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Old 07-10-12, 06:58 AM   #1
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Does this sound like an ok granny ring alternative?

Hi

I am buying a road bike, a Lapierre AUDACIO 400 DB. Its my first road bike and I'm a bit green. As indicated, it has two front rings but I was originally looking for a 3 ring but there are none available in my size.

The shop have told me that they will put an extra small ring on the back of the bike which will work equally as well as having a third ring on the front. As the shop is really reputable and the guys know their stuff this seems reasonable, but I thought I'd put it out there and see what you guys think?

I will probably use the bike for some alpine biking next year so there will be a lot of uphill work. My primary reason for thinking I need a third ring though is because I have a bad knee which I've blown once already doing another sport and as that put me out of commission for 6 months I don't want to run the risk of putting it under too much pressure again.

Does the small ring on the back sound like a good option?

Thanks for the help.
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Old 07-10-12, 07:03 AM   #2
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no
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Old 07-10-12, 07:12 AM   #3
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Thanks- can you tell me why?
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Old 07-10-12, 07:19 AM   #4
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They would have to install a cassette with a LARGER rear cog (12-32) to give you lower gears (and it won't be an "extra" - you already have 10 cogs in the rear). You will need to change rear derailleur as well. What you lose in the bargain is that your gears will be more widely spaced, but compared to things in the "olden" days when we had only 5-6 gears to work with it's still managable. But the 34/32 may still not be low enough. Although there are few things potentially better for your knees than biking (no impact or torsional stress) you can still stress them with too high a gear range in mountainous territory. Note though, that not all "alpine riding" is hard - depends on where you are. Most places in Europe include fairly steep grades, but main roads in the Rockies are pretty tame, due to restricting the grade so that trucks can manage them.

It may a bit late now, but I find it hard to believe you could not find a suitably sized bike with a triple, unless you are otherwise limiting yourself by looking for ultralight bikes. Converting to a triple will be very expensive - Crankset, bottom bracket, front and rear derailleurs.

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Old 07-10-12, 07:23 AM   #5
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That bike comes with a compact double.

50 T/34 T chain rings with a 12-28 cassette.

With bad knees you would most likely want a triple chain ring like 50/39/24 with a 12-34 cassette.

T is the number of teeth on the rings and cassette cogs.

http://i256.photobucket.com/albums/h...-24/503934.jpg

11/34 cassette:

http://i256.photobucket.com/albums/h...5-39-24002.jpg
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Old 07-10-12, 07:31 AM   #6
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Triple cranks for road bikes are on there way out, SRAM has WiFLi which gives a 32T largest on the cassette, and Shimano now has upto a 30T, combined with a 50/34 crank, you are getting a very similar range to a triple with a 25T cassette.

The Lapierre your looking at already has a 12-28 cassette as standard spec, this should get you up most hills. The spec sheet doesn't say what the RD is (SS or GS), if it has a GS long cage, it will take at least a 32T.

Not sure why you aren't happy with the advice that the bike shop is giving you, you seem to think that the bike shop you are going to is reputable, why don't you trust their judgement? If they are going to fit a larger cassette, they will know if it needs a change in RD.
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Old 07-10-12, 08:21 AM   #7
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Thanks- can you tell me why?
Putting a smaller cog on the front makes it easier to pedal. Putting a smaller cog on the back makes it harder to pedal. Putting an extra small cog on the back is the opposite of what you want.

Think about it: Your highest gear is when you're on the biggest chain ring in front and the smallest cog in the back, and lowest gear is when you are are the smallest chain ring in the front and the largest cog on the back.
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Old 07-10-12, 08:57 AM   #8
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For many people the typical low gearing offered on most new bikes works well. For any number of reasons, such gearing is not low enough. Among those reasons is age as in my case, or suspect knees such as in your case or the need to ride frequently in steep terrain and or a new rider who has not yet developed good leg strength and cardio-vascular improvements. With no previous experience to go on, you have no basis with which to judge bike gearing.

