Ultegra cassette choice

[Harleyboy]

Evening,
I have recently gone from a bike with a compact chainset and 10 speed 11-32 cassette (all Tiagra). It was good on hills! My new bike has a semi compact chainset and 11-30 cassette which loses some climbing ability. Ive only had the bike 3 weeks and done about 300 miles of mixed riding. I haven’t noticed an issue on hills so far but have some sportives planned with big climbs and a race in Marrakesh later this year which has 30km uphill so would like the comfort of an extra gear or two in reserve!

To the question! Am i right in thinking I would need to switch to an 11-34 rear cassette to maintain the same low gearing as my old bike? I would like to keep the higher front gearing.

I think i would need to change the cassette, the rear cage to a longer one and a new chain. Pricey but I knew the gearing wasn’t ideal when I bought the (used) bike. Anyone done this?

Thanks

[leyorkie]

I’ve got the Ultegra 11-34 on my bike with a 105 mech. I did not have to touch the rear mech. I’ve changed both my bikes as I find the spacing more useable for me even at the top end
Standard is 11,12,13,14,16,18,20,22,25,28,32. The ultegra is spread more even.
11,13,15,17,19,21,23,25,27,30,34.
I’m not racing so cadence is not important to me but when I change down a gear I want it to be easier.

[CoupeKid]

I’ve got a similar dilemma but am too tight to change the rear mech.

Have you considered using a rear mech extender? They only cost a couple of quid and drop the mech by a couple of centimetres. It’s the equivalent of buying a longer cage mech.

Jon Cannings on GCN Tech advocates for them.

I haven’t gone this route yet but probably will soon.

[Akz]

I wouldn't bother splashing out for an Ultegra cassette since the prices have gone up over the last few years. 105 will work just as well and is only a few grams more.

[Gilhooligan]

I put an 11-34t cassette on my bike which came standard with an 11-30t. The bike shop said I didn’t need a new longer cage derailleur. They did warn not to cross the chain though. The derailleur needed a bit of adjustment on the B screw and that was it. I believe manufacturers are a bit conservative when stating which length of cage is required.

[louiebaby]

For a nerdy person, the following is pretty handy for working out what difference the changes will make.

Don't forget that the wheel and tyre size will play a (probably very small) difference in proceedings too.

It's worth considering the frame as well, but only because the stiffness of the frame when comparing an old bike to a new one. If the new bike transmits the power more efficiently, you'll find it easier to turn the same gear on the same hill.

[Jimbo.]

louiebaby said:

For a nerdy person, the following is pretty handy for working out what difference the changes will make.

Don't forget that the wheel and tyre size will play a (probably very small) difference in proceedings too.

It's worth considering the frame as well, but only because the stiffness of the frame when comparing an old bike to a new one. If the new bike transmits the power more efficiently, you'll find it easier to turn the same gear on the same hill.

Only if you’re riding a bike made from wet spaghetti.

Manufacturers are not conservative re cage sizes and cassettes. If you cross chain and it fks itself halfway up the Galibier then don’t blame Shimano.

[Gilhooligan]

Jimbo. said:

Only if you’re riding a bike made from wet spaghetti.

Manufacturers are not conservative re cage sizes and cassettes. If you cross chain and it fks itself halfway up the Galibier then don’t blame Shimano.

Conservative probably the wrong word choice. What I was getting at is that they obviously have to account for scenarios where people will ride on the two biggest gears. Whereas if you refrain from doing that you can get away with retaining the smaller cage derailleur with the larger cassette.

[Jimbo.]

And after all day in the heat and hills when you’re absolutely fecked, can you be 100% sure you won’t accidentally cross-chain? Human factors and all that...

[Gilhooligan]

I’ve happily rode my bike with that setup for 3 years now. Obviously can’t speak for everyone though. I guess it boils down to an increased risk of giving yourself a mechanical if you’re not paying attention vs spending a lot more (comparitively) on new parts.

Longer cages look rubbish on a roadbike too

[Harleyboy]

thanks everyone, I've heard of the brackets that drop the mech down so might look at those. The bike has Di2 with synchro shifting so unless that fails, cross chaining should never happen....

Seems I can get an Ultegra 11-34 cassette for about £65 which doesn't seem too bad.

I hadn't considered the aesthetics of a longer mech - how much longer are they?

[millen]

Any thoughts on the ZTTO ultra light series? Eg SLR 11-34 is a claimed 228g against nearly 350g for my Shimano HG800.
One review I saw claimed the back plate was chocolate but that was an early version and and it's questionable whether the dude had installed it properly. I'm a featherweight so durability shouldn't be a big issue for me...
https://www.ebay.co.uk/itm/ZTTO-SLR-Cassette-11Spe...
Don't forget, there may be extra customs duty.

[ChrisMCoupe]

Harleyboy said:

Seems I can get an Ultegra 11-34 cassette for about £65 which doesn't seem too bad.

If you use a website which sounds an awful lot like Jiggle, you can get one nearer £50 I'm sure.

[Usget]

Harleyboy said:

To the question! Am i right in thinking I would need to switch to an 11-34 rear cassette to maintain the same low gearing as my old bike? I would like to keep the higher front gearing.

Assuming all other factors remain the same, gearing is just a ratio, so you can compare like-for-like by dividing front by back. Lower numbers are better. 34/32 = 1.0625, 36/34 = 1.0588, which is about as close to identical as you could get.

You want a Wolf Tooth Roadlink for your rear derailleur to move the jockey wheels further from the cassette teeth and therefore accommodate a larger sprocket. Or splash out on a 6870GS rear derailleur, but even that is only rated to 32T (it would probably be fine with 34T in practice).

Shimano do tend to be conservative, as other posters have said - I run a stock medium cage R7000GS with a 36T largest rear sprocket, with no difficulties at all. But I don't know if I'd be gambling a £200 magic robot mech on that theory.

[lufbramatt]

The 105 one can be had for £35. Suppose it depends if its worth the extra £15 for a 25g weight saving.

[gazza285]

Have you considered trying a bit harder? Going a bit faster?