Why Fishing Rods Get Expensive: Carbon Modulus, Tonnage, Strain Rate

In this article, we’ll be breaking down the factors that differentiate high-end rods from cheaper rods. We’ll talk about carbon modulus, strain rate, tonnage, IM rating, and how all these go into determining the quality of a rod. In the end, it comes down to an angler’s preference, but hopefully this helps in breaking down sensitivity, strength, weight, and other specifications that one might look at before purchasing a rod.

After the first couple hours of researching this topic, it became very clear that I wouldn’t be able to cover everything I wanted to in one article. It turns out the components that go into a rod are much more sophisticated and complicated than I originally thought. For that reason, this article will be primarily focused on rod blanks.

Why We’re talking About Rod Quality and Prices

Back when I first got into fishing, I remember talking about the hobby with friends, explaining how it’s such an inexpensive hobby with such great returns. It’s super accessible, you can catch your food, and if you’re all about catch and release, it’s food for the soul.

Most anglers who have fished for more than a few years will argue a different perspective. A cheap Walmart or Big 5 set-up might have been perfect for them a couple years ago, but now they’re too sophisticated for such a set-up and the difference in quality is bluntly noticeable. I’ve started branching out into the more “high-end” side of things and I’ve found myself relating to the anglers that so called, “graduate” from prior gear.

I’ve been in the market for a new rod for a style of fishing that’s a little different than what I’m used to. Naturally, I did some searching via, amazon.com, basspro.com, tackledirect.com, and a few company-specific searches. After finding three rods that I was genuinely interested in buying, I hit my fishing buddy up and asked what he thought. We ended up disagreeing on a couple of things which lead to me doing some research and in turn, writing this article.

Debate: High End Fishing Rods vs Cheaper Fishing Rods

Our main argument was triggered by two rods having nearly identical specs in length, action, power, lure rating, line weight rating, etc., but vastly different prices. One was in the low $100s range while the other was edging past $300. Long story short, I needed to do more research.

What Goes Into a Fishing Rod?

• Rod Blank – The foundation of a rod. Picture a cue stick for billiards, but extremely light.
• Scrim – A mesh that lines the blank and provides resilience so it can flex without breaking.
• Resin – In simplest terms, it’s the glue that holds the scrim and blank together.
• Guides – Commonly referred to as “eyelets”. These help to evenly distribute tension.
• Grip/Handle – Allows for comfortable hand placement at the butt of your rod.
• And Many More Little Details

I’ve always believed that if a rod feels right in your hands, and responds well in terms of sensitivity, action, and over all strength in fighting, your rod is perfect for you and whatever style of fishing you’re using it for. After doing all the research, I still stick with that statement, but I do have some more perspective on the topic. As mentioned earlier, let’s get into rod blanks. We’ll be speaking strictly about carbon fiber (graphite rods) today.

Below are some common terms you might come across when researching the topic:

• Carbon Modulus and Tonnage
• IM Rating
• Strain Rate

Don’t ask me why, but for whatever reason, there appears to be a whole lot of misinformation on this topic. For that reason, I’m going to define and describe each term separately.

Carbon Modulus and Tonnage

In respect to graphite rods, modulus is directly correlated to the stiffness of a rod. Modulus also correlates to lightness (or weight) of a rod. To break it down very clearly, modulus and tonnage supposedly measure the same thing. They measure the rating of the carbon fiber that is used to make a rod blank. So, as the modulus increases (the number gets larger), the stiffness increases per weight of the rod.

Plain and simple: a rod with higher modulus will require less material to reach the same stiffness as a rod with lower modulus. This results in a high performing rod that weighs less than its competition (1).

The main concern with higher modulus (or higher tonnage) is that as you increase this rating, the rod becomes thinner and lighter, and theoretically, it becomes more “brittle”. This is because higher modulus rods require less material than lower modulus rods to reach the same stiffness. Depending on the quality of the manufacturer, newer technology has allowed for extreme durability even within these high modulus rod blanks. The risk in these high modulus rods is more in the quality of the manufacturer. If they aren’t able top get the strain rate up high enough, you may be getting ripped off.

This is part of the reason some rods are more expensive than others. When you start getting into higher modulus and high strain rate, you end up with a very appealing, light weight, high performing rod… And it costs more $.

