Bike sizing total confusion

itboffin

I'm totally confused about choosing the right size frame, I currently have both 54cm & 56cm road frames which both feel just fine to ride, I have a full sus mountain bike that's 17in (43cm) and a hybrid that's 19in (48cm) all the online buyers guides suggest mountain bikes should be 10cm smaller.

Isn't that a lovely mix of sizes both imperial and metric, but really how the hell do I choose a new hardtail MTB frame?

This one is doing my head in, its a full sus pogo stick no matter how I set up the preload and rebound controls, after today's brown trouser morning ice ride I need to answer this question before next weeks commuting starts again.

This frame and me are no more

whyamihere

I just go for any MTB frame between 17" and 19". Seems to work for me. 6' tall, 33" inside leg.

Aidy

I seem to think you're about my height, and I'm normally on 17" mountain bike frames (also have 54cm and 56cm road bikes).

Sizing is a hard thing though, and it varies from manufacturer to manufacturer.

What are you thinking of?

cjcp

ITB - I've got a 19in Spesh Rockhopper.

Is your 54cm the Dolan though?

itboffin

I was thinking of a NOS 18.5 Kinesis XC frame, sort of in the middle.

@cjcp yes the Dolan is 54cm, I'm still amazed at how well such a cheap frame handles adding a Cane Creek BB really made a difference to.

MichaelW

If you have a bike that fits, you need to measure your points of contact. To avoid difficulties with frame angles, stick to a simple [x,y] coordinate system, with the bottom bracket at [0,0]

The point of contact for the saddle is probably the saddle nose and for the bars I use the point where the web of my hand meets the bars. If your not from Norfolk and hence, lack webbed hands, I cant help.

Pick a new bike that can be tweaked to these points of contact using normal amounts of seatpost and stem. The most critical aspect is effective top tube length. Some styles of bike favour more TT and less stem.

Jay dubbleU

MTB is 19" and CX is 56 - seems to work OK for me. Saddle on the MTB is set lower that the CX though. I'm around 6ft. I used this to calculate in the first place

http://www.tiemeyercycles.com/fit.htm

itboffin

That's for the advise all, i've gone for the quickest and cheapest solution of converting my hybrid into a NO SUS mountain bike



Might put the DMR flats back on, with all this ice around I like to know I'm not going to have a clipless moment whilst panicking.

nicklouse

MTB sizes mean bugger all. they only give a guide to the ones either side of it in that model from that maker.

you will, if you take it further, to look at the numbers. top tube and other things can make or brake a ride.

but as I , and others say, got your butt on as many as you can to see what is right for you and your riding and then take a punt at what you like that has similar numbers.

tailwindhome

itboffin wrote:

That's for the advise all, i've gone for the quickest and cheapest solution of converting my hybrid into a NO SUS mountain bike



Might put the DMR flats back on, with all this ice around I like to know I'm not going to have a clipless moment whilst panicking.

Is that a tin of Schweppes Tonic water strapped to the seat post?

Fireblade96

If you ride a 54cm road bike then 16.5-17" hardtail MTB should be just about perfect, if you actually want to ride it off road. If it's just for use on the road then you can get away with a slightly bigger frame, but you won't have the standover height (ballroom ;-)) you might want for offroading.

Of course, this depends entirely on whether you're as perfectly proportioned as me

itboffin

WheezyMcChubby wrote:

itboffin wrote:

That's for the advise all, i've gone for the quickest and cheapest solution of converting my hybrid into a NO SUS mountain bike



Might put the DMR flats back on, with all this ice around I like to know I'm not going to have a clipless moment whilst panicking.

Is that a tin of Schweppes Tonic water strapped to the seat post?

Yes, what of it? :oops:

itboffin

Off road is a must otherwise what would be the point of having a MTB? anyway after today mixed ride of smooth and rough on/off road/trail/path etc I can't help thinking that drops would be much more comfortable, do people have mountain bikes with drop bars? and I don't mean CX bikes.

MonkeyMonster

thats not a tin of tonic water...

thats a tin of premixed g&t - the height of the can gives it away...

Fireblade96

No drops on the MTB, they'd get in the way too much. If it's just for the hand position, go for some bar ends - which, although currently out of fashion, are great for riding longer distances and climbing too.

jejv

Fireblade96 wrote:

No drops on the MTB, they'd get in the way too much. If it's just for the hand position, go for some bar ends - which, although currently out of fashion, are great for riding longer distances and climbing too.

Personally, I don't get bar ends - if I had them I think I'd want them where I'd want hoods - 42cm ish appart for me. Which would usually get in the way of the controls, with "straight" bars. But then I'm not exactly a hardcore MTBer.

Here's someone who likes an MTB with drops:
http://mtbtires.com/features/bikes/why_dropbars.html

And someone with bar ends that aren't at the end:
http://www.crazyguyonabike.com/forum/bo ... =59978&v=I

supersonic

Fireblade96 wrote:

If you ride a 54cm road bike then 16.5-17" hardtail MTB should be just about perfect, if you actually want to ride it off road. If it's just for use on the road then you can get away with a slightly bigger frame, but you won't have the standover height (ballroom ;-)) you might want for offroading.

Of course, this depends entirely on whether you're as perfectly proportioned as me

Maybe in some cases it will be just about perfect, but more often than not it wont be. MTB sizes vary so much, and as nick says, are generally justy a way of differentiating one model size from the next. The seat tube length is one of many factors.

There is a guide to sizing in the MTB buying section, stickied at the top. Someone saying I am x height and ride y size frame is nigh on useless I am afraid.

itboffin

Here's something else I've noticed, by chance all my saddle to BB heights measure 74cm, don't know why, because I didn't set them up that way, I just tried different heights on each bike until it felt comfortable and so happens that 74cm works for me.

Anyway I stuck the new commuter at 74cm rode half a mile and had to drop the saddle 2cm, feels just fine, odd or what!?

Fireblade96

itboffin wrote:

Here's something else I've noticed, by chance all my saddle to BB heights measure 74cm, don't know why, because I didn't set them up that way, I just tried different heights on each bike until it felt comfortable and so happens that 74cm works for me.

Anyway I stuck the new commuter at 74cm rode half a mile and had to drop the saddle 2cm, feels just fine, odd or what!?

It's cos your @rse has got bigger over Christmas, seating you further away from the pedals!

:twisted:

itboffin

Fireblade96 wrote:

itboffin wrote:

Here's something else I've noticed, by chance all my saddle to BB heights measure 74cm, don't know why, because I didn't set them up that way, I just tried different heights on each bike until it felt comfortable and so happens that 74cm works for me.

Anyway I stuck the new commuter at 74cm rode half a mile and had to drop the saddle 2cm, feels just fine, odd or what!?

It's cos your @rse has got bigger over Christmas, seating you further away from the pedals!

:twisted:

Watch it young man or i'll set the dogs on you :P