Going "compact" options

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Going "compact" options

Postby digbyj » Tue Nov 12, 2013 8:57 am

Hi Folks,
I recently acquired a 2h Trek road bike running 105 as my entrance into road cycling. I'm loving it, but am finding the standard cranks are not matching well with my spindly little legs and the hills of the Yarra Valley!
Have done a bit of googling as you do and wanted some local responses to the following: do I buy a compact crankset 50/34, or do I replace my rear cassette? Will either of these mean replacing derailleurs or will adjustment suffice?
I am very budget conscious at the moment as we have a baby on the way so am looking at the cheapest/simplest way to increase my ride locations around home (ie use more hills!).
Many Thanks and look forward to your responses.
Marcus


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by BNA » Tue Nov 12, 2013 9:09 am

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Re: Going

Postby simonn » Tue Nov 12, 2013 9:09 am

Changing cassette is simpler and cheaper, but whether you can user a larger cassette depends on your existing cassette as it might already be the largest that your and rear derailleur can use.

So...

What size/how many teeth do the smallest and largest sprockets on you current cassette have? (count the teeth if unsure).

Do you have the short or medium length rear derailleur? (photos might be easy to identify, or if you can find the model number on it somewhere).
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Re: Going

Postby Duck! » Tue Nov 12, 2013 1:02 pm

You'll only find a medium cage derailleur when a triple-ring crank is fitted. :wink:
I had a thought, but it got run over as it crossed my mind.
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Re: Going

Postby winstonw » Tue Nov 12, 2013 1:14 pm

I'd suggest buying a compact chainset $183 from ribble.
A new 105 cassette is $54.

take the opportunity to buy an optimal crank length too.
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Re: Going "compact" options

Postby digbyj » Tue Nov 12, 2013 3:05 pm

The cassette is 12-25, my greasy fingers are proof! The chain rings are 52-39 so not sure where that sits in the scheme of things.
I forgot to check the derailleur but sounds like Duck might've cleared that question up.
I'll let the thread roll on for a bit and then make a decision...
Cheers


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Re: Going

Postby simonn » Tue Nov 12, 2013 3:13 pm

Just quickly and using ratios, lower ratio means lower gear, i.e. easier to pedal, but coincidentally makes it more expensive too.

39/25 = 1.56 <- this is your current lowest gear
39/28 = 1.39 <- changing just the cassette to an 11-28. Probably need a new chain too
34/25 = 1.36 <- changing to a compact crankset. Would not need a new chain
34/28 = 1.21 <- changing to a compact crankset and an 11-28 cassette. Probably would not need a new chain

IMHO, the last is the best as you will have a bigger top gear too

52/12 = 4.33
50/11 = 4.54

But it is more expensive. Probably worth getting a couple of chains and rotating through them around every 1000km. That will extend the life of the sprockets and chainrings.
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Re: Going "compact" options

Postby digbyj » Wed Nov 13, 2013 11:20 am

G'day simonn, thanks for taking the time to do some Maths for me! That clears it up for me, I think I may have to keep my eyes peeled for a cheap compact crankset, I figured that was where I was heading.
Cheers


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Re: Going

Postby jasonc » Wed Nov 13, 2013 11:38 am

simonn wrote:39/28 = 1.39 <- changing just the cassette to an 11-28. Probably need a new chain too


I disagree. have gone from 39/25 to 39/28 without replacing the chain. no problems.
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Re: Going "compact" options

Postby ozdavo » Wed Nov 13, 2013 12:35 pm

I'd recommend a compact crank first and see how you go. Also, if budget is a concern, I'd recommend looking at Tiagra 4600 (you will not notice any difference between this, 105 or Ultegra in the crank) http://www.ribblecycles.co.uk/sp/road-t ... himchar465


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