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TBird
10-13-2008, 10:04 AM
Hello Ladies—
I am a MTBer, in the market for my first road bike in 20 years. I’ve demo’d a handful of bikes, and recently became smitten with Trek Madone 5.1. (Yes, it’s way more bike than I “need,” but that part I can justify!) My only concern is that it has a compact crankset rather than a triple. I live in a very hilly area, and I did notice that when climbing, I was wishing for some smaller gears. I’m not sure if this is because I’m used to my MTB’s granny gears, just not used to road bikes, or if I really would be happier with a traditional triple crankset. I know Trek makes this bike in a triple, but I can’t find an 08 in my size.

Any thoughts from those who love or hate compacts? Also, is it a big deal to switch it out if I don’t like it? I read somewhere I could swap the cassette and end up with almost as many gears. Is that expensive? I’m thinking maybe I could ask the shop to do that as part of the sale. Right now, it has a 34/50 in front and 12-27 in rear.

I appreciate any input. You’ve all been a huge help already—I’ve been trolling this forum for a few weeks now and have learned so much!

melissam
10-13-2008, 10:29 AM
Hi TBird,

I can't help you with the compact vs. triple question, as I've never ridden a compact double. I'm currently getting a custom crankset made, and the guy who makes it is trying to convince me to go with a compact double. He says the shifting is much more precise than with a triple.

At one point, I considered switching a bike with a standard double to a triple. It was a slippery slope of equipment changes: new crankset, new front derailleur, new shifter. I ended up buying a bike with a triple.

As far as changing your cassette goes, I'm heartily in favor of it! I switched the road cassette to an 11-34 cassette, with a mountain bike rear derailleur, and a new chain. I picked up a new SRAM 9-speed cassette & chain on eBay for ~$40, and an XT derailleur for under $50. If you went with your compact double and an 11-34, this would give you a low gear of 34-34, vs. a 30-27 if you went with a triple and kept your current cassette.

The disadvantages of a mountain cassette is that your gears are wider apart. Sometimes on the flats, you might find that you either have to spin faster than you would like or mash harder than you'd like. (I rarely notice this and find that having the low gears is well worth it!)

I also wonder if you could switch the chainrings on your compact double. Think limbo: how low could it go? If you could get a 24 on there, that'd be a 24-27 low gear. Hmmmm..... Of course, your big ring would probably be a 40, so your high gear would be a 40-12, which might be to low for descents or flatland cruising.

Anyway, plenty to think about. And you were probably hoping for a simple answer. :)

TBird
10-13-2008, 11:02 AM
Wow, thanks Melissa. Great food for thought.
I realize I gave the wrong specs for the existing cassette. It's 11-25 on the compact, not 12-27. I can see how a MTB cassette could make a huge difference. Do you think even a 12-27 would make a difference? (Might be able to convince the LBS to make that change for free...)

melissam
10-13-2008, 11:09 AM
TBird,

I honestly don't think that a 34-27 will make a huge difference on hills vs. a 34-25. According to Sheldon Brown's gear calculator, a 34-25 will give you 35.7 gear inches, and 34-27 will give you 33.1 gear inches, assuming 700c wheels. Helpful, but not a huge difference on the hills.

Please keep in mind that this comes from someone who not only has a mountain cassette, but also a triple! I have to say that having my 30-34 available gives me great peace of mind on many a ride. I might not use it, but it's very reassuring to know that it's there.

One more thing: I rode with someone who had a mountain cassette with a 32 in the back, and he was able to use his Ultegra rear derailleur. You would just want to be careful and avoid shifting into the 32 while you're in your big ring. It's not something I'd do on purpose, but I can't guarantee that I wouldn't have a very blonde moment at some point during a long & strenuous ride.

- Melissa

ilima
10-13-2008, 12:27 PM
The shop should be able to switch out the cassette to a SRAM 12-28 for essentially free. Shimano road rear derailleurs are rated for 27, but they work okay with a 28-tooth cog.

