Help I need smaller gears - what can I do? A GUIDE

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redddraggon
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Help I need smaller gears - what can I do? A GUIDE

Postby redddraggon » Wed Aug 27, 2008 22:48 pm

Generally bigger sprockets and smaller chainrings equals smaller gears.

Getting bigger sprockets is normally done by fitting a wider ranging cassette, 12-27 (shimano), 11-28 (SRAM), and 13-29 (Campag) are commonly available. If these are still too small a MTB cassette can be used (assuming you have 8-spd or 9-spd) which come in the ratios 11-32 or 11-34 - these normally require an MTB rear derailler to work suitably. MTB cassettes can also come in 11-30 and these may or may not work with road deraillers Changing the cassette is normally the cheapest option.

Assuming a standard double (53/39 etc) smaller chainrings can be achieved by fitting a compact (50/34, 50/36. 48/34), normally the current front mech will be fine for a compact along with the shifters.

To get even smaller chainrings at the front a triple can be fitted, these come in ratios similar to 50/40/30, 53/39/30 and 52/42/30 etc, "touring triples" are also available with slightly smaller chainrings eg 48/38/28.

A double to triple conversion is usually pretty costly, a new front mech, longer caged rear mech, and shifters (if only double compatible - Campagnolo and some shimano shifters are triple and double compatible).

(MTB triples (eg 44/32/22) can be fitted to road bikes, but road specific front mechs tend not to be able to cope with the very small chainrings)
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gematkinson1
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Postby gematkinson1 » Thu Aug 28, 2008 13:32 pm

very useful... thanks!

fizz
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Postby fizz » Thu Aug 28, 2008 15:13 pm

dont forget a Shimano std double will take a 38 T inner ring so thats another option if you dont want to go the whole hog down to a compact.

woody-som
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Postby woody-som » Thu Aug 28, 2008 17:08 pm

or even try the rotor Q ring on the inner of a normal double. will reduce the effective size of the ring on the hardest part of the circle. I ride them, and find I actually use a bigger gear at the back now, since the change from normal chainrings.

loz*
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Postby loz* » Tue Sep 09, 2008 21:59 pm

this is great, i've been wanting to ask questions about this for a while but didn't fancy starting a new thread just for it.

Can someone tell me, if I wanted to change from a double to a triple, would i need a new front derailleur? How would I be able to tell whether the shifters I have could cope with a triple? What is a longer caged rear mech?

thanks in advance!

grayo59
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Postby grayo59 » Thu Sep 11, 2008 20:31 pm

woody-som wrote:or even try the rotor Q ring on the inner of a normal double. will reduce the effective size of the ring on the hardest part of the circle. I ride them, and find I actually use a bigger gear at the back now, since the change from normal chainrings.


Sorry? What does this mean in layman's terms please.

andrew_s
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Postby andrew_s » Sat Sep 13, 2008 21:16 pm

If you want a triple, rather than buy a new chainset, you can replace your inner chainring with a triple converter chainring (plus the 3rd chainring, another set of bolts and some spacers). The new small chainring then bolts to the new middle chainring rather than to the cranks direct.

You may or may not require a longer bottom bracket. It depends on the amount of clearance you have, and whether your front mech will swing in far enough to change onto the small ring without hitting the seat tube. Experimentation is in order.

andrew_s
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Postby andrew_s » Sat Sep 13, 2008 22:42 pm

For loz:

If changing to smaller chainrings, you may possibly require a new front mech for the following reasons.

1) The cage of the front mech is too short, so that when it's as low as it will go whilst clearing the big chainring, when in small/small the chain drags across the bottom end of the cage.
Try fitting a smaller large chainring so you can drop the front mech a little lower on the seat tube, or just avoid using the small half of the cassette with the small chainring. If this doesn't appeal or or doesn't work, then a look at a new mech.

2) The curve of the outer plate of the front mech is sized for a 53 chainring. If the large chainring is too much smaller than this, the bottom end of the cage will be well away from the chainring. The result is that you get poorer shifting between the middle and small chainrings and back up onto the large chainring, especially under power. Generally 48 is OK, smaller is where the problems start.

