[Falconer4ever]

Vent,

Unbelievable detail....had not thought about several of the issues you mention. Especially, the "sensitivity" involved with only slight deviation in cam rotation!
Will be doing alot of chewin' on your comments...
Really appreciate your advice!

 

[Falconer4ever]

I wouldn’t think a detuned bow would shoot efficiently as originally intended but maybe they will.

When I had my 150# limbs on my Ventilator, I think it shot 384/386 fps. It was a bear to cock and nearly impossible with the short sled and my long arms.

So I ordered some 125# limbs from Wyvern - it was much easier to cock and still shot 372 fps. Big deal for 12 feet.

Great point, TP.....thanks much for real-world data speeds....

 

[lonny996]

Option 2 with heavier arrow

 

[Huntersthompson]

Exit

 

[Iron Duke]

Lordy Lordy ... just use the 135lb limbs as is. Don't act like a purse swinger. 😂 135lb limbs are so unstressed already that they'd last a thousand years! Why start jerking around with odd length strings that will void your warrantee for no good reason? To me that's gambling to lose, not gambling to win. If you have some misguided desire to slow a good crossbow down just put a stupid heavy arrow in the 135lb crossbow. I think Moon Longstring can make you up some 754gr Easton FMJ's ...lol I'd go with the 135's every single time. Like Vice Lombardi said: "a good big man will beat a good small man every time." Remember: "If a little bit is good, a lot is better."

 

[tpcollins]

Back in my vertical compound days, I was under the impression the bow shot the best at the maximum poundage listed - not the least on a 60-70 pound bow for example.

I would think it wouldn’t be any different for crossbows but maybe it is.

 

[Iron Duke]

Back in my vertical compound days, I was under the impression the bow shot the best at the maximum poundage listed - not the least on a 60-70 pound bow for example.

I would think it wouldn’t be any different for crossbows but maybe it is.

Bow engineers ... make strings & cables a certain length for good reason would be my guess. Strings, cables, limbs, cams are all a system. Changing the dimensions of any of them could very well effect all the others in a way you are clueless to realize. Why would they make 110lb limbs if they could just change string length to get 135lb limbs to act the same way? It's like putting different size tires on your truck thinking you know more than the Ford engineers.

 

[rt2bowhunter]

What I think is being missed. A 150# set of limbs on a bow made to shoot let’s say 350 fps. Is still stressed as much as a 200# set of limbs on a bow made to shoot 400fps. Only when you take the 200# limbs and detune the bow to shoot 350fps or the same as the bow built to shoot 350fps stressed. Have you gained anything pertaining to durability.

A great example would be the Excalibur 405. It was problematic shooting 405 fps. But with the rail cut down as Excalibur did(or detuned) making the 350 a very dependable bow. That had the same limbs same everything but just detuned by shorting the draw.

Mission gives another great example. The mxb 320 at least mine shot 333 fps with a 401 gr arrow. And was a 4 cylinder working hard to run its speed limit.
But the mxb 400 that will shoot a 401 gr arrow 413 fps is a v8 being very lazy. With the limbs backed off shooting/run 333 fps.

The question is will you be happy and is this what you want.

 

[Déjà vu]

Here is the situation:

A crossbow I am very interested in is offered in both 110 lb. limbs and 135 lb. limbs.
The 110 lb limbs are fast enough for my purposes.

However, I am very interested in limb durability, reliability, longevity and minimal center serving wear.

So, trying to decide whether to:

A) Go with the 110 lb. limbs and standard / factory-spec string and cable length....or

B) Go with 135 lb. limbs and "detune" them by using a slightly longer string and cables.

Option "B" would shoot somewhat faster than the standard 110, but considerably slower than standard 135's. Advantages are since 135 limbs are not fully-stressed, they should last longer, perhaps have less serving wear, shoot quieter, and offer slightly more speed

Option "A" would cock a little easier and probably be a little quieter, definitely slower. Possibly also have less serving wear.

Those of you who have "detuned" a crossbow in this manner, I would appreciate your thoughts on why you did it, what your goals were and what was the outcome?

It is always best to ramp up with a stronger build then detune if you are looking to increase the lifespan of something.
I was talking with a crossbow company about durability a few years back. At the time of the conversation they had 4 models. I was told they have never had one of their two lightest limb bows come back for limb failures. He also said the second fastest was rare to see a failure. So 99.99% of their limb failures was their heaviest limb bow.
He went on to say that even with their heaviest limb bow they detune it to about 80% of its ability so they still don't see a lot of failures

 

[rt2bowhunter]

Back in my vertical compound days, I was under the impression the bow shot the best at the maximum poundage listed - not the least on a 60-70 pound bow for example.

I would think it wouldn’t be any different for crossbows but maybe it is.

I don’t think they shot there best unless you think the best means faster. If you take a 50 to 60 pound bow and shoot it maxed out. It will shoot the same arrow faster than a bow, that’s 60 to 70 pounds set at 60 pounds. Because they made the limbs heavier stronger to stand the 70 pounds. More weight to move when the string is dropped.
So a 60 to 70# bow would be a better choice as far as durability goes. If you shot it at lighter poundage.
Accuracy would not be affected.

 

[SEW]

Tp and Rt,
I think you are both correct. A 60# limbed vertical bow just felt better shooting at max weight than a 70# limbed bow detuned to 60#. But, I suspect that the latter was less stressed and would last longer.

