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There's always a lot of talk about rear shock sag and very little mention of fork sag. I've seen a few numbers in the 35-45mm range for motocross, and 55-65mm for offroad riding. Many bikes i see don't sag at all in the front end and i'm just trying to understand if motocross bikes are all set up that way or if they should sag a bit in the front. From a physics standpoint, it would make sense that the front end should sag a bit when the rider is on the bike.
I have AER48 forks on my Alta MXR and the recommended air pressure settings produces very little (if any) sag in the fork with me on it. I noticed the same case for the highly modified air forks on my KX450f. There is about 35mm of sag in the open chamber forks on my KX125 and they feel noticeably more plush and track the ground better than both of the other bikes which have air forks. And yes, the fork springs on my 125 are proper for my weight.
Should i try softening up the pressure on the AER48 until roughly 35mm of sag and then go stiffer on compression and move the forks down in the clamps to compensate? Right now i'm battling having a vague feeling in the front end.
I have AER48 forks on my Alta MXR and the recommended air pressure settings produces very little (if any) sag in the fork with me on it. I noticed the same case for the highly modified air forks on my KX450f. There is about 35mm of sag in the open chamber forks on my KX125 and they feel noticeably more plush and track the ground better than both of the other bikes which have air forks. And yes, the fork springs on my 125 are proper for my weight.
Should i try softening up the pressure on the AER48 until roughly 35mm of sag and then go stiffer on compression and move the forks down in the clamps to compensate? Right now i'm battling having a vague feeling in the front end.
But to get the ball rolling, I think the main issue with fork sag is to do with the amount of friction in the forks. They do not move as freely and accurately under smaller loads as the rear end. Meaning sag readings and repeatability can vary as much as 5/6mm compared with the rears ends 1/2mm (providing everything is mechanically sound).
I've played around with fork sag on my RMZ450. Even when reducing pre load and dropping the spring rate, it's had a very minimal effect on the fork sag reading.
So my advice would be to go on how it feels out on the track, as opposed to the numbers you are getting at home. I think fork sag can be used as a rough guide, and you definitely should have some sag, at least 40mm. But I wouldn't get too hung up on it.
So i'm thinking really any small amount of sag in the fork would be beneficial when it comes to front end feel. Of course, adjusting the fork height in the clamps to accommodate somewhat so as to not through off the geometry of the bike.
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