I’m thinking on switching my current 11spd Ultegra Di2 gears onto a forthcoming CX build and am wondering if the 32t cassette I currently run would be useable with a single ring up front?

Also, what size ring would you folk recommend?

Muchos cheers

I use a 40 11-32 with a 700/35 tyre. Fine for me but I’m not you 🙂

I’m running a 42 ring with a 32 bottom sprocket and it’s fine for the racing I do.

I use a 42 front with an 11-32 for racing and a 11-36 for general trail riding and non racing duties including road riding. Did have a 39 but found it a little low for road club rides, where the 42 is more than I could need as any speed above that I can just draft the others!

Cheers guys.

The bike will be used for cx racing – I have road bikes that I’ll keep using for the road specific stuff.

32t is the max I can use with my Ultegra 11spd Di2 so I won’t be changing that, I guess I could just change the front ring should I want to go bigger.. Unlikely as it is.

42t front then?

Be honest with yourself about your abilities – a large chunk of the front-runners in local and national level races here are using 42t fronts. Are you at that level?
There’s no point having a 42 on if you then never use the 11 and 12t sprockets but spend all your time at the lower end of the cassette.
38/11 or 40/11 is still a pretty hefty gear for faster sections or tarmac starts and finishes.

I’m not a racer but i am a data / maths geek, and assuming a tyre diam is 700 (poss a little understated depending on the size of tyre)

38/11 spinning at 120rpm would give you 55kph
38/11 at 150rpm (like a mad sprint) would be 68kph

40/11 @120 = 58kph
40/11 @150 = 71kph

I’d be tempted to make do with either of those and if you’re losing out in the race for the line then think about going bigger.

Not sure about my level tbh hence coming on here looking for advice, which has been great, so thanks everyone.

I ride with cat 3/2 riders on the road and keep up, but cx is totally new to me, so who knows!

I’ll start with a 40 and see how I go.

Thanks again

In that case, enjoy! Where will you be racing? Courses can have an influence on your decision too.

I’ll hopefully be riding the West Midlands league but I dont get back to the UK until mid October so it won’t be the full series, plus I’ve got to piece together a bike in between now and then.

Who knows.

Thanks again though everyone.

PS, anyone selling a 51/52 CX frame or complete bike!?