Alps gearing-Compact or bigger cassette.

chaffordred

Hi, I have entered La Marmotte in July and wondered if anyone had any advice on getting gear ratios right.

Been to the alps twice before and done century rides on compact (50/34) / 11-27 cassette set up.

I now have a crank based power meter (53/39) and would like to use that instead of the compact, but switch to a 12-30 cassette.

My question is would fitting a 30 cassette on standard chainrings be comparable to the 34/27 set up?

k-dog

34/27 is 33.1 gear inches and 39/30 is slightly harder at 34.2.

That's about equivalent to losing 1.5 teeth from your biggest cog on your 34/27 - so if last time you were happy in the second biggest (probably 24 or 25?) then you'd manage, but if you were in the 27 then using your standard chainset would be harder than that.

Personally I'd be using the compact and the 30 cassette!

jgsi

Semi compact to fit presuming 130bcd? 52/36.
The thought of doing Alp with 53/39 would scare me as you are really these days not supposed to use amphetemines any more to dull the pain.

First.Aspect

Get yourself an aftermarket 38T/130bcd inner.

http://www.wiggle.co.uk/ta-130-pcd-aliz ... 60206596uk

That would get you very close to the same lowest gear as a 34/27.

You could also use a medium or long cage deraileur. Shimano's med cage mechs take up to 32T for example. A 38/32 is actually a slightly shorter gear than a 34/28. Have a play on here: http://cycleseven.org/bicycle-gear-inch-calculator (longer gear inches = harder to pedal)

Only you know what's enough for you. But be realistic. 160k with your mates is likely to go easier than 170k riding with faster people you don't know. And there WILL be faster people and you WILL be drawn into hanging on to a fast group for as long as you can!!

When you get to the final couple of climbs and you've been dropped, your only company will be people walking their bikes up or grinding up at a cadence of 60, at which point you'll be glad of every fraction of a gear inch.

First.Aspect

JGSI wrote:

Semi compact to fit presuming 130bcd? 52/36.

Not possible, unfortunately. Anything below 38 is only possible for 110bcd or the new 4 bolt standard.

chaffordred

Thanks for the advice and good call on the 38 chainring. I didn't know they existed. I'm not sure a 32T would work with a 10sp DA Di2 rear mech though?

I did a century ride in the Alps last year on a compact and 27T. For the last climb I was in the 27T, but since then I have definitely got stronger, particularly on hills. My weak point is endurance and feeding on the bike-Anything over 4 Hrs and I start to suffer, but I intend to sort this out in the weeks leading up to the marmotte. The last couple of weekends I've been going out doing 4hr+ rides and stopping to eat.

One of the reasons why I wanted to keep the 53/39 was to keep a check on my power to make sure I don't get caught up in the moment, go mad and overcook myself on the first couple of climbs.

Right now I see my options are:

1. 53/38 (change inner ring) with crank power meter and 11-28 or 12-30 ultegra cassette.
2. 50/34 compact with 11-28 ultegra or 11-27 DA cassette and monitor HR instead of power.
3. 50/34 compact and 11-28 ultegra and buy stages crank arm, then ebay stages after event. (maybe take a £100 loss)
4. 53/39 crank power meter and try and squeeze a 32T on the back.
5. MTFU, train really hard and go with 39/27!

Cheers.

sheffsimon

chaffordred wrote:

Hi, I have entered La Marmotte in July and wondered if anyone had any advice on getting gear ratios right.

Been to the alps twice before and done century rides on compact (50/34) / 11-27 cassette set up.

I now have a crank based power meter (53/39) and would like to use that instead of the compact, but switch to a 12-30 cassette.

My question is would fitting a 30 cassette on standard chainrings be comparable to the 34/27 set up?

I used 53-39 and a 13-29 (Campag) cassette in the alps and rode up all the marmotte climbs on it. Didn't use the 29 much at all, top of Galibier I think, and that first ramp up the Alpe.

I must be more awesome than I thought

peat

blam a 12-30 on the back. Just remember not to use the big cog in training. Save it for when your are about to cry halfway up an Alp.

chaffordred

Peat wrote:

blam a 12-30 on the back. Just remember not to use the big cog in training. Save it for when your are about to cry halfway up an Alp.

I think this may be the way to go or as First Aspect suggested fit a 32T.

Doing a bit of research and some people have had success fitting a 11-32T Shimano 10 sp. XT cassette. Apparently the rear mech cage can be swapped for a longer Ultegra version and this seems to work well with the Di2 rear mech.

markhewitt1978

chaffordred wrote:

Hi, I have entered La Marmotte in July and wondered if anyone had any advice on getting gear ratios right.

Been to the alps twice before and done century rides on compact (50/34) / 11-27 cassette set up.

I now have a crank based power meter (53/39) and would like to use that instead of the compact, but switch to a 12-30 cassette.

My question is would fitting a 30 cassette on standard chainrings be comparable to the 34/27 set up?

It's easy to work out, you just divide front by back (no need to do inches on the same bike)

34/27 = 1.25
39/30 = 1.30

So there, the 30T ring on the double will be a little bit higher but not massively so.

If you were to fit a 32 (as said you may need a new rear mech), then;

39/32 = 1.21 - which is lower than you had with the compact, happy days.

turkeytickler

You can get a 12/30 ultegra cassette - presumably that would work out of the box with Dura Ace?

dgunthor

yes, any same speed shimano cassette will work fine.

i'd skip the power meter and use the 34-30 as someone else stated. i used 34-30 to get up alpe dhuez, marmotte has about 5 big climbs, i'd be grateful of easy gears for it

markhewitt1978

turkeytickler wrote:

You can get a 12/30 ultegra cassette - presumably that would work out of the box with Dura Ace?

Yup, I use Tiagra 12/30 which would also work just as well, and rather cheaper too if you're just trying it out - £12 on Wiggle.

turkeytickler

I know the spacing is compatible across same speed mechs/cassettes but I'm not 100% sure the dura ace mech has the same range as ultegra (i.e. whether it will take a 30T sprocket) not sure it doesnt either - just prob worth a quick check (which I could have done in the time it took to write this doh!)

DeVlaeminck

It all depends on how strong you are and what kind of time you are aiming at in the Marmotte. Strong riders/good climbers can suit a standard double especially with a 30 sprocket. For some 34*30 would be overkill even for the Alpe at the end of the day - others would be grateful for it - depends on you really.

chaffordred

DeVlaeminck wrote:

It all depends on how strong you are and what kind of time you are aiming at in the Marmotte. Strong riders/good climbers can suit a standard double especially with a 30 sprocket. For some 34*30 would be overkill even for the Alpe at the end of the day - others would be grateful for it - depends on you really.

I'm a fairly strong rider, but suffer on the 4+hr rides which I'm now sorting out. Aiming to do the Marmotte in around 8:30. Hopefully less. I've done quite a few Alps climbs on a 34-27 and not had a problem. But hitting the Alpe with 100 miles in my legs is whole new ball game and uncharted territory for me :?

chaffordred

turkeytickler wrote:

I know the spacing is compatible across same speed mechs/cassettes but I'm not 100% sure the dura ace mech has the same range as ultegra (i.e. whether it will take a 30T sprocket) not sure it doesnt either - just prob worth a quick check (which I could have done in the time it took to write this doh!)

After doing a bit of research I found the long cage from a Ultegra RD is supposed to be a straight swap with the DA RD short cage and then it's supposed to be able to accept up to 32T. Shimano does a 32T XT MTB rear mech that's supposed to be compatible.