I'm a new cyclist and I'm looking for a new bike primarily for recreation and also for fitness. I would like a mountain bike mainly because I like the style and the fat tires! However, I won't really be doing much if any trail riding. I did some research to try and determine the right size bike for me and based on my 5'9" height and my 29" inside leg I found that I needed an 18" or medium sized mountain bike. However, when I went to the store to check them out, it seemed like the 18" or medium bikes were quite small, and I felt like I wouldn't be comfortable on something like that.

So I was wondering if mountain Bikes, by design, are somewhat smaller than road or hybrid bikes due to the way they are ridden? If I'm not intending to do any actual mountain biking with it, would I be OK buying a larger size? I'm assuming that when riding trails etc. most riders are standing in the pedals rather than sitting on the saddle, but I'm guessing I'll spend more time in the saddle when I'm riding, which makes me feel like a larger bike would be best for me.

Just looking for some guidance here so I don't make a bad decision. Thanks

  • 4
    "What bike should I buy" has been asked several times, and I have always answered "Used". You don't really know what sort of bike will suit you best until you've ridden a modest amount, and you don't want to blow a wad of money on a bike that doesn't work for you. A common mistake is to buy a bike that is too large -- these are easy to spot since they are available in garage sales, 5-10 years old and ridden maybe 100 miles total. May 19, 2018 at 2:11
  • 3
    "comfortable to you" Don't be fooled by squishy saddles - you want a bike that fits you more than anything else. If you're not off-roading, avoid a MTB. If you're not going fast on road, avoid a dropbar road bike. Look at a commuter or hybrid bike as an "average" thing. If they feel too small, they are too small. If you want fat tyres, get a commuter with fat tyres. Riding is for you, not how you look on the bike. Also, Daniel is right with the used choice - for a first bike its a wallet friendly starting point to clarify what you want and don't want.
    – Criggie
    May 19, 2018 at 2:16
  • If you're expecting "brand and model and size" answers, you won't get them. On this Stack, such answers are considered off-topic because they're of short term use to one person only.
    – Criggie
    May 19, 2018 at 2:18
  • 1
    If going mainly on paved roads, a mountain bike is just wasting your energy. If you put slick (road) tyres on a MTB the choice is wrong from the start. I would get a road bike with allowances for big tyres , that would be the old hybrid, modern gravel bike. You can go with those on off road trails (those that a car would be able to do too )
    – gaurwraith
    May 19, 2018 at 18:14

5 Answers 5


Whenever I am asked a question like yours, I invariably ask back: "what are you going to do with that bike?".

As 90% of the time the answer is "dunno", the obvious suggestion is "go for an economical model that fares decently in most situations, then when you have found out what your cup of tea is and you still love biking, go for a more expensive choice".

And this advice is based on my own experience: in the times where having a mountain bike was cool, I rode an old 3 speed, steel frame from the '60s, my father's legacy. It was not cool maybe (nowadays we would call it vintage), but served my purpose.

Then for my first chosen bike in the early 2000s I went for a BSO city bike, sub brand of a major brand. Again, it was not fancy or cool, but I rode about 15 thousand km on it (including a holiday in the central Italy Apennines), discovering that what I like to do with bikes is commuting and touring.

Then my first serious bike was, and still is, a touring bike. I also own a cheap city bike, just because I don't trust leaving my touring model in an unguarded garage for thieves to pick up.

A friend who asked my advice in the past ignored it and went for a cool, expensive, full suspension off road model (where we live the max rise is about 40 m and the only off road, except BMX tracks, is gravel roads in the countryside). He admittedly rode it for a bare 40 km and then sold it after 10 years to make room in his garage.

  • To be fair, you're not going to discover you enjoy mountain biking if you take a BSO to the mountains, just as your friend had no chance of discovering that maybe he might like touring and road biking on that FS bike.
    – user20209
    May 25, 2018 at 22:35
  • @Purr, there are also MBSO (mountain bike shaped objects)
    – L.Dutch
    May 26, 2018 at 2:54
  • Fair point, but I can't imagine anyone new actually enjoying using one on anything beyond a fire road (if that), the brakes tend to inspire no confidence (though mechanical discs on a BSO can be passable, until they suddenly aren't) and the suspension they have is worse than being fully rigid (Not that there is anything bad about fully rigid, I run a rigid fork more often than the fox nowadays, I know my local loops too well.) Note: I have had fun on an MTBSO, but it was effectively destroyed within a day and I wasn't even riding hard since I didn't trust it.
    – user20209
    May 27, 2018 at 4:40
  • @Purr, my point is that to understand what confidence is on a bike you need to start from the base. I enjoyed a proper touring bike after knowing in my muscles what a BSO felt like. Before that all felt the same.
    – L.Dutch
    May 27, 2018 at 5:06
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    ah our experiences were different then, I tried an MTBSO after moving to a place with actual hills and mountains, the nerve wracking and unpleasant experience resulted in me missing out on quite a lot of MTBing; eventually I tried a half decent MTB and fell in love almost instantly and never looked back. I guess everyone is different, but suspect the BSO thing is even more of an issue in MTBing than other forms of biking, I might have had a particularly bad BSO as well.
    – user20209
    May 27, 2018 at 5:17

