Thought I’d share a little DIY project I just completed to add/increase resistance on aluminum rollers. I came across this simple idea when I researching ways to increase resistance for my FTP Test earlier this week as I was afraid of spinning out. I found 2 ways; first was to fold or roll an old towel under the roller(s) to which I did as it was the simplest & easiest to do & worked fine. The 2nd method required a few more parts but is a better longer term solution. It’s also my understanding a few manufacturers used to make something similar and sell as an accessory however have since discontinued them.
I got the idea from this YouTube video - https://youtu.be/75W2nL-CLdQ
All I had to purchased was 1 piece of angle bar and 2 x 1.8" long Rare Earth Channel Magnets. I’m in Toronto Canada, cost me $30 for the magnets & $10 for the angle bar, already had the clamps.
Just installed them on my rollers and did a quick test. I have Shimano Ultegra 8000 group set with 50/34 11sp. In big chainring and 19 tooth (5th cog) down from largest in rear WITHOUT magnets at 75rpm I was pushing on average 90w, then added the magnets same gearing and cadence I 'm now pushing around 193w - that huge! And most likely exponential as you move up through the gears and the rollers spin faster.
Here’s a few pics of my set up
Hope this helps, any questions just ask it’s a very simple & slick little mod.