Rotor material?

[Joerg]

Some rotors are sold for "resin pads only", others do not list
restrictions. What is the difference in materials?

I am using ceramic based pads not normally sold at the LBS, supposedly
similar to what motorcycles have. Because they give me best results.

Other questions while at it:

My rotors are formally 7" and 6". Can I use 180mm and 160mm instead? The
7" one on my MTB actually measures about 185mm. I'd hate to have to
grind down the spacer but might have to because 7" is more rare.

Does anyone know what the raw rotors foer custom-laser deals are called?
Couldn't find any on EBay. Ideally I'd want rotors that are solid like
on motor vehicles, for better heat tolerance. Weight doesn't matter.

--
Regards, Joerg

http://www.analogconsultants.com/

[Joerg]

Add-on: I am also looking for at least 2.2mm thickness like the
originals from Promax. The newer ones from Promax only have 2mm and also
a weird wavy design:

http://i.ebayimg.com/images/g/qjAAAOxyIPNTc4rj/s-l1600.jpg

[jbeattie]

Hayes makes the 5-7" rotors. https://www.universalcycles.com/shopping/product_details.php?id=5018 You could always go with a bigger metric size and add spacers rather than going smaller and grinding down your current bracket. You would have to get longer bolts probably. This would also accommodate your gnarly riding style and need for maximum braking power. Go big or go home!

I use sintered metalic pads because they last a long time and work well in wet conditions. I am not familiar with the ceramic/metal pads except that I have seen them on the rack.

All one piece rotors I know of are SS, although you can buy CF rotors. Magura (and I think Avid) makes thick rotors (2mm) that are supposed to be good at shedding heat, but I don't know of anyone who makes them thicker than that.
You'll have to do some detective work.

-- Jay Beattie.

[Joerg]

The data on those is a bit unreliable. For example, here the same P/N
98-17551 rotor is listed as 160mm which isn't 6":

https://www.worldwidecyclery.com/collections/hayes/products/hayes-v6-160mm-rotor-with-hardware

I believe Hayes rotors are also only 1.9mm thick and I'd be through that
in a jiffy.

It was similar when I bought a BB for my road bike. Most US dealers
listed it as JIS taper which is what I needed and most UK dealers listed
the same P/N as non-JIS. Shimano had no "Contact us" on their home page.
Luckily it ended up being JIS.

> You could always go with a bigger metric size and add spacers rather
> than going smaller and grinding down your current bracket. You would
> have to get longer bolts probably. This would also accommodate your
> gnarly riding style and need for maximum braking power. Go big or go
> home!
>

Indeed. I am thinking about upping the front to 203mm which equates to a
true 8". With 7" you always have the discrepancy and a standard 180mm
rotor is 5mm too small so I'd have no choice but to grind off.

My style isn't so gnarly but we have long steep descents here. A friend
who rode ahead of me lost his front brake before the last sharp turn
once. That was a real white-knuckle situation. It was weird, he had 8"
versus my 7" and weighs less, same route and speed.

> I use sintered metalic pads because they last a long time and work
> well in wet conditions. I am not familiar with the ceramic/metal pads
> except that I have seen them on the rack.
>

The ceramic-based ones last much longer for me. But who knows, maybe the
sintered ones I used before didn't like wet rides too much. The only
downside is a sandpaper sound when they are applied for a long descent
and become hot. Goes away once cooled off.

> All one piece rotors I know of are SS, although you can buy CF
> rotors.

There must be different steel in Shimano SM-RT56 versus SM-RT66 rotors
because they do not allow the RT56 to be operated with anything other
than resin pads.


> ... Magura (and I think Avid) makes thick rotors (2mm) that are

> supposed to be good at shedding heat, but I don't know of anyone who
> makes them thicker than that. You'll have to do some detective work.
>

It'll be tough because the thickness is almost never listed. There used
to be custom shops where you could have a rotor with a laser-cut
"Beattie Racing" made. One of them had 3mm thick versions and I could
ask them for raw rotors (full discs, no gaps, like on many motor
vehicles). However, seems they are gone.

I wish the original thick Promax rotors were still available. They are
really good but the micrometer shows them down to 1.75mm in front and
1.65mm in back. So they need to be replaced soon.

[James]

On 06/10/17 09:41, jbeattie wrote:

>
> All one piece rotors I know of are SS, although you can buy CF
> rotors. Magura (and I think Avid) makes thick rotors (2mm) that are
> supposed to be good at shedding heat, but I don't know of anyone who
> makes them thicker than that. You'll have to do some detective work.
>
>

I wouldn't have guessed that slightly thicker rotors would be
appreciably better at "shedding heat".

--
JS

[Frank Krygowski]

Agreed. Initial temperature rise might be slightly less rapid due to the
larger mass. Once steady state was reached, as on a long descent, I
doubt it would make any difference at all. Surface area is what matters
then, and the difference in surface area would be negligible.

--
- Frank Krygowski

[Sir Ridesalot]

160mm is 6.299212598425197. Does that extra .2992125... make that much of a difference?

Cheers

[John B.]

It might effect the location of the brake on the fork as it would mean
that the 160mm brake was about .149" larger radius but I do see brake
rotors listed as "6 inch (160mm)" or "7inch (170mm)" which sort of
makes one wonder how critical the measurement is.
--
Cheers,

John B.

[AMuzi]

A 160mm rotor is 160mm edge to edge.

It's 'about six inches' in the same way that a 700-25 is
about 27". A 27x1-1/4 is about 27-1/2 inches but you can't
call it that because 584mm 26-inch systems, which are
smaller than 630mm 27", already own that moniker.

