Originally Posted by kaiv
Do you have wheel clearance info for the E9x m3 application? I'm running 10.5" ET20 up front and the rim clears the stock strut by a couple millimeters. I'm looking for an aftermarket coilover that'll also clear without spacers.
The RS1 is ~5mm smaller in overall diameter so that equals to more room for the wheel/tire.
Originally Posted by M3SQRD
The location of the lower spring mount/collar sits up higher on the RS1 (damper body isn't as short as some other aftermarket dampers). I had clearance issues with my old damper setup but I'd have no problem now running a 10"et25 with a 275 tire - I can measure my current gap with a 9.5et23 but it's significant!
kaiv - the delta backspacing between your 10.5et20 and a 10et25 is ~0.05", and between my 9.5et23 is ~0.38". There's ~0.5" of clearance but I can easily verify...
JRZ also offers the RS1 as a fix height system so the overall dimensions of the front strut is kept as close to OE as possible.
If a longer static height spring is used there still can be wheel/tire clearance issues with the collar/lower spring perch.