Trainers: real meaning of max slope/gradient?

Triathlon Forum
1

Hi folks,

does anyone know what the “max slope” of a given smart trainer really means? Or better yet, how is that number calculated? I assume it is the max resistance (in watts) that a trainer can produce against your effort, and lots of calculations are done based on speed, average rider weight, and incline to determine how much resistance a trainer needs to simulate a grade of 3%, 10%, 15%, etc.

Just throwing out numbers: my trainer can simulate up to 10% grades, but lets say what that really means is that it can generate up to X watts resistance (lets say 200w as a placeholder). I assume 10% is the estimated grade that 200W drag simulates for the average rider (90kg?).

What I am actually trying to sort in my head is if being a lighter rider actually increases the grade/slope range of the trainer (lighter rider, less work to go up hill, thus less effective slope), and vice versa if you are a big moose.

thanks for any thoughts.

2

It’s a bad metric. What it is trying to express is max resistance at low wheel speed. A lot of trainers struggle here. When you are simulating hill work, you want a trainer that can produce high resistance while you have the bike in in an easy gear and are pedaling at a low cadence.

3

Thanks, makes sense.

I ran some numbers on a calculator for this kind of thing.

At 15km/hr a 130lbs rider (add 16lbs bike) needs about 305w on a 10% incline.

At the same speed, a 155lbs rider needs closer to 350w at 10%.

The 3 lbs i cut out of my climbing bike (13lbs) is good for 5-6w at my weight (130lbs)

4

It’s meaningless. But if you download the FE-C specs it does reference a rider with a certain weight and that specs should be normalized to this. Whether any manufacturers actually do take the FE-C specs into account for any of their products, I doubt it.

Doesn’t stop reviewers from parroting their meaningless specs though.

5

Finally some mathematical proof of why I suck on long climbs… 180lbs me + 20lbs bike = ungodly amounts of watts needed haha

6

Hahaha. If it makes you feel better, my max power is pretty low.

7

As I remember well, not sure if this is industry standard, Tacx’s max slope is for 75kg rider plus 10kg bike.

8

Just reread the specs. Default weight assumption for Fe-C is 75 kg and 10 kg if not otherwise configured . There is no standard for max slope.

There is a standard for max resistance, specified in Newtons and it is stated that this may be dependent on speed. The industry will be as vague as it thinks it can get away with, so I wouldn’t trust stated specs from any manufacturer.

9

Doesn’t stop reviewers from parroting their meaningless specs though.

Meee-owww… The manufacturers publish specs, reviewers mention these specs. This triggers you? If you know of a better way to communicate these specs or trainer details, let’s hear it. Let’s do things better.

I’ve also discussed this topic and given a few scenarios with different weights as it relates to gradient simulation indoors… with on-bike examples. https://www.youtube.com/watch?v=edJI8A8SMso