cyccommute 

First, consider what the difference between 40mm, 37mm and 35mm tires are. 3, 2 and 5mm. 5mm isn't even a quarter of an inch. 3mm is just shy of 1/8" and 2mm is just shy of 1/16". Are those really that large a difference? Going from a 40mm to a 37mm is a trivial volume difference. Going from 40mm to 35mm is still trivial.

Consider the difference at the contact patch which is the only place it really matters. A 3mm change in height is like adding a nickel under your tire. Is it really that radical a change?

I'm not sure the weight difference is going to be all that great either. Frankly, I'd be more concerned about the crappy performance of the Continentals. I've had far too many problems with Continentals...including getting stranded at a campground in Atlanta, Texas after the 4th blowout in the first 26 miles of a tour (see Twisting Down the Alley) below. A Bell tire from Helmart is better...and I've had to use one to replace yet another Continental failure.

Sheldon Brown's chart is very conservative. In my opinion, too conservative.

How does the bike handle and what pressures are you using? I regularly run 2.2" mountain bike tires on 17mm rims at 40 to 45psi on the rear (with and without rear suspension) with 50 to 55 psi on the front (with and without a suspension fork) and have never had any kind of handling issues either on- or off-road. I know that current fashion is to run tires with stupidly low pressures but I've never found flat tires to give a desirable ride and I like my rims. I corner hard on both pavement and off-road and never found that wide a tire on that narrow a rim with that pressure to have "handling" problems.

That's also the pressure I use for bikepacking.

jefnvk

Not planning on carrying a spare this trip, but when I do, it is a cheap folding generic sized one I got off the Wal-Mart clearance rack for $1. Mostly just concerned with something that'll get me to a shop to buy a proper replacement that doesn't take up too much room.

fietsbob

OK, OTOH, I brought 3rd of same , sidewall casing failure, 3 months in,
I left that one on a farm in southwest Scotland.

cyccommute 

I think you are missing the dynamics of rotating weight. It's always accelerating (deceleration is only negative acceleration). Pick a point on the wheel. Move it. The spokes put force on the wheel to pull that point into a different direction. That's the "external force" acting on that point of the wheel. The point accelerates away from the straight line. And it just keeps on accelerating which means you have to keep adding force to keep the wheel moving.

You also have to consider that we don't live and ride in a vacuum so we are always punching a hole in the air. The act of moving the air out of the way is another acceleration...well, deceleration, that we have to keep putting energy into overcoming. There also some frictional forces which are mostly trivial.

And then there is gravity. Every hill is an acceleration to lift yourself up it. Yea, we get a bit of a freebie on the other side but that's paid for.

We are constantly accelerating on a bike when we ride. Weight makes a difference.

boomhauer

The tension in the spoke is the constant force, not the force from the pedals.
A satellite in space doesn't need a constant tangential force to keep rotating around the earth , only the "tension" from gravity.

Marcus_Ti

No I really don't have to consider it, in the context of touring. The aerodynamic difference between a 35mm and a 45mm tire is moot IRL...because the difference in aerodynamics is orders of magnitude smaller than the drag of the rest of the system....unaerodynamic things like panniers and racks--never mind the rider.

If you're worried about winning a crit or a TT or any race, you'd have a point. Marginal gains everywhere. But people hauling 50 lbs of non-aerodynamic luggage like sleeping bags and tents and panniers don't care much.

Tourist in MSN

That is also my theory of a spare tire on a tour, one that will get you to the next bike shop to buy a better one.

But I carry my lightest smallest (folded volume) one regardless of cost. Since it is unlikely to be used, it lives in a zip lock in the bottom of a rear pannier.

Big Lew

My first long tour included riding on hundreds of miles of varied pavement with a lot of tarred surface cracks.
Each tarred over crack stuck up above the normal road surface. I was very glad I had 2" mb tires on rather than
my usual 32's because I was carrying 50 lbs of gear. I don't remember the brand name, but they had a narrow
solid center which helped me attain my highest touring average of 85 miles a day on tours of over 1000 miles,
so I don't think using wide tires designed for pavement use as well as off road are going to slow you down that much.

cyccommute 

And? Yes, the tension from the spoke is the force pulling any given point from a straight line into a circular path. That still means that any given point on the wheel at any given time is experiencing acceleration. Without force from the pedals, the wheel stops.

Entirely different system. The satellite has reached sufficient speed that it misses the earth when it starts to fall back down. The earth is pulling it down but it keeps missing the earth. Because it is moving in a vacuum, it continues until such time as something changes the speed.

Rob_E

I think I started with tires in the mid 30s, and when they wore out, tried 32s, but they gave a harsher ride, in my opinion, so I went back to my old size, and eventually switched to 40s. Then, in order to go fatter, I got a different bike. Now I'm on 2.15 Almotions (55mm), and apart from the tires being a little stiff, I'm very happy with them. My other wheelset is 2.5" ETs, and I'd probably use them on any trip that had a significant amount of unpaved travel. Rode them down the GAP last year, and they were great, but the rims don't fit in my S&S case and tires preclude me from using the bus rack, which I sometimes take advantage of.

