Steel Discs.....

[bornagainbiker]

Hi fonts of all knowledge..............

I recently bought a 1100 that has had the OE discs replaced with steel ones.
Can anyone shed any light on experiences with these? Do they last longer, perform any better? They look bloody unsightly when they rust up (after being parked up overnight when left outside) and that worries me abit!!

More to the point, would the light rusting up, and then cleaning up when being used affect the pads?
Any comments most welcome

Paul (Born Again Biker)

 

[sparkplug]

Speaking from complete ignorance and without experience...

Could these be the Cast Iron discs that Motobins sell?

They are supposed to be superior for reasons I have completely forgotten but I'm sure a quick search would find results.

I've never seen one, or even a photo of one - I just know that cast iron shows rust very quickly.

Helpful or Red Herring?

 

[Possu]

Cast iron rusts very quickly but braking is improved as it has a better (greater?) coefficient of friction, hence being popular on race bikes where carbon brakes are illegal (WSB).

Light surface rust will be removed by the pads, not too sure about much more though It's the one thing that's put me off cast iron discs as I tend to use my bikes in all weathers year round.

Not too sure if any rust on the discs causes premature pad wear also

 

[bornagainbiker]

discs

thanks for the replies.

not too sure if they came from motorworks, but yes to the cast iron. Rust is light surface and does indeed vanish pretty quickly when pads are applied!!

Again, not too sure if the pad wear is affected? Hoping for some guidance in that direction.

B A B

 

[DavidHolmes]

Had these on my R80RT, and my K75S. IMHO vastly better in every respect than the OE ones - which as I understand it have only one reason for fitting - which is they are shiny.

Then they have to be drilled to work at all in the wet. Which reduces swept area and adds all manner of ridges and edges to bugger up the pads, increasing wear (both absolute and uniformity of).

If my GS OE ones ever wear out I will replace with iron ones. However this is becoming increasingly unlikely (and I have done 66k) 'cause the OE buggers seem to be so bloody slippery that nothing wears them out.

I heard a rumour that they were so shiny and slippery that BMW had invented a new brake system that applied massive servo power just to get the pads to grip at all.

Vanity over safety. Fecking Insanity.

 

[Steptoe]

watch out for your boots and the front of the engine turning rust coloured after you've been using them a while .

 

[ebbo]

Perhaps there Stealth Discs, they advertise in MCN, there discs are made from ‘low carbon steel’ They do coat them, but where the pads rub it comes straight off, as its supposed to, then they go rusty.
Talking to a steel supplier on the same subject, he said SS was around 5 times more expensive than low carbon steel, which is probably why Stealth use it rather than SS.

 

[ELIMINATOR]

Remember that car discs are all cast iron. No problems with them, mind you, most of the time they can't be seen.

 

[ebbo]

Car discs are usually cast iron but kept dry within the wheel.
Bike discs are completely exposed to the rain and the pads act like sponges. When you park up for the night after a wet ride home, the metal under the pad stays wet for a long time, often right through to the next day. This corrodes the shape of the pads in to the disc surface, after doing that a few times your new discs start to wear unevenly, the brake lever starts to pulse and your right back were you started with a knackered pair of discs.

It cost me £200+, for 2 sets cast discs & pads before I worked out what was going wrong 12 years ago. I fitted a new set of S/S disc for another £200 with a third set of pads and that was the end of my problems. And, to be honest, I didn’t find the bike stopped any better with cast discs.

Oh, and has been mentioned, cast discs make an unbelievable amount of mess to the front of your bike with rusty water spray.

 

[rugbug]

recently had a problem with cast iron set of discs I fitted last autumn.

My '02 Adv kept 'locking' and the front brake pots kept fusing around the discs due to the build up of brake dust in the calipers, which prevented the bike from rolling off the main stand and meant having to use brake clenaer fluid to realease them. Every day. Now have OE discs fitted and they have given me no grief whatsoever and excellent assistance from the supplier. I know the cast iron discs are popular and give very good bite, whihc is why I chose them in the first place, but I personally would not use them again because of the truly awful problems I had. Buyer beware I guess.

 

[DavidHolmes]

Car discs are usually cast iron but kept dry within the wheel.
Bike discs are completely exposed to the rain and the pads act like sponges.

Was it the CBX 550F that had those lovely fully enclosed inboard discs, anyone remember those?? (or are you all dead 'cause of lack of braking??)

PS Ebbo - Dont understand your "This corrodes the shape of the pads in to the disc surface" statement. Perhaps you could elaborate ? And specifically did you use the pads designed for Iron Discs or did you use the standard (designed to be used with s/s discs) OE BMW ones?

 

[ebbo]

David, after a wet ride home (25 miles) the bike was garaged overnight, then ridden to work and back the next day. On getting home, where the pads had been resting on the disc the previous night, the outline shape of the pads was still visible on the disc surface. I put a micrometer on the disc and it was just possible to measure the difference in thickness. Sorry can’t remember the measurements it was at least 12 years back.
As the weeks rolled by the discs started to look a mess of overlapping patterns and soon after that the brake pulsing came back, hardly surprising the state they were in.

The discs were made by P*M, I was invited to their works and given a tour round while they looked at my discs. They measured them and agreed they were knackered and gave me a new pair. The second pair went the same way as the first after a few months.

The discs were bought from Moto*works and fitted with new Ferodo pads as recommended at the time.

The second set of knackered discs was taken to an engineering firm in Bradford where one was successfully ground true; the other was improved but not right. Eventually the disc carriers were sold back to Moto*works and the discs were binned.

12 years later the BMW discs, though worn, were still going well.