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Bike Ninja
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Discussion Starter · #1 ·
I bought a used touring bike that I plan to commute on. I want to use these big wide tires but am running into rear tire chainstay clearance issues. Tires are a little bit wide, and though they actually do have 1mm clearance from the chainstay, the side of the tire will rub if the wheel is even slightly out of true. I definitely need a bit more clearance and I know that to get that clearance I need to form dimples on the inside of the chainstays. Not too sure how to do this, and there isn't much documentation on the web. Definitely will take the bike in to a shop though as I do not want to ruin a perfectly good frame. Here is a picture of what I'm talking about. Note the lower right hand picture is the dimples that I'd like to create. Andy thoughts / ideas on how to form these dimples let me know.



Looks like the tire is mounted on backwards...doh
 

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I'd say your chance od success is roughly equal to your chance of ruining your frame. I'd simply use a slightly smaller tire and live with it.
 

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Escorted from the White House
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Another possibility is to do a 650B conversion... run smaller-diameter wheels with fat tires. This will improve chainstay clearance a bit, as the smaller diamater wheel puts the tire a bit further away from the narrowest part of the chainstays.

The diff wouldn't be dramatic, though- maybe 4 or 5mm more total chainstay clearance, or like 2mm on each side of the tire.

You can't do this if you're running cantilever brakes (unless you have some framebuilder guy move the brake bosses for you, which I doubt is cheap), and even with sidepull brakes you'll need a new set of 'long reach' sidepulls (rivbike.com sells these).

And, oh yeah, the wheels would run you some dough too (rivbike also sells some $200-250 650B wheelsets). Might make sense if you've always wanted to upgrade there (smaller-diameter wheels will spin up faster and be lighter, all else being equal), but if you're looking to not spend a significant amt of $$$, then I'd go with Cyclust and say run a slightly smaller tire and live with it.
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Bike Ninja
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Discussion Starter · #4 ·
Nah, don't want to go with smaller wheels. That just makes things more complicated. Dimples is the key. If you look at the lower right picture that frame has dimples specifically for this purposes. It's just a matter of creating two dimples. I'm sure if I just take it to a builder they could do the mod for $30 and make sure alignment stays in tact. It's a steel frame BTW.

This is what little info I've found on this:

http://www.frameforum.org/forum2/index.php?showtopic=1866

http://www.velocipedesalon.com/forum/f2/framebuilders-q-diy-chainstay-crimp-8185.html
 

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Those "dimples" you see on some frames weren't formed by some frame builder or bike shop bashing the tubes with a hammer after the frame was built. The tubes were made that way by the tubing manufacturer, or the shaping was done by a builder before the frame was welded or brazed together, Trying to re-shape the tubes on an assembled frame will likely damage them, and will almost certainly distort the alignment of the frame. You're barking up the wrong tree, IMHO.
 

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Militant commuter
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A competent builder could probably add the dimples...which could be relatively easy or could require new chainstays altogether. Even the easy way, I'd be damn surprised if it was a $30 process. Sounds like slightly narrower tires might be a more economical (and logical) solution.
 

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la dolce vita
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Cut a mm out of each dropout. It will move the tire back to give you the space you desire.
 

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Diesel Engine
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SilentAssassin said:
Nah, don't want to go with smaller wheels. That just makes things more complicated. Dimples is the key. If you look at the lower right picture that frame has dimples specifically for this purposes. It's just a matter of creating two dimples. I'm sure if I just take it to a builder they could do the mod for $30 and make sure alignment stays in tact. It's a steel frame BTW.

This is what little info I've found on this:

http://www.frameforum.org/forum2/index.php?showtopic=1866

http://www.velocipedesalon.com/forum/f2/framebuilders-q-diy-chainstay-crimp-8185.html
Plus what the painter would charge to repaint the modified area as the paint would at least crack in that area. There's really no good way to do this by tweaking the frame IMO. Best case is that the bashing in of the chainstay (which is effectively what it is) weakens it structutally in an area where a lot of torque is transmitted.

Narrower tires is the answer to the question.
 

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RoadBikeRider
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cyclust said:
I'd say your chance od success is roughly equal to your chance of ruining your frame. I'd simply use a slightly smaller tire and live with it.

