GS550 front discs .. thickness?

[OzJavelin]

Help?! I seem to have too different front discs on my '79 (EN?) GS550. One disc is marked with minimum thickness of 4.5mm and the other 6.0mm min thickness. The thinner disc has 2" contact area, while the thicker disc has less on the "inside" diameter. Both a solid without vents.

Which is the CORRECT disc for this bike? I'm thinking the thinner disc is correct as it allows the whole disc pad to sit on the surface, while the other disc is fouling the pad on the inside?

Can any other '78/'79 GS550 owners with twin front discs provide me with their disc thickness?

Thanks,
Rod

[sharpy]

They look the same style? One might be a "copy"

[hampshirehog]

If I understand your description properly, then if you've got round brake pads you should have the wider disc, if you've got the more rectangular type, with the litte 'ears', it's the thinner disc.

[Rover]

I seem to recall that rear discs are thicker than front.Could this be a rear disc someone put on the front?Is that even possible? Just brainstorming with you.

[OzJavelin]

I seem to recall that rear discs are thicker than front.Could this be a rear disc someone put on the front?Is that even possible? Just brainstorming with you.

That's my suspicion too. It looks a LOT like the rear disc on the same bike?
I have the round disc pads at the front which seem to foul on this thicker disc because the machined surface doesn't go all the way to the inner edge - the edge of the pad is rubbing on a raised "unmachined" surface ..