How to tell if a frame is compatible with 650b wheels?
08-14-18, 04:42 PM
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How to tell if a frame is compatible with 650b wheels?
Hi, I hope folks don't mind answering one more question for me about wheels for a build I'm doing.
After some thought, I'd decided to invest and have some good 650b wheels made for my 58 cm 1981 Univega Specialissima frame, rather than the 700s I originally asked about.
I'm a bit concerned about brake reach though -- I'm building this to use for touring and I want to make sure I have some real stopping power. Without finding some spare 650bs to put in, how can I best measure the necessary brake reach on this frame? I'm thinking about putting an axel of some sort through the back than then measuring from it to the hole and doing some arithmetic. But given the risk of imprecision there I wonder if anyone else has any better ideas? Thanks
After some thought, I'd decided to invest and have some good 650b wheels made for my 58 cm 1981 Univega Specialissima frame, rather than the 700s I originally asked about.
I'm a bit concerned about brake reach though -- I'm building this to use for touring and I want to make sure I have some real stopping power. Without finding some spare 650bs to put in, how can I best measure the necessary brake reach on this frame? I'm thinking about putting an axel of some sort through the back than then measuring from it to the hole and doing some arithmetic. But given the risk of imprecision there I wonder if anyone else has any better ideas? Thanks
08-14-18, 05:03 PM
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08-14-18, 05:08 PM
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Welcome to the forum!
The gold standard, of course, is to do a test fit with the wheels and tires you want to run. The bit of information you're missing is what width of tire you're interested in running. I found a link from someone who gives all of the pertinent specs for your bike.
Google 650b conversion requirements and you'll find lots of information. Sheldon Brown has one of the older ones.
For brake reach, a little searching shows that the stock Dia-Compe New Gran Compe NGC450 that came stock on that model/year have a reach of 55mm. MAFAC RAIDs work quite well, and have a max reach of 80mm - nearly an inch more(25mm) than the ones that came stock on the bike. There's a 22mm radius difference between 27" and 650b, so those brakes should work on the conversion. Other brakes may work as well, the RAIDs are a slam dunk for clearance.
The only concern I would have would be the chainstay clearance if you were running 42mm tires (the most popular size for conversions, it would seem). The chainstay length is 43cm, I would guess that you've got the clearance. Pictures I've seen online of that frame show the chainstays are indented for wider clearance. Between the long chainstays and the indentations I'm pretty sure it'll work.
The gold standard, of course, is to do a test fit with the wheels and tires you want to run. The bit of information you're missing is what width of tire you're interested in running. I found a link from someone who gives all of the pertinent specs for your bike.
Google 650b conversion requirements and you'll find lots of information. Sheldon Brown has one of the older ones.
For brake reach, a little searching shows that the stock Dia-Compe New Gran Compe NGC450 that came stock on that model/year have a reach of 55mm. MAFAC RAIDs work quite well, and have a max reach of 80mm - nearly an inch more(25mm) than the ones that came stock on the bike. There's a 22mm radius difference between 27" and 650b, so those brakes should work on the conversion. Other brakes may work as well, the RAIDs are a slam dunk for clearance.
The only concern I would have would be the chainstay clearance if you were running 42mm tires (the most popular size for conversions, it would seem). The chainstay length is 43cm, I would guess that you've got the clearance. Pictures I've seen online of that frame show the chainstays are indented for wider clearance. Between the long chainstays and the indentations I'm pretty sure it'll work.
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If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
08-14-18, 06:49 PM
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Welcome to the forum!
The gold standard, of course, is to do a test fit with the wheels and tires you want to run. The bit of information you're missing is what width of tire you're interested in running. I found a link from someone who gives all of the pertinent specs for your bike.
Google 650b conversion requirements and you'll find lots of information. Sheldon Brown has one of the older ones.
For brake reach, a little searching shows that the stock Dia-Compe New Gran Compe NGC450 that came stock on that model/year have a reach of 55mm. MAFAC RAIDs work quite well, and have a max reach of 80mm - nearly an inch more(25mm) than the ones that came stock on the bike. There's a 22mm radius difference between 27" and 650b, so those brakes should work on the conversion. Other brakes may work as well, the RAIDs are a slam dunk for clearance.
The only concern I would have would be the chainstay clearance if you were running 42mm tires (the most popular size for conversions, it would seem). The chainstay length is 43cm, I would guess that you've got the clearance. Pictures I've seen online of that frame show the chainstays are indented for wider clearance. Between the long chainstays and the indentations I'm pretty sure it'll work.
