roadbike crankset 50/34T paradox

[cardcard2001]

I bought a RB recently, it comes with Shimano 105 5600 groupset and a FSA 50/34T megaexo compact crankset.

I rode MTB hardtail before with 26 *1.25 slick tyres, I rode on flat road most of the time and use 32/22T and 11/12T gears mostly and my average speed were about 35km/h on 32+11/12 and about 22km/h on 22+11/12, I rarely use the 44T, just on few downhills

Now I switch to RB, and I query is the 34T compact (cassette is 12-25) may be too small (gear ratio) for my situation. I get use to ride on small teeth combination before, e.g. 53/16 and 39/12 are about the same gear ratio and I prefer to ride on the 39/12 for the sensation of smoother and quiter gears. I just don't know this habit is correct or wrong ...

Therefore I'm planning to change to 53/39 or 50/39, my budget is limited however. what would U recommend ?

1. change the inner chainring only (however, 110BCD 39T seems rare in my area)
2. change to 11-23 cassette (this helps little indeed)
3. change crankset (how about the Shimano 5600 50/39 or 53/39? some ppl said it is not stiff enough, even poorer than the 5501 crankset, is that true ? and do I need to replace for a longer chain if I use the 53/39?)

or actually I don't need to change any and I should adapt to the 50T+high gear cog setting ? I get wired ...

 

[Lonnie Utah]

Get the 11x23 casette. That's the easist change to make (ie you can do it yourself with a $5 tool). And if that's not enough, get a 36 or 38 tooth inner ring. I would be a bit worried about cross chaining in the 34x12 combination. You should be in the big ring at that point. The 34x12 combination is esentially the same as the 50x17 (5.6 vs 5.8 gear ratio)
http://www.sheldonbrown.com/gears/

You can get a FSA 38 tooth 110 BCD ring for $30 + Shipping. Not a bad deal at all. With a new 105 or Ultegra casette and new small chain ring, you should be out no more than about $100.

http://www.excelsports.com/new.asp?page=8&description=Chainring+Compact+Small&vendorCode=FSA&major=1&minor=12

http://www.excelsports.com/new.asp?page=8&description=105+CS5600+Cassette+10+Speed&vendorCode=SHIM&major=1&minor=10

 

[John M]

I bought a RB recently, it comes with Shimano 105 5600 groupset and a FSA 50/34T megaexo compact crankset.

I rode MTB hardtail before with 26 *1.25 slick tyres, I rode on flat road most of the time and use 32/22T and 11/12T gears mostly and my average speed were about 35km/h on 32+11/12 and about 22km/h on 22+11/12, I rarely use the 44T, just on few downhills

Now I switch to RB, and I query is the 34T compact (cassette is 12-25) may be too small (gear ratio) for my situation. I get use to ride on small teeth combination before, e.g. 53/16 and 39/12 are about the same gear ratio and I prefer to ride on the 39/12 for the sensation of smoother and quiter gears. I just don't know this habit is correct or wrong ...

Therefore I'm planning to change to 53/39 or 50/39, my budget is limited however. what would U recommend ?

1. change the inner chainring only (however, 110BCD 39T seems rare in my area)
2. change to 11-23 cassette (this helps little indeed)
3. change crankset (how about the Shimano 5600 50/39 or 53/39? some ppl said it is not stiff enough, even poorer than the 5501 crankset, is that true ? and do I need to replace for a longer chain if I use the 53/39?)

or actually I don't need to change any and I should adapt to the 50T+high gear cog setting ? I get wired ...

I agree with Lonnie to get larger inner chainring for your compact if you don't need the lower gears for the terrain where you ride. 38T with 11-23 should do OK for you and use the large chainring when you are going faster. Thats what it is there for. You will also get less chain/cassette wear riding more towards the middle of the cassette.

 

[alfeng]

I bought a RB recently, it comes with Shimano 105 5600 groupset and a FSA 50/34T megaexo compact crankset.

I rode MTB hardtail before with 26 *1.25 slick tyres, I rode on flat road most of the time and use 32/22T and 11/12T gears mostly and my average speed were about 35km/h on 32+11/12 and about 22km/h on 22+11/12, I rarely use the 44T, just on few downhills

Now I switch to RB, and I query is the 34T compact (cassette is 12-25) may be too small (gear ratio) for my situation. I get use to ride on small teeth combination before, e.g. 53/16 and 39/12 are about the same gear ratio and I prefer to ride on the 39/12 for the sensation of smoother and quiter gears. I just don't know this habit is correct or wrong ...

Therefore I'm planning to change to 53/39 or 50/39, my budget is limited however. what would U recommend ?

1. change the inner chainring only (however, 110BCD 39T seems rare in my area)
2. change to 11-23 cassette (this helps little indeed)
3. change crankset (how about the Shimano 5600 50/39 or 53/39? some ppl said it is not stiff enough, even poorer than the 5501 crankset, is that true ? and do I need to replace for a longer chain if I use the 53/39?)

or actually I don't need to change any and I should adapt to the 50T+high gear cog setting ? I get wired ...