As to the compact, I think it offers a very versatile setup. I run a compact crankset and a 12-25 and I'm a hill slug. For my commuter I used a triple, but for regular, unloaded road riding a compact is going to do the trick for most folks.

It would be quite costly to switch to a triple crankset. So costly that I think you'd be better off looking for a bike that already has a triple if you really want one.

Aggie_Ama
10-13-2008, 01:02 PM
Wow, thanks Melissa. Great food for thought.
I realize I gave the wrong specs for the existing cassette. It's 11-25 on the compact, not 12-27. I can see how a MTB cassette could make a huge difference. Do you think even a 12-27 would make a difference? (Might be able to convince the LBS to make that change for free...)

I live in Central Texas, somewhat hilly but not mountains. I wasn't ready to chunk my Ultegra Deraileur on my bike so I swapped 12-25 to 12-27. My LBS is one that does not like the SRAM 28 they said it works okay but they don't advocate it themselves. "Works okay" doesn't work for me. It is a noticeable change with the 12-27 but not enough if you aren't a mountain goat. I will eventually put a XT or XTR with a mountain cassette. It is overkill for my area but I like to go out to the extreme TX Hill Country and even on vacation to the mountains as often as I can. I can't climb and am a bit too unmotivated for hill repeats. I just like to ride for the joy of it not much on training. I also ride a triple. I like puppy gears, I don't ever in my wildest dreams see myself becoming a strong climber.

alpinerabbit
10-13-2008, 01:06 PM
I ride the swiss alps on a compact / 11-27 Ultegra. I'm fine. I'll struggle with 15-20% slopes but 8-12% is peachy.

madscot13
10-13-2008, 01:49 PM
I never thought I would become a strong climber. So I have a triple and a mountain cassette (I think I have an 11-34, but next time I would choose a set with closer gears). I used to do this one will on my granny gear and just spin my legs off. I am better now and I can stay in my middle gear and keep my cadence going. I still get passed but more importantly I still pass some.

it took a lot of training to get to the point that I am at now. I also haul groceries some times and the extended gear ratio is nice then.

Misandal
10-13-2008, 02:09 PM
TBird, my two cents: I started out with a triple and rode it for three years, then bought a bike that had a compact double and rode it for a year. When I traded it for my new Madone this spring (which came with a compact double), I asked my mechanic to put a triple on it. It didn't cost me any more and it's full Ultegra.

The compact had low enough gearing for the climbing that I do, but I missed all the in-between gears that you get with a triple. I felt like I was always in a gear that was either too easy or too hard, I could never find that happy in-between. I'm back on a triple and I'm much happier with it.

madscot13
10-13-2008, 07:38 PM
I spend most of my time in my 39. With my wide cassette I don't really shift so much. (Maybe I should be?) I always wonder what being in a 34-36 would do to me.

TBird
10-13-2008, 07:45 PM
This is so helpful everyone, thanks. I love the idea of customizing once I've spent some time in the saddle, but lots of swapping out of the gates feels a bit overwhelming. Seems like I'll know more about what I want after a couple hundred road miles.

Misandal, I was surprised (and psyched!) to hear that your LBS swapped out a compact for a triple for free. Do you know if they had a triple in stock, or did they really do the labor of disassembling and reassembling? I'm not sure my shop would be so accommodating. But it never hurts to ask...

Misandal
10-14-2008, 06:18 AM
No, they didn't have it in stock - they ordered the bike for me and then had to do the swapping once it arrived. I didn't inquire what the price of the bike would be had I taken it with the compact, but I paid what typical retail price on that bike was and I got it with a triple, so my perception of the deal is that it didn't cost me any more to get it the way I wanted it. :)

Aggie_Ama
10-14-2008, 06:28 AM
When I bought my bike in December 2006 (Cannondale Synapse 3 which at the time was the lowest end gruppo on the carbon) it was offered with a triple or compact double. I believe the Synapse 2 (Full Ultegra mine is 105/Ultegra rear) was also offered double or triple. Only the highest end Dura Ace was only double.

