# chain stays with dimples for wide tires



## febikes (Jan 28, 2011)

Just about every production frame and many custom frames have dimples on the stays for enhanced tire clearance.

Does anyone know of a source for stays that come with factory shaped bending and dimpling?

I can run 2.2ish tires without dimples but for my next bike I would like to have ability to run 2.4" tires. So far I have built all my bikes with NOVA chainstays. The NOVA stays come pre bent but they do not have dimples. I will give them a call next week but since I am thinking about the issue now I figured it would be good to ask you guys what you are using.

One option is to purchase or make special vise jaws to dimple chain stays. I figure I can build my own but would prefer to just get some prefabricated jaws if they are available at a reasonable price. What I would like is a nice aluminum or steel implementation of the basic male/female vise jaw concept. I have seen a few examples of homemade wood ones similar to these photos stolen from Meriweather's blog. I am thinking of making a similar design but would prefer an aluminum or ideally stainless steel version for tool durability and dimpling accuracy. For wood I would guess a hardwood like oak would work. A few weeks ago I also saw a version built with the head of a hammer so that's also an option.



















What are your thoughts and what are you using in your shop?


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## G-reg (Jan 12, 2004)

That was me with the hammer/tubing block in a vice method. Low engineering content but it made some nice dimples in spendy prebent stays. The thread pitch on my randomly found in Grandpa's garage is pretty course so it was a bit of a game to apply the same amount of grunt to both stays. A vice with a finer pitch screw or a press would make it easier to apply equal force.


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## febikes (Jan 28, 2011)

G-reg said:


> That was me with the hammer/tubing block in a vice method. Low engineering content but it made some nice dimples in spendy prebent stays. The thread pitch on my randomly found in Grandpa's garage is pretty course so it was a bit of a game to apply the same amount of grunt to both stays. A vice with a finer pitch screw or a press would make it easier to apply equal force.


Another option might be to use a stop to limit how far the vise can close. This can be as simple as a solid chunk of steel that stops the vise from closing once the dimple has been fully formed. If I end up building my own vise jaws they will likely be similar to your hammer version but include another chunk of metal (or I I may use step blocks to control the maximum amount of vise closing).


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## TrailMaker (Sep 16, 2007)

What about cement to make your dies?

Some may laugh at that, but it is a classic way to make a stamping die set cheap. If you use the proper cement, they are very hard and pretty durable. The process is similar to making a plug (prototype part), then a mold from the plug, and then the part you want like you do with composites. It's an option if you want to carry it that far.

*Todwil*uses a pretty slick - if rather farmer-ish - set up for his 36rs. An iron weight welded to a post on a shop press that seems to work pretty well.

I have been thinking about the same thing, but further, some way to ovalize the entire BB end of the tube for clearance.


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## febikes (Jan 28, 2011)

It seems weird to me that the stays from NOVA come nicely bent but lack the dimple. Sure I like doing stuff in my own shop but in this case it seems like a factory operation would be better. 

Does anyone know of a supplier that has good pre-dimpled stays for 29ers with 340ish chainstay length?


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## unterhausen (Sep 28, 2008)

wood will work just fine, especially for the part that holds the stay. I noticed on the Engin cycles flickr that he uses wood with epoxy to make the stay fit perfectly.


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## kampgnar (Apr 13, 2007)

Dimpling a stay is one of the easier steps in building a frame. Placement, size, depth etc... is going to vary from frame to frame so a manufacturer putting a dimple in a discrete location seems illogical. 

I've used aluminum, oak and maple for dimpling. In all cases I didn't seek out a specific material and just used what was on hand. However, I avoided steel (stainless, carbon...) and kept to softish materials to avoid leaving impressions/scars on the tube.


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## mack_turtle (Jan 6, 2009)

Seeking advice on this topic:

I have a Traitor Crusade steel CX bike that I use for mixed terrain urban rides and gravel races. The smallest tire clearance is between the chainstays, where a 700c/ 35mm tubeless Gravelkings SK barely fits on a 21mm inside Arch EX rim. The inside of the chainstays are already mildly dimpled and, as you can see, the paint is worn off where tire/ dirt hits the frame sometimes.

I'd like to be able to run a 700c/ 40-42mm tire in there. I know it's a risk, but how can I "safely" deepens the dimples in this frame to allow a fatter tire? I have been taking notes on the wood/ epoxy/ aluminum- c-clamp/ vice options in similar discussions.


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## scottzg (Sep 27, 2006)

There aren't many mysteries when it comes to dimples, so i'm not sure what advice you're looking for.

-you want to use a soft-ish material to form the dimples. Wood works great, don't use plywood. I have redwood pucks cuz it was convenient.
-dimples take strength out of the stays. Usually not a big deal if you don't create stress risers.
-soft tubes with thick walls will be much more tolerant of kludged dimples. Or any dimples.
-the frame in your photos was designed without much consideration for big tires. Looks like a pretty budget-oriented frame? That's to your advantage.


If it were my project, i'd use a hole saw to drill a 2" hole in to moderately hard wood, making a hockey puck. I'd file down the edges of the hockey puck to match the dimples i want. I'd stick a hub or a dummy axle in the dropouts, and grease the stays where the massaging will happen. Then tap the hockey puck into gap. Go slow, and if a stress riser starts to manifest... stop. In your photos i'd be concerned about the CS bridge, and i might cut it out beforehand. 700x40 seems optimistic, based on the photos.

I've done this process twice, on steel production frames i've bought. Stuff i've built i take pride in modeling such that i don't manipulate the stays... which probably is a waste of my time... but good for ego.


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## mack_turtle (Jan 6, 2009)

Thanks scott. I understand that there’s no recognized, exact science way to go about this, so your experience with it is exactly that I was looking for.

The Traitor Crusade frame is the same as a Transition Rapture, made from decent “Founderland Seamless Race Double Butted Chromoly”. the bike retailed for $1300 as a single-speed. I bought it on closeout for $600 and soon replaced every stock part on it, except the brakes. So it’s not a cheap-o hunk of steel, but it’s not exactly “boutique.” I made it my own and I love the way it fits and handles, except for the limitations of smaller tires on some terrain.

my biggest fear is that if I hurt the frame, it would be difficult to find a replacement on a budget: singlespeed, steel, works with my existing parts, etc. If the risk of damaging the frame is high, I should leave it alone and just enjoy it as-is.

I started whittling the end of a 1x2 plank to the shape that would enlarge the existing dimple. My plan would be to create a concave shape for the outside of the chainstay and the “puck” on the inside and use a clamp to squeeze it bit by bit until I have widened the space for the tire. I'll use a dummy axle to keep the dropouts spacing consistent.

Good call on the chainstay bridge! I'll keep that in mind.

The current space is not enough for 35mm tires and mud, so if I can at least make some space so that the current tire does not get jammed up with a little muck, I’ll consider it successful. If I can fit something like a 40mm WTB Nano in there, that would be even better.


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