Front Discs - Stainless OR Cast Iron

[dr nosh]

Well, as the title suggest, Which is best?

I know the CI will 'oxidise' in the damp and not look so pretty, but that aside, which will give the best overall performance?

Why am I asking?

I've currently got the 80ST wheels in pieces and rebuilding with stainless spokes, etc, and I had some thoughts about improving the front brake and fitting a new disc.

MW have both SS and CI available. I see that the CI offering does not have holes drilled in the rotor. Will this cause the rotor to ring/vibrate?

What is the beefit of the hole pattern in the standard rotor.

Also, MW have oversize 'flat' disc kits with a spacer to put the disc in the correct position and the kit also comes with an adaptor to enable use of the original caliper with the larger rotor.

How much braking improvement will I get for my (lots of) money?

Has anybody got any experience with these kits?

 

[(RIP) Arkwright]

I've put this kit on my Mono

which is a night and day improvement over the cast iron disc that came on it, (which always left the front wheel filthyand rusty when it got wet) but it is about £300!

The cut outs/holes are there to help the disc to cool, but when the rows of holes are on the same PCD the disc wears in ridges, hence the offset slots in this upgrade kit.

Anybody need an 'as new' cast iron disc?

 

[Rob Farmer]

Cast discs are shite. two of my airheads have three cast disks between them and they all warp when they get hot. Similar experience with previous bikes along with sintered pads rusting to disks and the rusty mess spread across your bike. On top of that I can't say theres any noticeable improvement in braking over stainless discs.

 

[Beemerboff]

Rob has summed the current position up nicely in his first four words-IMHO no need for any further discussion - and like Rob I have bikeS with CI disks and with SS.

 

[Mike the Bike]

-IMHO no need for any further discussion .

Further discussion.......

I changed to cast iron about 10,000 miles ago (the main reason was a warped stainless disk, and cast iron was the cheaper replacement). Anyway, the cast iron hasn't warped, and I would trust it more in the wet........ and I strangely quite like the rusty brown colour

 

[VAL. H.]

We've got one of each. Cast on Jills 100GS and I have a single stainless on my 80 (ex RT) Sidecar outfit. I'd say there's very little in the two and I'm supprised how good the single disc is on the outfit, although I do tend to massively over brake when I get back on my 1200

I my oppinion; if you are buying a new disc, don't wast your money on an OE one. Go for the bigger upgrade disc that Arkwright has. It's the easiest way you'll improve on what you've got


Val.

 

[Beemerboff]

Further discussion.......

I changed to cast iron about 10,000 miles ago (the main reason was a warped stainless disk, and cast iron was the cheaper replacement). Anyway, the cast iron hasn't warped, and I would trust it more in the wet........ and I strangely quite like the rusty brown colour

I've got rust on my stainless disk ---.

Disk and pad materials have changed a lot since this debate started - but if you get a contemporary SS disk and compatible HH rated pads it will be a long way better than any CI disk/ pad combo, wet or dry.

But forget stock, the el cheapo Kyoto disks from Wemoto work fine.

 

[electric_monk]

Further discussion.......

I changed to cast iron about 10,000 miles ago (the main reason was a warped stainless disk, and cast iron was the cheaper replacement). Anyway, the cast iron hasn't warped, and I would trust it more in the wet........ and I strangely quite like the rusty brown colour

+1. And I even managed to lock up the front wheel,(briefly before the Previa stopped me completely).
The rust is always worn off after a minute or so anyway.

 

[cookie]

I've put this kit on my Mono

which is a night and day improvement over the cast iron disc that came on it, (which always left the front wheel filthyand rusty when it got wet) but it is about £300!

the way to go IMO. had one on my PD, and now on my mono.

 

[ELIMINATOR]

http://www.buybrakes.com/brembo/faq.html#q19

Might be of interest. car based, but in principle similar.

 

[Mike the Bike]

,(briefly before the Previa stopped me completely)..

All bikes should be fitted with a Previa

 

[pete.keys]

which is a night and day improvement over the cast iron disc that came on it,

+1 As a fastish rider I found the standard brake life threatening! The larger rotor conversion Arkwright suggests are **much** better.

Even more money/better is one of these:

A Billet 6 pot calliper on the standard disk

This is what I use - my bike had a new cast iron disk and I managed to pick the calliper halp price and nearly new on fleabay.

 

[dr nosh]

Thanks chaps for your responses. Really useful info. I did search but could not find if this question had come up before. (Surely, it must have?).

Agree that the larger rotor is the way to go then.

@Arkwright2007 - Thanks for the picture. Thats very useful to see one actually installed.
Did the original length flexi hose fit OK without a rigid adaptor like the standard set up?

 

[(RIP) Arkwright]

Thanks chaps for your responses. Really useful info. I did search but could not find if this question had come up before. (Surely, it must have?).

Agree that the larger rotor is the way to go then.

@Arkwright2007 - Thanks for the picture. Thats very useful to see one actually installed.
Did the original length flexi hose fit OK without a rigid adaptor like the standard set up?

Mine came with a full length Goodrich braided hose which is normally tyrapped to the fork brace (unlike the picture) the big disc can use a slightly shorter hose, these things don't need the metal brake pipe, it's just an extra unnecessary joint.............just something else to go wrong.............like ABS and Servo's on later bikes!

 

[Benjamin M]

I fitted the 320mm disc as per Arkwright, and would concur that it makes a massive difference

 

[ebbo]

Cast iron discs

No1 problem.
It rains, your pads get wet, you park up the bike overnight or longer, pads corrode the shape of the pad in to the cast iron. As time goes by this gets worse, corrosion overlays corrosion, overlays corrosion till your brake lever starts to pulse, your back to square one

No2 problem
It rains, while your riding the disc’s sling off brown rusty water all over the front of the bike, it looks a mess

No2 problem
Your bike discs look a mess, they always look a mess, in fact they only look good from the first day you fit them to the first day it rains, after that they look a mess

Cast iron was all the rage some years back, truly a masterpiece of promotion thanks to the B*W club mag, Motor*orks and P*M cast discs

This is all just my opinion of course…

 

[(RIP) Tibs]

And how about my ol' R80/7 with its crappy ATE brakes? Still the same verdict?
I had been considering cast iron discs in a desperate bid to try and improve them a bit. I think you've just saved me a load of money....
Tibs

 

[ducatiparts.110mb]

Has anyone else found Iron discs to be very pad sensitive?

I had a set on my VTR years back and it took 3 sets of pads before I found a combination that worked - but then they were excellent.

I've also had them on 2 different Dukes - they were very poor indeed. In both cases I sold them on to someone else who was also taken in by the hype. When I reverted to standard the brakes improved.