63rickert

If you have been running Michelin Protek switching to Compass or Almanzo will be a total revelation. The Challenge Almanzo is labeled as 700x33 but stretches enormously.

700x35 is a limit for easy to find 700 bikes. Approximately normal for older bikes.

One of the main reasons conversions to 650x38 has been popular is the available tires in that size were all really good tires. When your choices were Pacenti, Compass, or Grand Bois it was not possible to buy a slow tire.

If the possible switch is to 650x38 rather than 650x42 there is no reason not to remain with 700x35. The volume of air in a 700x35 is just about the same as volume of air in a 650x38. Then you have the simple fact that rolling resistance is inversely proportional to wheel diameter. The big wheel is faster. Jan Heine says that is not true but every cycling engineer from Archibald Sharp to David Gordon Wilson is on the other side and so is common sense.

It is a total mystery to me why people will spend real money and endless hours converting bikes to something they aren't rather than make a simple purchase of good tires.

bikemig 

I run the Michelin Protek tires on the Sekine as it is a commuter. I wanted a stout tire with a reflective stripe. I use different tires for bikes I ride long distances. If modding a bike to take 650b x 42c with cantilevers, you are opening up roads to travel on that you might not wish to ride on 700 x 35c tires. But I agree with your bottom line which is why make the switch to 650b if you can run a sufficiently large volume 700c tire which is why I was looking for a frame or bike that can take a 700 x 38c tire.

Lemond1985

If you need a 650b x 42 to traverse it, it doesn't sound like any "road" that I know of unless it's some sort of un-maintained jeep trail or fire road.

bikemig 

Yes, that's the point, I'd like to set up a vintage bike for gravel riding. I can get by on 32c. Heck I've ridden gravel on tubulars by letting some air out of the tires but there are all these nice high quality large volume tires coming out and I was thinking of setting up a vintage bike with 38c tires.

88Tempo

I like the idea of a vintage gravel bike too. The 650b conversion probably makes the most sense in my case. I don't have a bike in that tire size which sounds like justification to me.

They just held the 1st Fountain Roubiax yesterday and it runs near where I live. One of the categories is vintage which requires downtube shifters and one piece of wool clothing.

USAZorro

You have a fighting chance of finding brakes that will work if you change to 700c. That won't be the case with 650b.

Lemond1985

So you are saying cantilever brakes are a "must" for 650b setups?

bikemig 

Right a 27 inch to 700c wheel conversion is pretty straightforward which is why I'm thinking a 70s era bike originally set up for 27 inch wheels with decent clearance might take a 700 x 38c tire. But maybe not because 38c might be pushing the envelope for a lot of frames.

USAZorro

That depends on the width of the tires. Here's the concern though.

The original rims' BSD is 630mm 650Bs are 584. 1/2 of 630 is 315mm 1/2 of 584 is 292mm 315 - 292 = 23mm difference in brake pad position from where the brakes were initially set. You may be able to find brakes with sufficient reach, but that would be something to determine before making a leap to 650B.

Many bicycles that have space for 38mm tires are designed for that, and have their brake bridges positioned so that there is also space for mudguards. Many of these bicycles come with long reach brakes, and while there's often room to adjust for 700c wheels (622mm BSD - 311mm radius), it is rare that there will be another 19 mm of reach. You might find something that works, but I think it is more likely to find a frame that fits 700c x 38mm tires.

Alternatives for 650B would be disc brakes (which poses even greater challenges, and I would not recommend), using a dropper bolt arrangement, or adding cantilever brake posts. I have no experience using dropper bolts, and have no idea if they also present challenges.

noglider 

The sluggishness is mostly an illusion. We have long believed that narrow tires are faster, and they are not. But narrow tires respond more quickly to steering inputs, and that creates the illusion that they respond more quickly to pedaling input.

I agree about Raleighs. I have owned several, and I currently own two. One is a 1974 International. The 32mm tire is tight between the chain stays, though.

You have an accident waiting to happen. Your chain is too short, and you will accidentally shift into the big-big combination, causing some kind of breakage.

Not in my view. Long reach dual pivot brakes work well, even the no-name kind.

Lemond1985

Disagree. Show me someone winning a grand tour on anything over a 25 mm tire.


This is the exact reason why I'm reluctant to post photos here, because some genius spots a toilet paper roll in the background that's hung the wrong way, a quick-release that's open (or a chain that's too short). The pic was for demonstration purposes only, I wasn't planning on entering any local races that way. Thanks for the warning.

Bill in VA

I find on the vintage bikes I have owned and looked at closely, the fit issue is more related to tire to fork crown or rear brake bridge than width of the stays or blades. Seat tube clearance is not usually an issue unless it was a full race or criterium bike. Even those may still work if equipped with vertical dropouts or if you do not mind deflating the tires to mount the wheel.

So if you orignally had short reach brakes with 700c tires you will be hindered. If the originals were 27" "usually" no issue. It the originals had long reach or medium reach brakes or had fenders with 700C it will probably work, especially without the fenders.

My wifes bike it challenged with 28mm mainly due to how far the sidepulls can open when the QR is used due to the narrow rim width. She can run Compass 28s but not Conti 4000S II as they run closer to 30mm and also hit the crown and bridges or brakes.

non-fixie 

Well put, and exactly what I meant to say by using the term "sluggish". Sorry if I used that incorrectly.

