Kevlar vs. Cotton, How To Tell The Difference?

[ModelTWoods]

I have a set of transmission bands that were taken out of a running car that stiil look usable. I was told that one of the three bands is a Kevlar band and the other two are cotton. since ther is no name on the bands that I can see as they are installed on the metal bands, how does one tell the difference? What do you look for?

[Allan]

The ends of most Kevlar linings have been treated to stop them fraying. This makes those edges feel really hard. Cotton linings are much more forgiving and will be softer. Prod those with a blunt point and they will give somewhat, whereas kevlar is much tougher and will not yield to prodding in the same way. You might prise the suspected kevlar lining up off the band between two rivets and see the oil stained but still yellow colouring of Kevlar bands.
Hope this helps.
Allan from down under.

[Steve Jelf]

Fresh Kevlar is light yellow.

This Kevlar lining (damaged by a bad drum) has turned light gray in oil.

Used cotton linings are dark brown.

Cotton also rots.

[ModelTWoods]

Thanks, Allen and Steve. I will try to look at the backside of the linings as best I can, but the linings have been previously installed; are oil soaked (although they are dry to the touch, now); and definitely not rotten, so looking at the ends and the backside may be my best bet. On the same subject, what should be the expected life span of original Scandinavia linings. I have a second set of lined bands that were lined back in the late 1960's when my Grandfather's coupe was originally restored. I know that they are cotton linings.They still look great. I would estimate that they probably only have 500 miles on them in 50 years and all of those miles were accumulated in the time period from 1970 to 1985; None since.

[Steve Jelf]

They still look great.

My NOS tires looked great, too. Like new. They didn't last 500 miles. I realize rubber and cotton are different, but cotton deteriorates with age too, as that last picture shows. If you use them, check them often.

[Thorlick]

“This Kevlar lining (damaged by a bad drum) has turned light gray in oil.“

Steve you really gave me a chuckle with that one... generally the Kevlar causes damage to the drum first, which then causes collateral damage to the band lining!

IMHO and experience, TH

[Allan]

I have used Kevlar bands from right back in the days of Custom Friction Company composite bands with the cotton and later synthetic backing. The only trouble I had with those was drilling the countersinks for the rivets heads in the linings. Then came the woven Kevlar linings which are fitted to the bands in exactly the same way as Scandinava/Ford cotton linings. Some will argue that Kevlar generates heat which will crack drums. Others will argue that the heat is created by poor driving technique involving excessive slipping of the bands. The only band which should ever slip is the brake band, so cracked, delicate/thin, reverse drums should not be blamed on Kevlar band linings.
Changing worn bands is such a pain in the butt, especially if done in the car by removing the hogs head. Anything which prolongs band life wins hands down for me. Driven correctly, with respect for a T's foibles and limitations, they are a boon. Abuse them, operate the car incorrectly, drive on the brake like you do in a modern car, and they may , or may not, cause some damage.

Allan from down under.