Gearing Questions

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Gearing Questions

Postby andione1983 » Sun Jul 14, 2013 11:38 am

Hi guys, i have a few questions on Gearing..
im new to all this stuff so bear with me..
background.. i am newish to riding, and slowly building up my stamina currently riding mostly flats on road bikes, and occasionally wil try the big hill like Mt. Dandenong in Melbourne..
Anyway cut to the chase,

When ordering a Shimano 10 Speed cassette
i get these options
11-25
11-28
12-25
12-27
what do they mean, and what would i choose?

then

Shimano 105 10 speed chainset
i get these options
5750 Compact 170 34/50
5700 170 39/53
5750 compact 172.5 34/50
5700 172.5 39/53
5750 compact 175 34/50
5700 175 39/53
what the heck do they mean?
Comapact?
whats the different numbers mean?
which one would i pick?
___________________________________--
i am a little confused at this stage, any help would be appreciated
thanks
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by BNA » Sun Jul 14, 2013 11:41 am

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Re: Gearing Questions

Postby andione1983 » Sun Jul 14, 2013 11:41 am

Also i am tossing up between shimano 105 (5700) or Ultegra (6700) groupsets
is there alot of difference between the performance on the two? keep in mind i am no pro yet ;)
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Re: Gearing Questions

Postby ozdavo » Sun Jul 14, 2013 12:02 pm

andione1983 wrote:When ordering a Shimano 10 Speed cassette
i get these options
11-25
11-28
12-25
12-27
what do they mean, and what would i choose?

These numbers refer to the number of teeth on the smallest and largest cogs on the cassette. 11-25 is a fairly standard cassette, 11-28 is better for hills.

Shimano 105 10 speed chainset
i get these options
5750 Compact 170 34/50
5700 170 39/53
5750 compact 172.5 34/50
5700 172.5 39/53
5750 compact 175 34/50
5700 175 39/53
what the heck do they mean?
Comapact?

5700 is a std crankset with 130mm BCD, 38 tooth is the minimum tooth capacity 5750 Compact is a crankset with 110mm BCD.
The 170/172.5/175 refers to the crank length in mm (your current one should have its length on the inside of each crank arm).
34/50 & 39/53 refer to the number of teeth on each chainring.

Difference between 105 & Ultegra is appearance and a small amount of weight. They are functionally the same.

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Re: Gearing Questions

Postby Duck! » Sun Jul 14, 2013 12:16 pm

ozdavo wrote:
andione1983 wrote:When ordering a Shimano 10 Speed cassette
i get these options
11-25
11-28
12-25
12-27
what do they mean, and what would i choose?

These numbers refer to the number of teeth on the smallest and largest cogs on the cassette. 11-25 is a fairly standard cassette, 11-28 is better for hills.

Shimano 105 10 speed chainset
i get these options
5750 Compact 170 34/50
5700 170 39/53
5750 compact 172.5 34/50
5700 172.5 39/53
5750 compact 175 34/50
5700 175 39/53
what the heck do they mean?
Comapact?

5700 is a std crankset with 130mm BCD, 38 tooth is the minimum tooth capacity 5750 Compact is a crankset with 110mm BCD.
The 170/172.5/175 refers to the crank length in mm (your current one should have its length on the inside of each crank arm).
34/50 & 39/53 refer to the number of teeth on each chainring.

Difference between 105 & Ultegra is appearance and a small amount of weight. They are functionally the same.

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To expand slightly: BCD is Bolt Circle Diameter, referring to the mounting bolts for the chainrings. "Compact" cranks have a smaller BCD to enable the fitting of smaller chainrings (for lower gearing) than a "traditional" crankset.

5700 is simply the groupset model code, identifying the current series of 105. xx50 is the identifier for a compact crankset within any groupset.
I had a thought, but it got run over as it crossed my mind.
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Re: Gearing Questions

Postby ldrcycles » Sun Jul 14, 2013 12:25 pm

What ozdavo said. Gearing depends on the road you ride and your fitness/strengths.

I like riding up big hills, but also don't like running out of gears on the way back down, so my bike has a 52-39 crankset and 12-28 cassette (i'm not sure what the cassette is, other than cheap, i don't think an 11-28 was available for the same price, otherwise i would have one of those).

