frame size...which?

Si78

hi all,
newbie who is waiting to buy his first good mtb thru cycle 2 work scheme.

my question , and im sure its probably a stupid one, what size frame should i choose? when i went down to halfords they didnt have the boardman sport, gt aggressor or kona fire mountain i was looking at in all the sizes available, and i didnt get chance to ride any.
quite difficult anyway because the bike bit is upstairs, which i think is a bit daft
so,
im 6 ft tall (183cm),

arm span is 5ft 11in (180cm), so according to one internet sizing guide i looked at im a 'negative ape' because my arm span is less than my height... apparently this means i should go down a size from the 'ideal frame size'

distance between the floor and my 'BARSE' (in trainers) is 34" (86cm).

sizing guides say you take 3" off the inside leg measurement to allow for cross bar clearence (sloping top bars on modern mtb's makes that fairly meaningless i reckon), and then take off another 10" for the distance between the ground and the bottom bracket.

that puts my 'ideal' frame size at 21", which i think is too big. ive ridden my mates GT, which is an 18" frame (he is a couple of inches shorter than me), and it felt ok...seat just needed to be raised a bit.

basically, after boring you all with all this waffle!, i want to know what size frame all you good people (of a similar size to me ) use...

ive always thought that having a smaller frame would make a bike more nimble. is this true?
and lighter too i guess!

are there disadvantages to buying a slightly smaller bike? how much does the length of the bike / wheelbase etc change in relation to the size of the frame?

most of my riding during week will be riding to work, with some off roading / xc at the weekends.

thanks in advance for any views offered, it will be really appreciated!
si

captainfly

I'm 6'2" with legs long enough to make buying trousers a pain and ride an 18" frame, more to do with toptube length than seat height (you can always lift you seat up), personaly I'd always air on the smaller side, so I move about on it more or tuck right in. But it depends on you riding style and how you feel comfortable.
What sort of riding are you planning on doing? I you are going to ride to work on the road and leave your bike locked up at work then a cheap (under £50) second hand roadbike that will be a nicer ride (tall close gears, fast rolling tyres, ligher weight) that you won't be upset if it gets nicked and save your mountain bike for off road riding and properly enjoy it

dave_hill

Si78 wrote:

What size frame should i choose?

I'm 6 ft tall (183cm), arm span is 5ft 11in (180cm)

distance between the floor and my 'BARSE' (in trainers) is 34" (86cm)

Take your trainers off, measure your inside leg (crotch to floor) properly.

Rule of thumb is that your frame size should be your inside leg minus 14". So if you're inside leg (minus trainers) is 33", you're looking at 19".

Personally I'd drop another inch if you feel that you have "short arm" syndrome. THat in itself is unusual for a bloke (assuming you are a bloke of course!!) because most men have short legs and long torso proportionately, where women are the other way round (long legs and short torso).

Try lots of frames of your chosen size as they can vary in length too depending upon manufacturer. Of course, if you can't find an ideal solution you can always swap the handlebar stem or move the saddle to find an ideal riding position

Si78 wrote:

basically, after boring you all with all this waffle!, i want to know what size frame all you good people (of a similar size to me ) use...

Don't go off what other people use - concentrate on what's right for you. For example, you sound to be a similar build to me. But I prefer a smaller frame and an upright, rearward bias riding position. You may not.

Si78 wrote:

ive always thought that having a smaller frame would make a bike more nimble. is this true?

Usually

Si78 wrote:

and lighter too i guess!

Yes, but it's usually such a small difference it's hardly noticeable.

Si78 wrote:

are there disadvantages to buying a slightly smaller bike?

Not really, except that a smaller frame will be stiffer and therefore may be more harsh to ride compared to the larger version. But don't obsess about smaller frames. Again, try lots and choose the right one for you.

Si78 wrote:

how much does the length of the bike / wheelbase etc change in relation to the size of the frame?

How long is a piece of string? It varies from bike type to bike type and manufacturer to manufacturer. There is no hard and fast rule.

It's like cars - you can have a 2 litre Fiesta ST or a 2 litre Imprezza - they're both cars, they both have the same sized engine, but they're vastly different!!