The gold standard, of course, is to do a test fit with the wheels and tires you want to run. The bit of information you're missing is what width of tire you're interested in running. I found a link from someone who gives all of the pertinent specs for your bike.
Google 650b conversion requirements and you'll find lots of information. Sheldon Brown has one of the older ones.
For brake reach, a little searching shows that the stock Dia-Compe New Gran Compe NGC450 that came stock on that model/year have a reach of 55mm. MAFAC RAIDs work quite well, and have a max reach of 80mm - nearly an inch more(25mm) than the ones that came stock on the bike. There's a 22mm radius difference between 27" and 650b, so those brakes should work on the conversion. Other brakes may work as well, the RAIDs are a slam dunk for clearance.
The only concern I would have would be the chainstay clearance if you were running 42mm tires (the most popular size for conversions, it would seem). The chainstay length is 43cm, I would guess that you've got the clearance. Pictures I've seen online of that frame show the chainstays are indented for wider clearance. Between the long chainstays and the indentations I'm pretty sure it'll work.
That seems like it should work clearance-wise, right?
08-14-18, 07:14 PM
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Measure the length of the seat stay from the dropout to the mounting hole on the brake bridge. Subtract 292 from that. That will give you roughly the needed brake reach. Find a set of brakes with that brake reach length in the middle of the brakes adjustable range.
A 42mm 650 tire may fit, but if it runs on the wide side, while it may fit, clearance may be closer than you want. A 38 will leave 2mm more per side. But if you go to a 38, you'll likely find that you could have fit a 35mm 700 but spent a great deal of $ for those few mm.
Just my experience (x2).
Unless you are adding fenders, I'd try to be happy with 700c.
If you are near DC, I can lend you a set of VO 650s to test with.
Thanks! this is super helpful. I just took some measurements and it appears that at the end of the indent you mentioned (a point whose center is about 34cm from the center of the axle) the clearance narrows to 41 mm. At 33cm from the center of the axle though, it widens to 45 mm. At 31 cm it's at 50mm. (Note to anyone looking at this thread for guidance in the future: these aren't standard measurements for this frameset because it's been cold-set to 130mm OLD.)
That seems like it should work clearance-wise, right?
That seems like it should work clearance-wise, right?
Just my experience (x2).
Unless you are adding fenders, I'd try to be happy with 700c.
If you are near DC, I can lend you a set of VO 650s to test with.
Last edited by S28546; 08-15-18 at 05:01 AM. Reason: Correct subtraction factor for 584 vice 622 wheel
08-14-18, 09:02 PM
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Measure the length of the seat stay from the dropout to the mounting hole on the brake bridge. Subtract 311 from that. That will give you roughly the needed brake reach. Find a set of brakes with that brake reach length in the middle of the brakes adjustable range.
A 42mm 650 tire may fit, but if it runs on the wide side, while it may fit, clearance may be closer than you want. A 38 will leave 2mm more per side. But if you go to a 38, you'll likely find that you could have fit a 35mm 700 but spent a great deal of $ for those few mm.
Just my experience (x2).
Unless you are adding fenders, I'd try too be happy with 700c.
If you are near DC, I can lend you a set of VO 650s to test with.
A 42mm 650 tire may fit, but if it runs on the wide side, while it may fit, clearance may be closer than you want. A 38 will leave 2mm more per side. But if you go to a 38, you'll likely find that you could have fit a 35mm 700 but spent a great deal of $ for those few mm.
Just my experience (x2).
Unless you are adding fenders, I'd try too be happy with 700c.
If you are near DC, I can lend you a set of VO 650s to test with.
08-14-18, 10:03 PM
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bicybike, I made a math error and corrected my post. You've read it before the correction. Subtract 292 not 311.
08-15-18, 12:57 AM
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Found too easily: My latest acquisition (1973 Nishiki Semi-Pro) fits all that (and fenders someday too, if I wanna). Wheels, freewheel, derailleurs and crank I had in my parts bin, the rest of the bike was $120 after the PO stripped off the stuff I couldn't use. It's one of those old bikes built for 27" wheels + big rubber, so when you drop down to 700c you can get even bigger rubber. The brakes it came with have no problem reaching down to the smaller rim size. (Yeah, I haven't got the pads adjusted perfectly, yet. Those are the initial set-it-up-quick-and ride-it photos.)
You have clearance, Clarence.
Ready for gravel grinding!
