TenGrainBread 

But the tire is a fixed piece of material - it doesn't get bigger, it just gets pulled one way or another. If you stretch the beads out with a wide rim, it makes the tire more oval-shaped, the top of the tire getting lower.

CO_Hoya 

This is true if the beads are nearly on opposite side of the circle, as I noted when the rim is large compared to the tire.

When the tire is the majority of the circle, then increasing the rim size allows the circle to grow which increases the height.

non-fixie 

Tried a pair of Continentals (Sportcontacts, 37-622) on my Roy Thame:








Fit was fine, as was comfort. But handling on decent roads suffered more than I cared for.

So after a couple of days I replaced them with Challenge Strada Biancas in 30-622. Liked those much better.

bikemig 

That bike is hot. I thought you only liked the bikes that no one else seemed to want?

rgvg

If it's not too new for you early hybrids shipped with 38s. I've seen them posted on C&V so maybe? Schwinn Crosscut. Call them vintage 29ers?

non-fixie 

I think people are beginning to catch on.

Thanks. I was looking for a high end touring frame in my size when this came along. Built it with my favorite parts for max enjoyment. I've taken it to France a few times on vacation trips and ridden it on and off road. This was September '18, in the Dordogne. As you can see it's sporting a different wheelset. Maxicar hubs, Weinmann rims and 28mm Paselas, my go-to all-terrain tire.

eeuuugh

I've put 700x35c tires on at least half a dozen frames that originally came with 27x1 1/4" tires. An 80's LeTour and World Sport, a Univega Nuovo Sport, a Ross 10-speed, and a few I don't remember. Most of them could have fit 38s, but one or two couldn't have, 700x35c has always been a safe bet. I put 38s on a Free Spirit 10-speed with a bare millimeter or two to spare, but I think they were Panaracer TourGuards, which run tall.

27x1 1/4" is a 630mm rim with 32mm of tire on top and bottom = 694mm height. 700x38c is 622+38+38 = 698mm height. Different tires will vary a few millimeters from these measurements, but if you've got a frame with 27x1 1/4" tires on it, you can look at the clearance and get an idea of what will fit.

Oh yeah, also had a 72 Sports Tourer I was planning to convert to 700c, definitely would have fit 38s.

inkandsilver

Bikemig, you've seen this one before, but it addresses your question. Soma Supple Vitesse 700x42, which measure 40-41mm on these Velocity Dyad rims. It's a tight fit but no problems so far. I had to grind down a bit of extra material on the bottom of the mounting yoke of the front DC 610 caliper.

noglider 

@non-fixie and everyone else: once you change tire width drastically, you have to experiment with different pressures. It may not be the tire width that caused funny handling. It could be the pressure or the exact tire model.

We've been talking a lot about lower and lower pressures, but I found that our tandem (with 26" MTB wheels) doesn't feel right unless pressure is up to 80 psi. In theory, we could get away with less, but it gets too wiggly.

bikemig 

That is a massive tire on your Moto GR. Beautiful bike as well. Yeah I figure a bike that was built around 27 inch wheels like this model Motobecane and center pull brakes is likely a good C&V candidate for a 38c tire.

You spread the rear triangle right?

I have a 1973 motobecane grand record that I need to rebuild and this might be the way I go on it. I have a set of wheels (tipo hubs and superchampion 58 rims) that would be great for this build but I'd have to redish the wheel from 6 to 5 unless I decide to spread the rear triangle.

What kind of gearing are you running? That is some massive gearing for an old bike.

cannonride15

@bikemig, don't forget 80's vintage mountain bikes, plenty of tire room. There's a thread on mountain bike drop bar conversion with some fine examples.

inkandsilver

Yes, rear triangle is spread to 130. I have been running it as a 2x1 with 44-30 in the front and using the high limit screw to keep it on 17t in the rear, just to see if I like having a 2 speed. Still trying to decide whether to go to a single cog on on the rear, or hook up the right side bar end shifter and go to 2x9 with 11-32 in the back.

TenGrainBread 

@inkandsilver Nice bike. I've had those tires (with the terracotta tread) and they are the bees' knees.

non-fixie 

You're right, Tom. And a higher pressure does improve the handling, but takes away some of the comfort. I've been experimenting with 35mm Paselas on our tandem, but there too, I'm inclined to go to 28mm, as I find the 35mm's somewhat sluggish, even at higher pressures.

Wileyone 

That looks like a Tommy Quick frame set.

Lemond1985

I have a 1976 Raleigh Competition that will "technically" clear 38's, just barely. It does much better with 35's though (they give me about 1/8th" clearance in the tightest spots) and I don't notice much difference between the two, except that the 35's are lighter and perform better on the road.

Pic shows the Raleigh with 38's. I'm totally sold on the Reynolds 531 Raleighs, BTW. Fine fine ride, excellent geometry, generous tire clearance, can't say enough good things about them..

non-fixie 

I believe it is.

canklecat

I was disappointed in Continental Sport Contact II tires too. I got a set last autumn in 700x32, hoping for a narrower version of my favorite hybrid tires, the Conti Speed Rides. The 700x32 tires would fit my old set of SKS Bluemel fenders, which were too narrow for the Speed Rides.

