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Author Topic: YZ250 Spring Rates  (Read 20690 times)

6IX

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YZ250 Spring Rates
« on: May 16, 2012, 11:02:54 AM »

There seems to be some conflicting information out there regarding late model YZ250 spring rates.  Race Tech lists the stock spring rates as .44 and 4.7 for 2009 – 2012 YZ250’s

http://racetech.com/ProductSearch/1/Yamaha/YZ250/2012

http://racetech.com/ProductSearch/1/Yamaha/YZ250/2011

http://racetech.com/ProductSearch/1/Yamaha/YZ250/2010

http://racetech.com/ProductSearch/1/Yamaha/YZ250/2009


The forks seem like a no brainer since RaceTech (.44) and my 2010 owners manual (.438) seem to agree.  I plan to go with a .45 spring which Factory Connection offers, or the .449 or .459 that the owner’s manual lists as the next 2 stiffer fork springs available from Yamaha.  Race Tech and Eibach fork springs are only available in .44 and .46 for the YZ250.


So the real question is what rate shock spring to go with taking into consideration that I probably won’t be dropping $650 for a new titanium spring. I’ve heard that you should drop down 1 rate when going from steel to titanium, and therein lies the dillema...

http://motocrossactionmag.com/Reviews/News/MXA-TEAM-TESTED-DSP-TITANIUM-SHOCK-SPRING--3220.aspx

The 2010 owner’s manual states that the stock titanium spring is a 4.9 (conflicting with RaceTech’s data of 4.7), and goes on to list equal pitch steel springs of  4.3, 5.3, 5.5, and 5.7 as replacement options for the titanium spring.  MXA also states that the 2010 rear spring rate is a 4.9, and recommends going to a 5.0 if you are a heavier / faster rider. What’s odd is that MXA states that the rear spring on the 2011 – 2012 bikes is a 4.7, even though there were no changes made through those years (unless you count the engine’s slightly lower compression and larger silencer).

.43 and 4.9
http://motocrossactionmag.com/Main/News/REAL-TESTS-2010-MXA-RACE-TEST-OF-THE-2010-YAMAHA-Y-7122.aspx

.43 and 4.7
http://motocrossactionmag.com/Main/News/2011-YAMAHA-YZ250-MOTOCROSS-TEST-THE-BIKE-WED-ALL-7809.aspx

.43 and 4.7
http://motocrossactionmag.com/Main/News/MXAS-2012-YAMAHA-YZ250-MOTOCROSS-TEST-NOT-EVERYONE-8839.aspx



SO, do I go with a 5.0 steel spring and hope that it’s slightly stiffer than the 4.9 (or is it 4.7 ??) titanium spring, or will it end up being about the same, and I really need to go with a 5.2 – 5.3 steel spring to notice any difference?

Any experience / advice is appreciated.  Thanks.
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flipside

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Re: YZ250 Spring Rates
« Reply #1 on: May 16, 2012, 11:05:29 AM »

Loose some weight... :lol:

Have the stock one tested. Ship it to me or give it to Shifty next he heads down there.

I can get you a way better price on the Ti or Steel spring.
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batotal

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Re: YZ250 Spring Rates
« Reply #2 on: May 16, 2012, 12:33:21 PM »

How much do you weigh? The difference between a 4.9 and 5 is slight. In my opinion not worth trading Ti for steel.

You really have to test the springs to have a proper reference point. There's a lot of variation in springs, as well as inaccuracies in what the manual says vs whats actually on the bike stock.

Without testing you have to trust both what the manual says is accurate and what the new spring rating actually is. Again there's variation. Either or both could be wrong.

It's a crap shoot.
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Hack-Man162

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Re: YZ250 Spring Rates
« Reply #3 on: May 16, 2012, 12:37:56 PM »

Why are you looking at any springs other than genuine KYB?  Actually, I've used a Diverse before on the shock and it was good stuff.  They test every spring for rate, as should any good seller.  Stay away from Eibach....my experience has been that they are junk.
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6IX

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Re: YZ250 Spring Rates
« Reply #4 on: May 16, 2012, 12:48:29 PM »

I weight ~185 without gear.   MXA noted the following regarding the DSP titanium spring they tested:

Quote from: MXA
You can’t trust the spring rate written on most titanium shock springs. In many cases, a 5.4 will test out as a 5.2. The good news is that when we tested the 5.3 Honda CRF450 spring from DSP, it tested as a 5.3 (it was confusing that the spring had 5.4 printed on it, but DSP tests every spring and hand writes the actual rate on it in pen).

