Changing rear cassette for higher top end speed

tamaskan

Hey,
I currently run a compact 50/34 12/25t. I don't often use the lowest gear for climbing and on descents I feel I run out of gear at too low a speed. What cassette would u recommend I change to to get a higher top speed on the flats and descents without making it too difficult on the hills? I was thinking an 11/25, but are there any disadvantages to 11/25? I know very little about this subject.
Thanks for your help.

quozl

The only difference will be that somewhere where you used to have a 1 tooth jump you'll now have a 2 tooth jump.

Which you may not like or may not notice.

You should be able to find the list of teeth in both the cassette you have and the cassette you're swapping to then you can see exactly where things will change.

I don't know what cassettes you're using but here are two sample ones from 9 speed HG50 cassettes.

11-25T: 11,12,13,15,17,19,21,23,25
12-25T: 12.13.14.15.17.19.21.23.25

You can see that you're losing the 14 tooth ring and gaining the 11. So you'll be jumping straight from 13 to 15 with the 11-25 rather than having two smaller jumps with the 14 in the middle.

Will you mind that? Personally, I doubt it.

Muckers

The difference between an 11/25 and a 12/25 will be too little to notice if it's greater speed on the flats or descents your looking for. A far better but more expensive option is too replace the front chainrings with a standard 53/39, and descend like a pro.

Casati

Muckers wrote: »

The difference between an 11/25 and a 12/25 will be too little to notice if it's greater speed on the flats or descents your looking for. A far better but more expensive option is too replace the front chainrings with a standard 53/39, and descend like a pro.

This would be an expensive option, you'd likely need a new chain too as the original would be too short. I'd go for an 11 23, the 34 23 should get you over most hills and a 50 11 is big enough gear for Irish roads inc most racing

tamaskan

Muckers wrote: »

The difference between an 11/25 and a 12/25 will be too little to notice if it's greater speed on the flats or descents your looking for. A far better but more expensive option is too replace the front chainrings with a standard 53/39, and descend like a pro.

Problem with that is it will be pretty hard getting up the hills with that, no?

Dermot Illogical

Muckers wrote: »

The difference between an 11/25 and a 12/25 will be too little to notice if it's greater speed on the flats or descents your looking for. A far better but more expensive option is too replace the front chainrings with a standard 53/39, and descend like a pro.

+1.
Or change both and have 53x11 for high speed frolics.

Dermot Illogical

tamaskan wrote: »

Problem with that is it will be pretty hard getting up the hills with that, no?

Next time you're out try your 50x15. That's pretty much where your easiest gear would be if you had 39x12 as your climbing gear.

tamaskan

Dermot Illogical wrote: »

Next time you're out try your 50x15. That's pretty much where your easiest gear would be if you had 39x12 as your climbing gear.

Sorry everyone, I got it ALL WRONG. It's actually a 12/28 I have on the back. So if I want as close to two gears higher on both the top and bottom end, what would I be looking for?

Raam

11-25 sounds right for you.

Beasty

Muckers wrote: »

The difference between an 11/25 and a 12/25 will be too little to notice if it's greater speed on the flats or descents your looking for. A far better but more expensive option is too replace the front chainrings with a standard 53/39, and descend like a pro.

Moving from 50 to 53 on the front increases gearing by 6%
Moving from 12 to 11 on the back increases it by 8.3%

Changing the cassette is cheaper, easier and increases the gearing more than moving to a full groupset

Raam

Beasty wrote: »

Moving from 50 to 53 on the front increases gearing by 6%
Moving from 12 to 11 on the back increases it by 8.3%

Changing the cassette is cheaper, easier and increases the gearing more than moving to a full groupset

Bigger chainrings aint so pricey.
http://www.chainreactioncycles.com/Models.aspx?ModelID=18512

tamaskan

Beasty wrote: »

Moving from 50 to 53 on the front increases gearing by 6%
Moving from 12 to 11 on the back increases it by 8.3%

Changing the cassette is cheaper, easier and increases the gearing more than moving to a full groupset

Well I won't be changing the groupset. So switching to an 11 at the back increases my top gear by 8.3% which is the equivalent of 1 gear higher. Would that be right? And same goes for bottom gear being one gear higher too?

quozl

Raam wrote: »

Bigger chainrings aint so pricey.
http://www.chainreactioncycles.com/Models.aspx?ModelID=18512

Surely that won't fit on a compact as the BCDs are different?

