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Discussion Starter · #1 · (Edited)
The 2016 shock came in, so some baselining work can be done.

Pic 1. The shock is heavy, about 6.5 lbs. I can see it mounts the wrong way as the shock body mounts to the swingarm and the shaft end mounts upward to the frame. This mounting puts the weight on the swing arm and adds to the unsprung weight of the rear suspension! This is a no-no if you want to get the best handling out of a bike. I can also see the plastic cover masks the shock shaft, so no slipping a nylon washer to track suspension use unless it is removed.



Pic 2. The shock is disassembled using a 20 ton press and some hardware to isolate the spring during compression. Spring work is much safer this way.



Pic 3. The components. There is good news and not so good (but no surprise). Good news is the shock working range before getting into the rubber stopper is 1.25”; this is a good working range. The spring is straight – without tapered ends, so you can get easy replacements. Not so good is the nonstandard length of 6.5” as springs come in 6 or 7” length as closest length match. Not so good is the shock itself, no nitrogen pressurization; its about a basic shock as you can get. The 7 seven preload indents span 7mm, so that is the most you can dial in. The spring itself mounts in the shock with a 1/8” compression, so the spring is 6 3/8” when installed at the 1st preload indent.



Pic 4. I used to use my gym equipment to load up a spring to test them, but I didn’t have enough weight to compress the big springs, so new equipment is at hand (on right). Here is the spring compressed about 1.25”



Pic 5. Test results, you could say the spring is a straight rate spring but it isn’t the best curve fit. Even so, a close approximation is 862 lbs/in.



Pic 6. This is the best curve fit. It shows the spring capacity at 1.25” of compression.



Pic 7. This shows the tested curve, now mounted in the shock with 1/8” of compression. The net affect is moving the curve down 1/8”. It has a new upper capacity with the 1/8” preload added.


Pic 8. Now we can start to see what it does in setting up the bike (sag). If I commit 25% of 1.25” (0.31”), the 1st indent preload setting can handle up to 361 lbs. That’s the max sprung load of the rear of the bike + rider. If the bike + rider sag load is greater, you have to go up a preload setting. Its easy to check this with the nylon washer. On the upper end, I found a good rule of thumb is having a ratio of about 2.75 or 3.0 to 1. So if the max sag load was 361 lbs, then the upper end might see 3 x 361 or 1,083 lbs. This is below the upper capacity, so in theory you would not bottom out.



Pic 9. What if the 1st indent could set a good sag distance? You must dial in more preload. Here is a few more curves to show the 4th and 7th (max) indent setting. You can see it keeps increasing the upper end capacity, but not at the same rate. On the 7th indent setting, it looks like it handle up to 600 lb. sag load, but this only translates up to a max of 1,500 lbs, or about a ratio of 2.5. So at some point you will need a stiffer spring.



This is about the most I can do without a bike. If there is a rider in the Baltimore area that would be willing to swap shocks (I can do the shock swap) and test ride this shock for a week or so with the nylon washer, we can get the necessary data to mathematically lay out the family of spring rates of a given rider weight if you stay with the stock shock. The data is also go to use with aftermarket shocks too, so it isn’t wasted effort.

Pm me if you want to be the rider to help finish the thread.
 

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Tiger, awesome test, analysis & write up. Very thorough and detailed. Suspension is amazing to me. Recently I got the Racetech suspension book and it blew my mind. I'm sure @pattonme and @jbluetooth will chime in here and be interested in this. Pattonme is a fork and suspension guru and Jesse, jblue, is a racer and motorcycle retailer and part designer/OEM part builder. Jesse sells a shock for the R3 that was modified off the base R6 rear shock and designed and built in conjunction with Traxxion Dynamics I believe.

Again, awesome stuff. Interested in reading more!


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Yeah I can't compete with annotated pics like this. Very nice presentation.
 

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Wow. I am seriously impressed. Never before has anyone done such an incredible, thorough and detailed write up about the stock rear shock and spring.

In fact, I got lost in the math about half way through the write up.

