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Wheel Backspace Calculations (2nd try)

To: spitfires@autox.team.net
Subject: Wheel Backspace Calculations (2nd try)
From: Dave Chu <dave@ece.concordia.ca>
Date: Thu, 18 Apr 2002 02:54:37 -0400
Looks like my first message never got to the list.  Here it is again, I
want to confirm these numbers, especially the offset for the stock steel
rim of my 78 Spit with the markings "4.5 X 13 X 88".

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

I asked about re-drilling a set of Honda rims to fit onto my spitfire 
a while back.  After some thinking, I have decided it is better to make
an adaptor.  This way, I can switch to other after market wheels instead
of getting stuck with just one re-drilled set.  

I have gotten my hands on a 6" diameter X 10" long solid aluminum cylinder.  
Before I start getting it cut up I would like to ask the list to verify my
back space calculations.  As I understand it, our stock spit wheels has
the following specs:

     4.5" X 13"   with .5" offset  and  3" backspace
                                      (4.5/2   +   .5     + .5  =   3.25")

     (Using the following formula: Centerline + offset + rimlip = backspace )

The Honda rims that I have are 5J14 45  which means they are:

      5" X 14"    with 45mm offset and 4.77" backspace 
                                         (5/2  +  45/25.4 + .5  =   4.77")


That will mean I have to get a 1.52" (4.77"-3.25") thick adaptor plate.  Any
input would be greatly appreciated.  If there are enought interest  will make a
mechanical drawing up and post it on my webpage.


Dave                                                  |\ |     | |      
_______________________________________/\  /\  /\_____| \|_____| |____________
Dave Chu                                 \/  \/       | /|     | |  
Dept. of Elec. & Comp. Eng.                           |/ |     | |      
Concordia University              Voice:(514)848-3115   Fax:(514)848-2802 
1455 de Maisonneuve W. H961       Email:dave@ece.concordia.ca
Montreal, Quebec, Canada H3G 1M8  http://www.ece.concordia.ca/~dave/addr.html
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