I have been wondering the same thing for several months. As I watch the posts and research numerous suspension guides, I find conflicting answers to the dilema. Ohlin's suspension guide says sitting in the riding position. KYB says standing on the pegs. Most don't specify, those who do seem to be devided about equally. I went with standing on the pegs because I ride mostly desert where standing is the predominant riding position.
Bulldog, I think that it is really less important as to how you do it, than that you compare apples to apples. If you take the measurement standing, always take it standing, or visa versa. IMHO I feel that sag numbers can be manipulated up and down to meet your individual needs.
Start at 100mm (measured however you like), then try increasing and decreasing until you find the spot that works for you. I know tuners who never check sag, they go exclusively by spring length and rider feel. Don't get too caught up in it.
I personnally like the standing measurement, as it gives at least some consistancy to the measure (that is hardly precise at the best of times).
Set you 'race sag' while on your bike in the attack position. To do it properly you need someone to help you steady the bike, just after you have rolled a bit while moving the suspension a bit comming to a nice slow stop (no braking). This will have the bike in the proper position to measure the sag.
Make sure your front springs are proper and set before setting the shock.
Some like to measure shock sag by themselves, and they will be close, but no cigar. Simply reaching around to measure can throw it off.
Checking the unladen sag of the shock, after you set the race sag proper, will give you the info you need on the spring.
I don't think it matters, sitting or standing, as long as you are in the "center" position of the bike.
BTW...go back and check the front again!
I think it's a whole bunch easier to get consistent results by standing. That way your weight will always be on the same spot (the footpegs). Just moving your butt on the seat will throw the sag off by as much as 15 mm.
We can be off more than that, Anssi. But it can also happen when standing. Imagine yourself going through whoops. You are definately standing, but where is your weight? Ok, now that I hope you see my point, lets imagine that we can be too far forward or rearward no matter sitting or standing.
The "Attack" position is what you want. YOUR attack position should be a constant positioning. We tend to get a feel for where the center of our bike is. Whether sitting or standing, our regular attack position should be the same, or very close. I find that I can sit and go back to the same postion each time. Same with standing. I still contend that there is no difference sitting or standing, just a matter of having our weight consistantly in the center of the bikes geometry.
However, do you agree that on a modern MX bike, the weight distribution while in the attack position is very nearly, if not exactly, the same as when you're standing on the pegs and not holding on to the handlebar?
That's why I do my sag measurements while just standing on the pegs so I can keep them absolutely consistent (since you can do zero maintainable weight transfer while standing on the pegs and not holding on to anything).
Ah, but with that procedure, you are slightly rearward from your attack position, abeit a consistant stance. I'd suggest holding the handlebars in normal attack positioning. That is where we ride, unless you are setting up for no hander-landers. <shrug>
Pick the way you can repeat the best , you are after a measurement you can repeat every time. Once you find a measurement that handles like you want then you can repeat it when you need to. ....just my opinion.
Originally posted by P_Taylor Pick the way you can repeat the best , you are after a measurement you can repeat every time. Once you find a measurement that handles like you want then you can repeat it when you need to. ....just my opinion.
This is what I was trying to get at...the method is less important than the consistancy. If you use the standing method, with hands off bars, yes you will have slightly more weight rearward...simply take this into consideration and instead of setting sag to 100mm, try maybe 105mm. The number is a guideline and should be used as such, not gospel. If 105mm measured standing works for you, its right, if not try more, or less until you get to the point where you are comfortable. JMO (shrug)