Rear Sag 101

Make no mistake, the rear end sag setting on your motorcycle should be agenda point numero uno for any conversation you're having on bike set-up or handling.

If you are thinking of making suspension changes and don’t know your sag settings are correct, then you are wasting your time and money. The amount of riders who want to throw money at trick suspension components without checking sag first is always mind-blowing to us, considering simply getting your sag correct could be the cheapest performance upgrade you’ll ever make!

Sag is so important because it configures the geometry of the motorcycles rear end and therefore dictates how well it can perform in corners, ruts, braking bumps and jump faces. Get the sag wrong and you’ll notice all sorts of strange behaviour from your bike and not just at the rear; incorrect rear sag will impact your forks too! No fancy suspension component in the world is capable of overcoming the issues created by incorrect sag settings.

There are two types of sag; race or static.

Race sag is the amount the suspension ‘sags’ with the weight of the rider in the normal riding position.

Static sag is the amount the suspension ‘sags’ just under its own weight.

Both are important, but always set your race sag first. The normal riding position should represent where you spend most of your time, either sitting or standing.

The race sag setting is usually around the 100mm mark. This differs a fair bit from OEM to OEM, model to model, year to year. There are loads of smart people on the internet who dump hours and hours into the new models to work out what feels best; people like Kris Keefer of Keefer Inc. Do your research, read and consume what the smart people have to say, then use this as your baseline. We're also very happy to offer advice and insight if you drop us a message. Measure the set the sag carefully and accurately, because small measurements really do make a big difference!

Once you’ve got your race sag set correctly and to personal preference, measure your static sag.

Static sag tells you if the spring rate is correct for the combination of everything it has to carry; rider, bike, fuel, bum-bag, last night’s curry, the lot.

Too little static sag and your spring is too soft, too much static sag and your spring is too stiff.

It sounds backwards, doesn’t it? But if the sag is too little then you had to preload the spring too much to achieve the correct race sag.

If the spring rate is correct for you, you will be able to get both the race and static sag correct. If not, you need a new spring.

If you cannot get both right with your current spring then prioritise rider/race sag in the short-term, if you're at the track for the weekend for example. But for the cost of a rear spring, dip your hand in your pocket and get the correct spring rate for you ASAP! Springs are available from £90 and considering this is what connects you, the rider, to the ground and dictates so much of your bikes handling; it’s well worth the investment!

Contact A-Spec today to talk about your settings and what they mean.