So it may be simply ordering the crank to switch since the bike is offered that way? Even if they are not in stock to be shipped that way I would think the LBS would have no problem doing it if it meant they sold that caliber of bike. :confused: I would think (and I don't know) the bike shop could just stock the double as a replacement/upgrade for someone?

OakLeaf
10-14-2008, 06:31 AM
It really depends on the LBS. My bike (same as Amanda's) came with a 170 mm crank and I had to buy the 165 to swap out (although IIRC they did the installation no charge). It got me a spare set of chainrings anyway :rolleyes: (which are right now getting installed at another LBS).

ilima
10-14-2008, 11:17 AM
It really depends on the LBS. My bike (same as Amanda's) came with a 170 mm crank and I had to buy the 165 to swap out (although IIRC they did the installation no charge). It got me a spare set of chainrings anyway :rolleyes: (which are right now getting installed at another LBS).

They didn't opt to credit you for the 170s? My bike came with a Cane Creek headset and I wanted a King ($$). The shop owner credited me full retail for the CC and then charged me for the King, which I thought was a fair deal. The CC headset was never installed.

RolliePollie
10-14-2008, 01:24 PM
I have a triple and I pretty much use every gear combo on every ride...but I ride loads of hills. I think it depends on the terrain where you'll be riding. I would not give up my triple but it's only because I'd never make it up some of my hills if I didn't have my granny gear!

Miranda
10-19-2008, 03:08 AM
My knowledge of switching the parts out is humble, but I do know that anything doesn't feel good to do ends up being something I don't look forward to doing.

My road bike has a triple. While I don't live in mountain land, I know my body could not probably take just having a double. Regardless of how strong my muscles are, I have some medical issues with weak facshia. Anything that causes me to torq on that tissue more than it can take, means pain = don't do it. My heart rate typically can take a lot more that the body parts, and recover.

Now, my situation is a bit unique, but the same principle still applies. With only having the double on the bike, will you look at a hilly route and think "ooohhh, dread/groan, grumble (maybe even avoid it)..." in time because the tools you have (a double vs a triple) to do it with make the activity a PITA, vs generally enjoyable (what the ride should be).

Just some food for thought:).

Bluetree
10-19-2008, 05:54 AM
Changing cassettes is a very easy way to get a wide range of gearing on a compact. Once you get the hang of it, it's very simple. I have compacts on both my road bikes and change out anything from an 11-23 to a 13-29!

There is absolutely nothing wrong with a triple. But the reasons why I gave up a triple is twofold. First is size/weight. I admit that I'm a weight weenie and I get a perverse sense of satisfaction getting my bike down to 14 lbs. Plus, shorter carbon cranks (sub 170) don't come in standard sizes very often.

But the biggest reason is quicker shifting. This may not be an issue with non-racers, but riding a triple turned out to be a big problem when riding hills/rollers with my racer-type friends. Upon cresting a hill or roller, the (bigger) guys can cruise for a few seconds and let their momentum caryy them as they upshift. With my lesser weight, I don't have the luxury of those few seconds as I would be dropped immediately. I have to get in my big ring quickly and immediately, and start mashing down the hill as hard as I can. Same as whwn the downhill suddenly becomes an uphill. That was cumbersome with a triple, and more than once I dropped a chain, and got dropped by the ride. When I got a compact, those issues disappeared. Two chainrings instead of three def. made my life easier.

