Change from compact to triple or change the cassette?

popette

If I were wanting to get lower gears on a bike, currently with shimano ultegra 50/34 25/12 (I think), what would be the best way of going about it?

I've already asked my bike shop about going from compact to triple and they said that I would need to possibly change the bottom bracket, the left gear changer and the chain (as well as the triple bit of course).

It's been suggested to me that changing the cassette might be easier. I've looked on bike websites and seen that I could get a 9speed shimano mtb cassette, 32/11 for about £90 (there are cheaper but this one is nice and light). This would give me lowest gear of 28", which is lower than what I currently have and sounds good. However, the current cassette is 10speed and I'm not sure if it's possible to change from 10 to 9 speed without having to make other changes. What are the limiting factors on which cassette you can put on the back without having to rework everything else.

I hope all that makes sense - what do you think?
Many thanks in advance guys

dennisn

Change the cassette to a 12-27. You can also get a 33 tooth compact inner ring from TA Specialties(110BCD).

Dennis Noward

willbevan

Limiting factors to the cassette on the back...

Rear mech max sprocket size on road bike is much smaller than on MTBs. I have had a 32T on a sora mech, which i think max on the stats was 27T. It worked, but you could hear a ping sound every now and again when you changed that made me nervous (was with a 50/34 chainring like you, now using an XT rear mech)

Right shifter, as 9 speed doesn't have the same spacing as 10 speed so that would need to be changed.

Rear Hub - Might have to change the rear wheel/hub if your current wheels are 10speed only, don't think this is common mind you.

If you had a 9 or 8 speed system i would of said, get a larger cassette, 11-32 or 11-34 (what i've done lol) and get a MTB rear mech....

But since your 10 speed and the max you can have is a 12-27T i think... doesn't give you much over a 12-25T

As the chap mentioned above you can get a 33, rather than a 34, and change to a 27, but that affectively only gives you one gear lower than you have now (% difference being aprox equal per gear, someone correct me if im wrong here as only just did a quick sum)

You havn't mentioned how much lower you want?

As if you want to go a lot lower, then think unfortunety tripple is the only way to go, as you can reduce the chainring AND increase the rear cassette size

If you don't, and just change the cassette a bit, and reduce the chainring 1, will you in the future regret it? as you can always not use the bottom gears, but if you don;t have them.

just my two p anyway.. as i bought a double, switched it to a compact, and wish i had bought the tripple (im a weak cyclist mind you)

pugwashcp

I bought myself a 10 speed Mars cassette from sjs cycles. It has a similar spread of gears to a mountain bike (11-34) and I've had no problems running it with my 105 mech.

It got me up the bwlch-y-groes on last years wild wales!!

Mettan

I'm currently running a 50/34 Compact with a HG40 11/32 cassette and MTB rear deraileur - it works well (although I am running an 8-speed admitedly) - not sure about the 10 to 9 thing, although as a concept, the 50/34 with a mtb 11/32 cassette and a mtb rear deraileur does work well enough - I've only been up to 15-18 % approx on my newish setup but the 34/32 does give a certain amount of "comfort" and security towards the end of a climb (if need be).

willbevan

pugwashcp wrote:

I bought myself a 10 speed Mars cassette from sjs cycles. It has a similar spread of gears to a mountain bike (11-34) and I've had no problems running it with my 105 mech.

It got me up the bwlch-y-groes on last years wild wales!!

Oh thats worth knowing:)

popette

Thanks for your replies so far guys

redddraggon

You can get a SRAM 11-28 10 Speed Cassette.

£45

Surely 34-28 should get you up anything (at least in this country)?

popette

I'm doing the Etape so that's what I'll be using it for. My triple (winter bike) has lowest gear of 31 inches. I would like the new bike with compact to have a similar low gear, or maybe a little lower. 34-28 would give me 32 inches so that's not too bad actually.
I'm not so bothered about the costs (within reason - perhaps up to £300) - I just want the bike set up right. When I watched that DVD of the guys climbing the Tourmalet, they were struggling on their gears and their advice was not to be macho and make sure you have low enough gearing. I would much rather have a really low gear option that I may not even use than struggle and possibly have to walk, wishing I'd gone for lower gears.

redddraggon

There's always a custom cassette, upto 30T

http://www.parker-international.co.uk/P ... b906a75f51

Surely 34-30 is small enough? A long cage mech will probably be required aswell. You wouldn't need a MTB mech.

maddog 2

foreign climbs are usually longer and less steep than, say, Lake District climbs like Honister or (the wall that is) Hard Knott, so you should be okay with a 34 ring and a 12-27.

