Which Schwalbe

[hem]

The math is irrefutable: 2 pounds of rubber is less than 1% of the total estimated mass of 300 pounds, 0.067. Thirty-two ounces is roughly two liters of water.

hmmm I seem to recall a liter being 33.792 oz. But maybe that just here in Arizona.

[Joe B]

Rotational inertia comes into play as well. 1 pound on your frame is different than 1 pound out at the end of a spoke. If you carry your bike up a hill or accelerate it forward  while holding it , a pound is a pound. However once you start spinning the weight out at the end of the spokes you get additional resistance, you still have to accelerate it forward and lift it up any incline but you ALSO have to make up the difference of rotational inertia as well. The amount of force added to the equation is equal to the total  forces of gyroscopic precession. Bicycles stay upright while we are riding because we have traded some energy from propulsion into gyroscopic precession. If your tires weigh more than you have traded more propulsion away.

For what its worth:
I ride on 32x700 Schwalbe Marathon Plus and I don't know or care what they weigh. The peace of mind they give me outweighs any Newtonian physics in play.

[hem]

hmmm I seem to recall a liter being 33.792 oz. But maybe that just here in Arizona.
[/quote]
He is talking about ounces of weight not fluid ounces.
[/quote]

I stand corrected. It should be one liter equals roughly one kilogram of water which equals roughly 2.2 pounds or around 35.2 ounces.

[staehpj1]

hmmm I seem to recall a liter being 33.792 oz. But maybe that just here in Arizona.

He is talking about ounces of weight not fluid ounces.

I stand corrected. It should be one liter equals roughly one kilogram of water which equals roughly 2.2 pounds or around 35.2 ounces.

My bad.  I realized my error and deleted the post then realized you had responded.  Sorry for the confusion.

On the original topic I will say that I find 2 pounds a substantial enough difference to worry about even if it weren't rotating mass which it is.  Also I find the stiff sidewalls of the Marathon Plus to be detrimental to ride quality.

[PeteJack]

The math is irrefutable: 2 pounds of rubber is less than 1% of the total estimated mass of 300 pounds, 0.067. Thirty-two ounces is roughly two liters of water. That delta of the effort to move this mass uphill or forward cannot be perceived. Nor does it translate directly into a 1% change in the total energy required to travel the same distance.   

I have to differ. A pound on a wheel is not the same as a pound in your paniers. The reason people pay thousands of dollars for wheels is because they are lighter,  specifically light rims and tires have a smaller moment of inertia.  An extra pound on a wheel will, very roughly, double the moment of inertia of a wheel, something you'll feel with every turn of the pedals. If this were not the case then I suppose we'd still be riding on steel rims.

[misterflask]

I have a pair of Marathon 700x35s (not the plus).  They can be wrestled on the rim by hand with a little bit of cleverness, and come off reasonably with tire irons.  I ran them 1500miles on a tour with no flats and there is barely any wear showing.  Here's the bad news though:  These two tires went on identical Sun CR18 rims.  One of the tires seats perfectly, but one never seats properly.  It's high in some places and low in others.  Several people have tried mounting this tire on multiple occasions, always with the same result.  I found it scary at first, but it eventually lured me into a sense of complacency.  On a smooth road where you'd like to really enjoy the ride, you can feel the tire's 'whumpy' spot.  Nevertheless, due to the extraordinary wear characteristics, I plan to buy more of these.  I'm going to mount them before I leave the shop, though.

[Trek950]

I have run the regular marathon 700x32 for years on one of my commuters and they are just about worn out, they are very comfortable and have never punctured which is pretty impressive for mostly NYC riding (think 3rd world road surface with extra broken glass).  I replaced the marathon plus on my other commuter with a lighter tire and really appreciate the increase in performance, also no punctures.
On my other bikes I use marathon XR, marathon extreme and big apples as well as panaracer tires.  My pluses sit in storage.
If I were doing your ride I would go light. Whatever you choose will work fine.

[mdxix]

They seem bullet proof

Says who?



With less than 1,000km on this pair, I got the nastiest of punctures. This old curved handmade nail penetrated the tire and shredded the tube.

[mucknort]

I don't know about the math, but Marathon Plus tires brought my family and I across the U.S. with no flats and no complaints.

[staehpj1]

I'd start with a basic reduction of the total mass in motion before rationalizing changing only the rolling mass. Lose 20% of the tent/sleeping bag/clothing/kitchen/tools. Heck, even sets of panniers and racks vary by many more than 2 pounds.

