# Can I purposefully dent/crimp a steel chain stay for tire clearance?



## KobayashiMaru (Apr 25, 2020)

I know it may sound absurd, but I think about all the hefty dents I've seen in steel frames that haven't taken a bike out of service, and I figure none of them were done on purpose. If you were to somehow put one in precisely the spot you needed it, would it be a bad thing?

I picked up a ten year old steel framed hybrid for next to nothing, and I've already got some 40mm tires (that measure 38mm) that I want to run on the bike, but for some odd reason, the gap between the tire and the chainstay on the non drive side is half that of the gap on the drive side with the 32mm tires on the bike now. When I swapped the wheel with the tire I want to run onto the bike, the bigger tire rubbed on the left side (in one spot... more on that in a minute). I just need a few more milimeters, I really don't want to get another tire to fit.

It's possible a remounting of the tire could solve the problem, since it seemed there was a bulge in that spot on the left side. Most of the tire ran free of the chainstay, but that one section rubbed hard. (Yes, both wheels are true, at least as well as I can determine without a truing stand.)

Even if a remount would bring it back in line with the rest of the tire, there is literally 1-2mm of clearance on the left side for the rest of the bigger tire that doesn't rub. Any sort of muck on the tire and I'll be digging into the paint and steel.


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## Nat (Dec 30, 2003)

I hereby grant you permission to purposely dent your own bike!


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## KobayashiMaru (Apr 25, 2020)

Nice! I like your wit.

I've floated around the internet a bit since posting this question and it seems it's a common practice with a vise, a C-clamp, or some vise grips. Hollow out a block of wood by drilling through it, then cut it in half to use as a backer for the side you don't want to dent. Use something like a golf putter head, a ball bearing, a rod of sorts, or a deep well socket to make the dent, align everything where you want the dent and then squeeze.

I'll give it a shot.


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## Sparticus (Dec 28, 1999)

KobayashiMaru said:


> Nice! I like your wit.
> 
> I've floated around the internet a bit since posting this question and it seems it's a common practice with a vise, a C-clamp, or some vise grips. Hollow out a block of wood by drilling through it, then cut it in half to use as a backer for the side you don't want to dent. Use something like a golf putter head, a ball bearing, a rod of sorts, or a deep well socket to make the dent, align everything where you want the dent and then squeeze.
> 
> I'll give it a shot.


Do it. I wanted a stealth dropper in my '13 steel Kona Honzo so I asked my buddy (who builds frames) what he thought and he said, "Just do it!" So I did. This was a couple years ago and the frame remains intact. And I hammer that thing mercilessly. Steel is... real. It'll take it.
=sParty


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## Varaxis (Mar 16, 2010)

Depends if it were heat-treated or not. Non-heat treated 4130 is more ductile than heat-treated 4130. Heat-treatment makes the 4130 generally stronger, but more likely to snap/crack than bend/dent.


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## KingOfOrd (Feb 19, 2005)

Wasn’t there a guy around here back in the day that put dents in his downhill rig for aerodynamics? Whatever happened to that dude?


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## mikesee (Aug 25, 2003)

I did this once in a light-gauge steel frame. Had to be _so_ delicate as I applied pressure. Could not believe how easy it was to make the impression needed.


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## Clapped_Out_46 (Jan 6, 2019)

Hey man, 
I have quite a bit of metal fabrication background (automotive), and my roommate and his dad have built ~16 steel frames, including everything from road bikes to mountain to tandem (now I have some minor credibility lol).
As Varaxis stated above, A heat treatment would make the bike more brittle, although fewer of the steel frames have been heat treated than not. If it is a brazed frame I wouldn't worry about it at all as it is only after welding that a frame is typically treated (to counteract the change the metal goes through from the heat of the weld.)

Anyways, as long as you don't really destroy the cross-section of the CS tube there should be no problems with denting it for some more clearance. (I wouldn't dent more than 30%of the total depth as a rough estimate) We actually did the same thing on my Roommate's Homemade Surly Krampus Replica to help clear 29x3.0 tires that buzzed on hard turns - adding about a 2mm dent by placing a ball peen with the round part facing the area in question and whacking it with another hammer. 

The other solution I could see is to re-dish the rim and adjust your brakes appropriately which would allow you to put a smaller dent in the CS in question or even 2 smaller dents in both.

Before doing any of this though, I would try and reseat the tire on the rim, as it seems like that is the primary concern if your wheel is centered in the frame.


