What can i upgrade ? (carrera owners)


New Member
Hi all

I bought a carrera vengeance from halfords at the beginning of the year,i knew it was a entry level bike but im only using it for towpath rides to get fit so figured it would be fine,however as time goes by i seem to be having one issue after another so thought i may start replacing some parts but better ones.

this started a couple of weeks ago when i damaged the front mech in a wipeout (wet cobbles hurt btw) :sad:
halfords said they couldnt even look at the bike for a fortnight so i took it to a LBS instead and they simply replaced the mech with a new better one the same day and its been fine since.

so now im looking at possibly ordering some new parts and having a go at installing them myself or if installing becomes difficult then getting the LBS to do it.

First things im looking at is a new rear mech and a new chainset/crankset,however knowing little about such parts i need to make sure i order compatible replacements,for the rear mech ive been looking at a shimano deore.


I reckon i can remove my chain,remove old mech and fit this one then set it up,but ive read that different mechs have short,medium and long cages and i have no idea what type the sram x4 is on my bike will it make alot of difference ? or am i better making sire i get the exact same size ?

and the front crank set can they be replaced by a novice ? or is this a job for the LBS ? i guess i know the answer to that but if the lbs does everything for me i'll never learn how to do it myself :sad:

how can i find out what exact size my current bottom bracket is so i can source a replacement ?
unless the rear mech is damaged, or not performing in some way, then it will be pointless simply to 'upgrade' it for the sake of it - you will not notice any difference. Same goes for the chainset. If you are determined to spend money on your bike, then go for lighter/better tyres, or wheels and replace other parts as/when they wear out or break.


New Member
Sorry i should have said,there has been issues with the bike.

currently im getting a what id describe as a slight "slipping" forward when im putting power through the peddles it usually happens on the middle cog on the front but i do have a suspision that the chain is catching somewhere on the rear mech although im not 100% sure , theres a few very worn teeth on the front chainset (non broken as yet) thats why im thinking of changing that and quite often the chain seems to get caught in the frame as i change from small cog on the front to the bigger cogs

oh and my back brake is rubbish :biggrin:
at the end of the day, it's an 'entry-level' bike and sounds like it needs a proper service. I would probably put the money towards replacing the bike itself, rather than upgrading what you have.


Swinging Member
West London
Your sram x4 rear mech is not interchangeable with any Shimano (including the deore) rear mech. If you wish to use a Shimano rear mech you will need to change the right shifter too.

Imho the Vengeance is fine for keep fit and towpaths if properly maintaned. Ok the forks are not great but then even expensive ones need regular (and sometimes expensive) maintenance.

If you are having shifting (or indeed any similar) problem, you could either give more detailed description here or try to identify and fix it yourself through Park's excellent guides.
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