The idea behind 11-25 or 11-23 cassettes is to reduce the gaps between gears, IMO justified when the choice was only 5 or 6 speeds (one of my bikes has a 5 speed 14-28 and the jumps on that are HUGE) but when you're talking 9 or 10 speeds it's bollocks. I reckon a 52-36 "semi compact" crankset matched to an 11-28 cassette would be the perfect all round solution.
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Re: Gearing Questions

Postby andione1983 » Sun Jul 14, 2013 12:54 pm

so whats the difference between the 5700 and the 5750 compact? is it physically smaller? why do they call it compact?
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Re: Gearing Questions

Postby Abby » Sun Jul 14, 2013 12:56 pm

Some quick, unstructured thoughts:

For the cassette, get 105 over ultegra - they are a consumable, & you won't see a performance difference.
For teh chainset - get Ultegra over 105. I believe the chainrings are better. That said, if you can't afford Ultegra, don't lose any sleep over it, 105 is still great.

Cassette ratio - personally, I believe the 11-tooth is a bit of a waste of time. That's just me personally though, it depends on rider style. I would go a 12-25 or 12-27, as you will get more use of the extra cog in the middle of the range than for a mad descent (just coast!!). I currently use a 12-25, and very rarely use the 12, if I had an 11 it would stay shiny and untouched... ;)

Chainset - if you are planning (& genuinely think you'll do it) regular trips into the hills, get the compacts. :)

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Re: Gearing Questions

Postby andione1983 » Sun Jul 14, 2013 1:05 pm

Abby wrote:Some quick, unstructured thoughts:

For the cassette, get 105 over ultegra - they are a consumable, & you won't see a performance difference.
For teh chainset - get Ultegra over 105. I believe the chainrings are better. That said, if you can't afford Ultegra, don't lose any sleep over it, 105 is still great.

Cassette ratio - personally, I believe the 11-tooth is a bit of a waste of time. That's just me personally though, it depends on rider style. I would go a 12-25 or 12-27, as you will get more use of the extra cog in the middle of the range than for a mad descent (just coast!!). I currently use a 12-25, and very rarely use the 12, if I had an 11 it would stay shiny and untouched... ;)

Chainset - if you are planning (& genuinely think you'll do it) regular trips into the hills, get the compacts. :)

Cheers,
Abby

great advice people.. its slowly sinking in... i will read above comments a number of times before i decide,
im leaning towards these options at this stage
12-27
and
5750 compact 175 34/50

correct me if you think i should do something different
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Re: Gearing Questions

Postby Philipthelam » Sun Jul 14, 2013 1:32 pm

Do you even know how gears work?

Big on cassette - easier to pedal but not as fast (for climbing)
Small - harder to pedal but you go faster (for fast descents/flats)

Other way round for the front.

pretty simple.

Hence the 11-28 cassette will have a lower low gear but the same high gear as the 11-25. However it will have a larger gap between gears after the 21 sprocket (going from 21-24-28 as opposed to 21-23-25).

Google compact vs standard crank. I think you would want a compact.

Make sure you get the right crank length as well.
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Re: Gearing Questions

Postby andione1983 » Sun Jul 14, 2013 1:55 pm

Philipthelam wrote:Do you even know how gears work?

Big on cassette - easier to pedal but not as fast (for climbing)
Small - harder to pedal but you go faster (for fast descents/flats)

Other way round for the front.

pretty simple.

Hence the 11-28 cassette will have a lower low gear but the same high gear as the 11-25. However it will have a larger gap between gears after the 21 sprocket (going from 21-24-28 as opposed to 21-23-25).

Google compact vs standard crank. I think you would want a compact.

Make sure you get the right crank length as well.


i understand the above, bit about the cassette, larger is easier to push/slower speed
and front bigger is harder to push and faster, etc..

when it comes to the casette, so if there is 12 teeth on the small does that mean if it has one more tooth 11 to 12 does it mean its harder to push with 1 more tooth? or easier...
I think i would prefer a combination that gives me more speed.. as i never really use the really low gear (the easy to push/ slow speed is that low? )
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Re: Gearing Questions

Postby andione1983 » Sun Jul 14, 2013 2:03 pm

my crank on my Merida presently is 175 (came stock )
other gearing i could work out on the Merida is
175 - 34-50
and
12T/28T on the casette
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Re: Gearing Questions

Postby bychosis » Sun Jul 14, 2013 2:07 pm

On extra tooth on the back(cassette) willi be easier to push.

