Hal Davis wrote:

> When the tire on my Nelson-Wiggen became stretched to the point where
> it was loose on the driven wheel I simply replaced it with an "O"-
> ring obtained for a couple of bucks at the local machine supply outlet.

I also have replaced these tires with "O" rings, but although Hal makes
no mention of any problem with those he has used, I have not found them
to be at all satisfactory.  They emit extremely loud squealing noises
which I have not been able to cure with rosin, belt dressing, sandpaper
or anything else I have tried.  I have concluded that the modern "O"
rings I have been able to find are made of some kind of neoprene whose
composition allows it to vibrate sonically as it stretches and slips.
Maybe the issue is silicone rubber vs. neoprene?

If anyone knows which types of rubber are likely to squeal and which
not, please let me know so I know what to specify when ordering!

Many thanks

Larry Broadmoore