Frame tweaking: Pompino with discs and gears

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  • thanks both of you. my basic intention was to run it SS for now but have the hanger on as i'm doing some braze-ons anyway. if i was to run it geared, i would respace it to 130. right now, i guess my main concern is getting a thin rear hub in there.

    although thinking out loud, i could just use a 130 rear wheel with freehub and a single sprocket...

    do road disc hubs come in 130mm? no i guess.

  • ah yes, I forgot about the extra 5mm of disc hub width. That might be pushing it a little too far.

  • so we agree that this whole idea is a bit silly

    i'm spending a grand on a welder to eke another year out of ten-year-old £99 frame

  • Novatec do a couple of 130mm disc hubs (24 or 28h drilling only): XD622SB/A-QR-AA-ABG-11S-130 and D722SB/A-QR-ABG-11S

  • Nice find. It looks like it has the same disc/chainline spacing as the fixie-inc one you linked to earlier, but with shorter endcaps. It would need a change of the axle plus other endcaps to work.

    The fixie-inc one would need (I haven't actually tried one) some spacers behind the rotor to fix the disc-line.

    Maybe the cheapest/easiest way is to buy a rear double sided track hub and use a adapter on the disc side. This also gives you the option of lockring threading for fixed drive.

    There is also a couple of options of using a short freehub and putting it on a normal spacing hub shell from the same brand. 135mm -> 120-122mm, but all need a bit of modification to work.

  • that last option is extremely attractive, because the bike currently has a rear fixed/fixed hub anyway. i had no idea those disc adapters existed. thanks!

  • The Fixie-inc also has fixed threading in the description. It is hard to tell from the photo

  • This adapter is better built than the one above: 6 bolt disc adapter
    You probably also need some rotor spacers as well

  • Magic, ta. i'm sure o could google this, but what is the standard disc line, or is it different for different brakes?

  • on 135mm hubs there should be about 15.25mm from the dropout to the disc mounting shoulder. This varies a little between different makes of hubs. I am guessing this distance is the same for the 116mm trial hub.

    The 6 bolt adapter is 7mm thick so it will sit at 17-18mm screwed on to a track hub (also a guess)

    I.S. brake mounting holes are flush with the rear dropout (0mm)

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  • Before you weld anything, you should check if the chainstay and seatstay have enough room for a rotor.

  • don't worry, i'm not welding i'm tig brazing, so i can safely ignore that advice ;)

    seriously, this input is very helpful though.

  • so the little disc adaptors (i got two for some reason) took a while to arrive but I banged one on my current wheels to see if a disc would have clearance inside the stays. note the precision disc gauge i made out of a shredded wheat box. not sure it's 100% true.

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  • You need to put some spacers on it or the caliper is going to hit the spokes
    I think you need at least 15mm from spokes to disc shoulder.

  • next step i guess is to procure a welder. my preferred supplier is still doing business, apparently, but spending a grand on a hobby tool now seems like a lot more of a risky undertaking

  • didn't see this. next step is to check that i guess. fml.

    anyone got a 140mm (dead?) rotor they want to send me? and sell me some brakes?

  • yes put the disc on and dangle the preferred caliper over it to get an idea of ideal spacing :)

  • cheers. it did look like there was bags of space there though, so i'm pretty confident.

  • done some feasibility testing today

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  • for sure I need to space the rotor out. by at least 2mm, possibly up to 4 if that's not a terrible idea.

    the calliper won't fit in between the stays, unfortunately, but it looks like it'll go nicely above the dropout. I guess this makes sense. normally, on road frames, the axle is much closer to the point where the two stays meet. with track ends, the axle is about 20mm further back.

    i also found this useful page­php?title=Disc_Brake_Retrofits

    helps to visualise the need for the slots in the tab to be parallel with the track ends

  • none of this was made any easier when i started the morning looking at my callipers and literally not knowing which end was supposed to face upwards

  • alternative is to go with fully sliding dropouts...

  • Just get an Arkose

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Frame tweaking: Pompino with discs and gears

Posted by Avatar for fizzy.bleach @fizzy.bleach