So it would be an expensive change.

RockWerchter

Pedaling faster is also an option, the cheapest one too.

petethedrummer

Can someone point me to these big long descents where everyone is spinning out?

Raam

quozl wrote: »

Surely that won't fit on a compact as the BCDs are different?

So it would be an expensive change.

You can get 53 rings with different BCD and will fit on a compact chainset. I can never remember which designates which.

tamaskan

petethedrummer wrote: »

Can someone point me to these big long descents where everyone is spinning out?

Come visit south Kerry. Some nice long downhill straights and I spin out at 55kph. It grates at my soul. Help me choose the right cassette for my needs please before I throw my bottle at the next car that passes me out coming down a nice steep section where I should be doing 65kph rather than 55kph.

Raam

Spinning out at 55kph seems odd. Obvious but... are you defo in the big ring? What's your cadence when you spin out?

tamaskan

Raam wrote: »

Spinning out at 55kph seems odd. Obvious but... are you defo in the big ring? What's your cadence when you spin out?

I'm in the very top gear in the big ring. Feckin compacts:(

tamaskan

tamaskan wrote: »

I'm in the very top gear in the big ring. Feckin compacts:(

Not sure of the cadence but over 100 I'd imagine

tamaskan

tamaskan wrote: »

Not sure of the cadence but over 100 I'd imagine

So far from what I've heard, an 11/25 seems like my best bet unless I go change the front cogs. Anyone care to disagree?

el tel

Shimano Capreo cassette and free hub is what you need. It goes down to NINE (9).

tamaskan

el tel wrote: »

Shimano Capreo cassette and free hub is what you need. It goes down to NINE (9).

Yes but it's a 9 speed, so wouldn't that mean less gear selection choices?

petethedrummer

tamaskan wrote: »

Come visit south Kerry. Some nice long downhill straights and I spin out at 55kph. It grates at my soul. Help me choose the right cassette for my needs please before I throw my bottle at the next car that passes me out coming down a nice steep section where I should be doing 65kph rather than 55kph.

Would gravity not be your friend by that stage? There's a stage where it becomes pointless to try and get faster on a descent through pedaling. But yes a 11 tooth will help you in some sense to go faster. I suppose if it was a long shallow descent it might be useful.

I'd argue that having a cassette with smaller jumps or more lower end gears is preferable to having a huge gear. Especially if you are climbing up the mountain before you are descending it. But I have a low gear bias.

I suppose there's no harm in having a few different cassettes.

quozl

tamaskan wrote: »

Not sure of the cadence but over 100 I'd imagine

A 50/12 needs a cadence of 94 for 50kph according to http://home.earthlink.net/~mike.sherman/shift.html , so you may be able to up your cadence. 94 wouldn't be a high cadence.

I'd still get the new cassette - you'll see if you like it, they're cheap enough and tinkering with your bike is fun.

You'll need a chain-whip and a cassette lock-ring tool. Maybe this is your opportunity to buy one of the cheap x-tools bicycle toolkits from chainreactioncycles.com

Slippery slope time...

tamaskan

petethedrummer wrote: »

Would gravity not be your friend by that stage? There's a stage where it becomes pointless to try and get faster on a descent through pedaling. But yes a 11 tooth will help you in some sense to go faster. I suppose if it was a long shallow descent it might be useful.

I'd argue that having a cassette with smaller jumps or more lower end gears is preferable to having a huge gear. Especially if you are climbing up the mountain before you are descending it. But I have a low gear bias.