To get an idea which gear combination is higher or lower take the number of teeth on the front ring, divide it by the number of teeth on the back cog and you will get a ratio. Eg 53f, 12b = 4.42 and 50f, 11b= 4.55 a bigger ratio is harder to push, goes faster. So 53/12 combo is a lower/easier gear than 50/11. The ratio gives the number of wheel revolutions for each pedal revolution. Some people use gear-inches as a measure of gears, but it adds extra complexity to the calcs. It compares the number of revolutions of pedals to the inches you are used down the road. IIRC. Gear inches is handy when comparing gearing with different wheel sizes.
Last edited by bychosis on Sun Jul 14, 2013 2:08 pm, edited 1 time in total.
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Re: Gearing Questions

Postby open roader » Sun Jul 14, 2013 2:07 pm

Philipthelam wrote:Make sure you get the right crank length as well.


Excellent point just made. The majority of riders turn 172.5mm crank arms but you want to have a basic grasp on why this is so and how it affects your seat post length in relation to the frame size.

I too think you are best to opt for compact cranks and a 11-28 or 12-28 cassette as this appears to be what are riding with now. The cassette can be changed (by you with a couple of tools)) for a lower ratio cassette at minor expence. An 11 tooth sprocket is 'harder' to push than a 12 but unless you are looking for warp factor sprint speeds it is a moot point. I rarely use the last cog on my cassettes with 80% of the miles being ridden in the middle 7 or 8 cogs.

I ride with compact cranks and high-ish ratio cassettes all the time - I'm quite 'bike fit' but do ride over a lot of undulating and genuinely hilly terrain. If I was riding mostly flatter terrain I'd be thinking long and hard about standard cranks.
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Re: Gearing Questions

Postby Duck! » Sun Jul 14, 2013 5:28 pm

andione1983 wrote:so whats the difference between the 5700 and the 5750 compact? is it physically smaller? why do they call it compact?

Yes, it is smaller, specifically in the "spider" part of the crank - the five arms that the chainrings are bolted to. On a compact (in this case the 5750), these arms are 10mm shorter than the regular crank, 55mm from crank centre to chainring bolt centre vs. 65mm on the traditional, doubled to give the BCD of 110mm & 130mm respectively. The shorter spider arms allow the fitment of an inner chainring smaller than 38 teeth (39T is standard fitment, but 38T rings are available if you look around). Any smaller than 38T on a standard crank would have the chainring bolts fouling on the chain (or worse, partially outside the boundary of the chainring!).
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Re: Gearing Questions

Postby yarravalleyplodder » Sun Jul 14, 2013 7:36 pm

I have a compact 50-34 crank. Started off with 11-25 cassette and is fine for 1:20, the wall etc. I put on a 11-28 when I climbed donna. lake mountain & buller. I have left it on and I like the flexibility it gives me. I would definitely go for a 11 tooth cassette if your going for a compact crank, you will run out of gears around the 45km/h range if you go a 12
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Re: Gearing Questions

Postby Xplora » Sun Jul 14, 2013 7:37 pm

OP. Reflecting on your recent posts, and after googling your bike -

Do not change your crankset. You have a 50/34 which is perfectly adequate and is the de facto standard for road bikes now because unless you race, most dudes lack to power or passion to drive a standard 53/39 crank. It's not a huge difference anyways. Half a gear in the harder gears on the cassette. But very expensive to change :lol:

Your cassette is easy IMO. Get yourself a 12-23. This gets you a TON of gears in the 25-35kmh speed at 80-100rpm cadence. If you run out of gears charging down a hill, consider it good practice to spin up to 150rpm. :idea:

I personally had a BIG jump in my cycling when I went from 12-27 to 12-23 (and lately 11-23). It forces you to toughen up on some of the shorter climbs (because you can climb a lot of 100-200m pinch climbs in the big ring) and you are able to pick a good gear when you're spinning away with your mates on the flat. You'll appreciate the 16 and 18 cogs a lot, and those are the ones you miss first as the cassette gets wider. I found I was wimping out to the 24 and 27 a lot, instead of standing up and pushing through it with the 21 or 23. Also, the gaps between the 21-24-28 aren't very friendly for convincing you to get pushing hard. You have to "reset" your cadence and it's hard to get the rhythm flowing again when you're already struggling. You will struggle, for sure. But you'll get stronger, and you'll stop needing those bottom gears as much. Then you'll be FASTER. :shock:

