I am looking for a new rod right now, What is the difference between IM6, IM7, and IM8?  I see many different rods with those numbers.

Andy

if im not mistaken it is the number of layers of graphite in the rod and more layers equals more sensitivity and more durability

for example IM8 means 8 layers of graphite and is more sensitive than IM 6 or 7

The metric used for evaluating graphite blanks is "Tensile Modulus", which is calibrated in millions.

"LM" stands for "Low Modulus", "IM" stands for "Intermediate Modulus" and "HM" stands for "High-Modulus".

Though it varies somewhat among manufacturers, these are ballpark equivalencies:

IM-6 = 40-million modulus

IM-7 = 41-million modulus

IM-8 = 42 to 45-million modulus.

Any blank rated over 45-million modulus is "High Modulus" or "HM". Most anglers tout the advantages of "high modulus" graphite

but there is much to be said for "intermediate modulus". As a matter of fact, many experts hold that ultra-high modulus is overkill,

that "intermediate modulus" is the sweet-spot (I agree).

Roger

I agree also it gets brittle past 7 .And graphite /composites are really durable but still have enough sensitivity for wormin and jiggin especially with braided lines.With the new superlines and sharp hooks now days you really dont need anything more then im 6 IMO

Here take a look at this. This comes from a chart put together by the folks at Hexcel (http://www.advancedcomposites.com/technology.htm)

The number on the far right is the modulus of the fiber, and the number in the middle is the elongation to failure or stretch.

Hexcel IM4 600 40

Hexcel IM6 760 40

Hexcel IM7 780 40

Hexcel IM8 790 44

Hexcel IM9 920 42

The fact is that the difference between IM6 and IM7 is nothing in terms of modulus, and compared to IM8 it's only slightly higher. Look at that IM9 it actually has a lower modulus than IM8... Now, many companies are using fibers with a much higher modulus, like 57 and even higher, however these fibers don't necessarily use the IM ratings. So, whenever you see a fiber with an IM rating...Buyer Beware! The Higher The IM Rating, Does not necessarily mean the higher the modules

Anglers have been sucked into the marketing hype that leads them to believe that the higher the IM rating, the lighter and more sensetive the material, which is not always the case.

Be warned that there is A LOT more to graphite blank construction, performance, quality, sensetivity, weight etc... than just what modulus the fiber is. There are lots of other variables like flag patterns, and wall thickness, and resin systems, and mandrel design....It's all about the talent of the blank designer, and what he is able to do in terms of the sum of those variables...not just the modulus!

Tight Lines All!!!