Suspension Data Acquisition

About to start processing some brake & suspension data collected by Matt from BrakeAce recently - he did a test a few months ago comparing how much braking performance changed after bracketing damper settings (it was a lot!) 

Also got my hands on a couple of used BYB units which is having its first outing at the moment! Some neat features with that system, like the ability to run up to 10 analog sensors at 1000Hz  in a self contained package which was pretty appealing. I've needed that for a bunch of experiments I want to do so hopefully they will get some action this summer!

Will have a 3d printer in the new workshop in a couple of months too, aiming to have a fast/easy workflow for making sensor mounts on different bikes which has been a massive bottleneck for me and I'm sure lots of other people

Is 1000 Hz enough? I guess it should be fine for brake sensors (position and/or pressure), but suspension travel? I was advocating having at least 2 to 4 kHz sampling rate for structural (strain gauge) measurements. 

Looks pretty reasonable to me, DH race bikes need to be fairly stiff which inherently reduces damper speeds. Most of those values are pretty typical to me, if anything the average position looks a little soft but if thats from Andorra (which is steep) then it tracks. Total travel used is pretty ideal too.

Not the 10m/s rebound speed at the rear wheel though! I have noticed a few spikes with the BYB system from other people posted data and even a few basic tests in the shop so its one thing I'll be looking in to with the new (to me) gear. Its probably a minor sensor dropout, ie loses connection for a sample but the logger interprets that as the wheel going from something like 100mm to 0mm and back again in the space of a few 1000ths of a second. Easily fixed with some basic filtering in by the software but its something people need to be mindful of. And why I always take peak speeds with a grain of salt! A single random spike should be ignored but if its consistently reaching high speeds then either extremely soft of there is a problem with the mounting fixtures (very common and why I get super fussy about how things are mounted)

If you export raw motion IQ data you will sometimes see a handful of dropouts, which is almost unavoidable for wireless transmission. Their app seems to be pretty good at either dropping those samples or filling it in without doing any excessive filtering or smoothing. When I process it I mostly just drop those samples and the values come really close to aligning exactly with the app. I could do something a bit more fancy to interpolate them but usually if the sensor mounting is solid the dropouts are too few to impact the resulting data much.

@Primoz - yeah 1000Hz is plenty, the shannon-nyquist theorem suggests that sample rates for frequency domain needs to be 10x the frequency of the inputs to be recorded. Since the majority of suspension movement is under 20Hz, then 200Hz is the minimum to be "acceptable" and 1000Hz is about the highest practical rate for logging, since higher than that introduces excessive noise and creates monster recording files. You also need sensors that can respond fast enough or have the resolution to see that much detail which isn't practical most of the time. I would like to be able to log vibration and force at very high rates but there aren't many off-the-shelf loggers that can do that which aren't crazy expensive or impractical for mountain bikes.

I think it shouldn't be too hard to get them as long as the data rates aren't an issue. Syn bike system supports I2c communication for example and I know Texas Instruments has a barrage of adc converters to fit your needs, from below 1 kHz all the way to MHz range with up to multiples of 10 bits of resolution.

Vibration is something I would have to look into how to get it to work given you need a charge amplifier to make an accelerometer work. Force (strain gauges) is easy though given what I have seen. 

Massive bummer for those of us with a MI2 on order:

From Motion Insturments 

Hello,

Just got this email from Motion Intruments (I placed an order a couple of weeks ago but have not received my order, now seems like I never will):

Oh man thats terrible news - I had heard there was outside investment in the company so this was exactly the kind of thing I was worried would heppen. It seems to be inevitable these days, but thats a super shitty move by the controlling company to take money for the product before pulling the plug. 

My plan is to wait it out to we hear from them on what they are planning on doing. Best case is that someone else swoops in and buys the IP and product and plans to make it commercial. I got the sense from the email that they are looking at options to bring MI2 to market in some capacity, and I certainly hope they do. 

It wouldn't surprise me if the technology will still come to market in a different form and with a different brand. I don't really want to speculate more but its strange to develop it this far and then just pull the pin completely. Not that its never happened, but this isn't the end of the story IMO

Got an email last night saying they were going to refund everyone who ordered this week and that there were a "lot of orders". Really hope they can find a way to ship the product, from everything I've seen they are ready to go so I'm really puzzled as to why the new owners pulled the plug...

