650C Availability Issue (CD coating)

POB_London

I'm trying to get hold of some Open Pros, 32h in a 650C size. Mavic say they make them with a CD coating. This is what I want, because they're going on a fixie / disk utility bike, and I don't want milled braking surfaces. I'd much prefer a corrosion-proof coating.

Problem is that Chicken don't list them, and my local bike shop have been unable to get them for ages. Everyone keeps palming me off with the black ones with the braking surface. Anyone know if they are actually imported? If not, can I order them from a bike shop in France?

Don't want to ruin my lovely new bike build with the wrong rims.... 8)

giant_man

You could try Hewitt cycles, always very helpful and may have a pair in stock you never know ...

JWSurrey

I thought the CD had a machined braking surface that then had the corrosion proof coating over the top.
Mine are a gun metal grey colour (machined braking surfaces and all).

olr1

Aluminium alloy as used on bike rims is pretty much corrosion proof anyway isn't it? The ceramic coating used by Mavic is really only to improve the braking surface and make it a bit more hard wearing rather than 'corrosion proof' it.

For rims on a disc braked bike, just buy anything; it will make absolutely no difference to the longevity of the rim whether they are CD or not. Bare, milled aluminium rims develop an oxidative coating which is harder than the original alloy anyway, so I suspect fancy coatings on a non-braking surface would be a waste of money.

alfablue

Absolutely right, the CD coating is purely for rim brakes (with special pads) no benefot at all for a disc braked bike. Aluminium doesn't really corrode further once it is oxidised, you will have just as strong rims as CD coated ones.

John.T

CD is not ceramic. It is a surface treatment on the whole rim. Ceramic rims have a ceramic coating on the braking surfaces only.
Copy and paste from the Mavic website.

Couche Dure
A chimical anodization process that forms a micro-hardness on the surface of the rim
_Slows down wear application by braking
_Improves the characteristics of the aluminum alloy application and the rim last longer
_Makes it easier to build and balance the wheel

redddraggon

olr1 wrote:

Aluminium alloy as used on bike rims is pretty much corrosion proof anyway isn't it?

Aluminium is a very reactive metal, but because this it forms the thin low permeability membrane on the surface, this protects the Al

olr1 wrote:

Bare, milled aluminium rims develop an oxidative coating which is harder than the original alloy anyway.

Aye, the oxidative coating is alumina which is a ceramic

So I'd say either of the rims would be fine, no need to go for the special coated rims.

John.T

The untreated braking surfaces on the normal coloured rims will get an oxidised surface after a while but if you get too much salt on them they will get pitted and look terrible. Braking normally stops this from happening. Get the CDs if you can. They will look good for years longer on a disc set up. As you say Mavic do list them so someone must be able to get them. As giant mancp says 'try Hewitts'

POB_London

Thanks a lot guys. I was just beginning to question my own logic when the debate came back around.

A CD rim is much less prone to surface attack (say from salt) than a milled ally surface. Since this bike will spend a lot of it's life on grotty roads covered in cr@p then this has a certain appeal.

I'm not talking about the ceramic, which is a different beast altogether.

PS > I should also admit at this stage that the looks of a rim without a prepared braking surface are far superior. With a rim brake, coated rims eventually look terrible (remember the way old GP4s used to show all your nipple stresses as variations in brake-block wear!?).

Will try and track them down. Hewitt's looking into it for me. Otherwise I'll break out the GCSE french and order some from a Frenchie bike shop and get them delivered.

POB_London

Ordered them from a French bike shop in Paris. I'm going over this weekend anyway, so I didn't think it would be a problem... unfortunately they wanted a deposit over the phone and no-one spoke a word of English. It also took a while to explain the circumstances; they couldn't understand that the UK importer isn't interested in special orders or bringing in minority items like these.....

Will keep you posted about how things turn out at Cycles Laurent, by all accounts the Condor of Paris. :roll:

Steve928

Parker International list 650C CDs in 32h. £29 ech.

Don't know if they actually have any though.

POB_London

Steve - lots of online places have them listed, but Chicke stopped importing them ages ago and no-one has any stock. I ordered a pair from Rutland Cycles at the beginning of September and they told me last week that the importer wouldn't help.

:-)