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Race Tech spring calculator...accurate?

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I tried entering my data (mx, 40yo, beginner, 240lbs) into the race tech spring calculator, and I am a bit baffled by its recommendation...

I have a totally stock 2016 YZ250F with standard springs:

  • Fork: 4.6 N/mm
  • Shock: 54 N/mm

and the calculator recommended:

  • Fork: 4.52 N/mm
  • Shock: 62.76 N/mm

I totally get the beefier shock spring, but I had not anticipated a softer fork spring.

So, the question is: how accurate is the race tech calculator? Does this make sense to you guys?

 

Thank you in advance :)

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Too soft on fork imo

Q springs have one I think

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Sounds much closer I have used 4.5 fork springs and I weigh 145 , the lowest fork spring I can run is 4.2

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The primary purpose of the fork spring is to get proper sag or ride height.  A lighter rate fork spring will give you more sag, a lower ride height.  Fork springs also contribute to fork compression resistance and work with fork oil level to prevent bottoming.  The fork spring and the air gap are what resist fork compression and damping is what slows the action down for more control but also to keep the fork working in the upper part of the stroke.

Why does RaceTech suggest softer fork spring rates for less experienced riders and older riders?  It has been my experience that spring rate doesn't change the plushness and without an adequate fork oil level, air gap too big, the fork will bottom effortlessly so clearly fork spring rate is a compromise to attain the desired sag above all else.  Fork oil level will dial in bottoming control and damping is to prevent excess motion but never resist enough to feel harsh.  It's important to use each one of these to tune the particular aspect of fork behavior and not compromise one to fix an issue for another one.  Like changing fork spring rate or damping to prevent bottoming, that is the job of fork oil level.

Sorry for the rant, just trying to get a better grasp on this suspension concept.  Quite frequently I see discussions on trying to correct a fork performance issue by changing the wrong department.  This gets confusing for new folks not to mention will not provide a successful result. 

 

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I love the rant! Give a man a fish vs. learn a man how to fish and all that :)

So if I understand correctly weight, above anything else, determines how to spring a bike. And I should therefore go for a heavier fork spring to match the much heavier shock spring.

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22 minutes ago, BoMadsen said:

I love the rant! Give a man a fish vs. learn a man how to fish and all that :)

So if I understand correctly weight, above anything else, determines how to spring a bike. And I should therefore go for a heavier fork spring to match the much heavier shock spring.

There is definitely a balance between front and rear which needs to be made or kept. 

RaceTech takes lots more into consideration than just rider weight.  Type of riding, Age, Skill Level all suggest the speeds the bike will be going, faster can use more spring rate.  A 25yo Pro Flat track rider is going the fastest and over the smoothest surfaces.

More sag is advantageous for slower more technical riding as it changes the rake angle of the forks and effects the "trail" value.  The front end will turn more easily and precisely, feels much better, less work but gives up some higher speed stability more typical on an MX track.  Not sure if this is why RaceTech suggests less fork spring rate for Trail/Enduro.  Desert is fast but over softer terrain except for the rocks many riders encounter.  Not sure why Desert is on the softer spring rate side.

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I think rt is just wrong on lots of it's fork recommendation, not always too soft or too stiff , just a bit all over the place

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2 hours ago, mog said:

I think rt is just wrong on lots of it's fork recommendation, not always too soft or too stiff , just a bit all over the place

This! I have gotten several different rate suggestions over the years on the same bike and exact same info. I do not understand RT not using rider weight "geared up" as opposed to without. Doesn't make sense to me.

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My opinion is that "if" they have imputed the stock rates correctly(many times I've found the stock rates to be incorrect) and you don't change the modifiers, the rates will be somewhat close. As soon as you start changing the modifiers from the standard settings they get all over the place.

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18 hours ago, homo erectus said:

My opinion is that "if" they have imputed the stock rates correctly(many times I've found the stock rates to be incorrect) and you don't change the modifiers, the rates will be somewhat close. As soon as you start changing the modifiers from the standard settings they get all over the place.

What "modifiers" are you talking about?

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In general beginners and vet do not charge the front end as much as a young pro and same between moto and trail riding that's why RT takes it in consideration. The rider weight is one thing but where will be the center of gravity depending of height, riding style,...is one more. 

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hi all

now i have noticed my springs are wrong.

i can't remember why they are so, maybe because i misunderstood something, or someone advised wrongly

average rider ,165lbs + -,enduro riding,45 yo, standard height, 3.0 gallon tank, cr250 2007 bike, showa forks + shock

front forks springs: 4.2kg each

shock springs: 5.0 kg

according to racetech ,the shock spring is too hard. i  should go 4.8 kg.  Is it a big issue? or can i solve easily by having more static sag? do i run unbalanced?

 

thanks

Edited by frenando

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16 hours ago, YHGEORGE said:

What "modifiers" are you talking about?

^^^What KDX said. Seems every one you alter changes the fork rate by 1 size. If you say you're a C class rider it drops 1 and if you are also 33yrs old instead of 27yrs old it drops you 1 more.

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I use the same exact info each time yet the spring suggested changes occasionally. I know myself and my bike pretty well now.

Edited by YHGEORGE

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Usually 38, haven't checked in a couple months, but that is normal with the 5.3 at 102-103 rider.

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