Make no mistake - the 28 cog with a compact is only necessary for seriously crazy climbs or bailing you out. I was riding a 28 last weekend on the verge of cramping badly; the easy gear gave me some breathing space to get the water in and survive the climb. But you shouldn't be that silly. You are unlikely to be trying climbs after pushing 80kms quite hard for a while. It took me a couple years to get this far. This advice might not be conventional wisdom, but you do need to force yourself to improve and a 12-23 is a great way to do that.
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Re: Gearing Questions

Postby cerb » Mon Jul 15, 2013 2:06 pm

Suggest you look at a gear speed calculator like http://www.machars.net/bikecalc.htm

You can use the cassette ratios I mention below to put into the calculator. I mostly look at the variation between cadence (speed you spin the pedals at) & speed on the 'speed' tab. As a guide, on flat rides I aim for a cadence of 100. For hill climbs, I want to spin as close to 100 as possible but for anything over about 5% gradient, with a 34 on the front and 28 at the back, I can't sustain it and I need to slow my cadence. For any climb longer than 1-2km, I would always aim to keep my cadence above 60 otherwise I'll be cooked!

I've ridden a shimano 105, 50-34 (compact) chain ring since I started cycling 3-4 years ago. I originally rode a 11-25 cassette, but switched to a 11-28 to make steep and long climbs easier (able to spin at higher cadence for the same speed). For reference, I race crits in C/D grade and also ride hills/mountains around VIC. I'm fairly hefty at over 90kg (heavier makes climbing harder!).


Speed / Cadence
A compact chainring (50-34) is all you need and what I'd recommend. In the big ring (50) and the smallest ring on the cassette (11) at a cadence of 100, you are doing 56.9kph. Getting your cadence up to 110 will get you over 60kph - enough to win sprints in races up to B grade.

To illustrate the difference between the different cassettes for climbing, I've based the cadence at 60 for a tough long climb in the little ring (34):

With a 23 you'll be doing 11.1kph
With a 25 you'll be doing 10.2kph
With a 28 you'll be doing 9.1kph

Of course, you want to go as fast as possible, but going uphill with a 23 will mean that if you want to go slower than 11.1kph, then you have to push a slower cadence than 60, which hurts your legs more and isn't sustainable for as long period of time. i.e. Riding up a sustained 10% gradient, I know that I can't really ride faster than 11kph for any period of time. Now, I could do this in the 23 at a cadence of 60, or I could use a 28 with a more comfortable and easier cadence of 70. It also means that if the hill gets steeper, I can still drop my speed down to 9kph and maintain a cadence of 60.


Gear spacing
Gears for an 11-23 cassette go: 11-12-13-14-15-16-17-19-21-23
Gears for an 11-25 cassette go: 11-12-13-14-15-17-19-21-23-25
Gears for an 11-28 cassette go: 11-12-13-14-15-17-19-21-24-28

Apart from the different top end of the range (higher number is easier for going uphills), the only difference is the 'gaps' in the gearing. 11-23 having smaller transitions between gears than 11-28 (numbers go up by 1 instead of 2 or 3), which makes it easier to ride a particular cadence and speed. This can be a key factor if you only do flat riding or bunch riding where there is very little speed differences over the course of the ride and/or you want to maintain the same cadence throughout. As a new rider, I doubt this will bother you and it'd therefore be better to choose a cassette with a larger range of gearing which can take you anywhere.

Summary
I'd recommend selecting components that get the best flexibility out of your setup - a compact 50-34 chainring and an 11-28 cassette.

A 50-34 (compact) chainring still gives you good top end speed for sprinting (over 60kph at 110 cadence), but is easier for going uphill than a standard 'double' chainring.

The 11-28 cassette would be the best as it has the same 11 gear for going fast on the flat as the 11-23 or 11-25, but it has the larger 28 gear to help you be more comfortable with climbing.

The 11-25 cassette would be fine for flats, rolling hills and many climbs, but will really hurt you once you start pushing sustained (30mins+) and/or difficult (7%+ gradient) climbs.

The 11-23 is a waste of time unless you only ride flats or you like to ride up every hill out of the saddle with your legs burning. Even if you want to do this, you can still do it with an 11-25 by changing down a gear!
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Re: Gearing Questions

Postby Abby » Mon Jul 15, 2013 2:19 pm

Some very good advice in the more recent posts. I concur with keeping your current compact cranks.

