Gearing

Divide the number of teeth on the chainring by the number of teeth on the sprocket; and multiply by the wheel diameter to get the gear in inches; or by the wheel circumference to get the development. Do both your bikes have the same wheel size?
Crank length does not affect gearing, but a longer crank will make it easier to push a big gear, or a small one up a hill. However, crank length should be determined by leg length.

glbenfld said:

Please help me understand gearing. I realize the questions that I'm going to ask have to do with the number of teeth on a gear, but that raw data doesn't mean anything to me. I'm new at this & trying to learn. This is my first post.😕
1. One bike has a 28/38/48 crank, another has 30/42/52. What does one do for me vs. the other?
2. One bike has a 11-32 8 speed cassette, the other 12-26 8 speed. What does that do for me?
I'm wanting to find out really 4 things.
1. What does one crank do for me vs. another? I would like to understand that independent of what the cassette does?
2. What does one cassette do for me vs. another. Again, I want to understand that independent of what the chainrings do?
3. Now I'd like to comibine the above. One bike has a 28/38/48 crank with a 11-32 8 speed cassette. The other has a 30/42/52 crank with a 12-26 8 speed cassette. Everything else being even, how will the one combination perform as compared to the other?
4. Final question. I'm over 50, over 200 lbs., & have only been peddling a few months. I ride 98% of the time on rural paved roads in the rolling hills of Piedmont NC. Everything else being equal, which of the above would make peddling up hill the easiest? Getting up hills is what I need help with the most.
I'm trying to learn how to translate the raw data of how many teeth a gear or chain ring into how that will affect me as I ride. I want to be able to understand how different size cassettes affect my peddling, how different size chain rings affect me peddling, then how different combinations of the two affect peddling.

The parameter that you want to focus on is the ratio of the number of teeth on the front chainring to the number of teeth on the rear cassette cog. By convention this ratio is usually mulitiplied by the diameter of the rear wheel (in inches-27" for typical road bikes with 700c or 27" wheels) to get the "gear-inches" for the given combination.

A lower gear-inches is an easier gear to pedal and a higher gear-inches is harder to pedal, but faster. As an example from your bikes, the one bike has a lowest gear combination of 28/32 which is 23.6 gear inches (28/32 X 27 = 23.6) and the other bike has a lowest gear combination of 30/26, which is 31.1 gear inches and is therefore not as low a gear. On the high-end, the 48/11 is 117.8 gear inches and the 52/12 is 117.0, or virtually the same. You can calculate the whole range of ratios manually or use a gear-inch chart such as found at this link and others on the internet:

http://home.i1.net/~dwolfe/gerz/index.html

Regardless of the combination, equivalent gear inches will pretty much feel the same for an identical wheel diameter and crank arm length (longer arms give a little more leverage). So a 48/24 is the same as a 38/19. The proper range of gearing for you will depend on your level of fitness, the terrain you ride, the load you carry, the road surface, and other factors.

For the two bikes you present, the 28/38/48 has a wider range of gears with a lower low end and will be easier to pedal uphill. The high-end is similar so there will not be much difference in top-end speed, but the 30/39/52 bike will have a smaller differences between each gear ratio because the cassette has a narrower range (14T as opposed to 21T), which can help maintain a smoother pedaling pattern as you shift gears. If you need help getting up the hill, go with the 28/38/48 and the 11-32 cassette 8s bike.

John, very good info. I'm such a newbe that I didn't have a clue of what teeth meant when it comes to actually peddling. Your explaination puts it down to basics which is where I need to start. With your info it's very easy to translate the raw data to what my legs will tell me when I start up a hill. Thanks for the great info.

OK, the 28/38/48 crankset and 11-32 rear cassete is mountain bike gearing probably a 26" wheel size. It is designed for lower speeds.

The 30/42/52 crankset and 12-26 cassette is road bike gearing and a 700c wheel size. It is desined to go faster.

If the two bikes you are comparing are similar, chances are the one with the MTB gearing is a cheaper entry level bike.

Weight of rider + bike + gear must not exceed a predetermined amount set by the bike manufacturer. Normally 110kg or 120kg for road and 130kg for MTB.

Don't worry about all this gear inch stuff, if you want a table I'll show you how to make one.

Both bikes have 700 size wheels.

glbenfld said:

Both bikes have 700 size wheels.

That's effectively 27".
One of your bikes has a top gear of 27*48/11 =117.8 inches, and a low of 27*28/32 =23.6 inches; the other a high of 27*52/12 =117 inches, and a low of 27*30/26 =31 inches.
23.6" is pretty low, for touring with a load for instance.

Ok, everyone has done a great job of helping me understand how to calculate what the different chain rings & cassettes do for me when I'm trying to ride up a hill. I understand the 28/38/48 with the 11-32 8s cassette will help me with hill climbing better than the 30/42/52 with the 12-26 8s cassette. Now let me introduce one more factor. Bike weight. Let's assume the rider & gear are the same in either situation. How much lighter would the higher geared bike above have to be, to even out the performance of the lower geared bike when it's time to climb hills?