Going to a mtb cassette is prohibitively expensive as you'll need to change your shifters, cassette and mech.

33t 110bcd rings are techincally possible but I've never seen any for sale.

andy_wrx

Aren't you being given a shiny new Felt then, Popette ?


These big Continental climbs are different to what we have in this country, is my opinion.
My Winter bike is a triple but I never use the inner ring in Cheshire, just if I go to the Peak District and I hit Winnats at 1:4 or something.
My Summer bike has 36 x 27 compact on it and gets me round UK sportives, including up Winnats and Mow Cop, but out of the saddle.

I took the compact to France last year and felt decidedly overgeared - I wanted perhaps two lower gears to spin as I was just grinding in a seated position all the time and it was knackering doing it daily for a week.
The climbs weren't steep, 7 or 9%, but they went on forever, upto 10 or 15 miles for instance, and are built at a very steady regular grade.
They're not like our climbs where they have steep bits, flatter bits, steeper bits, flatter bits, you push on some bits and then recover, push again out of the saddle, recover seated, etc.
When it says 7-9% for 10 miles, it really means 7% to 9% for 10 miles and there aren't those flatter bits to recover on.

popette

andy_wrx wrote:

Aren't you being given a shiny new Felt then, Popette ?


These big Continental climbs are different to what we have in this country, is my opinion.
My Winter bike is a triple but I never use the inner ring in Cheshire, just if I go to the Peak District and I hit Winnats at 1:4 or something.
My Summer bike has 36 x 27 compact on it and gets me round UK sportives, including up Winnats and Mow Cop, but out of the saddle.

I took the compact to France last year and felt decidedly overgeared - I wanted perhaps two lower gears to spin as I was just grinding in a seated position all the time and it was knackering doing it daily for a week.
The climbs weren't steep, 7 or 9%, but they went on forever, upto 10 or 15 miles for instance, and are built at a very steady regular grade.
They're not like our climbs where they have steep bits, flatter bits, steeper bits, flatter bits, you push on some bits and then recover, push again out of the saddle, recover seated, etc.
When it says 7-9% for 10 miles, it really means 7% to 9% for 10 miles and there aren't those flatter bits to recover on.

Hi Andy,
Yes, I'm getting a lovely new felt which I couldn't be more chuffed about. The gears are a bit of a worry for me though - like you say, Tourmalet is 25 miles of climbing - about 20km of those averaging out at 7%. I want to be spinning my way up not grinding.
If I had lowest gear equivalent to my triple, I think I could probably manage it.

I cycled with someone from wilmslow last weekend on my way to Sandbach - it wasn't you was it?

willbevan

redddraggon wrote:

There's always a custom cassette, upto 30T

http://www.parker-international.co.uk/P ... b906a75f51

Surely 34-30 is small enough? A long cage mech will probably be required aswell. You wouldn't need a MTB mech.

Would liketo add, long cage/short cage, thats not what decides the maximum sprocket size the rear mech can handle.

I have run 28T and a 32T on a short cage mech, and yesthe chain tention was tight(to tight), but the real factorws what the mechs max rear sprocket size is, most road ones are 27(shimano, not sure about campag)... you can put more in,but it starts getting very tight(rear sprocket and wheels onthe rear mech),i switched to a MTB mech becuase of this...

You might not have a problem as reddragon is suggesting,but from mylimited expereince i think its worth mentioning,... as im did exactly what your thinking, went for a compact and a large rear cassette rather than a tripple...

redddraggon

willbevan wrote:

I have run 28T and a 32T on a short cage mech, and yesthe chain tention was tight(to tight), but the real factorws what the mechs max rear sprocket size is, most road ones are 27(shimano, not sure about campag)... you can put more in,but it starts getting very tight(rear sprocket and wheels onthe rear mech),i switched to a MTB mech becuase of this...