Si78

captainfly wrote:

I'm 6'2" with legs long enough to make buying trousers a pain and ride an 18" frame, more to do with toptube length than seat height (you can always lift you seat up), personaly I'd always air on the smaller side, so I move about on it more or tuck right in. But it depends on you riding style and how you feel comfortable.

cheers for answering captain fly:) if you can comfortably ride an 18", and you are a couple of inches taller than me with longer legs, then i should have no problem on an 18 incher. i reckon i would definately feel more in control on a smaller, more manouverable steed

captainfly wrote:

What sort of riding are you planning on doing? I you are going to ride to work on the road and leave your bike locked up at work then a cheap (under £50) second hand roadbike that will be a nicer ride (tall close gears, fast rolling tyres, ligher weight) that you won't be upset if it gets nicked and save your mountain bike for off road riding and properly enjoy it

ive not really got the room for 2 bikes i can see your point tho. work has good security tho...security guards, long covered bike sheds, cctv, security patrols, gates with card entry... dont think it will get robbed there, and it will be properly insured too.

cheers, si

Si78

dave_hill wrote:

Take your trainers off, measure your inside leg (crotch to floor) properly.
Rule of thumb is that your frame size should be your inside leg minus 14". So if you're inside leg (minus trainers) is 33", you're looking at 19".

hi dave, cheers for reply yes, my inside leg floor to crotch without trainers is 33".

dave_hill wrote:

Personally I'd drop another inch if you feel that you have "short arm" syndrome. THat in itself is unusual for a bloke (assuming you are a bloke of course!!) because most men have short legs and long torso proportionately, where women are the other way round (long legs and short torso).

yes im a chap, thought the reference to my BARSE (balls/arse) was a clue .i read on the sizing section on wiggle.co.uk that if your arm span, finger tip to finger tip, was shorter than your overall height you should drop a size.

dave_hill wrote:

Try lots of frames of your chosen size as they can vary in length too depending upon manufacturer. Of course, if you can't find an ideal solution you can always swap the handlebar stem or move the saddle to find an ideal riding position).

you are totally right, no substitute for getting on bikes and trying them for size. only problem is that not all halfords have the entire range of bikes on display (i have been looking at boardman sport mtb) so it is difficult to directly compare frame sizes. gotta get from halfords cos it does our cycle 2 work scheme.

dave_hill wrote:

Don't go off what other people use - concentrate on what's right for you. For example, you sound to be a similar build to me. But I prefer a smaller frame and an upright, rearward bias riding position. You may not.

body shape wise im not at all freaky, except for my belly and moobs lol, but they will be consigned to the history bin after a few weeks of riding i will definately go for the option that increases manouverability and control. (even when im driving my car im more 'rally driver' than 'racing driver')

Si78 wrote:

how much does the length of the bike / wheelbase etc change in relation to the size of the frame?

dave_hill wrote:

How long is a piece of string? It varies from bike type to bike type and manufacturer to manufacturer. There is no hard and fast rule.
It's like cars - you can have a 2 litre Fiesta ST or a 2 litre Imprezza - they're both cars, they both have the same sized engine, but they're vastly different!!

yeah, i asked a bit of a silly question didnt i lol :oops: the boardman sport mtb im looking at has an 'effective top tube' length difference of 2.5cm between the 18 & 20" frames...bugger all really.

seat tube length is 5cm different between the 18 & 20", so can easily raise the seat height on the smaller one


cheers for the help buddy, i will take your advice and try and get halfords to dig out both size bikes so i can directly compare
thanks
si

supersonic

Have a read of this too:

http://www.bikeradar.com/forums/viewtop ... sc&start=0

Si78

supersonic wrote:

Have a read of this too:

http://www.bikeradar.com/forums/viewtop ... sc&start=0

cheers supersonic... didnt notice that thread :oops: i should have looked harder 8)

im thinking 18" boardman sport... gonna trot down halfrauds for a look and play asap

i think the medium will be fine, more manouverable and better proportioned.

just didnt want to look like 'a performing monkey on a miniature bike' lol