Front brake discs
- Thread starter pierodn
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Norton rotors were completely dull chromed over so the 'shiny' one is simply less worn and less desirable than the rusty one grip wise. Grinding like car rotors is a no no d/t less friction of the machine lines in line with motion. Cross grinding or blasting is preferred method to remove the slick chrome surface.
I can't cLaim to be a expert on any of this but can tell you my experiance. About 5 years ago I bead blasted mine to rid it of rust & the plating, then turned it on the lath to clean all the edges slightly etc. Repainted the center & it seemed to make a big improvement. I did have a sleeved MC but since have gone to a more modern Magura one..do a search to get advice from more knowageable members..
Turning a brake rotor on a lathe leaves a spiral grove that the pad follows. This produces a ratcheting effect for the pad. A slight sanding with a D-A sander will remove the spiral lines left from turning the rotor.
There was a test done with automobile rotors that had been turned on a conventional brake lathe versus ones blanchard ground. Those that were ground needed less distance to stop than those that were turned.
There was a test done with automobile rotors that had been turned on a conventional brake lathe versus ones blanchard ground. Those that were ground needed less distance to stop than those that were turned.
rvich
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When a disc is turned on the lathe it essentially creates a pattern just like a record album. The pads try to follow the spiral just like the arm of a turntable. The pads are restricted in the distance they can move so they are forced upward out of the grooves and have to reseat over and over again for the duration of the braking period. This actually increases stopping distance by a considerable amount.
Thus grinding with a circular motion is preferred. Such that the lines are a confused pattern that the pads don't try to follow. This would hold true for brake drums as well. Destroying the spiral effect is what is desired.
Russ
Thus grinding with a circular motion is preferred. Such that the lines are a confused pattern that the pads don't try to follow. This would hold true for brake drums as well. Destroying the spiral effect is what is desired.
Russ
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The method of turning rotors referenced by Jim and Russ is explained in the link below:
http://www.oeqf.com/techinfo/scratching ... ing_lg.htm
The importance of cross-grinding the rotor is not subtle; spiral-turned rotors without this important step can double the braking distance.
http://www.oeqf.com/techinfo/scratching ... ing_lg.htm
The importance of cross-grinding the rotor is not subtle; spiral-turned rotors without this important step can double the braking distance.
IIRC, Fred of Old Britts used to offer blanchard ground rotors. No doubt, Michael Morris of Vintage Brake can do the same. Personally, I think replacing the stock Norton rotor with one of the floating rotors makes more sense. Of course, it would no longer look stock, which has never been a concern of mine. Whereas, stopping quickly has been a concern.
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I've heard that cast iron discs are more effective than most . Back in the 70s when we had the first Suzuki RG500s, they were fitted with chromium plated aluminium discs with rivets to allow float , and the chrome used to spall. The father of one of our top guys had discs made from the cast iron brakes off a fork lift. During a race, the rider was approaching Murray's Corner at the end of Conrod straight at Bathurst when the discs exploded off the bike. He passed a friend of mine while climbing off the back of the bike. He died in the spectator area. - Take care fellas.
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I was simply offering a word of warning about materials. - I'm not being a misery guts. There are there common grades of cast iron - grey cast iron, meehanite , and cast iron containing nickel. It is possible to make gears out of the latter ,the second is used for drum brake liners , the first is rubbish. In a similar vein, in 2003 our club ran the national historic championships. Both fork yokes on one bike broke in the middle of a race, and the whole front end came off. Someone had simply used the forged steel ones as a pattern and had aluminium ones cast off it. A little knowledge is dangerous.
Rohan, your approach to safety is not helpful. And if you got off your arse and got some experience, that would be good for everybody. The man's name who died was Ross Barelli - a very nice bloke.
Rohan, your approach to safety is not helpful. And if you got off your arse and got some experience, that would be good for everybody. The man's name who died was Ross Barelli - a very nice bloke.
No-one here in this thread is talking making their own disks ?
And you go off on a weird tangent, as usual.....
Sad to say it for Ross, but anyone who races with 'cast iron disks from a forklift' is on very borrowed time ?!!!
Ever heard of the Darwin Awards ?
Almost every car made for decades and decades and decades had cast iron disks, this is almost horse-and-cart technology, not rocket science.
P.S. I have seen a pair of broken guzzi disks, under extreme provocation it must be said, they are not made of some magic stuff.
