing, misc. etc.). Ie. 700 lbs distributed in car & another 100 lbs. cantilever with rear hitch = total 800 lbs..

Both times after coming back safely had to replace the two rear tires due to badly worn inside tread ... presumably due to mercedes 'splay' rear wheel suspension under load. Tires were Toyo Tourevo & wheel alignment done (by Mercedes) verified not a tire nor alignment problem, tires also properly inflated. Now have new Michelin Primacy tires on car.

Has anyone else had this problem ? Is the load, particularly the cantilever bike hitch the culprit, particularly with sustained (6 day, there & back, total highway driving ? Can the Mercedes suspension not take this kind of load ? What if I mount the bikes on roof closer to center of gravity of car ? Alternative is to buy or rent bikes in Florida while on vacation .... cheaper than buying new tires after vacation.

For general info on this model, aside from tire problem .... 1. replacing the gear shift module due to water getting in ... not sure how but did replace it. After car sat idle for a day or so car wouldn't start .... instead of paying for costly electrical investigation (seat module, draw loss etc. decided to buy small instant starter battery, no problems since. Both rear coil springs had to be replaced .... before leaving for Florida. Had Xenon lamps replaced. Plastic clips on gear shift housing broke so gear shift housing left loose rather than pay $140 to replace with same cheap housing. One electronic key works fine two others intermittently .... not paying $200 to replace, probably could be simply reconfigured. Other than that am satisfied with car, drives nice no real problems .... most of time is working out & getting used to the pecularities of german engineering. It seems mercedes does everything different than others & sticks to their methods rather than change with the times. Odd but then when they work they do drive quite nicely.

Any help re rear tire wear problems would be appreciated.

 

For general interest .... received a reply from MB Canada. They say that hitch rear bike racks are not recommended for MB's; " The vehicle dynamics and the handling characteristics change when weight is mounted behind the trunk area. In addition, the load on the tires and vehicle also change from the aerodynamics/coefficient drag created by the raised area behind the bumper."

They recommend a roof rack only. Would have guessed that aerodynamincs are affected by a bike rack; see lots of other cars with rear hitch rack. MB's maybe just cannot compete with differing devices; the lower bike rack is easier to handle than higher roof rack ie. for elderly.

Not sure whether I will be spending $350 for a MB roof rack (I could then mount my VW roof bike rack inserts); may cost me another $400 for 2 rear tires, but will wait & see when ready to make decision next time travelling south. May still be cheaper to simply rent bikes than transport them.

 

Thanks for the comment. I did do some checking & it seems that MB really does not recommend nor install tow hitches for their sedans .... although an MB dealer rep did refer me to go to a reputable place. Unfortunately neither one advised me not to do it. Should have investigated a little further. Don't think the shock absorbers affected the wear; they seem to be OK, but will check them at next Service A appointment.

Come to think of it, I never did see an other MB loaded with bikes ... either on roof or on tow hitch. MB drivers maybe never ride bikes nor golf ... since golf bags don't fit in their trunks either.

I am resolved to get used to the thing since when they work they do drive nice.

Thanks again. Maybe this saga will assist & raise awareness to others with similar hobbies & situations.