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1984 FJ11 Brake Rotors

Started by Sparky84, September 25, 2017, 04:15:06 AM

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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
1984 FJ1100
1979 Kawasaki Z1300
1972 Honda CB750/4 K2

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. 
1985 FJ1100 x2 (1 sold)
2009 TDM 900
1980 Kawasaki Z1R Mk11 (sold and still regretting it)
1979 Kawasaki Z650 (sold)
1985 Suzuki GSXR 400 x2 (next project)
2001 KTM 520 exc (sold)
2004 GasGas Ec300
1981 Honda CB 900 F (sold)
1989 Kawasaki GPX 600 Adventure

Sparky84

Quote from: oldktmdude on September 25, 2017, 05:20:17 AM
 when I still had the misfortune of having standard rotors and callipers.
That's a bit harsh Pete  :dash2:
I'm a bit hurt now  :sorry:

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



1984 FJ1100
1979 Kawasaki Z1300
1972 Honda CB750/4 K2

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.  :good2:
1985 FJ1100 x2 (1 sold)
2009 TDM 900
1980 Kawasaki Z1R Mk11 (sold and still regretting it)
1979 Kawasaki Z650 (sold)
1985 Suzuki GSXR 400 x2 (next project)
2001 KTM 520 exc (sold)
2004 GasGas Ec300
1981 Honda CB 900 F (sold)
1989 Kawasaki GPX 600 Adventure

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
1984 FJ1100
1979 Kawasaki Z1300
1972 Honda CB750/4 K2

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'm not the fastest FJ rider, I am 'half-fast', the fastest slow guy....

Current
2008 VFR800 RC46 Vtec
1996 VFR750 RC36/2
1990 FJ1300 (1297cc) Casper
1990 VFR750 RC36/1 Minnie
1989 FJ1200 Lazarus, the Streetfighter Project
1985 VF500F RC31 Interceptor

balky1

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


FJ 1100, 1985, sold
FJR 1300, 2009

Sparky84

Quote from: balky1 on September 25, 2017, 09:57:35 AM
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
1984 FJ1100
1979 Kawasaki Z1300
1972 Honda CB750/4 K2

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
""Past Bikes""
Suzuki Stinger 125        
Honda 350/4
Kawasaki Z1000
Suzuki GS1000
Kawasaki GPZ900R
Yamaha FJ1100 84
Yamaha FJ1100 85
1991 FJ1200
1990 FJ1200  Pinky
2006 FJR1300
1980 GS850
Z500 /4
XJR1300
"""Present Bikes""": 
  1985 FJ1100
FJ1200  94
GSX1400

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?  :scratch_one-s_head:

Cheers
Alan
1984 FJ1100
1979 Kawasaki Z1300
1972 Honda CB750/4 K2

PaulG

Quote from: Sparky84 on September 28, 2017, 06:06:18 AM

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

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.
1992 FJ1200 ABS
YouTube Channel Paul G


Sparky84

Quote from: PaulG on September 28, 2017, 09:56:35 AM]
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  :scratch_one-s_head: , I'm wondering if this is the case

Cheers Alan
1984 FJ1100
1979 Kawasaki Z1300
1972 Honda CB750/4 K2

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. :good2:
ยด85 FJ 1100

Sparky84

Quote from: wainot-Phil on September 28, 2017, 05:35:31 AM
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.

Quote from: Bezmozek on October 01, 2017, 02:10:04 PM
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. :good2:

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
1984 FJ1100
1979 Kawasaki Z1300
1972 Honda CB750/4 K2