Frame size... Go larger or smaller?

CECB

What’s good.
I’m looking to drop some money on a new bike and want some advise towards purchasing a frame size. I’m stuck between a “size small” Giant TCR Advance and a “medium”.

These are my measurements
Actual inseam: 32.5
Trunk: 24
Forearm: 12.5
Arm: 23
Thigh: 21.5
Lower leg: 21.5
Sternal notch: 58.5
Total height: 68
In inches

A bike calculator says I should ride a 530mm top tube.
Top tube on a “M” is 550mm with a stem length of 100mm (what I’ve been basically riding but with a 90mm stem)
“S” is 535mm with a 90mm stem.
Will going a frame size down as the calculator suggest benefit me that much?
I do feel a bit twitchy with my set up now as far as steering goes on descent.

Any help would be appreciated.
Thanks in advance.

bristolpete

Tricky one. I used to right a Medium large giant as I loved the fit and felt great on it. Walked into a Giant shop and was hammered by all the staff there as I was clearly a medium according to the Giant size chart and fit parameters. I tried to reason that my body is bigger than my legs and explained that I liked the ML fit that to me was akin to my old Tarmac bikes. But in the end, I decided to sell on and bought a medium based on their advice. However, within a week or two I hated riding it. Felt too small, too cramped and a diddy bike which actually robbed me of power - could hardly wind the bike up in a power sprint up a gradient. So binned that and spent the summer regretting being a push over. As that bloke from US of A says on Youtube fit n feel are two different things.

Ride what you feel is right. What I perhaps should have done is knocked 10mm off my stem as a starter for 10, but panicked cleared the decks and now ride a good bike, but I still feel that nothing can touch the TCR as the perfect do it all modern road bike and might, just might buy one in the new year ....

cougie

Err on the smaller side. You can't fix a bike that's too big.

SJH76

bristolpete wrote:

As that bloke from US of A says on Youtube fit n feel are two different things.

I couldn't agree with this more. I have always ridden bikes that so called professional sales people or fitters say was too big for me and I should be on a smaller frame but I too always felt more comfortable and able to generate more power and speed out of it. Some twunt will come along and scoff at my setup saying it doesn't look right etc etc etc but those are the guys I usually smash past on rides so I don't care. I've always gone off instinct rather than letting someone else decide. No one knows your body better than you.

super_davo

I can''t make out the measurements you're quoting, but it is as a rule much easier to make a slightly too small bike grow to fit you than a slightly too large bike shrink.

If you're using a 90mm stem that's pretty short for a road bike; I've got 130mm on two of my bikes and 110s on others, so you can go much longer, might help the twitchiness on descents. Theoretically you should get a more comfortable ride with more seatpost showing like you'd get on the smaller size, especially if carbon. Flip side is that running loads of spacers under the stem looks a bit rubbish and might lose a bit of front end stiffness. If you're between sizes then all of this will be marginal.

In terms of the "feel" effect between sizes, that can really only come from geometry. The smaller size has a 1 degree slacker head tube and a slightly shorter wheelbase - the former will make the bike feel more stable, the latter more responsive. They've done this so the effects offset each other to attempt to make all sizes handle and feel the same, therefore if they've done their job right you shouldn't get any "feel" improvement with the larger size.

Ericshun

You’re in between sizes. Small will give a more responsive ride, medium will feel more relaxed. If you get it from a Giant dealer, they will do a ‘power fit’ to tweak the bike in to better suit you.

SJH76

super_davo wrote:

In terms of the "feel" effect between sizes, that can really only come from geometry. The smaller size has a 1 degree slacker head tube and a slightly shorter wheelbase - the former will make the bike feel more stable, the latter more responsive. They've done this so the effects offset each other to attempt to make all sizes handle and feel the same, therefore if they've done their job right you shouldn't get any "feel" improvement with the larger size.

But if you buyer smaller frame and compensate by putting a longer stem on for reach that is most definitely going to effect handling - probably more than any other adjustments you could possibly do. There is also another problem and that's mainly with the manufacturers. Some brands offer many various frame sizes so finding the best between a 53cm and 55 might be quite easy to compromise. But others out there (and Giant are one of them) offer far fewer frame options in the range so the step between two potential frames could be slightly over ideal size or very under ideal size and no matter of stem and saddle adjustment is going to make it feel comfortable.

sloppyschleckonds

super_davo wrote:

I can''t make out the measurements you're quoting,

Agreed, decide if you are going metric or imperial

gary_sparrow

And the other problem going small could be potentially the bar height is too low even with spacers . Hello neck pain !

animal72

I had the same problem as you when I bought my Condor.
Ended up getting them to set up their fitting rig to the same settings as each bike, including spacers/stem length to suit.

I went for the bigger bike in the end as the front was too low for me (I'm old) on the smaller one.

rwoofer

Like others have commented, I focus on stack first to determine whether a frame will fit, since many frames are just too low in the stack for me (even though I ride with a 9.5cm saddle to handlebar drop)

javanman123

Agreed I would go small every day of the week. you can adjust saddle, stem, etc. I have had many to small and too big bikes and the worse of the two was by far the ones that were too large.

StillGoing

Buy small and make it fit. Buy big and regret it.

