1984 FJ11 Brake Rotors

[Sparky84]

Hi All,

What is the difference between the OEM disc rotors?
Are they all the same and can the left be swapped with the right?
I have noticed the direction arrow and numbers, mine are 47A & 47B, all stamped on the outside as far as I could see.
B's are right and A's are left.
If I used a right disc and used it on the "left" and left the rotation arrow on the inside it seems to be the same but is it?

My reason is I can get only NOS right disc's.

Cheers Alan

[oldktmdude]

   Alan, my take on the difference between right and left, the directional angling of of the ventilation finning is opposite. That's my recollection from when I still had the misfortune of having standard rotors and callipers. That was quite a while ago so don't take it as a given.
   Regards, Pete.
PS. I do recall using a front rotor on the rear, from the opposite side that Yamaha recommends. I had not problems with it at all. 

[Sparky84]

 when I still had the misfortune of having standard rotors and callipers.

That's a bit harsh Pete 
I'm a bit hurt now 

I've had no problems stopping and those red light camera's do test your emergency braking out regularly.

They do look the same except for the direction arrow.

Cheers Alan

[oldktmdude]

   Alan, look at the angling of the cooling vents between the discs. Turn the right hand side around as to simulate it being mounted on the left hand side and compare the direction of the cooling fins. I think you'll find they are facing opposite directions.
    Once you have 320mm rotors, blue spots, EBC HH pads and a 14mm R1 master cylinder, the OEM brakes feel like absolute shit. Try mine in December and see what I mean. 

[Sparky84]

If I turned it around I would have reversed rotation and the cooling although I reckon the cooling fins are angled the wrong way but I'm no engineer.
I was actually thinking of not turning it around but mounting it with the outside facing in, exactly as if you just moved it from right to left with no turning

Cheers Alan

[fjbiker84]

You can buy two new aftermarket rotors for the price of one OEM and new rotors are supposedly better.  RPM has them and there are other sources.  I bought mine through a local bike shop before I knew about RPM as a source for parts. I'm hanging on the two OEM fronts in case the rear ever needs replacement.  

[aviationfred]

I have ordered brake components from this seller in the past. Take a look at these rotors.

http://www.ebay.com/itm/Front-Brake-Disc-Rotor-x2-Fit-YAMAHA-FJ-1100-1984-1985-84-85-/352138310700?fits=Model%3AFJ1100&hash=item51fd14342c:g:BwwAAOSwrFJZyM4W&vxp=mtr


Fred

[balky1]

I'd say your rotors look fine, why would you change them and change for the same ones?

[Sparky84]

I'd say your rotors look fine, why would you change them and change for the same ones?

Plenty of ridges Balky, just trying to keep the bike looking original

Cheers
Alan

[wainot-Phil]

Alan ,I think I have a set of FJ1100 Rotors hiding in my shed ,Not sure how worn they are,,If you are interested please measure your own Rotors with a set of Viner Calipers and advise how thick your Rotors are in mm,,I will then dig my FJ1100 Rotors  out and see if they are any thicker / less worn  than yours ,,that's if you are interested in them at all ,,cheers Phil

[Sparky84]

Thanks for the offer Phil,

I had a chance to buy some OEM but they were all right side ones that's why the post.
I will check thicknesses of both.
I've been also looking at the Metal Gear ones, they do look similar

Just thinking out aloud here, wouldn't all the ridges actually increase the braking surface area thus increasing braking performance? 

Cheers
Alan

[PaulG]

Just thinking out aloud here, wouldn't all the ridges actually increase the braking surface area thus increasing braking performance? 

Cheers
Alan

Theoretically that might make sense, but in reality IMHO I wouldn't think you would notice the difference.  However when you change pads you will notice less braking efficiency until they are bedded in. More so than with smoother rotors.  Also the more scoring there is - the less steel on the disc - the hotter they get - the quicker they warp.

[Sparky84]

]
Also the more scoring there is - the less steel on the disc - the hotter they get - the quicker they warp.

Maybe the sintered pads have scored the OEM discs  , I'm wondering if this is the case

Cheers Alan

[Bezmozek]

I have still OEM rotors at home, will ensure if there is any offset and let you know.
As far as I remember, offset is 0, so if you do not mind to have rotation arrow on the inside, go ahead.

[Sparky84]

measure your own Rotors with a set of Viner Calipers and advise how thick your Rotors are in mm

Hey Phil, finally got around to measuring them, 7.2 & 7.3.

I have still OEM rotors at home, will ensure if there is any offset and let you know.
As far as I remember, offset is 0, so if you do not mind to have rotation arrow on the inside, go ahead.

If that's the case No worries, as long as I fit them with the arrow the same as rotation I don't need to see it anymore.

Cheers Alan