titanium chainstay clearance

[Andres Muro]

can you add chainstay clearance to a titanium frame. I currently have 2mm between a 23mm tire and the chainstay on 2002 merlin extralight compact.

[riendeau...@gmail.com]

consider a 650B conversion.  Your current setup is 622 mm diameter and 311mm from the axle.   650B would be 584 diameter and 292 mm from the axle.  If you mark that point you can measure how much clearance you might have.   That might get you to a 35mm tire.  cf. Confrerie des 650B pneus at XXCycle.  622+46=668;  584+70= 654.   If you can fit 38s at the 650b mark your wheel diameter would be about 660.  Your bottom bracket would be lower by the equivalent of  one half of four 14 gauge spoke widths.

[Cliff McLeroy]

I agree on the 650B conversion. Continental has 28 and 32 sizes. You basically need to measure back 19  mm and see what the width is. Looking at your picture you might have similar clearance for a 28. Of course this will also drop your BB height by roughly 12-15 mm. So if you run 175 cranks, standard pedals, or pedal through corners a lot, I wouldn't recommend it.

On Monday, August 14, 2023 at 6:01:51 AM UTC-4 Andres Muro wrote:

[Andy Walker]

are the original brakes rim brakes? You might have to consider moving to canti posts or some type of disc to use 650b wheels.

[Mark Bulgier]

Andy Walker wrote: "You might have to consider moving to canti posts or some type of disc to use 650b wheels."

You can consider it, but I wouldn't, you certainly don't "have to".  Longer-reach side-pulls, dual-pivots or centerpulls are all choices that people often use in converting 700c bikes to 650b.  It's a whole cottage industry, been done thousands of times from what I've seen on the 'net.  I've done a few that way myself.  Tektro R559 long-reach dual-pivots are a popular choice.

Does Dave Levy of Ti Cycles still do his potato chip mod?  Dave's on this list so maybe he'll chime in.  It's still listed on his website here.

Retrofit - Potato Chip — TI CYCLES FABRICATION / www.ticycles.com

It won't be cheap, but I trust his work 100% — if he says the result is stiff and strong and reliable, you can bet it is. (For this mod, he puts more metal back in than he takes out.)  I worked for him for a few years in the '90s so maybe I'm biased, but I've seen his work up close, and it's impeccable.

That Merlin is such a dumb design.  Sorry dude, (talking to Andre the OP) maybe I shouldn't insult your ride, but inadequate clearance even with a 23 mm tire is LAME.  They could have made it so much more useful with a few easy tweaks of the design. As it stands, in my opinion the only way to make that clearance not a total deal-breaker is to do both the potato chip mod and the 650b conversion. With the potato chips put in the right place for the 650 tire, of course.  Unless you can get at least a 38 mm tire, the BB height is going to end up very low.  Maybe you're OK with that.  But with the Grand Bois Écureuil and other wide 650b tires available that are so light and fast, there's no reason not to go for it if there's any hope of getting to 38 mm.  Me, I shoot for 42 to 48 mm, but I'm old and fat.

BTW for anyone who thinks ordering from a Japanese website is difficult, let me put your mind at ease.  I've ordered from Gand Bois several times and it was painless.  Just use Chrome or other browser with good auto-translate (I use Brave).  You do have to go through checkout and then wait for an email from them with your total including shipping.  But the email comes fast-ish — not immediate, probably next day.  It's in perfect (and very polite) English, and the total cost with shipping is much less than you'd  pay to a Stateside importer.

I've also been impressed with Pacenti 38 mm tires, but I have heard that at some point they made the rubber thicker.  The older ones I've used were extremely light and fast-rolling but later production (now called Panaracer, not Pacenti anymore) may be a bit heavier/slower, and more durable.  The GB Écureuil is even lighter than the old Pacenti, so don't expect a lot of miles out of them.  I think of them as "race day" tires, or for light riders.  But there are lots of choices for more durable 650b tires too.  They're not going away any time soon.

Oh and one more plug, for Hahn Rossman's tire width checking tool.  Lets you quickly find out what's the widest tire your frame will fit, in 26", 650b and 700c.  Laser cut out of plastic, ships flat, you just add a dummy axle, which can be a piece of all-thread with some hardware store nuts.

Tire fit gauge — Rossman Cycles This is a simple and inexpensive tool made from laser cut acrylic to answer the age old will this tire/wheel size fit my frame. It’s also useful for framebuilders as a sanity check mid build especially when combined with the chainring gauge. Comes with a variety of sizes (23,34,38,42,48,54) and slo www.rossmancycles.com

Yes you can do this with a tape measure and calipers and some arithmetic, but the Rossman gauge pays for itself in convenience after the first use, in my opinion.  I liked my v1 so much I ordered a v2 when they came out.  I have no connection with Rossman, just a happy customer.

[Andres Muro]

Thanks Mark,  et al, 

I agree that the design of the frame is problematic. I am riding it with 700x23c right now and its ok. But it makes me a little nervous that if my wheel goes out of true it will start rubbing the chainstays. I don't think I will convert to 650B. I really like the way the frame rides as is with a skinny tire. I am thinking of the potato chip. It will allow me to to use a modern rim with a wider profile and 700x 25c tires. 

Andres

[njh...@gmail.com]

On Sunday, 20 August 2023 at 4:12:20 am UTC+8 Andy Walker wrote:

are the original brakes rim brakes? You might have to consider moving to canti posts or some type of disc to use 650b wheels.

Longer reach rim brakes will work fine. I did exactly this when I converted my old Litespeed race bike to 650b so that I could fit fatter tyres. I went from maxing out at 700x25 to just being able to fit 650Bx32, and I swapped the brake calipers to Tektro 556 long reach dual pivot. The only problem was that with a BB drop of 76mm, the BB was now a bit low, and I had to learn not to pedal through corners at any speed. But I did ride the bike setup like that for several years before I bought a frame intended for 650b wheels.

Nick Payne

[Andres Muro]

problem with 650b wheels is that they mostly come with 135mm spacing and are for disk brakes. I would have to spend upwards of 400 to have someone build wheels with 130mm spaced hubs and for rim brakes. If I am going to spend that much money, I'd rather do the potato chip retrofit conversion. I am not looking for a bike with super wide tires. I just want reasonable clearance on the chainstays. 

[riendeau...@gmail.com]

Off the shelf wheels, yes.  Wheels that come to you in pieces (rims, spokes, nipples, hubs) no problem.