(Something large and relatively heavy hit them)
I'd imagine that stainless probably would have bent in the same circumstances...
And you go off on a weird tangent, as usual.....
Sad to say it for Ross, but anyone who races with 'cast iron disks from a forklift' is on very borrowed time ?!!!
Ever heard of the Darwin Awards ?
Almost every car made for decades and decades and decades had cast iron disks, this is almost horse-and-cart technology, not rocket science.
P.S. I have seen a pair of broken guzzi disks, under extreme provocation it must be said, they are not made of some magic stuff.
(Something large and relatively heavy hit them)
I'd imagine that stainless probably would have bent in the same circumstances...
Sorta ?
I'd have said the brits plated their iron disks to look good in the showroom.
Until the flash of chrome wore off, the brakes were decidely feeble.
Japanese bikes, and BMW it must be said, (and others) used stainless disks.
Don't rust, but not much braking when wet, until ALL the water wipes off.
And still not quite as strong a braking as iron disks...
Slightly different philosophies....
GR8 photo of a flying Matchless.
Whoever took that knew how to wave a camera.
I'd have said the brits plated their iron disks to look good in the showroom.
Until the flash of chrome wore off, the brakes were decidely feeble.
Japanese bikes, and BMW it must be said, (and others) used stainless disks.
Don't rust, but not much braking when wet, until ALL the water wipes off.
And still not quite as strong a braking as iron disks...
Slightly different philosophies....
GR8 photo of a flying Matchless.
Whoever took that knew how to wave a camera.
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Seeing as as we're digressing , in part . :lol:
Rickmanish .
seems the origins of the Novil front brake / fork leg , perhaps .
the Jap shiney stainless things took a few revolutions before gripping , in the wet . A panicer would have the Lever on HARD by then .
as it ' Gripped ' on the Wet Road .
Where horrible old Iron things like on European stuff , would work under water , the Germans didnt know this , at the time . Which is Why they lost W W II .
Rickmanish .
seems the origins of the Novil front brake / fork leg , perhaps .
the Jap shiney stainless things took a few revolutions before gripping , in the wet . A panicer would have the Lever on HARD by then .
as it ' Gripped ' on the Wet Road .Where horrible old Iron things like on European stuff , would work under water , the Germans didnt know this , at the time . Which is Why they lost W W II .
My take on the discs, is that exposed cast iron will rust when subjected to the atmosphere/water but work well in the wet.
Stainless one do not appear to work well in the wet, sometimes giving a time lag before working, also with these I have found that if you do not regularly wipe the discs clean, a film of brake dust “clings” to the stainless disc, ruining the braking even more.
Stainless one do not appear to work well in the wet, sometimes giving a time lag before working, also with these I have found that if you do not regularly wipe the discs clean, a film of brake dust “clings” to the stainless disc, ruining the braking even more.
i dont think that there is a problem with stainless steel per se, but that in the 70s Pad compounds and leverage ratios were very poor and the blame was put on stainless steel, because Jap bikes used it and we all know that jap bikes had crap brakes!
with a revised mastercylinder ratio and modern pads the brakes on my 75 R90 are fine, wet and dry. I will keep the original disc on my Commando, but get it bead blasted and zinc plated.
Apart from the rusting, the other big downside with cast iron discs is that they weigh a lot more than equivalent stainless.
with a revised mastercylinder ratio and modern pads the brakes on my 75 R90 are fine, wet and dry. I will keep the original disc on my Commando, but get it bead blasted and zinc plated.
Apart from the rusting, the other big downside with cast iron discs is that they weigh a lot more than equivalent stainless.
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My Seeley has two Suzuki discs on the front. They don't look like they are made of stainless steel - perhaps a grade of high speed steel (about 3% chromium). I tried carbon pads, however now I have four of the old asbestos pads and the braking is superb - predictable, but stops like hitting a wall from high velocity. I've ridden the bike in the rain and won a race under those conditions - at times like that I tend to stroke the brake, not grab it.
When I first bought the rolling chassis, it was fitted with a stainless steel disc and one Lockheed caliper with the asbestos pads - when I'd built the bike, it would not stop. I managed to get the extra caliper by swapping a medium sized GP carburettor for it.
When I first bought the rolling chassis, it was fitted with a stainless steel disc and one Lockheed caliper with the asbestos pads - when I'd built the bike, it would not stop. I managed to get the extra caliper by swapping a medium sized GP carburettor for it.
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