Jim’s Tech Talk
By Jim Langley
Before we get rolling with this week’s TT, thanks for the interesting and helpful comments to last week’s discussion about whether bottles are safe to drink from. For example, Bob Williams shared that Camelbak actually has bottles with nozzle caps in their Dirt Series (https://amzn.to/3cLxRXF) which I didn’t know. And there are more great readers’ tips worth checking out.
If you missed the column and are wondering what could be unsafe about bike bottles, here’s a link to catch up: Are Bicycle Bottles Safe to Drink From?
Phil Shares Some Great Gearing News
This week’s news also comes from a RoadBikeRider reader. His name is Phil Young. He lives and rides in lovely San Diego, California and he’s emailed us a few times about gearing.
Of all the things we cover here, gearing is among the most popular, so I think you’ll like what Phil told us. He’s been wanting to upgrade a Shimano 9-speed road bike to a SRAM eTap 12-speed electronic drivetrain groupset. Or, he might splurge and buy a new bike with the group on it.
The thing holding him back is that they hadn’t yet offered low enough gearing for him. He knew about SRAM’s 1X (single chainring) setup using their wide-ratio 10-50 cassette but it didn’t offer the fine selection of ratios as the smaller double chainrings he was hoping for.
Phil was looking for something like a 25/38 chainring combo with a 10-33 cassette. He felt that that would provide the perfect gearing for club road riding and light touring especially for older and weaker riders. It would offer an easy 20-inch low gear right up to a 101-inch high with fine jumps of 10 to 15% between each shift.
SRAM’s New Force eTap Wider Gearing
Since Phil’s been in the hunt, he noticed this before we did and was only too happy to share the news that SRAM just came out with a Force AXS “Wide” group with 43/30 chainrings and a 10-36 cassette.
Here’s a link to read all about it: https://www.sram.com/en/sram/road/collections/wider-gearing-for-force-etap-axs.
Phil points out that it’s almost exactly what he’s been looking for and he believes it’ll be perfect for lots of other roadies, too. It has a low gear of 23 inches all the way up to an 116-inch high, with reasonable jumps between.
Here’s how the gear charts look:
The 12 cassette cogs are: 10/11/12/13/15/17/19/21/24/28/32/36
On the 30T ring, you get: 22, 25, 28, 33, 38, 42, 47, 53, 61, 66, 72 and 79 inch gears.
While on the 43, it’s 32, 36, 41, 47, 54, 60, 67, 76, 88, 95, 103 and 114.
It’s always nice when readers like Phil let us know about important new product developments like this so that we can spread the news. To learn more about SRAM’s new Force wide group and see all the components and options, here’s a link: https://www.sram.com/en/life/stories/force-etap-axs-wider-gearing-guide.
Ride total: 9,646
Jim, could you explain the gear inches — like 114 — how you calculate?
Jim Langley says
Sure, Marc, good question. The formula is: divide the number of teeth on the chainring by the number of teeth on the cassette cog and then multiply by 27 (the wheel diameter). That will give you what we call the gear-inch number. The larger the number, the higher/harder the gear is. The smaller the number is, the lower/easier the gear is to pedal.
Hope this helps,
I was comparing to my 50/34 and 11-28 cassette. I get a range from 32 to 122, so it seems 43/30 gives better climbing range at 22 but a bit less on the upper range.
Jim Langley says
Yes, you’re right, Marc. Phil’s perspective – and I’m putting it into my words.., is that most riders don’t need anything higher than the 116 because you have to be a pro rider to actually pedal in those gears – and at those speeds unless you’re a pro, you’ll probably be coasting, not pedaling.. So, he sees anything more as being “wasted” gears since you can’t really use them anyway. Now, when you reduce that high gear a very nice thing happens, which is you get more gears within the range that you can actually use. And because there are more steps in between the easiest and hardest now, your jumps between each shift become closer together, which makes for more efficient riding, too.
Gearing is all about what you like, though, so it’s perfectly fine if you like the gearing you have and not Phil’s. Thanks!
Allan Davidson says
question: why multiply by wheel size, since it is the same for all combinations? I understand it is traditional, but the impact of different wheel sizes on effort needed is pretty small.
Jim Langley says
Hi Allan, you’re right, it’s because of tradition. Gear inches go back to the earliest days of cycling and we were riding bikes with huge wheels back then. I see that another reader in the next comment provided a link to Sheldon’t webpage on gearing and that’s a good resource for learning more about gear inches and gear gain.
Jim Langley says
Hi again, Allan,
Actually, here’s the link that talks about Gear Inches on Sheldon’s site. It’s his glossary so you will need to scroll to Gear Inches to read about how it came about. Good stuff.
Kerry Irons says
Using wheel sizes makes it possible to compare not just 700c or 650b wheels, but also the 20 inch wheels found on many recumbents. But for most road bikes, it is just tradition. And many in Europe use “development” which is distance traveled per pedal revolution.
Greg Przybyl says
For easy gear/gain calculations check out this page:
Brian Becker says
Funny for me I’ve always used gear inches (since late 60’s) and i still have a table on my TT. Overlap gears are in red. in the old days we used to have a table of 5 ratio’s on either side of the stem for reference when your brain was fried. The more things change the more they stay the same. I’m not sure the ration is applied to the diameter I think it is the circumference. When I was juvenile we were limited to 83 inches.
Ray Green says
So a higher top gear than Eddy Merckx. How crazy is that?
John Evans says
I am 63 and definitely not a pro, but I need my 133 gear inch of my 50 front ring and 11 cog to go down the descents here in Colorado. I pedal on these descents staying in front of traffic and even get passed by more capable bikers.