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Need to get creative like this. Then make that sensor travel your shock ratio.
The one time I set up Motion Instruments v1 (RIP) on a Santa Cruz, what I arrived at was mounting one end of the tracer to the upper link, and the other end to the bottom of the top tube.
This is what I was thinking of doing. How did you attach to the upper link? Similar to what Carlino posted?
Thank you for the pictures. I was thinking of how to do this by mounting to the down tube and to the link. I sat there for a bit and didn't get creative enough. Are those mounts bent sheet metal or 3D printed? The tape doesn't interfere with the link rotation? If I can get this figured out I'll have a happy customer.
I had a 90 bent ball joint stuck to the front side of the upper link. And a standard ball joint stuck to the underside of the top tube. I took the shock out while mounting and made sure that in the full range of motion, the tracer wasn't getting bent or reaching the limits of the ball joints' swivel. I can't find any pictures, sorry.
This was 3 years ago so my setup was a little more sketchy. This was the first 3d print piece I made. Looks like I went to top tube. Which ever way you mount, the more travel you can give the sensor the less sensitive it will be and could be more accurate
How do you „decently“ measure sensor vs wheel travel (leverage curves) with setups like these?
For MI, they had a library of leverage curves, and if yours wasn't in it, you could create your own through a fairly tedious process of measuring wheel displacement vs shock displacement. If you didn't do that, it would just use a linear approximation (i.e. 30% of shock displacement = 30% of wheel displacement). Can't speak to any of the other systems out there.
I'm aware of that and am usually doing that in Linkagedesign to get proper rear wheel readings for my BYB kit. But if you use sort of "random" points between your rear and front triangle (as pictured above on that crestline), you get (at least in my mind) superfunky sensor displacement that has nothing to do with the shock movement. But I guess you could take the same approach in linkagedsign and use a high-res picture in order to get ~10 points of real wheel travel and corresponding sensor length and interpolate.
Yup you can use linkage in the same way and just pretend the sensor is the "shock" and calculate the wheel position relative to shock position from there. You can manually calculate a shock position reading later on if you need that but you will probably only have measurements for one or the other in the "raw" data.
I think BYB has added live sensor readings as well in the new kit, so you can mount the fork sensor to your rear axle and take the measurements that way.
If you have a sensor not mounted in parallel to the shock, this is what I do.
Let’s say you wanted to do an average leverage curve on a DH bike that is 200mm travel and 75mm shock.; first mount the sensor to a location that fits, then you compress the shock to bottom out and mark the sensor max travel. Return the shock to full travel. Measure the travel the sensor. This now becomes you “shock stroke”, so you would have 200mm X 72.5mm.
Or you can make your own leverage curve my measuring the sensor travel every 5 or 10mm of rear wheel travel. This is more accurate if you do it right.
Just measuring the travel on the sensor is part of the story. You also need the leverage ratio as that affects how wheel travel applies to sensor travel. Or shock travel.
The more progressive the leverage ratio is, the bigger the non-linearity between the two.
Measuring wheel travel is also a big question - how to do it reliably? Clamp the bike horizontally and move the rear wheel upwards and measure vertical travel? Measure travel along the path (even more complicated)? It's not as easy as with a fork and could change everything I mentioned above.
Or is the whole situation not that sensitive?
When I did it, I flipped the bike upside down, took the wheel out but replaced the rear axle. I tried to set it up so that the tires were level before I removed the wheel (extended seatpost IIRC). I then hooked a ratchet strap to the rear axle to hold it up, at the starting shock stroke position, then removed the shock. Key is figuring out what your zero stroke is, most frames can extend a bit past that. Then I measured vertically axle to floor in 5mm increments, taking corresponding measurements from the sensor stroke. When I plotted the data in Excel, it was close to what I expected (more or less linear progressive - for Santa Cruz Nomad), but had a bit of noise, so I Excel calculate the formula for the best fit line. I then created a new data table using my starting data point and my line's formula, and then fed that data into MI. It was definitely fiddly, and took probably a couple hours all said and done. It'd probably be easier with 2 people.
