Can i get some suspension definitions?
Thread Starter
|
Road Master
Joined: Jul 2010
Posts: 963
Likes: 1
From: Bellefonte PA
Can i get some suspension definitions?
Looking at upgrading both ends of my bike and just looking for a little clarification. Basically, from what I gather, travel is distance from fully extended to fully compressed. Compression is getting shorter, rebound is getting longer, damping is the rate at which these events occur. What I keep seeing that I don't really understand is sag. What exactly is the definition of sag? How, if at all is it related to preload? Sorry if this is dumb, but I need to know and I don't. Thanks.
Ultimate HDF Member
Joined: Jan 2008
Posts: 6,532
Likes: 132
From: SoCal
Looking at upgrading both ends of my bike and just looking for a little clarification. Basically, from what I gather, travel is distance from fully extended to fully compressed. Compression is getting shorter, rebound is getting longer, damping is the rate at which these events occur. What I keep seeing that I don't really understand is sag. What exactly is the definition of sag? How, if at all is it related to preload? Sorry if this is dumb, but I need to know and I don't. Thanks.
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,898
From: Bedford UK
Not dumb, so pleased to help if I can.
Travel is as you describe, fully extended to fully compressed - in other words when the suspension cannot get any shorter! Sag is the amount the suspension compresses, from fully extended to when you sit on the bike when it is stationary. The optimum is one third of total travel. That gives 2/3rds to absorb bumps plus a third to cope with potholes!
Preload is compressing the springs to get the sag right, so they resist the weight of bike and rider. On some shocks there are 2 or 3 positions of spring pre-load, while a few offer much finer adjustment. Not many forks have pre-load adjustment.
Damping is what stops the springs bouncing out of control. If the springs were left on their own, when they hit a bump they will compress, then extend and continue doing that several times before settling down. In other words they would pogo along and make us seasick! Damping limits how much the springs can move and getting it right is a black art.
Hope that helps.
Travel is as you describe, fully extended to fully compressed - in other words when the suspension cannot get any shorter! Sag is the amount the suspension compresses, from fully extended to when you sit on the bike when it is stationary. The optimum is one third of total travel. That gives 2/3rds to absorb bumps plus a third to cope with potholes!
Preload is compressing the springs to get the sag right, so they resist the weight of bike and rider. On some shocks there are 2 or 3 positions of spring pre-load, while a few offer much finer adjustment. Not many forks have pre-load adjustment.
Damping is what stops the springs bouncing out of control. If the springs were left on their own, when they hit a bump they will compress, then extend and continue doing that several times before settling down. In other words they would pogo along and make us seasick! Damping limits how much the springs can move and getting it right is a black art.
Hope that helps.
Thread Starter
|
Road Master
Joined: Jul 2010
Posts: 963
Likes: 1
From: Bellefonte PA
So when measuring to set sag if my end measurement is with me sitting on the bike, what is my starting point? Is it from the point where it sits with the weight of the bike on the suspension, or is it from the bike jacked up with the wheels off the ground?
I'm having a hard time wording the question, hopefully someone understands what I mean.
I'm having a hard time wording the question, hopefully someone understands what I mean.
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,898
From: Bedford UK
I sorted out my rear suspension, which made blindingly obvious how bad the front is. I suspect many owners find that out the same way!
As qtrracer wrote, there are two sags, however the one that is important is when you sit on the bike, measured from fully extended, wheels off the ground. If you ride 2-up most of the time, measure sag with both of you on the bike. That can be fun unless there is a third pair of hands!
So when measuring to set sag if my end measurement is with me sitting on the bike, what is my starting point? Is it from the point where it sits with the weight of the bike on the suspension, or is it from the bike jacked up with the wheels off the ground?
I'm having a hard time wording the question, hopefully someone understands what I mean.
I'm having a hard time wording the question, hopefully someone understands what I mean.
Last edited by grbrown; May 5, 2012 at 03:44 AM.
Ultimate HDF Member
Joined: Jan 2008
Posts: 6,532
Likes: 132
From: SoCal
So when measuring to set sag if my end measurement is with me sitting on the bike, what is my starting point? Is it from the point where it sits with the weight of the bike on the suspension, or is it from the bike jacked up with the wheels off the ground?
I'm having a hard time wording the question, hopefully someone understands what I mean.
I'm having a hard time wording the question, hopefully someone understands what I mean.
Thread
Thread Starter
Forum
Replies
Last Post
parabellum_9x19
Sportster Models
31
Oct 11, 2013 02:31 PM
baka1969
Sportster Models
62
Sep 8, 2013 07:16 PM
