Chinese wavey disc..

[Mr Gazza]

http://www.ebay.co.uk/itm/190959233447?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

My rear disc has a VERY slight warp and I was thinking of changing it, but with no particular urgency.

The wavey disc on ebay caught my eye, the price is not too bad and I wondered if it would be any good...Has anyone used one of these? Or know of their reputation?

On a more fickle level I wondered if it is considered uncool to have a wavey disc on the rear but not on the front??
I could not find matching front rotors in this particular ebay shop, but if there are fronts at a similar price it might be worth a shot...That said there is actually nothing wrong with my front rotors.

What do you think?

[DrD]

Hmm, I have rear wavy but its an Armstrong. And the reasoning for the extra cost is fairly clear.

[Dukedesmo]

I have wavy/cutaway discs on the rear of both my Monster and 916 - mainly because they weigh less and they have enough power, especially as I don't use them much anyway.

The one on my Monster was a cheap ebay disc (not the same as that one linked to though) and it is fine.

I wouldn't use them on the front where I want the best brakes available...

[Mr Gazza]

...........So is the thinking behind the wavey discs to save weight.?
I've only really noticed them in last couple of months or so, and figured that the purpose of cutting away a lot of the disc is to disapate heat and increase the pressure per square mm of the pads.

They do look "angrier" on the front and I assumed that it was a performance mod, but if brake power is lost then I am not interested.

BTW. I have never really liked Stainless Steel as a disc material. When I had the chromed iron discs on my beloved OIF triumphs, The braking power was always far superior when the chrome was skimmed off to use the iron surface.
The best stopper I had was with twin skimmed and drilled iron discs with Lockheed racing calipers and soft pads....Formidible stopper and loads of feel too..

[Dukedesmo]

They do look "angrier" on the front and I assumed that it was a performance mod, but if brake power is lost then I am not interested.



I don't see, from a technical point of view, how they can work better with less friction/heat dissipation area? I know they claim more initial bite, self-cleaning (maybe useful on dirt bikes?) but ultimately I'm convinced that a good round disc is better.

Both my Ducatis have round, stainless front discs and both have more than enough braking power for anyone under any circumstances, and the M4 Monoblocs on my Monster have plenty of (perhaps too much for some?) initial bite so I don't know what wavy discs could offer above them?

[Yorkie]

Try these:

http://www.blackshadow-uk.co.uk/Ducati.html

Made in Wales, might be what you are looking for.

Yorkie

[Nickj]

Got some Chinese ones o the front of mine, they're copies of an American design as far as I can see. The material spec is the same on paper but it is a bit hard to tell and if you want reassurance they're mostly made in the same factory and production lines that the big jap bike manufacturers out source to.
Do they work OK, well the bike stops just as fast as it used to, no lag in the wet etc. If I could change one thing it would be to go to a slightly softer pad than the HH's.
Otherwise works fine for me.

http://homepages.nildram.co.uk/~njames/misc/before_after.jpg

Oh have new tyres on ... bridgy T30F's like 023's but better

[Nickj]

......... so I don't know what wavy discs could offer above them?

They're pretty !!!
Yes the swept area is slightly smaller and the surface area to radiate off heat isn't significantly different, the material is the same so I think the answer is...

Yep Pretty like carbon, now carbon rotors would be uber cool

[Wasta]

I like the look of the Blackshadow discs, the price seems reasonable as well.

[Yorkie]

I like the look of the Blackshadow discs, the price seems reasonable as well.

I have some front ones on my SS project:

http://i1286.photobucket.com/albums/a615/Yorkie13/Ducati%20Monster/Ducati%20750SS%20Project/photo67_zps4cee0259.jpg (http://s1286.photobucket.com/user/Yorkie13/media/Ducati%20Monster/Ducati%20750SS%20Project/photo67_zps4cee0259.jpg.html)

They seem quite good quality and look good as well.

