b0rderline

After a long research I have finally decided to pull the trigger and buy the GT Grade Carbon 105. I was very interested in this bike from the moment I have tried the ALU version but I was afraid of the limited tire clearance. But it looks like the front can take Schwalbe G-one 40c tire. The rear clearance is more limited but I will try to put 40c there, if not, then I will have wider tire at the front and 35c in the back (combined with great rear compliance the comfort should be very good). 

The last question is about the size. I have come across a great offer for 2016 model (nearly 20% discount) so I simply can't wait till march to try different sizes and I have to decide now which will be best for me. I have tried L size and it felt slightly too big (it has 565 cm TT lenght). The feeling of big comes I think from the fact that the stem on Grade is unusually long (120 cm) where other gravel bikes with 565 TT lenght uses 100 mm stem. So I think that changing the stem for a 100 mm should do the trick but I don't know how this will affect the bike handling. Grade has a long headtube which already shifts some of the weight to the back. If I additionally make the stem shorter, then the front can start to be loose and twitchy. So maybe I should go with shorter frame M size (550cm TT) to avoid that. But I have tried bikes with that short TT and I felt cramped on them.

I am 179 cm tall and my inseam is 83 cm which makes me kinda in between M and L sizes so I have to decide which will be better, especially on gravel roads where I want to spent at least 50% of my rides.

Can You help me decide what size I shoud buy?

Thanks!

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stabbedintheface
I found the sizing listed on GTs site to be very accurate
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b0rderline
Where did You find this sizing? I can't find it.
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knl2stl
I am a little taller than you with inseam about the same.  Are you sure the stem on the large is 120?  That seems long.  The M has a pretty short reach.

I have a 2014 Kona Rove with TT of 565 and reach of 383.  Same HT and ST angles as the 56 (L) Grade.  I have a 90mm stem on it.  For sometime I felt like I needed a longer stem, but I come from a very stretched out xc and road background.  I just changed a 120 stem with 600mm bars on an xc race bike to 90 and 725.  It did not make the handling twitchy at all unless I am really low in a sharp turn already close to jack knifing, and that is probably due more to the wider bars.  

I think that the fear of shorter stems resulting in twitchier handling is a little over stated.  Ofter with a shorter stem you need wider bars to make the handling as fast as before.  

Not sure what your riding position is, but I am very comfortable way down and forward.  

So, I guess my view is this:  I would rather put a shorter stem on the L rather than a longer one on the M as well as moving the saddle farther back than it should be.

Chris


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knl2stl
http://www.gtbicycles.com/usa_en/2015/bikes/road/adventure/grade-carbon-105

Under "Geometry"

Here for the 2016, which looks the same, just scroll down:  

http://www.gtbicycles.com/usa_en/gorogue/
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b0rderline
knl2stl - there is only geometry there. No info about rider height versus frame size. So this does not solve my problem [wink]

Regarding the stem length. I have not measure it myself but just from looking at it You can tell that it is longer than in other similar bikes of comparable size. And I too think that longer frame and shorter stem is a better combination.
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knl2stl
Most manufactuers don't bother with rider height per frame size, since such a thing does not consider longer legs vs shorter, longer torso vs shorter, spine flex, riding style, etc.  Many don't even bother with reach, which is a problem.  TT and reach will tell you the most.  It sounds like you think you are between sizes (an issue I know well) and if you can't test ride, then you just need to make the call.  GT can't really do that for you.  Another thing to consider is stack.  You mention the long head tube, and the stack is kind of high.  With that reach and stack (this coming from a flexible person) I don't think it could stretch you out that far.  Reducing the stem of the L by 20-30mm would put the reach of the L under that of the M by the way I see it.  Good luck!
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RayJ
I've got a Carbon 55 cm Grade. Measures 21 inches from tip of seat to center of my bars running a 110 stem with. I'm 5'10" with 31'' inseam  if that helps any. 
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b0rderline
Have You tried 56 cm frame? 

It is said that regarding road bike it is better to have shorter than longer frame but I seek for the comfort first and I think that better comfort will provide the combination of a longer frame with longer head tube and shorter stem.  Shorter 55 cm frame with shorter head tube and standard stem will create a more racy position.
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the mayor

You're about 5'8" right?

without seeing you....I would say go with the 55.

I am 6' with a 36" inseam and ride a 56. It's a big bike.

Again.....the shop your buying from should be helping you

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gravelfondo
I am 5' 11" (180.3cm) with a 32" pant inseam.

I bought a 56cm GT Carbon Grade.  I did change the stem from a factory 125mm length to a 110mm length, and switched the seatpost from a factory layback to a 0-deg post.  These were more of personal fit changes and may or may not apply to you.

I do like the longer top tube and wheelbase and change those above items as needed for the desired fit.
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b0rderline
i am more like 5'11". And got response directly from the GT that I am (suprise suprise) just in between and can ride both M and L size. But for sure L size will require the change of the stem for a shorter one.

