BMX to MTB conversion, what a palaver! Can anyone help?

[LeeDevelopment]

A lot of head scratching here..... trying to fit an ethirteen chainguide to a BMX bottom bracket shell, oh yes!

The first backplate was an ISCG 05 so by using a Truvative BMX to MTB BB converter I was able to bodge it behind the driveside cup with no problem. However! The backplate was for a double ring chainguide and not a single ring one so I sourced another chainguide for a single ring (hoorah!), this time though it's the old ISCG mount and thus is too narrow to fit behind the Truvative BB converter cup, bugger!

Sadly the Truvative BMX to MTB cups have a recess where the normal bottom bracket is screwed in so using an ethirteen BB ISCG chainguide adapater won't work in this case.

Does anyone know where I can locate a BMX to MTB BB adapter that *doesn't* have the recess in the cups? I've been doing some searching online alas no-one seems to have any in stock.

 

[d8mok]

Re:

Not really what you need to know but on my Spooky I have run firstly MTB cranks with dmr cups and in its current form with profile bmx cranks. Both ways I couldn’t get a BB chain guide to work so I’ve got a dmr chainguide which fits like a front mech. However this was 20 years ago so maybe things have changed.

 

[LeeDevelopment]

....argh, this too is for my Metalhead build. My current thought is Profile 3pc cranks with their external MTB BB holding the ethirteen ISCG adapter mount in place mounted via a non-recessed BMX to MTB converter cups.

 

[d8mok]

Re:

I can vividly remember have loads of issues back in 1999 trying to get the BB and crank set up correct.

Using the converter cups used to creak badly whatever. And never looked right. Went to profile bmx ones and then struggled with chain line and making a bmx chainring work with 9 speed.

 

[LeeDevelopment]

Re:

I've all this to look forwards to, erk!

 

[d8mok]

Re:

However, I did manage to make it work and the bike was used very hard until I retired it I’d that inspires you. I found that the bmx chainrings that profile made came in slightly different thicknesses. I used the thinnest one and it worked with a sram 9 speed chain , XT 9 speed cassette and XTR m952. I tried a Shimano chain and didn’t work and neither did a 8 speed cassette for some reason. No idea why and can’t remember any more useful info

I then restored it back to as new condition (close too) using all the original parts.

 

[LeeDevelopment]

Re:

My plan is to use a Profile mtb spider and a normal MTB ring with mine. Will look at your photo when I get home in a few mins as using my phone at the mo.

 

[wesmamyke]

What you seek was actually made by MRP, not sure if if was specifically for running a chain guide or what.

They made an American BB converter that is flush across the face, and takes a 73mm english BB if I recall. They are raw/polished aluminum, so stand out from the others besides the lack of recess for the cups.

https://www.ebay.com/itm/MRP-BMX-to-Eng ... SwLuRc10-5

 

[ishaw]

Re:

DMR wonder cups are another conversion kit, dont see many around. I had a set on a dmr frame running 2 x 10 and they worked really well, no creaks.

Heres an alternative:

https://rover.ebay.com/rover/0/0/0?mpre ... 2715081743

 

[LeeDevelopment]

Re:

They sadly have a recess.... I'm trying to find non-recessed cups.