Brake discs?

[BenR]

Hi all at the moment I'm looking for a new set of brake discs for my wolf project. Below are a couple of links for some that are in my watch list.

https://www.ebay.co.uk/itm/301370988095?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
https://www.ebay.co.uk/itm/180842253885?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Has anybody used these before? They're unbranded & from Hong Kong but they look like Kagizume discs (which are Chinese) which I haven't heard of any horror stories about. Inb4 "you've answered your own question" any advice much appreciated ta!

[........................]

[BenR]

Any evidence to back that up?

[iooi]

[........................]

[Snorty]

I've heard bad things about them being made of sub-standard metal and thus being prone to warping.

This, I heard online.

I have two friends who bought Chinese discs and they claim they're fine.

I wouldn't buy Chinese discs, however. I'm a believer in "it's cheap for a reason". I do realise sometimes it's just high mark-up though.
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Current: Yamaha FZ1 '07 | GSXR 750 SRAD

Past: CB125TDC | TZR125 | GPZ500 | CBR600F3 | ZX9-R | GSXR1000 K4

[BenR]

[MCN.]

Price up an OEM disc, it might well be cheaper than you think and better than any shitty pattern one.

[iooi]

[BenR]

[talkToTheHat]

E(kinetic)= 1/2 * mass * velocity ²

Weight of a bike is not as significant as the velocity at high speed, 60mph is about 26 metres/second so v² is 676, so with bike plus rider at 200kg that's 135kJ of heat to dissipate. 270kJ for a fat rider on a big tourer or two up (400kg). This is about the same as braking the 200 kg bike from 80mph. (36.7m/s to 3sf)

Go figure how this applies to the heat put through a brake disk in each of your applications. The 125 probably has a braking system that can deal with significantly more frequent braking from terminal velocity than the gxsr750.

Note however that a brake rubbing at 60 mph might fuck up the disks on either bike.

Note further that sintered pads transfer much more heat to the caliper and thus brake fluid than organic, carbon ceramic or racing carbon brakes, so in some circumstances heat is transferred differently.
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Bandit. does. everything.

[lihp]

[Snod Blatter]

I had a pair of earlier non-wavy Kagizumes on a TRX850, they performed perfectly until I asked them to commute for a couple of months of winter when they started to warp. I laid the bike up after that and used something else to get to work, then came back to the TRX in April/May time to find the discs had warped more than I remembered. It turned out that the semi floating bobbins were full of corrosion and it was impossible to clean out, so they were scrap.

As an aside they were also significantly heavier than the OE Yamaha discs I replaced them with, so while not outright dangerous they don't have anything going for them other than price. Wear after around 7K miles with sintered pads was also non-existent but it doesn't matter when the bike is trying to throw the MOT guy onto the floor as he tries to test the front brakes on the rollers..!

[iooi]

[UrbanRacer]

There are no reports because people that buy them don't want to hear "I told you so"

[talkToTheHat]

[quote="lilihpBut mass and weight aren't the same thing [/quote]

Nope. But as weight was discussed it was worthy of a mention. Furthermore in earth gravity at non relativistic speed we don't have to worry too much, although the bike that weighs more will exert more force on the road through the tyres and thus the friction would be proportionally higher. There is a limit of about 1.1g to the possible braking deceleration in both cases though. And yes it's above 1g because tyres do amazing chemistry things with the road. Most riders will not be able to consistently sustain such braking deceleration.
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Bandit. does. everything.

[Tiger900]

Two years ago I purchased two wavy rotors from Ebay for the front and a plain disc for the rear both were Kagizume make as the Triumph ones were silly priced (£750 for 3).
*** The Good ***
They are really cheap and looked good for a week. They brake and stop you fine and passed an MOT.
*** The Bad ***
They were advertised as stainless but after two weeks rusted quickly so looked like they were years old.
Within two Months the front discs warped slightly but they actually worn flat again after 6 Months of use. The rear disc bolts had to be filed shorter as the disc was slightly loose due to slight spec difference in thickness. I used Hammorite black on the rusty part of the disc.
*** The Ugly ***
My rear disc snapped last week in one place and cracked at the opposite side and had a 4mm gap once I took the bolts out. Luckily it did not fall in half.
The disc has not had much wear.
It looks like the disc was permanently stressed in manufacture causing it to be a time bomb. It is so stressed that I cannot manually close the 4mm gap again with brute force.
Bottom line I will never buy Kagizume discs again. Mine was dangerous and very poor quality.

[ZX-7R]

If there is one thing i will never,ever go cheap on,its brakes.

You can't buy a new,better set and undead yourself.
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Current Bike - 2000 ZX-7R