What are these really for

[Kglo]

What it the engineered purpose of the grooves in friction plates?

[CASHESVALLEY]

I would think it would be for oil flow across the plates.

[k.g]

It allows for greater pressure to be placed on the steels, since there is less surface area.

[Beau 88]

I was told that the clutch basket is assembled by robot / Automated and those grooves or cutaways are used to line up the disc while assembly . 

[LovingOffroadPain]

Weight, simplicity, oil flow--wut others have posted. An ounce is a pound, as the saying goes.

[Kglo]

I only ask because I have seen them in just about every orientation from all in a line, or offset one slot on each plate forming almost a spiral effect. I always assumed this was done by someone replacing the clutch. However I just opened my 2012 crf450x up that I bought brand new from the dealer and the first 5 plates are all lined up but not the rest. I did a Google search and read through the clutch sections of several factory manuals. Just curious what they're for.

[1987CR250R]

The clutch lubricates the transmission.  If you look above the clutch there is a reservoir with a passage drilled through the case into the transmission area.  As the clutch spins it grabs oil from the sump slings it into the cup shaped reservoir on top then gravity drips fluid onto all of the gears within the transmission.  I assume the grooves are there to increase the amount of oil the clutch can throw into the transmission.

[Fat Tony]

Im just guessing here but maybe heat. Possibly same reason as drilling holes in your rotor or using a wave style. Or possibly to give a place for the debris worn off of the friction plates to go then be rinsed out by the oil. Like a tap when threading a hole. Just a couple thoughts off the top of my head.

[mec500]

The grooves give the oil somewhere to go when the clutch is engaged .it alows for faster reaction without slipping. The clutch plates are very similar to clutches in an automatic transmission where performance modifications include drilling holes in the clutch drum for faster oil release making for faster and firmer shifts. If your referring to the notches on the outside ears I not 100% positive but I always thought it was for orientation and weight reduction

Edited May 15, 2014 by mec500

[Still Bill]

I asked this last year and never got a definite answer.  One of life's great mysteries?

[gimped up]

The grooves give the oil somewhere to go when the clutch is engaged .it alows for faster reaction without slipping. The clutch plates are very similar to clutches in an automatic transmission where performance modifications include drilling holes in the clutch drum for faster oil release making for faster and firmer shifts. If your referring to the notches on the outside ears I not 100% positive but I always thought it was for orientation and weight reduction

Im just guessing here but maybe heat. Possibly same reason as drilling holes in your rotor or using a wave style. Or possibly to give a place for the debris worn off of the friction plates to go then be rinsed out by the oil. Like a tap when threading a hole. Just a couple thoughts off the top of my head.

These!

[Wild Alaskan]

i think he was asking about the groove on the outside of the disk

[The Spanky]

The grooves between the friction pads serve multiple functions. They promote oil circulation and flow through the transmission. They make it easier to disengage the clutch by preventing "vacuum suction" from causing the plates to stick together. And they also reduce drag when the clutch is disengaged by aerating the oil and thereby reducing viscosity drag between the plates..

[Kglo]

Yes the grooves on the outside edge, not on the face of the plate.

[gimped up]

Yes the grooves on the outside edge, not on the face of the plate.

Oh, they put them there, to make people start needless threads about grooves in clutch plates.

Lmbo

[Beau 88]

i think he was asking about the groove on the outside of the disk

That's what i assumed . o' well wrong again i guess ?