NVV Cyclocross: Tire pressure

Tire pressure for 'cross
All you ever wanted to know...and more
Aug 1999

Introduction How hard should you run your tires? In road racing it's easy: Hard as possible, most of the time at least. In cyclocross? Not so simple. With my roadie background I used to always run high pressure--until I realized I was going slower than I expected. So I dug through the rec.bike.racing archive to find a few tidbits that may interest you.
A couple of basic issues:
- Tubulars vs. clinchers. Sewups are more expensive, harder to find, and tougher to repair than clinchers. In mountain biking there's no such thing as a sewup. But in 'cross (with its roadie background) a lot of top riders ride sewups and really swear by them, especially Tufos. The major advantage of sewups: You can run them softer than clinchers without fear of pinch flats.
- Tire width. Pressure considerations change depending on what width you run. A narrower tire has a lower volume, which means it pinches more easily at a low pressure. Also narrow and wide tires handle some types of terrain differently (mud, sand, softpack).
- Surface. As you will note, hardpack, softpack, mud and ice each have different pressure requirements. You''l have to experiment and learn. The following discussions just give you an idea of where to start. --Dave Carr

Adam Myerson
(a New England cross racer) My tires of choice are the 34mm TUFO sewups. I like them because I can run them in all conditions at different pressures and cover most of my bases. The Clement Griffo Largo (not the Griffo Neve) is good for the same reason. Unless you've got lots of sets of wheels with different tires for different conditions, it's good to go with and all around, arrow or tractor-type tread. In my eyes, the bigger the better, up to 35mm.
If it's dry and fast, you can run them hard, if it's bumpy, run them in the middle, and if it's muddy, (or icy) run them low. I vary from 60-30 lbs, depending. With a bigger tire, your chances of bottoming out are less.   The hardest I ever go is 4 bars (60 psi). At the Seattle SuperCups (where it was really muddy) I used 2.5 bars (about 30 psi) in the front and 3 bars (about 40 psi) in the back.
If you're using tubulars in really soft condidtions, you can run your pressure just to the point where you start to bottom out. You obviously can't do that with clinchers (becuase you'll pinch flat). That's why I like to run 34 mm TUFO tubulars no matter what: I can run them at 2-2.5 bars and not bottom out, or I can run them at 4 bars and have a nice, fast tire.

Mark Weaver
(a NorCal master) For offroad riding, I generally use the lowest pressure that leaves me secure from pinch flats. on rough terrain, your tires are suspension, so if they're softer, they actually have less rolling resistance. (cool, huh?).
Llikewise, in soft stuff (like that icky damp grass and stuff) lower pressure means a wider footprint, so you don't sink in so far, so you don't push so much mud around, so you go faster.    Of course, low pressure is definitely slower on pavement or real smooth surfaces, so you have to achieve a balance.
As far as I'm concerned, traction is not a big issue in cross (with very occasional exceptions). It's simply a matter of matching tire pressure to the conditions to achieve minimum rolling resistance while resisting pinch flats. I find lower pressures to work well for me on softer or bumpier ground and higher pressures to work better on smooth, hard surfaces.
In the '98 San Jose Super Cup race, which had lots of pretty soft ground, not really mud, but soft moist grass and stuff, I was using about 60-65psi on my Michelin Cross Sprint 700 x 30 (more like 35 really). It felt like I was just not moving at all in the soft stuff, which was really annoying.
The next day at the Surf City race, which also included a fair amount of soft stuff, I went down to 40 psi. This seemed to work much better for me. It seemed as though the lower pressure resulted in a larger contact patch which meant I was riding more on top of the soft stuff and pusing less of it around. There was one pretty rocky section at the Super Cup, so I'm not sure if I could've gotten away with 40 psi without pinch-flatting, but at least if I flatted I'd have an excuse for sucking.

Tom Kunich
(contributor
to r.b.r.) If you soften your tires too much they push flat and don't get any traction at all. If they are too hard the slip on smooth surfaces. You have to find your own ideal pressure for your weight and weight distribution on your bike.
I run towards the soft end of the spectrum, but some people ride with tires that are unbelievably hard and don't seem to have any problems.    If you check out the guys leading from year to year they seem to change [their tire pressure] back and forth. My guess is that it's merely something to worry about.

