- DIY single speed disc brake converter……….will I die?
I have a lovely 1998 Indy Fab SS Deluxe that I’ve been planning on building up and riding again, but it being rim brake only on the back has been putting me off.
I considered having a disc mount brazed on (or maybe doing it myself), but I decided to go down the non-permanent route.
I’ve seen similar designs to this on t’interweb, but none that I could actually find for sale. So I decided to have a go at my own using a Boxford milling machine we have at work.
My only slight worry is that the forces on the dropout might be a bit much. I’ve fitted a 140mm disc to start off with to minimise the braking force a bit.
[url=https://flic.kr/p/223M1zP]SS Dropout 1[/url] by tom harrison, on Flickr
[url=https://flic.kr/p/DL69q4]SS Dropout 2[/url] by tom harrison, on Flickr
[url=https://flic.kr/p/223M1vk]SS Dropout 3[/url] by tom harrison, on Flickr
Prototypes – first was hand cut and milled in aluminium to get the shape/dimensions, and then CNC milled out of wood to make sure my CAD drawings worked:
[url=https://flic.kr/p/Fhd3LN]CNC SS Disc Dropout[/url] by tom harrison, on Flickr
[url=https://flic.kr/p/FhcS8o]CNC SS Disc Dropout[/url] by tom harrison, on Flickr
Final dropout – finish isn’t perfect, but it’ll do to test with and I can always make a ‘nicer’ one at some point!
[url=https://flic.kr/p/23nj3bU]CNC SS Disc Dropout[/url] by tom harrison, on Flickr
[url=https://flic.kr/p/JtcRbp]CNC SS Disc Dropout[/url] by tom harrison, on Flickr
[url=https://flic.kr/p/23nj8MJ]CNC SS Disc Dropout[/url] by tom harrison, on Flickr
[url=https://flic.kr/p/23nja7C]CNC SS Disc Dropout[/url] by tom harrison, on Flickr
And fitted ready for a ride/test tomorrow:
[url=https://flic.kr/p/DL5SiV]CNC SS Disc Dropout[/url] by tom harrison, on Flickr
[url=https://flic.kr/p/23njdg3]CNC SS Disc Dropout[/url] by tom harrison, on FlickrPosted 3 months agolazlowoodbineMember
As long as the bracket you made is a snug fit in the dropout slot I should think it will be ok. A brace running from the bracket’s upper caliper mount up to the the frames V brake mount would solve any such issues.
EDIT; Hmm no it probably wouldn’t looking at it again. Something to let it lean on the seat stay right under that upper caliper mount would though.Posted 3 months ago
As long as the bracket you made is a snug fit in the dropout slot I should think it will be ok.
It is a very snug fit, no movement at all with the brake on and rocking the bike back and forth.
You’re right though, I am a bit worried by the amount of torque that will be going through the dropout.Posted 3 months agodownhillfastMember
Looks good. The A2Z adapter I have also rests on the seatstay where the upper caliper bolt mount is, so perhaps that braces it a bit there too.Posted 3 months ago
Generally retrofit braze on disc tabs have a brace between seatstay and chainstay. Not something you can do with a bolt-on adapter, I’ve had no issues using the A2Z adapter on a few different frames with 160mm rotor though.tthewSubscriber
.I’d be looking at some way of bracing it to the seatstay to prevent the dropout taking all the force
That was my initial thought too. In fact, both the steel disk bikes I have have a brace between the seat and chainstays to spread the load between them too. Would be a shame to damage that nice frame.
edit – I was a bit slow. Oh yeah, and nice work too OP.Posted 3 months agoandylMember
Looking at the drop out area of the frame you could position the caliper in the triangle between the chain and seat stays like the original mounts on the On One carbon 456 ie rotate your mount around 90 degrees anti-clockwise. You could then make some form of extended pad areas to brace it against them with some form of adjuster or adjustable clamp – ie turn the mount into the seat/chainstay brace itself.
Little bit more work but would look a lot neater and not stick out on the frame so much.
Did you use the official IS brake mount measurements or work them out from another frame?
