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Discussion in 'Thumpers' started by jimjib, Jan 21, 2003.
I assume that you are looking for the suspension sag?
That really depends on what type of riding you are doing, how much does the rider/luggage weight, and also how fast/far do you plan on riding..
For normal on-pavement commute, with myself and 40lb. of luggage weight (total of 180-190lb.) I set the sag at 1.75-2.5 inches from free bike. I load up the preload for compression (to minimize brake induced diving) and set damping at mid-point... not much chance to take multiple impact from rough tarrain on-pavement.
For off-pavement.. that's whole different issue.. and make great difference what kind of terrain you are riding in... I usually experiment with my mountain bike first.. to see what kind of suspension setup would be suited.
I guess thats the front numbers...with you sitting on the bike, correct? What are the rear numbers?
I like a soft ride up the fire roads...I dont push it hard or launch the thing. I weigh 210 and have added hard bags...just went to a bit stiffer spring also.
Actually your numbers sound more like no rider.
i agree. ordinarily your sag should be set so that, with you on board in your normal riding position and wearing your normal riding gear, your suspension is compressed somewhere around 1/4 - 1/3 of its total travel. so, put the bike on the center stand to unload the suspension and measure from the center of the rear axle to a convenient point on the sub frame or rear body work. then suit up, get on the bike in your normal riding position with someone else helping balance the bike. bounce up and down a couple of times to settle the suspension and compensate for stiction. now have someone measure from the axle to the same point on the frame or bodywork. subtract the two and it should be about 1/4 -1/3 of the total suspension travel. if not, adjust accordingly. this is not exact but just a general rule of thumb. rider sag is diferent from static sag in that static sag is a measure of how much the bike compresses the suspension on it's own. if you have to crank preload up so much to achieve proper rider sag, that you don't have enough static sag then you need a stiffer spring with less preload. conversely if you have to back off so much on preload to achieve proper rider sag that you have too much static sag you need a softer spring with more preload.
the same procedure is used to set sag at both ends.
many people ride around on bikes with improper sag settings or spring rates and never really know the difference and are quite happy with it. but to get the most from your suspension it needs to be set up properly. of course it depends on your skill level and riding style to determine just how important it is.
maybe of more importance is that the sag is properly balanced, front to rear, as this can have negative consequences on geometry. this will have a more pronounced affect, for more riders, than just having wrong sag settings.
have to little sag allows the suspension to top out too often on rough terrain, loosing traction, while having to much lessens the amount of available travel. both situations adversely affect traction, handling and ride quality. it is best to have the suspension working in the proper portion of it's stroke.
Maybe I was not clear the first time..
The sag measurment that I posted first was for on-pavement commuting, not for off-pavement.
I don't know what the pavement is like in other parts of the country, but in my area, it is pretty smooth with maximum bump size of 2-4 inches, some manhole covers, some potholes.. that's it.. not 2 foot dropoffs.
You also have balance front to rear - do your rear sag as Randy says,then put your foot on the rear brake lever and push down on the peg with your foot - the bike should go down level,work on the front to get a balance.Long time since I've done it,please correct if I'm wrong.I am light and always set my bikes up soft,I don't mind the bike moving around,but at higher speeds I get some air time which can give wobbles if I come down crooked.
Lucky I'm getting a new computer next week,it didn't load all of Randy's post,I thought it was an image and didn't wait.
even if you do exclusively street riding your suspension will give you the best handling if set up properly. suspension setup is a huge part of roadracing and your best bet is to setup your suspension so that it will work within it's design parameters. too soft will allow for more hobby-horsing from abrupt throttle changes and braking. too hard will cause poor ride quality and more subtle negative effects on handling. more importantly, maybe, for street use is your damping settings. i would set the sag up as i advised earlier but you can get away with much more rebound and compression settings both front and rear. you will have better control and stability and an all around better handling bike if you set the suspension up properly. it's not a huge issue. as i stated in my earlier post, a lot of people ride around their whole lives without proper setup and never know the difference and are completely happy. but, for me, the KTM has really good suspension compared to a lot of bikes and i like knowing that i have it set up to extract the maximum performance. it all depends on your perspective.
