## Indoor trainer: gradient vs wattage (still don't get it)

A light bike doesn't replace good fitness.

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Sir Rides a Lot
Posts: 62
Joined: Mon Jun 02, 2008 7:10 pm
I'm in the process of buying an indoor trainer and will most likely be using it with Zwift. The main difference between a € 250 and a € 500 trainer seems to be the max wattage/ gradient simulation. I've read many different topics on this, with many people saying the max gradient is irrelevant, you can just shift to a bigger gear in order to simulate a higher gradient. I honestly still can't get my mind around this (I fully accept the fact that my mind is the limiting factor here).

I imagine the gradient as kind of a brake, which changes the resistance. Therefore I would think that a trainer simulating 10% will feel different than a trainer that can simulate 6% gradient, on which you just shift to a higher gear --> because of less momentum in de flywheel in the 10% than in the 6% trainer.

mvnsnd
Posts: 41
Joined: Mon Mar 21, 2016 8:16 pm
Look at it this way, the max gradient is a relation to the max power that can be applied with a low RPM. I assume you are talking about smart trainers? Shifting to a bigger gear to simulate gradient is more for the fluid trainers in which the faster the rear wheel spins, the more resistance the fluid unit generates.
Consider that in the real world, you can climb a hill at 300 watts and 50 rpm. You are in your small front ring and biggest rear cog. On a fluid trainer to do 300 watts at 50 rpm, you may be in your big ring up front and near smallest cog in the back. It's not really the same thing. When you consider a gradient with a smart trainer, it will estimate the power needed to advance the gradient (slope) independent of the choice of gear. So you could use either the small ring or the big ring at any cadence, and the power required would be the same.

Sir Rides a Lot
Posts: 62
Joined: Mon Jun 02, 2008 7:10 pm
thnx mvnsnd, but isn't the momentum of the flywheel different. I mean if I stop pedalling in a very high gear, the momentum will keep the flywheel turning. with a smart trainer that can simulate a higher gradient, the flywheel will stop more quickly, thus it will feel 'different'?

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