I agree on watching weight in all those areas.  They all add up.  A pound here and a pound there add up and the total difference can be pretty significant.  Over the years, my total bike and gear weight has dropped from about 75 pounds to under 40 pounds.  The difference in the ride is huge.

That said, I would start by not adding weight by purchasing tires that are two pounds heavier than other suitable tires.  If you already have the tires I can see wearing them out, but they were bad enough that I took mine off after a few hundred miles.

Given the poor ride characteristics due to the stiff sidewalls of the MP, to me avoiding them is a slam dunk.  Others who are less flat tolerant and more tolerant of extra weight and stiff sidewalls can certainly go the other way.

Rather than say that two pounds is insignificant, you could look at it as an approximately 50% reduction in the weight of one of many components all of which contribute to the total load.  That math is irrefutable too.  Depending on the rider's perspective they can choose which way they want to look at it.

[sspeed]

I know this is old, but Bicycle Quarterly did some controlled tests which showed speed can vary by as much as 20% (all things being equal) with just tire selection.

http://www.ohpv.org/forums/index.php?topic=115.0

Copy and paste of the summary:

Some test conclusions will be particularly enlightening if you’re riding on narrow, high-pressure clinchers seeking more speed via lower rolling resistance. Your skinny tires may not be as fast as you think.

For the full eight-page report on tire performance, order the Vol. 5 No. 1 issue from http://www.bicyclequarterly.com. The test included nine 700C tires, seven 650B tires and two tubulars. The protocol and results were reviewed by industry experts. These are eight findings:

—With roughly the same power output, the rider’s speed can vary by as much as 20% depending on tire choice. For example, the rider on the fastest tire [in this roll-down test] moved down the road at approximately 16.4 mph (26.2 kph) while the same rider on the slowest tire went approximately 13.6 mph (21.7 kph).

—Many longtime riders believe tires with a cotton casing are faster than modern casings made from nylon. Testing seems to confirm this. The best-performing tire in the test, the Deda Tre Giro d’Italia 700×23C (actual width 24.5 mm), has a cotton casing.

—Tire pressure has only a small effect on the rolling resistance of most tires. Narrow 23-mm tires seem to roll fastest at pressures of 105 psi (7.2 bar) or more. However, running these tires at 85 psi (5.8 bar) for improved comfort increased the test times only 2%. Wider 28-mm tires are as fast at 85 psi as they are at higher pressures.

—Tubular tires perform worse at very high pressure. At 130 psi (9 bar), the narrow Clement Criterium rolled slower than it did at a more comfortable 105 psi. The wider Clement Campione del Mundo rolled slightly faster at 85 psi than at 105 psi.

—Wide tires do not roll slower at lower pressures. In fact, testing indicated that a wide tire at lower pressures rolls faster than a narrow tire at high pressures, if all other factors remain the same. Even narrow tires can be ridden at comfortable pressures with only very small concessions to performance.

—Tires rolled slightly slower with Michelin’s relatively thick latex tubes than with butyl tubes. Thinner latex tubes, like used in tubular tires, may offer better performance, but when used in clinchers they are more prone to punctures caused by friction between tire and tube. Latex tubes do improve comfort.

—Perhaps the most important result of the test is that tire pressure does not significantly affect rolling resistance. Wide tires in particular do not need high pressures to roll fast. But because many current wide tires are designed to handle high pressure, they have strong casings that lack suppleness. This results in higher rolling resistance than necessary.

—The test’s findings point to a new direction for performance bicycles. For most cyclists, wide, supple tires at low pressures offer more speed, better comfort, increased versatility and improved safety than today’s narrow high-pressure tires. However, this type of wide, fast tire currently is not available. Hopefully, these test results will help persuade manufacturers to produce them.

[PeteJack]

If you want to experience the effect of additional rotational inertia without buying a spendy set of tires, put Mr Tuffys, which only weigh a few ounces, in your existing tires. I tried 'em and it was like riding through sand compared to riding without them. Got rid right quick. Mind you some people swear by the things.

[rockermike]

I rode across Mexico recently, 5000 miles / 5 months on 38mm Marathon Plus tires. 2 flats in the whole trip while some of the people I met en-route were getting an average of a flat a day (and losing their temper in the process I might add). Yes, they are heavy and sluggish - but with 50 lbs of gear on a bike, any bike is sluggish. My sense is that on the open road, once you get your tank up to speed and just keep going the disadvantages of weight and feel aren't that great. If you are in stop and go traffic or on an unloaded bike its a whole other ball game.