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MrSteve's picture
Suspension and Power

Mr. Tolhurst, you may remember my question, quite a while ago,
about experimenting with my Sofriders' rear suspension by turning it into a hard-tail.

I took your advice and replaced the stock sprung shock with a length of hardwood dowel.

The stock comfort disappeared, of course, but I did notice that the bike
was moving more efficiently... almost as much improvement as Jphipps notes.

My takeaway from the experiment was to reinstall the stock shock and crank up the spring preload to the
point where the spring barely sags under my weight.
Sharp road shocks are still absorbed by the rear suspension, but the bike has most
of the performance gain it showed when it was a hard-tail.

How come?
Why does the shock absorb power?

I guess it's during upper-body involvement, when the arms and/or shoulders
are putting power into the bike.

See this for yourself:
with your bike held upright in either a stand or a trainer, lay back into
your seat.
Now, with your full weight supported by both the seat back and the seat proper,
push against the handlebar.
Push, push-pull or just pull.
You'll see that you're either compressing the rear spring (pushing on the handlebar)
or you're relieveing the load of the rear spring (pulling on the handlebar).
The spring in the rear suspension may be soaking up some propulsive effort
from the upper body.

The bad news, is that watts may be dissipating in the suspension, rather than being
used for forward propulsion.

The good news is that it's not a problem, just cruising along, pedaling with your legs only.
And comfort.
Comfort is good, in the long run.