Crankin
10-19-2008, 07:24 AM
I'm like Miranda. I have always had a triple; right before I got my Kuota, I was actually thinking about switching out my 11-25 triple on my Trek 5200 for a compact double. I'm glad I didn't because about a year later, we moved to our house on a 10-15% grade hill. After about 2 months with my Kuota, we switched out both of our bikes to 11-27s.
I spin every chance I can get; mashing really aggravates my fibromyalgia. I've also lost a bit of strength in the past couple of years and I like the option of having lower gears. I am an OK climber for an "old lady," but I am not getting any younger...
Now, I am not a racer, but I do regularly climb steep grades. They are not usually long, but they are grades that a lot of people might walk. I definitely could not get up them without my triple. This summer was the first time I EVER got off my bike and walked up a very steep (18%) climb that was very long. At that point, I was thinking about Lisa's mountain gearing I had seen the day before! But, I was able to get back on the bike and finish the climb, which was not very easy, even after the steepest part.
And btw, my bike weighs about 15.5 pounds (without my bag).
If you are not racing, you need to think about the type of riding you do and not care what anyone else thinks. I've never had any trouble with my Ultegra triples.

RoadRaven
10-19-2008, 10:30 AM
My 2c
I have only ever ridden a triple off-road on my entry-level mountain bike.

I have a 10 speed compact crank set on what is now my training bike (roadie). 50-34 on the front, 27-12 on the back. I raced on my EMC2 FemetapePro for about a year before getting a better race bike and turning this one into a pure road-training bike. I climbed several hills with gradients of 15-18%, I am no hill climber and did not have to get off and walk, though at times I was only going at 4 -5kph.

It does everything I require - my smallest gear gets me up hills, my biggest gear allows me , on the flat, to crank it up to about 35kph for short bursts (or about 48kph for ages with a tail wind).

The only issue I had with the compact was when I first got it (and sometimes still have), was changing in the middle of the block - sometimes I couldn't quite find the 'right' gear to be in and would spend some time changing around trying to find the 'right' place to be. That was no good during racing.

But apart from that it does everything I need.

xeney
10-19-2008, 12:05 PM
To me, this answers the question:


I live in a very hilly area, and I did notice that when climbing, I was wishing for some smaller gears.

If you are wishing for them on the test ride, you are going to have times when you want them. I'd go for a triple.

RoadRaven
10-19-2008, 11:30 PM
I agree with xeney, but only if the triple actually gives you a lower gear then a compact set, or 'normal' double.

Sometimes a triple gives no true advantage, and adds only the complexity of an extra ring to contend with.

Sometimes the only real advantage is psychological, that is, "the shop guy tells me if you have a triple I can climb anything, and I have a triple, therefore I can"

Sometimes cyclists new to understanding bikes and gearing dont get told (or dont believe - like me) that sometimes it is easier to go up a gear to climb a hill and NOT be in your lowest gear.

Bluetree makes a great point early in this thread - a triple weighs more than a double, and if you want to get up a hill more quickly every little bit you shed helps.

Ask at the shop what the options are in terms of lowest gearing and then bring all the numbers back to us if you feel unsure...

For example, here are my stats [front // back // lowest gear]:

50-34 // 27-12 // 34-27(training bike) - gets me up a local 800metre, 18% climb at about 4.8kph

53-39 // 27-12 // 39-27 (road race bike) - tough on a hill but do-able as the bike itself is very light and responsive

52-39 // 27-13 // 39-27 (time trial road bike) - but I avoid hills on this because the bike itself is heavy. The low front end combined with aero bars makes hills difficult and uncomfortable

aicabsolut
10-20-2008, 07:19 AM
I ride the swiss alps on a compact / 11-27 Ultegra. I'm fine. I'll struggle with 15-20% slopes but 8-12% is peachy.

I ride a compact (50/36) with a 12-27 cassette. That is equivalent to a 50/34 with a 12-25. I struggle in the mountains only when the grades get upwards of 15% as well. Over 20% is really really tough. However, long sustained climbs from anywhere in the 6-12% range is doable. I'm thinking of taking my old frame and putting a 50/34 on it (using my same cassette) to get just one more gear for riding the mountains.

