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Fork springs - can you swap with another person?

  1. #1
    Lifer Ductard's Avatar
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    Fork springs - can you swap with another person?

    I have a 2004 GSX-R 600 that I think was set up for a 180 lb. rider. I'm ~205 and the forks are pretty close to bottoming out.

    I also have a 2002 KTM 520 SX that was set up for whatever Tricky Mike weighs - if I recall was also ~180 lbs. Those aren't bottoming out, but I'm betting that if they are traveling more than they should it's probably hurting performance at least a little.


    Let's say I could find someone that needed softer springs, could I just swap with them?

    Wondering if springs are one of those things you only use once (like crush washers) or with one set of components (like a chain & sprocket, or brake rotor and pads).

    And if there is some reason why it would be a bad idea to use used springs (other than not *really* knowing how much they had been used) - is it a "best practice" or really important not to violate.

    And if it would be ok to swap....how specific are springs as far as compatibility?
    Are fork springs super generic, or do they only fit specific makes / models, or are they more specific than that (i.e. I have non-stock internals)?


    And finally...does anybody have any fork springs they want to trade?

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    Last edited by Ductard; 09-14-14 at 11:04 PM.
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  2. #2
    Lifer jasnmar's Avatar
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    Re: Fork springs - can you swap with another person?

    Technically springs wear out.

    My service manual lists service limits for free length of the fork springs. If the free length is less than this stated length it's time for replacement.

    I haven't ever taken a set of factory springs out and not replaced them with aftermarket springs, so I can't actually give you any input on what the "wear rate" is for them as I never cared to measure them...

    That said, there's no reason to treat them as "single use" items. If I were rebuilding my forks to change valving or to replace a fork seal I wouldn't replace the springs just because. There's no problem in reusing them as long as they are within the service limit.

    They are not generic. They are not quite model specific. They are "sometimes" swappable across models / makes, but it all depends. For example the Racetech's that I put in aren't the same "free length" as the stock springs I took out (they aren't the same rate either), which meant cutting new spacers. Also, not all fork tubes are the same size, hence different diameter springs, so it really really depends.

    New springs from Race tech generally run ~$100 per set.

    The answer is it's complicated...

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  3. #3
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    Re: Fork springs - can you swap with another person?

    Quote Originally Posted by jasnmar View Post
    Technically springs wear out.

    My service manual lists service limits for free length of the fork springs. If the free length is less than this stated length it's time for replacement.

    I haven't ever taken a set of factory springs out and not replaced them with aftermarket springs, so I can't actually give you any input on what the "wear rate" is for them as I never cared to measure them...

    That said, there's no reason to treat them as "single use" items. If I were rebuilding my forks to change valving or to replace a fork seal I wouldn't replace the springs just because. There's no problem in reusing them as long as they are within the service limit.

    They are not generic. They are not quite model specific. They are "sometimes" swappable across models / makes, but it all depends. For example the Racetech's that I put in aren't the same "free length" as the stock springs I took out (they aren't the same rate either), which meant cutting new spacers. Also, not all fork tubes are the same size, hence different diameter springs, so it really really depends.

    New springs from Race tech generally run ~$100 per set.

    The answer is it's complicated...
    I'm gonna call your bluff, regarding that springs wear out... Though they might weaken slightly, depending on amount of preload and usage, you can certainly have them measured to see what their actual spring rates are at any given time. You can go to racetech.com and click on their "Spring Rate Search" to put in a particular bike and see what the OEM spring rates are. Also have the ability to input your rider weight & ability for a particular type of terrain to get recommended spring rates (take those numbers with a grain of salt). You can see dimensions O.D, Length & spring rate to determine if someone else has the springs that would work for you. You can also use two different spring rates in each fork to "fine tune" with what springs you have available. For example, 0.85 kg/mm & 0.95kg/mm springs could be used to have the equivalent of a set of 0.90kg/mm fork springs. If you know what you are looking for, there are some great deals for used fork & shock springs on ebay.

