# Ilf limb bolt adjustment



## GCook (Aug 22, 2016)

I've heard "nervous as a car in a room full of rocking chairs" but not that one.

Then again anything that makes a cat nervous is okay with me.

Sent from my SM-J710MN using Tapatalk


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## moog5050 (Oct 23, 2012)

Yes it is


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## Briar (Apr 22, 2004)

Thank you. I just dont want anymore expensive lessons if i can help it


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## Jim Casto Jr (Aug 20, 2002)

You can tighten or loosen ILF limbs throughout their range, provided you *don't foul* the dovetail bushing in the dovetail slot.


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## Brian N (Aug 14, 2014)

The fiberglass on my old PSE razorback XL upper limb splintered, just a poor quality glass/resin is my guess. Nothing to do with how it fit into the pocket, or bolts. Did the limb splinter, delaminate, or something else?


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## Briar (Apr 22, 2004)

It delaminated. I was told it was from riser contact....but that makes no sense to me.


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## moog5050 (Oct 23, 2012)

I have shot all my ilf rigs snugged down unless I want slightly negative tiller and the top bolt still stays snug. No problems yet. As Jim mentioned, don't want any binding but they shouldn't.


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## Hank D Thoreau (Dec 9, 2008)

I think trad shooters are the only ones that bolt ILF risers all the way down. When I was shooting FITA (where ILF came from) we were advised not to. The connection is not designed like a bolt down bow. I back off at least a half turn from full, but usually shoot more middle to out where the bow is most stable. The limb bolts are not intended to be weight adjustments. They are for adjusting tiller or making small changes to zero in tune. It sounds like folks are getting away with it but, is it really worth the risk when all you have to do is back out a half turn? I did a bow test once with the limb bolts all the way down and it left a nice scoring in my clear coat. I did not even shoot the bow, I just made a draw force curve. I can imagine what would have happened over time if I was shooting it.


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## Viper1 (Aug 21, 2003)

B - 

Depends on riser length and draw length. 
In most cases, it's not only "OK", it will give the most performance from the rig.
However, if you have a long draw length and a short riser, you can bring the stack or stress points on too soon. 

"Limb binding" is usually due to a flaw in riser and/or limb design. Some risers, include some very popular ones, have a very small window of allowable adjustment. 

After a while, limb bolt adjustment becomes just a tuning parameter. 

Btw - the limb that delaminated was defective or abused. 

Viper1 out.


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## Briar (Apr 22, 2004)

Thanks a lot fellas. I appreciate all the responses


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## Viper1 (Aug 21, 2003)

B - 

One other minor point...

Unless there's a severe mismatch between the limbs and riser, "snugging down" a limb bolt, means going against the stop built into bolt or riser, and not the limb. Just sayin'

Viper1 out.


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## Hank D Thoreau (Dec 9, 2008)

Just as food for thought on ILF:

Because we are using screws there is an infinite number of possible limb bolt settings. Of this infinity of settings, only one has the limb bolts all the way down. 

So if this unique setting is the best, why do we need adjustable limb bolts? We should be shooting bolt down bows. But yet, the best in the world are shooting ILF.

So did the engineers design the bow to optimize performance in this one unique position, or did they optimize it for the infinity of positions that are not all the way down?

There is a material difference between these two states, all the way down, and everywhere else. The design requirements and constraints change once you screw the limb bolts all the way down.

Optimizing the design of a loosely mounted limb is different than a rigidly mounted limb.


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## Briar (Apr 22, 2004)

Viper1 said:


> B -
> 
> One other minor point...
> 
> ...


Can someone show a photo of this so i understand? I had the correct length brass bushings, but as i am understanding, the washer on the bolt on the riser should be snugged on the riser, not the limb per say? I was using a tribe halo riser if that helps.


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## Viper1 (Aug 21, 2003)

Steve - 
Not exactly...



> "Because we are using screws there is an infinite number of possible limb bolt settings. Of this infinity of settings, only one has the limb bolts all the way down. "


Not really, a 1 degree turn isn't going to make a licks bit of difference, most people (elite shooters excluded) do well to 1/4 turns as a minimum. 


> "So if this unique setting is the best, why do we need adjustable limb bolts? We should be shooting bolt down bows. But yet, the best in the world are shooting ILF."


Because it doesn't allow for tiller changes, since not all limbs are created equal and neither are all shooters.
1. Notice I said "After a while, limb bolt adjustment becomes just a tuning parameter." 
2. Plenty of newer Olympic shooters use the limb bolt adjustments when increasing draw weights. Making gradual increments is usually better than 4# 0r 5# jumps. 



> "So did the engineers design the bow to optimize performance in this one unique position, or did they optimize it for the infinity of positions that are not all the way down?"


The "designers" can't break the rules of Physics. The greater the arc to which the limbs are bent the more potential energy is stored. However that may not provide the best tune or even be possible (practical) for a long draw shooter. It's why a knuckle dragger can successfully shoot a 62" ILF rig. 



