gears...what does this mean?

[Kalidurga]

Here's what I don't get about the way cog sets are put together:

There's a small differential between the higher gears, say 11 through 17. When you get into the lower gears, 19 through 27 or 28 or 34 or whatever, there's a much bigger jump between gears, which makes for more difficult shifting under load. Wouldn't it make sense to have closer gears for the situations in which it's more difficult to shift, and spread the gears out more for the range in which it's easier to shift?

Or is that logical only to my own wacky, hill-challenged mind?

[dachshund]

Here's what I don't get about the way cog sets are put together:

There's a small differential between the higher gears, say 11 through 17. When you get into the lower gears, 19 through 27 or 28 or 34 or whatever, there's a much bigger jump between gears, which makes for more difficult shifting under load. Wouldn't it make sense to have closer gears for the situations in which it's more difficult to shift, and spread the gears out more for the range in which it's easier to shift?

Or is that logical only to my own wacky, hill-challenged mind?

That's a good point. I'm considering the 11-34 IRD cassette that SadieKate mentioned. 11-13-15-17-19-21-23-25-28-34. That's a big jump into the spinner gear. I haven't tried it "in person" yet.

[SadieKate]

Couple of things -

First, the percentage of change. 2 teeth is a much greater percentage of change in the small cogs

Secondly,practicality as you get into steep climbs. Typically you don't really care about one-two tooth increments in the big cogs. You just need a gear, any gear.

One tooth increments are far more noticeable when you're trying to fine tune a gear selection and cadence on flat roads when you're using the smaller cogs.

And soft pedaling enough to change cogs should be easy. It's shifting chainrings that is hard.

[Kalidurga]

And soft pedling enough to change cogs should be easy. It's shifting chainrings that is hard.

Well, then, in addition to being the Queen of Cross-Chaining, I must also be the Duchess of the Hard Uphill Shift

[ilima]

That's a good point. I'm considering the 11-34 IRD cassette that SadieKate mentioned. 11-13-15-17-19-21-23-25-28-34. That's a big jump into the spinner gear. I haven't tried it "in person" yet.

If you currently have a 'road' rear derailleur, you'll need to get a mountain rear derailleur to use that cassette.

Shimano road derailleurs--even if they are the long cage for a triple up front--only can handle 27 teeth max, so that's why the biggest road cassettes from Shimano go to 27. SRAM goes to 28. Now, as far as your wheel hub goes, Shimano and SRAM are interchangeable (not true of Campy). And I have heard that a Shimano RD can be pushed to 28.

For more teeth, like a cassette with 32 or 34 teeth, you must use a mountain derailleur. As far as shifting under load, one thing you can do is get a 'low-normal' RD. This will make the moving to easier gears (bigger cogs) easier, but it will change your right STI (controls the rear) to a configuration opposite of a road or top normal mtn derailleur.

[Kalidurga]

As far as shifting under load, one thing you can do is get a 'low-normal' RD. This will make the moving to easier gears (bigger cogs) easier, but it will change your right STI (controls the rear) to a configuration opposite of a road or top normal mtn derailleur.

Can you clarify what you mean by "it will change your right STI (controls the rear) to a configuration opposite of a road or top normal mtn derailleur"? "Low normal" and "top normal" are terms I don't think I've heard before.

Thanks

[HillSlugger]

I'm using the SRAM 11-28 with my Shimano long-cage RD and triple FD without any issues. Didn't even need to change the chain length.

[SadieKate]

http://en.wikipedia.org/wiki/Derailleur_gears

Relaxed position
High normal or top normal rear derailleurs return to the smallest sprocket on the cassette when no cable tension is applied.[4] Most Shimano mountain, all Shimano road, and all SRAM and Campagnolo derailleurs are high-normal designs.

Low normal or rapid rise rear derailleurs for mountain bikes are manufactured by Shimano. These derailleurs, introduced in 2004 in the XT and XTR groups maintain position over the largest sprocket on the cassette when no cable tension is applied.[5] On mountain bikes especially, this is an advantage because gear changes tend to be easier and quicker when changing in the spring weighted direction. Changing gears in the sprung direction requires only a light click on the control, and the spring will move the derailleur into place. In road racing the swiftest gear changes are required on the sprints to the finish line, hence high-normal types, which allow a quick change to a higher gear, have become the most common. In off-road cycling the most critical gear changes occur on difficult uphill sections when the rider must not only cope with the hard pedaling, but must also get into a critical riding position to maintain grip and must often cope with obstacles and difficult turns at the same time. In addition, they may be moving at a slow speed and it may be difficult to ease off pressure from the pedals without losing balance. Under such conditions being able to switch easily to a lower gear can make the difference between being able to tackle the section or having to get off and push, and thus the advantages of low-normal changers make them the best choice. From a user interface point of view, they shift opposite to other rear derailleurs. The user 'clicks' the index finger trigger to move to a larger sprocket, and pushes with the thumb trigger to select a smaller sprocket.

