The bike my son rides the gears are too high, so I would like to lower it. So what options do I have. Its a Dawes Rocket with 3 piece crank 40t chainring crank arms are about 140mm and 6 speed 14-28 cassette.
Will it be normal sqaure taper ?
So has anyone done this or do you know what works ?
Cheap is also a key word.
Thanks Si

I've been looking at kids bikes in the last few days for my son & have seen the shimano mega range freewheels.
I can't see so many online for 6 speed (and have no idea about compatability) but maybe if you have a net search you can find something along these lines….

http://www.dotbike.com/ProductsP5570.aspx

yes that looks an option but my God its quite a jump up into first.

40/28 is a huge gear for kids bike, I'm not surprised he has problems. Check out Sheldon's gear calculator and compare his to your bike to get a feel for it.
My daughters 20" wheel bike was 36/28 and that was too much. Last week I put 32 on the front ,and it's much better. It dropped lowest gear from 26" to 23" and really helped her a lot on the steep hills round here.

mountaincarrot how did you do that ? the cranks are a bit funny on ours ?

Hi Blastit.

I have an Islabike Beinn with square taper cranks. Chainring is rivet/press fit to the crank, but it was easy for me to get a 32T crank+chainring from Islabikes to replace the existing 36T. Crank arms in my case are 127mm.

Rgds

I've put a mega range freewheel onto our kids bikes. The std rear mech coped fine. It looks a big jump from 1st to 2nd but worked well. The std ratios supplied are totally unsuitable – except on Isla bikes.

Just done a bit of a bodge, split old cassette to remove 32t sprocket and then bolted it to the 40t ring already on. Had to also put on old front mech to keep the chain on. Have to wait till weekend to see if it works .
If not I will try the mega 34t rear cassette.
Thanks for your comments.