All great info above! the more you do it the more accurate and faster you get.
I wonder if you could use the slacker tool to help figure wheel travel.
I've done it a very similar way in the past - I think this was an aluminium bar or timber board attached to the frame parallel to the "ground". I recorded the points then plugged it in to excel and used the fitted trendline to create the leverage curve. Although this was using the Aim system where you could make a custom math channel using that equation directly in the software
I've been making progress on a set of tools to help with set up, DAQ and frame measurement -
*testing magentic encoders as rotary sensors, and also a tool for meauring wheel paths and leverage ratio. It would be cool if the BYB system could have DIY digital sensors added - even if it was standard format/firmware we could use to build custom sensors with a common part like the AS5600 and the logger would be able to read it
*measurement aids like a "dummy" shock of accurate length so you can precisely set the exact fully extended position - I guess you could also 3D print several of these in 5-10mm increments and swap them out, measuring the axle position in every setting. Would be a little tedious but more accurate than trying to measure the change in distance for shock & wheel with a tape measure
*some more software tools to help generating leverage files in the correct format - I had one for MIQ and it does help a lot being able to generate that data quickly!
Haha, love the plastic rods label!
in rod we trust!
I got my unit did a day of testing to just get the little tweeks worked out. Then another day of actually testing on a rougher trail. Overall after following some of the suggestion from the auto tune to see if it would feel better it did but I am surprised by the suggestions. I have always ran a fairly compression heavy setup and it has constantly told me to go more open on both compression and rebound. I swear the auto tune feature will tell me different results on the same run and will be slightly different between phone and computer. I know the auto tune isnt the best way to use this software but just trying to use it a bit to see where it would take me. I dont under stand when I toggle between the skill levels as I go down in skill level its telling me to add more compression damping. I thought that would make a stiffer bike overall and an advanced rider would need more support overall. Any ideas on this?
What compression and rebound speeds are your guys trying to achieve? I posted my last recorded run. I have a Levo 4 with a 170 fox 38 Grip 2 and a CC link and DHX. Both are fully open compression and rebound. When I got back to my truck the data said I was 27% avg between front and rear. The auto tune suggested I bump up bottom out. I had no spacers and I was going to try and lowering my average sag so added another 3 psi in my fork and went for another lap. I also slowed my HSR on my fork 3 clicks.
Unfortunately when I dropped in I went to pedal and it felt like my bike was off, then I flipped up a large rock causing me to almost crash so I stopped to remove the rock and mess with my bike. I kept getting the same fault. I decided to push back up anyways and start the run over and reset. Again I dropped in and hit the same corner where the rock pulled out and started to hear some crazy noise. I stopped and realized that when I almost crashed the bars twisted and the fork sensor hit the downtube and breaking the ball joint socket. Knowing this now I would have set it up much more forward from where I did. Does anyone know if I can buy something like this in the US? Also the rear sensor ball joint vibrated off at some point not sure when.
My take, rear is hitting higher max compression if I could use a HSC adjuster I could slow it down. The fork is hitting slightly higher rebound speeds so use the HSR to slow it down. Overall pretty matched speeds. But I would think I would want to add LSC to the rear to get it closer to the fork but its telling me to reduce.
TLDR
What rebound and compression rates do you shoot for?
Why does Auto tune tell you the more advanced rider you're the less compression damping you need?
Where can I buy these ball joint in the us?
Check my data.
Awesome, that you are getting out there and using data! Bummer the sensor broke. The first day I used my Motion instruments. I broke it as well. But since then I’ve learned a lot more and figured out how to make them more durable.
look at McMaster car. You might be able to find something you can rig in there if the remaining part of the mount will unscrew from the sensor
https://www.mcmaster.com/
Hello @thegromit ,
Nice that you started using the system! Ouch for the broken part, but don't worry... our uniballs are removable, so not a big issue! With other sensors, you'd be throwing this it in the trash can (or using alternative/creative mounting options), but with our design, you'll just need to unscrew the remaining part of the broken uniball and replace it with a brand new uniball!
