S40: Strange vibrations at high speed

[kilou]

Hi,

when driving at about 140km/h on the highway, I can feel vibrations through the steering wheel, subframe and dashboard. Slower or faster the vibrations dissappear. It feels very similar to unbalanced wheels. However I get these vibrations only with summer tires on alu rims (195/55 R15) and not with the winter steel rims (185/65 R14). Now obviously it may sound like unbalanced summer wheels....but I recently changed all 4 tires for new Michelin, balanced the wheels and again get the same vibrations

There's definitely an issue with those rims but I can't understand what. Rims are not bent, have been correctly torque-tightened and placing the rear wheels at the front etc didn't cure the issue. 4 tires are brand new.

Is it possible that an alignment setting (camber, toe-in) may produce these vibrations with the larger summer wheels and not with the narrower winter rims???? Is there a specific balancing for "high speed" that should be performed???

[lauram]

I would closely examine your one set of tires to see if there is some cupping on the tires. This can lead to vibrations, Also search postings for drive shaft wear and vibrations.

[paulcl]

Have you had a look at the bearings??

[kilou]

Well it's definitely linked to the alloy rims as new tires didn't cure the problem and the vibrations dissappear when mounting the winter wheels (on steel rims). So wheel bearings and driveshaft are not suspected unless they may "over-react" to alloy wheels.

The problem is that balancing the wheels doesn't solve the issue so I guess there is some alignment setting that must but badly matched with those slightly larger wheels and which doesn't impact the steel rims...