So, help me understand this in layman's terms - rear shock is basic. I get that part. Stock spring is non standard length, I get that too.

As for all the preload and sag etc, I'm lost. And how is slipping in a nylon washer going to help you track suspension usage?

Sorry if these are all silly questions but I really want to understand it. I'd also like to know what would happen if you swap out the spring or what shock might fit in there that also wouldn't cost an arm and leg? ie - get a lower more progressive rate spring and a more advanced shock while still lowering the bike a bit (say 0.5")
 

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Discussion Starter · #5 · (Edited)
How does the nylon washer help; hopefully this helps answer the question you have. Let me know if it doesn’t.

By calibrating the spring and determining the equation of the [blue] line depicting the spring configuration you are using, you are measuring the distance the nylon washer moves. That distance is “Y” for the equation. Once you know “Y”, you can mathematically solve for “X” which is the load. So, in pics:

Pic 1. A pic of another shock that I did the same thing for. I cut an observation hole and mounted the washer (I call it a disc sometimes) on the shaft. You can see the washer way up at the top. Every time you take the measurement, you reach in with your fingers and push the washer back up against the shock to reset it.



Pic 2. Measuring the washer moving. There are many ways to measure the movement of the washer. For this bike, access was limited so I drilled a small hole so I could insert a wooden stick to mark how far to the washer. Knowing the total distance to the top, I just subtracted the stick measurement minus hole thickness from the total distance and you get the distance moved. That distance = “Y”



Pic 3. This shows what taking sag measurements would be like. You see the stick with 3 marks. A = the distance with washer all the way up. B = bike sag measurement (bike weight only). You can see the bike does compress the shock a bit. C = rider sag, the washer is pushed further, so the measurement is the shortest.



Pic 4. So taking the measurements, and putting them on the graph for that bike spring gives me a way to see/solve for the bike sag load and rider sag load. So on this graph, I measured a bike sag distance of 0.23”. That is the “Y” value. Using the equation of the red line shown on the plot; plugging in the value for Y, I solve for “X”. In this case, X = 620 lbs. This value will remain the same no matter what spring preload indent you use. I always use the softest setting so I get the maximum bike and sag movement. Same thing for rider sag; I measured a distance of 0.45”. That Y plugged in to the equation yields a rider sag of 830 lbs.



Pic 5. Now we go riding. In this pic, I show 4 measured data points (0.625, 0.741, 0.751, and 0.844). They are taken the same way you did the sag measurements with the stick. The only difference is I put the shock on the 7th indent so I had greater load capacity at the top end. Working the math and solving for “X”, I can see the range of loads I am seeing on different rides. You should not expect to see the same value as each ride is different. On the highway at high speeds when you transition through long dips, your shock piston speed will be the slowest, so the spring carries the load. When you are riding dynamically quicker through dips and turns, the shock piston speed increases and the damping force helps you; the washer movement will be less. So, for these 4 “Y” values, the corresponding shock loads are from a low of 1,425 lbs to a high of 1,718 lbs. It doesn’t take too long to find your min and max; perhaps a weeks’ worth of riding.



Now you do this testing with the oem shock. All measurements are applicable to what you will experience with any [aftermarket] shock. You take the oem data loads + the working range of the new shock and determine the spring rate for the new shock you need. Damping is a part of the equation as you can set up the damping to take some of the load. It depends on your riding style, road conditions, etc, but this method will help you trade off some spring rate for damping help, etc.

Once you get the new shock in, you should keep your washer on the new shock and set sag and track what your experiencing on the top end. Our buts are not always accurate, so the washer can tell you if you are bottoming out.

If you want to go more advanced with this, you can also use the washer to track suspension use to make sure you stay within a range. By measuring the relationship of swing arm position to shock compression, you can set up the suspension to stay with a range that favors more of a rear up orientation to keep rake angles the most favorable to best handling… but first things first, get a washer on and start collecting some data. Still looking for the test rider in/near the Baltimore area. Once I get some data. I am gong to experiment a little with a possible alternative. But I can't get to far as I have 2 bike projects I have to finish at the moment.