I think a good idea would be to borrow a bike for a day or two. Either from a friend or from a store/bike rental. They should also have some knowledge about bike sizing and fitting and point you in the right direction. This way you can get an idea about what size you need and what kind of cycling you want to do.

Bicycle sizes can be hard. Usually how high the bicycle is (seat tube length, that’s what the “size” usually is if it’s a length) is far less important than the length (reach) of the bike. Height can be adjusted in a very wide range with the seat post (10 cm up or down should be easily possible). Length can only be adjusted by replacing the stem with a shorter or longer one and there you are limited to a few centimeters (like, 3cm or so backwards and forwards). Fortunately it’s becoming more and more common to talk about stack and reach, which should be comparable independent of frame manufacturer and bike type. If you feel comfortable on a bike, be sure to find out its stack and reach measurements, not just the frame height.

If you are not planning to use the mountain bike for its intended purpose (off-road trail riding where no other bike can go) I’d really recommend you to get something lighter, faster. The fat, knobby tires, suspension and so on will only add weight and rolling resistance. At the very least get a hard tail and consider fitting road tires (i.e. without the knobs). If you are riding on tarmac only you could even get a road bike and I’d really recommend you to at least try one. A road bike accelerates and rolls so much better, you can easily go 5km/h faster just by switching to one.


The best advice to give you I think is go and test ride lots of bikes. All good stores will be perfectly happy to let you do that. Try a few different styles including some more road oriented hybrid bikes to find out how the different geometry feels. Let the bike store staff give you guidance on sizing - which may be different for different styles or brands of bikes.

Some mountain bikes may feel small because they have low top tubes and lots of standover clearance, and handlebars that a relatively high and close to the seat for rough trail riding.

Just a note about mountain bikes at the inexpensive end of the price range: they tend to have cheap suspension forks which are more cosmetic than functional and add lots of weight; and are definitely not required for on-road riding.


Mountain biking has many flavours, but I will assume you mean hardtail XC bike, because full suspension doesn't make much sense if you don't spend much time on the trails.

With that being said, it largely depends on your riding style. I have two bikes, a city/trekking bike and XC mountain bike, and I almost never get my city bike out of the garage. I live in a city with a lot of potholes, and quite often missing drainage covers, which I need to bunny-hop while moving with the traffic in the rightmost part of the lane. I also enjoy riding a bit more aggressively doing occasional jumps and tricks (off the street, when I pass through the park).

On your question about the frame sizes on mountain bikes, it depends what riding style do you have. If you mostly like going downhill you need to be able to comfortably (and quick enough) move your center of weight (your bottoms) behind the seat, so you should choose a bit smaller frame. If you intend to mostly climb hills and do XC marathons covering bigger distances, you should go for a larger frame size, which is more comfortable for pedalling. The same is also true if you are riding mostly on pavement/roads. However the frame geometry is also important, so to 18" frames may feel quite different.

However, if you go the mountain bike route, choose a good locking fork or go with a hard fork and quality fat slick tires. I ride with a locking air/oil fork and fat tires, and the fork is locked 90% of the time I ride in the city. Just for reference, I am 38yo, 170cm (5'7"), 60kg (130lb) rider, and I ride a 17" frame MB and 19.5" city bike.

As other commenters already said it all depends on what you are looking for in the cycling experience. Some days I prefer borrowing my girlfriend's old dutch bike and it is as fun to ride as my mountain bike, just different. However it isn't something you can't change in the future if you decide. Don't get into analysis paralysis, get a bike and ride it :)


You probably have a long torso. You might be able to fix that fit challenge with a longer stem. Bicycles are evolving to have taller head tubes to make all the bicycles more comfortable for long trips. Hence, the "endurance bike".
Mountain bikes have a lower standover height. Since bicycles are sized by seat tube length, then you need to look at a "smaller sized bicycle" if you are looking at a mountain bike.

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