> "There is a material difference between these two states, all the way down, and everywhere else.


" 
You're forgetting "all the way up" for bows with built in stops in that direction. 



> "The design requirements and constraints change once you screw the limb bolts all the way down."


Not really, it's just another point on the spectrum. 

Given a choice, I would always prefer my limb bolts to be full in for best performance, but tuning requirements and yes, strength may contraindicate that. 
As I get older, I find my limbs bolts are farther out, and my arrows have a weaker spine.

Viper1 out.


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## Viper1 (Aug 21, 2003)

B - 

Just look at the bolt.
Most have a shoulder that butts against the riser.

Can't speak for every riser out there, though. 

Viper1 out.


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## moog5050 (Oct 23, 2012)

Hank

I am just a hunter but like ilf because I can try different limbs and adjust tiller when needed. I suppose if I have a slightly week arrow, I can let a few lbs off too. But otherwise I keep them snug for most preload, best performance and they tend to be quieter this way. I agree that the flexibility is likely used more by target shooters.


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## Hank D Thoreau (Dec 9, 2008)

Viper, 

I should clarify that I am not speaking of the laws of physics or the impact of 1 degree of angle. I am referring to the potential for damage to the limbs, which is also an aspect of performance when you are looking at it from a engineering perspective. 

My point is whether the design was ever intended to accommodate limbs being fully clamped down. ILF has a loosely mounted limb attachment where the limb is held in place by the tension of the string and the flex of the limbs. Did the design account for the stresses imposed by a rigidly mounted limb? These are two distinctly different design scenarios. There are added requirements to deal with when you clamp the limb down in a rigid configuration.

I was always told that tightening the limb bolts all the way down could damage the limbs. As such, I avoid doing so. I thought that this came from manufacturer recommendations. It was awhile ago so I am fuzzy about the source of the information. There are a lot of unsubstantiated claims in the world. Maybe this is one of them. Since the extra weight is pretty much meaningless, I don't see the advantage of taking the risk. As such I error on the side of caution and go with not clamping my limb bolts all the way down. There is no question that the limbs were designed to be shot in that configuration.


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## Viper1 (Aug 21, 2003)

Steve -

And your reasoning doesn't hold water since on any decent production ILF riser, the bolt doesn't lock the limb, the bolt shoulder locks against the riser - even the Hoyt Excel does that. I would consider suspect any bowyer or company that allows an ILF limb to be clamped down by the bolt. But then again, there are plenty of T/Ds on the market that do just that and have been for well over a century. You can quote engineering textbooks all you like, but in the real world, it's just not an issue.

Viper1 out.


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## catman-do (Aug 17, 2014)

I have a 21" Black Bear riser that I had converted to ILF (Sam Dunham) and I'm using PSE Med Carbon Elite ILF limbs for total length of 64". Sam told me to just snug them down and then do a 1/4 turn out and then check for tiller. I keep my tiller length the same distance from the top & bottom of the riser where the limb is connected to my string. I keep a 8-3/8" brace height with me shooting 3 under. I'm also just hunter and a back yard shooter, but this ILF thing great with my Hillbilly Black Bear riser that I found in the trash. It's the best shooting bow I've ever shot. My 2 cents..


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## GEREP (May 6, 2003)

Briar said:


> Is it ok to shoot an ilf setup with the limb bolts tightened down snug?....i thought i was doing everything ok, but had a limb break and now im as paranoid as a cat on a hot stove. Thanks ron




Ron:

You got a lot of information here, some good, some bad. 

First you must define what you mean by *"tightened down snug."*









Most commercial ILF risers come with some sort of *"collar"* or *"bolt stop"* (red arrow) that insures that the limb is *NOT* snugged down tightly to the riser. The collar or bolt stop insures that the only part of the limb that rides on the limb pad is the rocker (blue arrow). There *MUST* be some space between the limb and the limb pad (yellow arrow.)

If the limb is tightened down too snug, and no space is left between the limb and the limb pad (green arrow), the ILF fitting can bind in the slot (pink circle) and it can and does cause undue stress in that area. At a minimum it can and will cause noise and damage to both the dovetail and the slot. It can also cause failure (delamination or fracture) of the limb butt area.

KPC


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## Briar (Apr 22, 2004)

Thank you kpc, thats very clear. I appreciate your photos


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## GEREP (May 6, 2003)

No problem Briar, glad they were helpful.


Just curious, what ILF riser are you using, what limbs did you have, and were you snugging them down like photo 2?



Another thing that you need to watch for is contact between the end of the limb butt and the rear limb pocket wall.











If there is binding in this area, at a minimum it will make noise and can also cause the limb butt to delaminate. 

There should only be two contact points between limb and riser. One is the rocker on the limb pad (A), and the other is the underside of the limb bolt bezel and the top of the limb butt (B).










KPC


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