changing chainring and cassette help please

ianbar

i am looking to change my chainring and cassette and pop the old one on my winter bike build. currently i am running fsa 50/34 chainring and a tiagra 10sp cassette 12-28. i have been looking and see you can get a chainring 53/39 i assume this would make it easier on the climbs? this is an ultegra chainring. i guess what i want is a little help on the climbs(not built for it) and while i am improving a little tech help wouldn't go amiss! oh btw the ultegra cassette is 11-28 so i guess the chainring size evens?

Wirral_paul

A 53/39 will make it harder, not easier on the climbs. To make it easier, you want a lower gear which means either a smaller chain ring on the front, or a larger one on the back.

If you cant get up hills with a 34/28 lowest gear then you need either a triple chainset, or a larger rear cog for your cassette. You'll therefore need to consider running a medium / long cage rear mech and then a 12-32 cassette if you go for the cheaper overall option of sticking with a double front and changing the cassette.

freezing77

What you propose will make it MORE difficult on climbs and not easier.

sungod

fitting a crankset with, say, 46/30 (or even lower) might be an option, what's possible depends on the bike (and budget)

ianbar

im not totally useless on the climbs, i can get up well actually got up everyone i have tried. i am just looking for a little help(marginal gains someone described it to me). i did realise after i put it that i got the chainring sizes the wrong way round. so would need smaller rather than bigger. i certainly don't want to go down the triple route.

andrewjoseph

I think 34 may be the smallest you can go on the front, so you need bigger on the back. medium cage ultegra didn't fit on a 36t but works fine on a 32t cassette. i think small cage will only go to 28?

i have a triple and use it for day rides and touring, hardly ever use granny for day rides (but it's really nice when I need it!), but use it a lot for touring.

edit, little bit of searching and you can get a 33t 110bcd chainring from TA.

to go smaller may need a new crankset, and then the front mech may not work well.

ianbar

oh dear this is sounding complicated now lol

ianbar

will as sram cassette work with shimano? or would i have to go sram on everything? seen a sram cassette 12-36?

freezing77

A SRAM cassette will fit your wheel but you will definately need a new rear derailleur and possibly new chain

ianbar

oh ok thats not too bad, but wouldn't need to change the shifters too since changing deraillieur?

freezing77

Short answer NO.
SRAM and Shimano road cassettes have the same spacing, is it the PG1050 you are looking at?.
Derailleurs are "dumb", they move how much the shifter tells them to.

http://www.sheldonbrown.com/k7.html

Cassette info from the incomparable Sheldon Brown

ianbar

Yeah that's the one. Looks like a SRAM cassette and derailleur could be on the shopping list next!

andrewjoseph

The short answer above may not be correct though. this does get complicated now. From what i can gather, sram mtb X series rear mechs have never been compatible with shimano road shifters, but shimano mtb mechs were.

Apparently shimano has changed the lever pull for some of its shifters. it used to be the case that all shimano shifters pulled the same amount, but no longer.

some shimano shifters are compatible with some shimano rear mechs road or mtb, but some are not. you need to do a lot of research.

sram cassettes and chains are fine, some x series rear mechs are not, 'named' (i.e. 'rocket') maybe, depends on your shifters.

i love sram mtb shifters, but I think you should stick to shimano for this or go to sram apex shifters and mechs.

Ultegra medium cage rear mech will go up to 32t and works fine with ultegra 6703 shifters. i have this on my bike.

cyco2

Have a look at this it's fascinating. :?
http://sheldonbrown.com/k7.html

ianbar

while working last night i did think to myself mixing it up was making it way to hard for myself, and did think i could aim for an ultegra set up.i have to ask though when you say medium cage what do you mean? when i have looked i havnt found a cassette that goes to 32t not that i don't believe you just i can't find them!

i look at that sheldon bloke(gets a lot of promotion here) but my little brain only takes in a little at a time lol

andrewjoseph

keeping with the same brand will help to reduce mistakes and headaches from banging your head against the wall.

the rear mech comes in three different sizes, short, medium and long. However: not all models come in he three sizes. i think ultegra only come sin short and medium, at least, i couldn't find a long cage.

the different sizes are actually about the measurement between the jockey wheels. short cage for close ratio cassettes like 11-23, medium cage for 11-27, long cage for 11-36 (or something similar, it depend on the make, model and discipline) most short to medium cages are for the road, medium to long is usually for mtb, but people mix it up depending on preference. it also depends on chain length and and how many chainrings up front, single, double, triple, and the sizes of the largest and smallest chainrings and the difference between them (tooth count).

the job of the rear mech is to shift gear AND to take up the slack when moving between different size cogs, front and back, to keep the chain tension constant.

to use large cassette cogs (to get up hills easier) you usually need a long cage that will allow the use of up top 36t biggest cog (lowest gear) and an 11 or 12t smallest cog (highest gear) AND the differences of the chain rings up front.

front mechs come in two types, double and triple. the same with the shifters and they have to match the mechs. The mechs have to match the profile of the chain rings and the 'throw' to move them up and down. get the wrong front mech and it will catch on the teeth as you try to move it.

there is also top and bottom pull and some that go both ways. you have to match the band clamp diameter to the seat tube diameter (or use shims), or use a bolt to braze on type, depending on your frame.

and then you have to chose what colour you want.

It's not easy to take it all in, and i might not be entirely correct in what I'm saying, but it's not rocket science and you will get there soon.

ianbar

thank you for that, it has taught me a thing or two! it is hard to figure everything out when new to this but thats part of the point! :-)

ianbar

if i get the tiagra cassette 12-30 will that require any special fixing from my 12-28 i have now?

andrewjoseph

'might' work. probably need to adjust the 'b' screw.