Commuting - rear rack advice for comfort bike

New to bike commuting and new around here - forgive me for any breach of ettiquette. I'm looking to start a 3-4 mile-each-way commute with a 2008 Specialized Expedition Sport and want to outfit it with a rear rack and basket/panniers that would allow me to stop off at the grocery on the way home. Given the non-standard frame geometry can anyone suggest a particular rack that will work best? I'd appreciate any advice.

If your bike has braze-ons at the rear drop-outs, but the seat stays are the problem. . .

There are some racks that attach to the seatpost ONLY, but that shifts your center of gravity up and they don't carry much weight, either -- this type: http://www.bikeparts.com/search_results.asp?ID=BPC306030.

I saw this device: http://www.bikeparts.com/search_results.asp?ID=BPC306017 but at the time it was about $15 or $18 or some such, so I figured that I could cobble together something similar, and did so. With this type of a gadget, any rack will work. Ran me about $4 for my home-built version.

Can use full panniers, not just a "trunk" and the center of gravity remains nearer the hub.

From the pic on Specialized web site it looks like there are rack mounts on the seatstays? If there are holes on the dropouts for them as well then you should be able to use any standard rack!

Most specialized do have full rack braze-ons and you should use them if provided.
The gold standard for everyday commuting/shopping racks is set by Blackburn, these are strong, light and very stiff. Flex is a bad thing when heavily loaded. I have a knock-off copy of a Blackburn (as well as the genuine one) that is excellent.
Mount it level, not too high above the rear wheel and as far forward as your pannierbags will allow.
One really useful modern feature of racks is a rear lamp bracket.

New to bike commuting and new around here - forgive me for any breach of ettiquette. I'm looking to start a 3-4 mile-each-way commute with a 2008 Specialized Expedition Sport and want to outfit it with a rear rack and basket/panniers that would allow me to stop off at the grocery on the way home. Given the non-standard frame geometry can anyone suggest a particular rack that will work best? I'd appreciate any advice.
I'll echo what iBRAD says. Looks like you can use a standard rack, since you have eyelets in the dropouts. Here's the web site: http://www.specialized.com/bc/SBCBkModel.jsp?spid=22031 The one issue may be that the saddle on this bike appears to be VERY low... you may need extra-long hardware to attach the top of the rack "downward" onto the seat stays, which any bike shop should be able to get for a few bucks.

I suggest one of the wire frame racks, since they are slightly lighter and often easier to attach things to than the ones with platforms... but it's mostly a personal preference. Nashbar has always had quite a good rack selection. Here's one with a rear light bracket for only $10: http://www.nashbar.com/profile.cfm?category=6000112&subcategory=60001079&brand=&sku=20205&storetype=&estoreid=&pagename=Shop%20by%20Subcat%3A%20Racks
I have an ascent rack that is nearly identical and quite sturdy, except doesn't have the light, and I paid twice as much cause it wasn't on sale :)

But, basically, you should be able to use a standard rack, with just a little adjustment or replacing of the struts that attach the front of the rack to the seat stays.

It does look like there are mounts on the seat stays, so most any rack should work.

Blackburns are very good.

You can bend the seat stay mounts (they are usually something like this. . .: http://www.bikeparts.com/search_results.asp?ID=BPC102198

without affecting the carrying ability (much) since the weight is pretty well all at the hub.

I see your concern with the geometry of the frame though. Might ask the shop where you got the bike what they recommend.

It does look like there are mounts on the seat stays, so most any rack should work.

Blackburns are very good.

You can bend the seat stay mounts (they are usually something like this. . .: http://www.bikeparts.com/search_results.asp?ID=BPC102198

without affecting the carrying ability (much) since the weight is pretty well all at the hub.

I see your concern with the geometry of the frame though. Might ask the shop where you got the bike what they recommend.

I'd suggest Delta Megarack Universal (http://www.deltacycle.com/product.php?g=24) over the Blackburn. It's adjustable to fit different frame configurations.

Thanks for the inputs. I guess my concern was the location of the seat stay brazeons. Since they're a fair bit lower than the top of the wheel I wasn't sure how to level the rack. Looking at the extender brackets I feel kind of dumb now. I worried that angling the seat stay mounts would really hurt the carrying capacity, but it makes sense that most of the weight will be on the hub (thanks for the physics refresher). Anyway, as I said I'm new to the game so I'll just keep learning as I go. Thanks again.

Thanks for the inputs. I guess my concern was the location of the seat stay brazeons. Since they're a fair bit lower than the top of the wheel I wasn't sure how to level the rack. Looking at the extender brackets I feel kind of dumb now. I worried that angling the seat stay mounts would really hurt the carrying capacity, but it makes sense that most of the weight will be on the hub (thanks for the physics refresher). Anyway, as I said I'm new to the game so I'll just keep learning as I go. Thanks again.

The main purpose of the seat stay brackets is to BALANCE the rack, rather than to support the weight... I have seen a couple of ridiculously weak jerry-rigged setups used to hold the rack to the seat stays, with no problems.

Good luck!