What I've found is that wider means I can get away with lower pressure, which can offer significant improvements in ride quality on any non-paved surface. Tread and tire suppleness play into comfort a lot, too. My ETs are pretty buzzy on pavement stretchs but still roll fairly well because they are supple. Meanwhile the Almotions are great of pavement, but I think it's only because I'm running them tubeless that they're supple enough for comfort on other surfaces.

For me, I'm always happy to go with wide tires, but that's not the only factor. I only enjoy a stiff tire on pavement, and I'll still take a supple tire there if I can get it.

cyccommute 

I wasn't addressing the aerodynamic force on the tires but the aerodynamic force on the rider/bike system. We are always accelerating against it. That's work we have to put into the system and any extra weight, especially rotating weight, is weight we have to accelerate through the air which makes us work harder. We're already working harder than those TT guys and racers.

boomhauer

[QUOTE=cyccommute;20390391. Without force from the pedals, the wheel stops.

Entirely different system. The satellite has reached sufficient speed that it misses the earth when it starts to fall back down. The earth is pulling it down but it keeps missing the earth. Because it is moving in a vacuum, it continues until such time as something changes the speed.[/QUOTE]


Once the wheel is in motion it stays in motion.....no matter how much it weighs.......(in a frictionless world).

A satellite stays in motion ....no matter how much it weights....

You seem like an educated dude.......I hope your boss doesn't see this post.

J.Higgins 

I've probably mentioned this before, but I think wider tires give a much better, albeit slower ride. My ECR is awesome for what it was designed, but its sad on pavement. The large diameter Cupacabras float over potholes and cracks like they aren't even there, but rolling resistance gets to me on longer trip intervals. If the ECR were an Ogre, and I was rolling some 2.0" Schwalbes, I'd be flying.

HTupolev

The spokes aren't required for a rim to experience centripetal acceleration. They're merely required to connect a bicycle to the rim. A rim can spin just fine without being attached to any spokes.

But more importantly, the centripetal acceleration just redirects the motion along a circular path and causes no change in speed. Even though the velocities of points on the rim are constantly changing their direction, this doesn't change the energy of the wheel system, so no forces need to be applied to the wheel to keep it rotating.

Moving air out of the way is drag. The extent to which the wheel accelerates in response depends on the net forces on the bike. Obviously some amount of microaccelerations are inevitable, due to variations in drags and the uneven force application through the pedal stroke. But when riding steady, this doesn't really increase the impact of heavy wheels. Heavy wheels do accelerate slower, but they also decelerate slower, so the amplitude of microaccelerations is made smaller.

jefnvk

Theoretically it should only be a negligible amount of difference, but in this case it is a very visible difference. As far as manufacturers, I remember from another thread that I can find folks on here that have had bad experiences with nearly any tire brand. Heck, one thread I found while trying to look these up claimed they had so many flats on the Marathons they went to Contis


Yeah, there's smaller out there, this is just what I had and I'm not saving all that much more space going to a 23. Not to mention, if I have already cut down a touring tire, I don't really mind the next tire going on there is a bit thicker kevlar one. Am amazed how small some of those 23s are folded up!

​​​​​​​Yeah, not worried about aero. I figure taking off bags would take care of more aero issues than running narrower tires.

djb

jef, which marathons are they? Regular ones or the plus ones?
As for running them into the ground, I have a pair of regular marathons that must have 10,000kms on them and they still look reasonable.

jefnvk

Regular, I believe. Dont see plus or mondial or supreme anywhere.

L134 

MarcusT

Can't argue with logic like that

LeeG

andrewclaus

Good point. Similarly, there's no comparison between my 25mm Schwalbe Marathon beasts and my swift 25mm Gatorskins. They're nominally the same size, but they're different tires for different uses. (When I supported my wife on her Katy ride. She started out with her favorite Gatorskins, but soon gladly switched to the Marathons.)

gerryl

You'd be well served with fat tires. It's interesting that while racers are going as fat as they can fit on their bikes, tourers are still in the skinny is better mode.
Here is a link to an interesting article. Fast fat tired

Rob_E

Makes sense to me. When I switched from 700x40 to 26 x 2.15, I was always in danger of running into things because I was mesmerized by my fat, front tire. When I put my 2.5" ETs on, forget about it. My commute time, however, remained pretty consistent.

Tourist in MSN

Agree on travel time being comparable. I used to have two sets of wheels for a 700c touring bike. One set had heavy duty rims for touring, 37mm wide tires, etc. And one set were 25mm, high pressure, thin tread with supple casings. The 25mm tires felt unbelievably faster, but when I got home after a 20 mile ride the 25mm tires resulted in about a 3 percent reduction in moving time. I consider a 3 percent difference to be not much more than round off error.

jefnvk

I don't know if it is so much tourers are looking for skinny, my question was more of a "at what point is big too big?". I see the virtues of fatter regularly talked about here. TBH, if I didn't have these or the Contis lying around, I'd probably buy another set of my 35mm Clement USH for this, not exactly lightweight tires themselves. Just more wondering at what point, if any, you really started hitting practical differences.

Also, interestingly enough, when I went to look for a rim size (none stamped that I could find), I notice these are also stamped both 40-622 and 700x38, so not even sure which they really are. I'll give them a go though, worst case I take them off after a few weeks.