Monday, May 18, 2009

Tire Stuff: A Follow-Up

My post about the humble Michelin Dynamic actually garnered an off-blog reader e-mail from (I presume) a real person who just stumbled into this dark corner of the interweb. I was more than a little humbled (though not as humble as the Dynamic) to find out that my audience is bigger than just the visible core that comments on my prattle. So, in Aden's honor (hi, Aden!), I'll try to address some of those off-blog tire questions here for the (questionable) benefit of all.

Aden writes:

I live in a relatively rural area in central Virginia, and my riding will be about 80 percent pavement (and to a lesser extent, hardpack bike trails)--lots of group rides, limited commuting, etc--and about 20 percent unimproved roads (dirt/gravel), fire roads, and the like--just casual outings, nothing that would really qualify as "mountain biking". So should I go with the 700x28s or the 700x32s (my rims are 15mm wide, inside measurement, BTW, and I'm a light rider at 145 lbs). I'm sure the larger tires would be smoother riding and perhaps better on the trails, but I'm also concerned about weight and shooting for minimal rolling resistance since the larger percent of riding I will be doing will be on pavement. What to do?

First, I need to disqualify myself on two counts. One, I've never been to any areas of any part of Virginia, so I can't say what's suitable for a rural area in central Virginia. Two, I haven't been 145 pounds since about the fourth grade (yup, I was a husky lad), so the world of the sub-150-pounder is about as foreign to me as the Klingon home world.

But, with those caveats in mind, here's my nutshell response: Read Volume 5, Number 1 of Bicycle Quarterly. Seriously. I'm just a subscriber, not a shill (and I have my issues with some of BQ's other research/hypotheses), but V5#1 (commonly known as the tire test issue) is a winner. It's the only research I'm aware of that attempts to put tires to a real world test (where most of us ride) rather than spinning them on a steel drum in a lab and calling it good.

In that real world, I've found BQ's somewhat controversial assertion that wider tires at lower pressures actually roll
faster to be true. How can that be, when everyone else seems to say that the skinner and harder you can run your tires, the faster you'll be? Think about the roads you ride on. Are they perfectly hardwood-floor smooth? I'm guessing not. Mine are pretty bumpy. And when I hit those bumps, a narrow tire with a lot of pressure tries to bounce. Maybe a tire bouncing Aden's 145 pounds is no biggie, but to bounce my girth takes some energy -- energy that's no longer available to move said girth forward.

Now, hit those same bumps with a tire that's maybe 10mm wider than race rubber (at least 32mm) and running down around 70-80 psi. The tire deforms rather than bouncing, and the bike/rider keeps plowing ahead with a lot less wasted energy. This is all a grotesque oversimplification of the fine work in BQ, but it at least gives you the drift.

Aden also asked about weight, which can often be the bugaboo of this "wider is better" argument. After all, tire manufacturers have chased that "skinnier is faster" fallacy for a while now, so they assume their 700x32/35/38 offerings are only being snapped up by tourists and commuters -- folks who aren't trying to get anywhere in a hurry, but want a tire that won't flat easily. That leaves the fat-tire buying public with a lot of similar choices: thick rubber, chunky sidewalls, belts to deflect poky objects, and a lot of weight -- which can take work to spin up to speed. The Dynamic isn't bad in a 700x32 (at a claimed 360 grams, though I kinda don't buy that), but it still starts with a thick cap of rubber in the tread area that could be lighter/more supple.

What I'd
like to see is an unbelted, folding semi-slick for 700c wheels in about a 40mm width. No extraordinary measures to prevent flats, just a reasonable rubber cap and nice flexible sidewalls. Proponents of the kooky 650B tire size (tee hee, how I love poking the 650B bear) claim that the 650Bx42 Gran Bois Hetre (imported by Bicycle Quarterly, so I guess I am a shill after all) is the tire I seek, but I'd like it in a normal diameter, please. And while you're at it, how about black sidewalls and tread? That's not a baguette in my pannier (I'm just happy to see you), so I don't need to look like a 1950s Frenchman headed out for a picnic.

Um, Aden, what was that question again?


John Speare said...

The 37 mm Panaracer Pasala is pretty close to your ideal tire size. 3 mm close to be theoretically exact. Hopefully you can find this in a non-Tourguard version. The tourguard version is pretty thick and not supple, but better than most other (ahem-Schwalbe-hem) options, which are super uncomfortable IMO. And they're cheap (about $20 each).

Steve Fuller said...

There are a lot of people that seem to think the Grand Bois is the holy grail of tires. I don't have a 650B shod bike, and I don't plan on owning one as I have enough issues keeping tubes organized for a fleet of 700c wheeled bikes.

The Schwalbe Marathon racer might be worth looking into. Light and a good center tread for road riding. I will state for the record that lately, I've been looking at tires with good off road capabilities that roll adequately on pavement and hardpack. (and I'm closer to Jason's weight than yours). ;)

Jason T. Nunemaker said...

John, that 37 Pasela would be a good call, though I prefer black sidewalls. I'm wondering if the new Panaracer Ribmo (stupid name) could be a winner, though they aren't exactly cheap.

Steve, I'll be curious to see how your Schwalbes work out. I hear great reviews, but I've never tried them. I guess if I'm going for wide, I should just shoehorn some Big Apples in there!