Caliper Mounting Holes on Fork Legs: Can They Be Tapped?

[IanDMacDonald]

Mounting the R6 Calipers on the XS via an adapter bracket necessitates that I run a bolt through the bracket, through the fork leg mount hole, then a nut on the inside to tighten it together. I was wondering if I could instead tap the holes on the fork legs that the original calipers mounted to, and run my flange bolts into them?

[DiverRay]

Yes. you can tap them. Problem is getting the proper size tap and bolt. I'm not sure, but I think a 12mm MAY work. You will need to measure the hole in the fork, and check tap sizes to match the proper size. Keep in mind, it may be easier to drill out slightly to get a good thread. So you might be into a 13mm or 14mm bolt size.

[TomB]

You will really struggle to get M13 and M14 bolts and taps.

The other alternative I did on a set of Jap forks when uprating the calipers (not XS11) was Helicoil the hole, the hole was too big to tap out to a decent size and the next size up was way too big, but the existing hole was ideal tapping soze for the helicoil. Insert fitted and use of M10 bolt again.

Another alternative is use a nut on the back.

[IanDMacDonald]

M10 clearance hole if anybody is curious.

[IanDMacDonald]

How do you guys feel about me using heli-coil inserts in the fork legs and tightening bolts into them, versus a bolt and nut?

[crazy steve]

A properly-installed helicoil is stronger than a hole into just aluminum. And I've done this trick multiple times, using a helicoil to reduce a hole size. The one tip I'd add to this is liberally apply Loctite to the coil when installing it, to prevent it from 'turning though' the hole when installing the bolt. I've also done this to convert from metric to more-easily-found 'standard' hardware when doing mods.

[bikerphil]

I use nuts and bolts with my adapter plates, makes it a little more difficult for installation having to hold the nut in that narrow space to get it started.

[trdriver71]

I would like to see a picture of how that looks on the bike!

[IanDMacDonald]

Fellow forum member had concerns pertaining to the aluminum being brittle. I'll throw some M10 heli coil inserts in and see what happens.

[DiverRay]

Use plenty of cutting oil, and back off the tap often.

[Gmac]

I used to be

an assembly tech for a goverment subcontractor and we used helicoils in a lot of places to make sure that threaded items didn't strip out of the softer aluminum.

+1 on the locktite, go red!

[ViperRon]

Helicoil and locktite will work but I personally would use the nut and bolt because if I bear down on my brakes going fast I don't want to be thinking I wish thoughts.

I wish I'd used a stupid nut
I wish I was going slower
I wish Bambi would get out of the road
I wish I had more insurance

[IanDMacDonald]

Helicoil and locktite will work but I personally would use the nut and bolt because if I bear down on my brakes going fast I don't want to be thinking I wish thoughts.

I wish I'd used a stupid nut
I wish I was going slower
I wish Bambi would get out of the road
I wish I had more insurance

I hear this from a few Ron. Can anybody say (I'm no metalurgist), that a bolt going through the hole with a nut on the other side is stronger than a bolt threaded into the hole?

[crazy steve]

Remember, those bolts will be in shear, not tension; the same forces whether there's nut there or not. Also remember that the OEM caliper brackets are threaded aluminum, and you haven't heard any reports of those failing, have you?...

[TopCatGr58]

Remember, those bolts will be in shear, not tension; the same forces whether there's nut there or not. Also remember that the OEM caliper brackets are threaded aluminum, and you haven't heard any reports of those failing, have you?...

Hey Steve,

Can you provide info regarding which bolts are more resistant to the shear forces, the grade 5 vs 8? Also I think Metric uses a different grading system as well, just can't recall all of the details. Ian may know this, but others reading may not and may appreciate the full info.

T.C.