Just got this email. Just seems to odd all this, spend so much time on everything then throw it all away and pretend nothing happened. What really happened here I wonder?

---
Hi Folks,

Prior to the it's all gone to hell emails, they were CLAIMING that the only hurdle left was some sort of emf or similar test to make sure the unit was safe.  IF that was actually the case, I wonder if that test found issues and that was the final straw?  Seems unlikely to me.

Important to emphasize that this is pure speculation on my part.

Before I placed my pre-order they told me that they'd had issues qualifying the fork sensor but had resolved that and the hardware was on a boat en-route to the US w/ orders expected to ship in late Sept.

Interesting.  Rob seemed like a great guy via email, so I guess I believe everything.  Absolutely nuts if they have product but are not going to ship.  Hopefully a sale of the IP and existing systems is imminent.  

Rumors/speculation from PB comments are that Specialized is the controlling party, I'll reserve judgment as e don't have all the facts...

Rob is also answering comments there, which is above-and-beyond IMO and just increases my appreciation for how he/they are handling what must be a really crappy situation for them.

definitely not BYB due to price, and a quick look at the syn.bike/hardware webpage shows some text and a picture but not much else... have they announced any plans to release a kit or something?

$500 was such a great price point for something seemingly so capable. super bummed about this and hope to see a similar product soon. I was pretty damn close to pulling the trigger on System 2 back in May.

Saw all of that and agree.  I had such a limited string of email exchanges with Rob I was reluctant to draw a real conclusion, but all the comments to that article make me pretty darn sure Rob and co are standup people that were shooting us straight. 

Every time suspension/brake/drivetrain data acquisition comes up in mtb media there's a discussion of the hardware. Engineers, I'm sure you're valuable and wonderful people. But just for a minute accept the premise that these systems are 100% accurate.

The first question raised by anyone looking at these data should be "So what?"

How, and under what circumstances, do these data help you accomplish something? Look at that Syn screenshot from a few posts back. These data are dumb. There's nothing remotely prescriptive in this. And that goes for the screenshot that's supposed to be Seagrave's DA output, too. There're no performance metrics, there's no context (here we can make some assumptions that Seagrave's team actually does have this stuff in a system alongside the DA--rider notes, spotter notes, a profile of the track, timing, etc). Our premise was that the hardware is accurate, and so we accept that in the descriptive sense that these data are true, but these data are just the measures the hardware folks decided they could implement within the constraints on the product -- that's no guarantee that each or any of these will be useful, or that some other potentially more useful measurement wasn't left out.

Which should give everyone pause when this cottage industry of people trying to tune your ride according to these data pop up making a meal out of whatever is to hand. Dynamic sag? Every so-called average of a set of measurements is stupid if you're not careful about what gets included and not included in the set, and if you're not carefully looking at the distribution of the data. Balanced suspension is better? What exactly do you mean by balanced: max wheel speeds fore-aft in a given hit, mean wheel speeds fore-aft in a given hit, max shaft speeds fore-aft, mean shaft speeds fore-aft? What's your rationale for the choice? How close do to measures have to be to be considered balanced vs imbalanced? And what's the evidence balanced as you define it is better in the first place? Which performance metrics are you watching? Cause those aren't on this screen and likely aren't even captured by this system of hardware. So ask of the data, 'so what?'

It shouldn't just be scientists who are disappointed by pseudoscience. Put your engineering hat back on. Imagine turning in a report with your name on it making serious predictions about future performance using data like these. Imagine really building something that was really expected to perform and your reputation was at stake because people are actually going to check your work. You wouldn't trust this stuff. You wouldn't drive your family car over the bridge that mountain bike DA built. Believing in this stuff now isn't like generously incubating a technology that will later deliver even more; being unable to tell fake from real may slow the development of stuff that actually works, since you remove pressure to achieve real gains.

@Snfoilhat - I don't really understand what you're trying to say.  First, I think it is accepted that there is a degree of error in most of these systems.  Mounts flex.  Electronics do their thing.  There's going to be a degree of error.

On your other point.  Are you wanting these systems to tell you how to tune your bike?  I don't think that is what they are trying to do at all.  Read through the Motion Instruments manual and there is a lot of advice on what the data means, and what you might do to tune your bike with it.  But none of them are trying to be a black tuning box.  It's about knowing how you want your bike to behave and comparing different settings to see if you can get there.  There's no one answer to how your bike should be tuned or what those numbers should look like.