So I’ve just gone to refit my Formula RX caliper to the post mount on my 2010 Rebas and before one of the caliper bolts was anywhere near tight the thread in the PM hole has started stripping! Ugh.

The forks are under a year old and I’ve only fitted/removed the caliper from said Reba twice in that year. As always I was careful to make sure there was no cross-threading of the bolt.

Looking at the kit now I can see a few areas that may have led to its demise; I wonder if the caliper bolts are steel and harder than the fork threads, also when fully screwed in the bolt only seats about 5mm into the PM hole i.e. not much meshing of the threads.

This isn’t something I expect to happen in under a year’s use. Any idea on where I stand with this issue? I’ve contacted Merlin Cycles but won’t hear back till Monday..

I think you will find it very hard to show its a fault with the fork. Is the hole in the fork deeper than the 5 mm engagement with the bolt? You may have enough thread left to secure if you use a longer bolt and you should have had a longer bolt fitted in the first place.

a helicoil might repair it but I would want the opinion of a reputable engineer as to whether there is enough metal to take the tappin out and helicoiling without weakening it.

The hole is about 15mm deep, using Formula supplied ‘long’ bolts to suit the caliper and adaptor.

Rather than a specific fault with the fork, it looks as though either RS haven’t tapped a very good hole or Formula haven’t considered thread depth/material. Surely not something i should have to consider.

Rather than a specific fault with the fork, it looks as though either RS haven’t tapped a very good hole or Formula haven’t considered thread depth/material. Surely not something i should have to consider.

You shouldn’t have to consider that the bolts you’re using are long enough to work properly? It’s unfortunate, but it sounds to me like it’s your own fault (unless you can demonstrate that the lowers are sub-standard or that the threads are over-sized.

A thread repair tap will only be .3mm or .4mm larger than the original hole, but you will have to get it done on a machine to ensure that the hole (and threads) are absolutely perpendicular to the axle. I suspect that TJ is correct in that a longer bolt will just bypass the ruined threads and tighten up in the good ones.

If the bolt only goes in 5 mm but the hole is 15 mm then the bolt is the wrong size and should have been changed on assembly. I am sure you will find a get oput clause i teh instructions saying to be asembled by a competent mechanic – who should have dealt with that issue.

Another option ( depending on clearances might be to screw a stud in to the hole and locktite it in -then you have a male thread rather than female on for the calliper mount depends on if there is enough room for a nut.

I had the same issue on a set of fox forks when using formula brakes, the supplied bolts were far too short and ended up stripping one of the threads. If you go to halfords you can pick up some M5 bolts for around £2, much cheaper and easier than the helicoil method.

Before you nip out and buy M5 bolts, they’re M6.

If you have previously removed the bolts twice as you say then i fail to see how the fork or bolt could be at fault. There would be next to no perceivable problem with the thread having been working (assuming) perfectly for the time you have owned the fork.

Are you sure it wasn’t simply a case of user error? It’s a PITA ass for sure but it will be fixable.

I’m fortunate in that there’s a large fabrication department at work, so I think for ease I’ll get the guys there to sort it out.

Sorted! Should be but the work of minutes to solve.