crank and chain ring
03-17-08, 03:12 PM
#1
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crank and chain ring
I have no bike mechanic skills so educate me please. My mechanic says my current triple ring crank set will need replacement in the next few months. Due to my riding level and our lack of hills he suggests that I change to a double ring or even a compact double. What are the pros and cons of this and what is the difference between a double and a double compact crank set?
03-17-08, 04:27 PM
#2
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In teeth, a double is usually 53/39 or 52/39 a compact is usually 50/36 or 50/34.
The advantage of the compact is lower gearing. A cmpact can be converted to regular with different chainrings, the inverse is not true since the BCD (bolt circle diameter) on a standard double can only go as low as 38 teeth (more commonly 39).
The advantages of either double over a triple is bling points because among the elitists a triple shows weakness... to most riders, there isn't a lot of difference. A triple will usually give a lower gear than even the compact double.
If you don't ever use the smallest ring on front, a double would be fine. It would require a new crank/rings and bottom bracket, plus some adjusting to make the switch.
If the bottom bracket is not worn, then a triple might be cheaper... if the bottom bracket needs to be replaced, then a double makes slightly more sense.
My thought is that with a triple you can always just not use the lowest gears... if you have a double, you don't have the option. But I am old, overweight and in a mountainous area.
The advantage of the compact is lower gearing. A cmpact can be converted to regular with different chainrings, the inverse is not true since the BCD (bolt circle diameter) on a standard double can only go as low as 38 teeth (more commonly 39).
The advantages of either double over a triple is bling points because among the elitists a triple shows weakness... to most riders, there isn't a lot of difference. A triple will usually give a lower gear than even the compact double.
If you don't ever use the smallest ring on front, a double would be fine. It would require a new crank/rings and bottom bracket, plus some adjusting to make the switch.
If the bottom bracket is not worn, then a triple might be cheaper... if the bottom bracket needs to be replaced, then a double makes slightly more sense.
My thought is that with a triple you can always just not use the lowest gears... if you have a double, you don't have the option. But I am old, overweight and in a mountainous area.
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03-17-08, 04:33 PM
#3
Really Old Senior Member
Cons-
You'll probably need a new BB to do it "right".
You won't have the "bail out" ring in case you ever need it.
You can probably still use your FDER, but it may not give the "best" shifting possible with a double. Shifting should be OK though.
Pros-
1/3 fewer gears to keep track of. It's not how many gears you have, but how many "useful" gears you have.
I'm in a similar situation- I don't do hills! I've kept my "granny" ring just in case I run into a hill that wasn't "on the schedule", however!
I've gone to a 12-23 cassette, so I'd be pretty limited for a bail out gear using my 38T ring as the smallest.
I;ll assume you have a "road" bike.
Typical triples would have a gearing similar to 30-39-52.
A double would be about 39-52 or so.
A compact would be something like 34-50.
What's wrong with the current set up? IF you have a worn ring, maybe just a replacement ring is all you need?
You'll probably need a new BB to do it "right".
You won't have the "bail out" ring in case you ever need it.
You can probably still use your FDER, but it may not give the "best" shifting possible with a double. Shifting should be OK though.
Pros-
1/3 fewer gears to keep track of. It's not how many gears you have, but how many "useful" gears you have.
I'm in a similar situation- I don't do hills! I've kept my "granny" ring just in case I run into a hill that wasn't "on the schedule", however!
I've gone to a 12-23 cassette, so I'd be pretty limited for a bail out gear using my 38T ring as the smallest.
I;ll assume you have a "road" bike.
Typical triples would have a gearing similar to 30-39-52.
A double would be about 39-52 or so.
A compact would be something like 34-50.
What's wrong with the current set up? IF you have a worn ring, maybe just a replacement ring is all you need?
03-17-08, 06:35 PM
#4
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If you go to a double, the other choice is a "cyclocross" crank, such as the Truvativ Elita on my hybrid, with 46/38 rings. Closer spaced gears than a compact double because the high isn't as high and the low isn't as low. The low is low enough with an 11-34 cassette and the high is high enough for my legs.
