Cam Timing Question

Thread starter #1
I'm learning as I go so don't have much experience with all this but enjoying the process. I put a new 60x string on my Hoyt CRX32 today. I got the string put on no problem. Upon completion there was a considerable amount of cam lean in the top cam so I adjusted the yolks accordingly and got it straight. I then proceeded with setting the nocking point and tied soft nocks and d loop. Once I got the d loop on I proceeded to put on draw board. When the bottom stop was touching the top was right at 3/8" off.

Couple questions:
1. Is it normal to see this much difference in the timing with a new string?

2. How exactly do I corrrect, twist both yolks cable the same until the timing is correct?

I know from reading what others have said it will change as the string breaks in but I thought the 3/8" was pretty extreme to go any further in the tuning process without getting the timing a lot closer.
 
First, what you're checking is cam sync, often confused with timing. And yes, 3/8" is a lot. The first thing I have to ask before u start twisting cables, is did u check ATA length, brace height, and poundage? This would tell me which cable I would twist first.
 
Thread starter #3
ATA is 31 7/16. Brace height is 7". It's the number 2 cam. I did not check poundage, scale is being delivered tomorrow so don't have any way of checking at the moment.
 
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OK, u can move the top cam closer to the control cable, or move the bottom cam away from the buss cable by two things. Untwisting the control cable or twisting the buss. Since the buss has a big impact on ATA length, poundage, and draw length, start with untwisting the control cable given it has some twists to undo. Many string makers I see make it too short, and I have to rely on the buss cable for adjustments. But start with 3 turns out of the control cable if u can.
 
Thread starter #5
OK, u can move the top cam closer to the control cable, or move the bottom cam away from the buss cable by two things. Untwisting the control cable or twisting the buss. Since the buss has a big impact on ATA length, poundage, and draw length, start with untwisting the control cable given it has some twists to undo. Many string makers I see make it too short, and I have to rely on the buss cable for adjustments. But start with 3 turns out of the control cable if u can.
Thanks for the help and feedback. I will work on some more this evening and see if I can get in closer in line.
 
Thread starter #6
Ok I finally got my bow scale and am ready to move forward. I had forgotten to bottom out my limb bolts when I gave the previous measurements so I did that and proceeded to untwist the control cable 3 full twists. I put back on the draw board and the top stop was still off a good bit so I untwisted 2 more full twists.

As of right now, when the bottom cam is hitting, the top cam is right at 1/8" off still. My ata measurement is 31.5"(tune chart says 31 3/8"). My draw weight is 67 lbs.

In my mind this makes sense. If the ata measurement is too long there is not as much tension on the limbs so the draw weight would be less. Kris also said that twisting the buss cables would take the bottom stop further away from the cam and I guess that would decrease the ata measurement and increase draw weight all at the same time. Am I correct and if so how many twists would you recommend adding to the buss cable? Do you make the adjustments to the buss cable at the bottom cam or twist equally both yolks at the top?
 
You're on the right track. One twist on the buss will move the cam more than one twist of the control. Start with one full twist and recheck. I normally do it at the yokes if they're not twisted up much unless I need to make big adjustments. But top or bottom is fine.
 
Thread starter #8
Ok I added 1 twist to the buss cable and rechecked. Now the top stop is hitting and the bottom is right at 1/16" or slightly less off. The ata didn't really change, it's still at 31.5. My scale is being a bit finicky but I think its right at 70.2ish now. Where does this leave me? Close enough to move on or need some minor tweaks?
 
Thread starter #10
Ok I finally got my paper tuning stand built and proceeded with paper tuning my setup.

This first picture is at 5 feet. The bottom tear I think was me. When removing the arrow from the target it was pointing downward considerably so I don't think I was holding my arm very level. The other 3 looked pretty good to me so I backed up to 10 feet.
IMG_2939.JPG

This is from 10 feet and each look to be low and a little to the right to me.
IMG_2940.JPG

A couple questions:

First and foremost as you can see I am not using a bare shaft. Should I be using a bare shaft in order to show as much variance as possible? Does it make that much of a difference?

If I need to go rip some vanes off an arrow and re-shoot I certainly will but based on the tears what would you guys recommend in order to fix it.
 
