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Old 01-12-18, 10:50 AM   #1
bark_eater
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1982 Miyata 610 as 650b Randonneur?

I've got a line on a 1982 Miyata 610. This is the precantaliver brake model with downtube shifters. I've been looking at Sports Tourers on craigslist with the idea of a low trail 650b conversion, but just as an idea.

What I do have, is hundreds of miles of country roads right starting at my driveway and a number of established long distance events that pass through every summer.

I'd like to confirm that this bike will be a good start for an all day riding bike. I weigh in at 230lbs and have a short of leg, long of back build. The I think Miyata frames are a little shorter on the top tube than the comparable Treks, but I don't know how this will translate with Randonneur bars.

The Miyata looks to have less BB drop which is good for dropping to 700c or 650b wheels, but I don't think it has a lot of tire clearance. I read that 27x 32mm tires with fenders is the limit, and being on the Clyde scale I like fatter tire.
So I'm wondering the Miyata will get me down the road with 27x32 tires, and how much of a clearance improvement will I get dropping to 700c or 650b?

Or should I keep looking for a more suitable frame?

Thanks, Woody

Last edited by bark_eater; 01-12-18 at 11:16 AM.
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Old 01-12-18, 12:40 PM   #2
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The first thing you need to do is measure the distance from the center of the BB to the ground and then compute how much that will be reduced with 650B tires. In all likelihood it will be an ideal conversion opportunity, as are most Japanese bikes of that era.

As an example, my late 80's Schwinn Voyageur came shod with 27 X 1 3/4 tires, but it easily takes 650 X 42 Compass tires that measure out to an actual 40mm or so.

Your weight should not be an issue with properly built wheels.
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Old 01-12-18, 06:37 PM   #3
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Going from 27”/630mm rims to 650b/584mm rims will require an additional 23mm of brake reach. That could be an issue depending on how long of a reach the original brakes have.
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Old 01-12-18, 07:06 PM   #4
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From a quick Google survey I'm pretty sure it has been done. I would have to go back through my book marks to see if the length and model of the brakes are noted. Unfortunately just because it's possible doesn't make it a good idea.
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Old 01-12-18, 08:44 PM   #5
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Quote:
Originally Posted by bark_eater View Post
From a quick Google survey I'm pretty sure it has been done. I would have to go back through my book marks to see if the length and model of the brakes are noted. Unfortunately just because it's possible doesn't make it a good idea.
650b is always a good idea! ;P
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Old 01-13-18, 01:06 AM   #6
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Be sure to look at these 650B conversion guidelines. In particular, check the possible tire size in both front and rear.

650B Conversion Guidlines

About the BB height - seems like lots of folks ask about that, but I don’t find that to be an issue on my own conversion, although I did switch from 175 to 170mm cranks arms, and discovered I prefer the easier spin with the shorter cranks for these 68-year old legs. I’ve never been a pedal through the corners rider anyway, even in my racing days.
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Old 01-13-18, 09:26 AM   #7
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Good link, dfrost. I find that I don’t pedal so much through tight turns. What has caught me is pedaling over rough stuff and catching roots, rocks and irregularities.

Use bikeman’s guides and see just how big you can go. It is important to compare what the max size tire is. I don’t know what the biggest tire size is for a 610, but touring bikes typically had large clearances for bigger tires and fenders.

I would also consider a 27” to 700c conversion. This is much more easily done and it is easy to find tire sizes. I have done this on a number of bikes and easily got clearance for 38mm tires.

Last edited by mountaindave; 01-13-18 at 10:53 PM.
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Old 01-13-18, 02:18 PM   #8
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Nice bike, go 27 to 700 with Panaracer gravelkings.
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Old 01-13-18, 08:41 PM   #9
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I think i would be happy with 700x38's and fenders.
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