Dave Carr
(your faithful editor) At San Jose I used two tire pressures: 65psi or so on my Michelins, followed by 0 psi after I flatted both tires (one pinch, one thorn). On the soft mud I couldn't really tell the difference, except 0psi was a touch slower.
I always run mine pretty hard for the following reasons: (a) I can jam on the pavement sections; (b) I won't pinch as easily; (c) for just an hour I can take the pounding, especially on those wide Michelins.    I don't buy the "wide soft tires float on mud" argument. If that were true then Mark's teammate Howie wouldn't have been cursing every time he hit the mud on his fat tire MTB that he rode for a lap so the pit crew could clean his cross bike (I'm referring to the sticky soft Watsonville Surf City race in 1998).   However I do believe wide tires float on soft earth; this I've seen for myself in the old days when I rode my MTB for cross (yes, I admit...)
I haven't found the answer for that sticky stuff yet. I just get sucked down in it no matter what I wear on my wheels. The best time I had in the mud was 1997's Surf City Soquel High mudfest. The skinny stock Kendas on my Redline sliced thru the wet stuff very nicely. Floating was definitely not the way to go that day.
I saw something interesting in Velonews recently commenting on the new tubeless tires that some downhill MTB pros are using. They run them real low because they don't pinch flat. The comment was, running them low is more efficient on rough terrain because (a) when you hit a bump the tire compresses, instead of slamming you, and (b) when you roll over the bump and the tire expands again, it pushes you off. (A) I agree with, but (b) sounds like complete fantasy or at the least, an effect offset by an equal and opposite effect when you first hit the bump.

Rob Hult
(contributor
to r.b.r.) My tires of choice are TUFO prestige 30mm and 32/34mm. The 30 is relatively narrow. I've used a 28 before and never liked it much. The 32/34 is a 34mm sectional width tire with 32mm of tread.   I usually run 50-55 psi. I will go softer for mud, sand, and soft conditions. I will go harder for large sections of pavement and dry (but grippy) courses.
Rider experience and the ability to feel how well your tires are cornering, gripping, and rolling influence tire selection and pressure choices. I think this is a skill that is developed with experience. (I learned a lot from guys with many more years of racing experience than myself.) More often than not I have improved ride feel, grip, quality, and speed by making a 5 psi adjustment.
Prior to bike racing I used to be into 4WD Jeeps and mud-bogging, where I learned two philosophies concerning how to get thru mud.   The most common, by far, was the idea that larger tires "float" over mud. They give you better traction, better floatation, more tread to push on more mud, etc. Makes sense.
The second idea was to use a tall, narrow tire to get thru mud. The idea was that your tire would slice thru the mud and water at the surface while gripping on the firmer ground underneath. You also had great steering control (unlike floating tires which wandered badly). As long as the mud bog wasn't too deep, this technique worked great.   I think both can apply to cyclocross bike tires.
Another note: One of my friends was at World 'Cross Champs in Europe two years ago. At the start line a spectator reached over the fencing and grabbed his tires. He then looked up at my friend and said, "No! Stupid American," and motioned down at his tires. My friend had about 65 psi. The guy convinced him to lower them down to about 35 psi. Why? The ground was frozen like cement. This guy explained to him that you should be able to push your finger across the tire and basically hit the rim! He was serious and was trying to help this kid who was lined up at the back of the pack with all the other Americans.   Just a thought.
Another note #2: In Europe it is not uncommon to find guys running 28mm and smaller section tires. Why? They are light and roll damn fast.
Another note #3: Ask Dale Knapp. When the ground freezes, racers switch to the largest tires they can find. Some use 40's. These are the European racers too.
Another note #4: Paul Curley is famous for using a 28mm diamond tread TUFO front tire in many conditions. His race record and technique speak for itself. He is an example of the importance of having proper cornering technique.
Another note #5: Frankie McCormack's tire of choice is a TUFO Pro 28mm front and rear. This year he was questioned by a racer about his narrow tire selection. His response, "This is not jungle-cross. This is cyclocross."

