Monday, January 5, 2009

BMW wheel bolt pattern

I see a lot of people looking for the BMW bolt pattern. It is as follows:

4 lug -> 4x100mm or 3.937 in. ---> All 4 lug BMW's all years

5 lug -> 5x120mm or 4.724 in. (chevy is very close to this) ---> All 5 lug BMW's all years

A four lug or five lug bolt cirlce is an imaginary circle running through the center of the lug holes. A 4 lug pattern can be measured from center of one lug to the center of the lug diagonally across from it. A 5 lug pattern is much more difficult to measure, due to the fact that the lugs are not equally opposite and would require a bolt pattern gauge.

Offset: The offset is where you run into trouble. The offset of a wheel is as follows: the distance from the mounting surface of the wheel to the true centerline of the rim. A positive offset means the mounting surface of the wheel is positioned in front of the true centerline of the wheel. This will bring the tire in to the fender well more. A negative offset will mean that the mounting surface of the wheel is behind the true centerline of the wheel. This will cause the tire to stick out away from the vehicle..

Most 5 , 6 and 7 series wheels will work on each other.
Early 3 series cars were 4 lug. The 3 series cars that are 5 lug, E36, E46 and E90, have a front wheel drive offset (negative offeset). This pushes the hub portion to the outside edge of the wheel and cause 3 series (5 lug) wheels to not fit on 5, 6 and 7 series cars. The back of the wheel will hit the strut before the hub surface makes contact. The 5, 6 and 7 series wheels will bolt onto a 3 series (5 lug) but tend to stick out and rub on the fenders (posative offset).

Here is a link to a bunch of factory wheels

M52 Dual Mass Flywheel

SO my new year started off with a Bang!! Right when I shifted from 2nd in to 3rd. BANG! We'll find out tonight what it was. I think my dual mass flywheel became 2 single mass pieces. The fly wheel has been shaking and chattering for the last couple weeks and I was hoping to get a lightened single mass replacement. No such luck right now. I'll just have to replace the one that's in there with another M52 oe flywheel. Hopefully it's not the transmission.

Late night update.....Dropped the trans out tonight in the driveway. Found out not only is my dual mass fly wheel bad, the car stopped moving because the center broke out of the pressure plate. Wierd! I haven't seen that before, the welds that hold the splined ring that fits over the input shaft on the trans, all broke. Maybe the vibration from the fly wheel caused it to break apart. I will post a picture of it when I get the pressure plate and fly wheel off tomorow.

All righty then, one week later and the E30 is back on the road. I ended up installing a 2000 528i E39 flywheel and self adjusting clutch. The pedal feel takes a little getting used to. Its's kind of soft. I didn't install the pressure valve on the clutch slave. I may add it later this week if I end up not liking the soft pedal.

It took me so long because of a leaky injector that wouldn't seat properly into the injector rail. I had removed my intake to make it easier to get at the starter and top trans bolts. Plus I needed to fix my pinched heater hose. I broke the bottom of the #5 injector when I popped it out of the intake and the replacement injector o-ring wouldn't seat into the fuel rail properly. What a pain in the ass.

I also have a clicking in my right rear axle shaft, so later on today I will be swapping that out. I guess this engine and injection set up is just a little bit to much for some of these old E30 parts. Luckily I can do most of the work myself.