| Author | Message | ||
     Fresnobuell |
Since suspension tuning is so important I figured maybe a dedicated thread might be of some use. Please post your thoughts, findings and questions here. There are some mighty knowledgeable folks on the Badweb! | ||
| Matteson |
teach me. | ||
| Rodrob |
IMHO, in order to have an intelligent group discussion about anything, one must define terms that everyone can agree to, or at least accept. So... Ride Height, Front - The distance measured in MM, from the bottom of the lower triple tree clamp, to where the lower fork tube meets the axle support, with the forks fully extended. Ride Height, Rear - The distance measured in MM, between the Shock Eye centers, with the shock fully extended. Free Sag - Front - The distance measured in MM, between the top of the upper fork tube dust seal, to where the lower fork tube meets the axle support, with the bike on level ground with no rider. Fee Sag Rear - The distance measured in MM, between a fixed point at the rear axle and a fixed point above on the rear subframe, where a line between these to points would (as much a possible) be perpendicular to the ground, with no rider. Rider Sag - Front - The distance measured in MM, between the top of the upper fork tube dust seal, to where the lower fork tube meets the axle support, with the bike on level ground, with the rider with gear and in position, mounted. Rider Sag Rear - The distance measured in MM, between a fixed point at the rear axle and a fixed point above on the rear subframe, where a line between these to points would (as much a possible) be perpendicular to the ground, with the rider with gear and in position, mounted. Spring Rate, Front - The amount of weight in Kg required to compress the spring 1mm, expressed as Kg/mm. Spring Rate, Rear - The amount of weight in Lbs required to compress the spring 1ft, expressed as Lbs/Ft. Low Speed Compression Damping (usually "Compression") An adjustment to the flow of oil in the fork/shock when being compressed, in lower velocity conditions (like braking), usually made with a needle and seat valve, in increments of "clicks" or 1/4 turns. Higher settings, restrict flow and slow down compression. Lower is the opposite. High Speed Compression Damping (usually "High Speed") An adjustment to the flow of oil in the fork/shock when being compressed, in higher velocity conditions (like sharp bumps), usually made with an internal "Stack" of spring shims. (NOTE - Building the "Stack" is as much art as science and are often tightly held secrets.) Some newer designs (like the BPFs on the new EBR's) have both Low and High speed external adjusters. Rebound Damping - An adjustment to the flow of oil in the fork/shock when rebounding from a compressed condition, usually made with a needle and seat valve, in increments of "clicks" or 1/4 turns. Higher settings, restrict flow and slow down rebound. Lower is the opposite. (NOTE - Because rebound forces are almost entirely subject to spring rate, high speed rebound adjustments are rare. An exception would be race conditions where torque induced anti-squat and wheel spin at corner exit can have significant influence on rear rebound. High end racing shocks can have these adjustments) Oil Level (Sometimes Air Gap) - The oil level as measured in MM in the fork tube, with the cartridge but no spring installed and the fork fully compressed, from the top edge of the fork tube, to the top of the oil in the tube. Typically between 100 and 200 mm. Front Pre-Load (External) - An external adjustment to the initial load applied to the fork spring, expressed in "Turns" (usually 1 turn/mm, post installation in the fork. Front Pre-Load (Internal) - An adjustment to the initial load applied to the fork spring, by an internal spacer, when installed in the fork. Typically 20mm Rear Pre-Load - an adjustment to the shock spring load, in MM, measured from the preload adjusting ring in the no load position, the the ring in the loaded position. Typically 10-20mm. (NOTE - Many high end shocks have hydraulic adjusters controlled with a knob. In this case preload is expressed in "turns". Just a start. Please add to or edit as you see fit. (Message edited by rodrob on September 09, 2014) | ||
| Oldog |
Rider Weight, weight of the rider In his or her riding gear Machine weight, Weight of motorcycle with oil and ~ 3/4 tank of fuel Intended Use? Track, "spirited street", "general" Track is as stated used at riders max capability involves high speed, heavy braking, and various surface transitions/features machine is not used on the street.. Spirited Street the machine is ridden at higher speeds mostly in a non urban setting ( Canyon riding ) it is seldom used for every day transport or utility may see some track use. general bike may be ridden as primary transportation with infrequent trips to canyons and or the track with majority of riding in town at lower speeds Surface Features ? | ||
