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  • Shimming Cams, Swapping Limbs

    Hello EAF. Hoping a few can set my mind at ease. I've read quite a bit where some have had difficulty gaining proper clearance to achieve l/r center shot. Suggestions have been to shim the cams to draw the string toward the riser, or the reverse, push it away. Another frequent response is to swap the limbs top to bottom.

    I've done all of my bow tuning for 20+ years, but can not afford a new compatible press AND a GT500 at the same time. Therefore, I will be forced to rely on a shop and shop labor to tune the bow after I have it shot in. Not looking forward to that. Therefore, I want to have sufficient knowledge of the bow to ensure that it is correct the first time. This brings me to my questions:

    1) How commonplace is this concern? Is it routine to need to adjust the orientation of the lims and/or cams?

    2) What is the root cause in bows that need additional modification?

    .....A) Are the limbs machined out of square from the attachment at the pocket?

    .....B) Are the cutouts for the cam machined off center?

    .....C) Is the deflection different across the face of the lims causing the cam to move off center from a twisting or torquing of the limb?

    3) Is there a way to check the bow at rest to determine if there is a likely issue before purchase? In other words, is there a standard value that the center of the arrow SHOULD be set at from the face of the riser with a corresponding center shot measurement to the center of the string? I am guessing that if the measurements were begun in reverse- at the rest based on spec, (rather than off the bowstring) AND the cams were skewed left or right, then the center shot would be considerably off when measured back to the string, right?

    I know all bows (and shooters) are individual, and slight variances are normal. I'm looking for big-picture knowledge here. Thanks to all who might help settle my concern.
    Never strive for perfection. Remember what it got the last guy? God, please guide my arrow and my life on a true course. Amen.

  • #2
    The short answer to your question is the limb inconsistency between the forks. It's basically a problem caused by the limb vendor.
    The shim change is necessary to tighten the cam between the forks and move the cam closer to the center of the riser.
    The tighter shims eliminate cam lean also.

    There are a lot of GT500's and Z28's that need to have them. If your CS is past 7/8"(or real close) and you can't get a bullet hole at that CS , you can figure you need shims.
    2014 E32
    2011 PULSE AP
    TUNER OF BOWS BY LONG DISTANCE
    Member of the JURY MEMBER OF THE LEFTY BROTHERHOOD




    "If it ain't broke , I can MAKE it better".
    Integrity is doing the right thing when no one is looking.

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    • #3
      Yeah, what he said. The only thing you can do before you buy it is to papertune with the rest at 7/8, if it will tune there or very close to that you should have no problem. The one's with a center shot issue wanted to have the rest over an inch center shot causing sight and rest problems. The shims can be a fix but some have need to swap out the limbs, both of mine (GT500 and XLR) I swapped the limbs and it fixed it. I had a Z28 that was perfect from factory.
      2011 Pure Sno AT 29/60
      Frequent Frankenbower

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      • #4
        Mine is just past 7/8 center shot. its fine. I dont think it common to have to shim or swap limbs. swapping limbs though has been done for years by tuners its not new. shimming cams also.
        No ifs and or buts Just maybee.

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        • #5
          The deal is with Binary cams that there is no cable or strings hooked to the limbs. So to adjust any minor limb twist (I mean minor) you have to shim the cams a few thousanths one way or the other to correct. It has the same effect as twisting a Yoke on other popular brands (mathews, Hoyt etc.)

          There is just a small % of these bows that even need this done, and your dealer should take care of all of this.

          Almost every Mathews I have ever tuned and worked on had to be pressed and have idler lean induced to make it stop left tearing. This is the same thing, it is just done a little different becasue of the way the binary cam is.

          There is just to many small variances in manufacturing to have them all leave the factory perfect. That is what the dealer is for !
          Mountain Gunworks & Archery
          Elite Dealer
          Proline Strings
          BoCoMo slings

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          • #6
            Thanks to all so far. Starting to understand it a bit better I believe. New to binary cams, but love the feel of the Revolution. It's like magic. Last bow was ughhum, a single cam. Have no interest in buying half a bow again!
            Never strive for perfection. Remember what it got the last guy? God, please guide my arrow and my life on a true course. Amen.

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            • #7
              Center Shot

              So is the limb swap done to counter limb twist?

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              • #8
                I think half of the trouble you hear are due to fletching contact or bad form. It seems people read about the spacer issue and that is immedaitly what they blame it on.
                -- that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion -- that we here highly resolve that these dead shall not have died in vain -- that this nation, under God, shall have a new birth of freedom -- and that government of the people, by the people, for the people, shall not perish from the earth.



