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Old November 14th 17, 12:55 AM posted to rec.bicycles.tech
Ralph Barone[_4_]
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Posts: 106
Default Why do some forks and frames have brake rotor size limits?

John B. wrote:
On Mon, 13 Nov 2017 14:57:49 +0000 (UTC), Ralph Barone
wrote:

John B. wrote:
On Mon, 13 Nov 2017 03:41:11 +0000 (UTC), Ralph Barone
wrote:

John B. wrote:
On Mon, 13 Nov 2017 02:24:55 +0000 (UTC), Ralph Barone
wrote:

John B. wrote:
On Sun, 12 Nov 2017 12:10:38 -0500, Frank Krygowski
wrote:

On 11/11/2017 7:39 PM, Joerg wrote:

Yes, if 10" were more mainstream I'd probably have taken those but 8"
seems fine because I am not towing a brake-less trailer. A friend of
mine does though.

The extra cost is minimal. The adapters cost me $5.56 for both. The
rotors were around $23.70 each and the cost difference towards the
smaller versions will almost be made up by extended service life.

BTW there is a new bike shop in Placerville and one of the owners had
his MTB there the other day. 10" rotors on both wheels. He weighs less
than I do and said 8" was too iffy on some of his rides. These guys know
their stuff.

Let's look at the big picture. How do we decide which disc size is big
enough? And how do we decide how much how much tire puncture protection
is enough? How do we decide how bright one's lights need to be? How do
we decide how strong wheels need to be, how strong frames need to be, etc.?

In each of those categories (as well as in everything else being
designed) there is a tradeoff of benefits vs. detriments. Everyone else
recognizes this, and shoots for some optimal compromise. Example: I had
a flat about three days ago, but I prefer dealing with a few flats per
year rather than riding tires that noticeably slow me.

In each of those categories, Joerg's claim has been: if it's not as
robust as an automobile it's not good enough. But A) that's total
nonsense, because bikes and cars have very different uses and
parameters. And B) he really doesn't believe it anyway; otherwise he'd
be pedaling the de-motorized motorcycle that Sir Ridesalot has proposed
many times.

Joerg's real attitude is different. He's decided that the only
acceptable equipment is what he desires or approves, and that the entire
bicycle industry should cater to his wishes.

But in its wisdom, the bicycling industry realizes there's only one Joerg.

I don't think that you understand :-) You see, if it is "mine" then it
must be better then anyone. My brakes are better; my legs are
stronger; my beer is better; and on and on and on.

As an aside, I just measured the front discs on my wife's Honda Jazz
(I think it is called a "Fit"in the U.S.) and to my horror I find that
they are only 240mm (9.4") in diameter. As the nominal weight of the
car is about 1100 Kg (2400lb), as opposed to (probably) an all up
weight of less then 250 lbs for a bicycle, it is obvious that they
can't possibly be large enough to be safe. And Horrors, there isn't
any room to fit larger :-(
--
Cheers,

John B.

Bah... Think outside the box. You can probably rig up some cantilever rim
brakes on there. That will probably get you up to 14" or so. :-)

I probably could but I think I'd have to change the rims to a
different brand to get a wide enough rim for the caliper pads to be
effective.

Another thing that might enter into the equation. They refer to the
wheels as "Mag Wheels". If they are in fact magnesium wheels they I'd
have to be careful not to get them too hot. I knew that they made a
movie called "Blazing Saddles" and I suspect that "blazing brakes"
might be even more exciting :-(
--
Cheers,

John B.

It's a safety feature. When the magnesium catches on fire, it emits a
blinding white light that signals other road users to get the hell out of
your way.

So... no requirement for a helmet if using Mag wheels :-)

--
Cheers,

John B.


Well, to be fair, it's only a safety feature for other people, so you may
wish to keep the helmet on. Unless your line of thinking is that you would
prefer NOT to be conscious after crashing your flaming vehicle


I'm not sure I'd want to be conscious WHEN I'm crashing my flaming
vehicle :-)

--
Cheers,

John B.


That too!

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