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Rocker plate effect on power: Positive or negative?

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Rocker plate effect on power: Positive or negative?

Old 01-11-21, 04:04 PM
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Rocker plate effect on power: Positive or negative?

Before I installed a rocker plate under my trainer, I worried that the side-to-side action of the plate might dissipate the power I attempted to put to the pedals. I tried researching the subject, but couldn't find anything conclusive.

My first two rides yielded surprising (at least to me) results. My average watts went up, not down, and I recorded personal-best times on two Zwift routes. So I'll ask for your personal observations on the subject. When you went to a rocker plate, did your power output suffer, soar or stay about the same?
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Old 01-11-21, 04:23 PM
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Where would the power be going? The only way to dissipate power would be to convert it to heat. If you're losing 50W while sprinting for 30S the rubber feet (or whatever is flexing) would heat up measurably.
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Old 01-11-21, 04:43 PM
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Originally Posted by gregf83 View Post
Where would the power be going? The only way to dissipate power would be to convert it to heat. If you're losing 50W while sprinting for 30S the rubber feet (or whatever is flexing) would heat up measurably.
Fair enough. From a physics standpoint, that makes perfect sense. That said, how would one account for the apparent increase in power I experienced? Most of the time I average about 122 watts for those rides. With the rocker plate, I averaged about 134.
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Old 01-11-21, 04:51 PM
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Sorry, I didn't read your post close enough. I assumed you were talking about sprinting. The slight difference in power you're talking is likely just normal day to day variability. You may feel a little more comfortable if there is a bit of give but I would be surprised if that was a repeatable, consistent improvement.
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Old 01-11-21, 05:00 PM
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Better ergonomics, and a (slightly) more realistic pedal stroke from the lateral flex of the rocker. When I put the Kickr feet on my, uh, Kickr, I noticed an instant increase in perceived comfort. I got used to it after about three sessions. Now I expect it, and I’m looking for more flex but I don’t find the current rocket plates worth the money at this time. Building my own is quite possible, but I haven’t found a design that gets me interested yet. I’d love a fire/aft with side-side flex if I could source materials for under $250 and it was a solid, reliable design that truly works.

Short answer: I believe a rocker can increase efficiency and power. (Poor design could probably do the opposite, too.)
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Old 01-11-21, 10:01 PM
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I think in general it's more comfortable so your average power would be higher. I haven't gotten comfortable standing up yet, I just did my second ride with mine. Haven't sprinted yet because of that. I think I would have trouble putting out the same power sprinting until I improve my technique
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Old 01-13-21, 10:21 PM
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When one stands out on the road, the right bar goes up as that pedal goes down. To rock the bike in this fashion, one has to pull up slightly on the down-pedal side. Thus one's upper body contributes to the power produced. People don't normally rock the bike while seated, so if you're seeing that, no idea not already brought up.
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Old 01-16-21, 12:05 PM
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Originally Posted by Carbonfiberboy View Post
When one stands out on the road, the right bar goes up as that pedal goes down. To rock the bike in this fashion, one has to pull up slightly on the down-pedal side. Thus one's upper body contributes to the power produced. People don't normally rock the bike while seated, so if you're seeing that, no idea not already brought up.
I have been doing a lot more standing on the pedals this week, doing climbs on Zwift, but it's very different from how you do it on the road. For one thing, on the road you have to splay your knees a little bit to avoid hitting the rocking top tube, whereas on the trainer it's more efficient for them to track straight. On the road, my upper body tends to stay straight up, while on the trainer I rock my shoulders side to side.

Regarding seated power - I wonder if the bike rocking just a bit is making the power more even all the way around the pedal stroke? On the road we spin circles because if we mash each downstroke the bike wobbles unpleasantly. On a fixed trainer, the bike doesn't rock, so we end up mashing. Allow the bike on a trainer to rock and maybe you go back to spinning circles?
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Old 01-16-21, 12:16 PM
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There are saddle pressure sensors and people have done tests with rocker plates. It reduces pressure hot spots. I noticed with the rocker plate that if I'm seated with relatively low cadence it rocks more than I would expect on the road. It's just physics, the forces are different.

