# When did Hoyt change their ILF dimensions?



## limbwalker (Sep 26, 2003)

There has been a lot of discussion on this forum about ILF dimensions and fit since Hoyt decided to manufacture their "HDS" moniker and develop their paralever (PMS) system. Myself and many other archers have experienced poor fit with various ILF limbs mated to Hoyt risers. I figured it was the limbs, but recently my opinion on that changed.

While trying to fit a pair of non-Hoyt limbs (We'll call these limb "A") to my trusty Axis riser (retrofitted to accept the hard-lock ILF dovetail dowel), I noticed the distance between the Hoyt fittings and the limb "A" fittings were not matching up. The distance between the Hoyt dovetail slot and the bolt was longer than the dovetail to "U" groove in the limb, causing the limb to move laterally in the limb pocket. Basically, the limbs were unuseable in that riser for that reason. 

However, I had other limbs that worked just fine, and they weren't Hoyt limbs... I became very curious as to why.

A few weeks ago, I had access to several other risers to test those same limbs in. They fit a Hoyt Nexus the same way they fit my converted Axis - sloppy. But they fit a Bernardini and a PSE riser just fine. That made me really curious. 

I had at the same time access to several old (one VERY old) Hoyt Gold Medalist risers. Now, I understand that this, or perhaps it's TD-4 predecessor, was the "original" ILF riser, right? At least, that's where Hoyt gets the "intellectual property" from that justfied the name change to HDS, right?

Anyway, I threw Limb "A" into the GM risers, and guess what? They fit like a glove. All of them. As did all my other non-Hoyt limbs.

So what that tells me is that at some point between the GM and the Axis, the dimensions changed for the "HDS." So much for intellectual property.

The skeptic in me wants to say that this was an intentional move on the part of Hoyt. But I could be wrong and if gt were still posting here, he would most certainly proclaim me dead wrong... (along with insulting my heritage or something...  )

But maybe for the sake of being truthful, someone (perhaps even gt or his proxy Shin) could set the record straight and explain why the riser dimensions changed over the years. And I would hope we don't get a reply like "they haven't changed!" 

But I suspect we will...

For anyone who has a new Hoyt riser with the hard-lock dowel system, and an old GM riser laying around, you may want to measure yourself. My sample size was small, but enough to satisfy my curiosity. 

I believe that Samick and W&W have kept pace with the changes by extending the "legs" on their limb butts to allow for this increase in length on the Hoyt risers. The Samicks and W&W limbs I've tried fit fine. 

I guess all the limb manufacturers could indeed follow suit and extend their geometry to fit the new Hoyt geometry, but then Hoyt really would be able to claim their intellectual property has been stolen at that point...

Interesting. Very interesting indeed.

Anyone else have Hoyt riser "fit" issues?

John.


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## Sanford (Jan 26, 2009)

LW, from the Hoyt Q&A section, is the looseness not intentional? I'm reading and learning, so I'm not stating one way or the other. I would think that their misspelling of "necessary" is not intentional, though.

*When my recurve limbs are unstrung, I can easily move them back and forth. Do I have a problem ?*

» The original, patented Hoyt Dovetail system functions by self-centering the limb on the engagement surfaces of the limb itself. This means that the system will appear to be loose until the bow is strung.

Once the bow is strung, the self-centering aspect of the system takes over.

Every time the bow is shot, the limbs are forced to the precise center alignment dictated by the geometric position of the alignment dowels.

This makes shimming limbs for pocket fit unnecessary.

Note that other bow companies making an imitation Hoyt dovetail may not hold the neccessary tolerances required for optimal system function.


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## Progen (Mar 17, 2006)

Sanford said:


> ...
> Note that other bow companies making an imitation Hoyt dovetail may not hold the neccessary tolerances required for optimal system function.


Despite being a partial Hoyt user (risers only, no limbs, can't afford them  ), I'd say that's total bullcrap. What do TOLERANCES mean? Is it that difficult to machine an exact copy of something as simple as a recurve riser's limb pockets? If the engine of an F1 race car can be reverse engineered by knowing the dimensions of its fasteners, what is a limb pocket?


