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mack_turtle

Steel frame modifications

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I have a cyclocross bike that has space for a 35mm tire in the back. It's a blast to ride everywhere, but it's extremely limited on anything other than the smoothest dirt because the rocks shred tires. I have had to walk home more than once for this reason. Lesson learned the hard way, and I mostly ride it on roads now.

This is a "budget" steel frame that went out of production four years ago, so I am not afraid of any reprocussions on the warranty that does not exist.

Short of buying a new frame, what would be involved in modifying the chainstays to take a 42mm+ tire? Who around here is equipped to do such a thing? Probably not worth the trouble, but I can't justify a new frame for such a petty concern.

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As a former frame builder, there were a few times were we used a wood form and a smaller tube (that had been cut in half long-ways) to crimp the stays in a vice.  We've never had one fail on us through later use.  YMMV though.  But if this is truly a budget frame and you want more clearance, I think you could easily crimp the stays.

Later, -CJB

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I was thinking about doing that. Might not get me to monster cross status, but if it makes room for a few extra millimeters, it's worth it.

The bike was cheap, but it seems to be nicely made and was purchased at a steep discount because it was NOS. I'd hate to damage it.

I looked up DIY chainstay dimpling, and it looks like it's not that hard.

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I'm going to be doing the same thing to my cruiser frame, just in reverse.  Needs to fit new, standard rear dropout spacing.  Steel is really forgiving to these kind of things.  I am the frankenbiker, so I have shoved 27.5x2.35 on a 26er mtb frame, and even 29x35mm onto the same frame.  I now turned an old school 29er voodoo frame into a monstercross with adding 2.2 Ikons and drop bars.  Old stuff is way more fun and more flexible than these new damn standards.

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35 minutes ago, Shinerider said:

Old stuff is way more fun and more flexible than these new damn standards.

I'll be expecting you to buy my Chris King 135mm wheel set soon. 

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Well, can they be bumped to 157mm superboost?  I might be interested (although, I now have to buy a new front axle since I lost mine!)

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41 minutes ago, Shinerider said:

I'm going to be doing the same thing to my cruiser frame, just in reverse.  Needs to fit new, standard rear dropout spacing.  Steel is really forgiving to these kind of things.  I am the frankenbiker, so I have shoved 27.5x2.35 on a 26er mtb frame, and even 29x35mm onto the same frame.  I now turned an old school 29er voodoo frame into a monstercross with adding 2.2 Ikons and drop bars.  Old stuff is way more fun and more flexible than these new damn standards.


Have you ever upgraded a boss-only frame to disc brakes?

I've looked at the various adapters available and read feedback. They seem legit, just wondered if you had any experience with them.

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2 hours ago, RidingAgain said:


Have you ever upgraded a boss-only frame to disc brakes?

I've looked at the various adapters available and read feedback. They seem legit, just wondered if you had any experience with them.

No experience with those.  I personally don't trust them.  Seems very backwoods jerryrig!  But, to each his own .  But, then again, I have ridden a basic, POS, 90's 26er cruiser modified with better wheels, tires, brakes, bmx bars out at WC.

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8 hours ago, Big_papa_nuts said:

650b?

I am considering that too. If I can find a 650b xc wheel with a narrow tire to borrow as an experiment, I would try it.

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I did it on a old Ibis Mojo. I removed the stay bridge and canti mounts and installed disc mounts. I ran 650 38's and had a flexy Ti fork. Really fun Frankenbike and for some stupid reason I sold it yrs ago. 

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I had something in mind more like cutting the chainstays at the BB and replacing the brace between them to widen it. If that costs significantly less than a frame, it sounds worthwhile. I'll look into dimpling the stays first. I can probably find a narrow 650b rim and tire even cheaper than that though. Gravel mullet?

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I have a set of 27.5 wheels you can borrow if necessary.  And maybe can find some 2.1 tires to fit on.  15mm front axle, bolton rear (don't ask)

Edited by Shinerider

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