A 34 T chain ring in the front and a 34 T lowest cog in the back is a 1:1 ratio which is quite low but is it low enough? If not low enough it will be expensive to change out the bottom bracket, cranks and chain rings to a triple setup and a triple shifter for those chain rings will have to be bought and installed as well as the front derailer. If you understand this much in advance, you will at least be making a somewhat informed decision with regard to costs.
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Old 07-10-12, 09:16 AM   #9
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1:1 Ratio.. if both are same size, 1 crank rotation = 1 wheel rotation..
as if a unicycle, with that size of wheel, if, say, a 28" wheel ,
then the next lower gear, given you have a 34t chainring,

is 24".. 2 feet... no shame in walking a steeper hill..
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Old 07-10-12, 10:21 AM   #10
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The spec sheet doesn't say what the RD is (SS or GS), if it has a GS long cage, it will take at least a 32T.
Not true. Shimano lists the max. cog size for both SS and GS a 27 teeth for Tiagra RD. I have heard reports that many get their Shimano derailleurs to work with 30 teeth or more, but also many who cannot get it to work properly with even 1 tooth over the max size. Certainly saying it will work with 'at least' 32 teeth is incorrect... perhaps 'at most 32 teeth, if you are very lucky.'

Across the board there is no difference in max cog size between SS and GS models. THe only difference is the amount of chain-takeup - the capacity, which is the diff. between smallest and biggest cog plus diff. between smallest and biggest chainring. For Tiagra SS model the capacity of the SS (short cage) is 31 teeth, and the capacity of the GS is 39 teeth. Both have a largest max cog size of 27 teeth. Source link

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Old 07-10-12, 11:10 AM   #11
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Not true. Shimano lists the max. cog size for both SS and GS a 27 teeth for Tiagra RD. I have heard reports that many get their Shimano derailleurs to work with 30 teeth or more, but also many who cannot get it to work properly with even 1 tooth over the max size. Certainly saying it will work with 'at least' 32 teeth is incorrect... perhaps 'at most 32 teeth, if you are very lucky.'

Across the board there is no difference in max cog size between SS and GS models. THe only difference is the amount of chain-takeup - the capacity, which is the diff. between smallest and biggest cog plus diff. between smallest and biggest chainring. For Tiagra SS model the capacity of the SS (short cage) is 31 teeth, and the capacity of the GS is 39 teeth. Both have a largest max cog size of 27 teeth. Source link


Have you actually tried this? I have, currently using a 105 (5700) GS with a SRAM PG1070 11-32 works fine, but wouldn't work with a 105 (5700) SS. Shimano under report the max capacity (rightly so) and you can also use the B screw trick to increase further.
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Old 07-10-12, 11:24 AM   #12
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Yes I have. I had a GS derailleur with a 30 tooth and the upper pulley was grinding against the 30 until I found a longer B-tension screw to use. It would not have worked with a 32.
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Old 07-10-12, 11:35 AM   #13
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play around with a graphical gear calculator.

You should quickly realize that two chainrings will never be able to compete with three for low range.

http://home.earthlink.net/~mike.sherman/shift.html


A typical road triple will have 52-39-28
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Old 07-10-12, 11:59 AM   #14
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34/28 isn't horrible, it'll be around 32 gear inches. Just make sure the saddle isn't too low, practice spinning rather than mashing, and get off and rest/stretch if your knee ever starts to give you trouble. (My left knee is kind of sensitive, so I'm in the same boat.)
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Old 07-10-12, 01:01 PM   #15
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Originally Posted by Trifides View Post
I am buying a road bike, a Lapierre AUDACIO 400 DB. Its my first road bike and I'm a bit green. As indicated, it has two front rings but I was originally looking for a 3 ring but there are none available in my size.
That bike is available with triple crank in all the same sizes as the one in compact crank. DB=standard crank, CP=compact TP=triple. Your shop may be reputable but for some reason they want to sell you what's on the floor rather than order the one you want in your size.

But if it's just the low end gear you're concerned with, a 34x32 is a pretty common configuration for alpine gearing - compact crank plus MTB cassette and long cage derailleur so if that's what the shop is offering it's a pretty good match for you.

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Old 07-10-12, 01:25 PM   #16
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Hi
The shop have told me that they will put an extra small ring on the back of the bike which will work equally as well as having a third ring on the front
They're ignorant (and you should go to a different bike shop) or they know better and are trying to sell you what they have in stock (and you should definitely go to a different bike shop).

Quote:
Does the small ring on the back sound like a good option?
Thanks for the help.
No.

1. If you really need it the triple can go much lower, as in 24 x 34. To match that with a compact double you'd need to run 34 x 48. Unfortunately you're not going to get anything bigger than a 34 cog which will put 40% more stress on your bad knee at the same speed.