Speed is not my main concern, but I do care how a bike feels. I like to feel how a bike responds to road conditions, and experience the difference between bikes. It's also one of the reasons I like cotton bar tape.

.

But it's that inertia that is keeping me away from

Phamilton

@bikemig, you mentioned earlier you like old Fujis - I had (have) a '73 Special Road Racer that would fit a 700 x 38 tire under fenders. The SRR is a low end frame but you may be able to find a Fuji Finest or something similar that will have identical geometry/clearances. I only rode it that way once to test the fit/clearances and have no pictures of the bike with those wheels on it. The pads were already at the bottom of the slots on the 27" factory wheels so I'd have had to source some long reach sidepulls or the 750 centerpulls, but those are easy to find. I never converted the bike to 700c, I put the 27s back on it until I "retired" it.

due ruote 

I sort of see your point, but the difference is likely in weight and increased wind resistance from a larger profile. Speaking for myself, the first factor isn’t big enough to trump the ride quality benefits of a wider tire, and I don’t ride nearly fast enough for the second factor to come into play. Ymmv.

bikemig 

Yeah, thanks. Yes I was thinking of an old Fuji that came with 27 factory wheels as quite possibly clearing 700 x 38c tires. Other possible contenders include a Raleigh Supercourse (531 plain gauge main tubes) and a 70s era Motobecane Grand Record.

noglider 

It's more complicated than that. The difference between wide and narrow is probably greater at top speeds, which the rest of us don't reach very often. Secondly, there are always tradeoffs, and all things are never equal, so a narrower tire is always lighter. But for long distances, more research may show that better shock absorption leads to lower fatigue in the human body which is hard to measure but is a form of energy efficiency.



Sorry. I didn't mean to sound critical. But not racing is not a reason you're safe. I don't mean to sound judgmental. I just want to offer a useful point, and I know you didn't ask.

bark_eater 

While borderline to the C+V definition I am dialing in a 90's Koga Miyata CityLiner with big tires.

It looks like I will be able to get 38's and fenders but its tight. I had to bend the chain-stay fender mounting tab and now I have 4 mm clearance all around. The tires are Schwable Marathon plus HEAVY Duty tires that I all ready had and the rims are HEAVY Duty Velocity NoBS. I never got a chance to ride the bike before stripping it to a frame.

Taking it out now the frame is very flexible and feels overpowered by the wheel weight. I can grab the handle bars and shake the bike into an impressive shimmy. This is probably influenced by the quill stem adapter, and I'm going to try and snug up the headset.

Other issues are the raising of an already high bottom bracket and lets say "Sporty" steering. The steering is likely amplified by using a short stem, which I'm swapping out for a longer one, but I think there is an increase in trail caused by the taller tires.

Point being, I'm not sure that bigger is always better, at least with light frames and 700/27 wheels.

Andy_K 

This is all pretty sound reasoning. When I was planning a 650B conversion, I got some wheels and tried the fit on various bikes. For all of the frames I tried, the brake reach problem was worst on the rear. The only bike I found for which a Tektro R559 (which has a generous 73mm of reach) would work unmodified was a bike that was designed for 700c wheels and short reach brakes. That combination doesn't typically coincide with clearance for wider tires, though in that case (a 1987 Centurion LeMans RS) a 650x38 tire did fit. For the other frames I tried, the rear brake required some work-around -- either a drop bolt or dropped pads. The dropped pads rendered a Tektro R559 as mostly ornamental (not that a rear brake needs to do much). Drop bolts are generally ugly, but the brake works fine.

There are some center pull brakes with more reach than the R559 -- MAFAC RAIDs and Weinmann 750 come to mind. I tried the 750s and found them to weak with the pads all the way down. I hear the RAIDs are better.

Phamilton

@bikemig, just for fun I put the wheels from my hybrid on the Fuji frame. Tires are nominally 38mm and measure 38mm exactly on these wheels. A 40 would be tight between the chainstays but there’s plenty of room everywhere else.

Phamilton

And also I measure 66mm center of brake bolt hole to center of rim brake track front, 62mm rear. I hope this info is helpful, but if not it was a fun exercise.

bikemig 

This looks cool, yeah I'm not surprised that this was a bit tight around the chain stays.

greatscott

The widest tire I have on a vintage bike is a 27 x 1 1/4 which works out to 32mm wide, that's the widest I can get on that bike with fenders, remove the fenders and I could probably put on 36 or maybe a 38, but the rims I currently have on it wouldn't handle a 38 right.

Lascauxcaveman 

This is the only hint as far as tubing:

bwilli88 

I am running a bunch of larger tires on a bunch of frames.
I have a number of 27" bikes with 1 3/8 tires that are Vietnamese tires that run 40+mm; 2 Raleigh Grand prix and a 80s brit market Raleigh Road Ace.
I am running 700Cx42 Schwalbe Marathon Plus Tours on my 81 Centurion Pro Tour and 37mm Marathon Plus on my 83 Pro Tour.
I am running 700Cx35mm Panaracer Tours on my 78 Raleigh Super course and 700Cx37mm on my 74 Grand Prix.
I like big tires. I also have a 32mm on the front of my Zunow with a 28mm on the back.

Did I say I like big tires.