YPVS Brake disks... Thickness question

[JonW]

So... I was looking at brake disks today and wondered this:

- 83-85 min thickness is 4.5, 86-on minimum thickness is 4.0.

- The 86-on disks started 0.5mm thinner to start with, so have the same acceptable wear amount.

- Different calipers in 83/4, but same calipers from 85-on.

So, why cant the 85 models at the very least run their disks down to 4mm?

And... Does this mean that 83-5 disks under spec are fine for another turn on bikes post 85?

My worry is cracking as these disks do crack from the holes to the outer edge.

[midlifecrisisrd]

Ahem, cough, cough 😇

I'm assuming the discs are actually 0.5mm thicker to start with. I've never measured any

Its how they are visually that does it for me

Looks like it was a weight/cost exercise to make them thinner

If a disc is evenly worn with a nice flat surface and no cracks then good to go

The issue with the thicker disc being used down to the 4mm limit instead of 4.5 is that it will have had twice the wear/heat so more likely to crack or to be grooved/concave from pad wear

Steve

[JonW]

I reckon they must be, I have some that measure over 4.5, ie 4.7ish and LC disks are defo 5mm. Same with XV550 etc

I think it was weight, but its basically the same disk and looks to be the same steel etc.

Interesting to think about adding in the greater amount of heat cycles for the steel... hmm...