FlamsteadHill

In the last few months as I've perused forums and articles I've seen many references to the fact that nowadays you don't need to let up the pressure when shifting. I still have been letting up some, because it just feels wrong.

Last night I took delivery of my Trek Domane SL5. Full 105 groupset. In the manual (which is generic for Trek, not specific to the model) it says to let up on the pedal pressure!

So why do so many people say you don't have to? Or is this all a relativity thing? i.e. 30 years ago you had to let off 90% and now you have to let off 50%. So compared to ages ago you're "not letting off pressure" (can now apply 5 times the force compared to before) but for those that have never ridden any bike ever, you're "letting off pressure"?

shelbyfv

I've missed those many references but it seems to be true with electronic. Maybe that was what you were reading about.

europa

In days gone by, if you didn't ease up on the pressure, the chain wouldn't shift. As the companies have learned more and improved things, that requirement has eased and maybe with some systems, you don't have to ease off... as much. Just experiment with your bike and find out what works. You can't hammer a bike with an armoured fist, you always have to use a bit of mechanical sympathy and part of the joy of cycling is learning how to work with your bike to get the best result.

(and for the little it's worth, Schleck didn't suffer a mechanical in 'that' incident, he was just ham fisted changing gears)

fietsbob

Its like the difference between lifting a 5 gallon bucket that is full, vs lifting one that is empty.

which one will fatigue more after repeatedly lifting it 6 hours?

the engineers by shortening the teeth , skipping one or so, and adding ramps and pins have made the mech work faster.

and by redesigning the chain , reduced its lateral stiffness..


Shifting under a load will shorten the drivetrain wear life, you may be fine with more frequent replacements..








.....

billyymc

The only time I do this is on a climb, and it's such an imperceptible and quick action that you wouldn't notice it if you were observing it. Not sure I NEED to do it, but it's habit so I do.

Never feel the need to do it on the flat or even a minor grade.

Sy Reene

Isn't that the point of tight gearing.. uninterrupted cadence and power application when accelerating or decelerating?
why does accelerate have 2 c's and decelerate have only 1 ?

TimothyH

Bikes were made to ride, not worship.

If you need to shift under power then do so. Just ride. Don't worry about it.


-Tim-

AndreyT

Um... What derailleur specifically are you talking about? The front and the rear are fundamentally different in this regard.

The RD does not "see" the load on the chain at all. You can shift it under any load. Light-loaded shifts will generally be smoother, but it will still shift under any load. If your RD has poorly adjusted indexing then trying to shift under heavy load might make the chain to "slip" mid-shift. It is unpleasant when it happens, but it is not a big deal.

The FD is a completely different story. It won't shift well (or at all) under load. So, yes, you have to unload the chain to perform a good FD shift. Modern electronic FDs might be better at shifting loaded chains, since they can "adapt" to the load and compensate for it by overshifting. But even with an electronic FD you can always load the chain so heavily that the FD won't be able to do anything.

AndreyT

These words are formed by adding different prefixes to the same root. In this case the original root is celer. That's where the common 'c' comes from. The former is formed by adding the 'ac-' prefix while the latter uses the 'de-' prefix.

In other words, two 'c's in 'accelerate' are not related to each other at all. They have different origins. It just so happened that they ended up next to each other.

FlamsteadHill

True. I was speaking of the RD

I see your point, but if shifting under load is not as smooth, there must be some negative effect as a result. OTOH, "not as smooth" is rather subjective, so maybe that would translate to a chain lasting only 4900 miles instead of 5000.

Love that phrase. It's what I generally use in cases like this, just hadn't thought of terming it so expressively.