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Thread: Hoyt Carbon Matrix with RKT Cam, Tuning Question

  1. #1
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    Hoyt Carbon Matrix with RKT Cam, Tuning Question

    I have been tuning bows for a while and am comfortable setting timing, ATA, BH, etc. I have never had the problem I am seeing on this bow...need some advice. The limb bolts are buried so I am starting from the normal starting point.

    With the #3 cams and a B module in the RKT cam (and draw peg in B), the DL should be 29.5". When I set up the bow to 35 7/16" ATA +/- 1/16", I get a BH just about perfect at 6 3/4". My dilemma comes with the draw weight and strings. BTW, cam rotation looks good and it is smooth shooting at this point.

    My buss/control cables are nearly straight (very little twist) but my string is twisted really tight. Again, ATA, BH and DL are correct (or close enough) at this point. Cam timing looks good. These are NOT Hoyt strings.

    Now the problem....draw weight is only 65# on a 70# bow which should be the final test of tuning. If I lengthen the string, I get to 70# but only when the DL is 1" longer than it should be.



    Is this a limb problem or am I missing something?

    Thoughts?
    Steve C
    Chesterton, IN

    Hoyt Carbon Spyder 34, QAD HD Rest. Carbon Express Maxima Reds, X-Busters, Spott Hogg Sight
    Through Christ, All Things Are Possible!:amen


  2. #2
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    What year matrix? is this a matrix that came with fuel or xtr? i would pm Ray knight he can help. Good luck

  3. #3
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    It is a 2012 Hoyt Matrix with the RKT cam.
    Steve C
    Chesterton, IN

    Hoyt Carbon Spyder 34, QAD HD Rest. Carbon Express Maxima Reds, X-Busters, Spott Hogg Sight
    Through Christ, All Things Are Possible!:amen

  4. #4

    Hoyt Carbon Matrix with RKT Cam, Tuning Question

    Can you measure your strings and cables? Is it a long draw model? Also if you can post a pic of the cable side of the bottom cam at rest. Are your limbs backed out? Or down all the way?
    AT Sponsor www.lum-tec.com Coupon code: Archerytalk111
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  5. #5

    Hoyt Carbon Matrix with RKT Cam, Tuning Question

    Longer cables will power draw weight and lower draw length. Shorter string will take weight off and increase holding weight/decrease valley as well as shorten draw length. My best guess is your strings are not sized properly. They may be for the long draw model. And those string measurements from Hoyt's tune charts are off. I have spoken to them a few times about them as well. If you use those lengths the DL is way too long. I had to go 1" short on the string to get it right.
    AT Sponsor www.lum-tec.com Coupon code: Archerytalk111
    Eliminate the fixed roller guard on Carbon Matrix and Carbon Spyder. Click HERE. Aluminum Hoyts click HERE
    NEW: TPU Speed nock system. Available HERE. *** Brownell bowstring products distributor *** Email wis913@yahoo.com for a full price list.

  6. #6
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    Here is the picture of the bottom cam, cable side. To answer your question above, the limbs are buried so I was expecting 70# given the other measurements. I am not sure if the starting cam position is right however...cables are just about without twist now. It is not a long draw model, I did measure the string and control cable and they were close to what the tune charts call for. However, if I used the factory string dimension, I was 1" long in DL>

    bottom cam.jpg
    Steve C
    Chesterton, IN

    Hoyt Carbon Spyder 34, QAD HD Rest. Carbon Express Maxima Reds, X-Busters, Spott Hogg Sight
    Through Christ, All Things Are Possible!:amen

  7. #7
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    how did this problem arise?? did you swap strings and trying to get into tune? or did you buy this bow this way?? SO buss seems twisted fine, control cable is straght and string is super twisted up right??
    Hoyt Vector35 - QAD - Spot-Hogg - Doinker - Easton - FOB's
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  8. #8
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    I bought the bow new last summer...was for my son. He wanted new strings due to some fraying on the factory string around the peep so we put A-B on last fall. He has grown so much that the extra 1/2+ of DL at 30" actually worked for him. With 30" modules and a DL (measured) of 30.5"+, ATA was OK and so was the draw weight. String twist was normal.

    He is now shooting a PSE for indoor so I am shooting his bow. My DL is around 29.5" I started twisting the string with the B modules installed to get to 29.5". That is where I noticed the ATA starting to shorten with all the string twist so I untwisted the cables to maintain ATA at spec the best I could. Both cables are nearly without twist. The string is tightly twisted. With ATA very close, BH good, and cam timing good, my DW is only 65#.
    Steve C
    Chesterton, IN

    Hoyt Carbon Spyder 34, QAD HD Rest. Carbon Express Maxima Reds, X-Busters, Spott Hogg Sight
    Through Christ, All Things Are Possible!:amen