If both bikes weighed the same, I have grasped the 28/38/48 w/11-32 8s would give me easier peddling uphill, while the top end of both bikes would be about the same. I also understand the the other bike would have smoother shifting because of the tighter gear range in the cassette.

Having said that, assuming all other things are equal, how can I determine how much less the higher geared bike would have to weigh than the lower geared bike, to make getting up hills be a wash, or perhaps even easier?

glbenfld said:

Ok, everyone has done a great job of helping me understand how to calculate what the different chain rings & cassettes do for me when I'm trying to ride up a hill. I understand the 28/38/48 with the 11-32 8s cassette will help me with hill climbing better than the 30/42/52 with the 12-26 8s cassette. Now let me introduce one more factor. Bike weight. Let's assume the rider & gear are the same in either situation. How much lighter would the higher geared bike above have to be, to even out the performance of the lower geared bike when it's time to climb hills?

If both bikes weighed the same, I have grasped the 28/38/48 w/11-32 8s would give me easier peddling uphill, while the top end of both bikes would be about the same. I also understand the the other bike would have smoother shifting because of the tighter gear range in the cassette.

Having said that, assuming all other things are equal, how can I determine how much less the higher geared bike would have to weigh than the lower geared bike, to make getting up hills be a wash, or perhaps even easier?

Actually that rather depends on you. Some cyclists like to mash big gears, and some prefer to spin small ones. You should be trying to spin since is easier on your knees and on the bike. But other factors come into it as well, such as bike geometry and set-up, the best way to find out what you wish to know is to do a lot of riding.

glbenfld said:

Ok, everyone has done a great job of helping me understand how to calculate what the different chain rings & cassettes do for me when I'm trying to ride up a hill. I understand the 28/38/48 with the 11-32 8s cassette will help me with hill climbing better than the 30/42/52 with the 12-26 8s cassette. Now let me introduce one more factor. Bike weight. Let's assume the rider & gear are the same in either situation. How much lighter would the higher geared bike above have to be, to even out the performance of the lower geared bike when it's time to climb hills?

If both bikes weighed the same, I have grasped the 28/38/48 w/11-32 8s would give me easier peddling uphill, while the top end of both bikes would be about the same. I also understand the the other bike would have smoother shifting because of the tighter gear range in the cassette.

Having said that, assuming all other things are equal, how can I determine how much less the higher geared bike would have to weigh than the lower geared bike, to make getting up hills be a wash, or perhaps even easier?

I would largely ignore bike weight as a major determinant in bike choice.

The actual weight difference between bikes is not likely to make much of a difference during actual climbing since it is likely to be only a few pounds at the most. This difference is also negligible compared to the weight of the rider. Many people probably could stand to lose 10-15 pounds off their gut and [censored] which would have much more of an effect than saving a few hundred grams on the bike. One bike may feel easier than the other though at a given gear ratio, depending on the tires, wheel weight, body position, etc... Overall bike weight is overrated as a performance factor by most people under general riding conditions. For your choice of a new bike, I think the priorities should be bike fit and suitability for the intended purpose (MTB for off-road/trails, road bike for roads/longer rides, flat-bar if you like more upright riding position, etc...), with the gearing range chosen to be reflective of your level of fitness, terrain, predicted load, etc...

Test ride the bikes that you are considering, discuss your intended use with a (hopefully) well-informed bike shop salesperson, and make your choice based on what feels the best. Gearing for any bike can be easily changed later if your level of fitness changes or if you ride different terrain by chaining the cassette or chainrings.

Good luck!

John, great advice as usual.

I have been for a test ride on both bikes. You're certainly correct about losing a few pounds would help more than anything. That's the reason I'm riding. Both bikes are considered fitness bikes. One is a Giant FCR 4. The other is a Trek 7.2 FX. Both are flat bar bikes which I like. I've been riding a Trek 3500 MTB with road tires. Another family member wants my 3500 & our LBS has verified the fit is ok.

The Trek 7.2 is the one with the lower gearing from my post yesterday. As you explained, both have the same top end so that's a wash. The Trek has a lower low end which is what you explained that I need for some of the hills I regularly ride on. I like a flat bar bike. A road bikes riding position isa little too agressive for my overweight frame. The Giant FCR 4 & the Trek 7.2 FX seem to be a nice nitch for what I'm looking for. I know there are flat bar road bikes, but from our discussion yesterday about gearing, it would appear either of these bikes would give me the top end I need for my level of riding, but it would seem the Trek would give me the extra help I need to pull the hills where I most often ride.

There is no reason why you can't buy the bike that you like the best, and have the gearing changed to suit the type of riding that you intend to do.

Giant FCR4: http://www.giant-bicycle.com/us/030.000.000/030.000.000.asp?year=2005&model=11031

Trek 7.2 FX: http://www2.trekbikes.com/Bikes/2006_preview.html

I think the Giant has better components.

glbenfld said:

John, great advice as usual.

I have been for a test ride on both bikes. You're certainly correct about losing a few pounds would help more than anything. That's the reason I'm riding. Both bikes are considered fitness bikes. One is a Giant FCR 4. The other is a Trek 7.2 FX. Both are flat bar bikes which I like. I've been riding a Trek 3500 MTB with road tires. Another family member wants my 3500 & our LBS has verified the fit is ok.

