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Suspension help for '05 450

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I have an '05 CRF450 and have a few suspension questions. At this point I only know enough to be dangerous. I weigh 155 and ride mostly mx at the expert level. I changed springs to 5.2 in the rear with 95 mm sag and .44 in the front with 395 cc of oil (I started with 385 but was bottoming too much). These are the recommended springs for my weight. The valving is stock.

Overall it works ok, but the front seems to chatter over small breaking bumps and the rear seems to kick on rebound. Fussing with the clickers hasn't helped much. I'm not really sure which way to go. Any of you suspension guys have any suggestions as to what direction to go? I think I need to revalve, but don't want to if I can fix it with clicker adjustment.

Any help is appreciated.

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durkot,

Try posting on the "Suspension" forum, under technical forums. There are a few good suspension reps who chat there. You might get quicker responses.

Hope that helps,

--SAWDADDY

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Who recomended to you that you go to softer springs?? even at 155 lbs (With out gear on) you sould be real close with the stk springs, especially if your riding at the A level . Most everyone over 180 goes to a 49kg fork spring with the stk rear. I recomend going back to the stk fork spring, I feel with a 44 kg front spring your front is riding to low in its travel and giving your bike a un-balanced feel, that is why your back end is kicking. (start with 385 also.) I hope this helps!! Troy

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Who recomended to you that you go to softer springs?? even at 155 lbs (With out gear on) you sould be real close with the stk springs, especially if your riding at the A level . Most everyone over 180 goes to a 49kg fork spring with the stk rear. I recomend going back to the stk fork spring, I feel with a 44 kg front spring your front is riding to low in its travel and giving your bike a un-balanced feel, that is why your back end is kicking. (start with 385 also.) I hope this helps!! Troy

Ditto that...

Id have you put the stock springs back on there...

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Thanks for the help. I was thinking that the front end may be down to far in the travel and that was causing the harshness in the front end. Like I said though, I know just enough to be dangerous and wasn't sure.

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I will probably switch back to the stock front springs, but I will have to do something different with the rear. The reason I resprung in the first place is because I could not get the proper sag with the stock rear spring. To get to even 95 mm of race sag I had amost 50 mm of free sag.

I think I will try sticking with the softer rear and go to stock on the front and see if it the inbalance is too much. If so I will try something in between the stock and 5.2 in the rear.

I appreciate all the help. I don't know what a lot of us would do without this forum.

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Well...hold on just a minute.

Stiffer springs will help to solve some of your problems, but it may introduce other concerns.

Let's cover some basic issues here before you jump to any conclusions.

First of all, the rear end of the bike will kick when the energy within the shock spring is released too quickly. In other words, the back end of the bike is moving forward and faster than the front end of the bike. Or you could say that it is "unloading" too quickly.

This is simply caused by not having enough rebound damping in the shock, or more specifically, the rebound rate is not in accordance with the spring rate.

Now, here's the tricky part. Sometimes when you introduce a rebound rate into a shock to keep kick from occurring, you lose other benefits. The biggest concern is the recovery rate - the rate in which the suspension can return the wheel back to the ground in order to serve its purpose. For the rear, the purpose is usually power delivery. If the rear wheel skips, you slow down.

The other consideration is the ability to load and unload for the purpose of hoping or seat bouncing the bike, which is not something that many riders need for trail riding but can be very advantageous for the tracks or a repeated terrain.

This means compromise, as are many things involving suspension setup.

Now the other issue.

When a shock or fork rides lower into the travel, usually because of a softer spring, there is a greater chance of the rider getting into a situation where the shock or fork can blow through the remaining travel, hence bottoming, which in turns introduces the situation of unloading too rapidly.

You can correct this in three ways. 1. Add more compression damping so that the shock or fork does not bottom, (as much) 2. Put in a stiffer spring, or 3. Add more rebound.

If you can't get within the proper sag parameters for the rear, a stiffer spring will only make matters worse. Therefore it becomes a matter of finding a good balance between compression and rebound damping and the level of flexibility you want with the bike with consideration to the terrain.