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## introverted (Jan 2, 2009)

Progen said:


> Despite being a partial Hoyt user (risers only, no limbs, can't afford them  ), I'd say that's total bullcrap. What do TOLERANCES mean? Is it that difficult to machine an exact copy of something as simple as a recurve riser's limb pockets? If the engine of an F1 race car can be reverse engineered by knowing the dimensions of its fasteners, what is a limb pocket?


you ever run a cnc?

it's not quite that easy


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## Sanford (Jan 26, 2009)

Progen said:


> Despite being a partial Hoyt user (risers only, no limbs, can't afford them  ), I'd say that's total bullcrap. What do TOLERANCES mean? Is it that difficult to machine an exact copy of something as simple as a recurve riser's limb pockets? If the engine of an F1 race car can be reverse engineered by knowing the dimensions of its fasteners, what is a limb pocket?


I think the copy changed for the copiers, maybe and probably intentionally, which is the topic of the thread. I read that last sentence to be Hoyt's backdoor way of saying, "don't expect universal fit with our competitor's limbs." If so, it's kind of sneaky to blame the poor QC of competitors' processes instead of stating that the tolerances changed. IOW, without claiming to have abandoned a standard, which is fine in the name of competition for marketplace, the blame for non-fit is on competitors' QC, when in fact, the standard changed in order to eliminate the competition. Kind of get two for one with that approach.


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## Borderbows (Apr 4, 2009)

well... the self centreing function works when you have the radii of both the dowel and limb bolt touching nicely.
then the limb will not rock side to side at either the dowel or limb bolt when strung up.

now if you move your limb bolt back by say 2mm, then the old limbs would secure at the dowel end and not the other, while new ones would fit, i can only imagine what the consiquences are if your limb butt "U" is longer then a competitors riser.then all the weight sits on the limb adjustment bolt!

i did start a thread a little while ago on another forum to try and allow people to measure there risers so that this kind of data can be seen... this has been a issue for a while and Gtek must have giggled when he blamed our limb fit. Good job our limbs performance is enough for our customers to keep us informed... afterall its just a limb fit.


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## ryan b. (Sep 1, 2005)

hmm.

i can sure tell on my hoyt excel.

the detent pin doesnt sit in its groove in the riser because the "U" cut outs in the limb arent deep/long enough.

Ive tried 5 sets of limbs now. none are hoyt limbs.

all limbs fit fine in spigarelli revolution and win/win exfeel. all limbs were win/win or samick.


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## SBills (Jan 14, 2004)

I just picked up a new set of 550 limbs for my wife's nexus. The old SKY limbs she was shooting fit very tight to the dovetails. The new ones snap in as easy as could be be. A very nice fit.

I would be more curious to know when Hoyt shortened their limbs? I noticed it first with a set of G3 limbs several years ago that I had to shoot a 1/2" shorter string than other mediums. Same thing withe teh 550's. The new medium Hoyt limb is about 1/4" shorter than the Sky jack medium limb.


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## Jim C (Oct 15, 2002)

The last 4 years I have shot a Helix with WINEX limbs as my indoor set up. I also have a back up with 900 Hoyts. I didn't see any difference in the fit


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## limbwalker (Sep 26, 2003)

Jim, the W&W limbs as well as my Samicks, must have adapted to the change I think... 

The legs on limbs by those two manufacturers (that I've seen) are long enough to accomodate the change in dimension. The limb butt dimensions on my Samicks are most definitely a few mm longer than my original SKY limbs. And I would suspect that Earl knew what the proper dimensions were...

Scott, did the (I assume original) SKY limbs fit the Nexus without any lateral movment? And what position is the limb bolt in? In, out or midway? 

The dovetails on all the limbs I've tried snap in just fine. The issue is whether the legs of the limb butt fully engage the bolt when the limb bolt is turned out. 

John.


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## Flint Hills Tex (Nov 3, 2008)

There has been a notice on the Alt Services Website for at least a year now stating that Hoyt changed the limb pocket geometry. When people (including me) started asking questions about this on various forums, we heard the most amazing theories as to why AS would post such "lible", as well as adamant denials that Hoyt would ever do such a thing.

I find it interesting, though, that more and more of us seem to be discovering the same thing, though the voices defending Hoyt's honor are still very prevalent.