2. With the same rear cassette you can deliver nearly 50% more power at a given cadence using a 39 middle ring on a triple instead of a 34 on a double when you continue to eschew the small cog and 90% more when you don't (the middle ring splits the difference between where the two rings are on a double so the chain line isn't unreasonable and you're not going to rub the chain on the big ring). That's huge if you'd like to get through an intersection before the pedestrian counter gets to zero and the light turns yellow.

3. With the triple you can spend a lot of time riding close to the middle of the cassette where the chain line's better for lower noise and there's a lot less shifting between rings. For instance, with a 50-40-30 x 13-14-15-16-17-18-19-21-23 triple I spent a lot of time in 40x17 right in the middle of the cassette while at the same speeds on 50-34 x 13-14-15-16-17-18-19-21-23 I was riding either 50x21 or 34x14 which would likely be followed with a ring change (34x14 is a perfect cruising gear up to about 19 MPH and 50x21 down to about 17 MPH. With rest days, head-winds, and false flats I spend a _lot_ of time in that range and slightly beyond). Although I initially bought into the mantra that two rings were better than three I quickly realized how wrong that was.

4. In a lot of cases you can have both tighter spacing and at least as much range using a triple instead of a compact double. Compact cranks, more cogs (Campagnolo will give you 11) and traditional cassettes with one big bail-out cog spliced on the end (Shimano Mega Range, SRAM road cassettes with a 12 starting cog) offset some of the advantage.

50-34 x 11-34
and
53-39-26 x 12-25
and
53-39-24 x 12-23

all effectively have the same range; although 11-34 usually runs

11-13-15-17-19-21-23-25-28-34

with 10 cogs while 12-25 runs

12-13-14-15-16-17-19-21-23-25

and 12-23

12-13-14-15-16-17-18-19-21-23

Lots of cyclists really want one-tooth jumps through the 17 cog and some of us like that through the 19.

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Old 07-10-12, 02:45 PM   #17
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Yo Trifides: From all of the above posts it is easy to see that there is quite a bit of info to absorb in making a rational decision. Some of the info is from very fit folks who have been cycling for a long time and don't understand that not all of us are not particularly fit or young. For example, I'm a healthy 73 y.o. man who has cycled 7500 miles over the past 2.5 years and I'm asthmatic. Without my inhaler, I'm toast. It is for this reason that I use a triple chain ring. Each year, in spite of my limitations, I become slightly stronger and faster to the point that I, maybe enjoy is the wrong word, but find satisfaction in showing improvement in my cycling and climbing. I have modified the gearing on my bike by quite a bit to the point that I can make it up any hill in my area and make it up hills with a bit of weight in panniers for modest distance bike touring. You will have different limitations, strengths, goals and your bike should reflect your reality.
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Old 07-10-12, 02:54 PM   #18
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Triple cranks for road bikes are on there way out, SRAM has WiFLi which gives a 32T largest on the cassette, and Shimano now has upto a 30T, combined with a 50/34 crank, you are getting a very similar range to a triple with a 25T cassette..
That's not strictly true as Campy is reintroducing triple cranks in some of their main road groups, Athena and Centaur for sure, next year. And, Shimano has continued triples in at least 105 for the time being. You are correct that the newly announced 2013 105 rear derailleurs will accept a 30T in SS and 32T in GS form. SRAM has, for reasons only they know, completely avoided triple road groups through their history and WiLi is a poor substitute.
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Old 07-10-12, 03:07 PM   #19
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SRAM has, for reasons only they know, completely avoided triple road groups through their history and WiLi is a poor substitute.
As well as I think triples work for many riders as a profit profit driven bike company not targeting a niche market I might do the same.

Fewer SKUs serving the same market mean more profits through the entire distribution chain with lower tooling costs, lower inventory costs, and lower losses when left overs are closed out at the end of the season.

By skipping triples they've eliminated a bunch of crank SKUs (gruppo x length x ring variations), several front derailleur SKUs (gruppo), several rear derailleur SKUs (gruppo), perhaps a few (gruppo) shifter SKUs (Campagnolo left levers go both ways), and more bike SKUs.

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Old 07-10-12, 04:09 PM   #20
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As well as I think triples work for many riders as a profit profit driven bike company not targeting a niche market I might do the same.
From the company's economic standpoint you are absolutely correct but from a rider's standpoint, SRAM is never on my radar as a component supplier.