| Stevenfrye |
A dedicated thread would be nice | ||
| Rodrob |
One of the other difficulties in discussing suspension tuning in general terms, is that one cannot separate the operation of the suspension, from the rider's style/skill and as Oldog pointed out, the intended use of the bike. I know from my own progression as a rider, that most of my suspension "problems" were and sometimes are, problems with my riding technique. These are much more difficult issues to quantify and adjust as one can't simply take 3 clicks out of the weight one has on the bars. That said, I think there are some basic assumptions one can make about suspension setup to provide a baseline for further tuning. I'll post my assumptions after I've had some time to think about them. Be aware that these are my opinions based on my experience and others may disagree. That's fine. I'm always ready to learn. | ||
| Fresnobuell |
Great start so far! I just installed the Showa Cartridge kit, so I am pretty much starting from scratch as far as setup. The first step is to set the Preload, which determines Sag, which essentially is where the fork or shock "rides" in its stroke (it also determines Ride Height per Robs definitions above.). The general rule of thumb for street sag is 25-35 millimeters. Is the beginning measurement supposed to be taken with the front of the bike in the air--ie with the forks fully extended? I have measured about 15 MM between the "fully extended" forks and when the bike is lowered to the ground (no rider.) When the rider is added, there is an additional 25 MM of sag. Can I say my total sag is 40MM with the next step to adjust in more Preload until I get down to appx. 30 MM? | ||
| Skntpig |
You got it. Your free sag is 15 and your rider sag is 40. That's too much. Tighten preload. I use a fairly loose zip tie on the slider to see how much of the available travel I am using. A common misconception is a tighter feeling suspension is better. I would way rather ride a bike that has too low compression and rebound than too much. | ||
| Rodrob |
And so it begins... To clarify, Preload has no bearing on Ride Height as defined above as the measurement is taken with the forks fully extended. I.E. front wheel off the ground. (Note - there is an exception to this when there is a top out spring in the cartridge, which can be compressed by pre-load.) IMHO, adjusting Pre-load to get the desired Sag is a stop gap measure to choosing the correct spring rate. In "Spirited Street" or "General" use as above, it is usually OK within limits. Once you move to "Track" the correct spring rate should come first with Pre-load used to fine tune. | ||
| Stevenfrye |
So sag is the difference between the bike off the ground suspention fully extended to bike on the ground with rider?? | ||
| Rodrob |
Here is a spring rate chart I did to show haw Spring Rate vs Pre-load effects Sag and Travel. Notice that small Pre-load changes get you similar SAG, but the different Spring Rates really show up deeper into the stroke. The casual rider might never get there, but the Racer most definitely would. Be aware that his does not take into account the Progressive Air Spring created by the fork oil level which also drastically effects what happens at the bottom of the stroke.  | ||
| Rodrob |
So sag is the difference between the bike off the ground suspention fully extended to bike on the ground with rider?? That would be Rider Sag, as defined above. Free Sag would be without the Rider as defined above. Different people name Sag differently. That's why it's important to refer to agreed upon definitions and terms. I can already see where I need to edit the definitions for clarity. (Message edited by rodrob on September 09, 2014) | ||
| Fresnobuell |
I am hoping the kit springs are correct. I remember them "fitting" the springs to my weigh and riding style, but I was probably 10-15 pounds lighter back then (not that I couldn't drop some weigh and probably should.) I have zero additional "external" (see I'm reading the definitions! lol) preload in the forks at this point. I will give it some add'l preload tonight. I believe it has 15mm of preload adjustablility....hopefully I end up in the middle of the range somewhere. (Message edited by fresnobuell on September 09, 2014) | ||
