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Setting the sag


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I have a 2005 CRF450R, the guy I bought it from had the suspension dialed in for a 180lb rider. I weigh 150-155. I feel like I don't get as much air as I should when I hit jumps.

How do I set the sag? Will this even help? What should I do?

I ride motocross btw.

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Setting the sag should be one of the first things that you do when you buy a bike. 😏

Here is how:

Setting Up Your Dirt Bike Suspension

The first thing to do when setting up your dirt bike suspension is to put the rebound and compression clickers for both the forks and rear shock in their standard position (your owners manual should tell you how many clicks out is standard), if you don't have the manual just set them halfway between hard and soft.

If possible find out what the standard rear spring was for your bike and make sure that's what is in it now. If you've bought your bike secondhand and the rider who owned it before you was heavier or lighter than you or was particularly fast then they may have put a different spring in it which can make dirt bike suspension tuning difficult, this can be the case for the forks as well.

To set the static sag on the rear shock you first need to set the preload.

Back off the locking ring and then you either tighten or loosen the main ring to increase or decrease the preload on the shock.

Put the bike on a stand with the rear wheel off the ground and measure from the axle nut to a point roughly above it on the bike (say, a mounting bolt for the muffler or a part on the rear subframe), now take the bike off the stand and let it stand upright.

With the bike off the stand now measure the distance between the axle bolt and the point on the bike itself.

Subtract that measurement from the distance measured when the bike was on the stand, there should be about 25mm of sag, if there's more than that wind up the preload or if there's less then back it off. This measurement is called static sag.

Now to set the laden sag (race sag). Take note of the measurement with the bike standing upright. Now with all your riding gear on sit on the bike in the attack position (head roughly over the crossbrace, elbows up and out and feet up on the pegs), have someone hang onto the bike for you and take a measurement again. The amount of sag should be between 90mm and 110mm, again if it's more or less then adjust the preload etc.

You should be able to get it set up approximately to those figures, if it's way out on either then that can indicate that it either has different springs than standard (if you bought the bike secondhand) or that you're heavier or lighter than the model used by the bike manufacturers. They base their settings on a theoretical rider who is about 5'10" tall and about 85kg.

These are just rough figures, read your owners manual for the bike, the japanese manufacturers have a decent section in their manuals on dirt bike suspension.

Taking some time to learn about and set up your dirt bike suspension costs nothing and can really improve your lap times.

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Before I respond, you say the guy you bought it from had the suspension "dialed" for a 180lb rider. What exactly was done?? If he had it revalved and resprung, then you will never get the sag set correctly. Here is why. There are more than one measurement regarding the rear suspension, those being sag and static sag. Sag is defined as unsprung height (bike off ground on a stand) minus ride height with rider in full gear. That will give you your sag measurement, which should be around 105-110mm on that bike. Then you have static sag, which is the unsprung height minus riderless bike measurement. In other words, your measurement is taken with the bike on the ground, with no rider. I believe the static sag measurement should be around 25-30mm. Maybe a little less or more on that one. Now the problem is, if he had the bike resprung for his weight, you are way out of the weight range for that spring. If you were even able to back the preload on the spring off enough to get your sag correct, which I doubt you could anyway, your static sag would now be way off, and thus the suspension geometry is all wrong. Both sag and static sag have a major impact on how the bike handles. So, the bottom line is, the bike must be sprung correctly for your weight before you can set the sag properly. Hope this helps.

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I agree with IKE, not only are the springs set up for a heavier rider but the valving is probably set up to match the heavier springs. Who knows what level of rider the guy was.

It would be nice if you could find out exactly what was done to the suspension. Some people think they can “dial in” a bike for a 180lb rider with clickers and preload. A good way to find out is by setting the sag per the manual. If you can get the race sag and static sag set correctly at 155lbs, your spring is probably stock.

If not, maybe you can find someone to trade for stock forks and shock. Good luck.

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