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  4. #4
    TRACK RAT!!!!! Pigman's Avatar
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    Re: Fork springs - can you swap with another person?

    I have a set of .95's out of 06 GSXR 600 forks...don't know if thats what you are looking for..

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  5. #5
    Lifer Kurlon's Avatar
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    Re: Fork springs - can you swap with another person?

    Quote Originally Posted by wheelieman14 View Post
    I'm gonna call your bluff, regarding that springs wear out...
    Springs absolutely can and do 'wear out' which shows in both a reduced spring rate, more damping in their operation and eventually, they break. Now, I'll defer to the professionals as to how quickly fork springs wear. I know it's not as quick as valve and clutch springs and I've seen some really old forks that still 'work' but I won't wager how close to the original spring rate they are, etc.

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  6. #6
    Lifer Ductard's Avatar
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    Re: Fork springs - can you swap with another person?

    Quote Originally Posted by Pigman View Post
    I have a set of .95's out of 06 GSXR 600 forks...don't know if thats what you are looking for..
    Hmm....I think Peter said I have 95's and need 1.0's in it, but that was a couple of rounds ago and I'm fuzzy. Plus it was my first time talking about spring weights, so I had no idea what the units were and don't trust my memory too much.

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    "Where are we going?...and why am I in this handbasket?"
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    '12 Ducati 1199 Panigale (track) '08 Honda CRF 250 (ice) '02 KTM 520 SX Supermoto (track)

  7. #7
    Lifer jasnmar's Avatar
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    Re: Fork springs - can you swap with another person?

    Just heard back from a contact at Racetech on this issue. He said that they don't provide a length measurement or standard on their springs, but they do a rate check to see if they are still performing adequately for their purpose. This makes sense, as Racetech does "straight" or "constant" rate springs.

    Other manufacturers, including some OEM use either multi or progressive rate springs, which makes the measurement of rate much less straight forward.

    So, again, it's complicated. Not impossible to trade, just complicated.

    If a spring is the right diameter to fit in your forks but the wrong length can it work? Maybe. If it is longer than it should be you may be able to use shorter spacers and still get it in there with a reasonable preload. So maybe. If it is shorter than it should be it may be possible to use longer spacers, but now you run the risk of bottoming out your forks earlier than you should be. You may have reduced your overall travel.

    If the rate is wrong, then the rate is wrong. You can get your sag number right using preload, but that doesn't make your rate correct, it just gets the sag right, which is just a starting point anyway.

    So "can springs from one bike be used in another?" it's complicated. I do agree that using the RaceTech reference for various models is a good place to start, but to do that we need to know the models in question.

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    Last edited by jasnmar; 09-15-14 at 05:42 PM. Reason: I type like an idiot

  8. #8
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    Re: Fork springs - can you swap with another person?

    Quote Originally Posted by Ductard View Post
    Hmm....I think Peter said I have 95's and need 1.0's in it, but that was a couple of rounds ago and I'm fuzzy. Plus it was my first time talking about spring weights, so I had no idea what the units were and don't trust my memory too much.
    I know you're going budget, but have you checked out Sonic Springs? $85 will get you a set for your GSXR . . .

    Take off one weekend day at NYST, and we can swap them into your bike in my garage.

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  9. #9
    TRACK RAT!!!!! Pigman's Avatar
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    Re: Fork springs - can you swap with another person?

    Quote Originally Posted by Ductard View Post
    Hmm....I think Peter said I have 95's and need 1.0's in it, but that was a couple of rounds ago and I'm fuzzy. Plus it was my first time talking about spring weights, so I had no idea what the units were and don't trust my memory too much.
    Whats your issue???

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  10. #10
    Lifer Ductard's Avatar
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    Fork springs - can you swap with another person?

    Quote Originally Posted by Pigman View Post
    Whats your issue???
    I've got one or those rubber rings to show how much travel I'm using...and it's every bit of it.

    Peter did a fork service on them during R5 and said stiffer springs would help.

