Well i dont think the ride hieght will change, nothing you could notice, and if your changing sprockets its best to do both and a new chain, now i might add that it is preffered to change chain with sprockets not required if the sprockets are ok. As to the length i can only say i run the 17 tooth around the city and for the long trips i swap back to the 18, mind you it is a new 18 not the original, of course with the change back (2nd time) i have not changed the chain and have been running the same chain length, it has shortened the wheel base from the original 18 tooth front, but i kinda like it a little shorter, gives me more weight over it and the front gives more feed back, but thats just me, not saying its right.