mtbtires.com

“… i guess though tire selection is a personal thing and besides terrain perhaps even riding style can determine whether you like or dislike a tire…”

He nailed that one and it is especially riding style that comes into play.

The sidewall flex/squirm is a very personal thing. Terrain, rider weight, type of riding and riding style all contribute.

I tend to like rounder profile tires for the way they track (straight line stability) and change direction. A narrower rim gives most tires this profile.

Some say a wider rim reduces pinch flats. I can not say I have noticed much difference and if anything, I pinch more with the same tire on a wider rim. Especially the case if it is a narrowish tire on a wideish rim.

I also like lower pressures for the way it lets the tire conform to the terrain and not be deflected as easily. Give a better feel and feedback. Too high a pressure and the tire bounces/deflects off of bumps/rocks/roots in strange directions.
I do feel the sidewall flex - in a good way. It is telling me the tire is working. The tread and casing conforming. Giving me info on the available grip. If I feel the tire “wallowing” or folding the pressure is too low. The pressure also needs to be high enough to support the tread blocks and not so high that it does not let the tread “work.” I know lighter riders than me that can not stand the “squirm” of tires even when running higher pressures than I use. It may actually be the tread flexing or slipping that they are noticing.

Every tire has a pressure sweet-spot where this balance takes place and varies with the rider, bike, rim and terrain. This brings up an mostly overlooked part of bike setup and tuning:
Many hours and dollars are spent on suspension setup. The affects of tire pressure on the suspension is largely ignored. Change the tire pressure and you may need to change the shock damping. The tire construction (tread design, rubber compound and casings) itself changes the handling and can require a suspension adjustment. I have ridden tires that are just plain awful on a rigid bike and shine on a boinger.

(adapted from a mtbr.com post)

They are just rubber and nylon treads. Why do they fascinate me so much?

So many ways to put them together.

Such a light and flexible structure.

But once attached to a rim and filled with air they can support great loads and take incredible abuse.

The only thing that connects bike to ground.

Without the tires a bike is useless.

After about 25 years of mtb tires people are spoiled with the selection we now have. It did not happen overnight. We did not even get truly huge 26″ tires until ~10 years ago. Most of the 29er tires currently available are wider than the biggest 26″ tires available just 15 years ago. Three exceptions come to mind: Ritchey Z-Max 2.35 and Specialized Extreme and More Extreme 2.50 (designed by WTB). All about the same actual size and light XC casings.

The 29er tire market is still only ~7 years old. Most of the tires we have happened in the last 2-3 years. The changeover is happening but it is a little more complicated (and much lower volume) than the music industry moving from LPs to CDs to MP3s. The internet age motto “instant gratification is not soon enough” just does not work when the final product is not 100% electrons.

(adapted from a post on mtbr.com)