As for the cassette issue. One good option, assuming you can afford it, is to have two back wheels - a flat-land wheel, & a climbing wheel (they can be the same brand/type, don't overthink it). Difference is maybe having a 12-23 cassette (or similar) on the flatland wheel, and a 12-27 (or similar) on the climbing wheel. Then its easy-peasy to do a quick 10-second change of wheel over depending on what the best cassette is for your ride that day.

Its actually pretty quick to change the cassette over too. But having a spare wheel to do it makes life easy... :)

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Re: Gearing Questions

Postby Xplora » Mon Jul 15, 2013 2:59 pm

It's also worth mentioning that part of the reason you climb hills is Achievement. You don't often have to climb 10% hills for any reason unless you want to. I crapped the bed with my 34/23 climbing Bowen Mountain, but that was a couple kilometres of 12% then a kilometre of 15-18% (holy moly). BIG nasty climb. After a century of fairly hard riding too. Most of your rides will be on the flats, so a 23 low will cover this. Yes, you'll hurt sometimes. That's not going to be fixed by going 28.
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Re: Gearing Questions

Postby hannos » Mon Jul 15, 2013 3:09 pm

I'm running a 50/34 up front and a 11/25 on the back most of the time.
I have a spare wheelset with a 12-28 on it for when I go to do climbs.

This setup suits me just fine for the type of riding I do.
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Re: Gearing Questions

Postby mitzikatzi » Mon Jul 15, 2013 3:29 pm

I would go a 11/25 or 12/27 cassette but change the front chain ring from 34 to 36.
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Re: Gearing Questions

Postby jimconte » Mon Jul 15, 2013 4:07 pm

yes keep your compact crank unless your young and are looking to go pro. My bike just happened to have 53/39 crank and 12-25 cassette and I wish I had a compact 50/34 as im certainly no tony martin on the flat and I sruggle on large climbs which I do often as I live in the hinterland and really wish I had a 34 tooth small chain ring I am now looking to buy a new cassette 11-30 to get up hills on those hard days but this will take away the clossness of my ratio,s which sucks but I can not afford to be changing chain rings which I would much prefrer.
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Re: Gearing Questions

Postby Derny Driver » Mon Jul 15, 2013 5:49 pm

cerb wrote:Suggest you look at a gear speed calculator like http://www.machars.net/bikecalc.htm

You can use the cassette ratios I mention below to put into the calculator. I mostly look at the variation between cadence (speed you spin the pedals at) & speed on the 'speed' tab. As a guide, on flat rides I aim for a cadence of 100. For hill climbs, I want to spin as close to 100 as possible but for anything over about 5% gradient, with a 34 on the front and 28 at the back, I can't sustain it and I need to slow my cadence. For any climb longer than 1-2km, I would always aim to keep my cadence above 60 otherwise I'll be cooked!

I've ridden a shimano 105, 50-34 (compact) chain ring since I started cycling 3-4 years ago. I originally rode a 11-25 cassette, but switched to a 11-28 to make steep and long climbs easier (able to spin at higher cadence for the same speed). For reference, I race crits in C/D grade and also ride hills/mountains around VIC. I'm fairly hefty at over 90kg (heavier makes climbing harder!).


Speed / Cadence
A compact chainring (50-34) is all you need and what I'd recommend. In the big ring (50) and the smallest ring on the cassette (11) at a cadence of 100, you are doing 56.9kph. Getting your cadence up to 110 will get you over 60kph - enough to win sprints in races up to B grade.

To illustrate the difference between the different cassettes for climbing, I've based the cadence at 60 for a tough long climb in the little ring (34):

With a 23 you'll be doing 11.1kph
With a 25 you'll be doing 10.2kph
With a 28 you'll be doing 9.1kph

Of course, you want to go as fast as possible, but going uphill with a 23 will mean that if you want to go slower than 11.1kph, then you have to push a slower cadence than 60, which hurts your legs more and isn't sustainable for as long period of time. i.e. Riding up a sustained 10% gradient, I know that I can't really ride faster than 11kph for any period of time. Now, I could do this in the 23 at a cadence of 60, or I could use a 28 with a more comfortable and easier cadence of 70. It also means that if the hill gets steeper, I can still drop my speed down to 9kph and maintain a cadence of 60.


