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Discussion Starter · #1 ·
hi guys had my first outing on my 848 street fighter loved it but found it really soggy
i understand the most of the owners manual but the preload confuses me , it states 23mm how do i measure it, is it the amount the shocks sink when I'm on the bike compered to the amount when the shocks are fully extended.

help folks

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Welcome to the forum!

Yea, you've got the general idea on how to measure sag OK. On street bikes because the shock springs are so stiff, there are truly three numbers you need to acquire in order to get an accurate reading.

The best way to take these measurements are with a few friends and a decent tape measure. Most people use millimeter tape measures, so the numbers I'm working with here will be in MM. Simply hook the end of the tape measure onto the axel in a place it won't move and find a place on the tail fender which is directly parallel to the axel, which doesn't move. Mark it with a grease pencil or something that rubs right off, so you don't forget.

First measurement will be with the rear wheel off the ground. This will be the A measurement.
Second measurement will be with you on the bike and someone holding it. You will pump the shock by sitting on the seat hard. That measurement will be B
Third measurement will be with you on the bike, but don't pump it. In fact, have someone pick up the tail a bit and let it go. That measurement will be C

So the numbers will kinda look like this.

A 360
B 330
C 335

First thing to do is find the average of B and C. In this case it's 332.5.

Next you subtract 332.5 from 360 = 27.5, which isn't a horrible sag number.

Some people talk about static sag, which is the same measuring procedure, but without the rider on board. It's great for determining if the spring rate is right for you. However, rider sag is the critical element and is what your 23mm number is coming from.

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Ducati engineering first determines the correct front and rear ride height for good handling based on their test rider's evaluations. In order to select the stock spring stiffness they need to make an assumption about the rider's weight. So they chose 160 lb. to be their standard rider. When a 160 lb. rider sits on the bike, the rear ride height is correct AND the resulting sag places the rear suspension at one-third of its range of travel.

A measurement of the length or number of threads showing above the locking ring nut is specified by Ducati (23mm in the Owners Manual) to help in returning to the factory settings, again for a 160 lb. rider.

If your weight is significantly more than 160 pounds then the bike rear ride height will sag under the additional weight and cause the soggy handling that you describe.

So you need to adjust the spring preload to achieve the correct ride height (sag).

Increasing spring preload will only increase a bike's ride height at the price of reduced available suspension travel. It has no effect on either suspension stiffness or compliance.

Ducati riders who weigh 180 pounds or more will need to change to stiffer springs to place the suspension at the correct ride height as well as at the one-third point of its range of travel, and also increase damping to preserve the bike’s handling.

Another use of preload adjusters is to temporarily maintain ride height when carrying a passenger.
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