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Technical Alloy wheel bolts
Replying to my own post. I've worked it out empirically.
The bolts on the Barchetta steel wheels are Hex 19 mm with a 60 deg taper, 12 mm x 1.25 thread and with a 28 mm long thread portion.
About 10 mm of the steel wheel bolts protrude through the hole in the alloy wheel compared to the full 28 mm (approx.) protruding through the steel wheel i.e. lost about 18 mm of thread on the alloy. There is a taper on the hole in both the steel wheel and the alloys so a flat head bolt isn't necessary.
The first 5 - 10 mm in the hole on the Barchetta hub isn't threaded therefore at 28 mm the threaded portion is too short for use with the Coupé alloys; there is only about 3 - 5 mm of thread actually holding the alloy wheel on.
Happily, by chance, I happened to have a set of Grayston Hex 19 mm, 12 x 1.25, 40 mm zinc plated bolts with a 60 deg taper. These fit perfectly!
Unfortunately the tyres on the alloys I bought are 205s and are fouling the rear mud guard. :bang: So I either need to change down to 195s (swap over the pre-existing tyres) or put in a 4 - 5 mm spacer on the rear hubs.
a
The bolts on the Barchetta steel wheels are Hex 19 mm with a 60 deg taper, 12 mm x 1.25 thread and with a 28 mm long thread portion.
About 10 mm of the steel wheel bolts protrude through the hole in the alloy wheel compared to the full 28 mm (approx.) protruding through the steel wheel i.e. lost about 18 mm of thread on the alloy. There is a taper on the hole in both the steel wheel and the alloys so a flat head bolt isn't necessary.
The first 5 - 10 mm in the hole on the Barchetta hub isn't threaded therefore at 28 mm the threaded portion is too short for use with the Coupé alloys; there is only about 3 - 5 mm of thread actually holding the alloy wheel on.
Happily, by chance, I happened to have a set of Grayston Hex 19 mm, 12 x 1.25, 40 mm zinc plated bolts with a 60 deg taper. These fit perfectly!
Unfortunately the tyres on the alloys I bought are 205s and are fouling the rear mud guard. :bang: So I either need to change down to 195s (swap over the pre-existing tyres) or put in a 4 - 5 mm spacer on the rear hubs.
a
