I beg to diff-er

Sir,

I thought that A Shadow on the Mountains (May) was a splendid write-up, but one error must not be allowed to be perpetuated in Motortsport. “Lock one side of the diff, the other will go twice as fast.”

Not so! The magic diff will take care of that The ratio will remain the same. You can’t believe it? Jack up the drive wheels and try it.

I am, yours, Etc

Bob Bradley, Oxford