Gear spacing
Gears for an 11-23 cassette go: 11-12-13-14-15-16-17-19-21-23
Gears for an 11-25 cassette go: 11-12-13-14-15-17-19-21-23-25
Gears for an 11-28 cassette go: 11-12-13-14-15-17-19-21-24-28

Apart from the different top end of the range (higher number is easier for going uphills), the only difference is the 'gaps' in the gearing. 11-23 having smaller transitions between gears than 11-28 (numbers go up by 1 instead of 2 or 3), which makes it easier to ride a particular cadence and speed. This can be a key factor if you only do flat riding or bunch riding where there is very little speed differences over the course of the ride and/or you want to maintain the same cadence throughout. As a new rider, I doubt this will bother you and it'd therefore be better to choose a cassette with a larger range of gearing which can take you anywhere.

Summary
I'd recommend selecting components that get the best flexibility out of your setup - a compact 50-34 chainring and an 11-28 cassette.

A 50-34 (compact) chainring still gives you good top end speed for sprinting (over 60kph at 110 cadence), but is easier for going uphill than a standard 'double' chainring.

The 11-28 cassette would be the best as it has the same 11 gear for going fast on the flat as the 11-23 or 11-25, but it has the larger 28 gear to help you be more comfortable with climbing.

The 11-25 cassette would be fine for flats, rolling hills and many climbs, but will really hurt you once you start pushing sustained (30mins+) and/or difficult (7%+ gradient) climbs.

The 11-23 is a waste of time unless you only ride flats or you like to ride up every hill out of the saddle with your legs burning. Even if you want to do this, you can still do it with an 11-25 by changing down a gear!

cerb wins the best advice prize. Re-read the above.

Just one thing to add - I always laugh at the number of people who think they can push a 53-11, or even a 50-11. I can accept (begrudgingly) that an 11 tooth cog may be used on the odd occasion with compact cranks, but for recreational cyclists to think they 'need 53-11 is kinda laughable. Even Greipel can only push that with a tailwind for 200 metres max.
Ok so there may be the rare occasion where you are on a long downhill with a huge tailwind and you may actually get the chain onto that shiny silver 11 for a couple of moments, but then for the rest of the ride you are alternating between your 15 (too hard) and 17 (too easy) because you sacrificed a 16 tooth cog so you could have the 11.
For me, on standard cranks, I'll take a 16 and an 18 in the middle of my cassette rather than a 11 and 12 any day. I would have 13, 14, 15, 16, 17, 18, 19, 21, 23, 25. No gaps / 1 tooth jumps = smooth and perfect cadence all day.
For compacts I would recommend 12 -27 or 12-28.
Crank length has been proven to be pretty much irrelevant. Most people think tall guys should have 175, short 170, "average" height 172.5 It probably makes no difference.
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Location: Wollongong

Re: Gearing Questions

Postby jimconte » Mon Jul 15, 2013 8:41 pm

Derny Driver wrote:
cerb wrote:Suggest you look at a gear speed calculator like http://www.machars.net/bikecalc.htm

You can use the cassette ratios I mention below to put into the calculator. I mostly look at the variation between cadence (speed you spin the pedals at) & speed on the 'speed' tab. As a guide, on flat rides I aim for a cadence of 100. For hill climbs, I want to spin as close to 100 as possible but for anything over about 5% gradient, with a 34 on the front and 28 at the back, I can't sustain it and I need to slow my cadence. For any climb longer than 1-2km, I would always aim to keep my cadence above 60 otherwise I'll be cooked!

I've ridden a shimano 105, 50-34 (compact) chain ring since I started cycling 3-4 years ago. I originally rode a 11-25 cassette, but switched to a 11-28 to make steep and long climbs easier (able to spin at higher cadence for the same speed). For reference, I race crits in C/D grade and also ride hills/mountains around VIC. I'm fairly hefty at over 90kg (heavier makes climbing harder!).


Speed / Cadence
A compact chainring (50-34) is all you need and what I'd recommend. In the big ring (50) and the smallest ring on the cassette (11) at a cadence of 100, you are doing 56.9kph. Getting your cadence up to 110 will get you over 60kph - enough to win sprints in races up to B grade.

