I was on a short ride and hit a disguised pot hole and all of a sudden it's hard as hell to peddle. Check the brakes thinking they were sticking, then noticed the rear frame part had come out of the main hub and the rear tire was rubbing right up against it.

I took it to my local Trek dealer who's done service on it, but frame repair is out of their league. They gave me the name of a shop on the south side of Chicago that does frame alignment and repair. I called them and they were very helpful. They said that some of the old Miyatas were made with both steel and aluminum tubing and were bonded and if that was the case, it wouldn't be fixable with brazing. I did the magnet test and dammit; steel and aluminum.

So my trusty road bike of 34 years has been replaced with a Trek FX3. Took my first ride on it this morning and despite having standard pedals, I achieved an average speed well above my norm for 18 miles. I'm not sure if I'll put clipless peddles on or not, but the more upright ride was more comfortable my "old" body.

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Sorry Mike! Corrected.

That's a 1990 Miyata 721A, pg 11 at the following archive:

https://www.ragandbone.ca/PDFs...20Catalogue%2090.pdf

Steel seat & chainstays bonded to an aluminum front triangle is unusual. I don't know of any other manufacturer who did that. If you're feeling daring you could try JB Welding that seatstay back into the bottom bracket lug.

What's stopping you from transferring the clipless pedals (Time ATACs?) from your Miyata to your new Trek?

Trek definitely bonded many of their frames in the early 90's. My brother still has my Trek 8000 mountain bike that is bonded 7000 series aluminum. They also bonded carbon fiber tubes into metal brackets for some VERY early carbon bikes. Probably 1994 or so.

It sure looks like that could be fixed by cleaning it and applying some good quality epoxy.
Another option would be to find an experienced welder. It won’t be cheep but aluminum can be welded.

iron chef, I may transfer my peddles to the new bike. Still getting used to a whole new platform.

I'd be afraid to try any kind of epoxy/liquid steel type of repair myself. If it could be welded/brazed to make a good repair, I'd be all for it, but the break is between steel and aluminum, making welding impossible as far as I know.

This message has been edited. Last edited by: 6guns,

The bottom bracket shell is almost certainly going to be steel, which means a half-decent frame builder could probably re-seat and braze the stays. Worth it if the Miyata has sentimental value. Probably not worth it otherwise.

I still ride a steel Schwinn from the same era. I've tried carbon frames and aluminum, but they just don't feel "right" to me.

Yeah, no JB Weld on a bicycle I'm riding at 25 miles an hour on asphalt wearing shorts and a tee shirt.

Dennis, based on a magnet test, the bottom bracket is aluminum and the rear fork piece that popped out is steel.

If I could get it fixed for a reasonable price, I would. I'd like to use it as a second bike. I just don't think it's possible to make a good aftermarket repair with dissimilar metals.

quote:

Originally posted by r0gue:
Trek definitely bonded many of their frames in the early 90's. My brother still has my Trek 8000 mountain bike that is bonded 7000 series aluminum. They also bonded carbon fiber tubes into metal brackets for some VERY early carbon bikes. Probably 1994 or so.

Many manufacturers bonded aluminum to aluminum and carbon to aluminum, and some still do currently. All the early carbon fiber frames were bonded tubes & lugs before monocoque construction took off.

My comment was about the uniqueness of bonding steel to aluminum, something I've never seen outside of Miyata. When I first read 6guns thread, I thought he might be mistaken, b/c who the hell glued steel tubes into an aluminum lug/bracket/joint? But he and the bike shops he consulted were 100% accurate.

quote:

Originally posted by DennisM:
The bottom bracket shell is almost certainly going to be steel, which means a half-decent frame builder could probably re-seat and braze the stays.

I thought the same at first, but check the catalog I linked above. It explains Miyata's Aluminum Pressurized Adhesive Bonding construction on pg 4 where Miyata proudly states, "...the tube or the lug will break before the glue-line will."

The BB shell is cast aluminum alloy. The seat & chainstays are chromoly steel.

quote:

Originally posted by 6guns:
Dennis, based on a magnet test, the bottom bracket is aluminum and the rear fork piece that popped out is steel.

quote:

Originally posted by iron chef:
I thought the same at first, but check the catalog I linked above. It explains Miyata's Aluminum Pressurized Adhesive Bonding construction on pg 4 where Miyata proudly states, "...the tube or the lug will break before the glue-line will."

Well... crap. That's a curve ball.

So the aluminum triangle also pretty much kills "I know... replace the BB shell with steel" because it'd just be moving the problem to the down tube - BB shell match.

I'd be interested to learn if there's a go-to trick for aluminum-to-aluminum repairs that might work, but you're likely correct about the issues with different metals.

Coincidentally, I just received this reply from the bike/frame shop where I'd sent my magnet test video:

"Hi Carl,

Thanks for sending the video. You are correct. The bottom bracket cluster (where the cranks attach) is aluminum, and unable to be safely welded to the steel chainstay.

Unless you can find someone comfortable with applying epoxy, that frame appears to be totalled.

If we can assist in any other way, let me know.

-Adam"

Damn. I really was hoping to salvage this bike as a second use bike and as someone had mentioned, sentimental reasons.

Is there room to drill and tap a hole top and bottom in the frame to secure the slide in tubing?

quote:

Originally posted by 41:
Is there room to drill and tap a hole top and bottom in the frame to secure the slide in tubing?

That's a good question. I could see using tiny self-drilling screws along with an epoxy to bond the joints.