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02.28.2018 | Categories: Archery Tips, Training

Yes, you can adjust the draw weight on certain recurve bows

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Compound bows are well known for their ability to have the draw weight adjusted. Most have a 10-pound adjustment range, but there are some that can be adjusted from 5-70 pounds.

Did you know it’s possible to adjust the weight of some recurve bows?

In an episode of “Behind the Riser,” filmed by Shrewd Archery, which follows U.S. Olympian Brady Ellison during the 2018 Lancaster Archery Classic, Ellison talks about “taking three turns out of” his Hoyt recurve bow after the first day of competition. That action changed the draw weight from 52 pounds to 47 pounds. (Ellison went on the win his second consecutive title at the Classic in the Men’s Recurve Division.)

Brady Ellison

So yes, you can change the draw weight of certain recurve bows. The only bows this will work on, however, are those Olympic recurve and Traditional recurve bows that have ILF limbs and fittings.

ILF stands for “International Limb Fitting,” which is a universal limb attachment system that allows ILF limbs and risers from various manufacturers to be mixed and matched. Several Hoyt recurve bows employ a modified ILF connection system that uses the same hardware as ILF bows, but the hardware spacing is distinctly different than ILF. This unique limb connection system is the Hoyt Formula system. Formula bows adjust in exactly the same manner as ILF bows.

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ILF limb being inserted into ILF riser.

An ILF or Hoyt Formula riser will have dovetail pockets to capture the dovetail bushings on the limbs. And they’ll also have limb bolts. The limb bolts on these risers are adjustable. Turning the limb bolts clockwise lowers the bolts closer to the riser and increases draw weight. Adjusting counterclockwise raises the bolts and decreases draw weight. Also, nearly all risers with adjustable limb bolts use some type of locking screw to keep a limb bolt in place after adjustments have been made. It is very important to unlock these screws before adjusting limb bolts, and then lock them again when adjustments are complete.

According to John Wert, who heads the TradTech division of Lancaster Archery Supply, which produces ILF and non-ILF recurve risers and limbs, the bolts on ILF recurve bows have a recommended best working range. Starting at a maximum height of 20mm (13/16 of an inch) for lowest draw weight and adjusting in to a minimum height of 15mm (5/8 of an inch), for the highest draw weight.  Those distances are measured from the underside of the limb bolt to the surface of the limb pocket beneath it.

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limb bolt12

“This is the best range for the entire sphere of ILF bows,” Wert said. “You can take some in or out farther, but then you are in a gray area that can lead to problems. If you know what to look for, you can adjust to as low as 12 mm and as high as 25 mm on some limb and riser combinations.”

The chief problem with turning in a limb bolt shorter than 15mm is the leading  edge of the limb bolt cap can start to dig into the limb surface. Back the limb bolt out more than 20mm, and the dovetail limb bushing can bind in the riser hardware– or even worse, the limb could fly out from under the bolt altogether.

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Left photo shows a limb sitting under a bolt set at 15mm, while the other is set at 20mm.

The number of turns an archer can put in or take out of a limb within that 15-20mm frame varies, according to Wert. Some screw patterns on the limb bolts are more aggressive than others, which would affect the total turns.

It’s up to each archer to figure out how many turns the limb bolt can withstand to stay within that 15-20mm gap. Likewise, the amount of weight that can be added or subtracted varies from bow to bow. It’s up to the archer to figure that out, so he or she knows how many turns are possible, and how much weight each turn gives up or puts back on. But generally, a set of limbs has an adjustment range of 8-10% of the limb’s draw weight.

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Turning a limb bolt with a hex wrench.

During the Lancaster Archery Classic, Ellison was able to reduce his draw weight by about 5 pounds by taking three turns out of his Hoyt limb bolts.

It’s important to note that equal turns must be put into/ taken out of the top and bottom limbs in order to maintain the tiller. Unequal turns will affect a bow’s tiller measurements, which can affect the bow’s tune and the way the bow sits in your hand.

Bow manufacturers vary on how they determine limb weights. Some, like TradTech archery, stamp their limbs with the low end of their weight range. So a TradTech limb rated at 50 pounds would draw at a minimum of 50 pounds at 28 inches with the limb bolts backed out to 20 mm. The weight would increase from there as the bolts are turned in and the limbs would reach a maximum weight of approximately 54 pounds.

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Other companies, like Hoyt, use the middle of the range for their limb ratings, and some rate their limbs at the top end of the adjustment range.

So all of this begs the question, “Why would I change the draw weight on my recurve?”

In the Shrewd video, Brady said he was having trouble holding his bow still at the higher draw weight. So he lowered it to gain more control. Other archers might find more control by increasing the draw weight.

Another reason to adjust draw weight might be to get an arrow to tune better. If the tune is close at a set draw weight, changing the weight just a little could be all that’s needed to get perfect flight.

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