I guess what I don't get about the whole thing is this: why doesn't Hoyt just own up to what they've done? If they've made their product better, then there is no reason why they should have to hush it up or deny the fact.

By changing the limb pocket geometry without telling customers they have done so, Hoyt has deceived them into buying a product which they believed to be universally (ILF) compatible, when in fact it isn't any more. Of course, I am aware of the fact that Hoyt _never_ claimed their HDS/ILF to be compatible with other manufacturers' limb fittings.

But that is a moot point any way, since everybody knows that ILF was introduced by Hoyt, then copied by the Asians. In fact, over here in Germany ILF is still often refered to as the "Hoyt-limb-fitting", even if you are buying a Samick or W&W limb/riser. It's not like anybody doubts the origin of ILF...


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## limbwalker (Sep 26, 2003)

> There has been a notice on the Alt Services Website for at least a year now stating that Hoyt changed the limb pocket geometry


Hmmm. Guess I missed that. Exactly what does it say? 



> though the voices defending Hoyt's honor are still very prevalent.


 Of course they are. It's the same mentality that makes the Nascar group argue whether "Ford" or "Chevy" is better, while a Dodge or Toyota is winning the race...  Hoyt and Mathews have carefully cultured a following. 

Don't think the fancy bowling shirts have nothing to do with it either... It appears that many folks are afraid to have nothing but their scores to brag about...




> since everybody knows that ILF was introduced by Hoyt


You mean Mr. Hoyt... the guy who started SKY archery, right? 

John.


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## limbwalker (Sep 26, 2003)

> There has been a notice on the Alt Services Website for at least a year now stating that Hoyt changed the limb pocket geometry


Hmmm. Guess I missed that. Exactly what does it say? 



> though the voices defending Hoyt's honor are still very prevalent.


 Of course they are. It's the same mentality that makes the Nascar group argue whether "Ford" or "Chevy" is better, while a Dodge or Toyota is winning the race...  Hoyt and Mathews have carefully cultured a following. 

Don't think the fancy bowling shirts have nothing to do with it either... It appears that many folks are afraid to have nothing but their scores to brag about...



> why doesn't Hoyt just own up to what they've done?


Not likely. The typical denials, if anything, will be prepared...



> since everybody knows that ILF was introduced by Hoyt


You mean purchased from Mr. Hoyt... the guy who started SKY archery, right? 

John.


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## greennock (Dec 13, 2007)

limbwalker said:


> Hmmm. Guess I missed that. Exactly what does it say?


I think Flint Hills Tex was referring to this disclaimer under all of their limb descriptions:

*Mix and Match Warning*​The basic principle of International fitting limbs and risers is for all items, regardless of manufacturer, to be interchangeable. However, due to the re-design of certain manufacturers products this is no longer the case.

*A particular case in point is the current range of Hoyt risers where the pivot point has now been moved back in line with the dovetail location. This pivot point on most other bows is on the leading edge of the pocket. This has resulted in some cases of poor fitting and non-alignment of limbs and in extreme cases even breakage due to the increased strain on the limbs.*


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## whiz-Oz (Jul 19, 2007)

The hint to your misfitting Axis problems may be partially contained in the conversion. The original fittings have the mounting point absolutely central in the dowel. 










The conversion dowels are offset to provide clearance. I don't know if you noticed right away (I didn't),You get a slightly longer bow when you convert it. But that's at the loss of a few mm seating of the slot into the limb bolt. 
Sorry for the crap photo (This was done without the macro lens), but you can see what I mean.











I'm not convinced that the pocket geometry HAS changed. If the hardlock dowel is proud of the pocket floor, it's going to be part of the pivot point. I have marks on the bottoms of some limbs that have been in my Axis in two positions. The dowel surface and the pocket edge. I didn't have these until I wound it right out and the limb bent until it touched the pocket edge. 

I'm tempted to polish a radius into it, but I don't care that much. There's plenty of thickness at that point on the limb.


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## whiz-Oz (Jul 19, 2007)

Whoops. You DID notice right away that the new limb conversion dowels offset the limb bolts. It's in your Axis conversion posts.