-------------------------------------
Longer cages on the rear mech.
The cage length is the distance between the upper jockey wheel and the lower one. Many rear mechs are available with different cage lengths (short/medium/long, or just short/long).
If you put the chain tight round small/small, you need less chain than when tight round large/large. The chain has to be long enough to go round large/large, and when you change gear the rear mech puts a zizzag in the chain to use up the spare and keep it tight. The amount of spare chain that you need to be able to wrap up in the zigzag depends on the sum of the differences between small and large chainrings and small and large sprockets. The amount of spare chain that can be used up the the zigzag depends on the cage length, and is expressed as having a capacity of so many teeth in the mech specifications.
So if you have a 52/42 chainset, and 12-23 cassette, your rear mech should have a capacity of 10+11 = 22 teeth or more
If you have a 30/40/50 chainset, and a, 13-29 cassette, your rear mech should have a capacity of 20 + 16 = 36 teeth.

In practice it doesn't matter if you exceed the rear mech capacity by a few teeth. What happens is that the cage comes up past the horizontal so the chain drags noisily across itself at the top jockey, and it's a bit slack so it will come off more easily if you hit a bump.
But you don't use small/small do you?

--------------------------------------------------
Do my shifters cope with triple?
Look up the specs for your shifters on the interweb.
Or you can count clicks and check whether the shifter pulls enough cable. One click is definitely double only, three or more is definitely OK for triple. If it's two, it may be double with trim or triple.
Back off the high and low gear limit screws on the front mech, then with the chain off, hold the mech cage positioned above the granny ring (or where it would be), and with the other hand take a grip on the inner cable where it emerges from the front of a cable stop (where "front" is towards the front of the bike). Then let the mech move to above the large ring whilst pulling on the cable by the stop. The distance the cable moves out from the stop tells you how much cable pull is needed to shift across 3 rings. To find out how much cable the shifter will pull, change to the large chainring end as far as the shifer will go, then grip the cable inner where it emerges from the rear of a cable stop, and keep it tight as you work the shifter as far as it goes towards the small chainring.
Don't expect too much accuracy, but it should tell you if the mech is well short of pulling enough cable.

loz*
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Postby loz* » Sun Sep 14, 2008 08:23 am

wow, lots of info. thanks a lot for your effort!

Leedsblue
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Re: Help I need smaller gears - what can I do? A GUIDE

Postby Leedsblue » Sun Sep 14, 2008 08:43 am

redddraggon wrote:Assuming a standard double (53/39 etc)


What is the default size on a standard road bike (i.e non custom specced). My 42/52 13-23 seems rather restrictive in a hilly area and I seem to see more people having a 39/50 set up.


Secondly, if you have a Campag set up and decide to change the cassette to give a bigger gear is there any reason to stay with Campag or go with say the SRAM which offers a bigger range or whatever cassette is available cheaply at the time

Good thread, thanks for starting

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Postby woody-som » Sun Sep 14, 2008 15:02 pm

grayo59 wrote:
woody-som wrote:or even try the rotor Q ring on the inner of a normal double. will reduce the effective size of the ring on the hardest part of the circle. I ride them, and find I actually use a bigger gear at the back now, since the change from normal chainrings.


Sorry? What does this mean in layman's terms please.

The rotor Q rings are not round. When your foot is at the top and bottom of the pedal stroke, you have less power in your legs to turn the gears, so the Q rings are smaller in this possition, and when your foot is at the 2-4 O'clock position, you have maximum power and the rings are actually bigger at this point than conventional rings.

I have both the small and large chainrings as Q rings, but you can just get the smaller one if you want.

loz*
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Postby loz* » Tue Sep 23, 2008 22:06 pm

Thanks again for the previous replies on this thread, they've been very useful.

I've decided that going triple will be too expensive (my sora shifters aren't triple compatible (model st-3300)).

Currently i've got 52/42 double chain rings and a 12-23 8 speed sora cassette. The front and rear derailleurs are also shimano sora.

The reason i'd like to get some easier gears is so i can use my older bike for some touring and i think i'd struggle to climb big hills day in , day out with the current setup.

So, my new plan is to get a Shimano HG50 8-speed cassette 11 - 32T
and a Shimano 3450 Sora 9-speed Compact chainset - 50 / 34T

Can anyone see a problem in this? I thought i'd wait and see if the rear derailleur works or not before getting another (i can't work out if my existing one is small/med/large!). Same logic with the chain, not sure if i'd need a different one so will just play it by ear. Guess I'll need tool for changing the cassette and chainrings too, any suggestions?

andrew_s
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Postby andrew_s » Sun Oct 05, 2008 14:18 pm

woody-som wrote:The rotor Q rings are not round. When your foot is at the top and bottom of the pedal stroke, you have less power in your legs to turn the gears, so the Q rings are smaller in this possition, and when your foot is at the 2-4 O'clock position, you have maximum power and the rings are actually bigger at this point than conventional rings.


