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Weight of bike to be included in fork spring rate?


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My bike weighs 280lbs wet.  I have a lot of add-ons such as skid plate, radiator guards, steering damper, etc...which is included in the 280lbs.  I weigh 200lbs with my gear on.  My current spring rate is 5.2n/mm.  I like to catch big air and the landings are often fairly flat.  I want to stiffen up the forks.  What spring rate should I have?

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Knowing which make, model, and year of motorcycle plus type of terrain (tight woods, trails,

sand pit, MX track, etc) would be very helpful in getting constructive opinions to your question.

2014 Husaberg 501FE 510cc, medium size jumps with semi flat landings, cliff drops onto steep landings, hill climbing at high speeds (tapped out in 2nd - 3rd gear).  Helpful I hope.

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What was the weight of the bike including fuel, before those accessories.

We'll have to convert that n/mm unit of mesure into more common kg/mm.

 

The Race Tech spring rate calculator doesn't list the 2014 model year 501FE, only up to 2000

What are the stock fork / shock springs specs? The manual looks available online but long to download.

Edited by mlatour
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How many threads do we need discussing this bike/setup?

 

Racetech says 5.1 N/mm for a 200 pound rider on a KTM 500 XC-W, which should be very close to your bike.  Based on this it sounds like 5.2 N/mm is the right ballpark.

 

What does your sag measure?

 

Spring rates, especially in the fork, are not an exact science; you pick the recommended rate and go from there.

 

To answer the thread title, yes, the bike weight is definitely included when determining the fork spring rate

 

If you think your springs are too soft, try stiffer ones and see how they work.  Worst case is you don't like them and you go back to the 5.2 N/mm.

 

You paid a tuner to set this bike up, discuss this with him!

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5.1 or 5.2, 0mm preload should be fine for you. Rear 80 something is my guess. If it is 77,78, 80 is impossible to say. You need to ride it to determen that.

 

Im almost 200lbs and with my 450 SXF 2014 i run 5.1 in front (revalved). Rear is not comparable since you have no linkage.

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Stiffen up for what part, bottoming, riding to low in front? Quick fix to stiffen is increase oil for more bottom end resistance. It will affect ride height also of course. Another solution is to increase preload 1-3mm.

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Lot's of people say to increase the oil height and you are not wrong.  However, it didn't make a huge difference.  I was able to notice once adding 30cc, and per my tuner I needed to stop at 60cc...so I stopped at 60cc.  Per all of you the spring rate is correct, but it wouldn't hurt to bump it up a bit to feel things out.  I am going to open two more threads.  One to discuss the fact that my rebound is maxed out and I want the option to feel a slower rebound and not just faster.  Second thread to discuss dropping the sag to 120mm in hopes that might create a smoother ride, not compromise bottoming resistance, and keep my rear from bouncing left to right in high speed whoops. 

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