I'll have to look to be sure, but IIRC my Nexus7 bike is using a 45 or 46 front with the 21 rear and that gives me gear inch range of about 40 into the 80's? They do make a 23 rear cog, but paired with a 52 front is still not going to give you very low gearing. Depends on your terrain I guess.
Edit: running a quick test using sheldon's calc, I think I'm using 46x21 with a range of 37.6 to 92gi.(700x35 tires)
Using a 52x23 wouldn't change it that much, so you'd be OK.
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Last edited by Ex Pres; 07-25-11 at 10:43 AM.