Talk:Bicycle gearing

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Contents 1 Different language in gearing? 2 Consistency? 3 Rewrite December 2, 2005 4 Why not use real ratios? 5 Drivetrain efficiency?

[edit] Different language in gearing?

Langton, this is a great start for the article, thanks! However, among road/racing cyclists it is more commonplace to hear the chainring/cog combination instead of gear-inches. For example, people would refer to "39x17" or "53x13" . Or, when discussion bicycles they would say, "50x43 front and 11-23 rear". I think the use of this other language should also be accomodated, since for most racing bicycles that I have seen, the "53/39" front combo is pretty much the de facto gearing choice, with the compact options "50/34" or "50/36" being distant options. Any thoughts on how to accomodate the different lingos? Among racers on my amateur team, I would say that only 3-4 out of 14 would even know the gear-inches numbers of their gears, and this is because they also ride a fixed gear bicycle, which use a wider variety of front chainring sizes for obvious reasons. Julius.kusuma 18:23, 23 November 2005 (UTC)

Hi Julius, thanks for your comment (I am more comfortable with you using my first name: Murray).

There is a section specifically for racing cycle gears (which I am not competent to write), so go right ahead and do this section with your notation. A usage such as "50/39 front and 11-23 rear" does assume that everyone is using the same size rear wheel - there are 5 bicycles in my household, with 4 different wheel sizes between them - the notations I've used (mainly gear-inches) allow for this variation in wheel size. Perhaps you could put a note in the section "Measuring Gears" to describe this notation. Alternatively, let me know what the standard wheel size is for racing bikes and I'll do an initial draft for you to correct. Murray Langton 10:27, 24 November 2005 (UTC)

Hi Murray, oops I meant to call you by your first name but got confused! The standard, and in fact the only UCI-legal size for road racing wheels is 700c. Thanks. Julius.kusuma 11:44, 24 November 2005 (UTC)

Thanks for the info Julius. I've added text and table emtries re road racing measures. Please check it for accuracy. Murray Langton 13:10, 24 November 2005 (UTC)

[edit] Consistency?

Julius, earlier in this talk page you referred to racing bicycles having chainrings of 50/39 etc. In the actual details you added last week re racing bicycles, you refer to chainrings 53/39. Which is correct, so I can get the article consistent? Murray Langton 10:07, 28 November 2005 (UTC)

It should be the 53/39 that is the most common, sorry. Julius.kusuma 11:30, 28 November 2005 (UTC)

[edit] Rewrite December 2, 2005

I rewrote and copyedited much of the article to be more encyclopedic, as Wikipedia is not a how-to guide. Wikibooks has a fledgling bicycle section. I just reformatted the examples section. Comments? --Christopherlin 05:53, 2 December 2005 (UTC)

Thanks Christopherlin, you've done a great job of tidying up my original article. I think there may be one or two minor grammatical points to check, but I'll mull it over for a day or so before I make any changes. Murray Langton 16:04, 2 December 2005 (UTC)

In the comparison table, I'm proposing to change the 'higher' gear from 120 to 125, so as to simplify the comparison with 'racing' notation. I will of course recalculate all the numbers in that row to match. Any objections? Murray Langton 21:43, 4 December 2005 (UTC)

[edit] Why not use real ratios?

I like to think of gearing as a simple ratio: teeth on the front over teeth on the back. The number you get is simply the number of times the rear wheel goes around for every full turn of the crank. I have a spreadsheet that gives ratios for several various crank configurations and several different cassette clusters. I wouldn't mind adding it if I could figure out how to make it look nice... I could email it to a wiki expert if someone wanted to volunteer... Ehidle 18:41, 22 March 2006 (UTC)

This ratio is essentially what racing cyclists do, except they just quote the number of teeth in each cog (e.g. 53/11) without bothering to convert to a single number. The problem is that it does not take into account the size of the rear wheel - compare mountain bike (26" wheel) to a Brompton folding bike (16" wheel). They might have the same cog ratios (say 42/12) but the effective gears will be very different. Murray Langton 22:24, 22 March 2006 (UTC)

I agree, we should use real ratios. It will make this a lot easier. Also to solve the problem of different wheel sizes, you can make 2 different tables, one for the 16" wheel and one for the 26" wheel.--Taida 20:24, 11 July 2006 (UTC)

Unfortunately there are a lot of different wheel sizes apart from the two mentioned above: 12", 15", 18", 20", 24", 27", 55cm, 60cm, 65cm, 70cm at least. In some cases the use of different tyres can also affect the effective diameter of the wheel. So you would finish up with rather a large number of tables. Murray Langton 21:01, 11 July 2006 (UTC)

[edit] Drivetrain efficiency?

I'm a bit sceptical about the reported efficiency for the drive train, especially for internal gearing. Most internal hubs have one direct drive gear, in which all the planetary gearing is effectively locked. Shouldn'd that be as efficient as the best external gearing or even a single-speed (given that the chain line should be optimal)? Moreover, Rohloff claims 95-99% efficieny for the Speedhub 500/14, and claims that to be "totally comparable with those of a high-quality derailleur gear system"[1]. --Stephan Schulz 21:53, 5 July 2006 (UTC)