You have a slightly high left tear. You call the tear by the back of the shaft, not the point. Its not bad. But I would shoot a bareshaft to see what's happening. It NEVER lies. :)
 
Thread starter #12
So right after I posted earlier I knew I probably should go ahead and shoot a bare shaft so I went ahead and stripped vanes off an arrow and proceeded to shoot. I also was still at peak draw weight so I decided to go ahead and lower to around 66 lbs. In the process of doing so my limb bolt "receivers" (I'm not sure if that is the correct term) started rotating along with my actual limb bolts so I had to put some oil on the bolts to get them to break up a little bit. After I was able to start turning the actual limb bolts I got them back as close as I could and shot some more. The bare shaft told a similar story and I proceeded to adjust the limb bolts slightly to get back closer.

The below picture is my latest group. I think it is still a slight high left tear(the top two holes are two shots) but closer than it was after the limb bolt fiasco. Right now my top tiller measurement is 12 13/16" and my bottom is 12 7/8". My ata is still right at 31.5". I also put back on draw board and while my top stop is hitting my bottom is right at 1/16" off.

So where do I go from here?

IMG_2947.jpg
 
I'd call it good. If u wanna back up some more, u could just to see what it does. But those are great holes, and would surely shoot great groups. Good job.
 
Thread starter #14
That last group was at 10'. How far can I safely go back and still shoot the bare shafts? Also, is there a tolerance for the tiller and ata measurements that they should fall within? I'm a bit of a perfectionist so it kind of bothers me that the tiller measurements don't measure exactly the same. Am I overthinking way too much and as long as the paper tune is good, forget about the rest of it?
 
Yep, don't overthink it. Specs are just guidelines, and bows are hardly ever perfect. U can make a bow shoot a clean hole by setting them up all kinda different ways. As long as it holds on target well, and shoots consistent groups, that's all that matters. Think of it this way....if u try to fix that itty bitty bit of tiller, then you're gonna have to change something else to get the clean flight u already have. I'd be happy with it.
 
Thread starter #16
I've been back at it today. I proceeded with tying peep sight in and installing all the string silencers and everything just like I intend to hunt with. I then proceeded to shoot through paper again figuring it would still be good and to my surprise I had about a 1.5" left tear. I didn't see that coming but I guess any little change or twisting of the strings could have that much of an impact. I proceeded to add twist into the left yoke and out of the right until the left tear was gone. It took three full turns but is now shooting good bullet holes again. With the adding of the twists I now have what I would consider to a good amount of cam lean. I know this is needed after following Brewskis thread. I also put back on the draw board and now when my bottom stop is hitting the top is about 1/8" off.

A couple questions:

Should I try to adjust to get the stops a little closer or have the top slightly ahead of the bottom or if it's still shooting bullet holes should I leave alone?

Also how much cam lean is too much at rest or is there no such thing as too much? When I put an arrow on the left side of the top cam, the arrow is hitting about halfway between the D-loop and peep sight.
 
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You definitely don't want the bottom cam ahead. Fix your cam sync before u do anything else. Get the top ahead slightly or at least dead even before u make any changes to anything else.
 
Thread starter #18
I adjusted the sync by untwisting the control cable one full turn. I put back on draw board and the top is now hitting while the bottom is less than 1/16" off. I decided to go ahead and recheck all my measurements and lo and behold my center shot had somehow moved slightly so that makes sense with the left tears I started getting. I adjusted back to 3/4" and my left tears went away. All my other measurements check out spot on so I'm pretty happy. Moral of the story for myself is check and recheck everything and make sure everything is tightened down properly before you start making all kind of adjustments. I'm still getting a very slight high tear but it is close enough for me until I get enough arrows shot to make sure everything has settled.

I proceeded with shooting bare and fletched arrows at some distance just to see what it would do. At 10 yards they are stacking on top of each other and are flying very true(i.e. bare and fletched arrows are perfectly parallel when entering the target). At 20 yards they are still hitting within a couple inches of each other but you can definitely see some variations in the bare shaft as far as flying straight. I'll blame that on my form and the 15 mph winds outside for now.

I checked my prelean again very closely and the shaft is intersecting the string at just above the peep sight.
2015-02-23 Prelean.jpg

Is this too much prelean? I know it is probably going to vary a lot but is there a ballpark for how much prelean would be considered ideal?
 
That's more than I normally see but nothing to be concerned about. You probably have a lot of grip pressure on the right side of the bow. You can play with different grips if u want, but if its comfortable and shooting OK, I wouldn't let that prelean bother me.
 
Thread starter #20
That's more than I normally see but nothing to be concerned about. You probably have a lot of grip pressure on the right side of the bow. You can play with different grips if u want, but if its comfortable and shooting OK, I wouldn't let that prelean bother me.
Thanks for all of the help Kris.
 
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