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Carbon rails question

clickshotsclickshots Posts: 91
edited February 2014 in Workshop
I have a Giant Defy 1 from 2009. I'd like to fit a new saddle and I liked the look of the Pro Turnix (hopefully it will fit me ok!), I just wasn't sure if it was compatible with my seat post. One of my friends seems to think that the rails will be a different size because they're carbon, but there doesn't seem to be any information about the rails on the website.

Any ideas if it'll fit? I have the original Giant carbon seat post.


  • BozmanBozman Posts: 2,570
    Some of the carbon rail saddles have oval rails, if your seatpost clamps top to bottom it shouldn't be an issue but I know from experience that certain seatposts require a change of clamp, Ritchey for one.
  • I'll have to find a shop I guess.
    If it doesn't fit, can anyone recommend a 30.9mm seat post that will fit carbon rails.


    should I buy a 27.2mm seat post and use an adaptor, seems like 30.9mm is a bit of an oddball size.
  • smidsysmidsy Posts: 5,273
    A giant Defy with a 30.9 seat post!!! Are you sure?
    Yellow is the new Black.
  • 100% sure.
    This is a Giant Defy 1 from 2009.
  • smidsysmidsy Posts: 5,273
    clickshots wrote:
    100% sure.
    This is a Giant Defy 1 from 2009.

    Yellow is the new Black.
  • BozmanBozman Posts: 2,570
    I think that your seatpost will be ok. If it isn't there's plenty out there that will be, Ritchey(2 bolt), 3T, Fizik Cyrano....... just Google.
  • I've ordered the saddle at my local shop, I'll see what turns up at the weekend :)
  • Right, doesn't fit :-P

    Can anyone recommend a 30.9mm seat post that's relatively lightweight and takes carbon rails? The shop has none. Seen a few advertised as being for MTB, does that make a difference? Or should I just use a shim and buy a 27.2mm?
  • smidsysmidsy Posts: 5,273
    Shims and slimmer posts look shoot and will certainly negate the weight saving of the carbon rails.
    Yellow is the new Black.
  • racingcondorracingcondor Posts: 1,434
    Presumably you have something like this -

    Looking at the head of that I can see why ovalised rails wouldn't fit.

    These look like they should work though -
  • No I had a different style post, that must be a newer design I guess.
    Anyway I managed to find a Giant post that was 30.9mm and fit (only) ovalized rails. Apparently on my new post you get different clamps, so if I go back to my old saddle I need to use my old post or get the other type clamp. So I got there in the end!

    Oh and the new post is lighter than my old carbon post, so with the saddle I took 250g off the bike, which isn't to be sniffed at :) Down to 7.5kg now which isn't bad for a large sized Aluminium Giant Defy :-P
  • Well I can completely inderstand your confusion (how many versions??)!

    Glad you got there in the end and 7.5 is a nice weight for that bike (I'd bet you could drop >100g by changing the fork as well if that's stock).
  • I should mention mine is a triple so I could probably take a bit of weight off there if I swapped to a double.
    That would be a big job though and I'm kind of lazy :-P
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