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My girlfriend's brother borrowed my girlfriend's bike and fell off it in the ice a couple of weeks ago. This had the unfortunate effect of ripping one side of her pannier rack out of the frame. The threads on both sides are damaged - the side with the brake, I've managed to bodge just by putting a nut on the other side of the hole. The side where the gears go, though is also damaged and there isn't room for a nut without it catching on the chain.
What to do? Is it possible to fill a hole in an aluminium frame with anything and re-drill it? Or can I make a bigger hole, tap a thread and use an adaptor / insert without weakening the frame? Suggestions please!
If there is plenty of metal and its a M5 at the moment then tapping out to M6 is perfectly possible - I have done this.
Or a helicoil insert - I have also done this.
Both easy fixes
Drill it out so bolt goes through, then use a longer bolt with a nut at the other side of the frame?
EDIT. Ignore me! Didn't read the OP properly.
Not enough room at the drive side
helicoil insert is the method i know of (from fixing paintball markers 20 years ago) The helicoill was a very effective and durable fix for a brass screw into thin aluminium.
Would there be enough space between the frame and cassette for a round head screw?
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Then put the bolt on the outside of the rack?
Ive drilled out and retapped a stem, pretty easy job and if you keep your eyes open you can pick up tap and die sets quite cheap
Thanks for all the replies, folks. I'm at work so can't address everything in depth but:
No, not room for a bolt head on the inside. Good thinking but already been there.
Helicoil - never heard of this before, I'll look into it.
I guess it's a 5mm thread, same as a bottle cage and just about everything else. I think I'm probably best to continue to use 5mm bolts for future compatibility so it sounds like I want to drill, tap a bigger thread and then use one of these helicoils (Google time).
I'm in Sheffield - does anyone know where I might be able to find these (tap and die and helicoil)? As long as there's a solution, I don't mind a problem - generally I end up better skilled after, and I do enjoy a good bodge!
Buck&Hickman, Riverside Court in Sheffield.You'll need an M5x0.8 thread repair kit.Will work out much cheaper to tap out to M6x1.0 in the short term though.
Helicoil is not a bodge. Kits are easily available. I prefer M6 bolts for lower rack mounts anyway so I would tap to M6 but helicoil to M5 is a perfectly good repair
P-clips and attach the rack to the seat stays?
I apologise for my mis-use of the word "bodge".
Coastsy: I just called in at Buck & Hickman on my way home (I live in Pitsmoor) but they were closed. I'll try phoning them tomorrow.
You'll also need to buy a tap-wrench (if you haven't already got one),whichever way you decide to go about creating a new thread.May be too late now, but it may be worth ordering it for collection via their website as they're normally a next day collection point for things like this.
I would be very suprised if the kit is not available in Sheffield - a decent bike shop will have helicoils as well
Cool. Ta.
Another question: If I go with Jeremy's solution of just tapping an M6 thread, can I then later insert a helicoil to make it an M5? My suspicion having looked at pictures of helicoils is that they convert (for instance) an M6x1.0 into an M5x1.0 thread - is that correct? If so, I guess I have to tap a 6x0.8 thread to convert into a 5x0.8 thread, so I have to decide what to do right from the start.
Of course, if I can tap a 6x1 thread and convert it into a 5x0.8 thread later, that's fine, I'll just get a 6x1 tap for now and use a fat bolt.
(I am liking this forum)
Can't see how a M6 x 1mm could ever ae helicoiled to an M5 x 0.8.
M6 way better for aluminum imo.
Can't see how a M6 x 1mm could ever ae helicoiled to an M5 x 0.8.
If I've understood helicoils correctly, neither can I.
My only concern at using M6 is that racks won't necessarily come with big enough holes for M6 bolts - I'm pretty sure the disc specific one on my bike didn't. I know I can drill them out, but if they then break, shops will just blame me for modifying them.
They won't break.
Drill the hole out at 5.2mm, countersink the inside face of the hole and fit an m5 countersunk bolt from the inside ?
An M5x0.8mm helicoil requires a 6.3mm hole, threaded with a specific helecoil tap, into which is screwed an M5x0.8mm insert. A 6x1 thread requires a 5mm (6mm - the 1mm pitch)hole for tapping, the outer diameter of the tapped thread becoming 6mm, so it's still feasible to tap to M6x1.0, and be able to fit the M5x0.8 helicoil at a later date.
I appreciate your optimism, especially given your username :). I've had racks break at the bolt-hole before (I spent a "fun" hour "drilling" a new hole in a broken strut with a swiss-army knife somewhere on a desolate moor in North Yorkshire a few years ago), but they were the early aluminium ones that just weren't chunky enough. The modern ones are much thicker and more rigid so you're probably right.cynic-al
They won't break.
That's cunning. I'll consider it but I think I'm sold on the 6mm plan nowdropoff
Drill the hole out at 5.2mm, countersink the inside face of the hole and fit an m5 countersunk bolt from the inside ?
I'd convinced myself that wouldn't be possible, but that sounds ideal. A plan, even. I'll give that place in Attercliffe a call in the morning to see if they have a 6x1 tap at a sensible price.coatesy
it's still feasible to tap to M6x1.0, and be able to fit the M5x0.8 helicoil at a later date.
Lots of taps cheap on ebay. You'll get away with the middle one given it's not blind.
A 5mm bit will do ok too, ap it's aluminium...wiggle it around to get 5.2 if you like 😀
But yes do check you've enough meat on the rack to oversize its hole (fnaar).
If you had to google helicoil and you don't already know where to buy taps, I'm guessing you're not a mechanic.
You only get one chance at getting it right with a frame, so it might be best to just take it to a local engineering company, someone who's familiar with drilling and tapping holes, and get them to do it.
Go through the back door, not reception, and it will probably cost less than buying a drill bit and tap.
If you were near me and could call in at work, I'd do it for free and find an M6 bolt.
can you get one of these *in correct size
hammer tabs flat and mount on the chainside wth the 'tube' thru the existing hole
gusamc - I ended up going with your solution, after making a mess of tapping to M6 (should have used a smaller drill bit - used 5mm and ended up with a hole too big!). It works perfectly, and should be tougher, what with being steel instead of aluminium. Ta!