# Bottom bracket replacement noob



## Macd Ryabko (28 Nov 2013)

Hi,

I have a carrera crossfire 1 with damaged bottom brackets (keeps skipping on pedal pressure). I want to change the bottom brackets myself. I'm not too sure how to proceed. 
I am assuming the bike has square taper bottom bracket. Can you give me a little information on tools I need and maybe replacement bottom bracket options I can buy. 
I have bought a crank puller/bottom bracket remover (http://www.ebay.co.uk/itm/ROAD-MOUNTAIN-BIKE-BICYCLE-Cycling-MTB-CRANK-PULLER-REMOVER-EXTRACTOR-TOOL-SET-/400577762535?pt=UK_SportsLeisure_Cycling_BikeLocks_SR&hash=item5d444b94e7)

Thank you


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## raindog (28 Nov 2013)

Macd Ryabko said:


> I have a carrera crossfire 1 with damaged bottom brackets (keeps skipping on pedal pressure).


Depends what you mean by "skipping", but that sounds more like a chain/cassette/derailleur problem.


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## compo (28 Nov 2013)

As Raindog says skipping and slipping doesn't sound like bottom bracket. How old is the bike and what sort of mileage have you on the chain and cassette. If not too old I would fit a new chain and see how it goes, although it may well be you will need to replace the cassette as well.


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## Paulus (29 Nov 2013)

Agree with the above, it will be either the chain skipping over the rear cassette, which will be a simple cable adjustment or indexing adjustment, or, the chain skipping over the chainrings. it could also be that the chain/chainrings/cassette are worn and one or the other need replacing. When the bottom bracket is buggered the cranks will be moving around and will sound like there is gravel in the BB.


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## evo456 (1 Dec 2013)

Couple of things to check, before replacing your bb. I did it recently on my crossfire.


Check chain for kinks and stiff links
Check rear cassette if the tooths have gone pointy and sharp.
Do the same with front chain ring, mine was very worn on the most used ring.
Gears index properly- smooth changes. If not cable tension needs adjusting.
I took the opportunity to do an over haul, as all my components are well worn after 2000 miles of mud and grit. Rear cassette, crank set, chain and new bb, 50 squids all in.


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## DragonNate (16 Aug 2014)

evo456 said:


> Couple of things to check, before replacing your bb. I did it recently on my crossfire.
> 
> 
> Check chain for kinks and stiff links
> ...


Could I ask where you got the parts from and part descriptions. As my front gears are bent which has also bent my chain, and halfords are not the brightest employs and have not been very helpful at all. Thank you for your time.


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## Ticktockmy (17 Aug 2014)

To bend a cycle chain, your front gear set must be very badly bent as even when new chain have quite a bit of sidewards flexibility. I can understand now why your chain is jumping off. you must have done something really excessive to bend the front gears. I am minded have you checked to see if the chain set locking screws are still screwed up tight, as if then have slackened off the gears could well be out of line..


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## smokeysmoo (17 Aug 2014)

Is it coincidence that your post is identical to THIS one on Bike Radar from November 2013?

Or is it a straight case of plagiarism? 

As for tools and how to do to there are loads of videos on YouTube, this was just the first one that came up.



I have to agree with the other posters though, and also with the first reply on Bike Radar, and that is to say BB's don't skip.


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## DragonNate (17 Aug 2014)

Ticktockmy said:


> To bend a cycle chain, your front gear set must be very badly bent as even when new chain have quite a bit of sidewards flexibility. I can understand now why your chain is jumping off. you must have done something really excessive to bend the front gears. I am minded have you checked to see if the chain set locking screws are still screwed up tight, as if then have slackened off the gears could well be out of line..


I bought the bike on Friday and only noticed when I went for a good ride. The rings look bowed and causing the chain to snake around. Have made a few adjustments and is a little better but would like to replace the ring set but unsure what I need. I know it's 170 mm and the teeth are 48/38/28. Could I replace with any set? Cheers


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## evo456 (17 Aug 2014)

DragonNate said:


> Could I ask where you got the parts from and part descriptions. As my front gears are bent which has also bent my chain, and halfords are not the brightest employs and have not been very helpful at all. Thank you for your time.



