# how to calculate a motorcycle spring rate for your weight?

## Recommended Posts

Curious to know how you choose the right spring for your weight on a bike, how do you find this out?

I assume you take the amount a shock travels and compare it to the spring rate versus your weight?

Do you compensate for the amount of force off of a jump?

Not to sure how this is done as you can probably already tell,

thanks for the information.

##### Share on other sites

Go to race tech http://racetech.com/ChooseVehicle.aspx. They have a spring rate calculator

You cannot really do the math just based on your weight and shock travel. Spring rates are also impacted by the weight of the bike (heavier bike = stiffer springs).

##### Share on other sites

The calculators are wrong, trust me I have 4 spare rear shock springs for my bike by using the calculators, be carefull.......

• 1

##### Share on other sites
Curious to know how you choose the right spring for your weight on a bike, how do you find this out?

I assume you take the amount a shock travels and compare it to the spring rate versus your weight?

Do you compensate for the amount of force off of a jump?

Not to sure how this is done as you can probably already tell,

thanks for the information.

are you on a 2 stroke? what is your weight?for me, the spring calculators are not even remotely in the ball park for correct rates.

i,m heavy and riding a 2 storke.all the calculators had way to heavy fork springs and way to light shock springs.

the rate quoted for me on the shock was between 5.6 and 5.8.i tried a 5.8, not even close.i now run a 6.7.perfect sag with 5mm spring preload and a great ride,soft yet firm and i use full travel on every ride.

forks were quoted at .52,i tried .50,ya right .i would only use half the travel,they were like riding on concrete.now i run .46.i get great dive for turn in,good sag,and i rarely bottom.most rides i use all but 1 to 1 1/2 inches of travel.

##### Share on other sites

i noticed this as well, i think they are using a maths formula, but for some reason the forks dont follow it properly.Very few people seem to need to go above 0.50 yet std is often 0.47, and on the rear they seem to start too hard for lighter riders, and yet are too soft for heavier....weird..

##### Share on other sites
That link does not go to the calculator, and I combed the site trying to find it with no luck. Google search results for the race tech spring rate calculator show thumper talk links and none to racetech...

what gives?

You have to go in like you are looking for springs for your bike. It will ask you for your make, model, year. Then at the top of the page there is a link for the spring rate calculator. The calculators worked for me and many others. I just changed the rear spring in my bike based on this calculator and I was able to set the sag right. If you can set the sag right within spec (search TT there are many threads on sag) then you have the right springs.

##### Share on other sites

I'm on a two stroke, bike is in the sig.

I weigh 195 pounds and I'm 6' tall.

##### Share on other sites

you mx or bush rider?calgary area?i have some shock springs that you could test with in calgary

##### Share on other sites

I am 100 kg's excluding riding gear, Mx-tech said i needed a 5.4kg rear, I am on a 6.0kg and my sag figures are 103mm rider, and 33mm static......

All I need to do now is figure out what to do with the 5.4,5.6,5.7 and 5.8kg spare springs I have

And what fork springs to match them too........4.7kg maybe?????

##### Share on other sites

Ah but stu the sag numbers you were getting on any of those springs would have helped you goto the correct one ?

##### Share on other sites

Nah, Instead of just trusting my calculations and y gut feel, I was fresh into suspension and listened to the many 'Experts' around where I live, turns out I learned about sag the hard way!!!

Our top guy here still tells m that the 6.0kg is way to stiff for enduro riding, and I should have the 5.7 or 5.8 in at most, what confuses me is that my figures are right...?

Mog what are your thoughts? And what should I use in front? Would 4.7's do the job?

##### Share on other sites

well i agree with the rest stu to be honest, i would run 5.8 rear and would run 0.45 fronts.

whats your proocedure for doing your sag. your numbers are good so theres something a miss here. also have you had the spring checked? did you get all your springs from the same place?

i test a lot of springs and they can be a way off what the rate thats stamped on there.

##### Share on other sites

what fork springs have you tried so far? i would think 0.47 would be stiff enough

##### Share on other sites
I am 100 kg's excluding riding gear, Mx-tech said i needed a 5.4kg rear, I am on a 6.0kg and my sag figures are 103mm rider, and 33mm static......

All I need to do now is figure out what to do with the 5.4,5.6,5.7 and 5.8kg spare springs I have

And what fork springs to match them too........4.7kg maybe?????

Maybe you can put them on your feet and make springy shoes, or better yet make a really cool pogo stick.