2010 yz450f spring rates

I have a completely stock 2010 yz450f and am thinking about changing out my springs. I weigh about 215 pounds without gear and race motocross in the vet B classes. I went on to the race tech website and it says i should be at a 5.95kg rear shock spring (5.7 is stock) and a .5kg fork springs (.47 is stock). I'm just curious if these numbers sound correct or if anyone has other suggestions.

I have a completely stock 2010 yz450f and am thinking about changing out my springs. I weigh about 215 pounds without gear and race motocross in the vet B classes. I went on to the race tech website and it says i should be at a 5.95kg rear shock spring (5.7 is stock) and a .5kg fork springs (.47 is stock). I'm just curious if these numbers sound correct or if anyone has other suggestions.

Call Factory connection. They will tell you what you should have. You should also be changing the shock and fork oil. If you have more than 30 hrs or so, its night and day difference.

Those are perfect for your weight

Those rates are about what I'd pick. Of course, everyone has their own preferences, but that will get you a lot closer than you are.

There's some feeling among tuners that the bike is slightly out of balance spring rate wise in stock form, meaning that the front and rear rates don't match each other well in their opinion, but I don't recall the discussion well enough to say which end they felt was soft or stiff compared to the other.

Thanks for the responses. I think I'm going to try the springs and work on my set up. I've never had a re-valve done on any of my bikes so I guess that would be the next step.

I weigh 200 and I'm running a Factory Connection 6.1 in the rear with about 14mm spring compression. I would like to be at about 10mm compression (preload). A 6.3 would probably be better even at my weight.

At 215 I would venture to say a 5.9 will not be stiff enough for you. I started with a 5.9 and found it produced the same sag as the stock "5.7". Better to have a slightly stiffer spring with less preload than too light a spring with too much preload. Max is 15mm.

I'm running .49 up front. .5 would be plenty stiff for you. .49 would probably suffice as these forks have excellent bottoming resistance.

I'm 205 wihout gear and in the middle of some spring testing. I'm a slow vet C, 46 y/o, riding MX only

current valving is a bit stiffer from stock (got the bike used) but not by much (the suspension tuner is a local guy, a good friend of mine)

PC lowering link installed too

The bike feels very harsh with the stock springs.

I recently went to .48t in the front (.47 in one leg and .5 in the other one) and it really helped.

I can feel the front stays higher and the plush feel I wanted is improved

Oil level is stock as of today

I put a 5.8 in the rear but still had to put a solid 10 mm of preload to get the sag in the 105 range. This resulted in 25-27 mm range of static sag

It was an improvement from the 5.7 but not by much

I called FC and they did recommend .49 front and 5.9 rear

I have a 5.9 on order and will see how ti works

At my level, and based on my modest experience, the less pre-load on the spring, the better it works.

So I hope to put 5 or 6 mm and still get a correct race sag

Good luck. There's a lot of variation in springs/rates. The only way to really know what you're getting is to test the spring yourself on known calibrated equipment.

In my experience either the stock "5.7" was actually closer to 5.9 or the Factory Connection "5.9" was closer to 5.7 because they both produced the exact same sag with the exact same preload. Which is to say too much sag @ 15mm preload, 200lbs. and gear.

I will admit I run the sag closer to the 100mm mark per the manual. That's how I ended up with a "6.1" which still comes close to "G-ing" out in certain abrupt faces or seat bounce situations.

I also don't bother with lowering links. I don't see the point lowering the rear of a bike maligned for not turning well enough. Raising the fork tubes is my remedy for that.

Edited by FZ1426

Good luck. There's a lot of variation in springs/rates. The only way to really know what you're getting is to test the spring yourself on known calibrated equipment.

In my experience either the stock "5.7" was actually closer to 5.9 or the Factory Connection "5.9" was closer to 5.7 because they both produced the exact same sag with the exact same preload. Which is to say too much sag @ 15mm preload, 200lbs. and gear.

I will admit I run the sag closer to the 100mm mark per the manual. That's how I ended up with a "6.1" which still comes close to "G-ing" out in certain abrupt faces or seat bounce situations.

I also don't bother with lowering links. I don't see the point lowering the rear of a bike maligned for not turning well enough. Raising the fork tubes is my remedy for that.

Yes, actual S/R can be off from what it is supposed to be but I have my springs tested on a load tester and all were as expected.

out of several dozens of sprins I got tested, one shock spring and one fork spring were off (by about one rate)

I thiink it's more difficult to get consistent sag numbers.

My last check was by myself with the ASV solo scale and i don't think it's the best setup

the ideal scenario is too have a few on hand and just do some trial and error

I'm about to try 0,50 kg front and 5,9 kg rear.

My question is about how much front fork preload? I'm guessing 4 mm. Is what RACETECH says is standard.

Any thoughts?

Those rates are about what I'd pick. Of course, everyone has their own preferences, but that will get you a lot closer than you are.

There's some feeling among tuners that the bike is slightly out of balance spring rate wise in stock form, meaning that the front and rear rates don't match each other well in their opinion, but I don't recall the discussion well enough to say which end they felt was soft or stiff compared to the other.

I recall, because I bought a new '10 and did the spring swap thing . . . the rear spring was generally good for most riders less than 200lbs, but the front springs were generally too soft for riders over 170lbs.

THAT was the basic mis-match.

 

I weigh 165 - kept stock fork springs (perfect for my weight) and switched to softer 5.4kg shock spring.

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