Ouch… Stupid Air Pressure


The group gathers around initial tree, one of the High Knob landmarks.


Heavy leaf coverage made the trail a bit more dangerous then usual.


Standard pre ride pose. Was to sore to mess with a post ride pose.

IMG_0003 IMG_0005 IMG_0007 In an attempt to have flat-free mountain bike rides I’ve been experimenting with higher air pressures.  As you probably know lower pressures ride much better on the trail then higher pressure.  Low pressures conform to the uneven surface of the trail and lower rolling resistance.  The problem is when you get so low you get pinch flats with tubes or a tubeless tire that rolls off the rim.

I realized that I could ride through stuff far more consistently and with much more comfort when my tires were low, my strategy basically became NEVER AIR UP THE TIRES.  This would be fine but tires slowly loose pressure.  This led to a string of pinch flats and blown off tubeless tires.  I decided to calibrate my pressure and started with 40 pounds.  Problem is that I think my floor pump’s gauge is off.  When I compare my 40 pound tires I get different pressures on every gauge, anywhere from 40-55 pounds.

Yesterday I rode with my tires probably at 50 and on the first turn in the trail I got chucked off my bike by a small and insignificant rock, it was a slow fall in the middle of the turn and I immediately let out some air and it seemed better. I was riding alone and taking it easy though.

Today on a group ride we were barreling down a high speed downhill section.  I was third in line and I guess I didn’t see a rock that was buried under some leaves.  When my front wheel hit it I knew immediately that I had too much air in the tire.  The sensation is much like dribbling a basketball of an errant rock on a playground court, you expect it to return to your hand it mysteriously flies out of bounds.

My front wheel flew out of bounds, which was sideways into the high side of the benchcut.  I found myself crumpling down and my knee came to an abrupt stop on a rock half buried in the trail.  I looked around and saw that I had hit the only rock I could see both ways on the trail.  I looked at my knee and saw that it was banged up pretty bad and the wind was knocked out of me so I had the privilege of laying there gasping for breath and trying to get my foot unclipped as everyone came to a stop behind me.

I normally bounce up from crashes laughing, even if they hurt but I sat there on the ground for several minutes before I could get up and continue.  Surprisingly carrying on with the ride caused little pain.  We have a theory on this, your body realizes that it had little choice, you are amped up and the inflammation and swelling is mostly delayed until you get to a safe place you can stop.  Then your body says, “Allright moron, you can move if you want but its going to hurt, quit doing stupid stuff.”

After the wreck I release air pressure from tires until they felt a bit squishy, but not as low as I was running them when they pinch flatted.  I had a bit more control the rest of the ride and avoided a second basketball bounce effect

Other then my little accident we had an awesome Sunday ride, 7 riders and the trails were mostly dry and fun.  I was able to ride this November ride in shorts.  I was riding the Bandersnatch which is working pretty well, or was until the Bottom Bracket bearings went out about halfway through the ride, causing my crank to be bouncing around in the BB.  I’ve been thinking ever since I got the Bandersnatch working again that it felt like I was pedaling much harder then my apparent speed would indicate.  Maybe it was the bottom bracket.

So what have we learned from today’s crash.  I’m going to buy a small gauge and figure out how much pressure is really in my tires, then I’m going to see how low I can get it until I get a pinch flat.


About Matt Gholson

Cycling, school teaching, husband.
This entry was posted in Barn Door Cycling, Bikes and components, Mountain BIking, Rides and tagged , , , , , , , , , , , , , , , , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s