The A2Z adapter has a little foot which rests on the seat stay but i think you could make something better. The problem you do have the the sliding drop out means it needs to be adjustable as you tension the chain and the gap changes but can be worked around.Posted 3 months agoandylMember
Look at B and D options here: https://www.on-one.co.uk/i/q/FSOOCNCSO/on-one-cnc-anodized-swap-out
The singlespeed design has slots to adjust the brake manually after tensioning the chain.Posted 3 months agojoebristolSubscriber
Might be worth having a look at this adapter. I’ve got one on an old hardtail – it bolts through the qr adapter like yours, but then has a bolt that braces it against the seatstay, and a torque arm which goes up to the v brake mount. Works perfectly.Posted 3 months agomintimperialSubscriber
cynic-al – Member
I’d be bracing it for sure, especially in a high end frame.
Rob Hilton – Member
Needs more spoons
Ah, good, carry on. 😉
He’s right though OP, I’d not ride that, not very far anyway. I think it will bend or snap and bad things will happen. I bet you could add some sort of triangulation to it to support it without too much modification of the design though, and it looks quite nicely made, well done.Posted 3 months ago
Brace it. Like this:
Posted 3 months agocookeaaSubscriber
I modelled something very similar intended for my slot dropout commuter, I was going to do it in mild steel though…
You do have a fair bit of support from the slot faces to react against brake torque so it’s not a given that bracing back to the stay is necessary, let us know how you get on…
Nice work.Posted 3 months agobrantMember
I did design, make and sell something similar for very early on-one frames.
I seem to recall I had bracing under the dropout too.
I didn’t use a CNCd lump to locate it. I used nuts from m6 bolts which are 10mm a/f located by 6mm holes. Much easier to fabricate.
I will see if I can find pics.Posted 3 months ago
Bring a camera along on Sunday Joe and film me going down in a massive fireball
I suspect the dropout will bend given what happened with the torque nuts on the alfine and a similar dropout.
i’m also happy you’ve built the indy fab back up. we’ll need something to ride to the bog next time we go camping.
It’s a beautiful bike serving a vital purpose…Posted 3 months agoSpeederSubscriber
The torque comes from the wheel at 13″ and ultimately will ultimately get reacted at the dropout as there’s no other load path it can take. What happens between, ie the rotor size is irrelevant. Big rotors are “better” because they can both apply more torque at any given instance, have more surface surface area to dissipate heat and the surface moves slower relative to the pad at a given rpm. All that is only applicable up to the point where you can’t generate any more grip and at the rear that point is quite low due to weight transfer.
I’d try to avoid skidding over braking bumps and no back hops but there’s lots of similar products being used in BMX right now so you may be ok.
Good luck, it’s a neat solution to have it outboard of the dropout. Not one I’d have thought of.Posted 3 months agolazlowoodbineMember
Brace added…..what do we think? Still a flaming ball of death?
That’ll be great, for going backwards.
I can’t help thinking that any force strong enough to damage the dropout/bracket would open up that clip like a tin of sardines.
Just a pad to push against the back edge of the seat stay would probably resist movement better.Posted 3 months agomick_rSubscriber
P clip should help, I guess the new extra tab of aluminium also braces against the stay.
Reverse braking is actually quite a relevant comment – a friend peeled off a disc mount that he’d silver soldered. It happened on a failed attempt at a steep banking, braking whilst rolling backwards. With weight transfer, that is probably the worst loadcase for your mount (but doesn’t happen very often)Posted 3 months agoSpeederSubscriber
thenorthwind – Member
Big rotors are “better” because … the surface moves slower relative to the pad at a given rpm.
The outside of a bigger rotor moves past the pad faster at a given rpm
Doh! Of course! I worded that wrong didn’t I! 😳 Anyway there’s more contact area per revolution which means better dissipation of heat and better cooling.Posted 3 months ago
Missed you out today – next week?
Managed to get out, but only for a ride with the gremlin. Hopefully be out next week for a decent ride.
Annoyingly after dropping a load of cash on the Belter she is insisting on riding her old balance bike. To be fair she did 4.5 miles on it. Which is pretty good going!
On a positive note (naysayers take note!) I rode the IF with it’s rear disc mod and didn’t explode in a fiery ball of death 😉
Now obviously a 4.5 mile ride with a 4 yr old, at an average of 3.5 mph isn’t really testing it to the limits. However, I did a few hard rear brakes to try it out and didn’t hold off using it for general braking……and it seems to work. So far.Posted 3 months ago
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