Q rings won't get you a lower gear as the smallest radius can't be any smaller than the smallest possible with a round chainring. The smallest Q ring that will fit on 130 bcd road cranks is 40T, and the smallest Q ring that will fit on 110 bcd compact cranks is 36T, comared to 38/34 for round rings
What they do is to allow you to use a slightly higher gear, without losing as much momentum when the cranks are at 6/12 o'clock as with round rings.

adeyboy
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Postby adeyboy » Tue Oct 21, 2008 20:20 pm

Assuming you change the cassette for one with bigger sprockets, will this then work OK straight away?
For instance I have a 12-26 SRAM 9 speed cassette, will any other 9 speed road cassette just slip in with the rest of the transmission system or will the rear mech need fiddling with etc? Seems a fairly simple job just to change cassette if that is all there is to it.

Went out on MTB today for first time since bought road bike 3 months ago, got to say that I tackle bigger hills on the road bike so a few more gears may help; the MTB granny ring is amazing! I'd forgotten really; I could sail up the Galibier on that!!!

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The Shiny
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Postby The Shiny » Wed Nov 12, 2008 08:50 am

Same question as above really, I have a Shimano 105 10spd 11-25 and I'm getting old.

Can I just change to a 12-27 and expect it to work without too much fiddling about?
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redddraggon
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Postby redddraggon » Wed Nov 12, 2008 09:20 am

The Shiny wrote:Same question as above really, I have a Shimano 105 10spd 11-25 and I'm getting old.

Can I just change to a 12-27 and expect it to work without too much fiddling about?


The only thing likely to cause a problem would be chainlength - but it's normally worth getting a new chain with a new cassette anyway.
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GavH
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Postby GavH » Sun Dec 07, 2008 13:17 pm

I have a 52/36 on the front and a 12-26 8 speed on the back. I have Shimano Sora 8 spd shifters. If I were to upgrade my square taper BB to a Hollowtech II and my front cranks to a 50/34 Compact to give me some extra breathing space on the bigger, longer hills, what other considerations do I need to take account of, or is it a straight swap out?
Thanks for any advice.

rickhotrod
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Postby rickhotrod » Sat Dec 13, 2008 02:09 am

I think you mean a 52/39 rather than a 52/36, otherwise you would already have a Compact.

Fitting a 50/34 would be a straight swap except for the need to lower the front mech a bit, and not using the two smallest sprockets with the 34 chainring if you have a short rear mech fitted.

Another option is to fit a 13-29 cassette with the 52/39. However, an 8-speed 13-29 cassette is not available off the shelf, so make it up using a 13-26 7-speed cassette and a 29 sprocket from a 14-34 7-speed cassette. Use the slightly thinner 8-speed spacers.

I have a 52/36 on the front and a 12-26 8 speed on the back. I have Shimano Sora 8 spd shifters. If I were to upgrade my square taper BB to a Hollowtech II and my front cranks to a 50/34 Compact to give me some extra breathing space on the bigger, longer hills, what other considerations do I need to take account of, or is it a straight swap out?

gbs
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Re: Help I need smaller gears - what can I do? A GUIDE

Postby gbs » Sun Jan 04, 2009 12:29 pm

Leedsblue wrote:
redddraggon wrote:Assuming a standard double (53/39 etc)


What is the default size on a standard road bike (i.e non custom specced). My 42/52 13-23 seems rather restrictive in a hilly area and I seem to see more people having a 39/50 set up.


Secondly, if you have a Campag set up and decide to change the cassette to give a bigger gear is there any reason to stay with Campag or go with say the SRAM which offers a bigger range or whatever cassette is available cheaply at the time

Good thread, thanks for starting


Did you get a response? I am struggling in the same way - lowest ratio available on my Campag setup is 39/23 = 1.7. I am hoping that x-27/29 cassette will solve the problem of 20% gradients.

Next issue: what are the tips for defeated, cleated riders forced to get off and walk? I do not want to fall again!

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redddraggon
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Postby redddraggon » Sun Jan 04, 2009 13:01 pm

gbs

13-29 cassettes are available. I assume you have 10 speed Campag?

Whether or not it makes 20% doable is dependant on an individual's fitness.

I've got a similar 34-25 to the 39-29 on my good bike, it just requires me to stand up for the steeper bikes

On my Audax/Winter bike, I've got 50/34 with 13-29, that makes getting up hills easy :lol:
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