As for the front, you can only turn a bike by allowing the front to dive or by kicking the back end around (usually via the rear brake). If the front is too stiff, via the spring(s), the bike will push. Not a good thing considering a tight track.

On a four stroke, your need to manage the clutch in a corner is more critical than on a two stroke. You may at many times not have the option of kicking the back end around via the brake, leaving your turning demands on the issue of dive.

Now, softer springs in the front will also mean that the bike will ride lower. Not by much, but by some. The other issue with softer springs is the decrease of the "recovery rate" for the front end; something that becomes very very important when dealing with high-speed sections or whoops. In other words, what you want to minimize is to have the front wheel recovering when you're going into another bump. Imagine the effect of 31 lbs. of un-sprung weight moving in the opposite direction when it (and you) encounter the next strike. This has a huge effect on forward speed and rider fatigue, but it often goes undetected by most self-tuners.

With that, stiffer and softer springs will each have their benefits and down falls. In my opinion, and on my bikes, I run a rear spring that I can get 90 to 110mm of rear sag as long as I can remain within the parameters of the spring and shock design. I can do this with either a 5.2 of 5.4 at a rider weight of 170. I switch between the two for various tracks and other needs.

For the front, I run .44s, which is soft but it yields more benefits on trail and track than what I gain by running a stiffer spring. However, I run very little rebound in my forks and have my compression damping set at a rate (curve) that is right at the edge of...well, too much. This curve or rate causes the fork to ride a bit higher than what you get with factory settings, but still allows the fork to move into position before the apex of the corner. Additionally, I also switch between .44 springs that offer linear or non-linear rates (a long story but a worthy consideration).

The bottom line is to understand that spring selections are usually associated with ride heights and balance, and sometimes recovery rates, but should seldom if ever be considered to resolve excess oscillation, (movement). Whereas compression damping should be used to control compression rate and often bottoming, keeping in mind that a bike that often feels stiff and out of control is usually corrected by adding more compression damping. In other words, any suspension system that moves around more than the bump height is detracting from forward speed.

Hope this helps.

DaveJ

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I bet your fork rebound (flathead screwdriver on the bottom of the fork) is set too hard/slow.

At your weight and ability I would use the stock springs front and rear, and 100 mm sag in back. The 5mm extra will help with the rebound (less stored energy in the spring to kick back), won't jar your teeth on the small stuff and still take the G-outs.

Put your rebound settings in the middle, front and rear, and go from there.

I agree, as I had similiar complaints with the stock springs at my weight - 175lb. I tried 95mm sag and it was unbalanced and overloading the front, making the small stuff chattery...reset to 102mm and it was better and the bike took a more level 'set' going into corners hard. I also went out one click on rebound in the front and the forks loosened up and tracked better over braking chop. If you are running the stock rebound with lighter springs it probably is too stiff on rebound. I'm also in two clicks on compression up front, as running it stock had the front hanging down too far and on fast 4th gear straights with chop it was too harsh..going stiffer made it plusher. I am getting it revalved though, as it can definitely be better than any setting I have tried.

As far as the rear rebound, I just need a revalve to get it right. At stock, 7 out, it is too fast and the rear end feels loose in sweepers with rolling bumps while hard on the gas, and won't 'set' and bite in. If I go in two clicks I can cure that and rail those, but then kickers on the face of jumps leave the rear feeling 'dead' and it doesn't recover fast enough in whoops making it harsh and kick. After testing two days and trying a lot of settings with rebound, LSC, then HSC I can't come to a setting I'm happy with all over the track.

Overall, the valving isn't bad until I start pushing it hard, and my novice friends think it is great at the last settings I reached, but I think at fast Intermediate speed or better it could be a lot better...the stock setup just isn't ideal for faster riders. My stuff is going to Factory Connection soon.

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i know is sounds like blasphemy, but maybe you should check out the settings that mxa run. I know they can sometimes chat a load of bs, but they ride and race every week and have done for decades, so they really know all the bikes inside out. I think they recommend .49 springs, 375cc's of oil, and around 10 all round on compression and reboud both ends (2 out on high speed). I set it like that and it feels fine. I am 16 pounds hevier than you however.

Good luck man

Chris

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