noglider 

I have a ~1996 Lemond titanium frame, made for narrow 700c wheels. I have put 650b wheels on it with 38mm tires. I like the way it rides. The tire clearance is very tight, and if I'm not careful, or if the rear wheel goes out of true, the tire rubs the frame. Does it make sense to have a frame builder put some dimples in the chainstays? Would someone even be willing to do this? I don't know much about titanium except that it is tricky to work with.

If this is not a sensible plan, I will probably put 700c wheels back on it and see how I like the harsher ride. Then I might sell the bike and replace it with something that can take wider tires.

HillRider

Back in 1996 road bike designers certainly weren't thinking about wider tires than 700x23 or so. My '96 Litespeed also won't take tires wider than 23. For that matter my 2006 Litespeed won't either. Road frames for wide tires are a recent development.

I'd be very leery about dimpling the chainstays. The tubing is thin and reducing the width could be a failure point. Chainstays designed with clearance dimples for wide tires have extra width and thickness to retain the needed strength. Ask a frame builder but I'd be surprised if he/she thought it was a good idea.

Moe Zhoost

I've added dimples to steel frames, which is fairly easy and low drama. I'm not sure that I'd try it with Ti in fear of causing some work hardening. How much more clearance do you need? If not much, perhaps flattening the chainstays a bit would get you just enough (2-3mm). Also not sure that dimpling or flattening Ti would be easy on a finished frame.

Best to consult a framebuilder who works with Ti. Good luck.

masi61

Dimpling the seat stay tubes with titanium sounds complicated. I'm curious how your Lemond titanium rides. I thought titanium gave a plush ride. I hope you are not running 23 mm Gatorskins with 120 psi or something like that.

In my mind, titanium bikes have a really great, non harsh built in bit of compliance that is similar to steel. It can be further tuned with tubes and tires and also with seatposts and saddles.

Can you run 25's on your bike? If so, why not get some supple 25's (high thread count "open tubular" type from Veloflex or Challenge come to mind) with some latex inner tubes and the run them down a bit on the pressure, as low as you care to go where they are still fast and don't squiggle around while cornering.

rowebr

I've put many thousands of problem-free miles, including plenty of gravel and dirt road riding, on my 650B Bianchi conversion which just barely fits 38mm tires between the chainstays. As best I can measure the clearance is about 2mm on each side. So if your wheels are well built, and you ride within the bounds of what the wheels and the bike are capable of, perhaps the tight clearance is not a problem. I even did a gravel race that had long sections of washboard and cratered dirt roads and tracks and the bike performed just fine.

On long rides far from home I did carry a fiber-fix spoke because one broken spoke would definitely make the tire rub on the chainstay.

ThermionicScott 

+1 to @rowebr's point. Even after dimpling my bike, the rear clearance for 38mm tires has never been what I'd call "generous" and it has yet to be a problem. (In fact, those tires have puffed up to around 40mm and eaten up some of the extra clearance I gained.) I'd like to think my wheel-building skills are above average, but I might just be lucky.

@masi61 has a good suggestion if a bike is stuck with skinnies. My 700C bikes just collect dust anymore, but I might try some premium high-tpi tires someday, maybe with wider rims...

squirtdad

Framebuilder Forum might have some additional info. IIRC titanium is a lot different than steel and things like cold setting and dimpling that are non-issues with steel are a problem with titanium.

Andrew R Stewart 

I remember a thread on this in one of the various forums I have hung in, maybe within the last couple of years. I can't find it quickly but recall that the responses were don't do it unless you know what's going on. (Or if you have to ask you don't know enough). The alloy, it's thermal treatment, the wall thickness, the radius of the mandrel, the radius of the dimple edges (and likely more) were mentioned.

Ti is a wonderful material but it can and does corrode, crack, dent and fail. Andy

noglider 

Thanks, everyone. I pretty much expected these answers. I might pose the question in framebuilders. I suspect they'll say don't do it. I'll see how it goes with these wheels, and I'll carry a spoke wrench.

I rode 87 miles on the bike on Sunday, and I was fresher than I've ever been on such a long ride. Jan Heine might well be right that a softer ride reduces fatigue. Long rides normally tire out my lower back and shoulders more than my legs and butt. They were tired but not killing me.

noglider 

There are many factors that contribute to how a bike rides, and material is not the major one, according to my understanding. This bike is fairly harsh, but maybe it's because it's my shortest-wheelbase bike. There's no way to know for sure. I do have a pair of 700x28 tires which measure 27mm, and they fit, barely. I tried other 28mm tires, but they measured 29mm, and there was a 1mm clearance behind the seat tube. That made me nervous, so I moved those tires to my McLean. But the Lemond rides great with the 650x38 tires. I ride over bumps and ask myself if I just rode over them. It's quite nice.

big john

Titanium, like steel, can ride extremely harsh or soft and smooth depending on certain factors.

J.Higgins 

Tom, from my professional experience working with titanium, I can attest that it can act like a natural spring. A simple attempt at dimpling the stay may end up in disaster, or at the very least, a half-dimple, which may be better than no dimple. I made custom knives for a while, and the liners on most of my folders were titanium - usually .080 6AL4V. I'd typically have a chore to even bend the spring part of the liner lock out of Ti. All of this would lead me to suggest that you get a bike that runs 650B or maybe even have one made for you! Now that would be the bombdiggity!

bikemig 

Tom, I like the way a bike rides with fat, high quality tires as well. I use a '93 Bridgestone XO 2 for multi-day events as well as gravel rides. It's a road bike built around 26 inch wheels and I ride it with 26 x 1.75 inch tires. It's a comfortable bike for a long day in a saddle. You may be better off selling that bike and getting a bike that can be converted to 650b.

ljsense

I've just been reading a lot about titanium, and came across many frame builders who describe cold working ti tubes into various shapes. Other industries also describe bending and shaping the metal cold.

It's springier than steel -- so it tends to bounce back from the bending force applied. But slightly squashing a round tube into more of an oval shape isn't some black art that will only work with steel. Bending a titanium tube a bit isn't going to turn it into glass. If you hang out in a bike shop service area long enough, you'll see lots of people riding dented titanium frames that haven't failed at all.

If you're feeling adventurous, you could do it yourself with a good vise or clamp. Lock a spare hub in the rear dropouts. Spread the load well on the outside of the chainstay, and concentrate the opposite load into about a 1 cm patch where the tire goes on the inside. If that seems too tame or boring, just take a dull punch where you want to make the dimple and strike it well.

ThermionicScott 

It's too bad bike tires can't be made much taller without adding to the width (or adding stiffness). The benefits we ascribe to "wide" tires are really attributable to their taller sidewalls that have more distance to compress for comfort.

J.Higgins 

That's a pretty interesting topic all on its own, Scott! I wonder how you could make a taller tire that doesn't flex sideways while cornering?

J.Higgins 

Or get a Troll. My Troll is pretty darn comfy.

Sy Reene

What would be so different just switching to 35mm tires?