As for lowering the bike, you will not do it via the springs. You have to make other changes to lower the bike. Can you say why you want to do this? There might be ways to do this without changing the suspension. If you have to do this, you should start a thread and have all comers dive in. Depending on your front setup, it could be straight forward. The rear would involve using a shorter shock.

If this isn't clear, say so, and I'll try to clarify the new thing that isn't clear. Note, I updated one of the earlier pics, so the equation of the R3 1st indent is now on the graph.
 

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Yeah Bluebird, don't get lost in the math. It isn't that important. Tiger explained his two variables, x and y, which are conventional and what they mean. If you remember algebra and precalc, and calc of course, a function explains the relationship between two variables; for each input x there is a single output, y or f(x), otherwise it is not a function. He gathered his data and drew a scatter plot. From this he was able to determine the line of best fit between the points. A linear equation has the form of y = mx + b where m is the slope. His R squared is how best the regression line fits the data. The math helps but the real crux of it is the visual graph. His variables are load, x, and distance, y. So from the graph you can visually see the relationship. For each corresponding x, you get each y. tiger is showing things change and about how one item changes in response to a change in another item. It is the rate of change. Just like in economics which is what my freaking BA was in. Econometrics was lovely. *cough*. Anyway, it is just like a demand curve. The graph explains how demand changes as the cost of a unit goes up. Instead of cost and demand, Tiger is explaining the relationship in the behavior of the shocks variables load and distance. Meh, I suck at teaching and explaining. I don't know if Im helping.
 

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Well, I almost failed Economics soo...;)

Okay, I get it now, thanks for all the explanations guys.

I really am okay with how the bike rides and I'm confident on it now that I have proper riding boots. But, I always thought it would be 'nicer' if I could be 100% flat footed at a stop light. I'm just on the ball of my foot technically but it feels okay because my boot has a heel on it so it looks like I'm flat footed.

I've seen all the lowering options out there and quite frankly, none of them are very appealing. My bike's suspension is bone stock - and really I haven't done enough riding to know how one bike feels different than another, much less a different suspension setup. Although I will say that lowering the preload to 2 made a big difference for me (probably cause I'm on the lighter side at about 155 lbs)
 

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Well, I almost failed Economics soo...;)

Okay, I get it now, thanks for all the explanations guys.

I really am okay with how the bike rides and I'm confident on it now that I have proper riding boots. But, I always thought it would be 'nicer' if I could be 100% flat footed at a stop light. I'm just on the ball of my foot technically but it feels okay because my boot has a heel on it so it looks like I'm flat footed.

I've seen all the lowering options out there and quite frankly, none of them are very appealing. My bike's suspension is bone stock - and really I haven't done enough riding to know how one bike feels different than another, much less a different suspension setup. Although I will say that lowering the preload to 2 made a big difference for me (probably cause I'm on the lighter side at about 155 lbs)
I'm short too. My Japanese Mom is 4'11" and 98 pounds wet after a 10 course Italian meal. My Dad was 5'11" and 200 about. I ended up being 5'5" but stocky and muscular. In my weightlifting and PT days I was around 180, but too bulky. Now I'm 165. I wouldn't say 155 is light. I am shocked about how many 6' guys are 150, and 5'10" guys are 140. Weight can be super misleading. I am pretty much flat footed on my R3, but I rarely wear boots. I wear my TCX, Joe Rocket, or Alpinestars Faster "Riding Shoes" which are not thick soled or height changing. Suspension has a huge effect on all aspects of the bikes feel-from preload, to corners, to split second emergency situations-getting it right for you is huge and often overlooked. It is something you definitely want to look into, learn, work on, and get mastery of.
 

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The washer is moved up the shaft from th part of the shock that moves. It's he same as placing a zip tie around your forks. After a ride, he bike is at rest and the location of the washer or zip tie would indicate the further your shock travelled up its shaft. If you are willing to truly learn, there are several sites you can go to that explain suspension, robot ninja has linked them before. Or spend ~$30 on the suspension bible. People get so caught up with mods but neglect publications that also help a rider be a better rider.
 

