Front discs interchangeable?

ST1100Y

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My goodness, it looks like today is my Lucky Day !!
Truedisk.net
Dunno... by the time the ST front rotors show remarkable grooves and ridges (its the RH side that goes first), their pretty much down to the wear-limit anyway... doubt there is much metal left for safely cross-hatch milling them true/smooth again...
 
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After I have my disks "touched-up" this winter, I'll report back the machinist's estimate on how much material he shaved off to true-up the disks.
 

Uncle Phil

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After I have my disks "touched-up" this winter, I'll report back the machinist's estimate on how much material he shaved off to true-up the disks.
That would be good to know and how many miles the disks had on them up this point. That would give me some relative idea - knowing driving styles and brake usage makes a difference.
 
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Well, to answer my own question, I fitted the R/H disc on the left side over two months ago. I told myself it was only temporary but last week and 2000 miles later it was still on with no issues. I have just changed it as I noticed it had become slightly warped. Whether this was due to it being on the wrong side or me being a bit overenthusiastic pushing the pistons back to change the pads, I cant say.....
 
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Late to the party here - but the directionality (is that a word??) may be related to how the discs work in the rain. Uncle Soichiro may have figured out a pattern which works best when turning one way and not so well when turning the other.

If that is correct, what might happen is that the torque produced under braking loads by the right disc may differ from that produced by the left. Having said that - I doubt that it is a major issue. Lots and lots of bikes how only one disc from the factory and they do just fine, so a slight difference between one disc and the other is not likely to cause a major headache IMHO.

Pete
 
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what might happen is that the torque produced under braking loads by the right disc may differ from that produced by the left. Having said that - I doubt that it is a major issue. Lots and lots of bikes how only one disc from the factory and they do just fine, so a slight difference between one disc and the other is not likely to cause a major headache IMHO.
I think this thread went off on two different sub-topics. The first discussed only the stresses on the brake rotor metal itself, the second involved the balance between the forces on the left and right rotor. As many have said, some smaller bikes have only one rotor, so there is no need to be concerned about differences in forces on both sides of the wheel centerline.

The original topic regarding the direction of the 'swirls' on the rotor had to do with the direction of the braking forces relative to the swirls. If we think of the swirls as springs, in the correct orientation the braking forces would compress the spring, in the opposite orientation the forces would extend the spring. Given that the spring 'rate' of the swirls is very high and they don't move much if at all under braking forces, its probably nothing more than a theoretical discussion. However, many of us came to the conclusion that we would not like to find out the hard way that there was enough difference between the two orientations that the brake rotor metal had weakened somehow under repeated braking loads over time.
 
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