Last edited by Lascauxcaveman; 08-15-18 at 10:21 AM.
08-15-18, 07:12 AM
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You'll be amazed at the number of people that will offer to meet up with you and let you test fit a set of 650b wheels with 42mm wide tires, find new riding buddies, and plug into a network of like minded bicyclists.
Words on this site are great, pictures are worth a thousand words, but meeting up in person and
Heck, you might even get invited to one of these.
__________________
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
08-20-18, 05:36 PM
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I've been holding off on tasting the 650b Kool-Aid because, well, I'm cheap. The best deals I can find for a decent pair of 650b wheels + tires is north of $300, and that's why I sorta/kinda started looking for a bike that would fit 700c x 38, since I have 700c wheelsets a-plenty, and my standard Paselas can be found in the 38mm size for $70/pair for folders.
Found too easily: My latest acquisition (1973 Nishiki Semi-Pro) fits all that (and fenders someday too, if I wanna). Wheels, freewheel, derailleurs and crank I had in my parts bin, the rest of the bike was $120 after the PO stripped off the stuff I couldn't use. It's one of those old bikes built for 27" wheels + big rubber, so when you drop down to 700c you can get even bigger rubber. The brakes it came with have no problem reaching down to the smaller rim size. (Yeah, I haven't got the pads adjusted perfectly, yet. Those are the initial set-it-up-quick-and ride-it photos.)
You have clearance, Clarence.
Ready for gravel grinding!
Found too easily: My latest acquisition (1973 Nishiki Semi-Pro) fits all that (and fenders someday too, if I wanna). Wheels, freewheel, derailleurs and crank I had in my parts bin, the rest of the bike was $120 after the PO stripped off the stuff I couldn't use. It's one of those old bikes built for 27" wheels + big rubber, so when you drop down to 700c you can get even bigger rubber. The brakes it came with have no problem reaching down to the smaller rim size. (Yeah, I haven't got the pads adjusted perfectly, yet. Those are the initial set-it-up-quick-and ride-it photos.)
You have clearance, Clarence.
Ready for gravel grinding!
08-20-18, 05:36 PM
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Suggestion: Add your location to your handle. Go to User CP > Edit your Details, scroll down, and put NYC in your location.
You'll be amazed at the number of people that will offer to meet up with you and let you test fit a set of 650b wheels with 42mm wide tires, find new riding buddies, and plug into a network of like minded bicyclists.
Words on this site are great, pictures are worth a thousand words, but meeting up in person and
Heck, you might even get invited to one of these.
You'll be amazed at the number of people that will offer to meet up with you and let you test fit a set of 650b wheels with 42mm wide tires, find new riding buddies, and plug into a network of like minded bicyclists.
Words on this site are great, pictures are worth a thousand words, but meeting up in person and
Heck, you might even get invited to one of these.
08-20-18, 06:25 PM
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Well, that didn't take long. Enjoy it!
I've been holding off on tasting the 650b Kool-Aid because, well, I'm cheap. The best deals I can find for a decent pair of 650b wheels + tires is north of $300, and that's why I sorta/kinda started looking for a bike that would fit 700c x 38, since I have 700c wheelsets a-plenty, and my standard Paselas can be found in the 38mm size for $70/pair for folders.
Found too easily: My latest acquisition (1973 Nishiki Semi-Pro) fits all that (and fenders someday too, if I wanna). Wheels, freewheel, derailleurs and crank I had in my parts bin, the rest of the bike was $120 after the PO stripped off the stuff I couldn't use. It's one of those old bikes built for 27" wheels + big rubber, so when you drop down to 700c you can get even bigger rubber. The brakes it came with have no problem reaching down to the smaller rim size. (Yeah, I haven't got the pads adjusted perfectly, yet. Those are the initial set-it-up-quick-and ride-it photos.)
You have clearance, Clarence.
Ready for gravel grinding!
Found too easily: My latest acquisition (1973 Nishiki Semi-Pro) fits all that (and fenders someday too, if I wanna). Wheels, freewheel, derailleurs and crank I had in my parts bin, the rest of the bike was $120 after the PO stripped off the stuff I couldn't use. It's one of those old bikes built for 27" wheels + big rubber, so when you drop down to 700c you can get even bigger rubber. The brakes it came with have no problem reaching down to the smaller rim size. (Yeah, I haven't got the pads adjusted perfectly, yet. Those are the initial set-it-up-quick-and ride-it photos.)
You have clearance, Clarence.
Ready for gravel grinding!
