The outside of a motorbike engine seen up close near the exhaust

Home Repair And Restoration

CBF125 Front Brake Disc

Repair Date 14 August 2017

By Ren Withnell

You ride the miles. You change the brake pads. You ride the miles. You change the brake pads. You ride the miles. You change the brake pads. You ride the miles. You change the brake pads. 

I never really considered the disc though.

Then while poking tools into places they ought not to go I saw that note on the disc "MIN TH 3.5MM". I've read it a thousand times before but today I'm wondering how thick my disc actually is. Ooooh, I have a micrometer thingy somewhere.

The markings on the brake disc are stamped min th 3.5 mm
I've read it, never actually checked it.

Not being a finicky, do things properly engineer type of guy I'm still getting my head around reading these tiny little markings on the micrometer. I'm getting old too, I need my glasses. Right so that's 0.5 and that's 1, so that's 2. Erm I can't see the 2.5 marker and the twiddly turny bit is at 30. Right erm that' 2.3mm!!

While I'm not a consummate engineer I am fairly good at mathematics. After years of schooling I am quite sure that 2.3 is LESS THAN 3.5. I check this on Google and yes, 2.3 is definitely less than 3.5. Oh dear.

So what's the problem? The brakes work just fine. Meh, why would there be a "MIN TH" anyhow? Then I start to remember images of cracked discs, tiny little hairline fractures appearing between the drilled holes. There's none on my disc as yet but that doesn't mean it won't happen. Then I have visions of shattered discs. If I'd read "3.40" on the micrometer I would just add "brake disc" to the list of things to keep an eye on but as my disc is not much thicker than a CD perhaps now is the time to act.

Tiny cracks appearing around the vent holes on a brake disc
I don't want to see these thank you.

OK. Right. Get This. Wemoto want £93.90 for an EBC disc and £85.92 for a "pattern" disc. Ouch but yeah, that's what brake discs cost for motorcycles, the robbing swines. Honda, well they'll be like £200 won't they? Nope. £49.67. So a genuine OEM part from a genuine Honda dealer is almost half the price of an aftermarket item? Check those OEM prices folks, you may be surprised. However Max Motorcycles list a pattern part for £25, with delivery that comes in at just under £30. Sold

Changing the disc is a doddle, I'll not bore you with the details. The problem with replacing the disc is that it has not made one jot of difference to the motorcycle. It stops the same, rides the same sounds the same and so on. I suppose I just don't need to worry about cracked discs so much.

The new disc fitted to Ren's CBF 125

Have you got a confusing prices for bike parts story? Drop Ren a line -

Reader's Comments

Ian Soady said :-
Rotors? Discs, old chap (with a "c" of course).

Although you only use the offensive term in the teaser on the main page.
20/8/2017 3:49:51 PM UTC
Ren - The Ed said :-
What on earth is wrong with "rotor"? Or indeed "disk" as opposed to "disc"? I take it you're opposed to Americanisms Ian.
21/8/2017 1:32:03 PM UTC
Ian Soady said :-
Yes. We have a perfectly good language already. No need to pretend to be trendy.

On the other hand, there are some neologisms which are useful......
21/8/2017 2:38:16 PM UTC
Ren - The Ed said :-
I believe the beauty of the English language is that it is NOT precious or precise and it can be adopted and adapted and mixed up and incorrect and yet still be understood. If the Yanks want to drop the "u" from colour then fine. If the Aussies poop in a "dunny" then great. If youths wanna say innit then thas fine then innit.

I can hear you cursing in your finest received pronunciation Ian :)
21/8/2017 7:51:46 PM UTC
Borsuk said :-
The faint Glaswegian lilting/braying curses you can hear alongside Ian's are mine. I deplore the Americanisation of English as well. The boy has a tendency to use Americanism's when he speaks and I just ignore him till he tries again in English. It also peeves me that my idiot machine at work was set up by a French IT twit who set all the neteork defaults as American resulting in a need to go to the printer to tell it to resize the print outs to A4/3/2 paper if I forget to resize it before hitting the button and a spell checker that keeps replacing S's with Z's to words and deleting U's.
On the posted subject I have just fitted new brake pads and disks to my car front wheels. I replaced the pads earlier this year and they were fine for 3000 miles till I took the car to an UK Suzuki dealer after which she developed a horibble rubbing noise around 500 miles later, some where south of Paris on the way back to Spain.
The brake pads have glazed areas on them and the disks have rough areas which weren't there before. I may take a sander to both and put them in the used but good shelf in my workshop, though with brakes I tend to replace rather than repair.
22/8/2017 12:58:05 AM UTC
Ian Soady said :-
"I can hear you cursing in your finest received pronunciation Ian :) "

You've met me and know my pronunciation is far from RP.....

I don't care what people from other countries do. However, you try posting on a US-based forum and using English spelling and they get all shirty.

As I said, I'm not against change. I am against letting all English-based languages drift downwards into a transatlantic mire.

Borsuk - thanks for the support but you used the spelling disk..........
22/8/2017 9:10:57 AM UTC
Borsuk said :-
Back of the class for me and on with the dunce's cap.
Do any of you find you have to think more about your spelling when you type than you do when you write.
23/8/2017 7:21:35 AM UTC
Ren - The Ed said :-
So note to self - spell color with a "u" and disk with a "c". I should be OK to say "innit" but not "gonna" or "gunna".

Borsuk - being of the modern age I use computers all the time and to be honest my writing is pretty appalling now. As for spelling I don't find any difference and to be honest as most of my writing is just the occasional notes for my own use I don't worry about the spelling.

Yes, the art of writing as in physically using a pen and paper is dying. Many will bemoan this but I see it as part of a changing world. We no longer use leaches in medicine (actually they are sometimes used but you get the idea) or magnetos on motorcycles.
23/8/2017 10:46:16 AM UTC

Post Your Comment Posts/Links Rules



Add a RELEVANT link (not required)

Upload an image (not required)

No uploaded image
Real person number
Please enter the above number below

Home Repair And Restoration
Admin   Re-Login