But the Sport Contact II felt sluggish at a comfortable pressure and harsh at full pressure. There wasn't any sweet spot. And it showed in my data. On the same familiar routes I was generally 2 mph slower. The thick tread and stiff sidewalls make for a mediocre ride. It's a decent tire for commuter and errand bikes -- durable and grippy in wet conditions. But it's not much fun to ride.

I switched back to Speed Rides last month after trying the Sport Contact all winter. The Speed Rides are better tires in almost every way. The only drawback is Speed Rides are available in one size only -- nominally 700x42, but measure closer to 700x38. But the ride is comfortable, smooth rolling, fast and grippy on pavement wet or dry, dry gravel and grass.

Lascauxcaveman 

1973 Nishiki Semi-Pro. The only place where fitting 700 x 38 is even a little tight is between the chain stays. Apart from that, tons of space left for fenders, even. These aren't as common as early 70s Raleigh Super Courses, though which you can find anywhere and fit very similarly.

But for long-running models, the year makes a huge difference. For instance, my '88 Trek 420 (Edit: ah, that's actually a Trek 400) maxes out around 28 or 30mm, whereas @mrv got some big meats on his older one, upthread. You kinda have to take the rims and mounted tires with you to check for yourself if they'll fit.

Kabuki12

1973 Super Mondia Special , My fat tire bike!
I run 27" x 1 1/4" Michelins ProTech on my 1973 Super Mondia. I have to deflate the rear tire to remove it , but that doesn't bother me. After I inflate the tires they check 1.390" (over 1 3/8") 0r 35mm and they still clear the frame! The Mondia bikes were used a lot in Europe for Cyclocross for this reason. I am pretty sure there are other frames that would work , but this one is particularly wide tire friendly. The ride is spectacular and very easy to navigate bad road conditions. Joe

bikemig 

That is a cool bike. I'd love to find one in my size but those don't pop up often. My first ten speed was a Nishiki so I like them. What is the frame tubing on the semi pro? This is sort of the build I was thinking of doing. I have the parts on hand to pretty much do a build like this if I can track down the right frame. A raleigh super course sounds like a good bet and they pop up on CL from time to time. There is a raleigh international on eBay that I've been trying to resist as I doubt it has the clearance I need; there's a Raleigh Gran Sport that I bet would work but it's overpriced. I almost never see older Nishikis like this on CL.

63rickert

Presumably if you want big tires you expect to do at least some riding where the road surface is a bit rough. Some place with loose debris. The rougher the ride the more you want some clearance. Big tires and big clearance go together. If you use all available clearance for stuffing tires into position inevitably something is going to get stuck, something is going to get damaged.

You are also riding around on a bike that looks like someone stuffed a grapefruit inside an orange peel.

The old Rickert mentioned previously had about 6mm either side at chainstays when fitted with 35mm tires. Again that was 35 measured, not the label. 6mm was not enough for anything but well paved roads with some potholes. There was also about 6mm at brake bridge. The Grifos were tall tires. I had problems a few times with twigs and pebbles getting stuck. The paint on that old bike was already very tired and there were a fair number of dents so it didn't much matter. And I never fell. But I could have.

If all you want out of the big tires is a boulevard ride get a boulevard cruiser. Anything that originally used 635bsd rims will have buckets of clearance. Or look at old German bikes and maybe old English bikes. French always used 650B for this. Italians frames that fit the bill are either very very old or for 635. You are looking for something that swallows 45mm fenders easily. Or has 50mm fenders. Take out the fenders and then you have room for the 38 tire to work. Super Courses are very nice bikes and also come in a lot of variety. None I've seen have anything close to working clearance for a 38.

Just because the wheel will turn doesn't mean you have a bike. More than half the tires shown above are well short of label size. Again, a real 35mm tire has a whole lot of plush. Use an Almanzo or a Compass Bon Jon and you are plush. Plush far beyond any stiff touring tire regardless of size.

Other general considerations. With a 38 the entire bike is a centimeter further up in the air. Maybe seek something with a low bottom bracket. Wider tire automatically increases steering trail. Plus the wheel is heavier. The bike will want to go straight. Unless it was lowish trail to start with. Look for forks with rake.

bikemig 

Reading through these posts, I'm thinking that 35c might be an upper limit on most vintage bikes with generous tire clearance (typically 70s era bikes that came stock with center pull brakes). Even most touring bikes back in the day tended to top out at 32c with fenders.

I have a Sekine SHS 271 (full tange frame set I believe) that I was thinking of converting to 700c wheels. It is currently running michelin protek 27 x 1 and 1/4 tires that measure out to 35c on my rims. There is no room for larger 27inch tire but I suspect it could take 38c tire. Whether there is enough room for a 700 by 38c when the rim thrown out of true by bad roads or for road debris is another question. You may well be right which is why a 650b conversion may be the way to go.

schiavonec

I had a motorbacon with weinnman brakes, and they seem very accommodating in general. i switched to 700c, but still had room even w/ cyclocross tires. (spares)

stardognine

I've been riding on some Bontrager 700x35s for about a month, and liking them. But they have a lot of tread, and the fit was close, on my '85 Cannondale ST400.
I recently bought some wheels (ok, the whole bike) that had very similar Bontrager 700x35s, but very little tread, so they fit much better. And still handle sand & gravel pretty well. 👍
So I'm pretty sure I could use the same tire, but in 700x38, as the thread asked about.