Help me out here – bike fit help

I am currently riding a medium giant trance x and always feels slightly cramped on it.
The way that its been run at the moment is the stem on top of 20mm of spacers – this makes the effective head tube the same length as a large frame i think.
The seat is central on a layback post – the bike came with a layback so that should be fine.

Am i right in thinking that even if i swapped the frame for a large i would be in the same place albeit with the seat 25mm further forwards towards the bb?

essentially – if i buy a large will i have more space/better pedaling postition?

Can you try one for size- may be the frames just don't fit you that well..

Simples…

Assuming you set the seat height the same (bb to top of seat),
and seat set back the same (distance seat is behind bb). You would acheive this just by dropping the post 2" in the bigger frame.
These are the two most important for proper pedalling dynamics.
And assuming you loose the 20mm head spacers;
You would end up with your lower body in exactly the same position and the bars at the same height BUT 25mm further away (Effective top tube).
hth

no thats the problem 🙁
current medium is naggingly to small

Do you mean cramped as in that you aren't stretching out to the bars enough, like upper body cramped, or seat too low/far over bb in a lower body cramped way ?

stanley
thats what i am struggling with – if i am more over the bb will i be more/less efficient pedaling than

Essentially i am getting lower back ache when pedalling in the saddle too long – reach seems fine with a 90mm stem. Just cannot seem to get the saddle in the right place 🙁

i seem to remember the 'correct' riding position is with your knees directly over the BB when theyre at 90 degree to you hips (if you know what i mean). think i read it on sheldon brown once?

i think you are mistaken ben – iirc you knee (ish) should be over the pedal spindle at 90 degrees – 3 o'clock position

ah, yeah that could be it! its been a long time and i always fiddle with my seat position 🙂

I suspect you will find the large is too large, i went through the same thing when looking at the Trance X, medium was too cramped, large was too stretched, they really need a M\L in there like they do on the road frames, i bought something else in the end.

What height are you?

6ftish

top end of medium bottom end of large 🙁

The way that its been run at the moment is the stem on top of 20mm of spacers – this makes the effective head tube the same length as a large frame i think.

Playing with the spacers under your stem will only make marginal differences, if you leave it all as it is, but just tried an unfashionably long stem on it say 120mm, it would give you a better clue as to if the large would fit you better..

sadly, you cant turn a medium into a large, you could really do with trying one out somewhere.

try tilting your saddle nose down – you may be bending in your back rather than tilting your hips and keeping the back straight(ish)

Have you ever been able to ride the distances your talking about without pain ? – i only ask because i know many folk who blame bike position and size only to ask them that question and find they are doing a 100km off road ride on a base of riding 20km twice a week … and wonder why they are sore

Will have a fiddle with seat height and position later tonight i think. With a 90mm stem the reach feels right. No excess weight on my hands.

There is quite a lot to get your pedalling position right. Not just height etc.
Shin / thigh length, cleat position, flexibility, type of riding, etc.

Quick method: Assuming you are happy with cleat position already, and sag is set up about right (or lock out front and rear first if poss.)
1)Get seat height right… with heel on pedal, leg should be locked out straight when pedal is at lowest position (in line with seat tube).
When you move foot to normal position, this should give you a slight bend at the knee.
2) Get seat set back right… sat on bike in normal riding position, cranks horrizontal. Drop a plumb line down from just below your knee cap. This should go through or behind the pedal spindle. In front is not generally a good idea. Move seat back and forth to get this right. Big adjustments and you need to re check seat height.

This is fairly basic, but will get you very close to your ideal seat position. Bar reach height comes after imo !

You need a helper to get it right really. Happy to have a look if you are in the Holmfirth area, or if I'm over your way.

thanks stanley that is a great help – on last nights ride i fiddled with shock pressure also so that may have had some bearing. You know when you have a nagging doubt!!
Will have a look tonight and see whats what 🙂
Thansk again

I confused as to what you want?

If you buy a large frame your saddle to crank relationship would be identicle given your using the knee over the pedal thing as a start point, but with the large you would be increasing the stretch as its the TT length that grows.. Yeah OK the hadtube does grow too, but only to match the height of the seat tube, raising the headtube and seatube wont make the bike feel any larger just more on top of it.

Thats two of us 🙂

I think i need to sort my seat height/position (fore/aft) and rear shock pressure first