What's the best rack (over rear tire mount) out there for a 700C road bike?

Planet Bike's looks nice...

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If your bike has threaded eyelets, then Blackburn expedition, or various copycats are good.

Seconded. My first Expedition was a trash-heap salvage in perfect condition but sans mounting rails - I called Blackburn, and they were good enough to send me a set of mounting hardware for it free of charge! With service like that, I'd buy their products even if I didn't like the rack as much as I do!

-chris

Since road bikes often have shortish chainstays, you need to consider what kind of heel clearance you'll get with panniers. If this is a concern, check out JandD's Expedition Rack. It has some extra length that let's you slide the panniers back farther.

Using small panniers will solve the heel clearance issue. Also, make sure you get ones with a heel cutout.
Panniers with the Rixen and Kaul clip-on fittings have an extruded rail, so you can position the hooks wherever you like. You can slide the bag back if you need. Carradice use this type of mounting system.

I have a Tubus Fly Rack - its for 700c, very light, only really takes panniers though -- if you want to put something on top, you might need to fashion your own deck and stabalizers... but otherwise its nifty... a little pricey though - secures to eyelets and to the brake bridge (same bolt as the caliper brake)

Topeak - I like the track system they have.

I second Topeak. Can remove it in a second with their rack system and bag expands as necessary to become a racktrunk and pannier. Great system. I love mine.

Hi,
the Planet Bike rack works just like the other racks. It's both lighter and cheaper.
It's not as rugged; but I have used even lighter racks for years with no problem.
If you are going on expedition tours; by all means get an expedition rack. Me, I like light and cheap. 3 of our 4 bikes have the Planet Bike rack so we can swap panniers. The fourth one is even lighter, and less rugged. I have had almost everyhing on a bike die on me. Frames brake, stuff wears out. Never had a busted rack. A decade ago I was using a cheap wimpy (but very light) Nashbar rack. I managed to lose their odd mounting hardware; but they are still kicking around,
ready to go if I ever figure out a way to use them.

Agreed... except as soon as you decide you'd like to hang the boxy "grocery bag" panniers, suddenly your heel clearance is gone. Heel strikes that knock off your load of bananas, eggs, milk, bread, bologna and pop-tarts in the middle of a busy intersection make for a great deal of panic and embarassment.

I guess it all depends on the intended use. If you're planning to carry groceries (which I don't think I would) then it'll pay to buy a sturdy rack. But if it's just a light pack that you don't want to carry on your back then light makes sense.
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