Gary Loomis on Modulus and Stiffness:

Loomis said this about stiffness, “Stiffness also equates to responsiveness – that is, the rod’s ability to store and release energy. The higher the modulus, the faster and more consistent a rod is able to store and release its energy, which enables an angler to cast farther and more accurately” (2).

I like the way Loomis worded his explanation. I think it sums up one’s thought process when comparing (in their hands) a high-quality rod vs a low-quality rod. Specifically, I thought the terms, “responsiveness” and “consistency” were very accurate.

You’ll see ratings such as 24 ton, 30 ton, 36 ton, and so on. You’ll also see ratings in million modulus as follows: 33 million modulus, 36 million modulus, 40 million modulus, and so on. Even more confusing, you’ll see ratings in IM like the following: IM6, IM7, IM8… These ratings are what have confused the heck out of anglers ever since graphite rods came into existence.

IM Rating

I think IM ratings are where everything derailed. The reason for this is that there is NO true universal standard for IM. From my research on the topic, IM ratings actually came from a manufacturer who was testing different rod blank consistency and on their 6th attempt, they called it good (1). From then to now, the meaning of IM6 and so on has sort of “evolved”.

You might be wondering, “well why is IM rating even used then?”.

I found a quote that (I thought) made a lot of sense as to why it’s still used.

“Generally speaking, a prestige German company such as BALZER uses IM rating not to confuse its customers, but because traditionally they’ve always done it this way and they don’t want to change. In their books, IM6 is 24Ton carbon, IM7 is 30Ton, IM8 is 36Ton and IM12 is 40Ton or 50-60Ton (depending on the range, and if they use nano-technology or not)” (1).

An Attempt to Convert IM to Tonnage.

It appears that IM ratings, tonnage, and million modulus attempt to measure the same thing but rod manufacturers do a terrible job of correlating each to the other. As carbon modulus increases and strain rate remain acceptably high, the assumed price of the rod will go up. If we use Gary Loomis’s explanation in combination with what the German company, BALZER goes by, a probable conversion of IM to million modulus to tonnage is as follows:

IM6 = 36 million modulus = 24 ton
IM7 = 40 million modulus = 30 ton
IM8 = 44 million modulus = 36 ton

Strain Rate

From what I’ve learned about rod quality and how these factors are related to one another, it appears strain rate and carbon modulus are very closely related. Strain rate is defined by Gary Loomis as the “measured strength of the material” (2). He then goes on to say, “While modulus is reported in millions, strain rate is reported in thousands. An acceptable strain rate for a fishing rod is 680,000 or higher. A graphite rod made from IM6 Hercules Fibers will have a modulus of 36 million and a strain rate of 750,000.” (2).

My understanding of strain rate (also known as tensile rating) is that it is determined via a combination of the carbon fiber used, plus the scrims, plus the resin that is used. All that, along with the execution of the manufacturing process play a role in the strain rate as well as the overall quality of the product.

Conclusion

While I mainly focused on carbon modulus and strain rate in this article, there are other factors that affect rod price. I simply can’t cover everything there is to know about a fishing rod in one article, but here are a few examples.

Rod handle types and quality can affect the price by more than you might think as you get into the higher end fishing rods. Similarly, quality and quantity of guides (eyelets) can affect price and performance (will write an article on this soon). Custom and different material rod tips can also factor in.

The list certainly goes on so don’t rip me to pieces for not mentioning all the little things that make up a rod, but this should provide a solid foundation.

Recommendations:

While knowing the specs is helpful, nothing beats feeling a rod and knowing it’s right for you. Along with that, your target and style is essential to determining the right rod for you. To that notion, Here are the set-ups that I recommend for surf fishing.

I hope this helps clear up any confusion you guys might have had regarding rod blanks and specifically tonnage, IM ratings, million modulus ratings and even strain rating. As always, let me know if you have any questions or you’re confused about something. Thanks for reading and tight lines!

References:

1.) https://kistlerrods.com/blogs/kistler-news/gary-loomis-talks-about-rod-breakage

2.) https://adoretackle.com/blog/how-to-select-the-perfect-fishing-rod/