Is that picture showing a disc thickness of 4mm? It's off an ebay ad for an unused disc but minimum thickness for the disc is 4mm so already seems to be on the limit? Thanks
I'd make that 4.075mm. Beware some chinese discs may have a different minimum thickness so as new but not per OE item.
4.075mm would still be really near the minimum limit, wouldn't it? It's supposed to be an unused set of OE Brembo discs, just seems odd to include a picture which seems to be showing they are on the minimum limit. I think you are supposed to take several readings and use the lowest one, but these seem to be worthless if already on such a low reading. Tried calling and was assured they were completely unused, mentioned the picture and thickness but not heard back. Cheers
These might be OEM fitment for the Street Triple R or Daytona which had the lighter disc rotors which were only 4mm thick when new. It’s possible these will bolt onto some of the later WC range, but without the matching callipers probably something that’s not recommended.
Do you think they might be 4.75mm, I can't work out what the second scale is? that would make more sense if they are unused.
No. It's a few years since I used old world verniers as all mine have been digital for as far back as I care to remember. If you look at the four graduations the corresponding line is only just out of alignment ( assuming negligible parallax) so the answer is a smidge over 4 and not nearly 5. I'd misread the top scale with them being grouped in 2's so I'd say it was 4.015 mm. Old verniers were always a little confusing and as the eyes get older become more of an eye test device than a measuring instrument.
Don't know if you can make any sense of my photo for explanation? You need a bit more of the top most scale for full detail but the difference is miniscule, so it's 4 + 0 + .14 and a bit so about 4.015
I read your caliper and gather 4.06mm...at least that is what reads to me or 4.04mm depends how the angle...
Looking again with a more sober head ..... I think I have sussed it although it is confusing as you said. Is the caliper Metric AND Imperial. 4.04mm reads about right on the bottom scales which equates to 159 thou on the top scales So this, if brand new, is a 4mm thick disc within a manufacturing tolerance If you are not looking for a 4.mm disc due to model or age etc then I'd just walk away. Some discs thicknesses vary with manufacturer and anything with up to say 5.5mm is quite possible within the same set up.
Thanks everyone. I was just considering replacing the Sunstars on my Thruxton S with Thruxton R floating discs as they are a straight swap. This set were advertised as unused on ebay. I think the bottom line is that disc is just a tiny smidgeon over 4mm, and the minimum thickness it is stamped with is 4mm, so I don't think they would be a good buy, there should surely be a bit more meat than that on them, especially as advertised as unused. They might be technically within tolerance, but literally only just. I think I will leave them, I'm a worrier so would be constantly checking them and thinking I'd made a bad decision. Great responses all, cheers.
@TonyG you got me and so out of curiosity I've just been and measured my Brembo discs which are on a late 2018 765rs. Using a micrometer not vernier (variable as we knew them ) caliper so as to avoid any wear step, they measure 4.46mm. They are stamped 4.0mm min. thk. If the ones advertised truly are unused then I can only presume in conclusion that they are factory rejects ........ unless someone has tried to refurbish them to sell on "as new" Be careful swapping about and ensure the offset remains the same. My Sunstar 675 discs have a different offset to my Brembo 765 ones.
Thanks again, Swapping the Sunstars for the Brembos has been done quite a lot on Thruxton S and T120s, the Thruxton R discs are a straight swap. Your measurement has sealed it, that's the sort of extra thickness I would expect so won't be buying these.
