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Newbie cyclist - chain broken and looking to overhaul bike
#1
Hi guys,
Been looking on the web trying to understand various concepts in layman's terms but i eventually decided there's no substitute for experience and so I thought I'd seek help here since the people on this forum seemed polite and intelligent.

Strangely only one side of one link in my chain broke and I've decided this is a good time to change a few components. This is my bike: http://www.bikepedia.com/QuickBike/BikeSpecs.aspx?Year=2011&Brand=Specialized&Model=Allez%20Triple&Type=bike got it around a year ago after the previous incarnation of it was stolen.

Looking to get a new chain (possibly this http://www.amazon.co.uk/Sram-Pc-850-Chain-Speed-Silver/dp/B000VDFQAA/ref=sr_1_10?s=sports&ie=UTF8&qid=1338544943&sr=1-10 ) and maybe a new cassette (http://www.amazon.co.uk/Sram-cassette-PG-850/dp/B003N2CUG4/ref=pd_sim_sg_2 the 11-32 model) as while i cycle I've noticed I never stray from a combination of the largest chainring and 3rd and 2nd (around here it begins to make a worrying grinding-like noise) smallest sprockets so would like a few more options to possibly rasie the overall gear ratio range and stop that sound.

I understand this could all be completely wrong since the most maintenance I've ever done is changing a bottom bracket on an old MTB but would appreciate any advice you could give me on any alterations to make or which components to purchase.

Thanks in advance for any help and I'll try to answer questions as best I can,
Brandon
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#2
First I don't understand why you would want a smaller gear (32 teeth as largest sprocket) when you usually only ride in high gears (large chain ring, small sprockets). Also, on the high gears: is it only down hill where you cycle or do you spin at such a low cadence? Try spinning at least at 90 rpm, it is much better for your knees.
SRAM chains and cassettes are nice, so you probably cannot go wrong with them. I would (probably) not put a MTB cassette on this bike, as the total capacity (total difference of teeth the RD can handle = small-small to large-large combination) of the rear dérailleur will likely be exceeded (look at the Shimano tech docs to find that number for your RD). (I also found a 25 teeth sprocket with the triple crank set on my road bike sufficient for most of the climbing I did in the Austrian Alps last week).
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#3
Thanks for the reply, my cadence is probably lower than that but I've not got a cycle computer with a readout for it so is there a rule of thumb to check it roughly? I wasn't aware that it was a MTB cassette so thanks for letting me know, I'll have a look online and ask at my local shop what would be a suitable replacement.
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#4
(06-06-2012, 10:00 AM)YourFellowMan Wrote:  Thanks for the reply, my cadence is probably lower than that but I've not got a cycle computer with a readout for it so is there a rule of thumb to check it roughly?

90 pedal revolutions per minute works out at 15 every 10 seconds. On a flat straight, where you can comfortably, and safely, look at your watch, or your cycle computer if it has a stop watch or a clock that shows the seconds, count how many times your right, or left, knee or foot reaches the top or bottom of it's stroke in a 10 second period and adjust speed and gears until it's about 15. After a while you should get a sense of what 90 rpm feels like.

You can also count over a 15 or 20 second period: 90/4 = 22.5 revs, 90/3 = 30 revs.

You can also work it out by knowing your gear combination, wheel size and speed: http://www.machars.net/bikecalc.htm
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#5
Thanks for that xerxes, I'll try that. Any recommendations on a good road bike replacement cassette? something similar is fine but I don't want to get ripped off at my LBS because i believe I have been a few times...
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#6
The SRAM PG-850 is available in a road version with 12-23 and 12-26.

The Shimano HG50 is available with a wider range of sprocket options:

12-21 - 12.13.14.15.16.17.19.21
12-23 - 12.13.14.15.17.19.21.23
12-25 - 12.13.15.17.19.21.23.25
13-23 - 13.14.15.16.17.19.21.23
13-26 - 13.14.15.17.19.21.23.26

There's probably very little to choose between them in terms of quality.
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#7
Thanks for all the help guys, I've got my eye on this cassette ( http://www.amazon.co.uk/Sram-Cassette-850-Design-Sprockets/dp/B000NNX2P4/ ) to maximize the chance it'll be compatible with the chain I mentioned in the first post. This cassette has a larger range so would I have to adjust the chain to fit the largest sprocket and the derailleur would sort the rest out?
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#8
Your rear dérailleur will most likely not be able to cope with the large sprockets. Check Shimano's homepage for the specs. You are interested in the "capacity" (how big the teeth difference between large-large and small-small combo is allowed to be, how much "slack" the dérailleur can take up) and the maximum teeth number (how big the biggest sprocket can be). As your bike uses cheap road components you probably cannot use larger sprockets than 27 teeth (maybe 28).
Shimano and SRAM chains and cassettes are compatible. Some say SRAM is more sturdy, others prefer Shimano, I stay out of debates of almost religious quality...
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