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    Last edited by Ductard; 09-16-14 at 04:44 PM.
    "Where are we going?...and why am I in this handbasket?"
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    '12 Ducati 1199 Panigale (track) '08 Honda CRF 250 (ice) '02 KTM 520 SX Supermoto (track)

  11. #11
    Lifer Ductard's Avatar
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    Re: Fork springs - can you swap with another person?

    Quote Originally Posted by TrackRat View Post
    I know you're going budget, but have you checked out Sonic Springs? $85 will get you a set for your GSXR . . .

    Take off one weekend day at NYST, and we can swap them into your bike in my garage.
    I haven't checked. I guess I could just stop being a cheapass and buy new ones, but I thought they were $200+

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    "Where are we going?...and why am I in this handbasket?"
    LRRS 919
    '12 Ducati 1199 Panigale (track) '08 Honda CRF 250 (ice) '02 KTM 520 SX Supermoto (track)

  12. #12
    Lifer Ductard's Avatar
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    Re: Fork springs - can you swap with another person?

    Quote Originally Posted by TrackRat View Post
    Take off one weekend day at NYST, and we can swap them into your bike in my garage.
    You mean don't go to NYST or an LRRS round? Ninja please.

    Seriously though, with like 3 weeks left in the season I'm thinking of this as a winter project at this point anyways.

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    Last edited by Ductard; 09-17-14 at 12:42 PM.
    "Where are we going?...and why am I in this handbasket?"
    LRRS 919
    '12 Ducati 1199 Panigale (track) '08 Honda CRF 250 (ice) '02 KTM 520 SX Supermoto (track)

  13. #13
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    Re: Fork springs - can you swap with another person?

    Quote Originally Posted by Ductard View Post
    I haven't checked. I guess I could just stop being a cheapass and buy new ones, but I thought they were $200+
    Even ohlins springs are only $130. If you are running cartridge internals, mostly, the springs come off the top (with the forks unloaded) and should be a fairly easy swap. Some special tools needed.

    Don't hem and haw about fork springs. Just do it, and just buy new.

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  14. #14
    TRACK RAT!!!!! Pigman's Avatar
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    Re: Fork springs - can you swap with another person?

    I paid a 100 for .10's and raised the fluid level a bit....worked great.

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  15. #15
    Fork oil in my veins.... gmdboston's Avatar
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    Re: Fork springs - can you swap with another person?

    Quote Originally Posted by Ductard View Post
    I have a 2004 GSX-R 600 that I think was set up for a 180 lb. rider. I'm ~205 and the forks are pretty close to bottoming out.

    I also have a 2002 KTM 520 SX that was set up for whatever Tricky Mike weighs - if I recall was also ~180 lbs. Those aren't bottoming out, but I'm betting that if they are traveling more than they should it's probably hurting performance at least a little.


    Let's say I could find someone that needed softer springs, could I just swap with them?

    Wondering if springs are one of those things you only use once (like crush washers) or with one set of components (like a chain & sprocket, or brake rotor and pads).

    And if there is some reason why it would be a bad idea to use used springs (other than not *really* knowing how much they had been used) - is it a "best practice" or really important not to violate.

    And if it would be ok to swap....how specific are springs as far as compatibility?
    Are fork springs super generic, or do they only fit specific makes / models, or are they more specific than that (i.e. I have non-stock internals)?


    And finally...does anybody have any fork springs they want to trade?
    We sell fork springs for $130 a pair. you can swap them from bike to bike as long as they are the same length and diameter. The KTM springs will not fit in the GSXR if that is what you were asking. They don't "Wear out" per say, but springs do lose length as they get get older, called "Sacking". They do not lose rate until they are several million cycles old. Let me know if you have any other questions.

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  16. #16
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    Re: Fork springs - can you swap with another person?

    Quote Originally Posted by Ductard View Post
    You mean don't go to NYST or an LRRS round? Ninja please.

    Seriously though, with like 3 weeks left in the season I'm thinking of this as a winter project at this point anyways.
    Keep me posted. I'm out of Albany the week of Thanksgiving, but the garage is open until then. If I can get someone to buy the SV, I'll even have more space in there.

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