ShopTalk Forums | Aircooled VW Tech & Restoration Help

What is the widest tire possible with stock fenders and stock beam?

Depends on the offset, but I have seen cars running 205's in the front, but alot run 185's which are still nice.

Balljoint, right?
We tried a 195/60-15 on my son's car which has CBPerformance diskbrake drop spindles - because of the spindles, the 5½" steel rim interfered with the lower balljoint; adding a ½" spacer fixed that problem (it was just enough) and put the outer sidewall out past the fender by a little bit - he gave it a good test-thrash and couldn't ever get the tire to rub on the fender but it was very close. Based upon that, I'd say 195/60 is about the limit with drop spindles for most (15") rims; there may be rims with a different contour that would clear the lower balljoint better, but no matter what you'll have to have just the right backspace. With stock spindles you could go a little wider, but the inner sidewall is probably going to hit the control arm/swaybar unless you crank in on the pitman arm stopbolts and live with a larger turning circle.

"More information to be found about fitting big rims up front...

From a member here(jj8319):

`74 standard beetle, standard width fenders, standard width beam, stock spindles, 17x7 ET40 205/40 rubber. No rubbing or cutting"

http://www.shoptalkforums.com/viewtopic ... 33&start=0

Chris V wrote:"More information to be found about fitting big rims up front...

From a member here(jj8319):

`74 standard beetle, standard width fenders, standard width beam, stock spindles, 17x7 ET40 205/40 rubber. No rubbing or cutting"

http://www.shoptalkforums.com/viewtopic ... 33&start=0

Chris, I know "ET40" is the backspacing, but what is that in inches. i was looking at some wheels (not in person, so could not measure) that have a backspacing of ET15 but I don't know what that is
Mark

kafer-cup wrote:I know "ET40" is the backspacing, but what is that in inches. i was looking at some wheels (not in person, so could not measure) that have a backspacing of ET15 but I don't know what that is

The ET ("Einpresstiefe") number is the offset, from which the backspace can be determined if the width is known - see the explanation here:
http://www.oxfordshirevwoc.co.uk/wheels.htm
Since width is measured from bead-to-bead and backspace is measured from the external edge of the rim, there's about ½" difference that needs to be taken into account when converting from one to the other - and that can vary somewhat from one rim to another, especially when comparing alloy rims to steel ones.

Thanks, that is what I was looking for.
Mark

To find backspacing of a rim:
1) Add 1" to the bead-to-bead dimension (7"+ 1"= 8")
2) Divide by 2 (8"/2=4")
3) Multiply by 25.4 to get mm (unit of measurement the ET number is in) (4x25.4= 101.6mm)
4) Add or subtract the offset number, in this case with +40ET you add. (101.6+40=141.6mm)
5) Divide by 25.4 to get back into inches. (141.6/25.4~5.575")

Answer an 17x7 inch wheel has got 5.575" backspace

This particular wheel may work on an otherwise stock `74 but once other variables enter the picture it gets confusing. The drop spindles obviously push out the track, while also reducing lower BJ clearance, the wheel diameter and inner contour also play a role as my father and I have found, clearance to the sway bar or other items inward of the bolt plane of the wheel also must be considered, sometimes it is neccessary to limit the steering stops to leave clearance, and last of all fender rub - which can be taken care of by wider fenders, narrowed suspension pieces, and smaller diameter/width tires.

Thats even better, Chris. I was looking at a 6x15 wheel with a ET15 backspacing. Using your explanation I get a hair over 4" which is what I have now with my current 6" rims, so I would not be gaining anything but I'd be saving money by not buying those rims.
Mark