Rider Sag Sanity Check

[milesprwr]

With the addition of the aux tank on my dale's rack, I thought it might be worth checking the state of my rear suspension with the tank topped off.

If I understand correctly, the 2013 NC700X has ~5.9 inches (15 cm) of rear wheel travel and general rule of thumb is 30 - 35% of wheel travel should be the target rider sag: 15 cm * 0.30 = 4.5 cm

My first measurement was on the center stand from the middle of the rear axle bolt to the top light grey lip of the givi pannier rack: 54.5 cm

Second measurement was me geared up on the bike, giving my full weight and trying my best to prevent my feet from taking any weight. Again, measuring from the rear axle bolt to the top light grep lip of the givi pannier: 39 cm

Rider sag = 54.5 - 39 = 15.5 cm ??

I must be messing something up here since my measured rider sag exceeds the claimed rear wheel travel? What could I be missing?

Here's a short clip of myself testing rider sag.

 

[dduelin]

Distance from axle bolt to top of rack with bike on center stand = X
Distance from axle bolt to top of rack with bike on it's wheels but no rider = X1
Distance from axle bolt to top of rack with rider on bike on it's wheels = X2

X - X1 = static sag
X - X2 = rider sag

 

[milesprwr]

Distance from axle bolt to top of rack with bike on center stand = X
Distance from axle bolt to top of rack with bike on it's wheels but no rider = X1
Distance from axle bolt to top of rack with rider on bike on it's wheels = X2

X - X1 = static sag
X - X2 = rider sag

Thanks @dduelin! Is the 5.9 inches / 15 cm of wheel travel correct? I should be shooting for 15 cm * .3 = 4.5 cm of rider sag?

 

[dduelin]

Suspension settings are suggestions and I believe rider rear sag can be between 3.8 and 5 cm which is .25 to .33% of the 15 cm of OEM rear suspension travel.

 

[milesprwr]

I see, looks like I need a stiffer spring at this point. Currently using about 75% of available preload on my RSV4 shock.

 

[dduelin]

I see, looks like I need a stiffer spring at this point. Currently using about 75% of available preload on my RSV4 shock.

What is static sag? 0 - 5mm I agree with increasing spring rate but 5 - 10mm should be ok.

 

[milesprwr]

What is static sag? 0 - 5mm I agree with increasing spring rate but 5 - 10mm should be ok.

Alright I just had my son help me with measurements.

Static sag = 2.2 cm
Rider sag = 5.7 cm

I saw that you were using mm as your units, was that intended? If mm was intended, that means my static sag is too high?

 

[dduelin]

Alright I just had my son help me with measurements.

Static sag = 2.2 cm
Rider sag = 5.7 cm

I saw that you were using mm as your units, was that intended? If mm was intended, that means my static sag is too high?

Just convert cm to mm. I used cm in post #4 because you earlier reported in cm. I prefer to use mm but it shouldn't make any difference. Your static sag is 22 mm and rider sag 57 mm, latter at 38% being a little more than suggested. At this point try and adjust preload to arrive at your target sag then measure static sag again. With rider sag where you want it then 0 - 5 mm static sag indicates the spring rate is too low or too soft, 5 - 10 mm of static sag indicates the spring rate is in the ball park for your weight, 10 or more the spring rate is too high. Again, these are suggestions and riders may have their own preferences. As the shock was not built expressly for you then might have to make some allowances for how things measure up.

 

[milesprwr]

Thanks again for the explanation. I think I understand now.

Adjusting preload will impact static sag much more than rider sag. My current rider sag (57 mm) is off from the "ideal" rider sag of 45 mm by 12 mm. Accepting a static sag minimum of 5 mm means I have 17 mm of static sag to play with.

Only if preload effected static sag and rider sag 1:1 would I achieve desired rider sag with a 10 mm static sag.