Drilled disc

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XTINCT

XTINCT

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I know that many, including myself, have drilled the brake disc.
Has anyone drilled the hub area?
The part of the disc that is not brake surface.
 
A friend of mine departed this planet when the discs exploded off the front of his RG500 Suzuki at the end of Conrod Straight at Bathurst.
 
Yes, similar to the Old Britts above, I have 12 holes, 3/4" dia, in the plate, a little closer to the center than the OB pattern.
I'll play it safe and try to stay away from Conrod Straight.
Sorry to hear about your friend, Alan-
 
Wouldn't drilling your own disc, infringe the safety standard the discs were manufactured under and render the disc not usable on roads today. The local MOT or WOF authority should seek the paperwork on a modified disc, prior to issuing a road safety certificate, and if one is not presented, than a road safety certificate would be declined.. Any safety part fitted to a motor vehicle has to have a certificate of approval from an authority like the UL in The States, or it can not be used on a motor vehicle. This would apply in all countries where vehicle safety is enforced.
Dereck
 
Send them to DBR for drilling and resurfacing. Gary drills the carrier section as well as the swept area of the rotor.
 
just curious, what is the problem that drilling the hub area of a disc is the solution to?

putting holes in the area closer to the fixing bolts would weaken the disc's structural integrity under heavy braking, no?
 
Ditto on Danno ' s suggestion of DBR . Gary will grind them flat and true too , I forget the type of grinding he does at the moment.......blanchard I think it is.
 
1up3down said:
what is the problem that drilling the hub area of a disc is the solution to?
Click to expand...

I don't know just how problematic they are, but my considerations were cooling, appearance, and about 6 ounces (170 grams) of weight savings.
It wd take a serious evaluation to convince me that any significant structural integrity has been lost under heavy (or even severe) braking conditions, but wd love to see such a discussion.
 
I am certainly no metallurgist. But I did read a long discussion about this very issue (weakening etc) on the 'Triples On Line' forum some time ago. If I recall correctly, Triumph discs are grey iron, and folk were suggesting that grey iron can be seriously weakened by this process. Pictures of discs that had disintegrated in use were, frankly, enough to put me off of the idea!

I do not know if Norton discs are also grey iron. But a reasoned debate between folk who know more about this would indeed be interesting.
 
kerinorton said:
Wouldn't drilling your own disc, infringe the safety standard the discs were manufactured under and render the disc not usable on roads today. The local MOT or WOF authority should seek the paperwork on a modified disc, prior to issuing a road safety certificate, and if one is not presented, than a road safety certificate would be declined.. Any safety part fitted to a motor vehicle has to have a certificate of approval from an authority like the UL in The States, or it can not be used on a motor vehicle. This would apply in all countries where vehicle safety is enforced.
Dereck
Click to expand...
This is the situation is some countries (e.g. Switzerland and to a large extent Germany) where they use a type approval system. If you follow these rules you don't change anything (other than perhaps the paint colour) of the bike.
Just how reasonable these rules are when applied to a 40 year old design is somewhat debatable. For example, in the UK you can register a kit car or a special bike with a different frame, wheels etc on a special single vehicle approval scheme, which allows special builders to market kits to the public without going through the whole testing procedure required for series manufacture. The argument here is that its not a problem, since specials simply do not figure in accident statistics. I seem to remember an on-going discussion with the EU (in particular the German TUV), who disagree strongly on this policy.
Personally, I would be very unhappy under such a system.
 
My old rotors were drilled to shit, mostly for weight reduction. I got some old, untouched ones and had Gary do them. The pattern in the swept area is of much smaller and fewer holes than before and there was never a problem with the old ones other than reduced contact which reduced braking power. Norton rotors are cast iron, which makes a fantastic braking surface once the factory plating is gone. None have disintegrated to my knowledge. DBR does grinding and drilling for many of the noted builders around here and many private owners.

Any time you can reduce unsprung weight, you're doing the suspension and your whole machine a favor.
 
I believe the original rotors are cast steel not cast iron. What you might get from the pirate product market might be an issue.
 
It may not be relevant, but talking to some guys at Pukekohe one year, I was told about a group of British bikers that "raced " over the Takaka hill from the Nelson side. The Takaka side drops straight down a zigzag for 800 metres. One of the bikes front discs got so hot, it warped, and jammed in the caliper. What would it have done if it had been drilled. I think he would have come off and lived because those corners are so tight, he probably could not have exceeded 50 mph on them. 25 mph would have been too fast for me.
Dereck

PS, I like the new look of the forum. Pity about the work that had to be done to save it. Hackers should be tied to one of "Kims" rockets,. I did wonder why I couldn't log on in my usual quick way. I am still too thick to work out how to add an avatar.
 
I do know there are reasons such as rotor cooling and effects due to unsprung weight and also rotational inertia to be considered since motorcycle rotors do have considerable mass. That said, I remember in the bicycling world of amateur racing there was a fad in the '70's and '80's of saving as much weight as possible by drilling out every single component. Everything was drilled to a final fragility. So a 20 pound overweight out of shape bicyclist saved 10 ounces. We called the resulting wonder metal "drillium". Pictures of this stuff are a true testimony to the industry and dilligence of some people.
 
From my experience of machining cast iron, it forms very fine chipping and the free carbon present manifests itself as black dust, you would get dirty hands handling it and in thin sections such as brake discs it would be very brittle. Whilst I don't intend putting a grinding wheel against my disc, the sparks formed from cast iron would be dull red. My money is on cast steel, but it would be interesting to see what the swarf looks like when machined, Maybe Gary from DBR would know.
 
If they're the same as the Triumph ones they are cast iron. Around 1981 I drilled my own while I was at work on a woodworking Mortice machine fitted with a chuck. My gaffer caught me an demanded to know what I was doing so I said, "I'm drilling my discs" to which he said "Oh", and wandered off. BTW, mine didn't explode luckily.


Drilled disc
 
I would not drill the centre area on a finished disc, it is cast iron. Likewise the pads now made by AP have a friction material for use with cast iron. As far as I'm aware no other manufacturer of pads supplies the friction material on a standard pad to suit the cast iron disc, only steel. Not sure about pads for other calipers, but when I have asked, none of the mainstream do due to steel rotors being so common in the motorcycle world.
 
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