| Rodrob |
On your spring, there are hash marks stamped into one end of the spring. One mark is ,95 Kg/mm, 2 is 1.0 Kg/mm, 3 is 1.05 Kg/mm. It's hard to know the correct spring rate without considering a lot of factors. On my 1125R race bike, I run a 1.0 in one leg and a 1.05 in the other, with 1 turn of pre-load. I weigh about 175 in full gear. I run the fork oil at 190mm. The heavier springs with little pre-load gives me the rider sag I'm after and very linear feel down toward the bottom of the stroke, without excessive compression, where the air spring prevents me from bottoming out. This is not the right or wrong way to do this. It just gives me the front end feel I'm looking for at my current skill level. (Message edited by rodrob on September 09, 2014) (Message edited by rodrob on September 09, 2014) | ||
| Fresnobuell |
Too late. Springs installed. I did glance at one of the spings to see if there were any obvious spring rate indicators. Didn't know about the hash marks at the time. Too bad they couldn't just put something helpful like the actual spring rates... | ||
| Fresnobuell |
the Showa kit specifies 100mm...Your lower oil level is for the Progressive Air Spring effect you speak of? WHat's does this do exactly? | ||
| Fresnobuell |
Why is too much preload detrimental versus a heavier spring and less preload? Is this only a factor deep in the stroke? Maybe you explained it already and I am not following.... | ||
| Stevenfrye |
Ok i get the sag and preloading bit in laymans terms how does this translate onto the street or track? Like under steer / over steer, where im living i get rain only afew days per year so everyday is spiretd riding day i use a dual compound dunlap track tires | ||
| Skntpig |
Google will help with troubleshooting: http://www.sportrider.com/suspension-tuning-guide- suspension-troubleshooting-symptoms http://www.sportrider.com/suspension-tuning-guide- handling http://www.sportrider.com/suspension-tuning-guide- suspension-troubleshooting-symptoms | ||
| Rodrob |
the Showa kit specifies 100mm...Your lower oil level is for the Progressive Air Spring effect you speak of? WHat's does this do exactly? Putting aside damping for the moment - You only need enough oil in the fork to supply the cartridge with fluid for damping. Beyond that, the oil level only functions to change the character of the Progressive air spring. A higher oil level, causes the air spring to show effects much earlier in the stroke and be much stronger at the end. The total spring rate in the forks is a sum of the spring and air spring, at a given point in the stroke, due to the air spring being progressive. Therefore, you can adjust the linearity of the stroke, by balancing the linear spring with the progressive spring. If you use a lighter spring, with lots of preload, you tend to need a more aggressive air spring to prevent bottoming. This gives a more non-linear feel to the forks. If you use a heavier spring with less pre-load, you tend to need a less aggressive air spring, which give a more linear feel to the stroke. I have also found that I am able to run less compression damping with this setup as I am not trying to get "stiffness" that the springs should provide by slowing down the stroke with damping. That said, I think this gets a little ahead of the basics. As a starting point, try setting the oil as recommended, the pre-load to get the SAG, put a zip tie on the lower fork tube and ride as hard as you ride. If have a lot of stroke left and the bike feels sluggish on turn in, lower the fork oil 20mm and test it again. If you are using all the stroke and the bike feels twitchy, raise the fork oil 20mm and test. If you need more oil that that, then IMHO your springs are too light. If you are using more than 1/2 your pre-load adjustment, then IMHO, you should consider heavier springs at some point as well. As I said, there is no right or wrong to this. It's a matter of feel for the rider. Also, I do not claim to be a suspension tuner. All of this is just my opinion based on my experience with several tuners and my own research. | ||
| Fresnobuell |
This is all good info...Suspension is something I have always wanted to understand better as it will make for a better and safer ride. I hope you don't mind the simple and possibly repetitive questions. The ONLY time I felt my suspension was "right" was after Dave Moss tuned it at Buttonwillow. I want to get that feeling back again. Do you know approximately how much of the chrome shows when these forks are bottomed out? Oil level in my forks is per the recommedation @ 100 MM. I do like the general feel of this cartridge kit, even with no preload and too much sag...that being said I have been taking it easy the first couple rides. I will also say the Accossato radial is a WAY different feel on the braking side, which is another reason I have been easing slowly as far as my riding. | ||
