Cassette info for a novice bike build..

johnscleary

Im fitting a 50-34 compact to my frame as Im starting a bike build soon.
Im wondering if I can get sound advice on the gear spread for the cassette, as the terrain around here is fairly hilly, though on the flat and descents I like to push on a bit.
Basically I dont want to be clunking around the gears, and on my old standard 9 speed 53-39 I didnt have huge problems with hills.
Just my knees are shagged and I reckon a compact would make things that bit easier.
I presume a standard short cage rear mech(was thinking Ultegra)will be compatible with the crankset?
Any other tips or advice well appreciated.
Cheers
John Cleary

robbarker

Ultegra short cage mech spec says max front difference 14 teeth, so 50/36 would be OK, 50/43 is not within the spec. You're suppose to get a GS cage version.. 105 and Dura-Ace short cage rear mechs spec at max 16t difference. All on the Shimano website.

From what you say I'd suggest 53/39 and 12/27 would be a better bet - nicer to live with IMHO as you're not constantly swapping rings at the front, as I found I was with a compact (I've now gone back to... 53/39 and 12-27!)

Smokin Joe

Compacts are only hard to live with if you go with the standard 50/34 configuration. I use 50/36 and 48/34, both with 13-26 cassettes and there is no more ring swapping than with a 53/39.

Ideally, 48/34 and 12-27 would suit most people who are not racing. Your top gear is exactly the same as the one Merckx won five TdF on and the bottom is low enough to get you over anything.

deal

there is a useful gear calculator available on Sheldon Brown http://www.sheldonbrown.com/gears/ which will allow you to compare different combinations of chain rings and cassettes

for example, assuming 700x23mm tires you will achieve the following range of speeds (mph) in the lowest/highest gears at 90 rpm (assuming a 12-25 cassette with the compact and 12-27 with the double)

Compact with 12-25     Double with 12-27
(39)    (53)			(34)    (50)
22.9	31.1			19.9	29.3
21.1	28.7			18.4	27.1
19.6	26.6			17.1	25.1
18.3	24.9			15.9	23.5
17.2	23.3			15.0	22.0
16.1	21.9			14.1	20.7
14.4	19.6			12.6	18.5
13.1	17.8			11.4	16.8
11.4	15.5			10.4	15.3
10.2	13.8			9.6	14.1

redddraggon

robbarker wrote:

From what you say I'd suggest 53/39 and 12/27 would be a better bet - nicer to live with IMHO as you're not constantly swapping rings at the front, as I found I was with a compact (I've now gone back to... 53/39 and 12-27!)

I'm not too sure about the whole swapping back and forth between the rings, I spend most of my time in the 50t on the compact, but use both the 53 and 39 on the double.

johnscleary

thanks to all who replied, Im veering towards going back to the traditional 53 39 now, based on what Im reading generally..

SDP

i am running 50/38 with 12-25 ...

if i put a 27 on i reckon you could get up most things
i run this with a short cage DA10 mech ...sweet as a nut shifting ...


i decided to try a 50/34 with 12-25 for my winter bike & TBH the 34 doesnt do it for me ...

i need to get a 36 on it PDQ ..

gtr mart

I just changed from a 12/25 ultegra cassette to a 12 x 27 105 rear cassette on a 53/39 double and whilst I havent given it a proper test it certainly feels like you could spin up steeper hills a bit easier.

You mentioned about going for an ultegra rear cassetee - I was advised the difference between the ultegra and the 105 was minimal (same cage) - is this right?

Do the specs of cassettes really matter?

johnscleary

Hi GTR,
I already have an Ultegra cassette in 12 27 so Im going to stick that on, but Im sure there must be very little difference in quality between the two, same goes for an Ultegra rear mech, which I also have here.
Except the difference in price, of course.
At least, thats what I think on the matter, any better tech advice out there on this?

aracer

I'd ignore the compact naysayers - I've not found the jump between rings to be such an issue as they're suggesting, and I have the 50-34 thwey seem to dislike. If you get a wideish range cassette then it's even less of an issue as you need to change rings less often. If you want to make it really easy on the hills then a 12-27 to go with that - only you know if a smaller cog on the top is enough to get up your hills without struggling.

BTW - the short cage rear mech should be fine, whatever Shimano specs say (they are usually pretty conservative). Specialized spec a short cage on the Roubaix with a 50-34 and 12-27, and you don't get complaints about that not working.

deal

the price difference between ultegra and 105 cassette is also minimal isnt it ? 3-4 quid at most which suggests there is very little if any difference. The only difference that would bother me is the range of sizes available, there is a 11-25 cassette available in 105, this isn't available in Ultegra.

John.T

aracer is spot on. 50/34 and 12/27 works fine with a short cage mech. 50/19 and 34/13 both give about a 70" gear which is the one I ride in most of the time. It is good for up to 20 mph without spinning your legs off. I just use the one that best suits the terrain I am on. The chain lines balance out compared with 53/39, some better, some worse. I consider that the 12/25 cassette is a bit of a waste as the 21, 23, 25 cogs give too close ratios for hilly country, the slightly wider 21, 24, 27 is better. I just change to a 12/23 for racing which is good for 30+ mph which is all I can manage nowadays.
There is far to much mistique made out about compacts. It is only gear ratios. Can I get up this hill on this gear? It does not matter how you get that gear. If you manage fine on 39/27 then stick with it, if not a 34 is the easiest way of getting lower. With a compact and 12/27 you will spread your gear range by one ratio lower and have one less duplicated gear.

johnscleary

again, thanks for all the posts on this issue, Im getting excellent feedback on every post I place, makes it easier to make decisions, naturally.