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I am 182cm (5' 11'') tall and am looking into buying a new frame for my mountain bike.

Right now i have a 19'' frame and i found a good deal on a 17'' frame.

The guy from the shop told me that it shouldn't be a problem for me to get a 17'' frame since you can have a longer stem and seat post so its fits alright.

Smaller frame means lighter but what are other advantages and disadvantages ? Would you choose a smaller frame ?

Update The difference top length (seat tube to handlebar stem) from my 19'' to this 17'' is 1cm.

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  • Solo, you really need to compare effective top tube length to truly understand the comparison. Make sense?
    – GuyZee
    Commented Jun 1, 2011 at 21:03
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    Instead of faffing about with a ruler, can't the shop guy give you a test ride?
    – cmannett85
    Commented Jan 10, 2012 at 18:25
  • A friend recently got a small-ish bike because it was a good deal. Was very sorry after that. Though a too-small frame would be nice for downhill, I suppose.
    – Vorac
    Commented Jan 29, 2014 at 16:06
  • @cmannett85 probably he can, but a test ride wouldn't allow you to spot mid/long term issues associated to the size (back pain, knee issues, for example). I guess that's the main 'benefit' of getting the proper bike size
    – Rodrigo
    Commented Oct 12, 2017 at 15:32

12 Answers 12

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  1. With a smaller frame, you will need an appropriately longer handlebar stem in order to retain the cockpit length. Bike handling will be affected: it will feel more "lively", which can be good in some cases (tight turns, difficult terrain) or bad (less stable) - in most cases. This effect on bike handling can be partly explained by shorter wheelbase.
  2. A smaller frame will be marginally less reliable, and more prone to break, due to bigger stresses in its structure; longer stem and seat post mean bigger levers to exert force on the frame. But this should not be a significant effect.

As a rule of thumb, a 17" frame is an inch or two too small for your size. I would not recommend taking the smaller one without actually riding it for a couple of hours and making sure it's comfortable for you.

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  • Agreed. The 17" is definitely too small, aside form a few special purpose bikes, or an unusually proportioned rider, based on your height.
    – zenbike
    Commented Jun 20, 2011 at 13:04
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    +1 For the stem comment. Increasing the stem length has the same effect as steepening the head angle, which is usually a bad thing.
    – cmannett85
    Commented Jan 10, 2012 at 18:23
  • Actually a smaller frame made with the same techniques and materials is more sturdy than the same design in a bigger frame, due to the shorter leverage of the internal forces in the frame.
    – Jahaziel
    Commented Jan 12, 2012 at 13:18
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    @Jahaziel The internal forces in the frame will be smaller, but the external forces exerted by the necessarily longer stem and seatpost will more than make up for it, because proportionally more leverage will be added externally than removed internally.
    – ttarchala
    Commented Jan 22, 2012 at 21:27
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A smaller frame also means a smaller reach--that's the distance from the saddle to the handlebars, and if you have short arms and/or torso height then a smaller frame may be a good idea. If not, you may find this frame too small.

This can be mitigated by sliding the saddle backwards in the rails a bit, but this can account for perhaps an inch at most. Changing the stem size can also help. If you want a more upright position on the bike, a smaller frame could help somewhat.

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    You can also get what's called a layback seatpost in order to make the reach a little longer. You won't be quite aligned with the pedals in the same way as before. I've never used one and can't attest as to how comfortable they are.
    – Kibbee
    Commented Jun 2, 2011 at 14:28
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Both Neil & Ttarchala are spot on. The one additional comment or perspective that should be considered is with a smaller cockpit your body may not be stretched out enough and for me the impact of mountain biking on a bike with too tight a cockpit wreaks havoc on my BACK!

Think of your spine as a coil...is there more flex when it pushed together or stretched out...that flex softens the ride and allows for more movement which ultimately improves your riding, is less taxing on the body therefore less fatiguing.

Also, too long a stem tends to put too much weight forward which increases the likelihood of issues with your upper body and increasing propensity to endo :(

Be careful..probably not a viable option!

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  • I have a small bike and am constantly worried about the endo on technical terrain.
    – Mranz
    Commented Oct 25, 2011 at 20:59
  • I agree. Using a longer stem puts you more forward, more over the front wheel. This, along with the shorter wheelbase of the smaller frame will increase the possibility of endos. For a long time I rode a small frame with a longer seat tube & stem, but, recently, I moved to a larger frame for safety.
    – Malarky
    Commented Dec 1, 2021 at 20:36
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There is some good information in some of the answers here, but, in reality, more information is needed to give a better answer. (Inseam, reach, type of riding you do...just to name a few key factors.)

I'm sure you've already made a choice by now, but just because you had a 19" frame doesn't mean that it was correct or incorrect for you. Certainly different size frames, with different stem combinations, tire sizes, and steering & frame angles will affect the handling of the bike.

Most likely there's going to be nothing "wrong" with choosing either size (given most mainstream manufacturers fit guides and your height), but they will ride differently.

