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Discussion Starter · #1 ·
greetings all

I am thinking of buying hard-tail MTB for myself and my wife.

I ride a road bike, size 53-54cm (54cm top tube). My height is 173-174cm or 5 feet 8 & 1/2 inches or 5 feet 9 inches tall at most, inseam 83cm.

What size MTB do I need?

My wife rides a 51-52cm road bike, ~169cm or 5 feet 6 or 5 feet 7 inches tall and has 81-82cm inseam.

What size MTB would she need?

thanks!
 

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Discussion Starter · #3 ·
thanks.

Should I go by the MTB effective top tube length then? I.e. if I ride a road bike with 54cm effective top tube and 73 degree STA then I should get MTB with similar effective tube lengh and similar STA?

In Specialized, for example, there is 53.8cm TT and 55.5cm TT (effective) and also 73 degree STA. Should I go for the smaller or larger one? Thanks again.

Also, what does 17inch MTB frame mean? what does it refer to?
 

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I seem to remember a similar thread to this one a while back, don't remember which board it was though.

I think you're over-thinking this. Effective lengths and whatnot aren't really transferable. The same rule applies to MTB as to any other bike... you really have to go in and try them out. Different manufacturers put them together differently, and even under one parent company, they can be made differently... Fisher, made by trek, uses a longer top tube and a shorter stem, than the corresponding trek model in the same price and component bracket.

Basically, measurements don't really transfer. In general, the size measures the length of the seat tube. But that doesn't really tell you how high the bottom bracket is off of the ground, and some sit pretty high to get ground clearance. You want to be able to stand with a few inches of clearance between the top tube and your junk, since it's very likely on the trail that you'll come to a short stop and have to ether fall over, or slide forward off of the saddle.

All that aside, there are a lot of other things to consider, since some frames are more along the S/M/L/XL sort of sizing chart. On top of that, there's what kind of frame you're interested in. Are you looking for rigid single speed, 29er, hard tail XC, trials oriented hard tail, soft tail, full suspension XC, Full suspension DH/Freeride...

Road bikes are road bikes, and the fit and handling is very fine tuned for the road. (Im sure that's a pretty gross generalization, but in comparison to the MTB world, it's pretty true) The fit issues are very different, both in terms of which kind of MTB, as well as what kind of riding you'll be doing. Are you doing slow and technical, are you doing faster XC on clean trails, bumming or bombing around the city, riding over rocks and roots, riding DH on ski trails, moab rock riding, ice riding in the winter, beach riding in the summer, or through desert sand? There's a wide range of terrain, and a wide range of frame styles to suit. My guess is you're just thinking of a standard hard tail. But even then, there are differences between frames and what they're intended for. There are light, clean XC frames, and beefy, gusseted steel frames that are more for urban freeriding, and even frames like the pugsley that are made to handle really wide tires for sand and snow. And depending on what you're planning to do, you might actually be better served by a small travel full suspension XC frame.

The moral of the story is pretty simple. Skip the theory, and skip the math, don't try to sove this problem in a vacuum. Go down and try a few of em out to see what feels like something you'll enjoy. It's a whole different kind of thing, and you're better served trying different bikes out and seeing what's actually available, and what you might like.
 

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Discussion Starter · #5 ·
thank you! I was afraid you were going to say that! 8^)

yes, we are looking for entry level XC hard tail, for city and trails riding, nothing too technical, a bit of grass, a bit of dirt, a bit of pavement, a bit of road city commute, etc. First MTB, no prior MTB experience. So I dont know what to expect from MTB, even if I test ride one, having been riding a road/racing bicycle for 4.5 years.

My LBS who sold me my 54cm road bike thinks I need 17-18 inch. I might have to take their word for it and not over-think it too much.
 

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They're probably right. But it still helps to try them out, and get one that feels comfortable, both when you're on it, and when you're standing over it. Bear in mind that standing over the bike on a tiled floor is different than standing on a sloping trail with rocks and roots... junk clearance is key.

