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Upgrading BB and cranks set compatibility?
#1
Aloha,

I've got a 2005 Felt F80. The triple chain ring is showing a fair amount of wear and I was thinking about upgrading.
It currently has a FSA RPM triple chain ring, 52-42-30
[attachment=2531]

The bottom bracket says
Power Pro Components
BB-7420
BC1.37x24T
68
[attachment=2532]

I think it's 115mm from spindle end to end.
It's tapered square spindles.

The bike is 9 speed.

It's more or less a commuter and training bike so I'm not looking for amazing performance.

What are my options for a new bottom bracket and crank/chainring?
If I do a tiagra crank/chainring would I get a different type of bottom bracket?

I was thinking of getting this:
http://amzn.com/B001GSQNL0
It's a tiagra crank but the gear numbers are different, it's 50 39 30.
and this different BB
http://amzn.com/B001QW3GZM

Would that work? Would I have to adjust chain length?

Mahalo,

Jeff
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#2
These BB are more like your current one. As per crank it still looks usable to me. If you change it than the chain will wear it quicker. If you change the chain than the rear cluster should be changed too and so on. Is something wrong with your current BB?

http://www.amazon.com/Shimano-BB-UN54-Bottom-Bracket-122mm/dp/B0011ZCEHK/
Never Give Up!!!
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#3
The BB is more or less okay. It's a little rough feeling and probably 6 years old.

For $15 I don't mind paying for a new one but then it lead down the path of looking for new front chainrings and trying to find what would be compatible.

I'm putting on a new chain. Will probably get a new cassette too.

(06-15-2011, 04:50 PM)GeorgeET Wrote:  These BB are more like your current one. As per crank it still looks usable to me. If you change it than the chain will wear it quicker. If you change the chain than the rear cluster should be changed too and so on. Is something wrong with your current BB?

http://www.amazon.com/Shimano-BB-UN54-Bottom-Bracket-122mm/dp/B0011ZCEHK/
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#4
Ye since its in pieces putting in a new BB is a good thing after six years.

You can just replace worn parts and it may take years for worn parts to wear new parts. However by the book its best to replace all together .
Never Give Up!!!
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#5
You should replace BB and crankset at the same time because sometimes the BB length is determined by the crank. You should replace chain and cassette at the same time because they wear into each other - can be bad to mix used and new. Replacing the 'front' (BB & crank) at the same time as the 'back' (chain cassette) is maybe recommended, but not critical.
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#6
Just as a follow up. I was able to get the new tiagra cranks and bb on.
I also put on a new chain, cables, and rear cassette.

From Bike Repair

I've given up on trying to get the deraillers adjusted and taking it to LBS tomorrow. Got a lot of fun new tools now.
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#7
Nicely done Jeff.
I presume the new crank is completely different to your old one.
ie external bearings and a two piece crankset.
I like the new design of these cranks but there are concerns about how long the bearings last.
Make sure you don't power-wash around the bearing area. Smile
[font=Trebuchet MS]Ride hard or ride home alone![/font]
Reply
#8
Yup, it has the external bearing BB.
Reply


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