E30 rims

[xLibelle]

My speedo reads 6 miles faster then actual and I am looking into getting a 75% diff. converted to 4.10:1. I think mine is 3.73. So the larger diameter would be good.

 

[rjp325i]

Maybe, the difference is not linear. Check it afterward at a few different points. If you have a problem with error my old 1985 318i automatic came standard with a 4:10 rear and you could use that sending unit setup for your speedo. The standard ratio for the 325i is 3:73.

 

[xLibelle]

What should the offset be for a 16x7.5 rim?
How would i figure it for any other rim?

 

[rjp325i]

The offset is stamped right into my Borbet rims. Try to stay as close to stock as possible. Stock is 30mm iI believe. I'm running a 38mm offset with no problems and no spacers.

 

[xLibelle]

So can i go as far a 42mm offset on a 16x7 inch rim?
Eventually, the 325i will have a 1 inch drop.

 

[xLibelle]

Bump.

I need an answer on this guys.

 

[rjp325i]

A lot depends on the tire size you are planning to use. A 205 or a 215 (a plus 2 configuration) should not present a problem. You may be OK with a 225 but I'm not sure on that. There are slight differences in tread widths between tire brands or models with the same size. However I must emphasize that what works on one car can present problems on another such as if the car had accident damage etc. The use of offset ca bushings can help a little as far as clearance is concerned and high spped handling will benefit as well. The wheel size you are contemplating will work though without any problems just do not go too big on the tire size or you may need a spacer.

 

[xLibelle]

i thought a larger offset would be where the tire sits further out from the hub, like there would be a larger lip.

The tire im looking at using is 225/50

 

[rjp325i]

Its the other way around.

 

[rjp325i]

Remember also that the increased tire width is divided between inside and outside the centerline. I have no experience with that offset but I have seen that tire size used without problems. That tire size has an overall diameter of about 1.25 greater that stock. A half inch is the usual guideline.

 

[xLibelle]

great, thanks
now i got to make sure the hub is the right bore. 57.4 i think.
i will definetly show pics of what i get accomplished.

 

[rjp325i]

Like to see it when you're done. You have my e-mail addy, feel free to contact me. If I can help I will. Which rims are you looking to install with what rubber?
A 45 profile brings the overall diameter down to 23.9" from 24.8" in case you are interested. A 205-60-14 tire is 23.6".

 

[xLibelle]

yeah, i was looking at those numbers already trying to predict what my speed change would be. i think with the 225/50 on 16x7 would give me 25 inch diameter. I wanted to bring the diameter up a notch to fill the gaps on the sides of the wheel well and drop the car an inch to even it out and make it more sporty.
Thanks for the offer. oh, Enkei DM5 anthracite finish with yoko dB s2's. i heard good things about those tires.

 

[rjp325i]

The numbers I gave you are from a Dunlop catalog for the 3 sizes. I also use the formula when I don't have the book. Sounds like a nice combo.

 

[xLibelle]

hehe, all you need to do is use the spec sheets at www.tirerack.com

example: http://www.tirerack.com/tires/Spec.jsp?make=Yokohama&model=AVS+dB+S2

 

[rjp325i]

I can do the math faster than use the web site (math backround from work). I've used all 3 methods at different times depending upon where I am and where my computer is.