In most (possibly all) types of mountain bike riding, if you need the seat moved to one end or the other of the rails, or if you feel you need a stem longer than 100mm, you probably need a different size frame.

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Weight comes into it too - I've ridden bikes that were too small for me, but with long seatposts, and in 20 years I have bent four of them and cracked one frame at the seat clamp.

The total length of your seat post from clamp to saddle should be no more than 30cm, and a max 20cm is much better.

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Generally a slightly smaller frame than recommended is a good idea. I am 6 ft and I ride a 56 cm road bike though 57 - 58 cm is recommended by most manufacturers for my height. The advantages are lighter, more aerodynamic, more compact, more 'on top of things.' I have made adjustments by putting the seat as far back as possible, raising the seat post and substituting the stem for a -17 degreee 140cm.

However if you are small and my g/f is 5 foot 2 inches and she rides a 13" mtb then the problem is that with such a small frame I think you will lose speed, she'd be better with a 14 - 14.5" frame imo.

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Ultimately there is a simple calculation which is.

Your height x the length of your beast / divided by 26.5 which would suggest your best with a 19" frame.

Trust that helps out.

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I'm 6ft and just brought a medium Lapierre (43) and so far am finding it fine. I was riding a large Giant Trance before this and often felt I was over reaching when going down hill (also had upper back pain often). The only thing I've noticed so far is needing to adjust my riding style to ensure I'm not too far forward and getting the weight over the bars.

Might condider a dropper post with a slight lay back if I can find one.

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Riding my little sister's MTB(she is significantly shorter than me):

  • low-speed handling is improved: hopping, jumping, wheeling, 90°, front or rear balance is so much easier
  • efficiency is severely reduced: both flat and uphill
  • at high speeds or rough terrain the bikes feels uncontrollable (but so much fun to bounce around).

This is an extreme example of size mismatching. Can perhaps still be helpful. Smaller == more playful, less speed-centric choice.

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I made a huge mistake, I had to order a new bike online. As the local dealers was way to overpriced here and their bikes were crap, I had a coupon for 35% of at a online shop. I'm 6" and ordered a 27.5 S (400mm) 15.6" as the manufactures site showed that I would fit S/M, I should have ordered a M which is 17.5 (445mm) but either way something would be off. Now I'm trying to adjust my way out of a bad purchase, the 17.5 would not have good crotch clearance so either way something would be wrong with the bike. Even with the S fame, I nudged my balls hard a few times on the top tube at a steep clime where my footing slipped. Xo/ Now I hope I can do something, my saddle is set nearly all the way back for my legs to have the right angle over the crank, and I'm gonna add a 70mm 35 degree stem to see if that can do the trick. I get lower back pain when I ride a long time and feel like I'm to far over the crank on the bike, hopefully the 70mm raised stem will do so I can get that higher for a more comfy position. I already have added a 40mm raiser bar and tried out a cheap stem with no raise and no extension so it's so close to the headtube as possible. It's helped a bit, now I'm just trying out stuff to see if I can get it to fit even better. I don't know if I should find a swayed backed dropper post, and if it will help me in the last adjustments. It's is so close to be a good fit but It does just feel a bit off.. Irritating and not fun to have these problems.

But the lesson others can take away from this is, get yourself measured and get a professional to find your first bike. Now I've used over 2000$ and I'm still not happy with my bike.

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    Welcome - sorry to hear you bought a bad-fitting bike. Your answer boils down to "a cheap bike that is too small will cost more because of replacing parts to get a better fit, and that its cheaper overall to buy a bike that fits right in the first place."
    – Criggie ♦
    Commented Oct 12, 2017 at 2:38
  • Welcome to Bicycles SE. We ask that you write to the best of your ability on this site. This means proper capitalization, proper punctuation, and complete sentences. There is some good, relevant information in your answer (such as your back pain and your contact with the top tube), but it's hard to interpret in the unstructured format of your post.
    – jimchristie ♦
    Commented Oct 16, 2017 at 13:59
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From my experience, frame "height" is nothing. Unless you are a shorty, then a small one is a definite choice.
If you compare exact model frames with only frame height as a difference, all riding dimensions will be the same. But different makes and models will differ.
I am 6'2" and have for a very long time used 17" frame. (mountain bike)
As such it is good for on road, and if I drop the saddle a bit, great for off road. Easy to mount and dismount. Less chance of cracking the family jewels.
Only thing I have had was that over time (many years and abuse) is that the seat post slowly bent backward. But is a minor issue and easily replaced.

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My height is 165cm (5ft 5). I currently use a 48cm sized (xxxs) CX bike. At first it was okay, No problem so far. But then I got into an accident, downhill on a tight right turn I attacked hard (I thought I was a Pro Racer) with my upper body leaning forward I felt my weight shifted too much on the front wheel that made the tire to skid. I didn't even do anything besides leaning forward and it cause me eat the asphalt. The next thing I knew it was my face on the road, good thing there were no on coming traffic at that time. For casual riding I think frame size is not a problem so long as your comfortable, but for competitive riding a proper bike fit is a must.

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