Gravelfondo - have You tried M size before buying? And if so, did You feel cramped?
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gravelfondo
@b0rderline - I did not try a M.  There was not one available, but I pretty much knew I wanted the L (56) based on the numbers/geometry as compared to my other bikes.
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b0rderline
Thanks gravelfondo! when I compare reach of both sizes then there is only 8 mm difference. The stem is longer, but changing it to a shorter one will eliminate any difference. But the head tube wlll stay longer and thus will create more upright and comfy position on bigger frame. So if the comfort is what I am after then the bigger frame is the one to go I think.
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lennymatuszewski
First off, great choice. I just got mine last week and it's amazing. I'm pretty close to the same height and inseam as you and I went with the 56. I did swap out the stem and seatpost (100mm stem and 20 degree setback seatpost, both Bontrager XXX) but those were personal preference. I have no doubt that I could've ridden it stock and been comfortable. If I had a 110 stem laying around, I think that would probably be perfect.
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b0rderline
I had a very informative talk with a GT salesman today. He told me that the difference between M and L size can be very small. He said that the 2 cm difference in head tube length can be eliminated by 2 cm of spacers put on the smaller frame and the reach will be around 1 cm different with the same handlebar height. M size frame has  a 1 cm shorter stem which gives 2 cm in total. Putting 2 cm shorter stem on L size will make the bike feel virtually the same. The real difference will be in standover height (he said that 80 cm may be too close to the limit for me) and the handling. L size frame has 71.5 head tube angle which combined with 10.5 cm stem will result in more quicker steering response comparing to the 70.5 head tube angle of M size frame and 11.5 cm stem. But again he said that in normal riding I will not feel any difference. Lastly, there is the 6 mm difference in the wheelbase. Negligible in his words, even more so if I want to shorten the stem of the bigger L sized frame. So in the end he said that the more safe choice for me would be the M sized frame. Mostly due to the lower stack but also because it gives me opportunity in the future to decrease the handlebar height and experiment with more racy position (which I wil not be able to do on L sized frame).
What do You think?
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lennymatuszewski
That sounds like good advice. The bike does have a very big feel to it. I'm coming off of two cyclocross bikes that I used as road/gravel/etc. so the "big" feeling was very welcomed. Haha I was ready to be done with the race feeling and wanted something comfortable but that I could keep up on club rides with so the 56 fits me well. I have my stem slammed and it's not a very racy feel, so I'd recommend the 55 if you think that's something that you'd want in the future
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lennymatuszewski
I have one small spacer under the stem just because I don't like running the stem directly on top of the headset and this is what the saddle to bar drop looks like
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b0rderline

@lennymatuszewski - it looks very nice. How many spacers do You think can be put there?

 

The distance between saddle and handlebar still looks rather long. Even though the seatpost does not have setback any more and the stem is 2,5 cm shorter.


I have two more question for You, if I may [smile]

The first one is: how long is the visible section of the seatpost in Your case. The reason I am asking is that I am thinking about buying VCLS 2.0 seatpost which flexes nicely but in order to be effective, it needs at least 15 cm between saddle and the frame.

The other question is about the fork length. Can You measure it? I am very interested if this is more like 390 mm or 405.

Thanks!

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lennymatuszewski
@b0rderline I've got 13 cm of seatpost showing there. That's collar to the clamp bolt. To be honest with you, the frame has so much flex I don't even know if you'd notice the seatpost. I couldn't tell the difference between the stock post and the XXX except for the weight. I did a rough measurement of the fork axle to crown and got about 395mm. When I get a chance later this week I can take the wheel out for a bit more accurate measurement. Hope this helps. Also hope you get your Grade soon! One of the best decisions I've made!
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lennymatuszewski
I've also started a Facebook group. I figured that would be the easiest way to connect everyone.

https://www.facebook.com/groups/1520981758229045/
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tsupport
I know this is an old thread, but I am facing the same decision as the OP and I am the same dimensions (179cm tall, 83cm inseam).  But, due to an amazing but very time-limited deal I am already the owner of a size 56 Carbon 105 Grade. I bought it without ever seeing or trying it out because it had everything I wanted AND a carbon frame within my budget. It's still in the box in my living room while I decide if it's the right size or if I should go with the 55.

I went to a bike shop and sat on a 55 (no seat adjusted, no pedals) and it seemed comfortable. Then I tried a 56 (the seat was too high, no pedals) and it seemed like a huge reach. But when I look at the geometry numbers the reach is a little less than bikes I've tried and liked and I have been sized for a 56 at a bike shop, so it should be the right size. The 55 is smaller in dimensions to most of the other bikes I have tried. It's the stem and seatpost that make the reach so long on the 56.

So, do I keep the 56 and get a shorter stem and different seat post, or do I exchange it for the 55? I would prefer a more upright, not aggressive position.

OP, if you are reading this, how do you like your Grade after over a year?
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rocthrower
If you want a more upright position, I'd say to stick with your 56 and get a shorter stem.  The 55 will have shorter headtube, bringing the bars lower.  It would probably fit fine, but would be a little more aggressive than the 56.

I used to own the aluminum 105 Grade in a 56, and I'm about 178cm with an 80cm inseam.  The stem on my bike was 120 mm, which was way too long.  I settled on a 100 mm stem and didn't have a ton of seatpost showing, but it was a comfortable fit.   
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Social Climber
I hope I can piggyback on this thread.  I am looking to buy a GT Grade as well.  I am just under 5'6" with a relatively short "actual for bike measurement" inseam, approx 20.75".  One dealer suggests a 53 frame size and another a 51.  It's my experience that GT frames run a little large. No interest in racing.  Most riding is on roughish to normal roads, some fireroads, and weather and root beaten paths.  Would like to ride the Erie Canal trails this summer as well as others in the north east as schedules permit. Any insight is much appreciated. If I've missed a relevant resource or thread, please point me in the right direction! 
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