And try riding some of the different configurations. Longer frame/shorter stem (fisher) will be better for more technical stuff, IMO, because the bike basically turns where you look. Shorter frame/longer stem makes for a shorter wheelbase, but I think the longer stem actually makes them feel less jittery at running speeds. Try them at speed, and in lowest gear, to see how they handle. Another FYI... lowest gear on a mountain bike is slower than a sleeping toddler. World of difference.
 

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Yea mountain bikes vary quite a good deal and what youre doing with it matters alot. For the riding you mentioned Id agree that a 17ish or M would be about right. If you arent doing any technical singletrack than id say that you should also consider a 19ish or L although this still depends on the bike geometry. Just set the saddle height so your forward leg is about 10% shy of full extension when all the way out on the pedal. After doing this just check that the bars arent strangely low or close to you. I had a friend flip over his bars and hit his head so hard that he woke up 15 minutes later and went home only to ask his mom if she was in fact his mom.... all of this happened because of a douchebag LBS wanting to get rid of a demo model and lied about the fit to a 14 year old kid. Because he needed the seat so high his center of gravity was way too high and the bars were too close. To give you an idea of how bad this was I am currently 5'6 and his bike fits me just fine although the top tube is maybe 1/2" higher than id like... yea he was like 6'2 back when he bought the bike. So moral of the story go ride them and decide for yourself. And whatever you buy im sure you'll enjoy it... mountain bikes are fun
 

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Get a medium for you and a med or small for your wife. New to mtbing? What kind of trails? I am a 29er convert and just got my wife 5-5.5" a small 29er and she likes it a lot more than her 26" bike of similar size for the fit and stability.

G
 

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acid_rider said:
Should I go by the MTB effective top tube length then? I.e. if I ride a road bike with 54cm effective top tube and 73 degree STA then I should get MTB with similar effective tube lengh and similar STA?
Yes. No.
I'm 176 tall, 84 inseam. I ride a roadbike with 54,5 TT (72,5 STA) and 110 mm stem. At the same time my MTB is Cannondale, M-size: 59,7 ETT (73,5 STA) and 120 mm stem.
So, you should get a much longer MTB in comparison to your roadbike.
 

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acid_rider said:
thank you! I was afraid you were going to say that! 8^)

yes, we are looking for entry level XC hard tail, for city and trails riding, nothing too technical, a bit of grass, a bit of dirt, a bit of pavement, a bit of road city commute, etc. First MTB, no prior MTB experience. So I dont know what to expect from MTB, even if I test ride one, having been riding a road/racing bicycle for 4.5 years.

My LBS who sold me my 54cm road bike thinks I need 17-18 inch. I might have to take their word for it and not over-think it too much.
I still think you want to try it on for size. And don't be afraid to go a little smaller than you think you need. You will want more standover clearance than your road bike because setting your feet down offroad is much different than setting them down on pavement. Also, a smaller frame enhances your maneuverability. I ride a 56cm road bike, but my hardtail is 17.5. At first I thought it was a little small, but now I know that it is "flickable", which means I can do hairpin turns & zig-zag through closely spaced trees on the trail with ease. You can always opt for a longer stem or bar-end grips if you feel the need to stretch out a bit. Both of those stategies also help place your body weight forward for doing epic climbs.

You're going to have a blast on the mountain bikes!:thumbsup:
 

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acid_rider said:
greetings all

I am thinking of buying hard-tail MTB for myself and my wife.

I ride a road bike, size 53-54cm (54cm top tube). My height is 173-174cm or 5 feet 8 & 1/2 inches or 5 feet 9 inches tall at most, inseam 83cm.

What size MTB do I need?

My wife rides a 51-52cm road bike, ~169cm or 5 feet 6 or 5 feet 7 inches tall and has 81-82cm inseam.

What size MTB would she need?

thanks!
I think a 17" frame would be too big. 18" would be way out there. I am 5' 7.5" (with a 53cm road bike) and ride anywhere from a 15" to 16.5 hardtail. I actually liked the smaller size better and almost never ride my 16.5 because I feel it's too big. A smaller frame is more nimble (agree with the other poster who said 'flickable')
 
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