Go back to the NVV Cyclocross Circuit

Introduction	How hard should you run your tires? In road racing it's easy: Hard as possible, most of the time at least. In cyclocross? Not so simple. With my roadie background I used to always run high pressure--until I realized I was going slower than I expected. So I dug through the rec.bike.racing archive to find a few tidbits that may interest you. A couple of basic issues: - Tubulars vs. clinchers. Sewups are more expensive, harder to find, and tougher to repair than clinchers. In mountain biking there's no such thing as a sewup. But in 'cross (with its roadie background) a lot of top riders ride sewups and really swear by them, especially Tufos. The major advantage of sewups: You can run them softer than clinchers without fear of pinch flats. - Tire width. Pressure considerations change depending on what width you run. A narrower tire has a lower volume, which means it pinches more easily at a low pressure. Also narrow and wide tires handle some types of terrain differently (mud, sand, softpack). - Surface. As you will note, hardpack, softpack, mud and ice each have different pressure requirements. You''l have to experiment and learn. The following discussions just give you an idea of where to start. --Dave Carr
Adam Myerson (a New England cross racer)	My tires of choice are the 34mm TUFO sewups. I like them because I can run them in all conditions at different pressures and cover most of my bases. The Clement Griffo Largo (not the Griffo Neve) is good for the same reason. Unless you've got lots of sets of wheels with different tires for different conditions, it's good to go with and all around, arrow or tractor-type tread. In my eyes, the bigger the better, up to 35mm. If it's dry and fast, you can run them hard, if it's bumpy, run them in the middle, and if it's muddy, (or icy) run them low. I vary from 60-30 lbs, depending. With a bigger tire, your chances of bottoming out are less. The hardest I ever go is 4 bars (60 psi). At the Seattle SuperCups (where it was really muddy) I used 2.5 bars (about 30 psi) in the front and 3 bars (about 40 psi) in the back. If you're using tubulars in really soft condidtions, you can run your pressure just to the point where you start to bottom out. You obviously can't do that with clinchers (becuase you'll pinch flat). That's why I like to run 34 mm TUFO tubulars no matter what: I can run them at 2-2.5 bars and not bottom out, or I can run them at 4 bars and have a nice, fast tire.
Mark Weaver (a NorCal master)	For offroad riding, I generally use the lowest pressure that leaves me secure from pinch flats. on rough terrain, your tires are suspension, so if they're softer, they actually have less rolling resistance. (cool, huh?). Llikewise, in soft stuff (like that icky damp grass and stuff) lower pressure means a wider footprint, so you don't sink in so far, so you don't push so much mud around, so you go faster. Of course, low pressure is definitely slower on pavement or real smooth surfaces, so you have to achieve a balance. As far as I'm concerned, traction is not a big issue in cross (with very occasional exceptions). It's simply a matter of matching tire pressure to the conditions to achieve minimum rolling resistance while resisting pinch flats. I find lower pressures to work well for me on softer or bumpier ground and higher pressures to work better on smooth, hard surfaces. In the '98 San Jose Super Cup race, which had lots of pretty soft ground, not really mud, but soft moist grass and stuff, I was using about 60-65psi on my Michelin Cross Sprint 700 x 30 (more like 35 really). It felt like I was just not moving at all in the soft stuff, which was really annoying. The next day at the Surf City race, which also included a fair amount of soft stuff, I went down to 40 psi. This seemed to work much better for me. It seemed as though the lower pressure resulted in a larger contact patch which meant I was riding more on top of the soft stuff and pusing less of it around. There was one pretty rocky section at the Super Cup, so I'm not sure if I could've gotten away with 40 psi without pinch-flatting, but at least if I flatted I'd have an excuse for sucking.
Tom Kunich (contributor to r.b.r.)	If you soften your tires too much they push flat and don't get any traction at all. If they are too hard the slip on smooth surfaces. You have to find your own ideal pressure for your weight and weight distribution on your bike. I run towards the soft end of the spectrum, but some people ride with tires that are unbelievably hard and don't seem to have any problems. If you check out the guys leading from year to year they seem to change [their tire pressure] back and forth. My guess is that it's merely something to worry about.
