Hey everyone,
I’m 173cm tall (5’8”) and trying to figure out if an 18” frame is too small for me. I’ll attach a photo where you can see both of my bikes side by side for comparison.
The orange one is a size 20” Rockhopper Comp. The saddle in the picture is set to the height I normally ride with, which feels right to me. However, the handlebar feels a bit too far forward — not a huge issue, but noticeable.
That’s why I recently bought a smaller frame: an 18” Trek 970. On the picture, the saddle is actually a bit lower (measured from the BB) than on the Rockhopper. If I raise it to the same height, the seatpost ends up slightly over the max line, which obviously isn’t ideal. Also, the bars on the Trek feel even less comfortable — they’re noticeably lower than the ones on the Rockhopper.
Ideally, I’d like to keep the Rockhopper mostly stock, maybe just bring the bars a bit closer or higher. But I’m wondering if it’s worth trying to set up the Trek for comfort, or if I’m starting with the wrong frame size altogether.
Also — why do so many people say a 20” frame is too big for someone my height, when it actually feels more comfortable to me?
Would really appreciate some insight or feedback on this.
Thanks in advance!
by achtung986
18 Comments
Fit is pretty subjective, but I suspect that you have pretty long legs for your height, which is why you have the seatpost so high on the Trek, and the position feels pretty “road bike” to you. I’m 175cm/5’9″, but I have stubby 30″ inseam legs, so something like a 17-18″ in this era of MTBs is pretty much a dead-on fit.
I would suggest playing around with stems and bars; the cockpit is the first thing I change up on a bike for myself. I think you have the right idea about the stem being too low on the Trek; it’s also a pretty long reach. I’d bet you have at least an inch or so of vertical adjustment on the stem, and all that costs is maybe a new front brake cable. If you want to keep the straight bars, a shorter reach stem can bring the bars closer; otherwise, swept bars on the original stem should leave you feeling less stretched out.
I’d say that 18 is just right. Wouldnt go any smaller.
Seatpost looks ok but you would need a higher stem imo. You can always get shorter stem for the Orange bike.
Bitd, most folks would have ridden a medium or 16.5/17 inch frame at 5’8”. We just stuck longer stems (say 100-120mm) on them. The tight wheelbase made for a more maneuverable bike.
Reading between the lines, you have relatively long legs and a short torso/arms for your height. Because of this, neither bike is optimal for you – both are “long and low” like most performance-oriented 90s MTBs.
(Sidebar: This trend was why the decade ended with the introduction of “Women’s Specific Designs” because the brands figured out that the dominant design was alienating half of their potential customer base. Current brands like Fairlight go beyond simple gender profiles and make their bikes in both ‘Regular’ and ‘Tall’ variants to suit the long of leg of all sexes.)
The 20″ bike feels good for you because you don’t have to dive for the handlebars above the shorter head tube. However, you’ve had to slam the saddle as far forward as possible to handle its increased reach and it’s still a bit too long. You may find your hip angle is too small, which eats power.
You can adapt both bikes, with a longer seatpost, or different bars respectively. Personally I think the Rockhopper is the better one to adapt of the two, because the Trek would have to be built up both at the bars and saddle.
However the best fit might be a bike with a taller head tube and shorter top tube. Usually these were the midrange and lower bikes in the 90s ranges, with a few niche nice bikes like Georgena Terry’s. Maybe this sub could crowdsource a list of 90s MTBs with a higher stack to reach ratio?
Edit: another data point, 5’11”, 34″ inseam, ride 18/19/20″ MTB and 56cm(22″) road/gravel.
Because some folks are all legs or all torso, and I’m guessing you’re all legs.
Bars that sweep back would probably increase your comfort
I’m also 5’8” and comfortably ride a range of 18-21” bikes. Just dial in with seatpost and stem lengths.
As others stated, fit can be subjective. I’m 5’6″ but the way I’m put together, I size up. Stand over height doesn’t really work as far as fit goes for me, I end up feeling cramped on bikes that have the generally accepted stand over clearance. So if I’m stopped I lean the bike over slightly to put a foot down as well as mounting. The “standard ” sizing system really isn’t standard and varies from one manufacturer to another so it’s really hard to say how a bike will fit but provides a decent starting point.
Both great bikes, but you’re just dealing with being an in between fit for this geometry as others have said. Consider swept back bars with some rise!
I would argue that it depends on your use case. If you actually do a lot of single track, then go by the mountain bike sizing charts. If you are using a mountain bike as a road bike or even gravel mostly, then refer to the road bike sizing charts. Top tube length can be dealt with by dialing in your cockpit if the reach is a little long.
I’m 174cm tall. Run the same (ish) bike, 18inches I did bosco bars to get the front end up. Wouldn’t be as much need for handlebar rise if I could find the rare 1” 1/8th quill stem with more than one clamp bolt or if I could afford to upgrade to a stridsland or magic fork.
You either have long legs for your height or, you (like me once upon a time) put your saddle too high for perceived power output and a habitual need for an aggressive stance from riding fixies or racer bikes? This is a guess, cos I did this and it was a true revelation when someone explained the heel on the pedal theory for saddle height.
Here’s my set up. Wouldn’t want any bigger frame really. I’d only go 20” on these 90s mtbs if I was only gonna do the most pedestrian of riding on a road. Otherwise, I like the extra stand over clearance for rough descents.
https://preview.redd.it/4535wpebub6f1.jpeg?width=4966&format=pjpg&auto=webp&s=166dbbfa197c8d9307a753b4bf6cb708d9f7950e
I am the same height, and that’s about perfect for me in a 26.
Where are you measuring from? Seat tube, from center of bottom bracket to center of top tube? Or center of bottom bracket to top of seat tube?
Because different people measure differently, I like to measure effective top tube length. Combined with the stand over height.
Perfect size. You could even ride a 17”
Depends on a a few variables but it should be an okay fit. Not great but it is what it is with the old bikes. Could be a little long and certainly low reach.
I’m 5’9 and have long legs and arms. I have an 18” frame that I need to raise the stem on. I also have a medium bridge club I had to buy an uncut steer tube for. Could have went to a large but I bought it used, and the internet said it would fit me.
I’d try an alt backswept bar like Jones H-Bars or Surly Moloko bars on the Rockhopper. You’ll won’t have as far to reach, and will still have some alternative hand positions.
Nope should be perfect, 22.5” large is to big