My compact is perfect for my usual terrain and racing. I run out of gears on the top end more often than on the low end. If I lived in the mountains, I might prefer a triple, but I think even then I'd be more inclined to just put more gears on the back--like maybe a 50/34 with a SRAM or DA7900 cassette with a 28 cog. It's not that much of a difference in gear inches, but my current gearing is *almost* enough for steep grades.

xeney
10-20-2008, 07:24 AM
I agree with xeney, but only if the triple actually gives you a lower gear then a compact set, or 'normal' double.


Okay, good point, and I should have said that if she knew on the test ride that she wanted lower gears, she should be sure to get those lower gears before she buys the bike. Whether that means a triple or something else.

OakLeaf
10-20-2008, 08:23 AM
I wonder if distance makes a difference, too. And whether you're riding with others. For a short ride, maybe you can "live with" an uncomfortable cadence; if you're alone, maybe you can maintain your preferred cadence but not ride your first choice of pace. But if you're going to be out for hours - or if you're trying to stay with other riders - you don't have that luxury.

With a compact, yes you can get some pretty low gears, but you're going to be losing gears in the very range that you ride the most. That's not just an issue for racers. IMO it's just as important for less strong riders. I wonder if the preponderance of strong but casual riders on this board is the reason there seems to be so much preference for compacts.

Also, if you're running out of high gears, that means you're not going to have as much momentum on descents to propel you up the next hill.

Of the two groups I ride with, in the stronger and faster group (B/A-) about half of them run triples; in the slower group (C+/B+) ALL of them do. The slower group is mostly composed of people who ride 7-10,000 miles a year, just at a slower pace.

As has also been pointed out when the topic has come up before, it depends on how much you plan to haul, too. If you're commuting or touring, your needs are very much different from a day rider's.

aicabsolut
10-20-2008, 10:31 AM
I wonder if distance makes a difference, too. And whether you're riding with others. For a short ride, maybe you can "live with" an uncomfortable cadence; if you're alone, maybe you can maintain your preferred cadence but not ride your first choice of pace. But if you're going to be out for hours - or if you're trying to stay with other riders - you don't have that luxury.

With a compact, yes you can get some pretty low gears, but you're going to be losing gears in the very range that you ride the most. That's not just an issue for racers. IMO it's just as important for less strong riders. I wonder if the preponderance of strong but casual riders on this board is the reason there seems to be so much preference for compacts.

Also, if you're running out of high gears, that means you're not going to have as much momentum on descents to propel you up the next hill.



That's not necessarily true. Even in races, I rarely run out of gears on either end. Therefore, the range of gears that I need the most is precisely what I have on my compact.

The 50/12 is plenty of gear for me for sprinting, unless there's a major tailwind or downhill sprint. Most of the sprints in my races tend to be uphill, and there, it's my legs holding me back and not my gearing. My cassette is a bit spaced out, but I don't have a big problem finding the right cruising gear. It can get more challenging in a TT, and sometimes it can be hard to draft off of someone with vastly different gearing at the low end of the cassette (where the jumps between cogs is greater for me).

As for descending, I can hit over 40mph on descents where I've outspun my hardest gear. That's fast enough for me. Depending on what's next, that momentum may not do that much for the next climb. It certainly won't help in mountain regions where you have really long climbs and really long descents. It only helps on rolling terrain where you are constantly going up and down. There, usually the descents aren't enough that I'm really wishing I had a 53 up front. In fact, I like being able to pop over some rollers in the 50 and not having to shift so much.

I don't have any problems staying with a group or riding for 4+ hours in the mountains because of my compact. If I can't keep up, then a triple isn't really going to help me much. I'd be able to spin a little faster, but I'm still not keeping up with the boys running standard cranksets. My compact only *possibly* holds me back on the flats when I'm getting dropped at 30+mph, but really, would i be able to sustain that speed with harder gears for any longer? Doubtful.

