Friday, April 30, 2010

When Fat is Good

We all know that fat is not exactly healthy.  It leads to all kinds of illness, disease, and a shorter life expectancy.  But there is one place where some extra girth can actually be quite beneficial.  It's in your tires!  No, I'm not speaking of your own physical "spare tire", but in your bike tires.

For many years there's been a trend toward ultra-narrow road tires ... brought on by an industry marketing of racing bikes to the general masses.  Three years ago, I truly believed that if I wanted to be a "serious" cyclist, I needed to have a carbon frame race bike with skinny tires.  That may be true if I was interested in racing ... but for recreational, transportation, and general fitness applications, adding some "fat" rubber to your rims can be quite beneficial to both enjoyment and safety.

I won't get into the physics of tire width, air pressure, rider weight, rolling resistance, and so on ... as there are many resources for that if you really want to research the technical side.  Visit Schwalbe's website for one such study, and while reading it, remember that this manufacturer makes ALL kinds of tires, including skinny ones.  All I can say is that fatter tires are more fun ... at least for me.

My Surly LHT has been fitted with Schwalbe Marathon Supreme tires in the 26"x2" size.  That's a pretty huge tire for a road-oriented bike.  Take a look at the photos and see for yourself:

They fill up the frame nicely, no?  What they provide is a very large volume of air at lower pressure ... which translates to cushion ... which translates to comfort.  Many of the roads here are chip sealed, and not exactly smooth.  These tires really float over all the ragged surfaces.  I like that.  When rolling over bumps, the extra cushion also flexes more like a set of shock absorbers, rather than jarring the bike (and me!) up and over it.  It's for these very reasons that Schwalbe and others maintain that wider tires actually have lower rolling resistance than skinny tires.  I tend to agree with them, having bikes with both fat and skinny tires.

I've also found that bigger tires also tend to flat less than their thinner counterparts.  I'm guessing this is due in part to their lower pressure and ability to flex over objects, but that may not be the science behind it.  The Marathon Supremes do have excellent puncture protection, as well, but I speak from experience with other tires in addition to them.  I have almost never had a flat on fatter tires, both in 26" and 29" varieties, but have had plenty on 700x23 or 700x25 tires (prior to finding Schwalbe Marathon Plus, that is ... but that's another post altogether ... patience, my friends ...).

Another benefit to rubber of the rotund variety is load capacity.  I do some grocery shopping on my bike, and often carry multiple cartons of Silk Milk (the unsweetened organic kind, of course) along with canned goods and other heavier items.  Groceries combined with my own weight can be a lot for a bike to handle ... so a set of tires rated for hauling cargo is a nice thing for peace of mind.  The Schwalbe Marathon Supremes in my size are rated to carry 140kg per tire at maximum inflation.  That's 280kg for the pair, or a total of 616 pounds!!  Now, I doubt that I could ever manage to put that much weight on my bike, but at least I know that the combined weight of the bike, me, and whatever I carry will NEVER exceed the rated capacity of my tires. 

The last benefit to fat tires is lower effort to inflate them.  Yes, that's right, LOWER effort.  High pressure tires may require fewer strokes from a large pump, but those strokes are much harder.  I used CO2 cartridges for flats on the road bike because I could never get the tire up to 100psi with a mini pump.  Getting a fat tire up to 50psi out on the road takes some extra strokes of the pump, but I can always reach the pressure I need with free air and no CO2.  To me, that's important.

Is there a down side to fat?  It depends on your point of view.  If you're all about having the lightest bike possible, then you probably don't want big tires ... they do indeed add some weight.  In the case of the Marathon Supreme, however, they are actually quite light in comparison to other similar tires ... but still not as light as skinny race models.  Some may feel that the additional weight makes the bike slower.  I suppose that may be true, depending on your comparison.  My experience is that I get to my destination in about the same amount of time, whether I'm riding my Surly LHT with big fat tires or my Look 555 with skinny tires ... give or take a few minutes.  The few minutes may matter to you, and that's perfectly fine.  For me, I'm not interested in making the ride as short as possible ... a few minutes more makes for a few minutes more fun!

I've also found that the extra-wide tires don't slide out from my released/opened brake pads when fully inflated on the rim ... they're just a tiny bit too wide.  I have to let a bit of air out so I can squeeze the tire thinner where it passes between the pads.  At first, I was rather irritated by this, but then I realized that the only time I'm removing the wheel from the bike is when A) I have a flat, in which case the tire is not inflated, or B) when truing the wheel or performing some other kind of maintenance, in which case I can let some air out for removal and re-installation.  So, when I really think about it, it's a very minor inconvenience in contrast to all of the wonderful benefits.  But if that bothers you, or if you routinely need to take your front wheel off for bike rack mounting, you may want to consider the clearance between your brake pads before purchasing.

Whatever tires you ride, check them often for proper air pressure, look for any puncture-causing debris that may be clinging to the tread, keep them clean, and then go ride!

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