Borrani Rims

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skymaster7
Posts: 3
Joined: Sat Jan 03, 2004 7:59 pm
Location: Miami , Florida

Borrani Rims

Post by skymaster7 » Sat Jan 03, 2004 8:05 pm

Has or does anyone know if Borrani RW 4075 will fit on a 330 GT 2+2 in place of RW 3812 ?

Ruedi
Posts: 50
Joined: Wed Jan 15, 2003 4:02 am

Post by Ruedi » Sun Jan 04, 2004 10:42 pm

I don't know if they fit, but I can tell you how these wheels are different:

RW3812: Size = 7 x 15; Offset = -25 mm; Backspace = 63mm; Fits 330 GT

RW4075: Size = 7-1/2 x 15; Offset = -9 mm; Backspace = 100 mm; Fits 250 GT, 365 GT and BB512

All of this information is taken from Borrani brochures.

Hope this helps,

Ruedi

skymaster7
Posts: 3
Joined: Sat Jan 03, 2004 7:59 pm
Location: Miami , Florida

Post by skymaster7 » Mon Jan 05, 2004 4:56 pm

Thanks for the reply. How does Borrani define offset and Backspace?

Ruedi
Posts: 50
Joined: Wed Jan 15, 2003 4:02 am

Post by Ruedi » Tue Jan 06, 2004 8:24 pm

Kind of hard to explain without a drawing, but I'll try anyway:

Offset is measured from the center of the rim (middle of the wheel) to the surface where the splined hub attaches to the wheel hub.

Backspace is measured from the vertical surface of the rim flange (facing the center of the car) to the surface where the splined hub attaches to the wheel hub.

So, both measurements take into account the combination of the wire wheel AND the splined hub.

WillS
Posts: 26
Joined: Fri Dec 19, 2003 9:11 pm

Post by WillS » Wed Jan 14, 2004 1:20 pm

skymaster7,

I found a good diagram & explanation of offset & backspace at:

http://207.158.236.129/Offset.htm

Ruedi, thanks for starting the ball rolling with your explanation.....

Will

Ruedi
Posts: 50
Joined: Wed Jan 15, 2003 4:02 am

Post by Ruedi » Sat Jan 17, 2004 8:20 pm

Not a bad description of the concepts. However, a few things are worth pointing out:

1. In the context of the Borrani measurements, the "Bolt-up Face" is the surface where the splined hub meets the axle. This is what I meant with my earlier remark "measurements take into account the combination of the wire wheel AND the splined hub." The problem this creates is that offset and backspace numbers are quite useless if one tries to measure a wheel by itself and doesn't know how much the splined hub adds to backspace and offset.

2. The Borrani brochures have many errors and inconsistencies. One of them is that Borrani drawings show backspace being measured differently for "Record" and "Standard" wheels: According to the drawings, backspace for "Standard" wheels is measured from the rim to the wheel hub, while "Record" wheels are measured from the rim to the "Bolt-up Face" of the splined hub. I cannot believe that different measurements were applied but that one of the drawings is wrong. I haven't found anybody yet who knows or can confirm which one is right and which one is wrong.

3. The drawings on the web site show backspace being measured from the lip. This is incorrect. Backspace is usually measured from the innermost (as related to the car) surface of the rim, at the nominal diameter of the wheel. This has to be somewhere below the lip on the rim, otherwise the tire falls off.

4. Wheel width is usually measured at the inside shoulders of the rim, not at the outside as shown in the drawings on the web site.

Will: FYI, I responded to your private message with my e-mail address. I have some information for you.

Cheers,

Ruedi

WillS
Posts: 26
Joined: Fri Dec 19, 2003 9:11 pm

Post by WillS » Thu Jan 22, 2004 7:30 pm

Ruedi,
Hope you get this. I've sent you a PM four times but haven't heard back from you. I'm probably doing something wrong, but don't know what. Please send me a PM with your email so that we can correspond.
Thanks,
Will

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