I don't think that distance makes much of a difference or being a strong casual rider (whatever that means) versus a strong serious rider or a racer or whatever. Instead, crankset preferences seem to have a lot to do with riding style, strength, terrain, joint health, and similar factors. For example, if I'd be hitting those 20% grades regularly, I'd want a triple to 1) keep my knees happier, and 2) reduce the chance that I'd have to get off and walk because of #1 or when my fitness lags. Overall, the compact works just fine for me.

Also, based on your group ride examples, it seems like a triple is needed because of your terrain. As a counter example, I ride with one faster group back home and I'm probably the only one with a compact (everyone else has standard gearing and itty bitty cassettes)--because it is FLAT. How long you ride or how strong you are and what your preferred cadence is relative to your strength is only part of the equation.

lunacycles
10-20-2008, 06:17 PM
Switching a bike like the Madone to a triple with mountain bike-like gearing in the rear (anything lower than 27t, usually) will not only necessitate a new cassette, but also new brifters (and sometimes new derailleurs). MTB cassettes (11-32, 11-34) are 9 speed and the Madone is set up for a road 10-speed, hence necessitating different shifters if you make that switch--in order to shift properly.

So it is a major deal, labor and parts wise, to make the change (basically a new drivetrain), and don't be surprised if the LBS has to charge you something additional to the bike price to secure both the sale and any kind of profit. That being said, if you really want the low gear options, the time to decide that is when you are purchasing the bike as the shop will be most willing to do what is necessary at minimal extra charge in order to get the sale.

If set up properly, a triple crank shifts as well as a compact (often better, imo), and adds more options at minimal weight penalty.

Margo

madscot13
10-20-2008, 06:23 PM
I ride a compact (50/36) with a 12-27 cassette. That is equivalent to a 50/34 with a 12-25. I struggle in the mountains only when the grades get upwards of 15% as well. Over 20% is really really tough. However, long sustained climbs from anywhere in the 6-12% range is doable. I'm thinking of taking my old frame and putting a 50/34 on it (using my same cassette) to get just one more gear for riding the mountains.

My compact is perfect for my usual terrain and racing. I run out of gears on the top end more often than on the low end. If I lived in the mountains, I might prefer a triple, but I think even then I'd be more inclined to just put more gears on the back--like maybe a 50/34 with a SRAM or DA7900 cassette with a 28 cog. It's not that much of a difference in gear inches, but my current gearing is *almost* enough for steep grades.

where do you go for local mountains? I'm not too bad with the hills around here, but I would like to get better on steeper climbs for the spring.

tulip
10-21-2008, 06:18 AM
where do you go for local mountains? I'm not too bad with the hills around here, but I would like to get better on steeper climbs for the spring.

Are you in MN or DC? If you're in DC, go west to the Shenandoah, Blue Ridge Parkway, Harrisonburg. Skyline Drive from Front Royal to Big Meadows is a great ride--stay over night at the Lodge and come back "down" (almost as much climbing as "up" the next day. Of course, you will need access to a car to get there. I drove there, stayed overnight at the Super8 in Front Royal, rode up, stayed at the lodge, rode down, and drove home. I have a compact double and I was fine. In fact, too much empty spinning gives me knee pain so I'm better off pushing a bit.

You can also find some decent climbing around Purceville in Maryland. Or up towards Gettysburg, PA. Lots of options, but a car is necessary to get there.

aicabsolut
10-21-2008, 07:55 AM
where do you go for local mountains? I'm not too bad with the hills around here, but I would like to get better on steeper climbs for the spring.

I go to the Charlottesville area and near Staunton for more hills, but I haven't done the mountain climbs there (such as the climb up to Skyline--once you're on Skyline Drive it's about as rolling as anywhere else in the area).

I go to West Virginia just on the other side of the Valley for the closest mountain climbs. Those are pretty challenging--they don't start throwing in switchbacks until the climbs get REALLY steep. Otherwise, it's just long, mostly straight shots up. That makes descending more fun too (tight, steep, narrow road switchbacks coming down are almost as bad as going up).

check out this place: www.lostriverbarn.com
They're about booked up for the good dates this spring already. The barn is situated at the top of a 2,000ft high mountain. The only way to get home from any side is pretty much straight up for 5-7 miles.

