Darren,
No. I am decidedly not talking about a shifting pattern where you have
to keep double shifting the front and rear derailers. I am talking
about simplifying the shifting pattern when you do have to shift the
front derailler. At the risk of overstating what you already know...
There are 4 variable that must be considered when selecting gearing.
First, how wide a range do you want, second how much distance between
gears are you willing to tolerate, third, how much shifting do you
have to do to get from one gear to the next, and fourth, finally, what
are your individual preferences amongst the first three. I can't
speak at all to the last for you but can only encourage you to
consider all 4 in making decisions.
I have a strong preference to have a fairly consistent difference of
about 10 % between gears and this eliminates the wide range cassetes
like the 8 spd 12x 32 you use. I use a 9 spd. 12x27. I also have a
strong preference to have a simple shifting pattern. Together, this
means i am forced to make some comprimises about how wide a range I
can use. When shifting between rings a difference of ten teeth will
generally put the next gear one rear shift away. This works well with
doubles but is too limiting for triples. So for triples I typically
use 46x36x26. Doubles get more complicated. I find that a difference
of 12 or 16 leaves me searching for the next gear, while a difference
of 14 puts me two cogs away from the next gear.
Here's my favorite set up for a double:
12 13 14 15 17 19 21 24 27
48 108 100 93 86 76 68 62 54 X
34 X 71 66 61 54 48 44 38 34
This gives a pretty big high gear, a manageable low gear for most
situations and an easy shifting pattern. I can slide up or down the
cog set with about 10 % between gears and when I need to shift rings,
I can know that I am 2 cogs from the next gear, e.g from 54 down to 48
or 62 down to 54.
A 46 X 30 looks more complicated:
12 13 14 15 17 19 21 24 27
46 104 96 89 83 73 65 59 52 x
30 x 62 58 54 48 43 39 34 30
The next gear is now three cogs away. E.G. from 59 to 54.
Certainly doable, but you might want to think about it before you go
that wide.
Here's what a 44 X 30 looks like.
12 13 14 15 17 19 21 24 27
44 99 91 85 79 70 63 57 50 X
30 X 62 58 54 48 43 39 34 30
In this case the two cog shift is a little more than my ideal of 10%,
(e. g. 50 to 43 or 54 to 63) but still perhaps acceptable.
For me, I would be willing to give up one half gear at the top (99 vs
104) to get a simpler shifting pattern. Others will disagree.
BTW, there are web sites that can help in calculating gear ratios, but
its pretty easy to set up a spreadsheet like Numbers or Excel to do
this. The formualis simplify ( Ring/cog) X 27. This is an imperfect
approximation, but good enough for government work!
Perfection is not reachable nor worth worrying about. Try what looks
like the best trade-off for you and change it if you feel you need to.
Michael
On Jun 12, 3:07 am, Darren Stone <dst...@bitmason.com> wrote:
> Hi Michael. I just read up on the White VBC road crank. It's quite
> beautiful also. It's a possibility. Thank you.
>
> I'm not sure if I'm understanding the 44-30 logic, but if it's to give
> a superior shift pattern that requires regular double shifts, then I
> may not enjoy it. I'm shooting for a wide-range double so I get a
> simple-minded "95% of the time ring", rowing through my 8 cogs (12-32)
> in the back, with a bail-out granny ring available when necessary.
> Mad up/down hills being the 5% exceptions that require double shifts.
>
> Singlespeeding has clearly rotted my brain!! I embrace any gear range
> now and don't care about step size! Thanks for doing the math,
> though; I appreciate it. It caused me to work through the
> possibilities again. On my Saluki, a 46-12 gives me 99 g.i. (it's
> shod with 650A) and even loaded up I think a 30-32 should be great for
> climbs.
>
> -Darren.
>
> On Jun 11, 5:43 pm, MichaelH <mhech...@gmail.com> wrote:
>
> > Two suggestions. Why don't you take a look at the White VBC crank
> > before you buy. They have a very low Q and lots of ring flexibility.
> > Second, one problem with a difference of 16 between rings is that once
> > you shift rings you are many cogs away from the next gear, and in fact
> > there really isn't a good pattern when you shift rings. A difference
> > of 14 will put you exactly two cogs away from the next gear of about +
> > or - 10 % almost anywhere on the cassette. So you might want to
> > consider a 44 / 30. You give up a couple of gear inches at the top,
> > but get a smoother pattern. A 30x32 is a small enough gear for most
> > riders to get up most hills without a touring load, and the 44x12 (99
> > g.i.) will allow you to spin up to 30 mph; after that you can tuck
> > and coast.
>
> > Michael
>
> > On Jun 11, 3:58 pm, Darren Stone <dst...@bitmason.com> wrote:
>
> > > Hi. I have a tech crankarm/BB/spindle question that could use some
> > > expert insight.
>
> > > Current: Saluki w/ Sugino 50-40-26 triple & Phil BB. It's fine but I
> > > definitely notice the "width"/tread/q-factor. My other rides are all
> > > singlespeeds, so that's to be expected. The triple is decadent but
> > > I'm seriously thinking about moving to a wide-range double. I spend
> > > most of my time in the 40 ring, likely in the 43 to 86 inch range.
> > > I've done the math and a 46-30 double might suit my riding needs. I'd
> > > like to keep my 8 speed 12-32 XT cassette, Campy Record 9-speed chain,
> > > and friction shift. It's all working well.
>
> > > So what I'm considering are the TA Pro 5 Vis cranks. Apparently,
> > > they're narrower than most cranksets so that's very appealing.
> > > Aesthetically, gorgeous. No reason to change the Phil BB, I assume.
> > > But what do I need to measure/scrutinize/order now before I make the
> > > switch? I understand chainline but some of the BB width and spindle
> > > length specs confuse me.
>
> > > Open to opinions. Cheers!
>
> > > -Darren.
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