abdon 

I guess this is as good a place as any to stick this in...

I'm looking to build a set of 650b tires for a commuter/rando bike. The bike is a former hard tail dirt bike currently running 26"x1.0 tires so there is plenty of space there. This is an open road bike and I would like to bump the tire size while keeping a fairly high tire pressure.

So, what are my choices for skinny 650b tires? I'm thinking that this way I could have my pie and eat it too; a 28~31mm tire size on a larger diameter wheel, coupled with high tire pressure.

ThermionicScott 

The Grand Bois and Hutchinson 650x32B tires come to mind. Compass sells them, among others.

lungimsam

There is also the 33mm maxy fasty https://www.rivbike.com/product-p/t101-10087.htm
But beware, Jan heine of Compass bikes found tires with similar tread to be among the slowest he tested.
I think the Grand Bois 650b's were among the fastest tested.

I searched far and wide last fall for skinny 650b tires, and there are none skinnier than 32mm that I could find.
I would like a puncture protected 32mm 650b tire, but there ain't one that looks good to me out there, so I just use Grand Bois Hetres (40.5mm on Synergy rim, unprotected) and Marathons (40.5mm on Synergy rim, overkill protected).

robertkat

Hutchinson makes a 32x650b tire that is supposedly a high quality, durable, and at a good price point. AFAIK, 32mm is the narrowest 650b tires go. Also, you still won't have a high pressure tire. If you want higher pressure and/or a 28mm tire, just go to 700c. That wheel size will fit on an MTB frame. I've done it.

lungimsam

I like my wide 650b tires.
Makes scrambling over rough streets easier for me.

Just the other day I was leading cars through a traffic light and hit some busted up roadway and sure was glad I wasn't bouncing around on my 700 x 25 120psi tires with all those cars just behind me.

The wider, lower pressure tires roll nicely over bad roadway. I feel much safer on them than my 25mm/120psi tires.

rhm

The question that comes to mind is: why? The whole advantage of the 650b is the availability of high quality fat tires.

corwin1968

I was really curious about Jan Heine's findings on wheel size/tire size combinations so I ordered the relevant issue of Bicycle Quarterly. I don't remember the specific numbers but he and his fellow testers found that skinny 650B tires just didn't handle very well. Roughly, 700c = skinny tires, 650B = medium tires and 26" = wide tires for what he terms "optimum handling". I know that low 30's is the widest he recommends for 700c because that's what I ride. 650B might have been upper 30's to lower 40's but not sure.

abdon 

Long story short; to properly dial the bicycle in to its intended purpose and the rider. This rider is a short 115-pound girl that can get away with a lot less tire pressure than you an I could, and can run 28mm tires at 50/65 PSI front/rear without worrying about pinching a flat. Tires fatter than 35mm don’t gain her much more cushioning and end up taking away from other handling characteristics. Her ideal tire size for good roads/city traffic would be around 30mm.

Ok the long story now. As stated this is for a 5 foot 115-pound girl. Her ideal frame size is around 48cm C-T-T. Building a small bike to use 700C tires requires an ungodly amount of torturing of the geometry; at some point you can’t make the frame smaller because you run out of steerer tube, so builders simply raise the bottom bracket, screwing up the handling just because people consider anything other than a 700C tire bad. I’m after the proper tire diameter, with the proper amount of tire pressure for the intended road conditions, based on the rider/bike/load weight, and desired handling characteristics. I could find 30mm tires on 700C wheels but those won’t fit the frame.

On the other extreme 26” tires work but not well enough; a larger diameter will roll better over the random crap out there. To get the best tire radius the frame will allow it would require a super fat tire, which are only available in knobby style and would require waaaaay less tire pressure than optimal for the proper blend of cushion/performance/radius balance that I’m after. Our 115-pounds of girl power, plus about 26 pounds worth of bike comes to 141 pounds but let’s round up to 150-pounds unloaded, 180-pounds loaded. Weight distribution is about 45%/55% front/rear. We want comfort, speed, and a larger tire diameter than 26” in order to roll better over cracks and stuff. The intended use is open roads in good condition plus city traffic, so we are aiming at a tire that requires around 50~60 PSI.

Tire pressure: to achieve optimal rolling resistance while preserving comfort. For a 115-pound girl with a total bike/rider load of 150-pounds on fairly clean roads plus city traffic. 50-PSI would be an ideal amount of cushiness so we work our way back to achieve a 15% tire deflection. 15% tire deflection, or how much the tire squishes under load, has been tested to be the ideal amount of deflection for rolling resistance purposes. More tire pressure beyond this point makes the ride harsher, and rolling resistance gains are negligible. The weight distribution of 150 pounds at 45% front/55% rear comes up to 67.5 pounds on the front, 82.5 pounds on the rear. Now; following vendor tire pressure recommendations tend to under inflate super skinny tires and over inflate fat tires. Fortunately an Australian by the name of Frank Berto did a handy chart to calculate tire pressure in order to achieve a 15% drop (google up frank berto tire pressure).

To bring this long story to an end: for a 150-pound total load a 28mm tire at 15% deflection can be achieved at 50/65 PSI front/rear. A 32mm tire could be run at sub 40/50 PSI. front/rear. A 30mm tire would be the ideal for the target PSI with enough volume for suspension (for the intended road conditions) and downhill cornering/gripping performance, without compromising rolling resistance and while having a large tire diameter to roll over stuff. The smaller size tire would also have the ability to bump up the pressure for when its time to load up the bike. Of course if you weight more than 115 pounds and you carry a heavier load, you can’t get away with 40/50 PSI on a 32mm tire. She can. You are also probably tall enough where a 700C tire size does not need to compromise frame geometry in order to fit, and there are plenty of fatties for 700C.