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## KobayashiMaru (Apr 25, 2020)

I forgot to mention it's Reynolds 520 steel, but that's just for the main triangle. The stays are "double tapered cromo" according to the info in the catalog from that year. 2010 bicycle, so probably tig welded but I could be wrong. At least I know it's not a lugged frame. Does that change things? I don't want a massive crimp, and I want to go really slow and delicate if I do it. I've heard of people doing this with aluminum frames, so surely a small crimp won't put a steel tube in the danger zone.

As far as the wheel being centered in the frame, it's really puzzling to me. There is obviously less room on the left side (non drive) than there is on the right and I keep thinking I've got the wheel crooked in the dropouts. I keep trying to put it in a different way, but it doesn't make a difference. It rolls true in the frame and the disc brake doesn't drag, so maybe it was built wonky to start with. I don't know anything about frame building, but it seems like you would build a bike with equal space between the chainstays. The seat stays have equal space, or at least they appear that way.

I'll absolutely try to remount the tire, and then try it on a different wheel if that doesn't work. There are a few mm difference in internal widths of the wheels I have, so maybe a wider one will take the light bulb shape out of the tire and straighten up the sidewall just enough to clear the stay. I don't see myself getting into much mud and muck with this bike, so if I can get the tire to just not rub I'll be ok with it, but man... I really want a bit more clearance and am so tempted to crimp the stay just for the experience. We form relationships with our bikes, and this would be a really cool way to start it off with this one.


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## Clapped_Out_46 (Jan 6, 2019)

Didn't realize it was a disk frame, so that makes a re-dish easier if you decide to go that route since you won't have to fiddle with recentering brakes. Sounds like being crooked in the dropouts isn't a problem either, so I wouldn't be concerned about that.

You are correct on wanting to build bikes with equal spacing, but it typically ends up being close, but not quite the same, especially when considering necessary clearance of external things like chainrings and cranks. The frames are usually built oversized on both sides (not necessarily proportionally) to clear oem spec tires, which will make manufacturing/building easier. 
You are correct on possible new wheels which will take out some of the ballooning of the tire, but it doesn't seem like that will solve the problem.

I think modifying a bike is great and you're right about forming a relationship; I just filed down part of my alloy frame to treat it to a new, coil shock.

In my best opinion, 'send it' comes to mind, so I'll put it in better terms; the worst that can happen is you have a dent in your steel frame, which isn't a big deal anyways. I would also add that it may be wise to give yourself slightly more room than less, so you will have clearance for tire deflection under hard cornering situations. 
Good Luck!


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## KobayashiMaru (Apr 25, 2020)

Clapped_Out_46 said:


> I would also add that it may be wise to give yourself slightly more room than less, so you will have clearance for tire deflection under hard cornering situations.


Very good advice I hadn't thought of yet.


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## EABiker (Jun 24, 2004)

Train Wreck said:


> Wasn't there a guy around here back in the day that put dents in his downhill rig for aerodynamics? Whatever happened to that dude?


He put too many dents in it, took it off of a jump, and never landed.


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## KobayashiMaru (Apr 25, 2020)

Well, I put the tire I want on the rim I want to run, and what was a 38mm wide tire blossomed up to a 41mm tire.

I crimped the non drive chain stay easily enough and will have to wait until I can pick up a crank puller to get at the drive side that now needs to be crimped as well.

What is really strange now is the issue mounting my chosen wheel. I had been mounting another wheel with 135mm spacing into the frame to check for tire clearance because it already had the tire I wanted to use on it, and that one took a bit of wiggling getting into the dropouts, but the other wheel took way too much. They both have 135mm spacing, and I just couldn't make sense of why one was more difficult than the other, so I spread the calipers between the dropouts and the bike has 130mm spacing. (Maybe the older wheel is more worn where it mates against a frame and gets in easier... Who knows?)

Anyway, this is a 2010 frame... how does it have 130mm spacing? It _is_ a hybrid, but it was spec'd from the manufacturer with an XT rear derailleur, an 11-32 9 speed cassette and a flat bar with trigger shifters. You'd think it would have 135mm dropouts.

Oh well. Now I have to cold set the frame to get it to (more easily) take the other wheel. Maybe it will spread the chainstays an extra millimeter near the tires.


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## Arm&Hammer (Dec 19, 2020)

Most hybrids back then were 130mm with a road/hybrid wheel. Not a mountain bike wheel.


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## D. Inoobinati (Aug 28, 2020)

I had this problem on an old aluminum hardtail. I took a belt sander to the tire. 20 minutes later, problem fixed.


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