DIY disc mount/stay brace on old steel frame – pic heavy

I have an old Rudge Bi-frame full size 26″ folding frame which has morphed through various guises into what could probably best be described as a bastardised monstercross bike. I use it for touring and general road riding with slicks, and cross and trail rides with beefier tyres.

It’s had a carbon disc fork on it from the start, but I’ve been running a V-brake on the rear. However, since I started using drop bars, the pull ratio’s been wrong, and a mini-V doesn’t give me the clearance I want. Swapping brake calipers with wheelsets is a pain, and discs are just easier and better.

So, long story short, I got around to welding a disc mount and a brace between the stays.

The first thing to say is that I wouldn’t have been able to do this without the plentiful help of mick_r on here. Cheers Mick!

This is the bike before. You probably think it’s ugly and you’re probably right.

In road mode:

In bikepacking mode:

This is what I had to work with, with a disc caliper clamped onto a rotor to size it up:

My first attempt at the stay brace used a section of old rotor (as I’d seen done elsewhere) for the new material. The welded joint proved to be weak at the join between the dissimilar metals and this was the result when I prodded it hard enough:

As I scrabbled around in my scraps box for an alternative, I came across an old 10″ table saw blade. Perfect! I cut a section out and snapped off the tungsten carbide tips.

I cleaned everything back up and set it all up in my vice with various bits and pieces holding it in place. The stays don’t taper in at the same rate, so it’s rather an awkward position – the brace is more or less parallel to the chain stay but at an angle to the seat stay, and of course nothing is square.

Then I did some distinctly amateur welding. I’ve done a fair bit of MIG welding before, but mostly on thicker material and whether aesthetics haven’t been much of an issue (you may argue the same is true here having looked at the bike). It’s not really the right tool for the job, but sometimes the right tool is the one you have.

These are the better of the four welds. I deliberately did the outside ones last since they’re more visible. I ground the ones inside back so they weren’t quite so hideous [welder shame]. The important thing is they’re solid and I didn’t blow holes in my frame.

On to the disc mount itself. Because of the position the mounting holes needed to be in – one above the thicker plate of the dropout, and one above the seat stay (but off-centre and not in plane with it, just to make things more difficult) – I decided to do it as two separate tabs. I cut the rack mounting eyelet off since it was in the way and wouldn’t be useful right next to the disc mount anyway.

Mick kindly lent me a jig he’d made to hold the mount(s) in the right place, which was a godsend.

More grinding back was involved 😳 but it’s in pretty much the right place (the rear end needs a couple of extra washers to space it out enough to clear the rotor.

The whole lot:

And after a few coats of acid etch primer to keep it neat while I work out whether to match it up as best I can or get the whole frame done (yes, the lawn probably does need cutting harvesting by now):

Flame away risk-aversionists of STW!

No spoon?

Spoon? Go on, enlighten me

Ace ‘bodging’ (in the nicest possible sense of the word).

Ignore cutlery references – cynic-al will be along to deny everything shortly.

bodging

Last time I used that term on here, it started an argument involving militant spoon-carvers. Wait a second, is that what the spoon thing is about?

Bravo, Rorsach!

I can fix this

The saw blade usage is brilliant!

That looks like a really nice job.

I like the jig, does it really say “k-nore hole” on it?

Cheers!

Yes, k-nore it at your peril! (or not)

knorr knore gnaw ignore hole 🙂 I still can’t remember why the jig had that extra hole……

I just rattle canned the radbike at lunchtime. Work sCrap bike challenge is on Friday afternoon (pubs and inappropriate bikes may be involved).

many contrafibularities

ace work. the welding especially

Work sCrap bike challenge is on Friday afternoon (pubs and inappropriate bikes may be involved).

Ace. I’m doing the Lakes and Dales loop this weekend (+Friday). Bikes will be more appropriate, but pubs will still be involved. And probably rain.