Brake 3

The adapter for the rear bb7 185mm disc arrived from Yuba. It seems they have gone to a lot of trouble to have it CNCed and are likely not making any money selling it for $30. I had a lot of trouble working out how to use this adapter (no instructions included) but finally worked out that you need to use one 1/2 of the BB7 adjustment shims with the bolts and washers they send with the adapter. After a bit of  moving the caliper position with washers etc I got it to mount ok.

Correctly mounted adapter before I broke it

 Then I broke it.

The caliper mounting bolts only go into the adapter about 3 or 4 threads deep so of course when tensioning it up I was a bit over zealous and stripped the thread in the soft alloy adapter. I might work Ok for you but watch out you don’t tension it too much. I probably didn’t need to do it up that tight but I have used a similar tension on the original BB7 adapter with no problems. The Yuba adapter is certainly weaker than the original, so maybe it wouldn’t have coped with braking forces over time and I’ve saved myself future problems?

Yuba adapter compared to the original Avid BB7 adapter note same bolt used

OK so long story short I had a 160mm BB7 rotor and after stuffing about with the adapter I thought I would just put that on and be done with it. But it didn’t fit! Certainly not with the standard adapter and mounting bolts. It might fit if the caliper bolts are adjusted/shimmed etc. I may try again if I can be bothered changing the rotor yet again.

I wonder how many people have successfully mounted rear discs on the Mundo? I only know of one other on the web and he mentions having to “man handle” the mounting tab.

So I have the 3 rotor sizes for BB7s and adapters and none of them mount on the rear of my Yuba without significant change to the mounting bolts or using a fairly weak adapter, nice.

Never fear on we go on this glorious rear brake adventure! I would have given up long ago and gone rear V Brake but as I previously mentioned my rims don’t have a V Brake track.

So nothing to lose with the ruined Yuba 185mm adapter I drilled it right through, made a couple of  “shelves” with my Dremel tool and some cutoff discs (a free Dremel tool should really come with every Mundo frame!), and mounted using some longer bolts with nylock nuts. Mounts nice and secure and so far so good with a 185mm rear brake!

Modified adapter

Mounted on the Mundo

My front brake mounting (original Mundo fork) was never all that good (203mm rotor) and needed alignment but I couldn’t get it to line up without bending the brake mount tab slightly and grinding all the paint and some metal off the inside of it. But it seems Ok now, but it does still shudder a bit if I really pull on the brake, not sure if this is the fork or something else.

Victory? Well it feels a hollow victory really. Are you building a Mundo with disc brakes? Ask youself do you really need them? Anyway maybe I’ve made all the mistakes for you. My pleasure that’s what I’m here for!

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8 Responses to “Brake 3”

  1. Katie Says:

    “a free Dremel tool should really come with every Mundo frame!”

    This made me laugh till I cried. Too true. Glad to see you’re making progress, though, Dremel-enabled or otherwise.

  2. keller74 Says:

    I recently sent an email to Ben at Yuba briefly outlining my “rear brake odyssey”, and suggesting a modification to the adapter. He has replied and tells me “..the bike is really design around 180mm discs”, as opposed to Avids 185mm.

    I also noticed that Yuba now have a disc brake kit on their site, the price looks ok anyway but not sure what the brand or quality is.

    Maybe I fell for marketing hype but I went with the Avid BB7 as all the reviews I could find said that it was the only worthwhile non Hydraulic Disc brake upgrade from V brakes.

    Hydraulic Brakes would be nice! Now there’s a new can of worms waiting to be opened!

  3. Dave Proctor Says:

    I’m concerned with the bolt setup you ended up with. The washer stack forms a universal ball joint, and by getting rid of half of it you can no longer align the caliper with the rotor. I have no idea what that’s going to do to the internals of the caliper.

    • keller74 Says:

      Thanks Dave, I’m not 100% happy with it either and I might get some longer bolts so can include all the adjustment washers (these were just a bit too short). By eye and performance it seems to line up Ok. However the Tab mount bolts have since worked loose which might be a symptom of poor alignment (or just me being nervous about stripping those threads too). Locktight is on the hareware shopping list!

      The supplied bolts from Yuba are only about 1 inch long so couldn’t use all the washers either.

      Actually my next move might be to just try the 160mm rotor again. It might be able to use some extra washers to position it correctly.

      • keller74 Says:

        Yes, more thinking about what I was thinking when I mounted the brake reminds me that i couldn’t mount all the BB7 adjustment washers as the whole adapter is designed to only work when it is mounted flush as I have mounted it. If I put all the washers on the on the whole caliper is out of position. So with this adapter it’s this setup or nothing.

  4. Jorge Luna Says:

    What Rims did you use? for this bike?

  5. Jorge Luna Says:

    Also what version of mundo do you have

    • keller74 Says:

      Hey Jorge, Its an early V3 Mundo, I started with Spinergy Xyclone wheelsets but the rear rim failed after a year (now repaired and on my mountain bike). I replaced them with a full prebuilt Halo SAS wheelset, very wide rims which better suit the big tires I’m running 48 spoke rear, 36 (I think?) front, 2 years on solid as a rock, never even needed truing.
      Mark

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