anyone know what thread size the alternator nut is? i would like to replace mine with the pulleys but i don't want to pay $99 for the SR Motorsports one.

 

I believe it is a 17mm...

 

i dont mean what size wrench will i need. i need to know the thread size.

 

Did you figure it out as I wanna change mine .

 

Shifty Which nut, the adjustment lock nut or lower nut to secure the alternator .

 

If nobody answers you can always just remove the nut and venture into home depot. Take the nut and try it on every bolt that looks like it may fit. They usually even have a thing set up with every bolt pointing at you so you can do this. Make sure the nut goes down past the tip of the bolt and then you can be sure its the right thread and pitch. That is... only if nobody responds here.

 

@fastfreddie61 its the nut holding the alternator pulley on the big beefy one.
@xexok thanks for the suggestion but 2 small issues with that in in the UK and we don't have home depot,s our equivelant is pretty finish also if I take the nut of how do I drive to the store lol

For stuff like this unfortunatly I have to rely on internet stores.

 

Ah I didn't see where you were from. I figured maybe someone could drive you up to the store, but my suggestion was more of a last option anyway. Seems like any post about thread pitch never gets answered on this forum, I can't find it searching anyway.

 

Thanks anyway might have the size though a guy from the Mazda rotary club seemed pretty clued up so il see where that gets me and if its right il post the size here.

 

Shifty, good stuff, I searched and asked around, but to no avail . Sorry mate.

 

Old thread so for the sake of archive: it's an M17x1.5 metric nut. Be sure not to use a to height one since the thread is not that long.

 

Seems like an odd size, but after swapping out the nut on mine I can confirm that this is correct. It’s also called a “short flanged nut” as compared to just a plain type.

 

Anyone knows the alternator shaft diameter ?
I am thinking to use free run/ clutch pulley.

 

Its not a flat shaft if i recall correctly. its tapered...

I do can tell you that the alternator is controlled by the Mazda MCU and for example is disabled if the the engine almost stalls.
(in case you consider changing it for another alternator).

Why would you do that anyway?

 

I did notice it its a taper. and I already know about ecu control over current control of alternator.
However, thats for load vs. rpm. What I am going to do it for physic law of mass vs. rpm.
rotor has a mass which always rotate by belt in case of solid pulley like rx8 or any 70's design.
I would prefer OAD ( overload alternator decoupler) for damping properties over simple
OAP (overrun alternator decoupler).
Imagine engine rev 9000 rpm suddenly you drop it to 1000, the engine mass would be balance over compression and...
BUT the alternator even in case of control via ecu want to rotate, with decoupler it would spin free till it drop its rpm.
I know pulley system of rx8 is tensioner free, still consider it better way over lightened pulleys.
Regarding to changing alternator as far I seek it there no other compatible alt on market expect rx7-FD !?

 

I don’t really see an advantage to an OAD relative to competition use or people paying the extra cost to have it on their street car. The OAP on a tensioner system makes sense though:

 

You can see it in clip since it has spring load tensioner. It would still happen in case of solid tensioner too, however, it wont be visible as all the force goes to alt bearing and belt it self.
What I can see is money saving of Mazda, Fair enough, some of this alt are over 15 years now with any issue,

 

I picked a alternator locally on eBay for tenner as spare.
It is not tapper and diameter is 17.0mm ( 16.8 ~ 16.6)
17*1.5 thread size is common as I can recall my memory the Valeo's and old Bouch's are same. Problem is with length rotor tho.