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## Vittorio (Jul 17, 2003)

greennock said:


> I think Flint Hills Tex was referring to this disclaimer under all of their limb descriptions:
> 
> *Mix and Match Warning*​The basic principle of International fitting limbs and risers is for all items, regardless of manufacturer, to be interchangeable. However, due to the re-design of certain manufacturers products this is no longer the case.
> 
> *A particular case in point is the current range of Hoyt risers where the pivot point has now been moved back in line with the dovetail location. This pivot point on most other bows is on the leading edge of the pocket. This has resulted in some cases of poor fitting and non-alignment of limbs and in extreme cases even breakage due to the increased strain on the limbs.*


I read this note on AltServices web site at that time, but frankly I did not understand its explanation . MY original guess was that as of many limbs bolts breaking in the market on new (at that time) Nexus, they were trying to explain that it was a problem related to extra stress generated by "other" limbs... Some dealers in Italy got ssimilar info from one Hoyt importer, and started telling around that, for instance, Inno limbs were not "compatible" with Nexus riser and could generate faults of the limbs bolts.
The reality was that changing the limb bolt from Steel (Matrix) to 7075 Al (Nexus) without changing the thicknesses and specifically the angles cut in the bolt area made a possible fractural point around (under) the bolt, that could be made more critical if the lever lenght under it was longer. In my guess, Hoyt probably tested their bolts under stress using Hoyt limbs only, that were fitting "less" in the bolt, while limbs from other manufacturers had a "longer" fork and were soleciting more the inner plane of the bolt. Anyhow, Hoyt sent steel bolts to users with bolts broken and after changed slightly the design of the bolts and problem disappeared.

I have already explained in another thread how the full dovetails system should work, including the so much uncknown small spring pin in the limb.
Can the ILF system be made better?
For sure, if an independent body can put toghether a real full specs of the ILF sytem, and manufacturers can rerefer to it for their design, situation will surely improve.


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## Borderbows (Apr 4, 2009)

Whiz, your a better source of info than any hoyt person Ive met... Your forthcoming for starters.

Your due a place in the Hoyt stable of paid people for your comendable efforts to set the record straight.

For what its worth, you have my respect for that.


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## whiz-Oz (Jul 19, 2007)

I'm not really a Hoyt person. I'm an archer who likes to know the truth. 
I base my decisions on what I know, what I've had experience with and what would be logical. 
I also have a lot of experienced archer friends who ask questions of and listen to.


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## SBills (Jan 14, 2004)

I think Whiz nailed it on the Axis issue. I never understood exactly the alt services warning and I think Vittorio's summary of the issue is spot on. FWIW I swapped stainless bolts into the wife's nexus for that very reason although they were the later beefier aluminum bolts.

Also @ John. No the SKY limbs fit solid, just very tight in and out and without a pronounced click of the detent pin. Viewing the two limbs side by side I could see no huge differences in ILF location to groove etc.


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## limbwalker (Sep 26, 2003)

Greennock, thanks. That is quite different than saying the limb pocket "geometry" has changed. Surely the pivot point is different since the Axis. 

Whiz, yes, I noticed that right off. You are correct. The Conversion dowels do indeed move the dovetail further from the bolt. 

But that is only where I first began to notice this. Because some of my limbs still work just fine with the converted riser, but others (including my SKY limbs) do not any longer. So it seems we have basically two dimensions of limb butts/risers out there.

Also, I attempted to fit another set of limbs to a Nexus the other day, and they were loose in the pocket. But the same set worked fine on Bernardini, PSE and the old GM risers. So that's when I became suspicious. 

Whiz, I don't know how else to explain that. The dimensions of the Hoyt risers with the hard lock dowel system are clearly different than the old GM risers. Why? 

Oh, and fwiw, I agree with Sid. While you are clearly a fan of Hoyt, you at least provide factual information and we appreciate that in this day and age...  It appears as though some folks have sipped a little too much of the Hoyt kool-aid and can no longer be objective about things... 

John.


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## massman (Jun 21, 2004)

*Limbwalker*

If the detend location on a Hoyt ILF rise ris now further from the poundage adjustment bolt, and the limb length from the detent to the tip have remained constant...does that not mean that even silghtly the bow is longer? If so then using a longer string would be needed to retain any specific brace height. What then would be the effect on the limbs performance?

