Suspension Sag Adjustment
Recently I posted an overview on air suspension setup which spurred on a flurry of questions about sag. First of all what is sag? and how do I set it up for my riding style?
Sag is the amount of suspension that is used simply by sitting on the bike in a neutral position. This is the amount of shock compression while your body weight is centered over the front a rear suspension.
So, how to you set it up? Depending on your riding style, the amount of sag which is optimum will differ. Personally, I run about 20% on an XC bike and 30% on a DH/FR bike. For the purpose of this demonstration I have used a 2009 Norco Shore 1. The Shore has 7″ of rear travel so 30% sag is equal to 2.1″.
The First step in sag setup involves measuring the height of the bike from a reference point. I like to use the distance from underside of the saddle to the ground. In this case the height measured 35″. The bike has a total of 7″ of travel so when fully compressed this length will decrease to 28″. With 30% sag, the measurement will be slightly under 33″
If you are using an air shock then you can adjust your sag with your air pressure. Increasing air pressure will decrease sag while decreasing pressure will increase sag. If on the other hand you are using a coil shock, you will need to change your spring weight to alter sag.
I hope this clears things up a bit.
Dustan
April 14th, 2009 at 8:10 AM
If you are upgrading your shock how do you size the spring for weight? I understand the stroke length, but haven’t been able to find any info on how to choose the weight ( 400lbs – 550lbs etc).
April 14th, 2009 at 3:46 PM
Unfortunately, this is not a cut-and dry answer. The correct spring rate for your frame will depend on a few different factors. These are rider weight, compression ratio, type of shock, stroke length and riding style. There is no easy way to calculate spring weights, the easiest way is to look at what comes stock and adjust from that point, or find other people that ride the same frame and use that as a reference.
July 13th, 2010 at 10:34 AM
Hi, can i get an air shock to fit my norco shore 3 2009 frame? i cant find any dhx air shocks that fit the right size
matt