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Zero Miles from Myself
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Discussion Starter · #1 ·
I am in the market for a new bike. I currently ride a 17.5 Marin Rock Springs and it is OK for stand over hight, but seems a little big in the "Flickableness" for my 5'10" self with a 32" inseam.

When I look at what people are riding in pics (a great thread BTW) and at the local trail, it seems many people are going with frames that would be smaller than the typical "recommended size" based on some theory. My Marin RS was the "Correct" size for me, but It is big too look at.

I will eventually ride some stuff before I pick a bike, but is the trend toward riding a smaller frame size and dealing with the shorter top tube by either living with it or a longer stem? I ride mostly XC and mild tec stuff. No real jumping to speak of at the moment.
 

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mrm1 said:
Not pickinng because it is trendy ... wondering if there is a reason behind the trend and what the reason / logic is. i.e. why are people going smaller (if they really are)? What are the likes / dis-likes about it.
Unfortunately a lot of what have witnessed is trendiness. I have heard many lbs salesmen recommending smaller bike because they are "easier to handle". However, it does make sense for some applications.

A smaller top tube is easier to just deal with when you have a taller front on the bike, whether that is because of a long fork or just a tall riser bar. This avoids the feeling of being hunched over with your hands in your knees. The result is you are less stretched out and sit up straighter. This sounds preferable to me for a DH/FR bike. But for an XC bike, nope.

Also, people that spend most of their time with their butt behind the seat and over the back wheel probably want a shorter top tube;)
 

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i ride a smaller bike. xc. and it is because of the flickability, the difference between my model an the xc racer, was about 10mm top tube, then i use a 18mm setback seat, and 45mm stem. this allows quick fast decents because the the top tube is small enough to easily get behnd the seat.it also allows a great position in the air. very neutral. i was on the fence of sizes, and i have ridden one size up, but it is a stretched out position, and i prefer the smaller size coming off a bmx.
 

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It comes down to how you measure the frame size.

Marin do it from the centre of the bottom bracket to the centre of the top tube (c-t-c) whilst the other bike companies (Specialized, Trek, Cannondale etc) measure theirs from the centre of the bottom bracket to the top of the seat tube (c-t-t).

Consequently, your 17.5" (medium) Marin is actually a 19" (large) bike in comparison to other bikes.

In my mind, c-t-c frame sizing for mountain bikes is misleading as there is no standard which defines how much seat tube that there should be above the top tube - hence, lowering the saddle for aggressive riding may become a problem. I once saw a custom built Ti mtb frame that was 17" c-t-c, but actually measured 21" c-t-t, that's an extra 4 inches!

When buying a new frame, buy the smallest one that will comfortably fit you. The reasons for this are obvious.

And find out if the frame size is quoted as c-t-c or c-t-t.
 

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No good in rock gardens..
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taikuodo said:
I think its because less kids are getting into XC, and applications like dh/fr etc simply require smaller bikes.
Absolutely - so many bikes come set up for the casual rider who has no interest in actually pointing their bike UP a long steep hill.

Long travel suspension, high front ends, and many bikes targeted to the casual rider and those who just want to have "fun" rather than do more traitional XC riding.

I'm amazed by how some people here manage to squeeze onto frames that sound too small - 6' guys on 16" frames etc.
 

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Dirt Deviant
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Alot of it depends on how a persons body is shaped.
I am about 6' 4" with shoes on, but have a really short inseam and long torso with long arms. So the perfect fit for me is the bigger size.
While I am sacraficing standover completely, I am really after that longer top tube because I need the bike longer for my upper body.
If I go with the proper size as my standover would dictate, I would be all scrunched up and would hurt my knees and back.
I've found the perfect fit is one size over what standover dictates, which usually gives me less than a half inch or less of standover clearance.

I hear what you are saying about the smaller bike thing though......and it does seem like a trend.
 

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Zero Miles from Myself
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Discussion Starter · #10 ·
standard3x said:
It comes down to how you measure the frame size.

Marin do it from the centre of the bottom bracket to the centre of the top tube (c-t-c) whilst the other bike companies (Specialized, Trek, Cannondale etc) measure theirs from the centre of the bottom bracket to the top of the seat tube (c-t-t).

Consequently, your 17.5" (medium) Marin is actually a 19" (large) bike in comparison to other bikes.
Like i said, in theory it is the "right" size for me, but it does seem big. not too big, but more like I am ride on top of the bike rather than having the bike under me. The later would be more "flickable", but I am not sure it would be a more desirable ride .... just different.

I guess the good news with this '04 RS is that there is not much seat tube above the top tube and the Suspension design allows for the seat to go all the way down. BUT one thing I cannot figure out is the Stand Over Height Spec from Marins web site. A standover height of 44" Yikes .... where is that number coming from? it really mesasures about 29. Oh and BTW, I run my fork at about 100-110mm travel, the geo chart is for the fork set at 125mm and I also have the Alpine Link on it which dropped the BB hight about 1/2 " and slackened the head tube to about 69 rather than 71
 

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Standover height isn't usually measured at the lowest point on the top tube, no, it's measured from the mid-way point between the effective horizontal top tube.

Btw, your choice of tyres and the pressures that you run them at also has a bearing on standover.
 

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I think too many riders are buying bikes too small. I'm 6'1 and ridea 19 in for XC and a 17 in for a freeride bike. For many riders for height, my bikes are too big.

I've always had 19 inch frames for all around bikes, pedaling anything smaller feels like my knees are going to hit my chin.

When I pedal my 17 inch bike up hill, the bike feels very very small, I need to run a 410 mm seatpost to get the right leg extension. Before I bought it, a lot of people on this forum suggested I get a 16 inch frame, a 17 would be way too big.

Different bikes are sized very different even if they're both the same size. Try and ride a couple different bikes, different sizes to get your right size.
 

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Small frames were always just a fop to get around the high standover and the weight-forward riding position of the older MTB frames. They were great going uphill, but coming down, the center-of-gravity was WAY too far forward. Hence, smaller frames, laid-back seat posts, and ad-hoc handlebar arrangements to compensate.

Once the top tubes stopped being parallel to the ground and the frames took on a more laid-back BMX-style geometry (which MTBs always should have had), it became a moot point. This is just as well, because if you ride a too-small bike for too long, you WILL develop a painful repetitive strain injury in your knees eventually. Not good, this.
 
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