RadRover : how slim (Tires) can we go ?

[m@Robertson]

Struggling with something these charts aren't showing. I have to wonder if there's an assumption regarding the design of the tires? Consider for a second a Schwalbe Marathon with it's stiff sidewalls, and then a balloon type like a Schwalbe Super Moto-X. They both have outstanding reputations for our purposes, but I believe the 2 tires are like night and day regarding designs. The Marathon is an outstanding tire, that is generally run with twice the air pressure that the Super Moto-X (and some similar tires like the Big Apple) typically run. If you've ridden the same bike equipped both ways, the extra pressure run in the Marathons makes them feel like you're on a roller skate riding down a brick road. Remove that tire and install one of the balloon types (like the Super Moto-x X or Big Apple), and things are very noticeably smoother. Expansion joints and dried out cracked pavement area seem to disappear!

This is what I'm talking about when I say "ride". Talking about the amount of vibration transferred to you wrists and your back side as you ride on a paved road.... minimizing that vibration.

We've seen the note regarding too big a tire on a rim (the Bell shape) causing a stiff ride - assuming it would be a softer ride if the tire and rim were properly matched. So what about when taken to the extreme, where we're installing a 2.25" tire on an 80mm rim?

Well, you probably know what I am going to say on that. the ride will SUCK. Purely for the reason that there is not enough sidewall to do any level of cushioning, and you still have to inflate the tire to its higher pressure limit - or risk the sidewall not being sufficient to absorb an impact, which means your rims will take the beating directly. Net result is your body takes a pounding. My Super Moto X's on 80mm rims were *horrible*. But they were also wonderful on my Stumpjumper conversion and its Alexrims, which were, IIRC, 30mm internal. BTW the performance difference is the same for car tires. Use skinny little rubber band 30 series tires versus 50-series sidewalls and exactly the same things happen.

My Schwalbe Marathons in 700x35 (which is really a 37) were like rolling rocks. But the same tire in 26x2.00 is great (I keep it at 60 psi which is underneath its 75 max). Different bikes, different rims... this is a big part of why I have a pile of tires in my garage. Everything is different and you just have to try stuff and see.

In my experience, no two tires are the same. Continental for example, I found they're way narrower than what's indicated on the sidewall.

^^^ This. For sure. On both counts. Contis have a reputation for being undersized and I count on this when I use them in a build. But be advised they do stretch into their size in a few weeks - but are still commonly undersized a bit even after they stretch out. On my Luna Fixed, I counted on this undersizing to get them to fit into that small frame triangle and they worked great. On my Mongoose Envoy, the 26x2.15 tires were actually right on spec for the first time ever, which was a surprise. And those bigger tires (Contact Plus City flatproofs) were like rolling on rocks. I got rid of them in favor of 2.8" Vee Speedsters and loved the pillow-soft ride enough to live without the security net of the belts on the Contis.