If I went with a 5.0 or 5.1 titanium spring I’d be pretty confident that I’d get what I was after (slightly more control for my weight), but if I went with a steel spring I’m not confident on what rate to choose, and would hate it if it ended up being too harsh.  :?
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Hack-Man162

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Re: YZ250 Spring Rates
« Reply #5 on: May 16, 2012, 01:52:23 PM »

6iX, what's your static sag now when you dial the spring in for race sag?
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Shamus

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Re: YZ250 Spring Rates
« Reply #6 on: May 16, 2012, 02:16:55 PM »

Why are you looking at any springs other than genuine KYB?  Actually, I've used a Diverse before on the shock and it was good stuff.  They test every spring for rate, as should any good seller.  Stay away from Eibach....my experience has been that they are junk.

Eibach makes the RaceTech springs.
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batotal

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Re: YZ250 Spring Rates
« Reply #7 on: May 16, 2012, 04:25:15 PM »

I weight ~185 without gear.   MXA noted the following regarding the DSP titanium spring they tested:

Quote from: MXA
You can’t trust the spring rate written on most titanium shock springs. In many cases, a 5.4 will test out as a 5.2. The good news is that when we tested the 5.3 Honda CRF450 spring from DSP, it tested as a 5.3 (it was confusing that the spring had 5.4 printed on it, but DSP tests every spring and hand writes the actual rate on it in pen).

If I went with a 5.0 or 5.1 titanium spring I’d be pretty confident that I’d get what I was after (slightly more control for my weight), but if I went with a steel spring I’m not confident on what rate to choose, and would hate it if it ended up being too harsh.  :?

Doesn't matter if it's steel or Ti, what matters is the actual rate.

You really don't want to spend the money for Ti unless you're sure of the rate, which means it has to be tested. At your weight a 5 or 5.1 should be fine regardless of whether it's steel ot Ti. Even the 4.9 (if it is 4.9) should be close to being in the ballpark.

The question is: What's the sag and how much preload do you have on your stock 4.9 Ti spring? If it's only preloaded say 10mm, you can easily go another couple turns to 13mm and still be well within the minimum range. If you're already preloaded to the minimum (approx 15mm) then a stiffer spring will probably give you the "control" you seek. But don't forget "control" can be adjusted with damping...




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nickvalve

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Re: YZ250 Spring Rates
« Reply #8 on: May 16, 2012, 04:51:26 PM »

Spring rates are spring rates . What really is different about Titanium springs is that Titanium has a faster frequency response than steel , can you actually feel it , yes I can. What does it mean in laymans terms ? It comes into play at the point of direction change or in terms of a track , when you have poor traction conditions [ say off cambers with chop ] the rear wheel is able to track the ground surface with more confidence . Many cannot tell the difference in the real world . As far as being lighter than steel , in truth , the latest KYB springs are wound so as to be not much different in actual weight [ all things being equal of course ie: rate ] there is perhaps a one to two pound difference between the late KYB's and their Ti counterparts. There were some reports of the early KYB Ti springs breaking , I have never seen one. Springs are difficult to manufacture and without them costing way too much , most spring manufacturers just give a plus or minus of one full rate , so a 5.2 spring could be within spec if its 5.1 to 5.3 . I will rate your spring for you and give you a recommendation if you want to bring it in here. As mentioned above a single rate spring change 5.2 to 5.3 for example is kinda fruitless . Any bike equiped with a top out spring top out system can seem to have good free sag , but not be correct. Yes , I have seen a couple Race Tech specs that I didn't agree with , that is why I rate every single spring that comes through here / both forks and shock. Nick shut up , blah blah blah.
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Bruce372