At the Philly pro race last month Campy had a demo booth and I mentioned to their local rep how pleased I was Campy had again added triple cranks to their lineup. He was less than happy about it saying; "Campy should always stick to serving the racers." I guess he doesn't realize the clientel that can afford premium priced components is aging.
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Old 07-10-12, 04:22 PM   #21
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From the company's economic standpoint you are absolutely correct but from a rider's standpoint, SRAM is never on my radar as a component supplier.
Right. I don't own any Shimano or SRAM components.

Quote:
At the Philly pro race last month Campy had a demo booth and I mentioned to their local rep how pleased I was Campy had again added triple cranks to their lineup. He was less than happy about it saying; "Campy should always stick to serving the racers." I guess he doesn't realize the clientel that can afford premium priced components is aging.
The local rep works for the sales department which doesn't control what gets built.

The guys in the marketing department obviously are catering to a growing population whether from the American obesity epidemic, cycling becoming the new golf with financially well off less fit participants, or middle aged spread.

They've given us bigger cogs, more compact cranks, and revived the triple for the 11 speed era.
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Old 07-10-12, 07:39 PM   #22
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The guys in the marketing department obviously are catering to a growing population whether from the American obesity epidemic, cycling becoming the new golf with financially well off less fit participants, or middle aged spread.
Or perhaps to people who don't view their bikes as expensive toys.
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Old 07-10-12, 07:54 PM   #23
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At the Philly pro race last month Campy had a demo booth and I mentioned to their local rep how pleased I was Campy had again added triple cranks to their lineup. He was less than happy about it saying; "Campy should always stick to serving the racers."
Groan. That is as shortsighted as saying that Ferrari should stick to building race cars, and stop building street-legal sports cars. Where does he think the bulk of the sales are made???
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Old 07-11-12, 02:44 PM   #24
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Doubles do have some advantages over triples, especially if you're using indexed front shifting; making this work right with a triple is unpleasant, as Tiagra front shifters don't have useful trimming ability (as far as I know)*. I would suggest either:

1) swap the cassette for a 12-36 HG-61 and the derailleur for a long-cage Deore; this shouldn't be terribly expensive (~$60 + ~$60?), giving you a 34-36 low, which should be great for hills but leaves you with some big jumps in the middle

2) get a cheap old MTB triple (24/26-36-46/48 or some such) from eBay, a cheap square taper BB in the right length, a new left brake lever, and a downtube or bar end friction shifter for the front (not sure if you have downtube braze-ons) (maybe ~$50 + ~$15 + ~$15 + ~$10, if you have a local bike co-op); this will let you use a tighter road cassette, but the mechanical work will be more involved.

Are you planning on doing the work yourself?

*The double model has several trim options, apparently (thanks, DCB0!). Friction is still better.

Last edited by dave35; 07-11-12 at 03:33 PM. Reason: Had wrong information.
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Old 07-11-12, 03:18 PM   #25
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Doubles do have some advantages over triples, especially if you're using indexed front shifting; making this work right with a triple is unpleasant, as Tiagra front shifters don't have useful trimming ability (as far as I know). I would suggest either:

1) swap the cassette for a 12-36 HG-61 and the derailleur for a long-cage Deore; this shouldn't be terribly expensive (~$60 + ~$60?), giving you a 34-36 low, which should be great for hills but leaves you with some big jumps in the middle

2) get a cheap old MTB triple (24/26-36-46/48 or some such) from eBay, a cheap square taper BB in the right length, a new left brake lever, and a downtube or bar end friction shifter for the front (not sure if you have downtube braze-ons) (maybe ~$50 + ~$15 + ~$15 + ~$10, if you have a local bike co-op); this will let you use a tighter road cassette, but the mechanical work will be more involved.

Are you planning on doing the work yourself?
Shifting on a double is quicker and cleaner as the derailleur can be slammed 'lock-to-lock' and it will work, while triples need to be set up more carefully. But triples can still easily be made to shift well with modern ramped and pinned chainrings. And Tiagra front shifters DO have a trim for eliinating rubbing.

Your solutions for the removing the complicated triple setup are technically correct, but are actually waaa-aaa-aay more complicated than proper adjustment of a triple FD on a new bike.
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