Yes, it's nonsensical. Zen is acceptance. Carry on.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

[cycl...@gmail.com]

On MTB's on difficult descents the rotors are almost red-hot. Since I've never seen rims that hot I can only assume that the disks allow you to hang it out a lot further.

[Joerg]

It can result in a large part of the brake pads never making contact
with the rotor. Another likely result would be a horrid noise because
unfortunately most bike rotors are wavy. You don't want that on a trail
with horses up front.

[Joerg]

On 2017-10-06 06:51, cycl...@gmail.com wrote:
> On Thursday, October 5, 2017 at 6:37:10 PM UTC-7, James wrote:
>> On 06/10/17 09:41, jbeattie wrote:
>>
>>>
>>> All one piece rotors I know of are SS, although you can buy CF
>>> rotors. Magura (and I think Avid) makes thick rotors (2mm) that
>>> are supposed to be good at shedding heat, but I don't know of
>>> anyone who makes them thicker than that. You'll have to do some
>>> detective work.
>>>
>>>
>>
>> I wouldn't have guessed that slightly thicker rotors would be
>> appreciably better at "shedding heat".
>

It would also be better if they didn't have so much material cut out for
the weight weenies. So far I haven't been able to find a rotor that is
completely solid or at least towards the center. Like motor vehicle
rotors are.

> On MTB's on difficult descents the rotors are almost red-hot. Since
> I've never seen rims that hot I can only assume that the disks allow
> you to hang it out a lot further.
>

Oh yeah.

https://www.youtube.com/watch?v=2S1KoZnIjbg

The guy should reverse the skewer. Not good to have the release where
the rotor is.

[AMuzi]

When I was young, The Ancients locked QR skewers randomly,
with many Italians on the right, most French left. Fashion
moved to nearly all left around 1970. Through at least 1973
I was uncrating new bikes with skewer handle right side
(Garlatti, Cinelli) What difference could it make, aside
from rider's personal convenience/opinion/fashion?

(my beef is skewers clamped down hard over a fork blade so I
can't get a finger under them)

[Joerg]

Normally it doesn't matter but with disc brakes it does. Some skewer
handles are designed wrong in that they can swing past 180 degrees. Or
they don't but for some reason the whole thing becomes lose and turns.
If that handle gets into the front rotor it can lock up the wheel and
the bike will likely eject you over the handlebar.

> (my beef is skewers clamped down hard over a fork blade so I can't get a
> finger under them)
>

That's what I do. One has to always keep in mind that crashes happen and
how to prevent unnecessary injuries. In a pinch a tire lever will help
pull it and since a flat is the main reason to open a skewer you'd have
to get that out anyhow.

[Sir Ridesalot]

Easier for wheel replacement during a big race?

Cheers

[AMuzi]

> Easier for wheel replacement during a big race?

In theory maybe but I remove and reinstall wheels all day
long. Yes, you can slip something under it and take care not
to scratch the finish but what's better about that? Slow
Release is not a feature.

p.s. Almost all skewers need lubrication. They are
frequently sticky binding and inefficient, giving low
clamping force with firm hand pressure.

[Frank Krygowski]

On 10/7/2017 11:29 AM, AMuzi wrote:
>
>
> p.s. Almost all skewers need lubrication. They are frequently sticky
> binding and inefficient, giving low clamping force with firm hand pressure.

Yep. Almost every time I ride my touring bike, I leave right from my
house, instead of tossing it into or onto a car. So I hadn't had the
front wheel out for many months.

A few days ago, I had to load it into a car. I almost couldn't get the
front quick release to open. It took three tries and all my strength.

I suppose, as with stems and seatposts, it makes sense to periodically
move and lubricate every bike part that's supposed to move.

--
- Frank Krygowski

[Ian Field]

"Joerg" <ne...@analogconsultants.com> wrote in message
news:f3nfp8...@mid.individual.net...

> Some rotors are sold for "resin pads only", others do not list
> restrictions. What is the difference in materials?
>
> I am using ceramic based pads not normally sold at the LBS, supposedly
> similar to what motorcycles have. Because they give me best results.

Stainless is pretty universal on motorcycles because it looks pretty - cast
iron works better as a brake rotor.

cast iron is unlikely to be suitable for the thin fragile rotors on
bicycles.

most bicycle rotors I've seen appear to be some form of stainless. There's a
pretty much infinite range of chrome/ferrous ratios. there's probably
various alloys with nickel and or vanadium etc.

[James]

Since bicycle rims have enormous cooling surface area compared to a disc
rotor, it is obvious why they don't get so hot yet can still provide
adequate braking performance.

And let's face it, aluminium tends to phase change from solid to liquid
without appearing "red hot".

--
JS

[cycl...@gmail.com]

With LARGE disks on my Trek Hi-Fi I've descended a hill where at the bottom the disks were smoking to the point where I worried about just that thing.

[Frank Krygowski]

... which adds some challenge when trying to weld it.

I've not yet succeed in welding aluminum by oxy-acetylene, although my
weak defense is that I haven't tried it more than a couple times.

Still, I admire anyone who can do that well.

--
- Frank Krygowski

[cycl...@gmail.com]

And the modern bicycle rim is very likely to be 30 mm deep or deeper for aero purposes. Lots of material and with a very low coefficient of conduction.

[John B.]

It is easier then it first appears. We used to use a flux but cleaning
and preheating was still important, But other then that the technique
is very similar to TIG welding it. In fact a properly gas welded joint
will look very much like a TIG welded joint - the so called stack of
dimes appearance.
--
Cheers,

John B.