Why the Slower FPS?

[Mitten_archery13]

Hey there.
I am fairly new to bow tuning and learning ot as I go.
My current setup lost FPS compared to a month ago and I am confused as to why.

Here is a little background as to what was going on with my bow.
Ordered new 70 pound limbs last summer and installed two months ago.

I was practicing the other night for TAC and the bow string came apart. Not sure how old string was as I bought the bow used.
Called around and had a custom string made, from my understanding a reputable builder, since no shops around had one in stock.
Installed the string, increased draw weight to 74 pounds by technician twisting the cables.
Paper tuned.
Shot 12-18 arrows while tuning

Shooting same arrows as other month but lost 5fps.

Specs:
2015 Hoyt Carbon Spyder ZT Turbo
Cam # 3. 29 1/2” DL
70 pounds limbs, pulling 74 on scale.
580 gn arrow.

Old FPS was 265@ 70 pounds
New FPS is 260 @ 74 pounds

Am I understanding this correctly, twisting cable = increase in draw weight and length, which should increase FPS?

What would the reasoning be for decreased velocity? I was hoping the velocity would increase after everything was done.

 

[Joe Holden]

Have you verified if specs are correct? ATA/Brace?

 

[BillNye]

String, knock, or peep weight going up could slow you down pretty easily

 

[sndmn11]

Did you switch chronographs?

 

[Stache Attack]

Different string material maybe, stiffer like 452x will be slower compared to some of the stretchy blends some of the new makers are using. Ie. that’s why system x gas strings are faster but you can feel the stretch in the back wall compared to ghost. I would check your specs though

 

[Mighty Mouse]

Increasing draw weight will increase speed, all else equal. Did you measure your draw weight before the string change when you were getting 265 fps?

Optical chronographs are notoriously finicky. Unless you're shooting the same arrow through the same chrono in the same lighting conditions, I wouldn't put much stock in the speed comparison.

 

[Mitten_archery13]

I have not checked to make sure everything is within spec. I.E, ATA and brace height. I will check when able to

Nothing on the arrows has changed. Same nock, etc.
Shot through the same chronograph at same distance.
I am using a Catfish custom string, 452X
The peep sight might have changed size by a hair but pretty sure it’s the same. Same brand, model as previous.

 

[blackveltbowhunter]

What about the weight scale? There is often variance between them as well.
Combining the weight AND speed difference that's a sizable enough change that ( given the bow is shooting well and tuned ) I would very likely be looking at discrepancies in testing equipment rather than the bow changing that much. I would imagine the 452 slowing the bow down a bit from stock strings although 5 pounds plus the presumed added DW would be excessive. If your ATA and BH are close and the bow shoots good, I wouldn't fret over anything.

 

[SippyCup]

I’d check the specs of the bow. Brace height and axle to axel first. If those are on is has to be the string material used.

 

[Mitten_archery13]

ATA spec are 33”
Brace height spec is 6”
For ATA I cut 4” on tape.

Does the roller guard normally have that much angle/ twist?