The Trek 7.2 is the one with the lower gearing from my post yesterday. As you explained, both have the same top end so that's a wash. The Trek has a lower low end which is what you explained that I need for some of the hills I regularly ride on. I like a flat bar bike. A road bikes riding position isa little too agressive for my overweight frame. The Giant FCR 4 & the Trek 7.2 FX seem to be a nice nitch for what I'm looking for. I know there are flat bar road bikes, but from our discussion yesterday about gearing, it would appear either of these bikes would give me the top end I need for my level of riding, but it would seem the Trek would give me the extra help I need to pull the hills where I most often ride.

I'm going to agree with gclark8 that the Giant has a little bit better components. In making a quick comparison to the current version of the Trek 3500 MTB specs, it looks like the FX 7.2 is a similar level component group and frame as the 3500 but with a more road like geometry and 700c wheels.

The Giant has narrower, lighter tires (28mm vs 35mm), and therefore may feel a bit quicker on the road. The SRAM shifters and rear derailleur and can accomodate a lower range cassette (may require a slightly longer chain), although some shops are reluctant to do much part swapping for entry level bikes.

I would suggest that you think carefully about what features you would want to improve from the current MTB to help guide the selection of the new bike. If the current bike is too hard to push up the hill, either of these choices won't be much easier. The MTB already has a really low gear of 28/34 that is even lower than that of either of your choices for a new bike. Also think what gear you actually ride in the most. If you are on the 28T small chainring much of the time now, you probably need to go for the lower range gearing. If you are only on the small chainring occasionally as a bail out on the steepest hills, then the range on the Giant may be OK. Although I would say that the 42T middle ring with a 12-26 cassette is a pretty high gear range. I would prefer a 39T middle ring for that triple.

If the current bike feels heavy and sluggish on the road, the Giant may be a better choice because of the lighter wheels and tires.

Since bikes have components that can be swapped out, I would get the bike that you overall like the best. Ride it awhile and modify the gearing as needed. If the shop is any good, they want you to be a satisfied customer and will work with you to get the bike that suits your needs the best and set it up to fit your body and your usage the best.

Whatever way you go, if you don't already ride with them, I would suggest that you consider clipless pedals and bike shoes (MTB-type SPD or similar would probably be best for your use since they are easy to walk in). They are way more efficient than using pedals without toe clips/straps and somewhat more efficient than using clips/straps but safer and more comfortable in my opinion.

Good luck and enjoy the riding.

Cassette Question:

I've been to some of Sheldon's pages & some other sites. I've found places where the number of teeth for each gear in a given Shimano cassette are listed.

Does anyone know of a site where the teeth of each gear in SRAM cassettes are listed? Specifically, SRAM PG830 11-32 8 speed, & also SRAM PG850 12-26 8 speed. I realize I could count them if I had the cassettes in hand, but I don't.

I want to plot the gain for each gear on the cassette, but can't do that unless I can find the number of teeth in each gear.

Edit: You now have the desired information in the post following mine, however, a story: Two of my friends bought new flat bar road bikes last year.

The first, a Felt SR101, it had 8 speed 12-26 cassette, 30/42/52 chainrings and 28mm 700c tyres.

The Second, an Avanti Blade, 8 speed 11-30 cassette, 28/38/48 chainrings and 28mm 700c tyres.

They ride together on Saturday and Sunday mornings for 2-3 hours. The chap on the Avanti normally keeps up with the guy on the Felt ok.

I recently fitted my old 100psi 25mm tyres to the Felt SR101, the reduced rolling resistance immediately made up 1-2 gears on all rides, the chap on the Avanti can no longer keep up and now wants to upgrade his gearing and tyres!!

The reason for this story, don't worry too much about the gearing too much, however, buy the best components you can afford and the best tyres, and keep them inflated!!

My SR81 Felt goes so well with the new Conti tyres, I fiddled with the gearing (12-25, 13-23), but the tyres made the big difference.

glbenfld said:

Cassette Question:

I've been to some of Sheldon's pages & some other sites. I've found places where the number of teeth for each gear in a given Shimano cassette are listed.

Does anyone know of a site where the teeth of each gear in SRAM cassettes are listed? Specifically, SRAM PG830 11-32 8 speed, & also SRAM PG850 12-26 8 speed. I realize I could count them if I had the cassettes in hand, but I don't.

I want to plot the gain for each gear on the cassette, but can't do that unless I can find the number of teeth in each gear.

11-12-14-16-18-21-26-32

12-13-15-17-19-21-23-26

see: http://www.sram.com/_media/pdf/sram/dealers/TM_MTB_MY06_E.pdf
pages 34-35

serenaslu,
Thanks for the info & for the link. I'd Googled & been to SRAM's website, but hadn't been able to find the data. Just what I was looking for.

11-12-14-16-18-21-26-32

12-13-15-17-19-21-23-26

see: sram.comTM MTB MY06 E.pdfOpen ↗
pages 34-35