That it true... so why would your perspective of sag setting make a difference to anyone elses' riding???
I think the point is that the sag settings should be set pretty much the same no matter how and where you ride. If your bike has more sag than than the base setting or a ton of preload jacked in to get those settings...you need stiffer spring.
You might be contradicting yourself with that..
I would think that suspension sag setting should vary drastically with riding style and terrain.. also especially with a rider's weight.
Given the fact that my weight 135 lb. is about 25% less than someone 175 lb. which could translate to 10% difference in total weight of rider and bike.
Given the fact that you weight 210 lb. yes, you are right, you definately have more sag than me.
No,the whole point of a sag setting is that it's a constant,the only things that will alter it are your weight or the weight you put on the bike.You alter how the bike responds with the dampening settings,if you have to go back to the springs then something is wrong.
Are you saying that sag should be constant regardless of riding terrain?
Think again, dude..
Yes,you are matching spring preload to your riding weight,you should only need to change it for very extreme conditions or some fine tuning.You might want a softer ride if you only ride on the road,or if you are getting supercross airtime you might go stiffer.When I was riding off road,with my bike correctly set up,I could ride on open very rough terain in 5th gear using up all my 12in travel,getting air time,and yet still have it soft enough to go in under trees etc..My current bike has no rear spring,just an air shock,but the same rules apply.
Bottom line - trust the guys who designed your bike and suspension,if it was made for serious use in the last 20yrs,suspension will be well sorted.
as a general rule...there is an optium sag setting regardless of your weight. You may be able to bring it in with the preload...but if its way out and you have to dial it in with a ton of preload..you need a stiffer spring.
I have learnd one thing about suspension.....its hard to get right.
If you have the preload wound to max,you need a new body,or a new bike.The manufacturers have built the bike with a certain sized rider in mind.So a little guy like me won't feel happy in serious off road use with anything bigger than a 400,but a guy over 6ft and well mucsled will find a 250 a bit wimpy and will go for a 600..A small rider will have the 600 preload wound right off,the big guy will have the 250 at max.
So,yes,you are right,in a way.
by your perspective, i was refering to how important proper suspension set up is to you. some riders are more interested in setting it up properly, others simply don't care and are quite happy with it as it came out of the box even if it's not technically correct for them. my personal perspective has nothing what-so-ever to do with how someone else rides. it's just that proper sag is not that much of a variable. there is just a proper amount to use for a given suspension design. suspension components work most efficiently when used in a given portion of their stroke as a starting point. this is achieved by proper sag settings. this is also why i gave the general rule of thumb as a ratio of suspension travel and not a specific measurement. this ratio does not vary that much from bike to bike even though suspension travel and intended use may. the factory provides preload adjustment to enable a rider to compensate for such variables as rider weight, luggage, passengers and so forth. stock spring rates are for average rider weight and preload changes allow for adjustments to be made to compensate, in a relatively narrow range. for example, lets just say that the stock spring is for a rider of 160 pounds. preload adjustments are designed to allow for riders ranging from 140 - 180 pounds (again just an example, not necessarily accurate). any heavier or lighter than that range and you should be using a lighter or heavier spring. many people mistakenly use preload as a means to compensate for incorrect spring rates. i, myself have used more spring preload (and heavier fork oil) to prevent excessive brake dive (on another bike) but in reality i need stiffer fork springs. yes, in operation, it works to a degree but it is not the correct solution. again, it depends on your perspective. are you satisfied with the suspension the way you have it set up? if so then great. but if you took it to an expert aftermarket suspension tuner (lindeman engineering, etc.)they may very well tell you it was all wrong.
there are a lot of variables in suspension tuning to get it just right. but, sag is just a starting point, then all other varialbes can be adjusted to give the rider what he needs or wants.
I think randy hit the nail on the head.