| Rodrob |
Ok i get the sag and preloading bit in laymans terms how does this translate onto the street or track? Like under steer / over steer, Personally, I just don't think in those terms with a motorcycle, so I don't know how to answer that. I first tune for stability. It does no good to have a bike that turns in quickly, only to be all over the place mid corner and exit. Having the bike balanced front to rear suspension wise, is the single most important goal IMHO. I can adapt to a too soft bike, or a too stiff bike fairly well as long as it's balanced. The 1125R has very aggressive geometry so a balanced setup is, IMHO, most important. Balance =Predictabiliy=Confidence=Speed. This becomes my baseline. Second I tune for braking. Is the bike stable on the brakes? Does it give me confidence? Does the front stay planted as I release the brakes? Does the nose dive far enough and quickly enough to give me fast turn in, but not so much to totally unload the rear? Next I tune for exit. Does it hold a tight line and finish the corner? Do I get enough weight transfer to get exit grip, but not enough to get the front light? Will the rear reach for traction if it spins? This is how I approach it. | ||
| Skntpig |
Rob, You ARE a suspension tuner. | ||
| Fresnobuell |
Second time I have typed in a follow up question for clarification, then went back and carefully read Rob's post and realized the answer is already there. Well done, sir. Between Rob and Race Tech's Suspension Bible, I might have a chance at REALLY understanding this suspension thing! | ||
| Fresnobuell |
Rob, I have been studying your chart above, trying to understand it. It took me a while but I got why the values appeared to be doubled. TWO FORKS with TWO SPRINGS. LOL. Glad I caught this before I posed the question. I posted it up for anyone who might have been wondering the same thing. | ||
| Tbowdre |
anyone know how much fluid is required to move the air spring 1mm… in other words: if I remove say, 10cc of fork oil how many mm will I increase the air spring? | ||
| Rodrob |
Depends on the volume of your fork tube. Best way is to take a little out then measure, repeat until unit you get 10mm lower, then measure removed fluid volume. I say 10mm, because you will not be able to feel a 1mm change. | ||
| Pwillikers |
Rob, an addition to your definitions: Stiction - Some suspensions are susceptible to stiction, A.K.A. static friction, which is the internal friction of suspension components that inhibits free suspension travel. The presence of excessive stiction may be a function of a particular suspension design or it may indicate misalignment of suspension components. In all cases it has a negative impact on suspension performance. To determine the presence of stiction (and factor it into sag calculations), 1. Unload the suspension by lifting on the handlebars or the rear sub-frame and allow it to gently settle to rest without bouncing, then measure the sag, 2. Load the suspension and allow it to gently rise to rest without bouncing, again, measure sag. 3. The average of the two measurements is the accurate measure of sag. 4. The difference between the two measurements is the measure of stiction. Newer suspension designs (and materials) usually present minimal stiction. Older ones, when they were new, showed more. Old, worn out suspensions have little stiction because they have excessive tolerances. Bent or misaligned forks usually show a lot. If significant stiction is present, it is well worth determining why. What is "significant" varies case by case and necessitates a comparison against like models to define excessive for a particular suspension design. (Message edited by pwillikers on September 12, 2014) | ||
| Pwillikers |
I really disliked its heavy turn in when I first bought the Buell. I spent a lot of energy trying to fix it with suspension adjustments. Eventually I replaced the stock Pirellis with Michelin Pilot Powers which solved the problems. I've never looked back. I built a spreadsheet to record my experimentation. It is on googleDocs if anyone wants access.  | ||
| Fresnobuell |
NIce, Paul. I haven't had a chance to digest your findings, but I look forward to it later tonight! Documentation is great! ON the stiction issue, the Race Tech book agrees with the techinque you outline. |
