shifting. which cogs!

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shifting. which cogs!

Postby rogklee » Wed Apr 20, 2011 11:29 pm

Hi guys,

I've switched from riding on a triple crankset to a double (full tiagra groupset) and the change in my shifting has me a little confused.

I typically ride with chain in the smallest front cog and shift the rear derailuer. Typically, on flats, I feel most comfortable with my rear cog in the 2-3rd smallest cog though. I can get the same candance if I switch the front to the larger cog and drop the rear cog a few gears, but it's annoying shifting the front and rear gears when I stop again.

Wondering what gear ratios are and what is the best gear ratio for people?
When should you be switching the front gear? Once the rear gears hit the middle cog?

Just looking for advise.

thanks, Roger
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by BNA » Thu Apr 21, 2011 3:07 am

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Re: shifting. which cogs!

Postby ColinOldnCranky » Thu Apr 21, 2011 3:07 am

As long as you have close enough spacing between rations and they cover a wide enough range, you can forget specific ratios. You will adjust them at any given time according to your needs and capacity at that time - Both of these change in the course of rides or days anyway.

The common advice revolves around not distorting your chain too much. I am sure that someone will raise it here so I will address another equally important issue and one that seems to pass a lot of people by.

It is best for the durability of your chain and hence your cogs, to ride with the largest front cog that still enables you to have a range of ratios to cover your needs, and only rarely needing to change the front one. Let me explain.

There is a tendency for riders to stick with using a smaller front cog that they started on but as their strength and as they increase thjeir capacity they move their rear derailleur further and further out. They would be better of making the change to the bigger front cog.

If you use a smaller front cog, then to get a similar ratio you will need to to have the chain on a smaller cog at the rear. This unnecessarily ups the forces at play on your rear cog set in a double whammy. First the tension of you chain will be closer to the axle so that, for a given torques on the rear wheel, there has to be a greater force (tension) on the cog. In addition, the chains tension will be distributed over less cogs on the rear wheel. So you get an exponentially increased load applied to each cog on the cluster.

"So what" you ask? Well, the chain will stretch at a faster rate than otherwise. And as your chain stretches, the rear cogs get worn in a little to accommodate the chain. At some time when you need a new chain, (which is partly a function of the stretch anyway) you do a swap and then find that your gears and chain perform poorly. Typically the bike will want to jump cogs when you apply a little extra oomph - to go up a gradient for example. Of course, you will have ditched your old chain, leaving you only one choice - replace the rear cluster. There is a hill outside my office and I have had so many people come to me over the years wondering why their chain is suddenly jumping off the bike.

btw, I used to run three quick release chains anyway. I managed a couple of hundred thousand, only changing the rear sprocket late in life when the knees required closer spaced gearing. With three chains I would keep spares lightly oiled and ready in a plastic bag. I could then conveniently switch to a clean one, especially needed in winter. I could also clean them at my convenience. If you ride with correct gearing and do basic maintenance your cluster should outlast many chains. If you use on ly one chain then you may be for a new cluster before you needed to be.

(It's all academic to me now - I now have no problems with chains, clusters or derailleurs. :mrgreen: )
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Re: shifting. which cogs!

Postby Ross » Thu Apr 21, 2011 9:11 am

I tend to stay in the big ring on the front most of the time and try not to go below the second largest on the rear. Obviously if I'm doing hill work I need to change to small front chainring but I try to do this as I approach the hill (or close to the bottom where it isn't as steep - easy to drop a chain while shifting front derailleurs under a big load) and at the same time flick the rear up (to smaller cogs) two or three gears.
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Re: shifting. which cogs!

Postby chill » Thu Apr 21, 2011 1:45 pm

Big chainring, it's better for your cycling in the long run. You'll become a stronger rider. Obviously don't dismiss the small chainring and use it when appropriate. 90+ rpm is good start.
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Re: shifting. which cogs!

Postby eeksll » Thu Apr 21, 2011 4:14 pm

excluding the extremes (big chain ring smallest cassette/small chain ring big cassette), I'll pretty much try to keep the chain in the middle 4 cassette rings at the back.

I have a compact and 105 gears.
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Re: shifting. which cogs!

Postby rogklee » Thu Apr 21, 2011 5:55 pm

Alright, great info, I'll give it a shot tommorow and try to stick to the front large cog. I'm sure I'll get used to it.

Let you know the results!
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Re: shifting. which cogs!

Postby ColinOldnCranky » Thu Apr 21, 2011 6:26 pm

rogklee wrote:Alright, great info, I'll give it a shot tommorow and try to stick to the front large cog. I'm sure I'll get used to it.

Let you know the results!


Roger, i hope we have not mislead you. We encourage you to migrate to the larger chain ring. But only as you are ready - when you find that you are using a smaller rear cog than previoulsy. At some point, you should then switch to the largest front ring as your default, thereby back to use of your middle cogs on your cluster.

The only reason you would use the inner chain rings would be if you were not up to it. No shame there, it takes time to build and you will develop comfort in a higher cadence in the process. There are reasons (discussed ad nauseum in other threads) to NOT push to high a gear and too low a cadence.

But, as Chill implied, take your time.
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Re: shifting. which cogs!

Postby ColinOldnCranky » Thu Apr 21, 2011 6:33 pm

ColinOldnCranky wrote:
rogklee wrote:Alright, great info, I'll give it a shot tommorow and try to stick to the front large cog. I'm sure I'll get used to it.

