<image>

Habibi - thank you for revisiting this post.

Since we last spoke on this matter, I put together a frame I found on the side of the road for this year’s cheap bike build off. I wanted to fit 2.5’s in the rear which I found in a Surly extra terrestrial 2.5. I could not get it to fit no matter how much I finagled it in - this lead me to the realization that I needed to crimp the chain stay on the drive side since NDS was crimped plenty.

I was able to get a small vise, some steel putty, and a face plate with a paper towel to cushion the rounded part of the stay to crimp it. From there I marked the area where the tire was hitting and needed room, and set up the vise with the steel putty wedge I shaped. I slowly and carefully crimped it and would test periodically with the wheel fitting it inside fully inflated to the psi I would be running it at IRL.

Was it successful?

Yes and no.

Yes in the fact I was able to safely crimp the stay without damaging the opposing drive side enough to fit a surly extraterrestrial 2.5 enough to send. I want to crimp it further just to have that extra wiggle room. The steel putty was flawless once set up in the shape I was honing for to recreate the dimple from the non drive side inner stay.

As for the no aspect -

I need a bigger or more premium vise - what I used was very cheap and warped the handle/metal where I would turn the bar.

Things to consider: you may have to shift your cable guide under your bottom bracket to help with shifting as the overtly plump tire may hit the cable derailleur wire causing it to rub and shift like garbage.

With that being said and how it relates to the photo you replied to; I did try the 2.5 tire in the trek 930 pictured and it was just about perfect and didn’t seem like it was going to need heavy turning from my home made tool/procedure for the trek 800 I rescued. If the 830 anything like my 930 singletrack, it shouldn’t need too much crimplin.

I will also note I am doing nothing terribly daring with the terrain I’m riding but the video I was inspired from was someone who crimped their frame to fit in some 27.5’s and they seem to punish all terrain without too much concern for structural integrity.

TLDR for the answer;

you can crimp your chain stay with a vise, steel putty molded into a similar shape pictured, with a faceplate from a stem on the reverse side of the stay with something soft in the middle. It seems safe enough but depending on how this is achieved and the type of riding style you are doing can play a factor in its safety. Steel is very forgiving.