Bottom Bracket HELP 2010 Giant Defy 4

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craigbillers

Member
Location
Belfast
Hi Guys,

Im at my witts end. ive spent about 2 hours tonight trying to sort out my 2010 Giant Defy 4. i bought the bike second hand. All seemed great but im missing the low gear on the cassette when im in high gear on the front. You get the idea.

So ive come to the conclusion that someone has ordered a new bottom bracket for the bike and fitted the wrong size making the crank sit a few mm out to far which is pushing the chain down. The more ive thought about it im convinced its correct.

Now the problem is i cant seem to find what Bottom Bracket i should have so i can get a replacment.

My bike is the triple
 

accountantpete

Brexiteer
Do you mean big ring front and biggest sprocket at the back so that the chain is running diagonally?

If so - you don't use that combination because of chain/sprocket wear.
 
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craigbillers

Member
Location
Belfast
Yes, i the two biggest, i understand that but i cant even if i wanted.

Perhaps a better way of explaining is, there is chain rub on the front derailleur if i shift from high to lowest on the rear no matter what way i have the front adjusted.
 

accountantpete

Brexiteer
Ah! - you need to trim with the left shifter.

You will find that for each ring there is a main click and then a lesser click - this is for trimming the front mech ie moving it slightly so that the chain doesn't catch.
 
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craigbillers

Member
Location
Belfast
I dont understand how adjusting the shifter is going to make a difference.

E.g. WIth the chain on the two biggest coggs the with no derailleur in use the chain will naturally drop of the big ring its really as if the crank isnt in far enough. Does that not make sense
 

Davestokesfoh1

Active Member
Location
Burton
Yes mate-they sent me one that was too small at first-113mm I think-the 118mm is the right one
 

Davestokesfoh1

Active Member
Location
Burton
Ha ha! Maybe thats why I can't shift to the small chainring sometimes-you're probably right about the 116mm-been a while since I changed it so I can't remember where I got the info from
Good luck!
 

RecordAceFromNew

Swinging Member
Location
West London
Thanks as there is a 115mm one also. I think someone told me the old one is actually 116m

For Shimano JIS BB the 115mm has the same chainline as the 113mm. If the 113mm is too short, so would the 115mm be. The 116mm and 118mm are 1mm and 2mm longer on the drive side respectively.

If you are not sure what spindle length you need the best way is to find out what length the existing (assuming it is JIS) is (all square tapered FSA Tempo chainsets, which the Giant Defy spec says it has, should be JIS), measure what chainline it delivers, and work out what you need from that.
 
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craigbillers

Member
Location
Belfast
Ha ha! Maybe thats why I can't shift to the small chainring sometimes-you're probably right about the 116mm-been a while since I changed it so I can't remember where I got the info from
Good luck!
If your bracket was too long then surely it wouldnt effect your small chain ring and only the big one. Anyone im gonna get the 118 and offer it up to the old bracket hopefully thats right
 
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