  9. #9

    Hoyt Carbon Matrix with RKT Cam, Tuning Question

    Quote Originally Posted by srcarlso View Post
    Here is the picture of the bottom cam, cable side. To answer your question above, the limbs are buried so I was expecting 70# given the other measurements. I am not sure if the starting cam position is right however...cables are just about without twist now. It is not a long draw model, I did measure the string and control cable and they were close to what the tune charts call for. However, if I used the factory string dimension, I was 1" long in DL>

    bottom cam.jpg
    I can tell by that pic that either the string is short or the cables are long. At factory settings, the peg that mounts the lower control cable is almost fully wrapped around. Its pretty far away in that picture. I have a feeling the string and cable lengths are both off.
    AT Sponsor www.lum-tec.com Coupon code: Archerytalk111
    Eliminate the fixed roller guard on Carbon Matrix and Carbon Spyder. Click HERE. Aluminum Hoyts click HERE
    NEW: TPU Speed nock system. Available HERE. *** Brownell bowstring products distributor *** Email wis913@yahoo.com for a full price list.

  10. #10

    Hoyt Carbon Matrix with RKT Cam, Tuning Question

    Quote Originally Posted by srcarlso View Post
    I bought the bow new last summer...was for my son. He wanted new strings due to some fraying on the factory string around the peep so we put A-B on last fall. He has grown so much that the extra 1/2+ of DL at 30" actually worked for him. With 30" modules and a DL (measured) of 30.5"+, ATA was OK and so was the draw weight. String twist was normal.

    He is now shooting a PSE for indoor so I am shooting his bow. My DL is around 29.5" I started twisting the string with the B modules installed to get to 29.5". That is where I noticed the ATA starting to shorten with all the string twist so I untwisted the cables to maintain ATA at spec the best I could. Both cables are nearly without twist. The string is tightly twisted. With ATA very close, BH good, and cam timing good, my DW is only 65#.
    Thats exactly what happens with longer cables and shorter string. Shorter DL, lower draw weight, higher holding weight, less valley. With that many twists out of the cables, you are going to ruin them. Eventually they will begin to untwist under the servings and you will have issues with that.
    AT Sponsor www.lum-tec.com Coupon code: Archerytalk111
    Eliminate the fixed roller guard on Carbon Matrix and Carbon Spyder. Click HERE. Aluminum Hoyts click HERE
    NEW: TPU Speed nock system. Available HERE. *** Brownell bowstring products distributor *** Email wis913@yahoo.com for a full price list.

  11. #11
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    Quote Originally Posted by Ray knight View Post
    Thats exactly what happens with longer cables and shorter string. Shorter DL, lower draw weight, higher holding weight, less valley. With that many twists out of the cables, you are going to ruin them. Eventually they will begin to untwist under the servings and you will have issues with that.
    Agreed...getting new cables and strings (again). I am not shooting it like this...was trying to get the bow into spec which I cannot.
    Steve C
    Chesterton, IN

    Hoyt Carbon Spyder 34, QAD HD Rest. Carbon Express Maxima Reds, X-Busters, Spott Hogg Sight
    Through Christ, All Things Are Possible!:amen

  12. #12
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    Quote Originally Posted by Ray knight View Post
    I can tell by that pic that either the string is short or the cables are long. At factory settings, the peg that mounts the lower control cable is almost fully wrapped around. Its pretty far away in that picture. I have a feeling the string and cable lengths are both off.
    Thanks for the input....it is appreciated. I have no room to untwist the cables to get the peg around and if I try to twist up the lower cable in the pic my ATA is way off.
    Steve C
    Chesterton, IN

    Hoyt Carbon Spyder 34, QAD HD Rest. Carbon Express Maxima Reds, X-Busters, Spott Hogg Sight
    Through Christ, All Things Are Possible!:amen

  13. #13

    Hoyt Carbon Matrix with RKT Cam, Tuning Question

    Quote Originally Posted by srcarlso View Post
    Thanks for the input....it is appreciated. I have no room to untwist the cables to get the peg around and if I try to twist up the lower cable in the pic my ATA is way off.
    I suggest measure your strings! I still think they are going to be off quite a bit.
    AT Sponsor www.lum-tec.com Coupon code: Archerytalk111
    Eliminate the fixed roller guard on Carbon Matrix and Carbon Spyder. Click HERE. Aluminum Hoyts click HERE
    NEW: TPU Speed nock system. Available HERE. *** Brownell bowstring products distributor *** Email wis913@yahoo.com for a full price list.

  14. #14
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    Quote Originally Posted by Ray knight View Post
    I suggest measure your strings! I still think they are going to be off quite a bit.
    Since the buss cable was straight, I ordered new strings and put them on today. With very little work on tuning, all the measurements came in right on spec including ATA, DW, BH, DL. Cam timing is good and starting position is right where it should be. Twists on string and both cables look good...no where near straight.

    Thanks for the comments guys!
    Steve C
    Chesterton, IN

    Hoyt Carbon Spyder 34, QAD HD Rest. Carbon Express Maxima Reds, X-Busters, Spott Hogg Sight
    Through Christ, All Things Are Possible!:amen

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