by Grant Petersen
The concept of rolling down the road on a cushion of air is what
Dunlop-the-Scottish-veterinarian had in mind when he invented the
pneumatic tire for his young son, a century or so ago. Over the years,
part of the concept has been lost, as riders ride the skinniest,
hardest tires their bodies can stand. It's not pure idiocy by any
means. Road surfaces have improved, after all; but even on smoothish
modern roads there are advantages to riding on 700x28s and 700x32s.
- More comfort. The more volume, the lower pressure you need. So,
when you hit a bump, the bump compresses the tire and isolates you from
most of the blow. It's the oldest, cheapest, lightest, lowest
maintenance, most fine-tunable type of suspension you can ride.
- Longer lasting wheels. Puffier tires run at lower pressure
protect rims and spokes from fatigue-inducing flexes and cornering
loads. Fewer pinch flats. That's when you hit a bump and it pinches the
tube between it and the rim. More tire pressure will prevent it, but if
you have to load up your tires with 130 psi just to prevent pinch
flats (and with skinny tires, you do), then you're doing it the hard
way. A 700x28 with 100 psi, or a700x32 tire with 85 or 90, will do the
job better and give you all those other benefits of volume.
Do wider tires have more rolling resistance? Yes, but it's mostly
the lower pressure that does it, not the size, and it's the lower
pressure that gives you all the benefits, too. Besides, the difference
in rolling resistance between a hard skinny and a slightly puffier
tires is infinitessimal. Fitness, body weight, and wind resistance each
matter ten times more. In a group, if you're in the same shape as
other riders, it's easy to ride the group's pace no matter what you're
on, because you're drafting so much of the time.
Finally, on rough roads, you go faster on a softer tire. When
the wheel hits a rock or a bump, the fatter, softer tire will deform
and roll right over it, while the hard tire bounces and jars you. Are
fatter tires heavier? It might seem so, but trust a scale more than
your intuition. An Avocet 700 x 32 Fasgrip tire weighs 300 to 315g.
There are fancy 700 x 25s that weigh more than that. The Avocet 700 x
28 foldable weighs between 230g and 250g; and there are fancy 700 x 19s
that weigh more.
Two-colored, dual-compound treads are popular and an easy sale.
The harder compound in the center increases wear, while the soft and
colorful rubber on the sides grips the road with eraser-like friction.
It's such a tidy package and an easy to grasp concept. I've been riding a
bike as a racer, tourist, and athletic recreational rider for 30
years, and the only times my tires have actually slipped around turns
have been on gravel, water, road paint, manhole covers, or oil. The
crashes have always been caused by bad luck, bad planning, or bad
technique, and I'm skeptical how much difference a softer rubber would
have made. On gravel, oil, paint, and manhole covers, surely none.
Maybe on a wet road, but even then, I'm skeptical. When it's wet out,
that's no time to set another PR for lean angle.
Dry surfaces are another story. I've read lean angle charts
comparing different brands and rubber compounds, but I've yet to reach
the traction limit on a single-compound tire while leaning into a turn,
and I've never seen or heard of anybody doing that. Not even fourth
hand! It may be possible that one tire grips at 28-degrees, and another
maxes out at 31-degrees, but I start to freak out at 45-degrees, and
even old-fashioned crummy tires grip at that.
Grant Petersen is a California-based member of PPTC and
founder of Rivendell Bicycle Works. Visit Rivendell Bicycles Works at