Rated maximum rear sprocket size, however, is also commonly much lower than what actually works. For instance, Shimano's models designated as "road" derailers are generally listed for a "maximum" sprocket of 27 teeth...because 27 teeth is the largest size that they make in a designated "road" cassette. However, in almost all cases, these derailers, even the short-cage models, will handle rear sprockets as large as 30 teeth in practice. (This somewhat depends on the design of the frame's derailer hanger, so once in a while you will find a particular installation where you can't use a 30, but I've never seen one where a 28 wouldn't work.

dennisn

maddog 2 wrote:

33t 110bcd rings are techincally possible but I've never seen any for sale.

Bought one a few years back. Only use in the big mountains. No problems with it.

http://sheldonbrown.com/harris/chainrings/110.html

dennis noward

John.T

You will have to forget MTB cassettes as they are only 9sp. A custom cassette 12/28 would work OK with the standard rear mech but will be pushing the chain slack take up to its limit. This will give a 32" gear as you say and should be enough for the Tourmalet. The Tourmalet from St Marie Campan does ease off at times. The first few Ks get you wondering what all the fuss was about. Then you get a few Ks at 9 or 10% followed by it easing off just before La Mongie. From here to the top the gradient varies quite a bit. I really struggled on this side a few years ago on 39/27 but rode the other side in 2006 on 34/27 with no trouble. Not easy but I was in the saddle almost all the way up. The Aspin is more of a steady climb with not much change in gradient. Sometimes on these longer climbs if you use a lower gear all that happens is you go slower and it does not seem any easier. I think 34/ 27 or 28 is about as low as you should go.

geoff_ss

I rode the Tourmalet from Luz St Saveur (ie opposite from the etape) with camping gear with a bottom gear of 36x28 IIRC and I don't think I used it. My wife did the same with a lighter load. We both fairly fit and in our 40s - I lie, on reflection, we were very fit. Not sure if it's steeper from St Mary de Campan.

I think the really hard climb will be to the finish at the ski station (Hautacam?) because, unlike normal cols, which are from the age of horse drawn traffic , it's graded for motor vehicles.

Personally, I always favour triple chain sets and a bottom gear in the low 20s when the going gets tough. You can honk up Winnat's in a highish gear but you can't do that for 10/15 miles over a continental pass. Look at how Armstrong climbs. He sat sat spun a (relatively) low gear when Ulrich was heaving and pushing a higher gear and getting dropped.

Geoff

willbevan

redddraggon wrote:

...you will find a particular installation where you can't use a 30, but I've never seen one where a 28 wouldn't work.

Exactly what i am getting at.... (Read the same article you have that you quoted that from)

hence worth mentioning, as they don't always change correctly as we are encouraging the chap here to get a 30, which may not work , or give bad shifts (in my short experience with road biking i have already come across this)

redddraggon

willbevan wrote:

redddraggon wrote:

...you will find a particular installation where you can't use a 30, but I've never seen one where a 28 wouldn't work.

Exactly what i am getting at.... (Read the same article you have that you quoted that from)

hence worth mentioning, as they don't always change correctly as we are encouraging the chap here to get a 30, which may not work , or give bad shifts (in my short experience with road biking i have already come across this)

redddraggon wrote:

You can get a SRAM 11-28 10 Speed Cassette.

£45

Surely 34-28 should get you up anything (at least in this country)?

I wasn't only advocating a 30T, I initially said 28T.

Piggy

Very useful thread! I have some more basic questions though...I'm doing the etape too and have been wondering about whether I have the right gears as I sometimes find myself grinding a bit much when I'm sure I should be spinning! There is probably another thread for this but how do you work out what you've already got? I know (or at least think) that the front cog has got a helpful number on it but what about the rear? Ta

John.T

Use Sheldon's gear calculator here. You can do them in Gear Inches, Meters Development or Gain Ratios. Being ancient I prefer inches. These relate to the diameter of a penny farthing wheel that would equate to the same gear.
http://sheldonbrown.com/gears/
You will need to know the number of teeth on all your chainrings and cogs.
Sheldon's site is worth bookmarking as it will answer most of the questions on here.