SJH76

Best way to go is to just try a bike or 2 and go from there. Going small is more often than not a default option but as most experienced riders know there is no such thing as a simple one size fits all answer to things. As many including myself have shown going small isn't always the guarantee you can 'just make it fit' . If you are 5'8" - 5'11" things seem to be pretty simple but if like me your not the tallest or on the flip side you're a beanpole things get a bit trickier to size up. No one is the same, 2 people the same height could have very different torso, leg lengths - that will effect stand over height, reach and many there variables. Don't take the default answer as Gospel.

dj58

Can you not get a Giant dealer to set up both sizes for you to try back to back? I was in a similar position to you when I bought my Defy, I preferred the medium bike.

vegasfoster

You can't fix too small if you are kicking the front wheels. You can't fix too big if you can't stand over the dumb thing. Stay away from those two extremes and you can usually find something workable, if not ideal, with different seatposts and or stems/handlebars. May have to buy a few to get there and you may not look as cool as you had dreamed possible.

StillGoing

vegasfoster wrote:

You can't fix too small if you are kicking the front wheels. You can't fix too big if you can't stand over the dumb thing. Stay away from those two extremes and you can usually find something workable, if not ideal, with different seatposts and or stems/handlebars. May have to buy a few to get there and you may not look as cool as you had dreamed possible.

You're going from one extreme to another there. If the rider is going to struggle being able to put a standing foot down while off of the saddle, then the bike is far too big. If the rider is going to be kicking the front wheel, then they're in a slow and extreme turning arc and probably have too long crank arms. I ride two bikes that are erring on the small size and fit perfectly. In a tight turning circle, I can easily kick the front wheel. Its just an unfortunate circumstance if you're on the short side riding a small frame and use full size wheels.

SJH76

philthy3 wrote:

vegasfoster wrote:

You can't fix too small if you are kicking the front wheels. You can't fix too big if you can't stand over the dumb thing. Stay away from those two extremes and you can usually find something workable, if not ideal, with different seatposts and or stems/handlebars. May have to buy a few to get there and you may not look as cool as you had dreamed possible.

You're going from one extreme to another there. If the rider is going to struggle being able to put a standing foot down while off of the saddle, then the bike is far too big. If the rider is going to be kicking the front wheel, then they're in a slow and extreme turning arc and probably have too long crank arms. I ride two bikes that are erring on the small size and fit perfectly. In a tight turning circle, I can easily kick the front wheel. Its just an unfortunate circumstance if you're on the short side riding a small frame and use full size wheels.

Same here. My Madone is a size 52 with 170mm crank arms the toe overlap is probably my only criticism of the bike. I believe the previous version of the specialized Venge was bad for it too. So it's not something you can judge a bike size on. The more bikes you see with the wheelbase getting increasingly shorter it's an inevitability

StillGoing

SJH76 wrote:

Same here. My Madone is a size 52 with 170mm crank arms the toe overlap is probably my only criticism of the bike. I believe the previous version of the specialized Venge was bad for it too. So it's not something you can judge a bike size on. The more bikes you see with the wheelbase getting increasingly shorter it's an inevitability

I'm a 520mm virtual top tube, but I went down to a 47cm Reacto and Ride for a much better fit. Playing with the stem lengths still gives me the same virtual top tube length with the benefit of an increased seat to bar height, better room for the hips coming over the top of the pedal stroke using 165mm and 170mm cranks. I can still toe strike the front wheel when turning around in the road.

CECB

Thanks for all the reply’s.
Looks like I’m gonna have to travel a bit as my local dealer only has a Medium and couldn’t adjust the saddle when sitting over it.
Not gonna lie, I have felt like I’ve been riding to large of a bike for some time. But every damn shop I go to always wants to put me in a “medium” size bike. Can’t get over the fact a bike calculator says I should be on a “Small” size frame.
Sorry about the measurements guys, I understand how that can confuse some. Had me confused when I had to convert it.

Actual inseam: 32.5 inches = 825.5 mm
Trunk: 24 inches = 609.6 mm
Forearm: 12.5 inches = 317.5 mm
Arm: 23 inches = 584.2 mm
Thigh: 21.5 inches = 546.1 mm
Lower leg: 21.5 inches =546.1 mm
Sternal notch: 58.5 inches = 1485.9 mm
Total height: 68 inches = 1727.2 mm

If I knew how to post photos on here I would post the bike frame calculators suggestion and Giants bike frame size chart for comparison.
Maybe some of you guys better with geometry and stack could tell me what’s best.

StillGoing

As shops tend to pre-order and stock the most common size frames, finding a small frame size usually incurs a special order unless you're lucky. I had years of dealers pushing me to medium frames they had in stock. Wasn't until I went for a fitting with Mike at Bike Dynamics in 2010, that I got all of my measurements recorded and knew what was right and what was wrong.

keef66

A decade ago I wanted a particular winter bike. Bike shop sat me on a 54 based on my height, but I have long legs / short torso, so it felt too stretched out.

So they bought in the 52 frame and built that up. Long legs meant more seat post out, and a big saddle to bar drop, so I have it with a flipped stem and several spacers. Looks a bit ungainly, but it's a perfect fit and all day comfy.

Summer bike in contrast I chose a less racy geometry with shorter TT and more stack, so the 54 is spot on and I don't need the stem flipped.

TLDR: try them both.