Gear ratio question

[dsimon]

I just bought e new to me serotta legend and it has a gear ratio of 52/36 front and a 13/29 rear campy 10spd. How and what does this ratio do for someone that is used to a traditional 52/42..... or 53/39...... thanks Demetrius :beer:

[Dave]

The big ring is the same, so that's no change. The 36T little ring adds gearing ramore low gearing, but it also requires on more cog to be shifted after a chainring shift, in order to produce a uniform gearing progression, compared to a 52/39. Most often, you'll want to shift 3-cogs smaller after shifting to the little ring, to have a uniform progression.

You've got a compact crank, but the chainrings are both larger than the typical 50/34. This drops the lowest gear by about the same amount that 1-cog larger would do.

Comparing the lowest gears is simple. Your 36/26 low gear is like a 39/28 or a 42/30.

[dsimon]

weird Thats all I can think of it

[palincss]

http://sheldonbrown.com/gears

Plot your old and new gearing, find out exactly how they compare.

[dsimon]

sorry still cant make heads or tails of it maybe ill just get a new cranks set.


52 44.4 % 36
13 8.1 5.6
7.7 %
14 7.5 5.2
7.1 %
15 7.0 4.8
6.7 %
16 6.6 4.5
6.3 %
17 6.2 4.3
11.8 %
19 5.5 3.8
10.5 %
21 5.0 3.5
9.5 %
23 4.6 3.2
13.0 %
26 4.0 2.8
11.5 %
29 3.6 2.5

[AndrewS]

What is there to make heads or tails of? That chart will give you the ratio, gear inches (how big your wheel would be if you were riding a high wheeler), KPH or MPH you produce at a fixed pedal RPM. The point of the chart is to give you an objective point of comparison between different gear combinations.

The only thing that has changed is that you now have lower gears than you used to.

In terms of which gear combinations you use, that doesn't really change: You use the inside seven cogs with the 36 chainring, and the outer seven set of cogs with the 52 chainring. The other six combinations are duplicated elsewhere so you avoid them to lower the cross-chain effect of going from inside to outside of your chainline.

[Tobias]

I just bought e new to me serotta legend and it has a gear ratio of 52/36 front and a 13/29 rear campy 10spd. How and what does this ratio do for someone that is used to a traditional 52/42..... or 53/39...... thanks Demetrius :beer:
Demetrius, if you like what you had you can replace the 36 tooth inner ring with a 39 or 42 if that's what you want. They are available and not that expensive ..... at least not compared to cassettes. The difference in the big ring between 52 and 53 teeth is not worth worrying about.

[Dave]

There is absolutely nothing wrong with using any of the gear combos except the big/big and little/little. Avoiding more combinations just results in more frequent chainring shifts and the subsequent cogs shifts that follow. If you're stuck in the 52/23 for a long time, you might consider shifting to the 36/16 instead, but the 52/21 is certainly not a problem.

[Marcusaurelius]

I'm not sure why anyone would want to use a 52 tooth chainring on a compact crank. I don't see where a 52/36 would be any advantage if you can use a 53/39. I'm also if you climb the swiss alps because that's about the only time I would use a 13/29 cassette with 52/36 chainrings.

It seems a little odd to me.

[AndrewS]

It seems that this gearing set up was designed to offer an extremely broad gear range on a double without huge steps in the cassette. Hence the 52x36 crank, rather than a 50 and using an 11 or 12 high gear. One good way to achieve that goal is using a compact crank but with a non-compact size chainring. Think of it as semi-compact.

[palincss]

I'm not sure why anyone would want to use a 52 tooth chainring on a compact crank. I don't see where a 52/36 would be any advantage if you can use a 53/39.


A 36T chain ring gives you lower gears all through the range than a 39, which certainly could be an advantage.

[Ti Designs]

As with all of the threads on gear ratios, this comes down to three factors: Chainring size, cog size and rider. Folks here like to make way too much fuss about the first two numbers. It's a ratio, nothing complicated about it. From there it's just a question if the range is what you need based on your own ability and where you ride.


Or, you could print out a gear ratio chard, tape it to your stem and try to find the sequence that gets you from one gear ratio to the next. This involves lots of concentration and shifting, the thought process goes something like this: "Let's see, I want the next gear up, and it's Tuesday, so I have to click this lever twice, pull this back once, pedal six times and - ah crap, that's not the gear I need..."

[sg8357]

"Let's see, I want the next gear up, and it's Tuesday, so I have to click this lever twice, pull this back once, pedal six times and - ah crap, that's not the gear I need..."

DI2 with half step granny software kit, coming soon from ShelBroCo. :)

The new Sram Apex group uses a 50/34 with an 11-32, spacing is not
as good as the OPs setup.

[Ti Designs]

DI2 with half step granny software kit, coming soon from ShelBroCo. :)


I've heard about that, it comes with a G3 link which tells Shimano what gear you're in, and using GPS it can also tell the grade. Shimano will use that data for the next generation (DI2.7.5 - there were a few problems along the way) so when you buy a bike they will select the gears for you. The next generation will also introduce automatic software updates, so from time to time your shifting controls will move from the brake levers to under the start menu...

[RPS]

I'm not sure why anyone would want to use a 52 tooth chainring on a compact crank. I don't see where a 52/36 would be any advantage if you can use a 53/39. I'm also if you climb the swiss alps because that's about the only time I would use a 13/29 cassette with 52/36 chainrings.

It seems a little odd to me.
As I recall the first time a modern compact was used in a major tour it was Tyler Hamilton and he used that ratio or chainrings -- 52/36.

I have stated in the past that I would like to see the 110 BC (i.e. -- compact bolt circle pattern) become the new standard. We can always go to bigger rings but we can't go smaller than the BC allows (not easily anyway). With compact BC we have greater flexibility to make changes with little cost. I see little reason why we shouldn't be able to switch chainrings like we do cassette sizes. Granted it takes a little more work, but so what?

For what it is worth, I have a 54 tooth big ring on my compact (110 bolt circle) tandem. Other than the rings having to be a little heavier to resist bending (which could be offset in part by spider weight) I see little not to like. And if I want to change gearing I can install a completely different set of rings for climbing or light offroad. For me it's a win win.

[palincss]

That's actually a pretty good idea. And if that should ever actually happen, and "compact" becomes "standard," the new compact could be 50.4, like the TA Pro V Bis and the VO Grand Cru (http://velo-orange.blogspot.com/2010/02/grand-cru-crank.html) . That would allow 30/46 wide range doubles.

[AndrewS]

The 5 bolt compact mountain crank would let you do that right now, I would think. The 94 bolt circle should be small enough.

Of course, you're giving up a little longevity by going smaller and smaller.

[RPS]

One solution I like is having two sets of bosses, one for each ring. That's the way SRAM set up the new XX MTB cranks with 120 and 80 mm bolt circles. On the surface this seems to give greater total range (i.e. -- flexibility) for chainring size selection.

For a road bike I'd prefer the traditional five-arm (5-bolt) pattern, but the general idea holds. 110 BC for big ring and something smaller (maybe 74 or 92 or 94) for small ring would work for me. And if the small ring is fairly large it could be bolted at the 110 bosses using spacers. Shimano went with 92 mm on new Ultegra triple which only allows going down to about a 30T ring, but it shows how rings can be bolted to each other.