It is the little things that transform a ride into something that fits like a glove.

unterhausen

the usual solution for this problem is 650c. Tire availability will still be an issue, but at least there are a batch of triathletes using them I am not sure any of the tire/rim combinations of 650b are really going to work that well for this application

Designing a frame for a small person that wants to use 700c tires is a real problem. I am not sure about raising the bb so much, but a slack head tube angle is pretty much required. Anything a higher bb can do can be done with slanted top tubes, although then the stack is higher. For long distance, this may not be an issue because most of us use a little bit higher handlebars. The temptation to move the seat tube to a higher angle is nearly irresistible, but it only makes sense if the person has correspondingly short femurs relative to their leg length. This isn't usually the case.

rhm

Okay, all that sounds pretty good. I agree 100% that a smaller rider wants smaller wheels; in fact smaller wheels hold advantages for us all, but that is another discussion. Let me restate what I said, but with a little more detail.

I've ridden bikes with a lot of different wheel sizes, 16' (both kinds), 20" (both kinds), 26" (MTB), 650A/EA3, EA1, 700c, 27"... I'm actually working on a 650B build now. Maybe others. And what I've learned is that diameter, by itself, makes little difference to the ride. Tire width and other tire qualities make more difference. So the advantage of 650B, that you can get snazzy fat tires, is wasted if you don't want snazzy fat tires. You're left only with the disadvantages of comparative rarity, few rim choices, etc. You might be better off with 650c, or even 26"(559mm).

Also, I didn't see any mention of crank arm length in your post. I've put my daughter on a little Lotus, made for 700c, with 26"(559mm) wheels; this necessitated hub brakes and shorter crank arms, which added up to a pretty good fit. You seem to want something a little racier than what my daughter is riding, so I'd look into 650C.

antimonysarah

As a short (though not that short -- I can just squeak onto 700C frames without making any major geometry concessions) woman who owns bikes with 26", 16", and 700C wheels (and has ridden a bunch of bikes with 27"), there's really not that big of a difference in the diameters except at the 16" end. Remember, a 26" wheel, proportionally, will be just as "big" as a 700C wheel is to a rider not that much taller. I'd go with 26", which is going to have lots of tires available for years to come for sure, no matter what happens with the 650B fad.

Heatherbikes

Thanks to abdon for explaining something very important! I have asked the higher powers that be(compass bicycles) for a more narrow 650b tire. I know 650b is all about fat and cushy, but that is for average to large sized riders! I am interested in 650B because I am that 5'2" little woman who wants smaller wheels on my bikes. I had a 26" wheeled bike and hated it. I have not tried 650c but it has it's own availability issues and lacks any supple tire choices. Also converting a 700c bike to 650c could be more problematic, you really do have to look into shorter cranks etc. I think 650b would be a good size to convert my bikes to, but being small I would really like something more narrow than 32mm, because for me, they would not be narrow, they'd just be perfect. My husband recently got the 700x32 'cypres' tires and they are actually only 30mm wide and really big! I have a few small vintage bicycles that were designed for 700c which is so silly because you can see the compromises made in the design. No bicycles for little people should be made with 700c wheels.
Also, I believe narrow 650b tires would handle well on small bicycles with small riders. If Heine and his colleagues are all largish mens, the results are going to be different, no?

unterhausen

the handling issues with narrow 650b may be rim choice as much as anything. However, we are stuck with the rims we can get.

Carbonfiberboy 

Short, light female riders who ride with us, including rando, all use 650c. Good availability of wheels/tires/tubes for road riding. Only hassle is that your buds may not be able to help you if you run out of tubes or slash a tire.

I don't get why you want both a narrow high pressure tire and also a tire wider than 25mm to run at low pressure. Seems like a contradiction. My wife runs a converted MTB frame with 26" X 1" which works OK. We've considered converting to 650c to get a better tire selection, would probably stick with 23-25 mm tires to get a good ride at her weight. She wouldn't run a tire at a lower pressure than the minimum shown on the sidewall. Good to keep a well-seated bead.

bowzette

One of my bikes has 650c wheels and it rides well with 23mm tires over rough chipped sealed and old county rough roads. I haven't found tires wider than 23mm however. I weigh 140 lbs. and my rides are 50-100 miles not long distance events.

thebulls

My wife's 1986 Trek 400 wouldn't take anything bigger than a 25c (with fenders), and she felt really unsafe riding on bike paths that can easily have wet leaves, slippery mildew on wood, longitudinal cracks, etc, and on downtown DC streets with potholes, manhole covers, etc. So I converted her to the Soma 650Bx38 B-Line's and she loves them. They are just as fast as any tire of similar construction, e.g. Panaracer Pasela's. But much more stable. Skinny tires are not faster than fat tires. High-pressure tires are not faster than low-pressure tires. What matters is the casing and the tread. Similar casing and tread produces tires of similar speed, independent of size and (across a wide range) tire pressure. That's based on my personal experience, but also based on Jan Heine's extensive tire testing.

Nick

Heatherbikes

Here is a list of 650c tires Bowzette Team Estrogen: Guide to 650C Bicycle Tires (ISO 571 tire size)
For small riders, 650B is often not enough of a solution for 700c bikes because the tires are so fat they do not lower bottom bracket and can still cause wheel flop. 650c is the better choice, but you do not have the supple tire options.

ThermionicScott 

That's a shame -- 650C was once the fattest tire spec out of the 650mm family.