The problem with the 34 tooth is that unless you are doing some long climbs at 10mph, you'll rarely use it. If you are doing long climbs in the saddle at 12mph or above, or you are doing short climbs out of the saddle at 8 mph or above, then you can use a 42x25 as your smallest gear. You can then stay in the 42 ring up until about 20mph.