Got a CX bike for my daughters to race on, age 11 and 13.
Gearing is a bit high for them.
It’s 36/46 double and a 12-25 10 speed at the back.
rear mech is a 105 short cage.

The spec on the mech says tooth capacity is 33t, so I could go for a 12-30 cassette.
Anyone running a 30t sprocket on a 105 short cage? is it OK?

Don’t forget about BC gear restrictions, I think 46/12 is too big for the age categories your children are in. Why not just single ring it?

I can’t imagine they will ever use the big ring in a CX race anyway. Need to make the bottom end lower, that’s all.
A new Tiagra cassette is only £16, much cheaper than a new chainset.

I think that gear restrictions might come in to play here:
Youth C Under 12 at 1st Jan 6.05 metres 76 inch 39×14 / 42×15 / 45×16 / 48×17
Youth B Under 14 at 1st Jan 6.45 metres 80 inch 39×13 / 42×14 / 45×15 / 51×17

yes, yes, ok. Never been checked on a CX race anyway that I know of.
I will make sure that it is single ring only for the racing, and so 36*12, and will probably get a 34 ring.

My question was, will a 30t sprocket work ok with a 105 short cage mech???

“My question was, will a 30t sprocket work ok with a 105 short cage mech??? “

why didn’t you say that in the 1st place:-)

it might is the answer you are right on the edge, and accidental big – big and some cx cack might do for it.
I’d be tempted with a MTB rear mech and cassette- 9 speed mtb mech with road kit.

if you’re ditching the big ring anyway then the big/big issue disappears?

Yes, get rid of the big ring and they’ll be no issues on either front.

I thought I had, with a bit of background and then the last line of:
“Anyone running a 30t sprocket on a 105 short cage? is it OK?”

will go for it anyway, big ring will be ditched/disdabled for CX

I don’t think the gear restrictions apply in CX.

My daughter has been racing for 3 years and never been checked.

I don’t think the gear restrictions apply in CX.

My daughter has been racing for 3 years and never been checked.

what region is that in?

Central

Thanks. they do apply, somebody isn’t doing their job properly. 😀

I use a 32 tooth ring most of the time the big ring only gets used on the tarmac bit of crosses .I reckon a smaller ring than 36 would suit a child

in reality though, all the junors are running in their easiest few gears. There are no places where it is possible to churn a high gear, well not in the scottish CX series anyway