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  1. #1
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    GT Marathon Team - Sizing (help please!)

    Hello,

    I've ridden a 1996 GT Avalanche for the last ... 12 years. It was a size "medium" then. It seems that GT has introduced new sizes over the years...and I need some advice.

    I just purchased a 2008 GT Marathon Team in medium... but I'm not 100% sure this was the right choice.

    There is no way for me to test ride one of these locally so I hope that somebody out there can give me some advice quickly.

    Geometry and specs are here:
    http://www.gtbicycles.com/usa/eng/de...ry&&id=20#2608
    (click the 'Geometry link')

    I'm about 5'6 and 1/2" tall (probably a bit over 5'7" with my shoes on)
    My inseem is about 29"

    This will be my first full suspension bike. I would rather it have a tight feel than "ride big". I also don't want a bike that's too small, obviously. I would've selected the medium by default, but then I noticed that they were selling XS frames... so I'm not sure which to choose.. M or S.

    I read on the forums about guys 5'7" to 5'10" riding medium sized iDrives... so that had me worried that this bike may be a little too big for me. Maybe not -- I'm not 100% sure how much different sizing on a full suspension rig compares to a hardtail.

    Please respond ASAP! Your thoughts are appreciated.

    Thank you,
    Adam
    Last edited by m1neral; 03-14-2008 at 11:53 PM.

  2. #2
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    Dude i'm 5"7. all my bikes so far be it HTs or sussers have been size small, including a GT zaskar. assuming you're into all-mountain and XC, you should be looking at seat tubes closer to 16" ct-top and 14" ct-ct. also a horizontal top tube closer to 22" / 559mm and no more than 22.75" for XC.

    i can safely say the M size cockpit will be a little too stretched. Also for yr bike's intended purpose, you will benefit from a better crotch clearance of a S size.

    judging by GT's specs and yr requirement, my money's on S size. for a bike this expensive you really don't want to make any mistake. demand a test ride from your shop to compare. your stem for xc riding shd be 90mm-110mm.

    Also, your geometry for xc HT is not much different from a xc susser. the basic cockpit and seat tube etc are still the same. it's only when you go for bigger rear travel rigs (5" and above) that you start to really deviate.
    Last edited by sparst; 03-15-2008 at 12:59 AM.

  3. #3
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    Thanks for the reply.

    There really isn't any way to test ride this bike -- no shop around here has one in stock. The closest I can get is a 2008 GT Zaskar Pro ...but even those numbers differ from the Marathon geometry.

    What year is your Zaskar? My 'medium' 1996 Avalanche fits just fine. I beleive back then a medium was considered a 17" frame. These days, it seems a medium is closer to 18".

    Is there any chance you can post a picture or two of your small frames? I'd love to check out the difference.

    Thanks
    Adam

  4. #4
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    I think the sizes are close enough to not worry about it. If you get a medium, you might need a shorter stem. If you get a small, you might need a longer stem. The shorter stem medium is probably gonna handle better than the long stem small.

    I think there's a pretty good chance neither size is 'perfect' but I would worry about your knees hitting the bars on the small, while the medium will actually handle even better if it's a little too big and you put on the shorter stem.

    Since you already bought it, quit worrying about it and be pumped you bought a super sick bike.

  5. #5
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    Thanks man. I should stop my worrying. I'm looking forward to my new ride.

  6. #6
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    M1neral I'm about your height and I think the M would be a bit stretched, to be honest. The M is over 23.5" in the TT which is pretty long. I normally run around a 22" TT with a 100mm stem and flat bars and that fits me pretty well. One of my mates sells GT and I've seen that bike in the flesh and they are pretty stretched and also quite high in the the standover department as well. All the XC FS bikes are longer in the TT than the Avalanche series, and have been for a few years now.
    My Cannondale Lefty keeps failing....

  7. #7
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    Quote Originally Posted by Sideknob
    M1neral I'm about your height and I think the M would be a bit stretched, to be honest. The M is over 23.5" in the TT which is pretty long. I normally run around a 22" TT with a 100mm stem and flat bars and that fits me pretty well. One of my mates sells GT and I've seen that bike in the flesh and they are pretty stretched and also quite high in the the standover department as well. All the XC FS bikes are longer in the TT than the Avalanche series, and have been for a few years now.
    Hey! I'm running the same setup, 22"-ish TT with 100mm stem with flat bars. i find it to be the perfect balance between speed and control.

    as for m1neral's reference to his old geometry, here's my opinion: i had a 17.5" frame with a 13.5" ct-ct. 17.5" on paper is too big for me, but 13.5" is perfect. So i had a usable frame albeit having a shorter seatpost. But what made me sell the frame was the 23" TT which i found too stretched even with a shorter 90mm stem. So my point is: the numbers that really matter are the ct-ct (that decides the crotch clearance) and the horizontal TT (that decides the cockpit). That is assuming the other measurements( HA,SA,WB, BB height etc) are average industry standards. So a Giant size S frame with 22.8" TT will actually be closer to a Spesh size M frame with 23" TT.

  8. #8
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    Thanks guys. Looks like I can change the order to a small before it ships. I went to a LBS today and test rode a similar GT FS model... small felt good.

  9. #9
    No good in rock gardens..
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    FWIW my last bike was a M Avalanche with a 100mm stem and it fitted fine - as I said though the FS bikes are longer. A friend has a M I Drive 4 with a 120mm stem and riser bar (the backsweep of which seems to take a little length off) and it feels like a skyscraper after my HT - the extra BB height is very noticeable and I have next to no gonad clearance.

    One thing I noticed with the Marathon Team is that it uses a zero setback post - this can put you a little further forward than is ideal if the length is borderline, but it also makes it easy to pick up extra length if need be by swapping to one with setback.

    That Marathon is going to be a nice bike! My pal has sold a couple, as well as the carbon Zaskars and they are both very trick. GT is turning out some nice bikes for great $$$.
    My Cannondale Lefty keeps failing....

  10. #10
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    Little difference in size

    I'm about 5-10 1/2 and have been riding a size L. It is a bit stretched for me, but a is less than 1/2 inch shorter in the tt length. I barely have enough clearance in the inseam, but I love the ride of this bike so much. I'll probably stick with an L and just shorten the stem or get some more swept back bars.


    BTW I've tested about 6 different full suspension XC bikes and I'm consistently 1 mph faster on my local single track track trail on this bike. I've ridden them all almost twice on the same trail. 1 mph doesn't sound like a lot but that translates to a pace almost 50 seconds faster per mile! Thats huge in XC. This bike is just plain fast and comfortable.

    My guess is that you are like me-a tweener. I am probably a ML but since they don't make that and my LBS doesn't and won't have a M to ride I'll just have to go with my gut feeling.

    Good luck, either way this bike will rock.

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