Yorkie

[Mr Gazza]

Interesting stuff..thanks for the info guys.
I think I might take a chance on a Chinese wavey rear, so I know it's not warped, but I don't feel a desperate urge to put new discs on the front just yet just for the sake of it.

If anyone is looking for some this might be of interest.
http://www.ebay.co.uk/itm/DUCATI-BREMBO-320mm-FULL-FLOATING-FRONT-BRAKE-DISCS-ROTORS/281208431944?_trksid=p2045573.m2042&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3 D1%26asc%3D19167%26meid%3D2817613604430776287%26pi d%3D100033%26prg%3D8693%26rk%3D2%26rkt%3D4%26sd%3D 130698213757%26#ht_2744wt_952

I like your photo Nick with the split wheel shot...Very good. Same Brembo wheels as mine too, and as it happens I was enquiring about "Brembo" Gold paint today, as I am intending to re-finish them over the December Hols.

Both the Chinese and Welsh discs look good, I think it was Yorkies discs that first grabbed my attention, they have a lot of asthetic appeal but when it comes to brakes, efficiency comes first with me...Nobody has convinced me yet that there is any advantage to a wavey disc(s) though at the moment there does not seem to be any particular disadvantage.

[Musty]

I fitted Armstrong Wavy on the front of my 696. Not a bad thing to say about them, smooth & progressive unlike the stock Ducati pile of poop.

http://www.musto.me/images/wavy.jpg

[damien666]

A friend of mine bought some front chinese discs for his old Yam TR1 1000 v twin.
First lot were wrong offset, second pair were both for one side instead of L&R.
He said never again!
The quality didn't look bad to be honest.

[Mr Gazza]

It's always a worry ordering from the Far East damien666 but to be honest it can sometimes be as bad from just down the road. At least these days there is Ebay and Paypal to stick up for us...Just had a total no fuss refund for some goods that didn't show from Germany.

Musty, if those brakes of yours make Ducati ones look like a pile of poo, then that is high praise indeed...Unless someone was greasing your pads..??

[Dirty]

I just don't get it. I mean I know it seems to be the case that they work fine but how can having less surface area mean no loss of braking? And if that is the case why don't they put holes in pads or give them a 'wavey' slant.

That said I'm not a fan of the looks anyway.

[chris.p]

One piece of advice I can give, I have seen a couple of Chinese front disc's that started to get cracks in the internal corners of the carriers, not good:thumbsdown:
On close inspection it would appear that the cause was that there was not enough internal radius /curve in the shaped holes in the carriers, if you look at the 3 examples of front discs shown, the Chinese ones have less curves than the other two.
I hope that made sense ad I am sure there will be a more technically correct explanation along shortly.

[Musty]

Musty, if those brakes of yours make Ducati ones look like a pile of poo, then that is high praise indeed...Unless someone was greasing your pads..??

No grease involved :D

I went through a couple of sets of standard ducati discs which were warped within months. Rosso fitted these for me back around May and they've been brilliant since. Breaking is even and especially those last few mph where you might expect some jerking, its completely smooth. High praise for these discs and I'll replace the rear with one as soon as it needs it.

I'd avoid the cheap chinese ones though. Armstrong is a very well recognised brand. Moore Speed sells them.

[Mr Gazza]

I just don't get it. I mean I know it seems to be the case that they work fine but how can having less surface area mean no loss of braking? And if that is the case why don't they put holes in pads or give them a 'wavey' slant.

I don't get it either Dirty, but Musty is clearly enjoying a big advantage over standard discs.

Musty has given me a clue regarding the warping.

These are my suppositions given that I do not pretend to understand the science of these wavey discs.

I use a lot of circular saw blades in my proffesion and there is sometimes a problem with warping due to over heating from the friction caused by certain cutting conditions when the wood can distort onto the blade nipping it a bit like a brake pad.
I have noticed peripheral slots in some blades, sometimes these are quite large and pronounced, not unlike the slots in the wavey discs. Theses are known to be there to help control the warping from heat.
When a blade (or disc) expands due to heating the extra dimension has to go somewhere, and I am proposing that what happens is that the circumferance increases proportionally more that the diameter, leaving more material than can be contained in a flat plane...Ergo the circumferance is forced onto another plane, or warped.

