Rocker Plate Testing with Saddle Pressure Mapping


  • It’s a long one at 30+ minutes, but I decided to leave it that way to show the process and review as much as possible, for clarity.
  • Here are start times to major sections if you want to find something in particular.
    • Rocker Setup (1:23)
    • Tests 1 & 2 for all rocker settings (2:37)
    • Data Review of tests 1 & 2 (7:53)
    • Tests 3 for all rocker settings (19:36)
    • Data Review of all tests (22:26)
    • Final Data Capture for all tests (29:06)

General Info

  • Using a Saddle Pressure Mapping device to capture pressure from the body on the saddle.

  • This includes a Rigid Setup (equivalent to a trainer on the floor), then adding Rocker Plate motion (at 3 different leveling spring settings).

  • I used the bike and trainer mounted on the rocker plate for all tests. I used wood shims to eliminate motion from the rocker plate for the Rigid setting. This serves as a baseline/control for comparison to the motion that comes from the 3 different rocker plate settings, and whether that motion alters the pressure on the saddle.


  • The common theory is that adding motion will change pressure on the saddle, and lead to more comfort for the rider. The rocker plate is an attempt to get a more natural feel and function to the bike on the trainer, that may be similar to the motion we have when riding outside.

Basic Review

  • The improvement starts right away when you move from Rigid (fixed) trainer to a Stiff leveling spring setting on the Rocker Plate. It is similar for the Medium leveling spring setting.

  • There is notable difference with the Light leveling spring setting. The bike and trainer are very free to move, almost to the point of being “hard” to ride and balance upright. It is possible a bit lighter than the setting I use on my current setup. The center of pressure moves fore and aft a bunch compared to any of the other tests.

Initial conclusions

  • I need to do a deeper dive into the summary data I captured at the end, but initial review seems to indicate that adding a rocker plate does reduce the peak pressure on the saddle.

Here is some initial analysis:

This is great! Thank you for posting. Do you have a DIY blog post or video laying out how you built the rocker plate?

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Section 6 has what you need, @GravelNut

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I saw you mention this in dcrainmaker but have you done this with the eflex rocker?

Also this test brings up a question on how useful the pressure mapping is during a fitting. In that if you do a fitting on a fit bike those bikes don’t rock at all so what looks good on a pressure map on a fit bike isn’t how that pressure map will look in reality outside. Would a bike fitting with a pressure map to find the best saddle be better if the bike was mounted on a rocker. (I’m assuming the range of the sensor doesn’t allow outdoor use)


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Sadly, our pressure mapper stopped working, and my boss is struggling with the replacement working. So I have not been able to get any more pressure testing done.

I am well on board with the fixed vs motion fitting question. Ive discussed it with a few others in the fitting world. I want to do tests with several clients this season, using my E-Flex in the shop. I planned to test with it locked out and fully functional.

I hope to see impact in pressure, but also overall fit results. My thought is to try and close the gap between indoor fitting and outside riding, so there is less missed opportunity inside or changes when they rider gets outside.

But the current mess has prevented fitting in any real scale, so it’s on the back burner for now.

To your question on the mapper fixed vs rigid and effectiveness, I think it’s a funny answer. My testing showed that motion reduced the pressure in nearly all cases. The riding being the worst may actually be a benefit in the fitting perspective.

We try to evaluate position and comfort in a short period, so having fixed “magnification” attribute may be beneficial. It might show issues sooner than outside or inside with motion. For things like saddle swaps and adjustment, it stands a chance to be beneficial from that feature.

It’s all interesting and may well be best with a blend of rigid and motion, applied at particular steps or times. It’s part of what I hope to test once we get into fitting again.

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I don’t doubt that’s its magnifying it, just thinking the amount of magnification may not be the same between different saddles.

I so wish you were in Maryland. Too many fitters out here don’t seem to keep an open mind :slightly_frowning_face:

Doing a fit on a rocker would seem to be hard as you have to ignore the overall movement of the bike. The motion recording tools would have to keep track of the bike position too. I don’t think Retul unless they recently upgraded could do it as their refresh rate is too slow and the bike may move too fast for it to handle it.

