-1 tooth on the front sprocket will increase acceleration and reduce top speed significantly more than changing the rear sprocket by 1 tooth. Think of it this way....with 16 tooth front sprocket each revolution will move the chain 16 links and, if you had a 32 tooth rear sprocket 2 revolutions of the front sprocket would equal 1 revolution of the rear wheel. Reducing the front sprocket to 15 teeth will mean that 2 revolutions of the front sprocket will equal 30/32 revolutions of the rear wheel. So, the front sprocket, and hence the engine, will need to revolve more to cover the same ground.......more revs for same distance covered.....