Hole in my 2X9 Gearing!!

[patches]

Your front chainrings are the wrong size, i did the same thing also went 2X9 but you cant just take your big blade off, what is the use in that. You loose a lot of speed. I bought myself a (i think) 38 or 39 "middle blade" and a 26 small blade from starbike chainrings (brand Specialites TA)google it, its very nice rings!

yup! I got a new XTR crank... 1st thing I did was take those 3 fancy rings off (22T, 32T, 44T), sell them on the hub for a bargain... and bought some blackspire's (24T and 36T), a chainguide and a bashguard

[Skylark]

 

yup! I got a new XTR crank... 1st thing I did was take those 3 fancy rings off (22T, 32T, 44T), sell them on the hub for a bargain... and bought some blackspire's (24T and 36T), a chainguide and a bashguard

 

Whoa that is sick!! (what frame is that , see you got what looks like a DHX 5 in there?)

I think 24T/36T is the ultimate chainrings for 2X9 on a AM/singletrack bike , its pretty much all you'd need even for XC as the 36t gives you plenty topend. I went for a long ride now on the road and the 36t gave me plenty of speed even on some huge downhills. I just need the 24t though...

 

I'm also running a bashgaurd - have you got the chain tensioner to stop chain slap on jumps?

It looks like its a BB mount tensioner?

Edited January 19, 2012 by SkyLark

[patches]

Whoa that is sick!! (what frame is that , see you got what looks like a DHX 5 in there?)

I think 24T/36T is the ultimate chainrings for 2X9 on a AM/singletrack bike , its pretty much all you'd need even for XC as the 36t gives you plenty topend. I went for a long ride now on the road and the 36t gave me plenty of speed even on some huge downhills. I just need the 24t though...

 

I'm also running a bashgaurd - have you got the chain tensioner to stop chain slap on jumps?

It looks like its a BB mount tensioner?

 

thanks... it's a work in progress. The bike has yet to make its maiden voyage. Yup, that is a DHX 5 air in there. The frame is a Cannondale Moto 1 carbon (160mm travel). And yup that is a BB mount 2 ring tensioner there to keep the chain where it should be on jumps and the bumpy stuff. The alu version of this frame has ISCG tabs.

 

The tensioner is a Blackspire stinger (R236 on CRC).

 

but yeah... I still haven't ridden this beast... it's the first bike I'll own with a 2x9 setup. all my others are 1x9. So I'm looking forward to seeing what extra ability the 24T gives... as well as seeing if FD-tensioner combo is as reliable as a 1x9 chainguide. If it proves otherwise, I may go back to a 1x9 chainguide setup.

[Climate]

Check your technique because the way you riding is giving you the problem. You should have changed up to the bigger chainring before you reach the 3rd smallest cog.

 

Did you bother to read what I wrote : "If you have the 1.5 ratio and you are only dropping 1 ring at a time and you are not at either of the extreme ends of the cassette (ie first or last 3 cogs) you need to check out your technique - cause its not supposed to be like that.

From my understanding thats the whole point of the 1.5 ratio - it allows smooth transitions between rings without needing an immediate cog change"

 

Anyways you going off the plot here , we talking about the front chain ring ratios - All I know is that I have a hole when changing front chainrings thats 2 big to power through and its been pointed out that its due to the ratio between the 2 front chainrings, once my ratio is closer to 1.5 I'm confident I will be able to power through the hole.

 

Simple

 

I don't have a problem with my technique SkyLark ... I'm simply responding to your post where you stated that "If the ratio is not almost spot on, the change up or down between front chainrings will also need a change up or down on the back cogs to maintain cadence - and doing that everytime is a load of bollocks!!"

 

It should be simple ... but you're missing it! It won't matter whether you run 26/39 or 24/36 ... both ratios are 1:1.5, so the "holes" in your cadence will be the same. But to keep with your preferred ratio, let's assume that you're running 24/36 chainrings and are busy pedaling along in the middle cog on your cassette (you can't get further from the extreme ends of the cassette) and on the small ring, then your gear is 19~24 = 32.8 If you then change to the big ring, your gear will be 19~36 = 49.3 (which is a "hole", because you've made the equivalent of 2 cog changes on the casette, without a ring change). You now need to change up 1 cog on the casette to get to a gearing of 22~36 = 42.5 (which would effectively have been the same as changing down 1 cog on the cluster, without changing from the small ring (22~24 = 42.3) initially.

 

But if you think one needs to have changed up to the big ring before getting to the 3rd smallest cog on your cassette (as in your previous post), you're effectively limiting yourself to a third of your gear ratios ... because, by the same logic, you need to change down to the small ring, before you get to the 3rd largest cog on your cassette. And since you've only got 9 cogs back there, you can't use more than 3 of them?!!

 

The point I was trying to make in my original post however, was that even with the ideal chainring combination, you will always need to change a gear or 2 at the cassette, when you change gears to a different ring. So, if you've got enough power in the legs (as you suggest you have), then a "non-ideal" chainring ratio won't make a huge difference.

Edited January 20, 2012 by Climate

[Skylark]

I don't have a problem with my technique SkyLark ... I'm simply responding to your post where you stated that "If the ratio is not almost spot on, the change up or down between front chainrings will also need a change up or down on the back cogs to maintain cadence - and doing that everytime is a load of bollocks!!"

