My drivetrain is due for replacement and I was considering changing from a compact (50/34) chainset to a standard 53/39 set-up.
I am currently running a 11-23 cassette on the rear, which is fine with the compact c/s, but would I be better off fitting a 12-25 (or similar)?
I live in an area that is very hilly, although none of the hills are particularly big - we are talking West Sussex here, not the alps.
Is there any benefit in changing to a 53/39 c/s? I do like the idea of the smaller jump between the two chain rings.
And finally: Is it worth spending the extra and going for an Ultegra chainset, rather than 105? If it helps, I don't race.
What are you trying to achieve?
To keep the low gear you'd have to get a 25, you'll prob use the front mech less.
You won't notice any difference riding ultegra, over Tiagra even.
Apart from the smoother transition between chainrings, I could do with strengthening my legs. I do also find that I spin out on the compact on occasion.
Why? The same low gear won't do anything for leg strength!
I agree re. jump between rings, I can't even deal with 39-53!
If you're happy with your current gearing then dont change but if you decide to go to 53/39 then you are best to change the block at the back to a 12-25, yes. Ultegra is a bit lighter and stiffer than a 105, better idea to have a trawl around the online stores for a deal on a carbon set, possibly something like an FSA/SRAM or similar.
You are spinning out on 50/11? and want to go to 53/12 instead. Well I thought that 50/11 was slightly higher in gearing terms. Perhaps you should be looking even bigger at the front or keep the 11-23 at the back.
If you are regularly spinning out on a gear like that, have you considered racing?
50/11 is a bigger gear than 53/12? I wouldn't have thought that, but then again I've never really looked into the technical side of it, just what feels good.
I suppose I could just keep the 50 outer and change the inner to a 38, using a 11-25/28 cassette.
Spinning out?
50/11 and 53/12 are both going to be around 35mph @ 100rpm and 45mph @ 130rpm
When I meant spinning out, I meant primarily on downhills.
Don't worry about that!
I'm in the middle of knee rehab after an ACL recon in june. Surgeon is dead keen on cycling for rehab so I started off using my old Rockhopper on a turbo then out on the road. I was interested to try and find out what gears on the MTB would be equivalent to my compact road bike so i made up a very basic spreadsheet to look at gear ratios and how that translated into road metres for each crank turn.
You can have a look at it [url= https://dl.dropbox.com/u/38554627/Bike%20Gears.xlsx ]here.[/url]
Should be self explanatory. Replace the red numbers for your own front and rear set ups and wheel size, then read across to the tables on the right for ratios, gear inches, and road metres. It's interesting to see where up the cassette the crossovers occur.
It's only my second ever go at a spreadsheet so no laughing, and no doubt there are slicker versions around.
ps, first go at using dropbox too so hope it works.
50/11 is a bigger gear than 53/12? I wouldn't have thought that, but then again I've never really looked into the technical side of it, just what feels good.
The [i]"technical"[/i] side of it? What would that be then?
You're over thinking it way too much... It's simple division, the kind most 8 year olds wouldn't even struggle with. You take the big number and divide it by the little number to give you your gear ratio, 50/11 being 4.55:1 and 53/12 being 4.42:1.
Simple!
As for gear ratio choice. If you don't struggle currently with your 34/23 bottom gear, then you could probably change for a 36 or 38 inner chainring and go to an 11-25 or 11-26 cassette to give you a similar bottom gear with less gap in the rings. I'll agree the jump from 34-50 is huge and can be an annoyance, but then I like having the lower gears the ratios afford too. Does make me think though that for most people, not racing, a triple makes more sense ironically as you'd spend most of your time on the 39 and only use the 30T for going up steep hills, and the 52 for going down them.