To illustrate the difference between the different cassettes for climbing, I've based the cadence at 60 for a tough long climb in the little ring (34):

With a 23 you'll be doing 11.1kph
With a 25 you'll be doing 10.2kph
With a 28 you'll be doing 9.1kph

Of course, you want to go as fast as possible, but going uphill with a 23 will mean that if you want to go slower than 11.1kph, then you have to push a slower cadence than 60, which hurts your legs more and isn't sustainable for as long period of time. i.e. Riding up a sustained 10% gradient, I know that I can't really ride faster than 11kph for any period of time. Now, I could do this in the 23 at a cadence of 60, or I could use a 28 with a more comfortable and easier cadence of 70. It also means that if the hill gets steeper, I can still drop my speed down to 9kph and maintain a cadence of 60.


Gear spacing
Gears for an 11-23 cassette go: 11-12-13-14-15-16-17-19-21-23
Gears for an 11-25 cassette go: 11-12-13-14-15-17-19-21-23-25
Gears for an 11-28 cassette go: 11-12-13-14-15-17-19-21-24-28

Apart from the different top end of the range (higher number is easier for going uphills), the only difference is the 'gaps' in the gearing. 11-23 having smaller transitions between gears than 11-28 (numbers go up by 1 instead of 2 or 3), which makes it easier to ride a particular cadence and speed. This can be a key factor if you only do flat riding or bunch riding where there is very little speed differences over the course of the ride and/or you want to maintain the same cadence throughout. As a new rider, I doubt this will bother you and it'd therefore be better to choose a cassette with a larger range of gearing which can take you anywhere.

Summary
I'd recommend selecting components that get the best flexibility out of your setup - a compact 50-34 chainring and an 11-28 cassette.

A 50-34 (compact) chainring still gives you good top end speed for sprinting (over 60kph at 110 cadence), but is easier for going uphill than a standard 'double' chainring.

The 11-28 cassette would be the best as it has the same 11 gear for going fast on the flat as the 11-23 or 11-25, but it has the larger 28 gear to help you be more comfortable with climbing.

The 11-25 cassette would be fine for flats, rolling hills and many climbs, but will really hurt you once you start pushing sustained (30mins+) and/or difficult (7%+ gradient) climbs.

The 11-23 is a waste of time unless you only ride flats or you like to ride up every hill out of the saddle with your legs burning. Even if you want to do this, you can still do it with an 11-25 by changing down a gear!

cerb wins the best advice prize. Re-read the above.

Just one thing to add - I always laugh at the number of people who think they can push a 53-11, or even a 50-11. I can accept (begrudgingly) that an 11 tooth cog may be used on the odd occasion with compact cranks, but for recreational cyclists to think they 'need 53-11 is kinda laughable. Even Greipel can only push that with a tailwind for 200 metres max.
Ok so there may be the rare occasion where you are on a long downhill with a huge tailwind and you may actually get the chain onto that shiny silver 11 for a couple of moments, but then for the rest of the ride you are alternating between your 15 (too hard) and 17 (too easy) because you sacrificed a 16 tooth cog so you could have the 11.
For me, on standard cranks, I'll take a 16 and an 18 in the middle of my cassette rather than a 11 and 12 any day. I would have 13, 14, 15, 16, 17, 18, 19, 21, 23, 25. No gaps / 1 tooth jumps = smooth and perfect cadence all day.
For compacts I would recommend 12 -27 or 12-28.
Crank length has been proven to be pretty much irrelevant. Most people think tall guys should have 175, short 170, "average" height 172.5 It probably makes no difference.
jimconte
 
Posts: 32
Joined: Mon Jun 25, 2012 10:29 am

Re: Gearing Questions

Postby jimconte » Mon Jul 15, 2013 8:51 pm

Yes derny you are right about not needing a 11 or really even a 12 if your just an enthusiast as it is way to dangerous to go ripping down hills over 60km,s an hour with rim breaks and someone pulls out in front of you like you are invisible. Believe me I live half way up a catorgory 3 climb and am always going up and down everytime I leave home and it has happened countless times so I don't do over 45-50km per hour unfortunetly the shimano 105 cassetes when you need a 30 tooth only come with an 11 at the bottom I wish they made a 13-30 as ratio,s would be closer I know they make 13-25 but for some reason the larger than 30 tooth size only comes with an 11.
jimconte
 
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Joined: Mon Jun 25, 2012 10:29 am

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