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 Post subject: how to make 2x9 work...?
PostPosted: Wed Apr 28, 2004 10:47 am 
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Joined: Thu Apr 08, 2004 6:19 am
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Location: nr Derby, UK
I've been really tempted to try a 2x9 setup, but have been trying to figure out how you guys (well, those that use it) get the shifting to work?
Looking at old posts, obviously i have to take the granny ring off (or just get a 2x9 specific crankset. methinks the better option) and make sure the chain-line is shifted a bit by using a shorter BB, but how does the whole front mech/shifting thing work? It's pretty obvious the rear stays as i have it, maybe with a different cassette, but what about the front (i prefer the sh*mano sti type, but not this new integrated stuff)

do you:
a: keep using the same shifter and derailleur and just change the end stops?
b: use a road 'double' derailleur with the same or different shifter?
c: i saw an sti kit to convert a road 2x9 to flat bars somewhere--steal the left pod out of that? (but in conjuntion with what derailleur...hmm..)

i couldn't really tell how people were making this work, apart from that it could be finicky for some


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 Post subject:
PostPosted: Wed Apr 28, 2004 12:25 pm 
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Location: Sydney, Australia
I can't say I've done it, but try adjusting the limits on the derailure.
I know they can be adjusted to make 2*9 into 1*9.

This is the MTB forum, are you working on a road or MTB? What bars/rings are you working with?

Brian


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 Post subject:
Posted: Wed Apr 28, 2004 12:25 pm 


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 Post subject: sorry, mtb 2x9
PostPosted: Wed Apr 28, 2004 3:03 pm 
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Location: nr Derby, UK
i'm having a look at converting my xc 3x9 setup to 2x9 because i don't ever seem to use the granny ring, even on steep climbs. keeping the gearing sensible would probably mean 42/30 up front and 12-34 on the back. (44/32/22 F and 12-34 R at the mo')
this would be on flat bars, standard mtb sizing and all that.


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 Post subject:
PostPosted: Wed Apr 28, 2004 3:44 pm 
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Location: Oxford - UK
Have you looked into the options of:

2x9 and 12-34 rear against

3x9 and 11-23 rear?

11-23 Dura Ace Cassette comes in at 156g
12-34 XT Cassette comes in at 300g

What I dont know is the weight of your granny ring.
An XT Granny ring weighs ONLY 20g!!!

Do you want to save 144g or 20g?

It seems to me that changing the rear cassette is easier than a new BB and re-alligning to get 2x9.

Just my 2 Euros!


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 Post subject:
PostPosted: Wed Apr 28, 2004 4:35 pm 
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Location: nr Derby, UK
it's all a bit hypothetical at the moment, so i should probably have been looking at both angles all along. thanks!

trying to balance ease of use against weight saving is always going to be hard with this; as much as i want the bike as light as possible, it still has to work consistently. also hypothetical as, though i'll try it out on my current ride, it's really for the new bike that's in the works

i've always found front mechs/shifting to be more problematic (not to mention slower-shifting) than the rear, even though the 9-speed has never been as bulletproof as 8-speed. this is why i'm more tempted to play with things at this end even if the weight saving is slightly less (more on this later). the idea is, if something's more likely to go wrong, i'd like to be using it less.

however, i do see the merits of the DA cassette idea. that, and i've seen more people using it than 2x9.

so, onto the weight savings

my current 12-34 XTR is round about 255g (lack of access to decent scale gives poor precision)
DA seems to be mostly in the 150-160g range
so that saves 100g-ish plus, say 35g from the rear mech. close to your figure in total

typical shimano daftness means i can't put a different BB with my '03 XT crank (as far as i can tell), so i'll just pretend this was on my new bike
FRM Cu-2-M Integral claims 755, total as a double, and 770, total as a triple (15g saved) (or ~40g vs. XTR-960)
other combinations are similar.

so, i may not be saving that much weight, but to me this is kind of like the argument of tubed v. tubeless: there are other advantages and disadvantages that aren't so clear-cut. i know i may seem a bit set in what i want to do, but i'd still like to hear what others think


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 Post subject:
PostPosted: Wed Apr 28, 2004 5:06 pm 
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Location: Oxford - UK
Another Dura Ace advantage is the weight saving in shortening your chain length. When you move to 11-23 at the back, you have 11 less teeth.

A chain fitting a 12-34 rear cassette will weigh 292g.
A chain fitting a 11-23 rear cassette will weigh 268g.

I'm a big fan of 3x9 with DA upgrade Vs 2x9 with 12-34 XTR

To do it you need to have good fitness for long steep uphills.


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 Post subject:
PostPosted: Wed Apr 28, 2004 6:22 pm 
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Location: nr Derby, UK
hmm.. hadn't thought of that one. makes it look even better from the weight saving point of view.

you mean more fit to do the DA option, right? if i've sussed the ratios, the 11-23 with standard 44/32/22 chainrings actually gives you a 'taller' lowest gear than the 2x9 setup. doesn't bother me, just trying to figure out which one you mean

12-25 DA gives the same gear spread as the 2x9, approximately


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 Post subject:
PostPosted: Wed Apr 28, 2004 6:40 pm 
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Location: Oxford - UK
Not sure what you intended use will be for your set-up.

