MTB size up or down

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MTB size up or down

Post by Elizabeth_S »

I'm looking for a hardtail bike, with 27.5" wheels, I want to do some bikejor with it and I might do some off-road but nothing serious downhill. So I don't want to pay a massive amount for it, but obviously I'm a bit flexible and will pay more if I need to (but want so stay under £850). I've looked a second-hand and while there are some good ones-ish out there, I'm not sure or confident enough to by second hand and there is the size problem.
The problem that I'm running into is that I'm 5ft 7 (168 cm), 30" inside leg, average reach, which puts me mid size in many bike ranges (womens and unisex), I'm either a S/M or a M/L depending on the sizing. Normally this wouldn't be a problem as I'd go along to a reputable bike shop and try a few, but they don't have many bikes in stock and I live north of the central belt in Scotland.
I've been told that it is better to go for the smaller size as it is easier to make a small bike bigger than a big bike smaller, is that true? Anyone have any useful size tips for models that will help me.
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Re: MTB size up or down

Post by Jdsk »

Elizabeth_S wrote:I've been told that it is better to go for the smaller size as it is easier to make a small bike bigger than a big bike smaller, is that true?

I agree with that: you can raise seats and slide them back and and you can push bars further away and fit bits to them.

But it's still nowhere near as good as trying it out... sorry that's currently so difficult.

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Re: MTB size up or down

Post by PT1029 »

If you have a similar(ish) bike, even if not 27.5" wheels, you could measure that. Once you have the measurements, you have a reference point against which to judge any online bikes (which usually have a geometry chart somewhere, be it on the seller's website or the manufacturer's website).
You can then make an informed judgement as to whether the bike is a good fit, or if adjusting/changing stems etc is possible.
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Re: MTB size up or down

Post by Stevek76 »

I'm not sure I'd fully agree with a size down is always safe, it's easier but with the risk that the handlebar height is too low and, since built bikes almost always have the steerer tube cut down quite short, isn't easy to put higher. For the size up then the length is the potential problem, particularly as the trend in present mtbs is to maximise reach & effective top tube via a short stem.

Agree with the use a reference point suggestion. I had to buy without trying out recently due to the present shortage and did a similar thing. I stumbled across this site: that has a fairly extensive database plus a geometry comparison tool so used my old mtb as a reference.

There might be better tools around. I had to account for the handlebar position manually as that site does not consider that part and reach/ETT/stack of course only measure to the top of the head tube.
The contents of this post, unless otherwise stated, are opinions of the author and may actually be complete codswallop
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Re: MTB size up or down

Post by Dizzie »

I have an app called SizeMyBike, I am just under 5’4” with 29” leg which was proving a tad difficult and that has been reliable at stating what size road and MTB to look at. I bought a hardtail off Wiggle, gave them my measurements and it arrived a perfect fit if that is any help.
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Re: MTB size up or down

Post by mumbojumbo »

A smaller bike will flex less and is more resilient.
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Re: MTB size up or down

Post by Wenagade »

There's a few perhaps very few descent MTBs in small size that house 29 inch wheels.

That makes the difference & rolls more comfort, though 27.5 are a good wheel size.

I use bike geometry geeks website & a longer stem & setback saddle.

There's some great ebay second hand bikes for that price range, you just have to scroll threw hundreds to find the odd jem & selecting bike size parameters only excludes half the bikes from search so better to just look @ many.

Just haven't got the 29 inch bike, not yet.
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Re: MTB size up or down

Post by iandusud »

I would say that it is better to opt for the smaller of two sizes if you are in between sizes for the reasons already mentioned. However be careful if tempted to to choose a smaller option if you are at or over the recommended size limit. I made that mistake when I had the chance to buy a full sus Giant at a very reasonable price. It was too good to pass up, the only problem being that I was really at the limit on size. It was size M, which according to Giant was for a rider up to 185cm, which is my height. However I always felt too cramped on it and was constantly sliding off the back of the saddle. In the end I sold it on.
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Re: MTB size up or down

Post by Nearholmer »

Have you ridden MTB before?

I ask because at the tender age of 62 I’d never ridden one and bought a secondhand one (29er) to use on bridleways that are so rough and steep that a CX bike feels too harsh and over-geared.

What I’ve found is that the stance, fit and sizing is massively different from a generally road-ish shaped bike. After much fiddling with fit, messing around with stem lengths, and progressively cutting down the length of the bars, it now works for me.

Long way round of saying that if you’ve never ridden one before, and are used to other shapes of bike, use any available means (hire, borrow, I won’t suggest steal) to get a feel for the geometry before spending big money.
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Re: MTB size up or down

Post by tenbikes »

We dabble in bikejor and find that bike geometry is more significant than traditional ideas about fit.

Modern slack HT is good,as is long TT and short stem.

A 'nippy' old school MTB isnt a good platform for bikejor.

We are near Kinross.. Where are you?
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Re: MTB size up or down

Post by colin54 »

This is a two year old thread.
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Re: MTB size up or down

Post by tenbikes »

:) not now it isn't...

But point taken....
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Re: MTB size up or down

Post by 531colin »

Every days a schoolday! I just Googled bikejor
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