All sorts- from Amazon and Rose Bikes, whatever worked out cheaper and easier to get hold of. The crankset from Rose was a stroke of good timing.... £13 , shop about if you're not interested in the high level group sets- Tourney/Altus/Alivio. Here's a shopping list:

http://www.amazon.co.uk/Shimano-Tou...=1408294198&sr=1-5&keywords=chainset+48-38-28
http://www.amazon.co.uk/KMC-Speed-C...=1408294365&sr=1-2&keywords=kmc+7+speed+chain
http://www.amazon.co.uk/Shimano-Tou...F8&qid=undefined&sr=1-3&keywords=shimano+tz21
http://www.amazon.co.uk/Shimano-BBU...408294517&sr=1-1&keywords=un55+bottom+bracket


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## smokeysmoo (17 Aug 2014)

DragonNate said:


> The rings look bowed


You can replace just the chainrings rather than the entire chainset. Pics would help though.



DragonNate said:


> Could I replace with any set? Cheers


In a word, no. It has to match you bottom bracket, and there are several types of BB. Again pics would help.


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## DragonNate (17 Aug 2014)

evo456 said:


> All sorts- from Amazon and Rose Bikes, whatever worked out cheaper and easier to get hold of. The crankset from Rose was a stroke of good timing.... £13 , shop about if you're not interested in the high level group sets- Tourney/Altus/Alivio. Here's a shopping list:
> 
> http://www.amazon.co.uk/Shimano-Tourney-FCM171-Chainguard-Crankset/dp/B00A7B5624/ref=sr_1_5?s=sports&ie=UTF8&qid=1408294198&sr=1-5&keywords=chainset 48-38-28
> http://www.amazon.co.uk/KMC-Speed-Chain-Link-Silver/dp/B0013NPYTU/ref=sr_1_2?s=sports&ie=UTF8&qid=1408294365&sr=1-2&keywords=kmc 7 speed chain
> ...


Thanks for that, much appreciated. Try and get the bike back to how it should be.


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## winjim (17 Aug 2014)

smokeysmoo said:


> Is it coincidence that your post is identical to THIS one on Bike Radar from November 2013?


Check the date of the OP


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## smokeysmoo (17 Aug 2014)

winjim said:


> Check the date of the OP


That'll be November 2013.....................................exactly as I stated in the post you've quoted


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## ChrisTh (18 Aug 2014)

Not first post from link you put, first post from this forum.


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## DragonNate (19 Aug 2014)

evo456 said:


> All sorts- from Amazon and Rose Bikes, whatever worked out cheaper and easier to get hold of. The crankset from Rose was a stroke of good timing.... £13 , shop about if you're not interested in the high level group sets- Tourney/Altus/Alivio. Here's a shopping list:
> 
> http://www.amazon.co.uk/Shimano-Tourney-FCM171-Chainguard-Crankset/dp/B00A7B5624/ref=sr_1_5?s=sports&ie=UTF8&qid=1408294198&sr=1-5&keywords=chainset 48-38-28
> http://www.amazon.co.uk/KMC-Speed-Chain-Link-Silver/dp/B0013NPYTU/ref=sr_1_2?s=sports&ie=UTF8&qid=1408294365&sr=1-2&keywords=kmc 7 speed chain
> ...


What size is the bottom bracket for the crossfire 1. Cheers


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## evo456 (19 Aug 2014)

DragonNate said:


> What size is the bottom bracket for the crossfire 1. Cheers



122mm


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## DragonNate (19 Aug 2014)

evo456 said:


> 122mm


Thanks, I've looked on amazon and the options are 68 x 122.5mm is this right or did they miss the point out of it (6.8 x 122.5mm) the others are 6.8 x 12.7 cm/11.8 cm. I appreciate your time.


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## smokeysmoo (19 Aug 2014)

DragonNate said:


> Thanks, I've looked on amazon and the options are 68 x 122.5mm is this right or did they miss the point out of it (6.8 x 122.5mm) the others are 6.8 x 12.7 cm/11.8 cm. I appreciate your time.


If it is 122mm wide then just get the 68 x 122.5mm English thread UN55, currently £9.99 at CRC 

I say UN55 and not UN54 because the 55 has a metal adjustable cup whereas the 54 only has a plastic one


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## evo456 (21 Aug 2014)

smokeysmoo said:


> If it is 122mm wide then just get the 68 x 122.5mm English thread UN55, currently £9.99 at CRC
> 
> I say UN55 and not UN54 because the 55 has a metal adjustable cup whereas the 54 only has a plastic one



What he said


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