The slots are effectivly gaps in the circumferance and therefor allow the disc to expand into them thus keeping the disc in a flat plane....Hope you can see what I'm getting at even though I might not be right..?

Musty claims that his brakes are smooth right up to the end of the application when the discs will be the hottest and most likely to be warping...So maybe that lends my theory some credability..?

As for the lack of area on a wavey disc not appearing to decrease the power. I think that maybe something to do with pressure per area.
If you have the same weight (or braking effort) on a normal rota and a wavey disc, the weight per sq mm will be higher on the wavey disc, as there will be less sq mm to bear the weight....So I believe the effective braking force would be the same.?

Of course all that friction is the cause of the heat (a lot of it) and it begs the question that if there is more pressure on the wavey disc for the same braking effort there will be more friction, so will there be more heat in less metal.? or is the wavey disc benefiting from a lower thermal mass..?....That's me out of my depth now, but I had a go..:chuckle:

Does Brian Cox visit this forum?....anyone..?

[Dirty]

I don't get it either Dirty, but Musty is clearly enjoying a big advantage over standard discs.
......
......
As for the lack of area on a wavey disc not appearing to decrease the power. I think that maybe something to do with pressure per area.
If you have the same weight (or braking effort) on a normal rota and a wavey disc, the weight per sq mm will be higher on the wavey disc, as there will be less sq mm to bear the weight....So I believe the effective braking force would be the same.?


You have me right up to the braking force per sq mil. I can see that a pad pushing on flat steel is spreading the load and if there was a hole in the steel the pressure per mil would be higher but if that steel is rotating then the friction per sq mil must be less unless it is balanced by extra pressure. If that is the case then why not have 10mm square pads and similar sized discs and huge pressures?

[Albie]

I have had one set replaced on warranty and these are warped a bit too. Looking for some more. Theres some really trick ones made on the IOM we saw this year. Fantastic mounting system too. Need to find the link. BigOz and Rally will back me up.

[Mr Gazza]

You have me right up to the braking force per sq mil. I can see that a pad pushing on flat steel is spreading the load and if there was a hole in the steel the pressure per mil would be higher but if that steel is rotating then the friction per sq mil must be less unless it is balanced by extra pressure. If that is the case then why not have 10mm square pads and similar sized discs and huge pressures?

No.. I think that for a given weight, the pad pressure increases as the area diminishes, and therfore friction will balance up to the same thing.

I see what you are getting at by suggesting that the pressure should increase if the pad area was reduced, but I don't think that the idea behind the wavey discs is to increase the pad pressure but more of a happy accident that that happens (if indeed it does) when the problem of the warping is addressed..

...Drowning here....Help...!

[Dirty]

No.. I think that for a given weight, the pad pressure increases as the area diminishes, and therfore friction will balance up to the same thing.

I see what you are getting at by suggesting that the pressure should increase if the pad area was reduced, but I don't think that the idea behind the wavey discs is to increase the pad pressure but more of a happy accident that that happens (if indeed it does) when the problem of the warping is addressed..

...Drowning here....Help...!

I'm glad it's not just me that's drowning.

So, just for example, pressing the brake exerts 10kg of pressure. The pad is 10 sq mm, the disc is standard. The pressure is then 1kg per sq cm. Cut a hole in it and reduce the area by 50% and the pressure is 2kg per sq cm which creates equal frictional force (presumably the figures go up and down as the holes move around!)

If that is roughly correct as we understand it there must come a point when it does stop being equally efficient to a standard disc?

Aargh! Stop all this silly Higgs boson nonsense, tell me how wavey brakes work Mr Hawkings! :)

[Albie]

Here if you want the best and all the race teams are starting to use them. They are affordable too

http://www.west-performance.com/pfmbrakes.php