Accessories Bicycles Parts Specials Tools

Search sheldonbrown.com and sheldonbrown.org

@sheldonbrowncom
More Articles by Jobst Brandt
Next: Patching Tubes
Previous: Tube Failure in Clinchers

spoke

Subject: More Flats on Rear Tires
From: Jobst Brandt
Date: January 22, 1998

Many sharp objects, especially those that lie flat on the road like nails and pieces of metal, more often enter rear tires than the front tires. That is because the front tire upends them just in time for the rear tire to be impaled on them.

For example, nails seldom enter front tires. When dropped from a moving vehicle, nails slide down the road, and align themselves pointing toward traffic, because they prefer to slide head first as they would when laid on a slope. The front tire rolling over such a lengthwise nail, can tilt it up just in time for the rear tire to encounter it on end. I once got a flat from a one inch diameter steel washer that the front tire had flipped up so that the rear tire struck it on edge. When following another wheel closely, the front tire can get the "rear tire" treatment from the preceding wheel.

The front wheel set-up effect is especially true for "Michelin" wires, the fine strands of stainless wire that make up steel belts of auto tires. These wires, left on the road when such tires exposes their belt, cause hard to find slow leaks almost exclusively in rear tires.

When wet, glass can stick to the tire even in the flat orientation and thereby get a second chance when it comes around again. To make things worse, glass cuts far more easily when wet as those who have cut rubber tubing in chemistry class may remember. A wet razor blade cuts latex rubber tubing in a single slice while a dry blade only makes a nick.

As for pinch flats, aka snake bites , they occur on the rear wheel more readily because it carries more load and is uncushioned when the rider is seated. The rider's arms, even when leaning heavily on the front wheel, cushion impact when striking a blunt obstacle.

Jobst Brandt

Spoke Divider

See also Sheldon Brown on Flat Tires

Spoke Divider

More Articles by Jobst Brandt
Next: Patching Tubes
Previous: Tube Failure in Clinchers

Spoke Divider

Spoke Divider

Articles by Sheldon Brown and others
Harris
Home
Beginners Brakes Commuting
Lights
Cycle-
Computers
Do-It-
Yourself
Essays
Family
Cycling
Fixed Gear
Singlespeed
Frames Gears &
Drivetrain
Bicycle
Humor
Bicycle
Glossary
Bicycle
Links
Old
Bikes
Repair
Tips
Tandems Touring What's
New
Wheels Sheldon
Brown

Accessories Bicycles Parts Specials Tools

Harris Cyclery Home Page

If you would like to make a link or bookmark to this page, the URL is:
http://sheldonbrown.com/brandt/rear-flats.html

Last Updated: by Harriet Fell