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                • #9
                  Originally posted by vhunter View Post
                  I think half of the trouble you hear are due to fletching contact or bad form. It seems people read about the spacer issue and that is immedaitly what they blame it on.
                  AMEN ! Like I said, Very small % with actual problems ! And when there is it is a very easy fix !
                  Mountain Gunworks & Archery
                  Elite Dealer
                  Proline Strings
                  BoCoMo slings

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                  • #10
                    Fall away rest

                    Originally posted by Antlerquest View Post
                    Thanks to all so far. Starting to understand it a bit better I believe. New to binary cams, but love the feel of the Revolution. It's like magic. Last bow was ughhum, a single cam. Have no interest in buying half a bow again!

                    I did notice attaching anything to the cable can change center shot as well. Atleast this was the case for me. My cam has a small cam lean at full draw on my gt500. Sure isnt effecting the center shot or groups while shooting. Im now shooting a launcher blade on a Trophy Taker. Put the bowplane tool on it last night and my centershot is real close.
                    DB
                    OK-Archery DST 40, 09 Elite Z28, Vortex binos 15X50 Vipers , Carter releases, Trophy Taker rests, Vapor Trail strings, Custom Bow Equipment sights, Goldtip arrows. B Stinger Stabilizers. Slick Tricks

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                    • #11
                      Originally posted by vhunter View Post
                      I think half of the trouble you hear are due to fletching contact or bad form. It seems people read about the spacer issue and that is immedaitly what they blame it on.
                      I know what you're saying and I agree to a point but there are some who are very confident in their shooting and tuning and they have had issues. The first thing we do at times is to say "oh, it's torque". I've found that it's hard to torque the new cams, if you get that dreaded rt. tear it stays there until you get the rest way the heck out from the riser. You literally have to choke the bow to get it out. Elites in the past have not been known for center shot issues so if you've shot the old ones and now all of a sudden you have a rt. tear problem sometimes it could be the bow. Just because our bow is fine doesn't mean everyone else's is.
                      2011 Pure Sno AT 29/60
                      Frequent Frankenbower

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                      • #12
                        Originally posted by archer58inPA View Post
                        The short answer to your question is the limb inconsistency between the forks. It's basically a problem caused by the limb vendor.
                        The shim change is necessary to tighten the cam between the forks and move the cam closer to the center of the riser.
                        The tighter shims eliminate cam lean also.

                        There are a lot of GT500's and Z28's that need to have them. If your CS is past 7/8"(or real close) and you can't get a bullet hole at that CS , you can figure you need shims.
                        Isn't the Limb vendor Barnsdale??? Are you saying he makes limbs that are inconsistent?
                        Bowhunting...Pure and simple

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                        • #13
                          Limb swap

                          Originally posted by harleyryder View Post
                          Isn't the Limb vendor Barnsdale??? Are you saying he makes limbs that are inconsistent?
                          x2 Is the limb swap to counter twisting? It is said that only a few have this problem. So is this limb swap just masking a bigger problem with the limbs? Should a new bow owner be worried and request a new set of limbs?

                          Comment


                          • #14
                            Originally posted by out west View Post
                            x2 Is the limb swap to counter twisting? It is said that only a few have this problem. So is this limb swap just masking a bigger problem with the limbs? Should a new bow owner be worried and request a new set of limbs?
                            Im starting to wonder if that its one of the issues. Month or so ago I shimmed cams, it shot better not perfect but well, over that month with nothing changing(except some slight lean) I developed a bad tear in paper and bad arrow flight, tried everything...again.... swapped limbs and its back to shooting pretty good. I do think I need to shim further right, and that might square everything up but...pretty frustrating to have to do this to a new bow and worried it will "give" over another period of time.
                            Wanted to add something that Lariat touched on, the bow still groups very very well. It just doesnt have the same perfect arrow flight I could get out of many Elites Ive owned or shot. And I will NOT settle for less, supposed to be PERFECTED EXCELLENCE right?
                            Last edited by L-train; 01-20-2009, 04:41 PM.

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                            • #15
                              I am probably the poster child for having this problem. I have not swapped limbs yet, but I have tried EVERYTHING else so far and have not gotten it solved. With that said, this bow still groups really good but the arrow flight off the bow is less than perfect.

                              I am sending my bow to Elite Greg (he has been nothing short of awesome) and let him perfect the excellence.
                              The rewards of a successful hunt last forever.---author: Nate Simmons.

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