I suppose there's no harm in having a few different cassettes.

Yes u would think gravity would work in my favour, especially as I'm 95kg. When I start to spin out I go into a tuck position I don't continue to gain much speed. I am however getting me a nice set of Dura Ace C24 Wheels next week so that should help a little.

As for more lower end gears over more higher end gears, I'd rather have to mash up the hills and break my records coming down.

G rock

A cadence of over 100 surely isn't spinning out?

I sometimes hit 150 when riding downhill fixed. And there are many more experienced and stronger riders than me hitting higher rpms than that.

tamaskan

quozl wrote: »

A 50/12 needs a cadence of 94 for 50kph according to http://home.earthlink.net/~mike.sherman/shift.html , so you may be able to up your cadence. 94 wouldn't be a high cadence.

I'd still get the new cassette - you'll see if you like it, they're cheap enough and tinkering with your bike is fun.

You'll need a chain-whip and a cassette lock-ring tool. Maybe this is your opportunity to buy one of the cheap x-tools bicycle toolkits from TFT
Slippery slope time...

I love slippery slopes, as we all do. I was this close to getting a Felt F4 or Ar4 last week, but decided I'd be better off getting a nice new set of wheels, a new cassette and a turbo trainer and have €700 left over. After all, I like my Alu framed KTM Strada. It's a nice racy geometry, I reckon I'm better off giving it a few minor upgrades and lose some weight.

tamaskan

G rock wrote: »

A cadence of over 100 surely isn't spinning out?

I sometimes hit 150 when riding downhill fixed. And there are many more experienced and stronger riders than me hitting higher rpms than that.

To be honest G Rock I only got my cadence metre recently and haven't been on a spin out descent since so I could have been well over 100, I dunno. All I know is I am spinning out in top gear and I wanna sort it out.

petethedrummer

tamaskan wrote: »

As for more lower end gears over more higher end gears, I'd rather have to mash up the hills and break my records coming down.

Well each to their own. But remember my sage advice next time climbing gets tough and you shift the lever but nothing happens. :pac:

G rock

I suppose it would be nice to say that "this one goes to eleven"!

tamaskan

petethedrummer wrote: »

Well each to their own. But remember my sage advice next time climbing gets tough and you shift the lever but nothing happens. :pac:

Well all I can say to that is I borrowed an AR4 with 52/36 and did my usual ride between Kenmare and Killarney. I struggled more than usual up the first 9k uphill but surprisingly beat my previous best time by nearly 2 minutes. However the next 20 k are mostly downhill or flat and I knocked 14 minutes off that section. So I reckon the struggle up the hill is worth the thrill of the high speed downhill.

tamaskan

G rock wrote: »

I suppose it would be nice to say that "this one goes to eleven"!

Excuse my ignorance, but what u mean by that?

Dermot Illogical

https://www.youtube.com/watch?v=EbVKWCpNFhY

tamaskan wrote: »

Excuse my ignorance, but what u mean by that?

It's a Spinal Tap quote.

tamaskan

Dermot Illogical wrote: »

It's a Spinal Tap quote.

Really gotta watch that, everyone is always quoting it.

tamaskan

By the way, who here is at work?

tamaskan

Dermot Illogical wrote: »

https://www.youtube.com/watch?v=EbVKWCpNFhY

It's a Spinal Tap quote.

Just watched the clip, priceless. That is pure class and so appropriate for this thread. Thanks Bud.

petethedrummer

tamaskan wrote: »

By the way, who here is at work?

anyone responding is in work.

kingoffifa

back on track.

cheap option is get a cassette with an 11 on it. 11-25 sounds good enough.

i have been able to manage away on it. noticeable difference to a 12-25 to me anyways.

kumate_champ07

do some barbell squats and learn to spin faster = higher top end speed

tamaskan

kingoffifa wrote: »

back on track.

cheap option is get a cassette with an 11 on it. 11-25 sounds good enough.

i have been able to manage away on it. noticeable difference to a 12-25 to me anyways.