Dave Carr (your faithful editor)	At San Jose I used two tire pressures: 65psi or so on my Michelins, followed by 0 psi after I flatted both tires (one pinch, one thorn). On the soft mud I couldn't really tell the difference, except 0psi was a touch slower. I always run mine pretty hard for the following reasons: (a) I can jam on the pavement sections; (b) I won't pinch as easily; (c) for just an hour I can take the pounding, especially on those wide Michelins. I don't buy the "wide soft tires float on mud" argument. If that were true then Mark's teammate Howie wouldn't have been cursing every time he hit the mud on his fat tire MTB that he rode for a lap so the pit crew could clean his cross bike (I'm referring to the sticky soft Watsonville Surf City race in 1998). However I do believe wide tires float on soft earth; this I've seen for myself in the old days when I rode my MTB for cross (yes, I admit...) I haven't found the answer for that sticky stuff yet. I just get sucked down in it no matter what I wear on my wheels. The best time I had in the mud was 1997's Surf City Soquel High mudfest. The skinny stock Kendas on my Redline sliced thru the wet stuff very nicely. Floating was definitely not the way to go that day. I saw something interesting in Velonews recently commenting on the new tubeless tires that some downhill MTB pros are using. They run them real low because they don't pinch flat. The comment was, running them low is more efficient on rough terrain because (a) when you hit a bump the tire compresses, instead of slamming you, and (b) when you roll over the bump and the tire expands again, it pushes you off. (A) I agree with, but (b) sounds like complete fantasy or at the least, an effect offset by an equal and opposite effect when you first hit the bump.
Rob Hult (contributor to r.b.r.)	My tires of choice are TUFO prestige 30mm and 32/34mm. The 30 is relatively narrow. I've used a 28 before and never liked it much. The 32/34 is a 34mm sectional width tire with 32mm of tread. I usually run 50-55 psi. I will go softer for mud, sand, and soft conditions. I will go harder for large sections of pavement and dry (but grippy) courses. Rider experience and the ability to feel how well your tires are cornering, gripping, and rolling influence tire selection and pressure choices. I think this is a skill that is developed with experience. (I learned a lot from guys with many more years of racing experience than myself.) More often than not I have improved ride feel, grip, quality, and speed by making a 5 psi adjustment. Prior to bike racing I used to be into 4WD Jeeps and mud-bogging, where I learned two philosophies concerning how to get thru mud. The most common, by far, was the idea that larger tires "float" over mud. They give you better traction, better floatation, more tread to push on more mud, etc. Makes sense. The second idea was to use a tall, narrow tire to get thru mud. The idea was that your tire would slice thru the mud and water at the surface while gripping on the firmer ground underneath. You also had great steering control (unlike floating tires which wandered badly). As long as the mud bog wasn't too deep, this technique worked great. I think both can apply to cyclocross bike tires. Another note: One of my friends was at World 'Cross Champs in Europe two years ago. At the start line a spectator reached over the fencing and grabbed his tires. He then looked up at my friend and said, "No! Stupid American," and motioned down at his tires. My friend had about 65 psi. The guy convinced him to lower them down to about 35 psi. Why? The ground was frozen like cement. This guy explained to him that you should be able to push your finger across the tire and basically hit the rim! He was serious and was trying to help this kid who was lined up at the back of the pack with all the other Americans. Just a thought. Another note #2: In Europe it is not uncommon to find guys running 28mm and smaller section tires. Why? They are light and roll damn fast. Another note #3: Ask Dale Knapp. When the ground freezes, racers switch to the largest tires they can find. Some use 40's. These are the European racers too. Another note #4: Paul Curley is famous for using a 28mm diamond tread TUFO front tire in many conditions. His race record and technique speak for itself. He is an example of the importance of having proper cornering technique. Another note #5: Frankie McCormack's tire of choice is a TUFO Pro 28mm front and rear. This year he was questioned by a racer about his narrow tire selection. His response, "This is not jungle-cross. This is cyclocross."