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kurtcrf450

09 suspension setup woes

8 posts in this topic

This isn't my main bike but id still like it rideable on a track. I'm a c rider 220lbs and it's a stock suspension. The biggest problem is the springs are too soft for me but I was hoping I could get it close while sacrificing in some areas. I know sags never goin to be right and for a while I wasn't concerned as I was rd racing but now I want it for an Mx bike. I have it handling ok but it seems to bounce a lot on hard hits is that.

Is the rebound too hard?

Compression not hard enough?

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Put stiffer springs in front and rear, set all clickers back to factory settings, and set sag at 100mm. Live happily ever after. You can thank me later!

According to the Racetech spring calculator you will need .49kg in front and a 6.0kg in the rear.

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Until the springs match the combined weight of the bike and rider, you're not really going to be able to make much progress with the damping.

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I was worried that was the answer. Sag at 100mm on that bike is what works best?

What about front fork height? Where I have it now is probably going to be effected once I put the right springs in.

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Start by putting the forks 5mm up in the clamps. There is a line on the top of the forks engraved at 5mm.

Fork height and rear sag are just good starting points and can be adjusted after riding to affect handling. I have the same bike as you (2009 YZ450F) and I'm sure you will be very pleased with the end result.

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Trying to race a YZ450 and not having it properly sprung and setting sag is like buying a pair of shoes and not tying the laces (or adjusting the Velcro straps for some, ha). You can still "go" but it will be inefficient and it's only a matter of time until you get hurt.

 

Slight exaggeration, but you get the gist.

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More like buying the wrong size shoes and not lacing them.

 

When the springs are too light for the weight applied, the compression damping has to work harder than it should to prevent bottoming.  Thus, the ride becomes harsher with lighter springs.  Conversely, because the springs are not as strong as they should be, rebound will be too slow with the rider's weight aboard and the wheels on the ground, and if you correct that, rebound when the bike leaves the ground will be too fast.  In all, it just doesn't work well.

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I was worried that was the answer. Sag at 100mm on that bike is what works best?

 

 From web test:

 

"The handling on the YZ seems to come under scrutiny for its turning. We have had turning issues with our bike as well. They were easily remedied by playing with the ride height. First by getting the sag setting dialed for the rider, typically between 100-105mm, then on some circumstances by playing with the fork height in the tripleclamp. That is why these bikes are adjustable, you know. There is not one magical setting that everyone settled on but we seemed pretty happy for riders in the 170-190 pound range with closer to 105mm of sag and the stock fork position at all of the tracks we rode. The whole time we were within one click of stock on all the clickers. After that we rarely fiddled with the bike, track-to-track."

Read more: http://www.dirtrider.com/tests/motocross-bikes/141_0807_web_test_2009_yamaha_yz450f/#ixzz3963v2iuT

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