 

It should be simple ... but you're missing it! It won't matter whether you run 26/39 or 24/36 ... both ratios are 1:1.5, so the "holes" in your cadence will be the same. But to keep with your preferred ratio, let's assume that you're running 24/36 chainrings and are busy pedaling along in the middle cog on your cassette (you can't get further from the extreme ends of the cassette) and on the small ring, then your gear is 19~24 = 32.8 If you then change to the big ring, your gear will be 19~36 = 49.3 (which is a "hole", because you've made the equivalent of 2 cog changes on the casette, without a ring change). You now need to change up 1 cog on the casette to get to a gearing of 22~36 = 42.5 (which would effectively have been the same as changing down 1 cog on the cluster, without changing from the small ring (22~24 = 42.3) initially.

 

But if you think one needs to have changed up to the big ring before getting to the 3rd smallest cog on your cassette (as in your previous post), you're effectively limiting yourself to a third of your gear ratios ... because, by the same logic, you need to change down to the small ring, before you get to the 3rd largest cog on your cassette. And since you've only got 9 cogs back there, you can't use more than 3 of them?!!

 

The point I was trying to make in my original post however, was that even with the ideal chainring combination, you will always need to change a gear or 2 at the cassette, when you change gears to a different ring. So, if you've got enough power in the legs (as you suggest you have), then a "non-ideal" chainring ratio won't make a huge difference.

 

You right off the path and in the bushes walking into trees

You carry on carrying on

[Climate]

Here's the path bud ... you cut it (and all this time, I thought you were looking for advice)

 

"I'm running 2 X 9 speed :

Chainrings 36t & 22t

Cassette 11t to 34t

 

I'm happy with the range - excellent top speed and granny speed

Just theres a giant hole in the middle and I lose my cadence rythym...

I can use 7 cogs of the cassette in either chainring , I have noticed I am totally chewing up my bottom RD pulley tho.

Where should I ideally be changing up/down between the front rings - about 5 cogs from the top or bottom depending if I'm moving up or down?

 

I'm thinking of changing the big chainring to 34t or maybe 32t , but I think 32t may be a little drastic but that is what a typical middle ring would be.

But I may have a rather limited top speed with a 32t.

 

What you chaps think?"

Edited January 20, 2012 by Climate

[Skylark]

There's advice and then there's incoherence , both of them involve words

[Climate]

From that statement SkyLark, I guess you found your maths teachers incoherent as well ... that involves numbers

[NINER_boy]

There's advice and then there's incoherence , both of them involve words

 

Hi SkyLark

 

The "gap" will always be there, bigger and smaller jumps in rear cog tooth count changes up or down (2, 3 or 4 tooth jumps per change).

 

The point is, that the "gap" will be MORE accentuated with a bigger F ratio (bigger than a 1.5 ratio), and

LESS accentuated with a smaller F ratio (smaller that 1.5 ratio).

 

Now, you will have to find what works for you,

but the solution to your "gap" is a smaller ratio between your 2 F chainrings.

 

Cherio

[Skylark]

Well it looks like I'll be arguing with the internet today

 

Ok Climate let me re-phrase what I said just for your benefit :

 

There's advice and then there's incoherence , both of them involve words and numbers

[Skylark]

Hi SkyLark

 

The "gap" will always be there, bigger and smaller jumps in rear cog tooth count changes up or down (2, 3 or 4 tooth jumps per change).

 

The point is, that the "gap" will be MORE accentuated with a bigger F ratio (bigger than a 1.5 ratio), and

LESS accentuated with a smaller F ratio (smaller that 1.5 ratio).

 

Now, you will have to find what works for you,

but the solution to your "gap" is a smaller ratio between your 2 F chainrings.

 

Cherio

 

Exactly - you made that very good point over 2 pages back.... And I heard you!!!

Thanks NINER_boy for dealing with the issue at hand and with such wise succinctness

[Climate]

_{One of the questions in your original post SkyLark, was when to change from big to small ring and vice-versa ... on a 9-speed cassette with just 2 chainrings, you won't do any damage, if you still have 2 sprockets available on the side of the cassette opposite to the chainring currently engaged. So the damage to the idler gear on your RD remains unexplained ... perhaps you can explain what's happening there.}

Edited January 20, 2012 by Climate

[NINER_boy]

Pleasure

 

For me this is a "help and advice" forum, and not a slanting opportunity.

 

Glad I could assist

[Climate]

Well it looks like I'll be arguing with the internet today

 

Ok Climate let me re-phrase what I said just for your benefit :

 

There's advice and then there's incoherence , both of them involve words and numbers

 

Nope SkyLark ... just because you don't understand something, doesn't necessarily mean the statement was incoherent. So there's no need to re-phrase ... you just need to benefit

[Skylark]

Nope SkyLark ... just because you don't understand something, doesn't necessarily mean the statement was incoherent. So there's no need to re-phrase ... you just need to benefit

 

You would benefit from not making assumptions.

[Climate]

You would benefit from not making assumptions.

Maybe you can explain how I would benefit ... I've been gently trying to help you to understand that you can't get away from changing a gear at the back, if you change to a different gear in the front. It's been painful, even with spreadsheets to help get you on the same page ... so there are no assumptions made. That became clear when you started telling me I've got a problem with my gear changing technique (?) and in the same breath, continue to inform me that I should change to a different chainring, before I get down to the 3rd last sprocket on my cassette.

 

You're trying to solve a problem, which is why you posted the issue on this forum - remember? Now take a step back, read this again carefully and guess what ... you'll see that Niner_Boy and I have been saying exactly the same thing. Do you get it yet ...

Edited January 20, 2012 by Climate