I rarely have limb problems and run my xbows about 10-15’/sec slower than rated. Only my Excals (400BD and M405s ) had limb failures but a significant contributor was the sharp, too tight riser pockets plus the hard edge where the limbs exited the riser.

 

[tpcollins]

It just seems that tighten down versus loosey goose would optimize the bow’s performance better.

PSE recommends I can back the limb bolts out 6 turns on my Bow Madness. Each turn supposedly represents 2 1/2 pound, so I could turn the 60-70 pound rating to 55 pounds.

However, the limb bolts will turn 23 times before coming out. If I back them out 10 turns (still have 13 threads left) that should drop it to 45 pounds. How efficient do you it would shoot with cams, strings, and cable set for a specific tune like Duke said?

I also have a set of 50-60# limbs for that bow that I had on it for awhile when my rotator cuff started going bad.

It would have been easier to just turn the limb bolts out more to lower the poundage that much - PSE must have had a reason not to do that. (I’m aware my Dagger’s poundage could be lowered by turning the limb bolts out as well - not sure how effective it would have been at the lowest recommendation).

 

[Jack Pine]

Some may be making detuning more complicated than it needs to be; just shoot a heavier arrow. That's it, it's really profoundly simple. You don't have to have different length strings & cables.

 

[ramrod]

For me, I ordered a 110. Why would someone do that? Both shoulders have been repaired and three weeks ago my neck. I want one bow I can shoot a lot that doesn’t have a crank. The bow chrono’d 370 with a 400. Rex actually called me and asked if that was good enough. It was to me and I’ll be shooting those 400gr arrows. That Tremor with 110’s will be a bullet proof fun bow to shoot. It will also zip through any deer I shoot at. The 135 may be the best compromise when it comes to a Scorpyd. Vent is correct, those cams have that designed let off engineered in. They also are engineered to widen the string angle and reduce the holding weight when cocked. You would be removing those features detuning the bow.

 

[rt2bowhunter]

Some may be making detuning more complicated than it needs to be; just shoot a heavier arrow. That's it, it's really profoundly simple. You don't have to have different length strings & cables.

True but that don’t address IMO the main problem. Being cocked maxed out. It has to be more stressful if a bow is cocked for hours max poundage vs cocked under less.

 

[Jack Pine]

True but that don’t address IMO the main problem. Being cocked maxed out. It has to be more stressful if a bow is cocked for hours max poundage vs cocked under less.

We have no disagreement there.

 

[Runningbuck]

Go with the 110 and shoot it as designed. If its enough horsepower to fit your needs why run something at half throttle?Bigger is not always better, and faster just wears things out quicker. Detuning just creates a whole new list of problems down the road.

 

[tpcollins]

A bit of a different situation but back in a previous life - aka 1st marriage - I lived about 10 miles from Dan Fitzgerald’s store (I know). He was a dealer for Martin and was showing off his 100# bow. He pulled it back and anchored it with not problems. My butt couldn’t budge the string.

He pointed to the gap between the limb pocket and riser and I could see 2 steel ball bearings in that gap. He said Marting used the same limbs for all bows and just used different size ball bearing to increase/decrease the limb’s angle for different poundage bows - sort of one size fits all.

I remember long ago compound shooters would shim the edge of the riser to limb opening to stress the limb more to gain more speed, don’t know how that worked out.

However, my PSE Bow Madness has an adjustable draw length of 25” to 30” - one would think you could get the same 70# max weight at either 25” or 30” draw length. If so, I wonder if the ATA at rest and at full draw would be the same?

 

[Jack Pine]

A bit of a different situation but back in a previous life - aka 1st marriage - I lived about 10 miles from Dan Fitzgerald’s store (I know). He was a dealer for Martin and was showing off his 100# bow. He pulled it back and anchored it with not problems. My butt couldn’t budge the string.

He pointed to the gap between the limb pocket and riser and I could see 2 steel ball bearings in that gap. He said Marting used the same limbs for all bows and just used different size ball bearing to increase/decrease the limb’s angle for different poundage bows - sort of one size fits all.

I remember long ago compound shooters would shim the edge of the riser to limb opening to stress the limb more to gain more speed, don’t know how that worked out.

However, my PSE Bow Madness has an adjustable draw length of 25” to 30” - one would think you could get the same 70# max weight at either 25” or 30” draw length. If so, I wonder if the ATA at rest and at full draw would be the same?

Yep, probably around 45 or so years ago, I had a vert compound that used "weight wedges" to stress/relax the limbs. It was a Jennings model T; normally 60lb, but could be 55 or 65 depending on the direction the wedges were installed. Worked great.

 

[Joseph_A_Feiccabrino_Jr]

Scorypd makes crossbows for everyone. They make low-pound limbs for a couple of reasons. Some people compete with these bows and need a well-tunied bow to shoot below 300fps to meet rule requirements. /another reason is to make it easier for young, old, sick people to be able to cock the bow easier. Some people like to put a lot of arrows downrange, again an issue to make the bow cock easier. Have not really seen any reviews as to whether the lower-weight limbs last longer or not. More inclined to think not, just 110 lb is designed to be easier to cock and deliver slower but very accurate speed and shot.

They also make the crossbow for hunters and speed freaks. The 135lb limbs are for people that benefit from fast accurate shoots. The only drawback is that they are more difficult to cock.

Pick the one that meets your needs and keep the bow tuned. To much work, to many things to go wrong when detuning these crossbows and no proven benefits.