Let you know the results!


Roger, i hope we have not mislead you. We encourage you to migrate to the larger chain ring. But only as you are ready - when you find that you are using a smaller rear cog than previoulsy. At some point, you should then switch to the largest front ring as your default, thereby back to use of your middle cogs on your cluster.

The only reason you would use the inner chain rings would be if you were not up to it. No shame there, it takes time to build and you will develop comfort in a higher cadence in the process. There are reasons (discussed ad nauseum in other threads) to NOT push to high a gear and too low a cadence.

But, as Chill implied, take your time.


A comment on eeksll's comment - (assuming a proper combination of chain wheel and sprocket) you would stick to the middle of the rear cogs if you were running in the middle chain ring up front. As you move out to a bigger chain ring, you will use the four or so cogs on the outside of the cluster. Conversely, if you are in need of going all the way in with your chainwheel (extreme hill for example) then you will limit the rear cogs used to the four or so on the inside of the cluster. Inner-IN; Middle-Middle; Outer-OUT. Obviously there will be some combinations of strength/ratios/road conditions that would determine you may deviate a bit, but in general...
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Re: shifting. which cogs!

Postby stang1 » Thu Apr 21, 2011 9:07 pm

In the mean time..

Jens' big ring is 56. His rear cassettte is 11-11-11-11-11-11-11-11-11-12.
http://www.jensvoigtfacts.com/

Dunt think shifting applies to jens !
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Re: shifting. which cogs!

Postby mekore » Fri Apr 22, 2011 12:20 am

rogklee wrote:Hi guys,

I typically ride with chain in the smallest front cog and shift the rear derailuer. Typically, on flats, I feel most comfortable with my rear cog in the 2-3rd smallest cog though. I can get the same candance if I switch the front to the larger cog and drop the rear cog a few gears, but it's annoying shifting the front and rear gears when I stop again.


thanks, Roger


It seems to me that you need a smaller big chainring, try to find cross chainring, or specialites TA made rings in many option of tooth. I do think that stock cranks have chainrings that is too big for us, non UCI elites....
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Re: shifting. which cogs!

Postby rogklee » Sat Apr 23, 2011 3:03 pm

Went for a ride today,

Tried to stick to the large front cog and it was quite alright. Just had to stand up to get myself moving from a starting position.


Sure will get used to it soon.

Roger
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Re: shifting. which cogs!

Postby eeksll » Sat Apr 23, 2011 11:08 pm

rogklee wrote:Went for a ride today,

Tried to stick to the large front cog and it was quite alright. Just had to stand up to get myself moving from a starting position.


Sure will get used to it soon.

Roger


I think you should use the smaller front cog as there is a reason for having gears :). I have a compact crankset which means I have 34/50 tooth fornt chain ring. I usually drop to the smaller front cog when stopping for a traffic light then move to the bigger cog when I pick up some speed. But sometimes I need to do some hard pushing when I change up too early.

I think the idea is you try to keep a 90 ish rpm cadence. (to the original question) what ever gear your on to match that 90 rpm you can probably find a combination front/rear cog where you will be riding with the chain in the middle section of the rear cassette.

push the point a little further, thats the point of having multiple gears, you can pick the gear to match your 90ish rpm. I dont think going the other way around is the way to do it (i.e. picking a gear and trying to use it all the time)
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Re: shifting. which cogs!

Postby waramatt » Thu Apr 28, 2011 9:48 pm

I do two thirds of my riding on SS (42:16 and 48:18) and I reckon it has helped me on the road bike. 12 months ago my LBS guy told me he never uses anything but the big chainring. I thought he was talking cr@p but here I am a year later riding 99% of time in big chain ring (53T), including all but monster hills. So I think it is a transitional thing for most new riders, especially if in process of building up weekly km. From a standing start (e.g. red light) I now stay in big front ring but shift back to 53:24 or so and gradually move through the gears.

But a year ago that 39T smaller front chain ring was my best friend, so I say just give it time, and experiment until you find what feels 'right".
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Re: shifting. which cogs!

Postby Eugene » Fri Apr 29, 2011 6:56 am

Noob input.

I have a 3 ring front and 9 speed (tiagra), I now do 95% of riding on the "big" front ring, took me a few weeks to get there, I will drop to the middle ring if required, but I dont use the full spread of rear gears, for example.

I only use the 6 smallest rear gears 3 to 9 when on big ring, if I need lower I will drop to middle ring and choose rear gear to suit.

I only use the middle 5 gears when on mid ring

I rarley use the smallest ring but only use the first 3 gears as I just dont need that much reduction.

The amount of bending in the chain if I go outside these selections is pretty high, I also hate hearing derailer noise of any kind, this also stops all noise.

The thought of a chain failing as I am standing up pushing my guts out up a hill does not fill my heart with joy, so I do all I can to extend its good health, I have broken several chains on mountain bikes while pushing hard up steep hills with less than enjoyable results.
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Re: shifting. which cogs!

Postby rogklee » Mon Jun 20, 2011 11:36 pm

Update!

Been a few months now, and have definately switched over to the larger cog 90% of the time. Harder to push and get your rpm but definitely worth it. Noticed my av. speed going up significantly from low 20s to high 20s to 30km/hr.

Thanks for input guys
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