@#$%^! bolt size request

[robmacl01]

Anyone out there know what the size of the bolt/threaded shaft is on both fork sliders is on the S? They are the brass-colored rods that the fugly black plastic caps screw onto on the top of each slider.

I am looking at replicating what Martin Fabrication does for a GPS mount on the S but am having a hell of a time determining if it is an M8 x 0.8 or what have you. Thanks much.

[jclark]

I's the same size as a valve stem cap that you use on the tires ( usa shrader valve )

jeff
I use red ones...

[Dave Hopkins]

This piece had me steamed up a while back! I bought a Saeng radar mount. Anyway the thread was 8MM x 1. That is one thread per mm. The local metric bolt place had that thread in very limited sizes, too short for my radar detector mount and of course I was looking for a socket head cap screw (allen) which gave me less to choose from. So;
An SAE "5/16 X 24" (that is 24 threads per inch) for comparision;
5/16 is .312"
8mm is just under .320" (damn close) and
1 mm per mm is just under 25 threads per inch
while the 5/16 is 24
Thus if you buy a 5/16 X 24 bolt and run an 8 x 1mm die over it, the 25th thread will be junk, but the first 6 or so are 99% perfect.
So I bought a 5/16 X 24, cut the length to be exact, no extra as each thread after the first deterorates just a bit, then ran the die over its first about 8 threads. I would not use a stainless bolt for this, threads do not cut as nice as tool steel and you will have junk (every time I have tried stainless bolts I felt I had junk).
The other option is to tap the fork cap out to 3/8 X 16 where you can get a good selection of bolts but ;
A: You may have to counter bore your "Martin" piece, and
B: They will be a bit bulky, overkill, and
C: If you ever want to return it to stock you will have to purchase new fork caps.

[roger albert]

It is a standard schrader valve. Th at means 5/16x24 as Dave says. His math and info is good, but _maybe_ backwards, iirc. I.e. it is really the US thread size (a standard, even in the metric world) but the m8x1.0 is the one that is 'close enough)

I could have it backwards too though, but thought that the u.s. size fit better than the metric one. I haven't confirmed with a thread gauge. Largely academic, but now I'm curious. How did you check the actual size Dave?

Also, a good hardware store will have a decent selection on M8x1.0. It's a fine thread, but not really odd. There are at least a half dozen here locally, and Austin is NOT a good industrial/mechanical town
(I'm struggling to find walnut blast media, for instance) aregh!@#$

[jclark]

Rog - try:

http://www.eastwoodcompany.com/

Mash the button "Abrasive Blasting", then "Media".
$37.99 for 50lbs.

[Dave Hopkins]

Roger
I used a thread gauge and the 24TPI is close but the 1TPM fit perfect. I went to a major industrial supplier, "All Metric Company" in Kent WA and went over it with thier guru. The 8mm x 1TPM in socket head caps is available in very limited selection meaning "too short" for my SAENG mount.

[robmacl01]

Did some experimenting and hit local parts store and the following is what I've been able to derive:
Again, I am talking about the UPPER portion of that @#$% bolt - not the lower with the rubber seal.

1. It does fit the schrader cap
2. It is a British Standard Thread - VERY hard and expensive to come by.
3. It is 8mm x 0.75 - NOT 8mm x1.0. the 0.75 is what Martin Fab uses (talked to them).
4. 5/16 x 32 tpi would work as well - hard to come by, but workable. www.e-taps.com and ICS have it. e-taps also has 8mmx0.75 as well.
5. If I remember correctly, the lower portion is 8mm x1.0.

if you bore out the fork cap to replace with a "normal" bolt, what of the rubber seal and taper on the fork cap where the seal sits?

It is a royal pain.

Thanks everyone.

[Dave Hopkins]

Ahh, I was speaking of the lower thread.