I have a 79-80 Stevenson Sport Tourer that when made was able to run 30 mm tires at most. When I had the bike repainted some years ago I had a new fork made that could accept wider tires. Unfortunately I did not think of modifying the rear triangle, which can realistically accept 32 mm at most. (35s fit but with minimal clearance at the chainstays). I'd like to use those 35mm tires, so here's the question: Will dimpling the chainstays damage the current paint or otherwise cause a problem that I need to consider before I approach a frame builder?

Thanks -

I have indented chainstays without damaging the paint, but other times the paint cracked and flaked off. Depends on paint chemistry, surface prep, painter skill and who knows what all else. So I'm sure we can't say, without just trying it. Sounds like you don't need much, just a little dimple?

Does Bill S. still work on bike frames? Maybe he wouldn't for just anyone, but would for one of his own? Corey Thompson might be another great choice, if he takes in this kind of work. His frames are droolworthy. Olympia area I believe.

Damage to the steel is possible but extremely unlikely in my experience, and repairable should the worst happen. I think paint is the only likely casualty

Would lightly heating the area help to make the paint more flexible? Is wood or lead used to dimple on a painted frame?

If it were me, I'd have the frame indented. If the paint cracks or breaks away, I would just touch it up. You don't have to be that perfect on the color match since this area will not be too prominent. That's just my take on it since I've touched up lots of bike since I like to keep original paint if I can.

Before you dimple the frame, check and make sure the brake stay won't be a problem. I'd like to put 35mm tires on one of my Colnagos and the problem is the brake stay. On another one, the chainstays are the problem.

Sachi- Indenting stays for tire or ring (or rotor too) clearance usually is NBD given some care and thought with minor expectations as the goal. But one can do some real "harm" too, hence the care and thought part. This topic has been discussed here and in other forums many times and I suspect there are gems of wisdom to be found if searched for.

Here's the dimpling tool I use most of the time I need dented stays.

Made with hand tools and files. I like the modular design approach for tooling as I often will find later I want a slightly different detail on the tool. In this case I wanted to change the shape of the indent.



So I made a second form and backing plate.


And here's the resulting indent shapes. Both on oval chain stays. The RH stay has the first, long and narrow form and the LH is from the second wider form.

Both times the amount of added clearance per stay indent was only a couple of MMs. The oval shape reduces the indent's actual effect, a round stay will show a greater amount of clearance added for the same indent depth. On the actual frame's stays I do a running judgement as to how deep I need to go balanced with how much stay cross section is lost. IMO having to indent so far to gain more than a couple of Mms per side is suggesting you have the wrong bike/set up. Andy

Andy, most impressive and beautiful tooling and an excellent Porter.

Thanks everyone for your helpful comments.