Increasing Gearing Range...

Bhima

When I crashed on Friday, the only damage to my bike was a crushed rear mech so, when I get a new one, i'm considering getting a mountain-bike one instead of a road one, so I can go up to 34t on the back.

If I get a 11-34 cassette, I'm looking at this, with my current chainrings:



If I get a 53/39 combination of chainrings when I need to replace my current chainrings, I'll get this:



At the moment, my lowest gear is 38.6 inches, so both give me a lot more room for spinning on the hills, which I prefer. I'm just unsure weather or not i'll get "gaps" where the jump from one gear to the next will be too extreme or not...

Would such setups feel really odd, because of the bigger gaps between sprocket sizes? I reckon if I can get better at lower cadence work, a broader range of spinning speeds will probably make this irrelevant but i'm just curious...

Here's my current setup, for comparison:



Can anyone see any problems with me trying one of those setups?

Is this cheaper than getting a tripple installed?

John.T

Cheaper than a triple but does leave a large hole between the 17 and 20 cogs. This is right where I spend most of my time. On the 50 ring all gaps above the 20 cog are more than 10" while the gaps down to the 34 are much less. I would try to close the smaller cog gaps up and increase the larger ones. If you need this wide a range of gears you are much better off with a triple. 53/39/30 with 12/27 gives a range from 116" to 29" while still being close enough for racing if you wanted.
If your present shifters will work a triple you would need mechs, chainset, cassette and chain.

Bhima

Right.

The hole between the 17/20 is quite big actually. I see it now.

But... :? If you spin at 100RPM, the speed difference is almost the same as the transitions you get when changing other gears...

So, would a LBS let me do a custom cassette which had less extreme transisions around the 18-25mph mark? Or would I have to buy individual sprockets off ebay etc...?

I'm thinking along the lines of this now:

(MPH @ 100 RPM)

John.T

I would base the rpm at 90. This is more realistic for any length of time. I would also bin the 11. If you need a 26" gear then you do not need a 119" one. I race with a 50/12 top gear and have not spun out yet. If I am going that fast I would rather freewheel and recover a bit. When climbing there is no way you will maintain 100 rpm so the lower gears need to be based on closer to 60rpm. It is very difficult to get all the gears you want and the larger range you want the more compromises you have to make. My ideal would be 50/36 with an 11 speed cassette straight through from 12 to 19 then 21/24/28. I could then do everything without changing cassettes.
For custom cassettes Marchisio (expensive) and Miche do them. Also TA and Mavic. There was a chap advertising in Cycling Weekly but I can not remember his name.

Bhima

I'm rarely down at 90RPM, unless on serious hills. I naturally prefer high cadences and 110 RPM+ for 15 minutes up hills is normal for me, but I feel my gears don't go low enough to do this once the gradient gets beyond a certain point.

I do occasionally spin the top gear out, but I don't think a 53t chainring is for me now, as 50t at a higher RPM would be more effective than a slower RPM. The 50/11 combo is quite effective at the moment I think...

It's not a fitness thing - I probably could handle a 53/11, it's more to do with the fact that I like high cadences (100-150) and my gears aren't good enough for this on hills at the moment.

oldwelshman

1 to 1 bottom gear? It's faster to get off and walk
The trouble with 11 to 34 is there are bound to be big gaps.
I think most people would find the big gaps in the high gears too much.
Not sure where you would need a 34 x 34 in uk or anywhere for that matter as you seem to be fit.
I race with 39 x 23 bottom but did use 36 x 27 for the Marmotte at certain points.

rickhotrod

Consider a 9 speed 52/42 13-34 (13,15,17,19,21,23,26,30,34).

You have to make the cassette up though.

Probably better to use a triple and 13-25 (13,14,15,16,17,19,21,23,25) cassette so that the gears are closely spaced. Notice the extra 14 and 16 sprockets.

Bhima

rickhotrod - that seems like a good setup! I may go with that one actually..

oldwelshman wrote:

Not sure where you would need a 34 x 34 in uk or anywhere for that matter as you seem to be fit.

Again, it's because I ride at stupidly high cadences all the time. (110-170) I don't expect anyone to understand; my riding style has confused almost everyone i've ridden with... It's quite unusual... :? So obviously, smaller gears might seem really extreme but up a 20% hill, it's just about right to feel comfortable.

maddog 2

I've ridden 11-32 on the Fred Whitton on a compact and although it worked well on the hills, the gaps were noticeable, even compared to a 12-27 I currently run. 11-34 would be more so, and I think would start to annoy you on regular rides.

Have a look at running/comparing 33/50 or maybe 33/48 on a 12/27 on Sheldon. That gives you a pretty low gear (33 inches) with a fair spread of gears. Okay you may spin out sometimes but it's a small price to pay in reality (unless you race).