WR Spring on a YZ


10 replies to this topic
  • torqueme

Posted December 10, 2006 - 11:18 PM

#1

Allright, i know sombody out there must have tried this, i've had it posted on the suspension forum for 2 days with no replies. what do you guys think?

I know this may sound crazy to some out there, but here goes...I have a '02 yz426f. i love the bike but i ride strictly trails, HS & mostly mud, rivers & mountains-tight trails. i just cannot get the suspension "trail friendly." i know the WR spring will fit & is lighter-but my question is will it work? is there a down side? all info / comments appreciated. aloha

  • 642MX

Posted December 11, 2006 - 06:27 AM

#2

Allright, i know sombody out there must have tried this, i've had it posted on the suspension forum for 2 days with no replies. what do you guys think?

I know this may sound crazy to some out there, but here goes...I have a '02 yz426f. i love the bike but i ride strictly trails, HS & mostly mud, rivers & mountains-tight trails. i just cannot get the suspension "trail friendly." i know the WR spring will fit & is lighter-but my question is will it work? is there a down side? all info / comments appreciated. aloha



I don't think a softer spring is what you need. A softer spring is just going to cause the rear end to drop in its stroke and its still going to be too harsh for trail riding. You would probably benefit from having a suspension shop revalve your forks and shock for woods riding. Its amazing what a good suspension shop can do. :thumbsup:

  • grayracer513

Posted December 11, 2006 - 10:07 AM

#3

Interesting that Race Tech's spring calculator calls for a 5.26 kg/mm spring on the YZ426 with a 180 pound (no gear) rider. The stock YZ426 spring is listed as a 5.4, and the WR426 spring is listed as a 5.2.

Understanding what a change in spring rate does is made a little difficult on modern bikes because the spring works at a huge disadvantage due to its position on the swing arm, and has to be a lot stiffer than if were in an old school mount back by the rear wheel. You have to consider what the effective spring rate would be. In the first place, the 5.2 kg/mm spring is roughly 290 lbs/in, and the 5.4 is about 301 lbs/in. Since they work at about a 3:1 leverage disadvantage, they equate to about 97 and 100 lbs/in at the rear wheel.

What those numbers mean is, to use the 100 pound spring rate as an example, is that it will take 100 pounds of load to compress the spring on inch. Because we can adjust the ride height (sag) as we like it, we can set either of these springs to the same height with the rider sitting on the bike. The difference then is what happens when the load changes. If you hit a bump that produces an impact force of 400 pounds, the stiffer spring would compress 4 more inches, while the weaker one would compress 4 1/8". (note that this is a very simplistic look at this, and it ignores a whole host of dynamic factors like inertia and damping, but it makes it easier to understand).

If you ride at less than a racing pace pretty much everywhere, and you can back off the compression damping all the way without bottoming out on the most severe impacts you generally take, then you probably can run softer springs. Either that, or your suspension damping was redone for someone much heavier and/or faster than you. But 642 is correct that it is possible to put too soft a spring on the bike too, and end up having to crank up the compression to the point that it always feels harsh in order to compensate. In those cases, a stiffer spring actually ends up giving a plusher ride.

But I don't think it sounds like you're in danger of doing that by going to a 5.2 in your case, and you can always decide you don't like it and switch it back.

  • tammie

Posted December 11, 2006 - 05:17 PM

#4

i did it, made a difference to me, the stock yz rear was stiff for me i was getting bounced around im only 140lbs, just swapped the rear spring for a stock WR one and softer race tech fork springs and ive loved my suspension ever since.

  • torqueme

Posted December 11, 2006 - 11:44 PM

#5

Thanks for all the input-Especially the #s in english gray. i swapped them tonight & i already like it better just on a test ride. will know more after this weekends ride. the springs are exactly the same length, but diameter of steel coil is smaller on the WR. this seems to give me more range of adjustment with dampening & rebound. the YZ spring/system worked great WFO-but i seldom get out of 3rd in the stuff i ride in. picked the brand new WR spring up on ebay for $5.00-so if i hate it nothing lost. again thanks & will post results -sun/mon.aloha

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  • grayracer513

Posted December 12, 2006 - 08:08 AM

#6

the springs are exactly the same length, but diameter of steel coil is smaller on the WR.

That's one of two ways the spring can be made to have a lower rate. The materials being otherwise the same, the "springiness" per mass of the steel used ends up being more or less the same for any spring. Given that, the rate of the finished spring is controlled in one or both of two ways.

It helps to understand that a coil spring is just a torsion bar wound into a cylindrical shape, and the wire absorbs the load placed on the spring by twisting. If you visualize a cross section of the spring as the coils compress, you can see that. With that, if you make the wire larger in diameter, or make the torsion bar shorter, it will be stiffer. Coil springs made to fit on a certain type of shock have to all have a certain free length, so the way that they are made "shorter", and thereby stiffer, is to reduce the number of coils in the spring.

Make sense?

  • torqueme

Posted December 12, 2006 - 10:44 AM

#7

Makes more sense than any other explanation i've heard...no wonder i hated physics. looking forward to this weekend & a true test. thanks...

  • torqueme

Posted December 18, 2006 - 12:01 AM

#8

Ok it's been trail tested HARD today & it works. thanks for the input from all. the softer rate of the wr spring gives me a wider range of compression & dampening adjustment using the stock yz shock. i played with it all day & finally found my comfort zone. amazing difference, the shock is actually allowed to work with the lighter spring on trails. harshness pretty much a thing of the past. highly recomended as an economical remedy for yz in the woods.:thumbsup:

  • jayh300

Posted December 18, 2006 - 07:08 AM

#9

sweet..... btw how are trails in hawaii ??????????
not that i would ever get a chance to ride there.

  • torqueme

Posted December 18, 2006 - 10:42 AM

#10

sweet..... btw how are trails in hawaii ??????????
not that i would ever get a chance to ride there.

Closest to the mainland geography i can compare would be the georgia mountains. we have what we call "red dirt" here, fine clay that rides like glass or glue, depending on how much rain there has been. not to mention the volcanic mountains/rocks. makes for good fun!! i've got a couple of spares in the garage if you ever cross the pond...aloha.

  • bboyce

Posted December 18, 2006 - 01:55 PM

#11

i did it, made a difference to me, the stock yz rear was stiff for me i was getting bounced around im only 140lbs, just swapped the rear spring for a stock WR one and softer race tech fork springs and ive loved my suspension ever since.


How come im 137, and my 06 seems to just blow through the stroke? My sag is a little low, at around 90, but it seems to handle fine. All the magazines say that the fork is underspring, but the shock is perfect. How come it seems the other way around for me? My fork seems to be perfect, and the shock bottoms easily. I am currently running 6 clicks out on compression, stock rebound and stock HS damping.

Sorry this is off topic, just had to ask while were on the topic, and your around my weight.





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