"Universal" BMX chainrings (110BCD) which will work with a 1/8" chain come in sizes between 34t & 48t.

They should work with 8-speed & 9-speed drivetrains ... they may be problematical with a 10-speed drivetrain, but perhaps not.

 

[gclark8]

My MTB has 28/38/48 and 11-28, its got to be a real hill that gets me out of the middle ring.

Comparing the MTB+slicks to the road bike, I assume you are on 700c wheels. This ups the gearing by 10% first. The Road bike is faster, most times, so a few more %.

If you try a 39/50 or 39/53 you should be using the middle of a 12-25 cassete most of the time on the flat. You may then find the missing 16 and 18 tooth (9 speed) a bit of a problem, gaps in the gearing, I did, so a 13-23 (with 52 or 53 big ring) solves that. My bike is a Triple, the 42 is too big for local slow riding, 36 would be perfect but the 13 cassette will be too low. So its all compromise, 39-13 for local riding and change to a 42 for tri training, Not likely! I will stay with the triple and put a 36 tooth on the inner. So for me 36/42/52 and 13-23 gives the best options.

 

[mnr3]

solution 1 (easiest): get used to staying in the 50x16 or so; you won't have to use your front derailleur as much, and if it's not quieter than your 34x12, then something is wrong with your setup.
solution 2 (may please you better and make someone else happy): find someone who wants to move to a compact crank (new craze) and swap them if they have a good quality and condition 53x39. if you live in the flatlands there is no reason for a 34 or a compact crank. sell it and get a standard size; the latter are getting plentiful as people switch over to compacts

 

[cardcard2001]

solution 1 (easiest): get used to staying in the 50x16 or so; you won't have to use your front derailleur as much, and if it's not quieter than your 34x12, then something is wrong with your setup.
solution 2 (may please you better and make someone else happy): find someone who wants to move to a compact crank (new craze) and swap them if they have a good quality and condition 53x39. if you live in the flatlands there is no reason for a 34 or a compact crank. sell it and get a standard size; the latter are getting plentiful as people switch over to compacts

thx all guys for suggestions,

I had look around most bike shops in my area, they don't even sell chainring separately, one can help me order, including shipping fee, it need about US$ 44 for the 38T.

My main problem is limited budget.

If I change the crankset. I need add ~US$100 for new crankset and chain. What this really helps may be the inner chainring only, I think 50T should be quite suitable for me.

If I change the chainring only, I probably need to leave the 34T useless, I won't think someoe will have interest on a compact chainring in my area

Another question, could someone recommend some shops that sell the mentioned chainring online that is reliable and able to ship to Asian countries in reasonable price tag ?

Besides, what is the difference on power output for same tooth chainring on different bolt circle diameter crankarm (e.g. 39T on 110 vs 130)?

thx!

 

[mnr3]

Besides, what is the difference on power output for same tooth chainring on different bolt circle diameter crankarm (e.g. 39T on 110 vs 130)?

thx!

there is no difference, just like there is no difference between being in a 34, 39, 44, 50, 52, or 53 tooth ring in the front, combined with whatever cog in the back will give you the same ratio. it is the ratio that matters, which translates into how many times your wheel turns for how many times your crank turns. does not matter how you get there, which is why I still don't understand why you want to make this change. if it's for more "power output" or smoother spinning, the answer is even cheaper: training and practice good pedaling technique! the power output equals the power input: you, the motor.

 

[Insight Driver]

I might suggest before you go and change anything is ride your bike a lot and find out what gears you use the most. Find out by riding if there are gaps that you wish were covered. There is such a difference between a mountain bike setup and a road bike setup that you can't compare the two because its an apples to oranges comparison. The compact setup you have is a typical one and suits most people who ride road bikes in all but very hilly areas. If you have very hilly areas then it would make more sense to get a 12/27 cassette.

Only with riding experience will you find out what your optimum gearing is. It just sounds to me by what you posted is that you see the difference between your mountain bike gearing and your road bike gearing and think they should be equivalent. Of course, I could be wrong.

 

[mnr3]

I might suggest before you go and change anything is ride your bike a lot and find out what gears you use the most. Find out by riding if there are gaps that you wish were covered. There is such a difference between a mountain bike setup and a road bike setup that you can't compare the two because its an apples to oranges comparison. The compact setup you have is a typical one and suits most people who ride road bikes in all but very hilly areas. If you have very hilly areas then it would make more sense to get a 12/27 cassette.

Only with riding experience will you find out what your optimum gearing is. It just sounds to me by what you posted is that you see the difference between your mountain bike gearing and your road bike gearing and think they should be equivalent. Of course, I could be wrong.

to which you could add the fact that a mountain bike wheel is smaller; therefore even the same gear is different: a 39x15 is harder to turn over on a road bike because of the bigger wheel, so at the same speed you wheel need a smaller gear for a road bike. of course road bikes are faster, so these tend to cancel out a little. I think someone posted the sheldon brown site on gearing on the first page. read and understand that, or another site on gear inches alone (sheldon likes that ratio stuff).
I would agree with previous post that you should ride before you buy anything. cranks and crank components are expensive, relatively speaking