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I've been looking into pedal kick back ready for a possible new bike build. Like many, I've started off by reading and watching the mathematical analysis of it but the most interesting comments on the subject to me, are from Steve Matthews at Vorsprung who suggests it's not chain tension directly along the drive line. Pink Bike Huck to flat in which all the chains on the top side bounce around like crazy in what must be the best example of slow forward velocity with maximum shaft speed. Recently, Cass Lab on YouTube set up a data logger and found that he was recording more false positives than true perceptible kick back events.</p>
I've only started pondering this as I was wondering if an instant engagement hub would have a negative affect on a full suspension bike and I'm inclined to think it would not.
Anyone interested in getting geeky about the subject?
I would first need to know what pedal kickback is!
My Patriot has a very much rearward axle path which results in lots of pedal kick back whilst climbing. It's very noticeable but does it matter? Not really! Just feels different, but still works.
While climbing, isn't it called anti squat?
That Cass Lab video is great, impressive work!
While climbing, isn’t it called anti squat?
Yes, or around the turn of the century it got called ‘dig in technology’ to enhance power transfer and climbing efficiency 😀. I had a Marin Mount Vision on which pedalling extended the rear suspension very noticeably but I never felt it whilst freewheeling.
The only time I’ve obviously noticed it was landing a jump badly at quite low speed. That was on my Spitfire which had high anti-squat at sag but decreasing through the travel.
Most full-sus bikes now have fairly high anti-squat - gone are the days of big differences. Similar to how most linkages now are a bit progressive or more progressive. Go back 10-15 years and you could buy bikes with no anti-squat and regressive leverage!
If you swap to a smaller chain ring you get more anti-squat and more pedal kickback.
Or a smaller chainring means using a smaller rear cog which would, in theory, reduce kick back. In fact, Rulzmann recommends smaller chainrings to reduce kick back for that reason. Having said that, taking the chainring further below the instant centre does increase anti squat.
Yeah well hmm...having ridden a bunch of HL bikes and then going to a single pivot, I occasionally used to feel something that I assumed was kickback but who knows. It was typically on a slower, techy manouvre - maybe a tight turning drop - when I felt it, and then instantly forgot about it as the next obstacle loomed. I tend to descend in a highish gear for stabilty and to pump through chossy lines which might have made it more noticeable. I'm guessing the same thing was happening on all my bikes but not as noticeable on the hl's. Hub was a multi pick up thing fwiw
But i'm just a confused bikeist so who knows?? It certainly wasnt a regular occurrence
I notice it most when pedalling up steeper, lumpier terrain. The chain is already under loads of tension; when the back wheel hits a square-edged bump and the suspension compresses, I definitely feel it stall my pedalling. Doesn't happen on the hardtail. In this scenario it wouldn't matter what the pick-up speed was.