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Good data. I didn't get that oem rate testing the spring; closer to an average of 862 lb/in which is 7% low compared to the indicated oem rate above). My spring test gear is good within 2% accuracy (factory spec), so a bit surprising there is this big a difference. In the end, you can test to get you close but you always have to ride to verify you are not topping out.

The YSS spring rate (854 lb/in) would be okay for a light weight rider (Yamaha design weight target) if oem was 862 lb/in rate spring as you could add a slightly greater initial preload of 0.125" to the YSS shock. Without riding data to verify top end spring usage, I think you should be getting a higher rated spring if you are greater than 165-175 lbs.
(note: This would also require the YSS shock to have a 1.25" working range before getting to the rubber bumper like the oem shock)
Out of curiosity from you suspension guys, when you mention rider weights, you mean geared up or not? As with race tech, sonic springs, or ohlins, everyone seems to differ with what thy call rider weight. I was about to order an ohlins but read that replacement springs are limited, and that the spring (for race use), would be very light for anyone over 140 lbs. I don't race but definitely do track, so not quite sure if I want an ohlins or other brand at this point. I copied this from another thread cause I didn't want to derail the YSS thread.
 

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Discussion Starter · #11 ·
For me, I would use the rider weight to mean the total weight weight of rider + gear. I do this as I would want to correlate how the suspension is working for the weight of the rider (with all gear) + weight of the bike.

What geometry have you set up the bike to run on the track and/or street? Have you checked the swingarm movement to shock compression? Are you running the shock slightly longer than oem length?

One of the nice things about this bike, the aftermarket is very good. I have not seen other bikes with an Ohlin option in the less than $600 category of a YSS option for less than $400. I too have a Japanese mom so I am a bit on the light side (170 with no gear) but heavy enough to want to make sure I don't bottom out,

Jerry
 

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For me, I would use the rider weight to mean the total weight weight of rider + gear. I do this as I would want to correlate how the suspension is working for the weight of the rider (with all gear) + weight of the bike.

What geometry have you set up the bike to run on the track and/or street? Have you checked the swingarm movement to shock compression? Are you running the shock slightly longer than oem length?

One of the nice things about this bike, the aftermarket is very good. I have not seen other bikes with an Ohlin option in the less than $600 category of a YSS option for less than $400. I too have a Japanese mom so I am a bit on the light side (170 with no gear) but heavy enough to want to make sure I don't bottom out,

Jerry


Japanese Mom's are crazy! :). Nah, love my Mom. Mom is Japanese and Dad was born in Wyoming but of mainly English heritage. I'm Hafu. My bro got an anglo name and I got the Japanese first name Kenji, for second sons.

And yes, the aftermarket is great for this bike which lead me to choose it over the Ninja300 besides leaning more towards Honda's and Yamaha's historically over other manufacturers. Even after a year, the aftermarket was substantial. Though I have been riding for years it was not until recently did I start paying more attention to the suspension and geometry. It is a huge, complex and diverse topic. Recently I got the suspension bible to learn more and the depth of it was mind blowing. Though I outfitted aesthetic and other performance related parts before I did suspension, it does not mean I do not consider the suspension to be integral to the ride and control of the bike. As it is, suspension parts are usually the most expensive and intensive upgrades. So far I have a rear shock and preload caps. In the future I am looking to upgrade the front springs with Sonic's or the Ohlins or Andreani fork cartridge kit and definitely want the Ohlins steering damper and Graves mounting kit. The steering is so light and New York is laden with warped and bumpy asphalt and pot holes. A couple of times I had the steering shimmy dance which I want to mitigate with a steering damper. The amount of suspension knowledge here is unreal though I think it matter more on the track as far as performance but street riders shouldn't overlook it due to the street being what it is-a circus.


