This is my first post to this newsgroup and I thought I would share my experience over the last 10
years with fat, treadless tires.
I've spent a bit of time over the last couple of weeks looking for replacements for my Avocet
FasGrip tires I have mounted on a Trek 7000 mountain bike. The tires are 16 x 1.9 front and rear and
mounted on Matrix SingleTrak rims that measure 24mm at the widest portion. The tires are rated 40-85
lbs. but I have run them as low as 35 lbs. without rim damage on tricky, loose trails and have run
them on the road as high as 90 lbs. for extended distances on pavement. I weigh about 200 lbs.
I wondered what has changed since I bought these tires over a decade ago. (Yes, it's true, I haven't
been riding a lot in the last six years or so). So I've read a lot of old Usenet postings on the
subject of slicks and that's what prompted me to write this post. I feel like a lot of people are
prejudiced against slicks because it doesn't seem intuitive that they should work very well under a
wide range of conditions. My experience is that a slick works amazingly well under all sorts of
conditions (with a few limitations) but only if the tire is plenty wide. A lot of people try slicks
in a 1.5" width and are not that happy with their performance on softer, slippery surfaces. I have
found that the extra width of a 1.9" slick makes a world of difference. A wider tire can be run with
lower pressures without fear of pinching or rim damage. These lower pressures make the tire perform
like an even wider tire and gives plenty of "float" in softer surfaces.
Even with lower pressures, a wide slick will pedal easier and faster than a knobby pumped up hard.
To illustrate, try this experiment. Mount your knobby equipped bike in a work stand or turn it
upside down. Now put the bike in high cruising gear and turn the pedals at a nice cadence. Notice
the breeze created by those knobbies. Notice how much energy you need to continuously add to the
pedals to maintain a constant speed. The knobby is essentially a big fan and not just the rear one
but the front also. So double the pedal energy you feel to approximate both tires spinning. Remember
the aerodyne by Schwinn? Now thy the same thing with a fat slick. Notice how little energy is
required to maintain a constant speed? That, not rolling resistance, is the biggest difference in
pedaling efficiency between a slick and a knobby. But the rolling resistance difference is
significant also, even if the slick is run with less air pressure. So fat slicks can provide a
smoother ride which is important to many people who ride for fun and don't have or want
full-suspension as well as a faster ride.
I have even found the slicks to outperform knobbies (of the same width) in certain loose conditions
like deep or loose gravel and even certain types of sand, wet and dry. I believe this is because the
knobbies tend displace individual stones, disrupting the surface, while the fat slick can compress
some materials which can make for a more stable base. I have seen this many times climbing gravel
with others who use knobbies. Dry fine sand can be a problem though. I have often wanted to try even
wider slicks for certain conditions.
For steeper, more technical rocky trials the slicks often give more consistent and predictable
performance. I believe this is because a knobby can hook up on irregular edges of the rocks, roots
or bark but give away suddenly and unexpectedly if the knobs slip off the surface irregularity. This
may not be a big concern as the knobby will likely hook back up on something else soon. But the
slick gives smoother, more predictable traction and performance which I really enjoy. In comparison,
the fat slick is more predictable and smoother, if it does come off the edge of an embedded trail
rock or root and slides a short ways down the face it will give predictable friction during the
slide helping the rider to relax .
On wet pavement nothing grips as well as a slick that is inflated to road pressures. Bicycles have a
high enough loading per area of contact patch that hydro-planing is not a problem. The wider contact
patch of a wide slick (compared to a narrow tire of any type) gives a smooth consistent traction at
high lean angles that is not as likely to surprise the rider by slipping out due to the traction
"averaging" of the larger contact patch. It's supremely fun to eat up fast pavement corners, wet or
dry, with wide slicks with confidence and without scrubbing off a lot of speed as treaded tires will
do. If traction is lost while leaned over in the wet (say an unexpected white vinyl pavement marking
or a smooth metal manhole cover that is unavoidable) the slick is less likely to throw the rider in
highside when it hooks back up because there are no knobbies to tuck under, bite temporarily and
then release suddenly, just smooth predictable traction.
The weak link of fat slicks is wet leaves, organic matter, mud and deep, dry, fine sand. If you are
a weekend warrior who thrives on going and getting muddy and your favorite trails are high in wet
organic slime and downhill speed is the name of the game, then knobbies are for you. If you
primarily ride on firm surfaces, wet or dry pavement and rock, packed dirt, wet sand beaches, grass
and gravel and you like to cover a lot of ground, appreciate a smoother, quieter more comfortable
ride then you owe it to yourself to try fat slicks as a good all-around tire choice. You may never
turn back. Pump them up for covering the distance and let them soft for more technical endeavors or
to increase the ride comfort, the choice is yours.
Mike Mullen