12-25 11-25 :-s

[Jdratcliffe]

i have a stock 12- 25 on my commute which has no done 5000miles ( with the original chain too not passed .75% stretch) looking at replacements thinking will i notice the speed difference or worth just sticking with the same? if i do change it would i need to make any adjustments as it so similair?

ideas if its worth changing it in a more extreme way? i probably only use my smaller chain ring 5% of my commute ( its a 50 x 34) so thinking bike is a bit under geared... ideas welcome.

 

[User482]

Unless you're regularly spinning out top gear, you won't gain anything, and will have a bigger jump between ratios. I have a 50/ 12 top gear on my bike, and can pedal at 30mph quite comfortably. I'm tempted to switch to a 48T chainring and 11-25 cassette, which would reduce the jump between chainrings. 48/ 11 is bigger than 52/ 12.

 

[compo]

Unless you're regularly spinning out top gear, you won't gain anything, and will have a bigger jump between ratios. I have a 50/ 12 top gear on my bike, and can pedal at 30mph quite comfortably. I'm tempted to switch to a 48T chainring and 11-25 cassette, which would reduce the jump between chainrings. 48/ 11 is bigger than 52/ 12.

30mph COMFORTABLY!!
What the hell do you do uncomfortably?

Respect!

 

[User482]

30mph COMFORTABLY!!
What the hell do you do uncomfortably?

Respect!

I meant going downhill - I'm not Mark Cavendish!

 

[PpPete]

50 /12 (with 700x23mm tyres) 100 rpm will give you 32.6 mph 50/11 will up that 35.6 mph
50 /12 (with 700x23mm tyres) 135 rpm will give you 44 mph 50/11 will up that 48 mph

If you are regularly exceeding those kind of rpms /speeds then worth changing - if not, work on your leg speed.

_______
EDIT - x-posted with User482' 1st reply

 

[Jdratcliffe]

50 /12 (with 700x23mm tyres) 100 rpm will give you 32.6 mph 50/11 will up that 35.6 mph
50 /12 (with 700x23mm tyres) 135 rpm will give you 44 mph 50/11 will up that 48 mph

If you are regularly exceeding those kind of rpms /speeds then worth changing - if not, work on your leg speed.

mmm fair enough i not getting near that so looking at leg speed any tips?

 

[MontyVeda]

mmm fair enough i not getting near that so looking at leg speed any tips?

pedal faster

 

[HLaB]

I changed from an 12-25 to an 11-25 that lower cog just gives me that little bit extra down hill or in a strong tailwind. I've subsequently fitted a SRAM 11-26 to get that little bit extra going up them too

 

[PpPete]

mmm fair enough i not getting near that so looking at leg speed any tips?

Spinning classes at the local gym ?
First time I went I could barely get above 120 rpm. After a few months I could hold 140 rpm for several minutes, and can now hit 165 for short periods. On the road this means I can just about get up to 30 mph downhill on the fixed (about 135 rpm).

 

[amaferanga]

I just changed from a 12-23 to an 11-25 and I really notice a couple of the jumps between gears now. Wish I'd gone for a 12-25 or stuck with a 12-23 now.

 

[old bell]

I made the change from 25/12 to 25/11 on my Chorus 11 bike last summer and felt it gave me an extra gear for going faster. I am now going to make the same change on my other bike.

Don't think about it any further, just go for it.

 

[amaferanga]

I made the change from 25/12 to 25/11 on my Chorus 11 bike last summer and felt it gave me an extra gear for going faster. I am now going to make the same change on my other bike.

Don't think about it any further, just go for it.

I bet it doesn't actually make you faster though given that you should never (or at least hardly ever) be spinning out with the 12 anyway.

 

[HLaB]

I bet it doesn't actually make you faster though given that you should never (or at least hardly ever) be spinning out with the 12 anyway.

Its made me faster on downhills, I didn't often brake the 40mph barrier before, pedalling downhill at 119rpm (52-12) or spinning out and not being able to feel resistance doesn't inspire me with confidence. I can hit 40+mph more often, 52-11, it needs just 109rpm and I don't spin out much and feel the bike responds quicker to me. In sprints (with a tailwind) its also useful to have that extra gear.

 

[e-rider]

Unless you're regularly spinning out top gear, you won't gain anything, and will have a bigger jump between ratios. I have a 50/ 12 top gear on my bike, and can pedal at 30mph quite comfortably. I'm tempted to switch to a 48T chainring and 11-25 cassette, which would reduce the jump between chainrings. 48/ 11 is bigger than 52/ 12.

are you sure? Aren't they just about the same, or even 52/12 is slightly bigger than 48/11?

 

[HLaB]

are you sure? Aren't they just about the same, or even 52/12 is slightly bigger than 48/11?

According to the Machinehead Gear Calculator the 48/11 is slightly bigger (114.63inch) than the 52/12 (113.84); whether or not you actually notice that extra 0.79 inch (0.28mph @ 120rpm) is another question