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  • That’s very true, and one of the reasons that saddle selection and fitting may be the toughest challenge in fitting.
  • I’ve spent many many hours and so many saddle swaps for some riders and still not hit on the right one.
  • The mapper is handy as a communication tool to side step some of the tricky discussion and hit the important points. It can also help rule out some bad candidates. But like other tech, it’s best in helping validate the feedback from the rider, that some can’t always comment on as well as we might hope.
  • Ha, would be fun to work with you. I have my sticking points, but I try to be open to trying stuff rather than being to stuck in predefined settings. Good to have a direction, but there are good times and reasons to stay and try something different too. :slight_smile:
  • I plan to use a mix of fixed and .motion if my ideas have any merit. I know that fixed is still necessary and useful for much of the evaluation process
  • Good or bad, we don’t have the motion capture or analysis setup. The only tech we used was the mapper. Otherwise, I’m old school with visual observation and rider feedback.
  • I’m not opposed to the tech overall, but the relative frequency I see in tech issues on the support site bother me. I don’t want tech to get in the way of the process. We had just enough issues with mapper when it was working, that it caused frustration and delays. I’m not taking that risk with the cost and complexity of the Retul until it gets to a better level.
  • I also worry that tech gets in the way of firing at times by becoming the focus rather than a tool. Fixating on numbers or the process might lead to poor results.
  • But even if we had it, I suspect I would stuff use it for fixed parts of the fitting.
  • My main thought in the motion is towards the later parts of the fit, with hope’s of getting some more lifelike evaluation of the changes in anticipation of the feel outside.
  • Could be a total bust and still not close enough to justify the effort. But that’s what I hope to learn.

I really appreciate your thoughts and discussion. I don’t get to dive in like this as often as I’d like. :smiley:

I’m sure you’ve seen some of my post here and on DCrainmaker so kind of obvious I like tech for the sake of tech in that it makes things more fun for me. But I also know its not really needed. Plus can get in the way of a useful measurement if not good enough.

For example retul’s update speed (18fps) meant I had to slow my cadence down from what felt normal for me. Or the Kinect based fit systems. Sure, its great for gaming but I’ve been to developer meetings (I do c#) on the kinect api and while neat and good enough for games it was obvious that it wasn’t really able to position the location of joints with cm accuracy (low resolution depth camera) and only 30fps so unsure how a bike fit would work.

Seems like STT system’s Cycling 3DMA motion capture ( would be the better option as it does 100fps. So may be fast enough to factor out the moving bike.

Leomo is a non video based motion capture that is interesting. Was almost tempted to buy the type s

Though what looks good on paper may not really work well in reality.

Just thinking maybe I should compare the data from my pioneer power meter now to what it records once I get my eflex rocker. If the vectors of power are different then it would seem like the training impact would be different with rockers

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I love the tech too, especially when it works :stuck_out_tongue:

I’ll be really interested in your comments on feel and power from the E-Flex. I have my thoughts and experiences and have discussed it with many people in the Rocker group.

I’ll hold that for now (assuming you’ve not already read it) and we chan chat more when you’ve got some experience too. :smiley:

I have only read the big eflex thread here (the one with your review and modifications) and dcrainmaker’s review. Don’t know any rocker group so kind of want to read it but after I try it. Thinking having less biases going into trying it the first time will give a better first impression in that I’ll be more open to thinking about how it feels. (On the easy week at the end of ssb mid 1 right now)

Just thinking, pedal strokes are generally the same one to the next so frame rate isn’t so important but motion blur inside a frame is. If there isn’t much blur you can merge the data from many pedal strokes to show what happens during one pedal stroke.

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Here is a link to the FB group when you want to check in there.

Yeah, I think the pedaling could settle down and be predictable enough for less than perfect tools in many cases.