race-tech vs mx-tech spring calculator

I have a 2009 YZ450 that im going to be replacing the springs and rebuilding the forks. I weigh 145lbs....the springs in the bike are stock. the fronts are .47 stock and the rear is 5.5. Which spring calculator is more accurate? they are both showing complete different spring rates for the front and are close on the back.....so what springs would you suggest?

The mx-tech is with gear and the race tech is without gear. So add about 10 lbs to the race tech and your numbers will be pretty close

yeah i know...race tech at 145 pounds (without gear) recommends .45 front springs with a 5.15 rear...mx-tech at 155 pounds (with gear) recommends a .42 front spring with a 5.1 rear spring a big difference in the front

.42, and .45 are real close to the same, I doubt youd even notice

.42, and .45 are real close to the same, I doubt youd even notice

There is a HUGH difference between .42 and .45 springs. Both will probably be too heavy for a 145lb rider. Check your sag numbers to get the correct springs. I have found that the spring generator are usually way off.

how exactly would i measure the front forks for their sag numbers?

I have a 2009 YZ450 that im going to be replacing the springs and rebuilding the forks. I weigh 145lbs....the springs in the bike are stock. the fronts are .47 stock and the rear is 5.5. Which spring calculator is more accurate? they are both showing complete different spring rates for the front and are close on the back.....so what springs would you suggest?

try moto pro suspensions spring calculator. if you're riding enduro stuff, you're probably a .40kg/4.9-5.0.

it just depends on the style, if you're moto/sx it will be a stiffer rate in the forks. generally, if the target weight for a bike is 185, (not sure for your year) then, drop a rate for each 20lbs. lighter. depending on who's making the springs, two rates less for you could be .45's, or .43's, from the stock 47's. for enduro it will be less. the moto pro spring calculator will have softer fork settings than mx/race tech.

ahhh forgot to mention that...i race motocross as a B rider

It makes no difference in most cases between Enduro / HS / or MX. (Sometimes SX riders run in my opinion too stiff a fork spring).

Main difference is damping between the different disiplines.

On your forks you should have about 25% of fork travel in rider sag. Static sag should be about 14%. A variance of 2-3mm is acceptable. I try to get mine as close as possible. If racing MX, er to the less sag side. .40kg fork springs at your weight is not out of the question. I weigh 180lbs but ride a Husky WR150. I run .40kg fork springs with 40mm static sag and 75mm rider sag. Fork travel on this bike is 300mm.

I will say that if I used the Moto Pro calculator and said I was riding MX instead of Enduro that I get the fork spring weight that I am currently using and that gives me the correct sag numbers. If I put in that I ride Enduro , the fork spring is way off. I am using a .40 spring and they said that I should be using a .36. If I punch in Motocross it says .40kg. I think that spring rates should be close on any disipline and only the damping should be the big difference.

0.43 and 5.1 IMO

There is a HUGH difference between .42 and .45 springs. Both will probably be too heavy for a 145lb rider. Check your sag numbers to get the correct springs. I have found that the spring generator are usually way off.

I would think a huge difference would be going from a .42 to a .52

isnt that number the diameter of the spring? so in the original posters case its three hundreths of an inch thicker than the lighter spring suggested?

Or am I mistaken? thanks for clarifying..

The race-tech calculator already factors in the gear. I know this because when I was shopping for a new rear shock spring, mx-tech said 5.6kg and race-tech a 5.8kg.

ok my rear race sag is set at 100mm....the static sag is 56mm....the front sag is 38mm

Edited by bwf8907

I would ck with local shops, riding groups for a good local tuner. Go to him and talk about your skill level, riding etc. I bet he will have used springs that are still perfectly good and can help get you set and save a lot of money. And later if more work is needed you will have a relationship to build on.

56 mm static is way too much

yes it is the bike is like a pogo stick right now...last time i rode it last year i was 200 pounds...im currently 145....im going to be ordering .43 front springs and a 5.1 rear

im 160lb and use .45 on my tried and true harescramble 04crf450. The 08crf450 i just got has .47 springs, although in the range for my weight, there is a MAJOR difference in the feel of the .47 springs vs. the .45.. and we even revlaved the 08 bike for woods similar to the 04. Im not liking the .47 fronts and will likely get a set of .45 and im heavier than you.. I agree as DW posted, that springs should be similar (but correct based on your weight) regardless of the discipline, it is the valving and damping adjustments that gets changed ..

...springs should be similar (but correct based on your weight) regardless of the discipline, it is the valving and damping adjustments that gets changed ..
This may be true for trail riding and soft core mx but i guarantee you once you start setting up a bike for more agressive mx and sx you will feel like chasing your tail finding a setup that stays consistent the whole 30min if you keep the softish springs.

i ride the woods on my 09 crf450. I revalved my suspension and racetech told me to keep the stock fork springs (.46), i am 190 lbs and this was very much so too soft. I went with the .48 and it seemed too harsh, even with the revalve. So i changed the emulator spring(the little one on the inner chamber) to the next softer one...that made a huge difference on the initial plushness. That is what i would recemend, go on the stiff side for fork spring and for woods go with a softer emulator spring. Even with the .48 i am using all but about a 1/2" of the travel in the woods...no jumps. I know your softer, but to me that gives all the more reason to play with the emulator spring rate.

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