I do 90 to 95% road miles on my Spec M5 HT.

Change the tyres and I'm off road. I'm fit enought not to need 11-32 at the back.

I need the 11 smallest cog at the back.

alternative is to go for whatever largest cog you want and add a 11 tooth XT cog.


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 Post subject:
PostPosted: Wed Apr 28, 2004 9:34 pm 
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You may be interested in this set-up:

Middleburn RS8 with XC Duo rings (29/42) plus DA 12-27 cassette.

I've been running this for ages now and its great. You can spend longer in the big ring, as you have a better chainline to access the top part of the block, and get smooth changes to your lower gears under pressure as you haven't got to worry about changing to the granny. I still get low gears with the 29 inner (you can spec a 11-34 or 12-34 or whatever) as you would with a normal set up. The XC Duo is also available as a 32/44, with the inner being the spider for the outer. There's a few pics of it on my bike here: http://www.gonemountainbiking.com

Its nice and light too, and is much less prone to getting cacked up with mud, which is nice :wink:

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Middle ring all the way


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 Post subject:
PostPosted: Wed Apr 28, 2004 9:50 pm 
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I'm running the 2 x 9 also. And after 3 years of use with shimano. Just remove the granny and take option a! A shorter bb isn't needed when your on a budget... The sti pods work great with this setup.

I'm on a Sram diet now and this is totally awesome! A slightly shorter bb and just two rings up front. It really feels good!

Good luck!

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'Tape was made to wrap your GF's gifts, NOT hold a freakin tire on.'

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a bit more detail about you - height weight etc,
I am 185cm and about 76kg. I like pina colada's and getting caught in the rain.


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 Post subject:
PostPosted: Wed Apr 28, 2004 10:32 pm 
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Location: The Netherlands - Europe
just removing the granny, without shortening the BB does nothing really... apart from losing some grams for the ring. The whole point of 2x9 is what Ian is talking about: Improved chainline.

Lloyd; Check this article: http://www.light-bikes.com/articles/drivetrain.asp ; the section about 2x9 pretty much says it all.


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 Post subject:
PostPosted: Thu Apr 29, 2004 12:56 am 
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Location: Sydney, Australia
20g improvement from the granny is pretty frugal.

An 11*23 would give you a ratio of 12.4
The 30*32 you mentioned would give a ratio of 24.5

3*9(DA) would still be a better climbing ratio with the weight loss an advantage.

Go for the real weight loss and change the cassette and chain (RD optional).

Brian


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 Post subject:
PostPosted: Thu Apr 29, 2004 1:16 am 
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Location: nr Derby, UK
i do about 85-90% off road, of which about 40% is racing, so a top-end of 44/11 is probably pushing things a bit, as i rarely make it up to the 44/12 i've got at the moment unless i'm on a particularly smooth fireroad.

that article was exactly what i was after, though it still doesn't really answer the question of what to put up on the bars to shift with; using the standard sti's seems like a bit of a bodge in that department. it does look like using a standard front mech will work, though.

Ian, that is a gorgeous bike! the middleburn setup looks really trick, too. two questions about the setup, though. does the 'standard' (high-band)swing mech you've got on there offer more adjustment of the end stops than a 'top' (low-band) swing type? what sort of shifter is that you're using to control the front mech? it looks not only purpose-built but very light.

i know it's not losing as much weight as the DA cassette, but most people seem to miss the point that using a purpose-built setup like the middleburn is going to lose more than just the mass of the granny and its screws. that, and the lowest gear i realistically use at the moment is 32F/34R (1.06) anyway.

how are you calculating ratios Brian? there is no way my legs are spinning 24 times faster than the wheels!


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 Post subject:
PostPosted: Thu Apr 29, 2004 1:30 am 
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Location: Sydney, Australia
Ratios are calculated by:

Dividing the size of your Front Ring (teeth) by the size of the rear cog, multiplied by the diameter of your wheel (26). Trackies use it alot and it good to compare Road and MTB gearing.

DA9 also comes in a 12/23 cassette

I push a 46*11 no problem (175m cranks) on the road and occassionally in races.

Brian


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 Post subject:
PostPosted: Thu Apr 29, 2004 9:24 am 
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LloydP wrote:
Ian, that is a gorgeous bike! the middleburn setup looks really trick, too. two questions about the setup, though. does the 'standard' (high-band)swing mech you've got on there offer more adjustment of the end stops than a 'top' (low-band) swing type? what sort of shifter is that you're using to control the front mech? it looks not only purpose-built but very light.


The Pace frame will only take this type of mech for a 42t ring, as a top swing mech won't fit lower due to the frame design with the carbon seat tube. A top swing mechs would work OK with 44t rings though. For the shifters, I use Forge-MTB mounts (sadly no longer available) with DA bar end 9sp shifters. The thumbies are handy for tweaking the position of mech cage to eliminate chain rub.

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 Post subject:
Posted: Thu Apr 29, 2004 9:24 am 


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