mtb sizing

fatbob · Post by **fatbob** » 21 Nov 2007, 1:00pm

Hi there - I'm looking at buying a mountain bike and my lbs has a giant xtc 4.5 on offer at the mo. I usually ride a marin hybrid with a 17.5 inch frame (I'm 5ft8/9) but the 'medium' bikes I have tried give me zero crotch clearance - I've ridden the Giant and it's very comfortable but it has a 14.5 inch seat tube that gives me about 3 inches of stand over clearance. Is this too low?

Post by Si » 21 Nov 2007, 1:26pm

Sounds OK to me. I'm 5'11" and have three MTBs, two of 18" and one of 16". They all fit me fine because the reach is the same on all of them.

The trend amung MTBs these days is for quite short (virtual) seat tubes, giving a good amount of goollie clearance and plenty of room to move around in the cockpit. As long as the reach isn't too short for you the 14.5 should be OK.

fatbob · Post by **fatbob** » 21 Nov 2007, 10:28pm

Thanks for the advice - I haven't much MTB experience, so it's greatly appreciated!

ransos · Post by **ransos** » 28 Nov 2007, 3:28pm

I'm 5'9" and have had two Giant mtbs, both in 16" frame. In each case, the seat tube was near to its maximum extension, so you may find that the 14.5" frame is too small.

bikegeek · Post by **bikegeek** » 28 Nov 2007, 3:41pm

I'd say like ransos get the smallest frame you can (for ba11 clearance) but watch that the seatpost is still in the safe range.
You say the Giant is comfy and 3" standover may be ok. You can ride a bigger (taller) bike offroad but you have to then develop the skills to not hurt yourself with it. On some trails it might not be the 'standover' height thats applicable but the 'bellyover' height as you tend to stick your backside out the back for balance, causing your stomach to sit on the saddle if it's too high.

orangechimp · Post by **orangechimp** » 28 Nov 2007, 9:37pm

i'd say 3" is about right, ride the bike first though just to make sure. i'm 5'8" and have a 15" orange Mr XC and it's just right, but my hardtail is a 17" P7, both about the same reach etc, but the crank is higher off the ground on the full susser.

fatbob · Post by **fatbob** » 7 Dec 2007, 12:39pm

I went for the Giant and am really enjoying it (when it isn't micturating it down!). I'm intrigued by something though.I've just realised I may have been measuring the bike incorrectly. I've compared it to my hybrid and there just doesn't seem enough clearance for a 14.5 inch bike compared to my 17.5 hyrid - and there's no precise measurement at the centre of the top tube on the Giant. The only precise measurement I can get is 17 inches from the centre bb to the top of the seat tube. Are mtb frames ever measured in this way? A 17 inch frame would certainly explain the closeness in sizing to my Marin (top tube 1cm shorter, inch extra standover). On the other hand, there is a 'small' label on the frame. I've since discovered that the xtc 2007 bikes come in sizes 14,17,19,21 and 23, which would make a 19 'medium' and would explain why I had zero crotch clearance on a 'medium' bike. It's all very confusing! After all, I'm 5'8/9, which is, I think, about average height. Any info would be greatly appreciated!

orangechimp · Post by **orangechimp** » 7 Dec 2007, 1:01pm

good question, it would seem that all the manufacturers have different ways of measuring their bikes, which makes things all very confusing.

i test rode 2 bikes last weekend at 18 bikes in hope, who i have to say are really helpful and pleasant. anyway, i tested a Cotic Hemlock which was a medium and a Pace RC405, also medium, both very simular bikes, but the sizes were quite different, longer reach and more crotch room on the Cotic than the Pace, but both of them comparable to my Orange, which is effectively a small. a small Cotic is the same as the the medium, but with 1/2" difference in the top tube length.

ransos · Post by **ransos** » 7 Dec 2007, 3:43pm

fatbob wrote:I went for the Giant and am really enjoying it (when it isn't micturating it down!). I'm intrigued by something though.I've just realised I may have been measuring the bike incorrectly. I've compared it to my hybrid and there just doesn't seem enough clearance for a 14.5 inch bike compared to my 17.5 hyrid - and there's no precise measurement at the centre of the top tube on the Giant. The only precise measurement I can get is 17 inches from the centre bb to the top of the seat tube. Are mtb frames ever measured in this way? A 17 inch frame would certainly explain the closeness in sizing to my Marin (top tube 1cm shorter, inch extra standover). On the other hand, there is a 'small' label on the frame. I've since discovered that the xtc 2007 bikes come in sizes 14,17,19,21 and 23, which would make a 19 'medium' and would explain why I had zero crotch clearance on a 'medium' bike. It's all very confusing! After all, I'm 5'8/9, which is, I think, about average height. Any info would be greatly appreciated!

If it's labelled "small" then it's 16".

james_h · Post by **james_h** » 19 Jan 2008, 5:05pm

I read this thread with interest fatbob, as you're exactly the same height as me - what I'd consider bang on average (5'8"/9") yet cannot get this much talked about 3" of recommended standover height on a "medium" .

When I bought my first mtb about 18 months ago, I opted for a small frame purely to get the standover height which I was over focussed on. Every bike shop I spoke to said for my height I needed a medium, but I went for the small anyway.

Anyhow to cut a long story short - the small was too small. I've since bought a couple more bikes in medium which although don't give me this so called required 3" of standover (probably more like 1") but they fit me like a glove. And I can't actually bear to ride my old small bike now... So the moral of my story (in my humble opinion) don't get hung up on the standover height!

andymiller · Post by **andymiller** » 19 Jan 2008, 8:22pm

You also need to consider the length of the top tube. With compact geometry frames you will normally have plenty of standover clearance but that's a fat lot of use if the top tube is too long for you.

fatbob · Post by **fatbob** » 31 Jan 2008, 2:51pm

That's just the thing Andy - my Giant has a compact frame with plenty of clearance, but still has a virtual top tube length of 55cm. Christ knows what the TT measures on the 'large' bike! Assuming, of course, it's proportionate. It's like Dawes's tourers. They all seem to have a similar TT length regardless of seat tube height. Why bother with sizing in such instances? As a newbie to MTBing, it seems that the same rules apply as so often do in other cycling arenas: there are as many takes on the idea of a MTB as there are manufacturers. I think that there is also a pressure on manufacturers to differentiate themselves from one another in a struggle to capture market share, something that can be very confusing for newcomers like myself. After all, how much difference can there ultimately be between a 'XC' Mtb and a 'Freeride'?