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Is Race Tech spring rate search close?

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Im setting up a YZ250 for woods riding for my boy and I am curious if the race tech spring rate search is close to the correct spring rates or not??

 

The bike is a 99 YZ250, My boy weighs 160lbs with out riding gear. I would say he is B rider as he is a lot faster than all of his buddy's.

 

According to Race Tech being a B rider, using trail / enduro, Class B, standard height & gas tank and being 160lbs with out gear he should be using .417 fork springs and 5.096 shock spring.

 

I then checked it using a C rider and it said to use  .403 fork springs and 5.044 shock spring which are pretty close to each other.

 

Any input would be much appreciated.

 

http://racetech.com/VehicleSearch

 

 

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I use their calculator all the time. You can see a small difference, because the springs are mostly there to hold up bike and rider weight. They are not very terrain or skill influenced.

Can you get the sag on the shock correct as-is? What fork springs do you have in there now?

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When I got my springs a few years ago, I noticed their calculator recommended too stiff for the forks and too soft for the shock (or vice versa :excuseme:), but they must have corrected it.  I just checked and the they're pretty close (less than 1 rate off for each) to what I have and know works for me.

Edited by bg10459

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Im setting up a YZ250 for woods riding for my boy and I am curious if the race tech spring rate search is close to the correct spring rates or not??

 

The bike is a 99 YZ250, My boy weighs 160lbs with out riding gear. I would say he is B rider as he is a lot faster than all of his buddy's.

 

According to Race Tech being a B rider, using trail / enduro, Class B, standard height & gas tank and being 160lbs with out gear he should be using .417 fork springs and 5.096 shock spring.

 

I then checked it using a C rider and it said to use  .403 fork springs and 5.044 shock spring which are pretty close to each other.

 

Any input would be much appreciated.

 

http://racetech.com/VehicleSearch

 

The calculator can give you a balpark estimate, but for the shock spring the actual sag tells the whole truth.

 

At 160 lbs I imagine the stock springs should be either perfect or slightly stiff. Do you know what springs are in there now? what are you current sag numbers?

 

If you know your current spring rate and sag you can estimate the new spring rate to achieve the target sag.

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I will see what the Sag is when he gets home from school today. In the mean time I will see if I can figure out what spring is installed on the rear. I know it has the stock fork springs in it as we replaced the fork fluid when we bought it last fall.

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I think the calculator is right on for mx. However for off road it can be a little light. Pretty hard to account for all the weight that could be added to the bike in the form of pipe guards/skid plates, trail equipment, steering damper, spare parts, water packs, and etc. Etc. Etc.

So for mx it's good. But for off road you may need to guestimate the weight of extra stuff on the bike and add that to the rider weight in street clothes to get a real close calculation for spring rates. I find if I don't add a bunch of off road weight the calculator comes up 1-2 springs light.

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I will see what the Sag is when he gets home from school today. In the mean time I will see if I can figure out what spring is installed on the rear. I know it has the stock fork springs in it as we replaced the fork fluid when we bought it last fall.

As far as I know there is no way to tell if the spring in the forks are stock by looking at them. I have a set of OEM .43 and a set of  OEM .41 and they look identical in every way. There are no markings that I can find. I always wondered why Yamaha didn't label them like FC does.

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As far as I know there is no way to tell if the spring in the forks are stock by looking at them. I have a set of OEM .43 and a set of  OEM .41 and they look identical in every way. There are no markings that I can find. I always wondered why Yamaha didn't label them like FC does.

I think you are correct. So who knows. Is there a way to check what the rear shock spring is??? I thought the previous owner had it written down in the service manual but it was not. It must have been a different bike.

 

Here is what we got with him in street close with 7lbs added for back pack.

 

Bike on stand.....    ..........    ............ ...    Front 654mm   Rear 593mm

 

Bike free standing on its own wieght...    Front 625mm   Rear 576mm

 

With him on it and 7lbs added ...........     Front 593mm   Rear 492mm

 

Just from looking at these numbers I know the springs are out to lunch for him on it. Im planning on getting it re-valved but I first need to get the springs close.

Edited by Zrt1200

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Their calculator was way too stiff on my fork springs. I ended up putting one stock spring back in to split the difference.

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I think you are correct. So who knows. Is there a way to check what the rear shock spring is??? I thought the previous owner had it written down in the service manual but it was not. It must have been a different bike.

Here is what we got with him in street close with 7lbs added for back pack.