[SadieKate]

I personally run the high normal derailleur on my mtb because mud and debris can crap up the spring of the low normal and then you can't shift at all. It tends to be a love or it leave on normal or rapid rise. Reviews are on both ends of the spectrum.

[ilima]

Can you clarify what you mean by "it will change your right STI (controls the rear) to a configuration opposite of a road or top normal mtn derailleur"? "Low normal" and "top normal" are terms I don't think I've heard before.

Thanks

I only heard of the terms 'low normal' and 'top normal' recently, as I was cobbling components together for a commuter. SadieKate's post gives you an idea of the why behind a low normal RD, so I'll just explain the actual practical mechanics.

With the STI shifters on a road bike, shifting the little lever (not the whole big brake lever) will put you into a smaller ring, front and back. On the front (left shifter), that means shifting the little lever will make pedaling easier, but on the back (right shifter) it will make pedaling more difficult.

With my 'low normal' RD, the right shifter works opposite of that. Shifting just the little lever puts me into a bigger cog making pedaling easier.

Because I live on a big a$$ hill, I decided to go with the low normal for my commuter; mostly for kicks but also because I didn't want to be struggling up the steep (~20%!) pitches with a load and have trouble shifting into an easier gear. When I first start riding the bike I have to remember that the rear shifting is opposite of my road bike, but that's been pretty easy.

[Kalidurga]

This has been a great thread. I've been thinking since last year of building a new cyclocross bike with lower gears in the cog set, and the information here has been very helpful. Since I'm currently using Shimano Sora levers and plan to switch to Tiagra or better on the new bike and would have to get used to different shifters entirely, I wouldn't have the issue of adjusting to the RD shifting being "backwards" with a low-normal setup.

Thank you, ladies, very much.

[dachshund]

If you currently have a 'road' rear derailleur, you'll need to get a mountain rear derailleur to use that cassette.

Shimano road derailleurs--even if they are the long cage for a triple up front--only can handle 27 teeth max, so that's why the biggest road cassettes from Shimano go to 27. SRAM goes to 28. Now, as far as your wheel hub goes, Shimano and SRAM are interchangeable (not true of Campy). And I have heard that a Shimano RD can be pushed to 28.

For more teeth, like a cassette with 32 or 34 teeth, you must use a mountain derailleur. As far as shifting under load, one thing you can do is get a 'low-normal' RD. This will make the moving to easier gears (bigger cogs) easier, but it will change your right STI (controls the rear) to a configuration opposite of a road or top normal mtn derailleur.

The IRD 11-34 is also supposed to work with a Campy compact 34-50 and a medium cage derailleur.

[ilima]

The IRD 11-34 is also supposed to work with a Campy compact 34-50 and a medium cage derailleur.

That would have to be a medium cage mountain derailleur. If you had a triple up front you'd need a long cage mountain derailleur with that cassette.

A 'medium cage' road derailleur is for a triple up front and a road (i.e., no more than 27) cassette.

The maximum cog refers to the maximum number of teeth a RD can handle. For road, it's 27/28 and for mountain it's 34.

Capacity refers to the number of teeth between the hardest and easiest gears (biggest chainring minus smallest chainring) - (biggest cog minus smallest cog).

I don't know about the designations for Campy, but Shimano uses SS for road RDs meant for a double crankset. GS for R

[Tuckervill]

Well, it sort of is, except in the 70s they were talking about the total number of gear combinations, and now it refers just to the rear cassette.

That's the most forthright and direct explanation I've ever read. THANKS.

I know about cross chaining so I get why you don't have ex. 30 total gear combos.

whew, I can sleep tonight!

Karen

[SadieKate]

The IRD 11-34 is also supposed to work with a Campy compact 34-50 and a medium cage derailleur.

The Basics
http://bluecollarmtb.com/2007/06/19/...ity-explained/

So which Campy derailleur should you pick? Read the yellow box a little way down the page.
http://www.branfordbike.com/cgi-bin/...R_ID=647623406

Branford Bike is my "go to" place for all things Campy.