Rod questions.. IM6, IM7, or IM8

[Dylan33]

This may be a dumb question, but i've never paid any attention to what my rod is made of. I'm looking to get a new spinning combo before summer. What are the benefits of a IM8, versus a IM7 or IM6? Does it really make that big of a difference? Thanks for any and all input.

[OnAFly]

These are terms given by companies to classify the stiffness of the materials used to make the rod. An IM6 rod uses material that is less stiff than an IM7 rod and again for an IM8 rod.

A rod with high stiffness is more brittle than a rod with lower stiffness. This means that small irregularities in the surface of the rod (scratches, cracks, cuts) have a greater effect on the strength of the rod. Basically, rods that are very stiff can break more easily than a rod that is less stiff.

Rods with high stiffness are generally more sensitive and a rod with low stiffness. If you've ever used a fiberglass rod compared to a carbon fiber rod, this is the difference between high stiffness and low stiffness.

[Dylan33]

So a more expensive IM8 is more prone to scratching, cracking and breaking than a less expensive IM6, but the IM8 is more sensitive? So, for a weekend, non tournament, recreational angler such as myself it really shouldn't matter all that much. I'd be afraid of breaking an expensive IM8 rod, and missing a few fish due to lack of sensitivity would be worth the money savings.

Am I accurate in assuming the IM8's would be more expensive?

[TurnUpTheFishing]

IMs are used by some companies to classify the type/quality of graphite blank used on a rod. It can be tought to compare blanks between companies as their isnt a set standard for IM ratings across the industry and not all companies use IM ratings. Example, one company may call a blank IM7 while another will call it an IM8. St. Croix uses a different labeling system (sc II, scIII, etc.). Also, some just label the modulus numbers, generally I think numbers around 35 million modulus is probably equivalent to IM6 and 80 million on up is like an IM8 on up.

The better graphite blanks are generally lighter, stiffer, and yes more brittle. As long as you take care of your gear you should be fine even with a high quality rod. Id say get the best rod you can afford. Also, most high end rods have pretty nice warranties to back them up.

[OnAFly]

My post applies only to the material used to make the rods. How the rods are designed is a different story. You can have a well design IM6 rod that is more sensitive than an poorly designed IM8.

I wouldn't worry so much about all these labels companies put onto their products. Find a rod that you like and you can afford and go for it. Like TUPT said, not all companies use the same scale for determining what an IM6/7/8 or whatever they call it is.

As for the durability part. The idea behind stiffer materials is that the blanks can be made thinner to reduce weight and improve sensitivity. Since the cross section of the blank was reduced, but the deflection caused by a given force was also reduced, you will have a higher stress in side the blank. These higher stresses coupled with a flaw in the fibers (a scratch/cut or whatever you have) can cause the blank to have a higher chance at failure than a blank with lower stresses (lower modulus).

Any blank can fail when damaged, it simply takes less damage to make a high modulus blank fail than a low modulus blank.

[Dylan33]

Ok. that is some great info guys. Like I said, I've never really paid attention to that kind of thing, but then I saw people on this forum that say stuff like "That rod is an IM7, no way i'd ever use something of that low quality" and stuff like that. There seems to be a lot of mention of it, so I wasn't sure if I was missing something. Sounds like I should just keep doing what I have in the past...find something I can afford and that feels good to me and then get out and catch some fish! Thanks again for the input

[JohnMickish]

This should answer all of the rod questions out there. This is not me, I got it from a different source but it applies here. Written by the senior rod manufacturing engineer at St. Croix.

Guys, I thought I could shed some light on the modulus thing for you.

First of all don't get caught up in the numbers. Most of the marketing you see these days is misinforming and they use those high numbers just to get you interested. In fact, those higher modulus fibers.....say 50 and up cannot be used in 100 percent of a rod blank. They can be used in the lower section in conjunction with a lower modulus material. We do this with our SCVI material, but only use it to stiffen the butt portion creating backbone in a rod. I, at one time built a blank here at St. Croix using 63MSI material in 100% of the blank. It blew up in my face big time........shattered in several pieces with very little stress applied. Here's the reason for this. As fibers are produced, they are sujected to very high temperatures in an oven line. As they pass through different stages, the properties change creating different fibers for certain applications. As these fibers are heated they become stiffer, but also become more brittle due to the tensile strength getting lower. At some point the fiber will graphitize and become what we call graphite.........way too brittle to use in a fishing rod. Carbon fiber is what we all use and typically use 30 to 45MSI materials in our blanks. For these reasons, we do not advertise our modulus ratings as they really don't factor in much.

Don't get too wrapped up in the IM ratings as well and here's why. I have a fiber book in the lab here and it gives me details on common fibers for our industry. IM7 for example has about 20 differents fibers that are listed. All of them are different in one way or another.

In choosing a rod, place your focus on other things like reputation, quality and consistency as it's truely the manufacturing that sets one company apart from another. Technologies in tooling such as our IPC is another feature to look at. Take our factory tour on our HSOforum and you can get a quick snapshot of our factory and some of our advancements.

[PerchJerker]

Great info mnfishinguy

I was going to post the same thing several others have said --- go with a rod that feels good in your hand and fits your budget. Don't get hung up on the numbers and don't think that bigger numbers mean higher quality rods.

It's a spinal tap thing ..... these go to 11.

[JohnMickish]

Yes, you can't believe everyones numbers, but reputations don't lie.

[Nick Kuhn]

Great info mnfishinguy

I was going to post the same thing several others have said --- go with a rod that feels good in your hand and fits your budget. Don't get hung up on the numbers and don't think that bigger numbers mean higher quality rods.

It's a spinal tap thing ..... these go to 11.

For $1000 I'll build you one that goes to 12

[laker1]

Old topic but very informative. Time to bump up and maybe new info from somebody?