TBird
10-24-2008, 07:26 PM
Thanks again everyone, this is like a crash course in bicycle mechanics. I have a question that may be a silly one. I understand that in the front, the big chain ring is for more speed/power and progressively smaller ones are more for climbing. I also understand that in the cassette in the back, the opposite is true—the bigger the cog (ie, greater number of teeth), the lower the gear.

So my question is this: how do I compare two different cofigurations? For example, how different would it feel to climb in 34 front /25 rear versus, say, 36 front/ 27 rear? (If those are even possible configurations.) You can’t just add the numbers for a comparison. So is it just be experience that you know? Would I even notice the difference? As I demo compacts vs triples, it’s hard to gauge these subtleties. I can only be on one bike at a time, after all, and even if I play with bikes back to back climbing hills, I’m obviously more fatigued the second time around. On the Trek I am considering, the lowest gear combination is 34/25 on the compact, 30/27 on the triple. Is that a huge difference--one gear? Two gears? They only have the compact for me to demo.

Maybe I’m overthinking this, but I do keep getting mixed reactions on the compact vs. triple debate. I visited a second LBS and they, too, thought the compact was the way to go, saying that it shifted much smoother. (And they had both compacts and triples on the floor, so no apparent bias.) I also want to make sure I consider some of the points some of you have made, such as making sure I don’t sacrifice gears in “my” typical spinning range.

And frankly, at this point, I’m just curious about how this gear business really works. I had never even contemplated the term “gear inches” until aicabsolut mentioned it. The big ring/little ring thing seems so counterintuitive to me! :eek:

OakLeaf
10-25-2008, 04:56 AM
Here's Sheldon Brown's gear calculator (http://www.sheldonbrown.com/gears/), to compare various setups. That whole site has a wealth of technical information. RIP Sheldon.

It's really not that complicated. You want to know for every revolution of your legs, how far will your rear (drive) wheel travel? Let's say you're in a gear where your rear cog has the same number of teeth as your front one. Maybe a 30x30. (That's a very low gear, stock road bikes don't normally go that low, but mountain bikes do - anyway just for the sake of discussion.) For every revolution of your crank, your rear wheel will also make one revolution.*

Okay, now shift your imaginary derailleurs into a gear where your rear cog has exactly half the teeth of your front one. Say it's a 42x21. Now, every time you move your legs and crank one revolution, your rear wheel will make TWO revolutions. So you're going twice as far for every revolution of your legs (faster given a fixed cadence), but you also have less mechanical advantage (you have to exert more force on the pedals to go the same speed).

Bigger cog in front = more revolutions of the rear wheel per crank revolution ("more speed"); bigger cog in back = fewer revolutions of the rear wheel per crank revolution ("more power").

HTH to get you started. There's more to think about, but that's a beginning.


*"Gear inches" is based on the diameter of the wheel, not the circumference. I don't know why.

TBird
11-23-2008, 09:26 PM
This is a belated "thank you" to everyone who offered advice on my compact vs. triple conundrum. After a lot of demo-ing and bike shopping, I ended up still back lusting after the original Trek Madone 5.1 with the compact that I had fallen in love with. But here's the best part: I convinced the LBS to swap out the compact for a triple that was on a men's Madone! All it took was a sixer of Jubilale (a great Deschutes seasonal brew).
I've only logged about 100 miles on my dreamy new bike, but I am SO glad I went with the compact. That lowest granny gear has already seen a lot of use.
Thanks again. This is such a great community of folks!

tantrumbean
01-17-2009, 01:35 AM
This thread on another forum convinced me a triple would be a good idea:

http://www.cyclechat.co.uk/forums/showthread.php?t=25303

jobob
01-17-2009, 08:02 AM
All it took was a sixer of Jubilale (a great Deschutes seasonal brew).

You have excellent taste in bribes. :D