I'm having a really hard time believing ANY bike made in 2012 has a threaded on freewheel. the bike in question is http://www.diamondback.com/2012-clarity-1 .... that page says...


[TABLE="class: specs_geometry, width: 604"]
[TR="bgcolor: transparent"]
[TH="bgcolor: transparent"]Gear[/TH]
[TD="bgcolor: transparent"]Shimano 7spd Freewheel (14-28t)
[/TD]
[/TR]
[TR="bgcolor: transparent"]
[TH="bgcolor: transparent"]Hubset[/TH]
[TD="bgcolor: transparent"](F) 32h Alloy QR (R) 32h Alloy QR Cassette
[/TD]
[/TR]
[/TABLE]


well, ONE of those has to be wrong, you can't put a freewheel on a cassette pub. Shimano hasn't made threaded on freewheels in close to 20 years, I bet its a cassette. you'll need to stick with a 7 speed, or get a new shifters (and those EF51 are integrated brake+shifter). the derailleur can handle 8 speed fine.