dsaul

I noticed that frame has rocker dropouts, do you have them adjusted all the way back? It looks like you could get a few more millimeters per side from more dimpling, but not enough to get a 42 in there. If it were mine and I could find a way to fixture it on the mill, I would cut out a section of the stays with a hole saw and weld in a section of heavy walled tube. It could also be done without the hole saw, but would definitely take longer to get a nice fit for welding in the section of tube.

This is what I do to fit a 3" tire on a frame with a 73mm bottom bracket. Something similar would work on your frame with a smaller diameter section of tube welded into your existing stays. Finding someone willing to do it for a reasonable price is another matter.

mack_turtle

I have the rockers about half-way back, but I don't think that would help. the drivetrain is singlespeed, so I can't push the wheel back more with the current gearing. I tried a few other gearing combos and realized it's a moot point because the dimples in the frame are tapered in such a way that they the most clearance is available where the axle is closest to the bottom bracket. if I take the chain off and loosen the dropouts so the swing freely through their path, the clearance gets worse as I swing them back. that's counter-intuitive, but the chainstays were inexplicably welded at the bottom bracket so close together that there's more tire clearance because of the existing dimples than there is where the angle of the stays diverges. there was no apparent need for this design choice as there's an absurd amount of chainring clearance. weird.

The method you describe is what I was hoping someone could do: cut out a segment of the inside of the chainstays and weld a section of another tube. probably not cost-effective for someone with that kind of skill, but I was hoping to find someone local who could actually give me a quote.

at this point, the bike is becoming less and less fun for me, but I can't get something else. first world problems!

unterhausen

I think he would have to ship the bike. Not that long ago, you could get a frame across the country for $30, but that doesn't seem likely now. People do modifications for far cheaper than I think makes sense, so maybe it wouldn't cost that much.

David, when you draw up a rear triangle, do you just go measure the tire on a rim? I think I will have a problem finding a 650bx2.25" wheel/tire to measure. I usually just rely in bikecad, but I trust it for this size.

dsaul

I measure if I have the actual tire and wheel on hand. Otherwise, I find that the Bead Seat Diameter + 2x tire width in millimeters is pretty close for the diameter of the tire/wheel. For a 650b x 2.25" tire that would be 584 + (2 x 57.15) = 698.3mm. I divide that by 2 and get 349.15mm from the axle center to the peak of the tire.

guy153

Yes, especially on the inside of the CS that's really hard to reach

repechage

I did look it up reread the post, just the welds appeared sloppy, sell this and buy another used bike that has capacity.
here is the logic path- the bike has some value now- modify it and the value (assuming burnt paint as you are willing to tolerate, will be so much less)
if the frame cracks post modification- you are out. The appearance of the welds just does not exhibit good control of the welding.
A real gamble to modify and have a durable machine.
A broken frame in the future will render the frame value zero.
Then you will have been out the modification cost and need to buy a frame which you state you cannot wrangle.
fair enough, these are tough times.
Why stack the odds against yourself?

himespau 

I know you said a new frame isn't in the budget, but, before the pandamic-induced bike shortage, it was possible to get a mtb from the early 90's for not too much money. Throwing a riser stem and drop bars on one would get you a bike that could handle much wider tires (they'd be 26-er wheels with canti brakes, though) but you could get some semi-slicks or whatever you wanted but still have a road-like position. Not always the most attractive option, but a way to do it on the semi-cheap.

mack_turtle

the rear swinging dropouts on this frame are stripped out and replacement are no longer available. I checked: Traitor Cycles no longer exists and Transition (this frame is identical to the Rapture because the companies were related) does not have them anymore. the swinging dropouts are being held in place with a longer bolt and a locking nut now. this frame is already scrap metal to anyone who might want to buy it. I would not feel good about selling it. It'll go for $50 and a millstone of guilt around my neck for selling it in that condition.

your logic makes perfect sense, but the Budget Committee capped my budget for the year on bikes after I replaced a dead wheel on my mountain bike in the spring ($300) and replaced my dying brakes last month ($200).

yeah, I have been looking at old mountain bikes for a sort of "monster cross" conversion for a while now. bikes that would normally sell for $125 are now listed for $400 on Craigslist where I live. that would be a significant downgrade and require a lot of spending to get them to fit and handle with confidence, but at least it would be me on a tire size that does not suck. I have been scouring half a dozen classified sections of various places like it's a part-time job for months and nothing with a reasonable price tag comes up lately.

base2 

The biggest problem I see, is the cost. With enough money, you can do anything. What I gather is this is a single speed steel framed flat land city bike that is being retooled to jump on the latest trend (gravel) and surprise, surprise it is having difficulty.

Anyone who could do what you want is going to charge you so much more than a new frame costs it just wouldn't be worth it, either for them to do it, or for you to have it done. It's not a simple job by any means. To be done properly, we're talking a whole new rear triangle. That costs real money, more so since the builder is starting with a work already in process and has to eat the liability of others work & complications of their quality control decisions...and this is coming from a guy who has gleefully thrown good money after bad for some pretty outrageous projects.

Simply put. Tell your significant other that it costs more to modify this bike than it does to obtain a new frame.

Below is an old 1997 Trek mountain bike gravel bike conversion. The conversion cost for new bars, shifters, cables, housing, bartape was under $250...shifters being $175 of it. It currently has 559x47c mountain bike tires on it (pictured). But, Rene Hearse Naches Pass branded GravelKing tires cost the same $71 dollars as heavy wooden Schwalbe Marathon Supreme and ride with every bit of the glorious smoothness you would expect.

My point is, you can accomplish your goal, have a lot of freedom, and a much more capable machine at less than half the cost of your current frame alone if you are even the slightest bit resourceful.
All-terrain warbike by Richard Mozzarella, on Flickr

You may even simply re-tire your old mountain bike with https://www.renehersecycles.com/product-category/components/tires/26-inch/ and be money/capability/speed ahead of where you are now.
(Rene Herse tires are made by Panaracer & since you already have Gravelkink SK's you know how good they roll. Moreorless they are made on the same production line and essentially with very little difference, each brand gets every other size, unless you choose the "extralight" which is Rene Herse exclusively.)

mack_turtle

FWIW, it's a cyclocross bike that I've been using as a gravel bike, like many people do. otherwise, your advice is spot-on. I won the singlespeed 50K Castell Grind on this bike two years ago. (I was also the only person riding the 50k distance on a singlespeed that year.)I would LOVE to find an old bike that like. however, bikes like that rad conversion you shared are selling for $400+ right now and are in need of new chains and a lot of other stuff. making it survive the local terrain by switching to to tubeless and getting a singlespeed drivetrain to work poses another set of challenges. I worked in bike shops for several years so the mechanics of it are no problem, just the money. my wife understands this and her financial goals are elsewhere, so mine are too. I now have more money to play with but no bike industry discount, so I am basically in the same place.

base2 

In a genuine effort to be helpful: Would something like this work? Simply swap all the components over from your existing bike. New cables and you're done.

mack_turtle

yeah, I have been looking for something along those lines. no cables, just a headset most likely. I would need to check the geometry but my guess is it's too long. going off of ETT, I would need an XS for that to fit and I am 5'9".

I've tried a few chain tensioners and I can't think of which one I hated the least, which is why I choose bikes that are designed with singlespeeding in mind. an aluminum frame and fork sounds like it will ride harsh and I'll need a headset to fit in it. knowing me, I'll compromise with something like that and grow to hate it after three rides. it's good to know deals like that are out there, though.

StanSeven

Thread closed at OPs request