I think most people have something like 5% higher ftp while standing. I imagine it's because you can engage your upper body more. Of course, that has to be trained. One year I emphasized standing a little too much on the trainer and couldn't climb in the saddle nearly as well.
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Old 01-16-21, 09:10 PM
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Originally Posted by genejockey View Post
I have been doing a lot more standing on the pedals this week, doing climbs on Zwift, but it's very different from how you do it on the road. For one thing, on the road you have to splay your knees a little bit to avoid hitting the rocking top tube, whereas on the trainer it's more efficient for them to track straight. On the road, my upper body tends to stay straight up, while on the trainer I rock my shoulders side to side.

Regarding seated power - I wonder if the bike rocking just a bit is making the power more even all the way around the pedal stroke? On the road we spin circles because if we mash each downstroke the bike wobbles unpleasantly. On a fixed trainer, the bike doesn't rock, so we end up mashing. Allow the bike on a trainer to rock and maybe you go back to spinning circles?
Yes, that's interesting. I've noticed the same things myself, the few times I've been on a trainer.

I've been watching riders much better than myself from the rear for a long time. My observation is that less movement is better. On the road, I try to keep my knees above the pedals and rock the bike just enough that my knee barely grazes the top tube. One wants to keep one's physical mechanics efficient and unstrained. Probably one does rock the upper body instead of the bike when on the trainer, trying to add that upper body force to the pedal stroke.

On my rollers, the bike stays still as does my upper body. No motion from either, even doing intervals. When I started doing long (90"-120") Z2 roller rides, 70-75% FTP, my hip flexors were pretty sore for a couple of weeks, but not anymore. One definitely doesn't want to rock the bike while seated. I know a really good randonneur who does that. He had friction sores until he got a Brooks. His girlfriend rides tandem with him and she gets friction sores from the bike's motion. That's an endurance/efficiency thing though. I sure see a lot of young pros who slam their upper body down over the downstroke pedal when they try to go hard. Not so much the older pros. The few national-class riders I know are very smooth, no motion at all.

I don't know if it's easier to spin circles on a bike fixed to a trainer than it is on the road or not. I doubt that it makes any difference, except that it might be considerably more difficult to know what one's body is doing on the trainer, since the bike can't move in response. As it is said, if you want to get smooth, ride rollers. Resistance rollers are even better.

I don't stand on my rollers anymore. I used to, but my balance isn't what it was. I just feel safer if I don't. It's hard enough without going our of my way to make it harder.

Watch these guys' knees:

Some of them work the bars back and forth to keep the bike under them.
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Old 01-16-21, 09:26 PM
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I was more thinking of climbing out of the saddle, which is different from sprinting,Here's Pantani climbing:
His knees seem to go WAY out as he dances on the pedals. I'd say that's how I do it, but that's like saying "The elephant dances like the ballerina"
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Old 01-17-21, 06:36 AM
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Originally Posted by Carbonfiberboy View Post
I sure see a lot of young pros who slam their upper body down over the downstroke pedal when they try to go hard. Not so much the older pros. The few national-class riders I know are very smooth, no motion at all.
I used to avoid it and tried to be as smooth as possible but I'm still experimenting what may work best for me and tried it. The action seems to reduce the perceived effort similar to how pedaling out of the saddle does but you're sitted (so you don't raise your HR as high) which seems to be a good thing.

I've been testing the technique on steep climbs and seems to be faster and more sustainable to either out of the saddle (paced) technique and simply pedaling smoothly sitted.
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Old 01-17-21, 10:50 AM
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Originally Posted by cubewheels View Post
I used to avoid it and tried to be as smooth as possible but I'm still experimenting what may work best for me and tried it. The action seems to reduce the perceived effort similar to how pedaling out of the saddle does but you're sitted (so you don't raise your HR as high) which seems to be a good thing.

I've been testing the technique on steep climbs and seems to be faster and more sustainable to either out of the saddle (paced) technique and simply pedaling smoothly sitted.
Typical group ride is shattered by a steep climb:
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Old 01-17-21, 08:46 PM
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Originally Posted by Carbonfiberboy View Post
Typical group ride is shattered by a steep climb:
https://www.youtube.com/watch?v=CIHElF8kODg
That is one reason I spend more time interval training in climbs (less training in the flats). One lap fully sitted, next lap fully out of the saddle and so on and so forth.

I used to be not strong at out of the saddle so I built my own rocker for my trainer and is a huge help.

In relation to the topic, I didn't care if the rocker improved my watts or worse on the trainer (I did worse on the trainer with the rocker). All I cared about is my performance on the real bike on the road and rocker helped, A LOT!

Now that I'm decent at out of the saddle, I've removed the rockers and just work on my in-the-saddle pedaling technique in climbs.
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