I wonder if there are people here that run on bigger tyres than original and if they have problems with it. Reason for asking is that I am thinking of either have 225/45R16 or 245/45R16 on the back. The 245 would fill the arches pretty nocely but would they bump into the rear-panels? The rims I would like are 9J and therefor 225 would be a little too small. A light stretch. However the same rims in 8J are not available in the right offset and then I would need thick spacers.
Not easy picking new rims...
Compared to the original Murena 2.2 rear tyres (196/60x14) the 225/45x16 will raise the rear ride height by approx. 10mm and raise the gearing by just over 1 km/hr. A 225 width tyre will fit comfortably on a 6.5" width or 7" width wheel rim. Wheel rims should
always be narrower than the tyre because its the width between the mounting beads that matter and they come inwards from the sidewalls. Both a 6.5" and 7" width wheel will fit on the rear of the Murena with a standard offset and should not foul the semi-trailing arm, and the wheel and tyre should not foul the bodywork. However, please note that the clearance between tyres and semi-trailing arm or tyres and bodywork will be less under cornering than measured when the car is static as things move.
A 245 width tyre will fit on a 7.5" wheel but now the wheel and tyre will foul the semi-trailing arm if the offset is standard (29mm), so you will need a smaller offset* than standard to move the wheel outwards away from the arm. But if you keep the change small - say around 15mm, you would need an offset on the new wheel around 15mm and that should be enough to keep the wheel and tyre away from the semi-trailing arm and probably still not foul the bodywork - although I haven't checked this so you would need verify that for yourself. Also note that once you change the offset the wheel bearing gets a twist torque loading which can reduce its life.
The tyre required for a 9" wide wheel rim would be 275mm or wider and I don't think you should be trying to fit that wide a wheel or tyre on the Murena, nor should something that big be necessary! Also the offset would have to be even less to clear the semi-trailing arm, and then the outer edge of the wheel and tyre are bound to foul the bodywork.
*N.B. please understand that the larger the offset of a wheel, the more it mounts inwards and the smaller the offset the further out the wheel mounts, because the mounting face on the hub does not alter. Many people originally get this the wrong way around.
Roy
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