Drivetrain replacements/upgrades

[l4dva]

Hi need a bit of help with my drivetrain and some possible replacements...

I have a broadmans team carbon with SRAM rival group set, its done about 1200 miles and the chain length for 12 links has gone over 12 inchs, it hasnt started skipping or anything like that yet so im just woundering if and when I should thinking about replacing the chain/cassette?

I also wanted to go from 12-25 to 11-25 to get a little bit more speed on the flats/downhills, im assuming i can do this without having to alter the length of my chain or make any changes to the deraileur?

The bike came with shimano 105 cassette and chain, i use the bike for commuting and triathalons so would you recomend spending more money and getting the sram 1070 chain/cassette?? or should i stick with the cheeper 105 as I will be putting high mileage on this bike? also from reading around i gather shimano chains have bad reviews and kmc are the way to go... which kmc chain in particular would you suggest? CRC have a massive range of kmc chains ranging from apx £8 to £55

I am also 'thinking' of upgrading the cranks to sram force cranks... would BB30 fit on this frame? is it worth spending the extra £40 (plus what ever the bearings cost) for this or should I stick with GXP? Would I be better off upgrading the wheels and leaving the cranks?

Thanks!

 

[RecordAceFromNew]

If you have never read it I would recommend the late great Sheldon's article on chain and sprocket wear assessment.

You should be able to change cassette size as you suggested without needing a shorter chain (since it is the size of the large sprocket that affects the chain length). If you have a 50x34T chainset, then a new cassette of 11-25T would require a rear mech with a capacity of (50-34+25-11)=30T, which even the short cage Rival rear mech provides - so no need to change the rear mech either.

Assuming you are running 10 speed, for KMC chains then only their X10 variants are suitable - I know there are still 5 or 6 to choose from but as always only you can decide whether bling is of interest, or whether you wish to have the lightest components (by sacrificing durability usually).


IMHO neither chain nor cassette nor crankset "upgrades" as you are considering will have meaningful influence on speed or acceleration as long as the current components are well maintained, work as intended, and meet your needs. I am not sure how light your wheels are but it might be worth measuring them (without skewers, tyres, rim tapes or tubes, although in practice it is the rim weight that matters far more than the hub weight) and comparing them with other wheels in the market, and of course to measure how heavy the tyres and tubes are. For example if the tyres are Conti Ultra Sport but if they are the wire bead variant then they will offer an opportunity for improvement.

Hope it helps!

 

[accountantpete]

The thing is that the more you spend the lighter and more polished the components are - except that the drivetrain components are at the centre of the revolving bits and consequently weight saving in this area won't have as great an effect as savings in the wheel rim/tyre/pedal/footwear dept.

 

[l4dva]

Thanks for that link, that helps clear things up, ill check the exact lenght of the chain/wear tomorrow morning.

Going by what you guys say I think I'd be better off spending the money else where than on upgrading parts of the drivetrain.. i guess it isn't broke so I shouldn't trying fixing it. And seen as this is a high mileage bike I might just stick with the 105 cassette as it rides nice and smoothly as it is, and the extra expense probably isnt worht it.

I dont have a decent set of scales to check the weight of my wheels, but i reckon ill feel most improvement upgrading these. I've already changed the tyres for michelin krylions, which have made a good improvement already. Now to choose weather to go for some cheep(ish) aeros like the planet x's for triathlons and keep current for commutes or get a lighter racey set of wheels that will handle the commutes/potholes and the races...

Thanks for your help guys!