Road Cycling - 700c wheel on an older motobecane mirage? please help!

Hi,

I'm converting an older Motobecane Mirage bike (year unknown) into a fixed gear, and I have just come across a detail I hadn't considered (I'm new to working on bikes). I have a new 700c track wheel on the way, but I just read that french bikes of this era tend to use 27" wheels. So, my question is - will this 700c track wheel work with my motobecane? All advice is welcomed.

Hi,

I'm converting an older Motobecane Mirage bike (year unknown) into a fixed gear, and I have just come across a detail I hadn't considered (I'm new to working on bikes). I have a new 700c track wheel on the way, but I just read that french bikes of this era tend to use 27" wheels. So, my question is - will this 700c track wheel work with my motobecane? All advice is welcomed.

Older Motobecane Mirages are indeed 27" wheel. The only problems you would run into would be if you were attaching a brake (either front or rear) in which case you would have a problem reaching the rim with the pads since the 700c is slightly smaller diameter. Since this is a fixed gear, I'm assuming you won't be attaching any brakes.

As far as spacing, Motobecane rear will be 120mm. if 5-speed, 126mm if 6-speed. Not sure what the spacing is on your track wheel, but modern track wheels are 126mm. Since this frame is not race geometry, the ride will be comfy, but the handling will not be real quick. Good luck!

Older Motobecane Mirages are indeed 27" wheel. The only problems you would run into would be if you were attaching a brake (either front or rear) in which case you would have a problem reaching the rim with the pads since the 700c is slightly smaller diameter. Since this is a fixed gear, I'm assuming you won't be attaching any brakes.

As far as spacing, Motobecane rear will be 120mm. if 5-speed, 126mm if 6-speed. Not sure what the spacing is on your track wheel, but modern track wheels are 126mm. Since this frame is not race geometry, the ride will be comfy, but the handling will not be real quick. Good luck!

If my track wheel is indeed 126 mm and the spacing on the frame is 120mm, what can I do to make it fit?

If my track wheel is indeed 126 mm and the spacing on the frame is 120mm, what can I do to make it fit?


The rear triangle will need to be spread 6mm. which means 3mm on each side. This can be done with a steel frame, the trick is who does it and the resulting quality. What you want in the end is a frame that is 126mm wide with the dropouts aligned as well (parallel to hub spacers) It's the last part that will require the proper alignment tools. Some shops can do this and any framemaker can. I'd check with the shops first and to see who's capable of doing this and what it will cost...

The rear triangle will need to be spread 6mm. which means 3mm on each side. This can be done with a steel frame, the trick is who does it and the resulting quality. What you want in the end is a frame that is 126mm wide with the dropouts aligned as well (parallel to hub spacers) It's the last part that will require the proper alignment tools. Some shops can do this and any framemaker can. I'd check with the shops first and to see who's capable of doing this and what it will cost...

Sheldon Brown has a page (http://sheldonbrown.com/frame-spacing.html) devoted to this task - it looks like something I could take on myself. Anyone have any hints besides those on this page?

Sheldon Brown has a page (http://sheldonbrown.com/frame-spacing.html) devoted to this task - it looks like something I could take on myself. Anyone have any hints besides those on this page?

Looked at Sheldon's page. He's a pretty careful guy. This should work fine. I would make sure and use nothing narrower than a 2 x 4 since you will be putting force on the seat tube with the 4" portion. Any thing narrower might put enough pressure on the seat tube to dent and/or distort it.

If I were trying to widen a frame made with really thin walled tubing (Reynolds 531, Tange Prestige, etc)
I'm not sure I would use this method. With the Mirage frame you have, this shouldn't be a problem.

My only other hint is to bend the frame little bit at a time and be patient rather than trying to "reef" the 2 x 4 and get the frame widened all the way on the first attempt.