K11 Owners Group

Beachcomber · Posted: Mon Feb 01, 2010 10:21 am Post subject: K1100 - stainless vs cast discs?

gentlemen,

what's your thoughts on Stainless vs Cast discs - specifically K1100 / Oilheads.

I'm currently in talks with Realm, who have spoken with one of their overseas suppliers re: supply of discs at a reasonable cost.

We can have "wavy" stainless discs or plain / grooved cast discs.

Your thoughts?
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Beachcomber '93 K1100RS / '93 K1100LT and several K100's

RobWheatley · Posted: Sat Feb 27, 2010 5:58 am Post subject:

I have just bought a pair of used Grimeca cast discs off Ebay to replace the stainless (warped) fronts, will let you know my thoughts and how they perform as soon as they are fitted.
Rob
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1999 K1100LTIC Smooth and Quiet Smile

Cruise, BFD & HID
1996 K1100RS. dead but not forgotten.

Ernie-NH · Posted: Sat Feb 27, 2010 10:01 am Post subject:

Good Morning B/C....

Those of us who are or have been Airhead riders have long believed and experienced "cast discs" to be superior in 'maintaining shape' and in 'stopping power' when compared to discs made of stainless. Could be there is yet another material for discs out there which would outperform that which we know, but as yet it has not been introduced, to the best of my knowledge. Sounds like it would be a GREAT research project and/or thesis topic !

Best regards...........// Ernie-NH
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AMA,, American Deaf Bikers
Airhead Beemers Club
'11 G650gs
'95 K1100LT
'76 R100/7

Technician · Posted: Sat Feb 27, 2010 10:54 am Post subject:

I swopped the stainless OE discs on my K100Lt for cast ones supplied by Motorworks and changed to the recomended Ferodo pads and the resulting braking performance was superb. The only downside was that a thin film of rust used to form on the surface of the discs when they got wet but would be cleared off after a couple of applications. I haven't got round to changing the K1100 discs yet as they are still servicable but if the price is right i'd be interested.
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Fat Ba***d with a K1100LTse
Squire D18 trailer
Garmin Zumo 660
"Run it round the block to see if the wheels fall off!!!!"

duckbubbles · Posted: Sat Feb 27, 2010 3:00 pm Post subject:

Cast iron has a better coefficient of friction than stainless steel. If you don't mind having a slight coating of rust once in a while, go with cast iron for the performance.

Frank
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85 K100/1100RS, 321,000 miles, 25 years
96 Ducati 900SS/SP, sold it
05 R1200ST, 35,000 miles, 5 years
400,000 BMW miles

hockeyshifter · Posted: Sun Feb 28, 2010 4:52 pm Post subject:

The Disk is really just a large heat sink... if u get metal hot enough it will warp period. the advantage to cast is less alloys ( nickle candminum etc.) and more carbon. but the down side is rust. A bike just dose not look pretty with rusty disks. i had a honda a with Stainless disk and to stop the bike took alot of effort. What u can do is get a cast disk and paint it with high temp engine paint then scuff or scrap or mask off areas of the pad contact patch. this will inhibit but not stop the rust on the disk.
if u look at the Superbikes u will see that they are using carbon/cardon brakes the reason are because of heat issues. at the first few laps they really suck for stopping but as they heat up the preformance imporves. the oppsite is for cast the cooler the disk the better the stopping .. Stainless is in the middle some were. another factor is the pad meterial. u can get pads that will grind down a disk min thickness with out ever showing signs of wear on the pads. u will need to strike a balance.
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fix the problem not the blame ; fix what is messed up ; NO one is to blame.

tmoons · Flying Brick Rider Joined: 09 Oct 2008 Posts: 161

I think the hockeyshifter is right on the money,
find the right pads (I heard good stories about EBC "green stuff" )
or proper sintered (copper) pads.
The problem with the cheaper sintered ones is that the bits of material in the pad are way to coarse and that the more expensive ones have a much better grain-distribution... and thus being favourable..

Beachcomber · Posted: Mon Mar 01, 2010 8:46 am Post subject:

Hockeyshifter / Theo,

yes we ARE going for stainless - with SUITABLE pads. Wink

The Discs will be "wavy" pattern with holes to assist with the heat sink problem. The tech guys are currently testing disc / pad materials for the best all round performance. Once they've selected their choice, we will get them tried out in the real World on suitable bikes. We are lucky in that we have secured the services of a couple of Kay bike Couriers for road testing - who do Starship mileages! Laughing

Their normal riding will take them through all road scenarios and weather combinations.
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Beachcomber '93 K1100RS / '93 K1100LT and several K100's

RobWheatley · Posted: Mon Mar 01, 2010 4:21 pm Post subject:

Beachcomber · Posted: Tue Mar 02, 2010 5:29 am Post subject:

sorry, that was my very sloppy use of the English language. Embarassed

I should have said the PRIMARY reason for the holes was water diffusion - to which the wavy edges contribute.
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Beachcomber '93 K1100RS / '93 K1100LT and several K100's