+1...I say go with what you have, get a narrower tire for the rear and keep the extra tire as a spare for up front.
 

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Bike Ninja
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Discussion Starter · #10 ·
Mike Prince said:
Plus what the painter would charge to repaint the modified area as the paint would at least crack in that area. There's really no good way to do this by tweaking the frame IMO. Best case is that the bashing in of the chainstay (which is effectively what it is) weakens it structutally in an area where a lot of torque is transmitted.

Narrower tires is the answer to the question.
People add dimples to get clearance all the time after the bike has been built, usually from what I've read, they would do it to get crank clearance.

Also I don't care about the paint cracking. I'd probably just put touch up paint over the area. This is a commuter bike that will see a lot of miles, and it was also bought used.

I've also read about people taking their bikes to a frame builder to have this done.
 

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Diesel Engine
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SilentAssassin said:
People add dimples to get clearance all the time after the bike has been built, usually from what I've read, they would do it to get crank clearance.

Also I don't care about the paint cracking. I'd probably just put touch up paint over the area. This is a commuter bike that will see a lot of miles, and it was also bought used.

I've also read about people taking their bikes to a frame builder to have this done.
Have you actually talked to a framebuilder about it or just read anecdotal stories online? There's a few folks on here who build, I would shoot Ed ("Nessism") a PM and get his advice before I took any of the random advice (including mine) that you have received in this thread,
 

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SilentAssassin said:
People add dimples to get clearance all the time after the bike has been built, usually from what I've read, they would do it to get crank clearance.

I've also read about people taking their bikes to a frame builder to have this done.
Didn't know that. Good luck. Please let us know how it works out.
 

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Bike Ninja
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Discussion Starter · #14 ·
Mike Prince said:
Have you actually talked to a framebuilder about it or just read anecdotal stories online? There's a few folks on here who build, I would shoot Ed ("Nessism") a PM and get his advice before I took any of the random advice (including mine) that you have received in this thread,
Thanks, I'll shoot him a PM.
 

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You didn't say what tire width you were trying to use, but if there's any downside room in tire width, it's a no brainer. Use a tire that fits, and leave the frame alone.

As someone else pointed out chainstay crimping is done prior to building, and while it isn't hard to deepen an existing crimp, adding one to a non crimped oval tube isn't nearly as easy.

You might find a builder to take this on, but it won't be cheap. so if you're dead set on these wide tires, you'd be better off selling this frame and buying one more suited to your needs.
 

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Bike Ninja
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Discussion Starter · #18 ·
I'm asking around. Not going to pay an arm and a leg to have this done obviously. I know an experienced frame builder could probably do this real quickly with the right tools. Tire size I want to use is in the picture: it's a 700x45 tire.
 

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Bike Ninja
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Discussion Starter · #19 ·
FBinNY said:
You didn't say what tire width you were trying to use, but if there's any downside room in tire width, it's a no brainer. Use a tire that fits, and leave the frame alone.

As someone else pointed out chainstay crimping is done prior to building, and while it isn't hard to deepen an existing crimp, adding one to a non crimped oval tube isn't nearly as easy.

You might find a builder to take this on, but it won't be cheap. so if you're dead set on these wide tires, you'd be better off selling this frame and buying one more suited to your needs.
People seem to use a c-clamp, and a wood block to protect the other side of the frame when they do it.
 

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SilentAssassin said:
People seem to use a c-clamp, and a wood block to protect the other side of the frame when they do it.
Little late to the party, but dimpling (we called it "thumping" a frame) was pretty common back in the day. When a rider wanted to try a huge chainring on the track and there was insufficient chainstay clearance, an educated thwack or two with plastic or wooden mallet would do the trick, with no problems other than a paint flake or two after the deed. Of course, bicycles weren't living room wall art back in those days.

However, this was in the days of stout steel tubing—long before there was EL and OS. My suggestion is to go ahead and dimple with with the clamp and wood if the tubing is traditional thick-walled steel like 4130 gas pipe or even something like Reynolds 500-series tubing. But if your frame is made to compete with aluminum- or carbon frames in terms of weight, I'd take the general advice given in this thread and not do it.
 
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