Hi all, coming off a 3×10 26″ bike to a 1×11 650b bike I’m struggling to decide on a chainring/cassette combo.

Was thinking either 11-42 with a 30t up front or maybe 11-46 with 32.

Bike will be used mostly for peaks riding and although I have some fitness I’m also slightly heavier than your average mtb rider due to a decade of heavy weight lifitng in my 20s.

Any help choosing what to go for would be much appreciated.

Start with this, but basically front/rear gives you the ratio.
Work out what you use now and match about that
http://gears.mtbcrosscountry.com/#26I1I1
Slightly more complex version making some wheel size adjustments

In the end it’s really personal

Thanks for that,

Had penned some similar calculations, was thinking the 650b vs 26 makes the ratios feel slightly harder thought right? For one revolution of the wheel you go slightly further so it’s more effort for the same gearing.

Anyone know the circumference of a 26 wheel and a 650b wheel with tyres on? Could factor a % in then

depends on the specific tyres chilled – with some large height 26″/small height 650b there’s virtually no difference.

tbh, I don;t think your legs will notice a huge difference if you match your current ‘climbing’ gear on your existing bike on a 650b

One other question.. Can you get away with medium cage mechs for an 11-46t cassette?

If you’re strong in off-the-bike terms [heavy weights], plus a bit heavier, then a bigger gearset is in order IME. Need to get the show on the road, not spin a 30t gear like a wee man.
The Peak doesn’t have a lot of sharp climbs, in general, so you should get up everything regardless. It can crush you with cumulative climbing, right enough, so also depends how long you like to go out for.

Tends to be 4-5 hour rides in the peaks, mix of long draggy climbs and the occasional short sharp one.

I’m thinking 32t with 11-46 at the minute, however I really don’t like the look of a dinner plate on the back so may go 11-42t and just man-up!

It’s about 1.5 tooth difference on the front between 26 and 27.5 – I certainly noticed it and went down from a 34t to a 32t, having swapped the same drivetrain to a bigger wheeled bike. If anything 27.5 tyres tend to be bigger volume than 26 (look at a Minion DHF 26 x 2.35 vs a 27.5 x 2.3).

If you’re going 1×11 I’d go SRAM or one of the other cassettes that gives you a 10t smallest sprocket – that makes a big difference.

Need a new freehub if I go SRAM 🙁 also In my personal experience I find it wears out quicker than shimano kit.

Can anyone answer the question about mech length? Can you use a medium cage with a 11-46t cassette?

Once you have the freehub that’s it, out of my ride group sram is easily out lasting shimano 11 and doesn’t weigh anywhere near as much.

I’ve seen a recommendation to use the 11spd derailleur to cope with the 11-46 but no personal experience either of the cassette or derailleur.

I run with an 11-36 (and 40T expander) with either 30T or 32T chainring on a 29er and it’s fine for the Dales and Peak.

this, 11-42 with a 30t
Depending on fitness/weight you might even go 28t up front.

Because – the inner ring (40t) is made of aluminium so if your big’ing it up front and climbing on the 40t ring it will wear out quickly.

Go for a front ring that gives you a good chain line ie straight for most of your riding, experiment. Changing the ring is 2 min job.

From what you said about weight and fitness Id start with a 28t

Anyone know of any good deals on sram groupsets? Shimano ones are peanuts at the min on CRC, was just going to buy an XT 1×11 set up.

Thanks for all the info so far

I am used to riding 2×9. A year ago I moved to 1×11 on my hard tail. I went for 30T and 11-42. It’s absolutely fine at trail centres etc, but my local trail is a long steep climb with some very steep sections. If I’m off the bike for a while for any reason, or just more tired than usual, the 30 – 42 kills me. It’s definitely doable, but feels like you’re in gear 3 on my older bikes.

So, when I went 1×11 on my Blur recently, I went 11-46 with a 30T at the front. Again, at a trail centre, I would never need the lowest gear, but it’s excellent on my local trails.

If you never use the lowest gear on your current bike then I would guess that 30t &11-42 would be just fine. If you find yourself using your lowest gear a lot, like I do, then I recommend the 11-46.

Cheers for all the info guys.

Been looking and it appears the sram cranksets are hard to mate up with BB92 so I’m going to stick with shimano for ease of replacing bb’s in the alps etc.

Johne, are you using a long or medium cage mech with the 46t?