Inch bolt sizing for my Morris rims?

Being from Europe I don't have any experiance with Inch sizes...

I am in need of new front brake rotor bolts for the Morris wheel/ rotorcenters on my Martin Z1, these were a bit of a nightmare to get out, a lot of them were already damaged, one even had a bit of broken off tool still stick out of it. Thing is that the allen key needed is pretty close to a metric 5mm bit but not quite so that was probably been used...

They have a tapered head and fit a 3/16 Allen key
Thread length is 0.6" and the thread itself is "Whitworth 55° 18G 5/16" accoriding to my little thread measuring tool. I measured the thickness of the thread and it's 0.3" but that measurement needs to be a "fracture" size like too I suppose to order new ones? so that would make it a 5/16? The thread of the bolt itself being a bit smaller and the thread hole itself being a true 5/16?

I hope to find them locally, maybe at the Harley dealer?

If you don't get an answer here you may want to try some Harley sites. Some of the Harley XR750 flattrack bikes used Morris magnesium wheels.

650ed wrote:

If you don't get an answer here you may want to try some Harley sites. Some of the Harley XR750 flattrack bikes used Morris magnesium wheels.

Really hoping to get the answer on here, visiting Harley sites with questions about my Kawa being plan B. BTW in my search for the origin of my wheels (at first I didn't know what they were) I found out that the Factory Cafe Racer XLCR came stock with Morris wheels but the aluminum type, like mine.

The Morris Mags on my KZ750 twin use four standard 3/8" x 16 bolts about four inches long that extend all the way through both front brake disks and have nut's on one end.

Morris Mags are generic, it's the hub that makes a difference, so you may have a problem finding someone with the same hub adapters.

The hub adapters would be simple to make on a lathe.

steell wrote:

The Morris Mags on my KZ750 twin use four standard 3/8" x 16 bolts about four inches long that extend all the way through both front brake disks and have nut's on one end.

Morris Mags are generic, it's the hub that makes a difference, so you may have a problem finding someone with the same hub adapters.

The hub adapters would be simple to make on a lathe.

My mags are different from yours, front and rear both have six threaded holes, rear is fine luckally. On the front the disc centers bolt directly to the hub, these also hold the bearings. On the rear I have the hub adaptors that bolt on the hub, hold the bearings, the stock rear disc and a redrilled rear sprocket without a cush mount.

Now what I need to know is if my 0.3" thick bolt is a 5/16th. And if the Whitworth 55° 18G is American thread.

Here is a pic of the rims before powdercoat.

Morris Mags were originally made by Performance Machine
(PM)in USA which could possibly account for standard fasteners, not metric. Try contacting them www.performance machine.com

American threads for hardware come in fine and coarse threads.
As an example:
1/4"-20, 1/4" diameter 20 threads per inch (coarse)
1/4"-28, 1/4" diameter 28 threads per inch (fine)

5/16"-18, 5/16" diameter 18 threads per inch (coarse)
5/16"-24, 5/16" diameter 24 threads per inch (fine)

3/8"-16, 3/8" diameter 16 threads per inch (coarse)
3/8"-24, 3/8" diameter 24 threads per inch (fine)

To find out what kind of thread you have in those wheels a quick way is to go to an industrial supply place and see if they sell a metric and imperial(or American) thread checker.

It comes on a cable with male and female thread checking pieces, they are silver for one type and black for the other.