Adding bosses to an Aluminium frame…

All the talk on STW over the weekend about bolt on top tube bags, plus the minor bother of strap faffing has got me mulling the idea of putting a couple of rivnuts in my (aluminium) gravel bike’s top tube to take a bolt on bag (And maybe even underneath for some bonus multitool/pump stashing options).

I’ve done it to old steel frames before with no ill effects (so far) but not to an Aluminium frame.

The frame is getting on anyway and warranty is long gone so not really a worry, if I need to replace it in the next couple of years so be it.

In my mind it’s just the same as the bottle bosses already in the down and seat tubes, I have a Rivnut kit and M5 aluminium Rivnuts are readily available.

Anyone done it? any horror stories to share?

Not done it but given many bikes used to come with them, I wouldn’t be concerned.

Just make sure the hole is nice and clean, no burrs or tears.

(have also done it, steel and aluminium)

Cheers both.

I suppose the only other question is how far back to drill the first hole? Maybe Go one 64mm pitch back from the junction? (noting some people are finding issues with certain frame/bag combinations).

Could you bond a small stub onto the TT? Was discussing something like this the other week with someone who was wondering about drilling a carbon TT. Seemed better to 3D print a rivnut surround then bond it all on, it’s only a TT bag so not much weight in it.

No internal routing, but its a Planet X and not particularly light, I doubt it will have skinny tube walls.

If I was looking at doing it to my Carbon Road bike (which I might consider actually, Hmmm) I’d probably 3D print a suitable “captive nut holder” and attach it with VHB tape or similar, but I’m inclined to trust a Rivnut more on a bike that goes offroad and gets shaken about a bit. you’d probably want to use some very short bolts and/or pop a little shim in the back to prevent damage to the tube behind…

I’ve bonded a mount under the TT on my bird using 3m tape and its had a strap and inner tube on it for over a year. No permanent damage to frame and could always add another strap round the tube if I get worried.

Couple of these instead if your TT is one of the covered diameters?

dRj0n Bagworks Barnacle

Could you bond a small stub onto the TT? Was discussing something like this the other week with someone who was wondering about drilling a carbon TT. Seemed better to 3D print a rivnut surround then bond it all on, it’s only a TT bag so not much weight in it.

Its probably worth pointing out what your job is/was jameso.

How about a better bag or strap…? I’ve found that using voile nano straps has made a previously slightly floppy top tube bag (alpkit), much better. I imagine it would work even better with one that has a stiffer internal/base construction. A stiffer bag would be my preference, as you might go to all the effort of drilling holes and the bag is still only attached in 2 areas with a small surface area to fix them down. When you look at the (very expensive) tailfin top tube bag, they use basically a fancy voile nano strap but the mounting feet are large and help stop movement. Voile straps don’t really rub like velcro does either. Also doesn’t really need attaching around the steerer spacers either. Just an alternative thought.

My Dad did the rivnut thing on an alu Decathlon frame for a pump bracket* and it was fine, but he did them off centre. The man is an animal.

*No, I don’t know why he didn’t just put the pump bracket under the bottle cage either…

Couple of these instead if your TT is one of the covered diameters?

It’s not a round section tube, a glued or VHB taped on 3d printed captive nut holder is certainly an option still, but I’m not precious about the frame and a permanent pair of drilled and riv-nutted bosses would be the ‘most secure’ option (IMO).

How about a better bag or strap…? I’ve found that using voile nano straps has made a previously slightly floppy top tube bag (alpkit), much better. I imagine it would work even better with one that has a stiffer internal/base construction.

The current bag lives there pretty much permanently with tools and an emergency buff in it, so it’s got some mass that adds to the floppage. TBH I am close to playing with the idea of making/modifying my own more rigid bag (or even a mini-box?). A rigid, bolted base with some internal structure is what I keep coming back to wanting. Strapped on fabric even with a bit of stiff foam is never going to be quite rigid enough. plus straps are the main root of the faff/wear/annoyance. a ‘better bag’ is a bolted one to me now.

How offended are you by plastic straps? I use these topeak ones for bottle cages on a couple of my bikes.

https://www.tredz.co.uk/.Topeak-Versamount_210356.htm?sku=643004&utm_source=google&utm_medium=cpc&utm_content=Topeak&utm_campaign=shopping&gad_source=1&gclid=CjwKCAjwr7ayBhAPEiwA6EIGxPiAYNn0Pdxifk_jkFxtooq0lgxHZacQBn-Jh7AzcWhY8xCi5gsKnxoCc1kQAvD_BwE

How offended are you by plastic straps?

Hugely 🙂

those do look like quite a ‘clean’ way of adding a pair of bosses (assuming you can trim any trailing ends once fitted), are they reasonably robust in use?

What about this?

stick on version

MICRO PIGGY

How do we feel about doing it on forks? I have a Whyte Glencoe which has some funny offset forks. I don’t have bosses on the fork legs for my bike packing bag racks.

Recipe for death if I drill and tap a couple of holes? The forks are fairly chunky

Some one up there posted an adhesive option. Surprised there aren’t more to be honest. I’d probably sand off the paint but after that an aluminium to aluminium bond should be more than durable enough.