Hi Stew72,
You shouldn’t have a problem if you fit a 2 tooth larger outer ring. It depends how accurately set up the bike was to begin with. On a new bike the chain is adjusted in length so that it JUST fits between the largest chainring at the front and the largest sprocket at the back, with a little bit of slack to allow for the gear change.
If you decide that you want to change to a larger chainring DO NOT use the gear that uses the large chainring and the large sprocket until you have checked, (off the bike!), that the ratio will work. Incidentally, this gear is not a gear that you should be using, but we all make mistakes!, as it tends to put the chain under too much sideways pressure and leads to early wear on the chain.
Regards
Incognito1
