To measure the sag start by measuring the distance between the mounting bolts at the top and bottom of the shock from centre to centre, this will give you the eye to eye length of your shock. You need to know the stroke length of you shock too.

Alternatively if you know the stroke of your shock use the method shown in the picture to the left.

Sit on the bike in your normal riding position leaning against your immovable object/person and then measure the eye to eye length again. Refer to the table below to get your desired sag amount.

If you need to put more than 3 to 4 turns of spring preload on a coil strung shock you probably need a stiffer spring.

Eye to eye x Stroke		Eye to eye measurement in mm with percentage measurement of sag
		20%	25%	30%	35%	40%	45%	50%
6.5 x 1.5”	165 x 38mm	157	155	153	151	149	147	145
7.5 x 2.0”	190 x 50mm	180	177.5	175	175.5	170	167.5	165
7.875 x 2.0”	200 x 50mm	190	187.5	185	182.5	180	177.5	175
7.875 x 2.25”	200 x 57mm	188	185	183	180	177	174	171
8.5 x 2.5”	215 x 64 mm	203	200	197	194	191	187	184
8.75 x 2.75”	222 x 71mm	208	204	200	197	193	189	186
9.0 x 2.75”	230 x 71mm	218	214	210	207	203	199	196
9.5 x 3.0”	241 x 76mm	226	222	218	214	210	206	203
10.50 x 3.50”	267 x 90mm	249	244.5	240	235.5	231	226.5	222

 

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Sag/Spring rate problem solver

Symptoms: Not using full travel, feels harsh, poor traction while making turns

Causes: Overly stiff spring or compression damping

Solutions: Lower air pressure or soften coil springs; reduce compression damping

 

Symptoms: Bottoms out, soft throughout travel

Causes: Spring rate too low throughout travel or too little compression damping

Solutions: More air pressure or stiffer coils springs; increase compression damping

 

Symptoms: Excessive sag, feels soft initially but does not bottom out

Causes: Initial spring rate or preload too low

Solutions: Increase air pressure or spring preload

 

Symptoms: Harsh over small bumps but uses full travel

Causes: Initial spring rate or preload too high, or too much compression damping

Solutions: Lower air pressure or install softer springs; reduce compression damping; reduce spring preload

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