Feel free to send me an email at: enrico@bybtech.it so we can arrange the replacement.
Best,
Enrico
Hey, here are a few notes from your data. Take this just with a grain of salt because I don't know the bike, the track, the steepness, the dirt type, riding level.
-You can consider doing a shorter section of the trail, like 90-120 seconds. Just for your initial tune.
- I like your Dynamic sag balance and max travel. I wouldn't worry about adding or removing spacers yet. You only had 1 "Bottom out"
- For Comp speeds, you need to ask yourself if you like the front or rear feel more. Either stiffen the rear or soften the front.
- Same with reb speeds, which feels better, then go with that? If you can't feel which you like, I normally go faster or meet them in the middle.
-The rear is moving much more than the front at 80m total stroke vs front at 73m total. Once that gets closer, it will really improve the ride.
- You are getting close, but still off a bit from a great balance!
Thanks for the response. A few questions here.
For Comp speeds, you need to ask yourself if you like the front or rear feel more. Either stiffen the rear or soften the front.
---- I am full open now with both compression adjusters, so my only option currently is to go stiffer in the rear. This is going to bring my rear averages down then to be more inline with fork, correct?
Same with reb speeds, which feels better, then go with that? If you can't feel which you like, I normally go faster or meet them in the middle.
----I am again at full open for front and rear LSR so I cant do much there. I was thinking about slowing the HSR on the fork to bring down the max compression speed. Is this a correct interpenetration?
The rear is moving much more than the front at 80m total stroke vs front at 73m total. Once that gets closer, it will really improve the ride.
----I am guessing this is a blend of both the reb/comp speeds? I don't want to decrease my fork spring rate any more and I dont really want to increase my rear. Can you explain how this computed? I actually wasn't looking at the parameter before.
Replacement rod ends are very common - you can get them from mechatronics or other "maker" supply stores and Ali Express very cheaply, I try and buy a bunch of different types as spares or for tweaking length
Can you post a picture of the position histogram? That shows better if you are using too much travel too frequently
re: the speeds questions, the front and rear are unlikely to match most of the time, due to the weight distribution and how both ends impact bumps. Typically the front will have higher rebound speeds and lower compression speeds than the rear, so if they are the same its probably an indicator that the spring is too soft or stiff at one end. I didn't see your weight or spring rate used anywhere, but if you are running the rebound wide open its more likely that your spring is too soft or there is excess friction. Grip2 had very fast rebound but the DHX depends on the tune, so it is possible your tune is too slow there, have you got the specs for the shock on hand?
What fork, shock and bike are you on?
Fox 38 grip x2 170mm 103psi I think 3 volume spacers. Levo 4 LS cascade link with a DHX coil 434# ohlins spring
About 174+/- lbs no gear
Ok sweet, I see a few things now -
The fork is spending more time deeper in the travel than the shock, so I would increase the pressure to about 110psi. If theres already 3 spacers then that should be OK I wouldn't go more. Normally I would suggest 2 for you and you might want to try that so you can experiment with higher pressure first. But normally I would be aiming for closer to 20% average position on the fork, no more than 25 for sure. I do find starting with too many spacers can send you off in the wrong direction so keep that in mind.
Then slow the rebound down - set HS to their factory suggestion and bracket the low speed +/- about 2 or 3 clicks from suggested as well. ignore the autotune for now and see if you can feel the difference and observe how much the damper speeds and fork position changes. I have found you can make large changes which you can feel on the trail but there is little change to the numbers, so I recommend making big adjustments until you can personally see changes in the data the match up to the difference you felt on the trail
I was thinking I needed to go up in spring rate on the fork and I made a mistake on my previous post. I was at 100psi and bumped up to 103 for my next run before I broke the sensor. I will do a few more runs incrementally increasing fork pressure until I get closer to the 20% mark before I dive too far into the compression/rebound settings.
What I dont get is why the position distribution on the desk top version shows such different data. The X and Y axis are at a different scale and the data show it never gets past 90mm of wheel travel. What am I doing wrong here?
Dumb question but if I don't have the leverage programed in can I not use the wheel travel function?
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