1x11 MMM - what am I doing wrong?

[maxcr]

I finally took the xtracycle off the mmm and found some time to work on my build.

My amateur mechanic plan to build it up as a 1x11 was: White Industries front crank, 36 TSR chainring and a SLX 11 speed 11-42 cassette and a Shimano GRX RD-RX812.

Take a look at the picture below. For some reason the chain hits the chainstay close to the cassette when it's on the small cog. It's like the chainstay should be lower. Any ideas what might be going on?

The frame looks straight, the chainline on a 110 phil bb seems to be around 45.5mm. I tried a different wheel, a 9 speed 11-32 cassette and a larger chainring but it doesn't work.

Thanks for sharing your knowledge.

Max in Boston

[Bill Lindsay]

Your bike just isn't made to work with that drivetrain.  Look at basically any other bike on earth and see where the center of the rear hub is relative to the chainstay.  They are pretty much on the same level.  On the MMM the modified horizontal dropout holds the rear axle about 15mm below the chainstay, so the chain is going to rub if you try to ride the bike with both a small chainring and a small cog.  

It's just not a good drivetrain choice for that frame set.  You'd want a normal vertical dropout on the MMM to accommodate a 1x drivetrain.  

Those dropouts were the one thing I didn't like about the MMM.  I'd still buy mine back if it was offered to me, but the dropouts were a negative. 

Bill Lindsay

El Cerrito, CA

[maxcr]

Thanks Bill, that makes sense.

Is there an "ideal" drivetrain for this frame? Should I just try a larger chainring? or would a double or triple work better? 

I imagine the 11-speed isn't the problem since the small 11 cog will be essentially in the same place regardless. I ordered a 7 speed 13-42 cassette from Riv, hoping that maybe the larger cog will help. I'll report back but any insights would be appreciated.

Also, anyone know what was the rationale behind using horizontal dropouts on these frames?

Max

[Jim M.]

I give up -- what's an MMM?

[Bill Lindsay]

I'd say something like a 2x9 with a 12-36 in back and a 42/26 in front.  

Bill Lindsay

El Cerrito, CA

On Friday, September 27, 2024 at 7:59:45 AM UTC-7 maxcr wrote:

[Bill Lindsay]

Rivendell Bicycle Works has at times farmed out frame and fork manufacture to different manufacturers.  That, plus a couple other nuances of their supply chain have at times left them with a bunch of extra forks.  Grant is trying to "train his replacement(s)" and move more and more agency to the younger generation, so they took the opportunity to let other Riv folks design a small batch of frames to fit the extra forks.  Those various frames have all carried the Rosco Bubbe name and head badge.  One of the Rosco Bubbe models was designed by Roman, and was a step through frame for wide 650B tires in "Roman's size".  That particular Rosco Bubbe took on the nickname "Medium Mountain Mixte". Some people get/got super indignant over the detail that Roman's Rosco Bubbe is not, technically, a mixte.  I tried to call mine "Trusty MUSTy", where MUST stands for Mountain Utility Step Through.  I had one for a while, and I had a Rosco Bubbe Road model for a while as well.  Both of those bikes had this kind of weird rear dropout architecture, and I think they "learned from their mistakes".  The dropout itself has never been on a full-on production Riv.  

Bill Lindsay

El Cerrito, CA

[Max Faingezicht]

Here's an old blog post that shows this particular Rosco Bubbe model: https://rivbike.tumblr.com/post/154226333284/the-rosco-bubbe-project-frames-and-a-few-demos

Max

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Max Faingezicht

[Max Faingezicht]

Very helpful, thanks again Bill.

Max

On Sep 27, 2024, at 1:10 PM, Bill Lindsay <tape...@gmail.com> wrote:

I'd say something like a 2x9 with a 12-36 in back and a 42/26 in front.  

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[R. Alexis]

I wonder if you could do a 7 speed cassette and move the spacer from the inside next to the spokes to the outside between the smallest cog and lockring to move the chain further in away from the chainstay. 

Thanks,

Reggie

[Laing Conley]

Being a horizontal drop-out, I thought the MMM was ideal for an internal gear hub. I have been playing around with an S-A 3 speed and a Shimano Nexus 8-speed on mine. 

Laing Conley

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