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Re: YZ250 Spring Rates
« Reply #9 on: May 16, 2012, 05:25:48 PM »

i've never trusted the race tech specs, they always seem to be a little on the soft side.

i dont think its worth going from a 0.44 to a 0.45 or a 5.0 to a 5.1, very little difference.
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batotal

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Re: YZ250 Spring Rates
« Reply #10 on: May 16, 2012, 05:33:41 PM »

Spring rates are spring rates . What really is different about Titanium springs is that Titanium has a faster frequency response than steel , can you actually feel it , yes I can. What does it mean in laymans terms ? It comes into play at the point of direction change or in terms of a track , when you have poor traction conditions [ say off cambers with chop ] the rear wheel is able to track the ground surface with more confidence . Many cannot tell the difference in the real world . As far as being lighter than steel , in truth , the latest KYB springs are wound so as to be not much different in actual weight [ all things being equal of course ie: rate ] there is perhaps a one to two pound difference between the late KYB's and their Ti counterparts. There were some reports of the early KYB Ti springs breaking , I have never seen one. Springs are difficult to manufacture and without them costing way too much , most spring manufacturers just give a plus or minus of one full rate , so a 5.2 spring could be within spec if its 5.1 to 5.3 . I will rate your spring for you and give you a recommendation if you want to bring it in here. As mentioned above a single rate spring change 5.2 to 5.3 for example is kinda fruitless . Any bike equiped with a top out spring top out system can seem to have good free sag , but not be correct. Yes , I have seen a couple Race Tech specs that I didn't agree with , that is why I rate every single spring that comes through here / both forks and shock. Nick shut up , blah blah blah.

I agree. I can feel the difference between Ti and steel as well. Not only the frequency but the installed weight effect. That's why I would try and keep the Ti spring if at all possible. If I were 185 lbs I would do everything I could to keep the Ti spring in this case.
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Hack-Man162

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Re: YZ250 Spring Rates
« Reply #11 on: May 16, 2012, 05:40:20 PM »

I've got a 4.9 stock titanium spring if anyone is interested.  Offers that involve Stone Brewing Company beverages are always welcome!
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6IX

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Re: YZ250 Spring Rates
« Reply #12 on: May 17, 2012, 09:20:24 AM »

6iX, what's your static sag now when you dial the spring in for race sag?

I’d have to check, but shouldn’t it be around 15mm at the bare minimum?  I've heard that the stock Ti spring is progressive (whatever that really means. :? ) and requires more pre load than a steel spring at the same rate and free sag numbers will be less.  Generally, I'd say the bike drops very little when I pull up on the rear fender and then let it go.

Is it important to actually measure the preload?  :?  I've always just set the sag where it should be with however many turns of the spring it takes, but I've been reading about people having actual preload measurements in mm.  :?


What really is different about Titanium springs is that Titanium has a faster frequency response than steel , can you actually feel it , yes I can. What does it mean in laymans terms ? It comes into play at the point of direction change or in terms of a track , when you have poor traction conditions [ say off cambers with chop ] the rear wheel is able to track the ground surface with more confidence .

Related to the comment that a Ti spring is more progressive, my guess is that the Ti spring will feel a little more sensitive & supple initially, and feel a bit more lively than a steel spring. Maybe this relates to your comment, maybe not.

You're with ProValve, right?  Where are you located?
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6IX

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Re: YZ250 Spring Rates
« Reply #13 on: May 17, 2012, 09:23:27 AM »

i dont think its worth going from a 0.44 to a 0.45 or a 5.0 to a 5.1, very little difference.

Thanks for the advice.  I am looking for a very subtle difference though.   I just dont think the YZ250 is sprung for a guy who weighs 185lbs in his street clothes and likes to jump.  :(
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Bruce372

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Re: YZ250 Spring Rates
« Reply #14 on: May 17, 2012, 09:26:48 AM »

i dont think its worth going from a 0.44 to a 0.45 or a 5.0 to a 5.1, very little difference.

Thanks for the advice.  I am looking for a very subtle difference though.   I just dont think the YZ250 is sprung for a guy who weighs 185lbs in his street clothes and likes to jump.  :(

Problem is, you might buy a 5.1 and get  a 5.0 and end up no different!
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