Thanks King. So 11/25 is manageable on the hills but a noticeable difference in top speed and decending?

Brian?

petethedrummer wrote: »

Can someone point me to these big long descents where everyone is spinning out?

N81 towards Tallaght. I spin out a 50x11. That's not even a long descent.

2 Wheels Good

Gear speed calculator here
You can compare the difference in mph/km between a 50x12 and a 50x11. 32.5mph vs 35.5 at 100rpm (These seem a bit low to me)

Brian?

2 Wheels Good wrote: »

Gear speed calculator here
You can compare the difference in mph/km between a 50x12 and a 50x11. 32.5mph vs 35.5 at 100rpm (These seem a bit low to me)

I think the term "spinning out" needs to be defined here.

To me it's when I'm pedalling as fast as I can and it's not adding any momentum.

An I wrong?

tamaskan

Brian? wrote: »

I think the term "spinning out" needs to be defined here.

To me it's when I'm pedalling as fast as I can and it's not adding any momentum.

An I wrong?

Spot on I'd say.

ROK ON

Imho it is not very likely to spin out on a descent at 55kmph.
I am familiar with every climb and descent in Sth Kerry, I have hit max speeds of 90km on one descent and have not spun out.

I have hit max speed of 72kmph descending Molls Gap to Kenmare and it was only laziness and lack of fitness that prevented me from spinning more.
I have done all of the descents with a higher gear ranging from 53-12 to 50-11 and I have not spun out ever.
Most of the time that I reduced my pedalling was I order to tuck a little further.

On a turbo trainer with no resistance I have hit a max cadence of 147 on a 50-11 and I do mkt believe I spun out - I nearly passed out, but that's not te same.

tamaskan

ROK ON wrote: »

Imho it is not very likely to spin out on a descent at 55kmph.
I am familiar with every climb and descent in Sth Kerry, I have hit max speeds of 90km on one descent and have not spun out.

I have hit max speed of 72kmph descending Molls Gap to Kenmare and it was only laziness and lack of fitness that prevented me from spinning more.
I have done all of the descents with a higher gear ranging from 53-12 to 50-11 and I have not spun out ever.
Most of the time that I reduced my pedalling was I order to tuck a little further.

On a turbo trainer with no resistance I have hit a max cadence of 147 on a 50-11 and I do mkt believe I spun out - I nearly passed out, but that's not te same.

Thanks for your very thorough reply ROK. Glad u know the roads of south kerry so well. I'll tell u where I have spun out recently... On the back road between Sneem and Molls Gap, coming from Sneem. I definitely was spinning out at 55kph, as I could feel no momentum being added by me pedalling in top gear (50/12). Can't explain it, but it's true.

tamaskan

Brian? wrote: »

N81 towards Tallaght. I spin out a 50x11. That's not even a long descent.

At what speed were u spinning out Brian?

Dermot Illogical

tamaskan wrote: »

I definitely was spinning out at 55kph,

How are you measuring your speed?

Lumen

tamaskan wrote: »

Thanks for your very thorough reply ROK. Glad u know the roads of south kerry so well. I'll tell u where I have spun out recently... On the back road between Sneem and Molls Gap, coming from Sneem. I definitely was spinning out at 55kph, as I could feel no momentum being added by me pedalling in top gear (50/12). Can't explain it, but it's true.

Momentum is speed (your mass is a constant). So you're saying you couldn't spin your legs faster, even though you had power to spare (or else how would you drive an 11?).

Pro cyclists used 53/13 as a maximum gear not so long ago, and that's smaller than 50/12.

AFAIK junior riders are restricted to something like 52x14, and they're bloody quick.

You're doing it wrong. Just turn your legs faster. It's a neuromusclar thing.

tamaskan

Dermot Illogical wrote: »

How are you measuring your speed?

For the past couple