Frame flex and efficiency

"41" wrote in message
oups.com...

Philip Holman wrote:
"41" wrote in message

left BB deflection is greater, being assisted by chain tension
and conversely, right deflection diminished for the same reason.

Reverse?

No, try it.

The reason I posed this is because what you said previously sounds
like
the reverse:

#Right pedal loading always results in more deflection due to chain
tension.

Is it?a

Well, right pedal loading causes left deflection of the BB. Confusing
isn't it :-)

Phil H

wrote:

OK, so I did the same thing on my bicycle with SPD shoes and cleats,
the 50-16t gear engaged and the rear brake firmly held. Pushing down
on the right pedal and pulling up statically as hard as I can in the
seated position, I achieved a mark from a pen attached to the right
pedal on the fixed piece of paper 5mm long or 0.197". For me that's a
long way from one inch and also insignificant.

Did you try pushing and measuring on the left also?

In any case, thanks for taking the time to do the test.

5mm is less than 2% of the pedal stroke. I agree that's
not particularly significant. Of course, some people spend
big $$$ to get 1% sized effects, but that's their business.

I think you have a soft frame, literally and it was that way when new.

I'd referred to the time of manufacture only to help identify
the vintage of material it was made from. I also doubt that
it has changed noticeably since it was new.

It's not the frame I do most of my riding on nowadays.

Tom Ace