Mountain Gear

Tech FAQ: Should you ride wider or skinnier in the mud?

LZ uses skinnier tires to cut through the mud down to where the traction is, rather than wide tires with low PSI and float on mud without traction

Editor’s note: Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn.

Dear Lennard,
Fantastic stuff on road tires. You really turned me around years ago on pressure, and now after reading you and Nick Legan the past few years, I’ll for sure be migrating back to 25C road tires.

My one question concerns mountain bike tires in mud.  I’ve read that one should actually pressure up for mud.   I’m guessing the theory is that unlike sand or snow, you don’t want to stay on top, because it’s too slippery.  I get the impression the higher pressure is to help dig down through the mud to find traction.  Does that make any sense?  Any thoughts on mud and mountain bike tires?
— Steve

Dear Steve,
Yes, that makes sense.

It’s what I learned from Tom Ritchey and is what I still practice — and what old Willys Jeeps did — use a narrow tire at high pressure that digs down to get traction. It’s the opposite of what most cyclocross riders do. I can’t understand that. There’s no reason for the suspension that a soft tire provides, as the surface is soft. And mooshing around on the top with a squishy tire hardly seems like the way to go to me. You still have to support the same amount of weight, so the contact patch will be smaller and the amount of force going into a smaller area will be higher, which should get better traction in deep mud.

On the other hand, what do I know about mud? I grew up in New Mexico and live in the Colorado Front Range; neither place is known for its mud. And there are countless guys who ride faster than me in mud.

However, I think this same philosophy applies to riding in snow, and I have lots of personal anecdotal evidence to indicate that it works better on snow to have a narrower tire at higher pressure. In ‘cross races and ‘cross training sessions in deep snow, I regularly drop buddies of mine who normally trounce me in ‘cross races. They tend to be riding 34mm tires at perhaps 25psi, I’ll be on 32mm tires at 35psi and will ride away from them.

Being well over 50 (next year I’ll be the young guy in 55+!), I don’t have that much power anymore, so I depend on traction to get me through places I might have been able to just power through 30 years ago. It’s similar to the old Willys Jeep I had in high school that had skinny tires pumped up hard and a super low-power 4-cylinder engine. I didn’t drive much in the mud, but I drove it a lot in snow, and I would merrily cruise past 4-wheel drive vehicles with big tires that were stuck in drifts.
― Lennard