IE a 68 1/4" bow with a 8/14" BH??

BEST Regards,

Tom


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## Acehero (Nov 2, 2007)

In a similar thread i mentioned that my wife once had a problem with her 23" Matrix and getting some Hoyt G3's to stay aligned. We had to wind in the limb bolts quite a way before the limbs would seat solidly. Now this bit of info may be relevant here...the original dowels had been removed and replaced with some stainless steel ones. Dont know why, it had been done by the previous owner. Both the riser and limbs were straight with no damage or twisting.


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## Flint Hills Tex (Nov 3, 2008)

whiz-Oz said:


> The hint to your misfitting Axis problems may be partially contained in the conversion. The original fittings have the mounting point absolutely central in the dowel.
> 
> 
> 
> ...


Your pics are pretty good, really. Now I actually understand what the difference is. Thanks for the illustrated explanation. 

@John, sorry for my poor description of the Alt Services notice. There is quite a difference between moving the pivot point and changing the limb pocket geometry.

Now I'm no engineer, but even if the change is only minimal (a few mm as pictured above), I would think that could radically affect lateral limb stability and stresses put on a limb.


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## Warbow (Apr 18, 2006)

Vittorio said:


> For sure, if an independent body can put toghether a real full specs of the ILF sytem, and manufacturers can rerefer to it for their design, situation will surely improve.


Indeed they could, but the industry seems to have a somewhat ambivalent attitude regarding standards, so much so that they refuse to even call them such. The Archery Trade Association's bylaws specifically *prohibit* the association from creating "standards" but only "guidelines":



> The Committee will issue voluntary guidelines to the Corporation’s Membership regarding the manufacture of archery and bowhunting equipment. The Committee will not issue standards.


I'm not sure what the paranoia over the word "standards" is, though, since standards aren't necessarily any more mandatory than "guidelines."


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## Sanford (Jan 26, 2009)

Warbow said:


> I'm not sure what the paranoia over the word "standards" is, though, since standards aren't necessarily any more mandatory than "guidelines."


I think standards imply set/mandated benchmarks of merchantability.  IOW, standards imply benchmarks for expectations of warranties. "Guidelines" work to give manufacturers more independence in this regard. If a company made risers to an industry "standard", any failure of a competitors product used on that riser could be subject to warranty by either company - namely, the company assumed to have not met the "standard". In this regard, product liability is a factor as well.


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## ryan b. (Sep 1, 2005)

the samick and win/win limbs i tried to fit to my excel are old limbs (though barely used).

old limbs and brand new riser may equal bad fit. the detent pin does not engage even with the limb bolts all the way in.

i have some new limbs coming.

I want DAS limb pads and limb hardware on all my bows


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## Borderbows (Apr 4, 2009)

hang on a tad... Whiz you could bail us out here.

If the original fitting Fixed gear were located central to the limbs, and the conversion Dovetail system is say 2mm longer... were the limbs interchangeable too, in which case the limbs designed for the dovetail system would be 2mm too long for the radii to radii fit or automatic centralisation at both the dovetail and the limb bolt?


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## whiz-Oz (Jul 19, 2007)

The limbs were totally identical. You just push the bushing out of the limb and put the dovetail ones one. In terms of movement laterally, it made no difference and when strung, it felt as solid as the original screw in fitting. (That's what I actually wanted to see, and I couldn't void the warranty on my new limbs that I wanted to shoot in the Axis.)


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## SBills (Jan 14, 2004)

SBills said:


> I would be more curious to know when Hoyt shortened their limbs? I noticed it first with a set of G3 limbs several years ago that I had to shoot a 1/2" shorter string than other mediums. Same thing withe the 550's. The new medium Hoyt limb is about 1/4" shorter than the Sky jack medium limb.


Going back to this I measured with a tape measure from the center of the dovetail to the center of the string groove along the belly on three sets of medium limbs. The 550's a set of SKY jacks and a set of W&W Innos,

The Sky and W&W both measured 21 7/8" although the W&W curve was very different.

The 550's were 21 5/8" thus giving a half inch shorter bow and needing a 1/2" shorter string. Strange.


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