Frame sizing advice 54 or 56 L or M

tonyhogg

I've currently got a scott cr1 pro premium with di2 in 54cm, not sure on my next frame what size to go for 54 or 56ish, looking at a bianchi infinito cv in 55cm, bh ultralight in 57cm, or a cipollini bond. I've tried a BMC team machine slr01 in 54 and 56 and wasn't comfortable on either really. I've also had a Specialized BG fit session which recommended me a more relaxed geometry bike not a race type with large saddle to bar drop.

I've included my measurements in competitive cyclist fit calculator:
actual inseam 84cm
trunk 61cm
forearm 34.5cm
arm 68cm
thigh 60.5cm
lower leg 56cm
sternal notch 144cm
total height 178cm

also tried wrench science
Height 178cm
sternum notch 144cm
inseam length 84cm
arm length 62cm
shoulder width 38cm
felxibility 3
weight 140lbs
fort size 9 us

Please help me understand the measurement relating to my cr1 and the new bikes I'm looking at thanks.

dwanes

You went for a BG fit session?
Surely Specialized should have answered your questions?

tonye_n

dwanes wrote:

You went for a BG fit session?
Surely Specialized should have answered your questions?

This ^^

What is your height and in-seam in Feet and Inches?
When in doubt (that is if you find yourself between sizes) always go for the smaller size. You can size up the frame (longer stem, longer crank-arm etc).

Much more difficult to size down a bigger frame without adversely affecting handling and such like.

dwanes

But, if you want a more relaxed fit then go a size up.
Going down in size will give you a larger saddle to handlebar drop.

If you are between sizes, going for the larger size will not be a problem.

styxd

Using a short stem with lots of spacers under it seems to be the fashion these days, so I would pick whichever size allows you to do that.

darkhairedlord

Frame sizes are largely irrelevant, DYOR and look them up then draw them all out, on top of each other, including your current and any bike you've tried and found comfortable. What's most critical is the stack and reach, everything else hangs off this and can be adjusted out with stem and seatpost changes.

dgunthor

never mind whether someone calls it a M, L, 54, 56 etc, centre to centre top tube length is what you want to get right

drlodge

dgunthor wrote:

never mind whether someone calls it a M, L, 54, 56 etc, centre to centre top tube length is what you want to get right

Spot on...but also factor in the seat tube angle. A 1 degree steeper STA means you need about 1cm less top tube length for the same overall effective reach.

kajjal

darkhairedlord wrote:

Frame sizes are largely irrelevant, DYOR and look them up then draw them all out, on top of each other, including your current and any bike you've tried and found comfortable. What's most critical is the stack and reach, everything else hangs off this and can be adjusted out with stem and seatpost changes.

This is the advice I would give, stack and reach give a very good guide. As long as you know what type of riding position you want the choice should be easy enough.

tonyhogg

thanks for the advice, but I'm a bit thick to be honest and stack and reach confuse me a little bit and don't get me started on degree's and angles. Based on my measurements would most people say I'm 100% a medium frame 54cm/55cm whichever they size it as, and definitely not a Large 56cm/57cm

drlodge

Your frame has an eTT length of 545mm, same as my frame but it has a STA of 74 degrees (mine is 73.5), so a little extra reach. You are only 3 cm taller than me so I would think a 56cm/Large frame will have you too stretched out. Stick with a 54/medium is my opinion based on little evidence and my hunch.

When looking at a new bike, find out the effective (horizontally measured) top tube length centre-centre. You want it to be about the same as your current frame - 545mm.

darkhairedlord

drlodge wrote:

Your frame has an eTT length of 545mm, same as my frame but it has a STA of 74 degrees (mine is 73.5), so a little extra reach. You are only 3 cm taller than me so I would think a 56cm/Large frame will have you too stretched out. Stick with a 54/medium is my opinion based on little evidence and my hunch.

When looking at a new bike, find out the effective (horizontally measured) top tube length centre-centre. You want it to be about the same as your current frame - 545mm.

it's the relationship between your butt, feet and hands that are important, so stack and reach are what you need to compare. TT length is OK if the bikes you are comparing have the the seat tube and head tube parallel to each other. Best bet is to take the diagram and geometry off the manufacturers website and compare or overlap drawings as stated above. If the OP doesn't understand the terminology he needs to read-up or just try them ALL for size.

gazman428

I only ever buy a bike after trying it. Ive been so close to buying the wrong bike on more than one occasion, different manufacturers size them differently and some have to be 4cm bigger than other manufacturers to give me the top tube length I need as I have a long torso and short legs.