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Discussion Starter · #13 ·
Don't overlook Penske springs:
http://shop.penskeshocks.com/FORK-SPRINGS/

They are shorter than RT spring so they allow you to set up your suspension up front a bit different since they are shorter (reduce air spring and go with more steel spring) for a more linear rate overall spring. Also note, if you are going with one of the new kits on the market, the springs for the kit are a bit different than ones you buy for the damper rod/GVE set up as they are a bit smaller in diameter. If you know you are going with a cartridge kit eventually, then skip the change the spring now step as the spring may not be usable later saving $120 or so you would have spent on the spring.
 

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A couple of times I had the steering shimmy dance which I want to mitigate with a steering damper.
What do you mean exactly? I always wondered what the point of a damper was for a bike. As for suspension, it is something that I really have a hard time fully (or even partially) understanding.

Being fully Asian (Chinese descent), I'm definitely on the light side at 155 lbs (about 160 with gear I'm guessing), I'm starting to notice a few things. One, the nose definitely squats a lot, even in fairly light braking. Two, the bike feels a bit 'hard' or something going over bumps or railroad tracks. I've learned to relax but it still feels like the bumps are not that damped. I equate this to driving my old car as the springs are pretty hard on it but the shocks are a touch softer than I'd like. In other words, the springs don't have much of a progressive rate on them. I think the R3 is similar.
 

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What do you mean exactly? I always wondered what the point of a damper was for a bike. As for suspension, it is something that I really have a hard time fully (or even partially) understanding.

Being fully Asian (Chinese descent), I'm definitely on the light side at 155 lbs (about 160 with gear I'm guessing), I'm starting to notice a few things. One, the nose definitely squats a lot, even in fairly light braking. Two, the bike feels a bit 'hard' or something going over bumps or railroad tracks. I've learned to relax but it still feels like the bumps are not that damped. I equate this to driving my old car as the springs are pretty hard on it but the shocks are a touch softer than I'd like. In other words, the springs don't have much of a progressive rate on them. I think the R3 is similar.
A steering damper (or stabilizer) is meant to prevent or greatly reduce the chance of tank slappers. Some bikes are more or less susceptible to tank slappers based on the geometry and what you do to change that (for example lowering the front end and raising the rear by a lot). Having had a couple of tank slappers I have a steering damper on every bike. All my bikes except for my first one has had one. Granted I had one last year on my zx6r at about 100-110 mph, which has a steering damper, but that was mostly due to poor geometry setup. It has been corrected and hasn't happened since :)
 

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Tank slappers??? Speak English!! lol
Seriously?? How long you been riding for?? :nerd:

Here is an example of a tank slapper from a CBR1000 at one of my local tracks. Don't know for sure who this guy is but I imagine he **** himself. Thankfully the 2 I've had (one on the street, one on the track), also did not result in crashes, but I know of quite a few examples where others were not so lucky.

 

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I almost had a tank slapper on the R3 several months ago when the front hit a bump in the road when I was accelerating hard out of a corner, so it can happen. In my case the bars moved from side to side twice and then stabilized (right, left, then back to normal). It happened so fast that I didn't have time to react at all, which was probably a good thing as it let the bike sort itself out.

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I almost had a tank slapper on the R3 several months ago when the front hit a bump in the road when I was accelerating hard out of a corner, so it can happen. In my case the bars moved from side to side twice and then stabilized (right, left, then back to normal). It happened so fast that I didn't have time to react at all, which was probably a good thing as it let the bike sort itself out.

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Yeah that's not bad, I get those all the time at the track especially on the zx6, or on my old 1198. If it's just a quick little wobble like that it doesn't slow me down any, but the steering damper is what usually prevents that from turning into a tank slapper like the one in the video. Being light on the handle bars helps a lot too.
 

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Discussion Starter · #20 ·
I almost had a tank slapper on the R3 several months ago when the front hit a bump in the road when I was accelerating hard out of a corner, so it can happen. In my case the bars moved from side to side twice and then stabilized (right, left, then back to normal). It happened so fast that I didn't have time to react at all, which was probably a good thing as it let the bike sort itself out.

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Questions:
1. What suspension changes to the bike have you made up to that point?
2. What geometry changes had you made up to that point?
3. Your riding weight?
 
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