Bike on stand..... .......... ............ ... Front 654mm Rear 593mm

Bike free standing on its own wieght... Front 625mm Rear 576mm

With him on it and 7lbs added ........... Front 593mm Rear 492mm

Just from looking at these numbers I know the springs are out to lunch for him on it. Im planning on getting it re-valved but I first need to get the springs close.

so it looks like the shock spring may be a bit light for him. your current numbers show a rider sag of 100 and static sag of only 17. you can probably drop the rider sag to as much as 110 and see how much the static drops but my guess is it will not drop enough. I think you want go get that static up in the 30-35 range while maintaining 105-110 rider sag. But these numbers are for my 2011. not sure about the 99.

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I think you are correct. So who knows. Is there a way to check what the rear shock spring is??? I thought the previous owner had it written down in the service manual but it was not. It must have been a different bike.

 

Here is what we got with him in street close with 7lbs added for back pack.

 

Bike on stand.....    ..........    ............ ...    Front 654mm   Rear 593mm

 

Bike free standing on its own wieght...    Front 625mm   Rear 576mm

 

With him on it and 7lbs added ...........     Front 593mm   Rear 492mm

 

Just from looking at these numbers I know the springs are out to lunch for him on it. Im planning on getting it re-valved but I first need to get the springs close.

Your rear spring is close. You've got 101mm in race sag, and 17mm in Static sag. Which means your close, but the spring is slightly to light.

 

The stock shock springs will typically have a color code on them. A small dot of paint, that when you search in the manual will tell you the spring rate.

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There is a huge difference between RaceTech's philosophy for offroad and other tuners, like Factory Connection and some others. RT emphasizes a very soft ride in the woods. It is really plush compared to FC. But if you need more spring, you are out of luck. RT tunes for 95% woods riding.

 

Example?

 

I'm 175 without gear and RT recommended a 0.86 kg spring for my KXF250, while FC recommended 0.97. I was running a 0.87, which was really plush, but take a big jump and not so much fun. It's just a difference in philosophy. Both will work.

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Very good info guys, I will set rider sag at 110mm and see what I get for static sag. Im curious if the front being stiff will change the back though?? Also, Would the clicker setting make any diferance doing this as I have no clue to where they are set at.

Edited by Zrt1200

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Looking at getting a 2017 YZ250, possibly a new left over 2016 and upgrading the brakes.  Anyway.....I looked at RaceTech and MX-Tech and they aren't even close.  According to RaceTech for a 42 y/o MX'r in B-class at 185-190lb my fork spring rate should be 0.46kg/mm and my shock spring should be 5.6 kg/mm.  According to MX-Tech I can basically use the stock springs (0.43 kg/mm for the fork), possibly increase the shock spring from 4.8kg/mm to 4.9kg/mm.

 

Looks like RaceTech is calculating way too stiff or MX-Tech way too soft??  According the the MX-Tech info a 5.6kg/mm shock spring is for a 260lb rider and the spring rate is in the 230lb area.......so what gives???  Looks like I'll do it the old fashion way and get on the bike and measure.....

Edited by mattcrna10

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I'm 185–190 without gear and run .48 up front and a 5.6 in the rear. Perfect for me. It's hard to believe but the stiffer the springs the softer the ride.

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The spring calculator is good, but the springs themselves can vary by 10% in rate (which I found out by having them tested).  Apparently that is an accepted margin of error.  

 

If you don't mind a suggestion, Phil at SOPRO in Chattanooga, TN will sell you springs with verified spring rates for about the same price as what you get anywhere else. He does great work on YZs too!

http://sopro.bz/

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I'm 185–190 without gear and run .48 up front and a 5.6 in the rear. Perfect for me. It's hard to believe but the stiffer the springs the softer the ride.

Do you ride MX or woods with those springs?

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I'm 185–190 without gear and run .48 up front and a 5.6 in the rear. Perfect for me. It's hard to believe but the stiffer the springs the softer the ride.

 

I am 195 wo gear and also running a 5.6 in the rear and the sag is perfect. A friend of mine tried my bike yesterday and thought it was way too stiff, but to me it seems perfect. I think there is a lot of variation in personal preference. As you mention, some tuners (FC for one) argue that stiffer springs with softer valving = plusher ride. I have always heard that getting the sag right is the only purpose of the spring, but I still may try a lighter one based on the feedback I got.

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Do you ride MX or woods with those springs?

Mostly woods, but I don't think it matters. Springs are for your weight, valving is for your terrain.

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