[Closed] PSA: Please check your rotors / discs! Fail.

Happened to Stevo guiding last year on our Whiteroom holiday in the Alps 😯

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What calipers are you running.

How would one go about measuring the thickness? (Preferably with equipment I'm likely to own)

Micrometer would be best - vernier or digital calipers might be fooled by an unworn band around the outside edge.

Are you running the wrong pads?

Some Shimano rotors are "resin pads only".

If you run sintered pads....this happens.

Already said resin/organic but if they're not Shimano, could be made from any combination of materials, no standard for pads, so god knows whether they're compatible.

How would one go about measuring the thickness? (Preferably with equipment I'm likely to own)

Or cheap thickness [url= http://www.ebay.co.uk/itm/0-12mm-Portable-LCD-Digital-Thickness-Gauge-Meter-Micrometer-Tester-Tool-eml/201961684499?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20150313114020%26meid%3Dafaf3995f16843a1b2afc8bba9efca6a%26pid%3D100338%26rk%3D2%26rkt%3D9%26sd%3D142422412973&_trksid=p2141725.c100338.m3726 ]gauge[/url]

I can't bring myself to call it a micrometer but it's better than a tape measure.

Wow, that's actually cheaper than my solution! 😯

Murray - Member
Or cheap thickness gauge

I can't bring myself to call it a micrometer but it's better than a tape measure.

An ultra cheap digital micrometer! - as we'd say around here "I didn't know the like was in"....
Not that I need one, I've got proper ones, but handy enough for everyday use, I suppose.
Like the plastic verniers that I use to measure tyre widths.

Iirc my SLX rotors are 1.5mm new, Shimano advise replacing at 1.3mm. Mine got down to 0.9mm. New SLX rotors were an amazing performance upgrade!

If anyone is wanting a cheapish micrometer to check rotor thickness then i have two, [url= http://singletrackmag.com/forum/topic/two-0-25mm-micrometers-10-each ]see my for sale post here[/url]

Shimano organic pads

Slx calipers

This was on my front wheel (29er)

I have measured the thickness on all my bikes now. Surprisingly even the 6 month old xt rotors on my cdf are down to below 1.5mm already (running sintered though on these so not surprising)

You have to be a little careful measuring with calipers. If the pad contact is not across the full face of the disc you will get a false reading. Some of my discs have worn slightly concave so the thickness in the middle is less than if you measure across the parallel surface if that makes sense.

Micrometer is best for this as you can measure the middle (most worn area of the disc)

Another option is to stick some ball bearings onto the surface of a known diameter and measure across these with calipers if you don't have a micrometer.

Took me a while to stop shaking.... Thank goodness it was a little wet and my marathon supremes just skidded through swinley. If it had happen on tarmac I would have been properly ducked.

To measure disc thickness you need to get some of [url= http://www.ebay.co.uk/itm/IWANSON-Gauge-Spring-Measuring-Caliper-10mm-Guage-Jewellers-Dental-Crown-Tool-/252484518060?epid=933517776&hash=item3ac94000ac:g:eQcAAOSwRoxXn3fx ]these[/url].

And you'll want to check at the centre of the braking area.

Does anybody else think the new style Sram Guide rotors look like they're designed to fail quickly (with less material in the area which wears the fastest?)

Some Shimano rotors are "resin pads only".

If you run sintered pads....this happens.

I've never been convinced that they're any different to any other rotors, it's just arse covering. I've always ignored it and not noticed the rotors wearing any quicker than others.

That seems like a lot of wear for discs that are a year old 😯

Do you do a lot of miles, how many miles do you think they've done?

Does anybody else think the new style Sram Guide rotors look like they're designed to fail quickly

Yes, there's so little disc material in the pad area I'm surprised they even work 😆

There's a calliper gauge thingy that works well for measuring thicknesses like that (also rim thickness for people with run brakes)

Iwanson gauge. Just a couple of quid on eBay.

I agree ^ run a mix of slx / deore / xt across my 5 bikes. Rotors all different and mix of shimano oem, uber, superstar and ashima pads. Mix of compounds. I think what kills them more than anything is the Ginge! (swinley's lovely trail surface)

Although the broken rotor has only been run on organic oem pads.

Do you do a lot of miles, how many miles do you think they've done?

Depends on where you ride, The Peak kills disk rotors due to the combination of gritstone, water and hills. Swinley isn't much better in terms of gritty wetness although doesn't have so many hills.

Milage probably close to 2000 miles. Quite a lot to be fair. On average 60 miles a week commuting.

At first glance the Guide rotors look like the central grooves are all in the same place but they do actually alternate in their position. Still don't like the look of them though, too easy to wear through the bit between the grooves quickly!

That seems like a lot of wear for discs that are a year old 😯

One of my commuter bikes went through an RT66 rotor on a similar amount of time, gritty roads and use in any weather does that to them.

{stupidlastwords} I'm still running Hope floaters that were 'bedded in' on the infamous Kielder 100 wet and gritty year {/stupidlastwords}

[quote=doncorleoni ]You have to be a little careful measuring with calipers. If the pad contact is not across the full face of the disc you will get a false reading. Some of my discs have worn slightly concave so the thickness in the middle is less than if you measure across the parallel surface if that makes sense.
Micrometer is best for this as you can measure the middle (most worn area of the disc)
Another option is to stick some ball bearings onto the surface of a known diameter and measure across these with calipers if you don't have a micrometer.

I made myself a "tool" by bending an old straight gauge spoke for use with my caliper for measuring thickness of things like that (originally intended for measuring thickness of rims used for braking, which a micrometer won't work for). Don't have a pic of mine, but here's a pic of somebody else's which is much the same as what I have:

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Put the end bits either side of what you're measuring and measure across them.

^ great idea!

That's another toy for the mancave, cheers Murray 🙂

Aldi were flogging cheap (£10) digital micrometers a few months back and I'm sure they'll appear again. Surprisingly accurate and extremely useful for stuff like this as well as accurately measuring bearings so you get the right ones ordered 🙂

Do Shimano make their rotors out of cheese? I've had Hope rotors that were years old and had done 1000's of miles and never had one that even looked close to failing.

I had a set of hope floating rotors, the back one looked fine at first glance but the braking surface was concave on both sides and really thin!

So who took Snap's photo??

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How much do you weigh? 2000 miles is nothing, especially if much of it is commuting. Do you brake like the wind?