How does handling change as bike size changes?

[moose8]

I can ride a 56 or 58 in a variety of bikes as I can theoretically get the same contact points. Aside from the look of the bikes, how would the handling change? I've never done a side by side comparison of a bike to see and am just curious and since this is a bike forum with amazing knowledge of these types of questions I figured I would post it here. My natural inclination is to go for the larger size bike because there's less seatpost/stem etc.

[Keith A]

I can ride a bike in the range of a 54cm to 56cm top tube and have owned bikes at both ends of this range. For the most part, I like being on the smaller end of this spectrum. I simply like the way the smaller bike feels under me. There some issues that come up going smaller in my range, such as tow overlap and the HTA is often a bit slacker. However, in the 56cm to 58cm range, I don't think you would have to deal with either of these issues.

I'm sure others can chime in and get all technical on this question, but smaller feels better to me.

Edit: BTW, if you do an Internet search of "small vs large bike frame", you'll get more than you may care to read about.

[Geeheeb]

this is pretty personal, but I like a large-for-me frame

[Keith A]

this is pretty personal, but I like a large-for-me frameVery true and I know other folks who are like you that feel better on the larger end of their scale.

[Dead Man]

I also like a smaller frame... and since I'm already small, that means TCO is more like WFO (whole foot overlap). I also have had some problems with my knees hitting the handlebars if I get a little out of sync on a sprint, and getting rake/trail dialed in seems to be even more critical, when your center of gravity moves that far forward.

One thing I've never really seen addressed is flex and tube sizing. With carbon, seems like this is possibly addressed in framebuilding... maybe in really higher-end carbon frame building anyway.. but for metal bikes, tube thickness is tube thickness. They don't use wider tubes just because they're building for a giant, so it seems to me like smaller frames should be way stiffer than bigger frames. But I'm generally thinking about this when I'm looking at my XS Ti bike leaning next to my bros' L and XL Ti bikes. I doubt there's much noticeable flex difference in just one size jump.

But since little guys can't ride huge frames and vice versa... isn't this also kinda like theorizing about sensory perception differences?

[etu]

Isn't there also change in the fore-aft distribution. Smaller frame means longer stem which means weight is centered further forward?

[sitzmark]

No "scientific" input, but I started out on a XXL (61cm C2T ST) Scott CR1, then moved to the "same frame" (different year) in XL (58) and noticed a discernible difference in lateral flex (less) in the front triangle of the smaller frame. Liked that better.

Have to make stack and reach adjustments for the smaller frame - no slammed stems w/o "tall" HT option - but have selected 57.5/58 for all subsequent frames. Horizontal top tubes give me about 1.5-2 fists of post. Slanted TTs 2.5-3.0 depending on slope.

[Charles M]

Strictly speaking, this isn't a question of "SIZE"...

It's a question about geometry...

Without knowing the geometry (especially the Head and seat angle, fork rake and wheel base), Talking "size" is talking around the real question.

[David Tollefson]

"Handling" is the result of a bunch of dimensions that can almost be completely independent of the fit of the contact points to the rider. As you stated, you can fit on a 56 or a 58 of the same model.

But think of it another way: The handling of a single model and size for two different riders won't significantly change UNLESS the weight distribution between the wheels changes. 2cm more stem, lift the seatpost up a little more, no problem. The wheelbase, front center, trail, weight distribution being the same, the handling feel will be almost identical.

What happens when you take the rider and change the size? Assume the saddle stays in the same place relative to the BB, the top tube grows, making for a shorter stem. Makers try to keep the handling similar, so maybe a steeper HTA to help keep wheelbase and FC similar, but trail decreases? Your weight distribution will change with any changes to FC and/or chainstay length. Can't say for sure whether it'll be more ponderous or twitchy (note: I intentionally used the "negative" terms for the opposing ends of the handling spectrum). The sum of the changes will tell the tale.

[Mark McM]

One thing I've never really seen addressed is flex and tube sizing. With carbon, seems like this is possibly addressed in framebuilding... maybe in really higher-end carbon frame building anyway.. but for metal bikes, tube thickness is tube thickness. They don't use wider tubes just because they're building for a giant, so it seems to me like smaller frames should be way stiffer than bigger frames. But I'm generally thinking about this when I'm looking at my XS Ti bike leaning next to my bros' L and XL Ti bikes. I doubt there's much noticeable flex difference in just one size jump.

Metal bike builders have varied tube sizing (diameter, wall thickness) according to bike size for a long time. If you look at the tube sets available from the tube manufacturers, you'll see that they often offer the same tube (say, down tube or seat tube) in both different diameters and different wall thicknesses, and even sometimes in different cross-sectional shapes. A good bike designer will select the appropriate tube sizes for the frame. Dependiing on joinery method, a designer may even select different tubes from completely different tube sets.

[Dead Man]

Metal bike builders have varied tube sizing (diameter, wall thickness) according to bike size for a long time. If you look at the tube sets available from the tube manufacturers, you'll see that they often offer the same tube (say, down tube or seat tube) in both different diameters and different wall thicknesses, and even sometimes in different cross-sectional shapes. A good bike designer will select the appropriate tube sizes for the frame. Dependiing on joinery method, a designer may even select different tubes from completely different tube sets.

Are you talking custom? I've ever noticed any tube diameter differences in factory bikes, with different sizes... but I've also not really looked that hard.

[Charles M]

Most top shelf models will have differentiated tube sizes and wall thickness for different size...

That's mostly an equalizer though.

The geometry is the important consideration and that will also vary by size and model...

The key isn't a generic difference in SIZE...

You need to determine what kind of handling you like and determine what Geometry gives you that...

And it will be different for different people...


This thread is a bit of a trick / misleading question...

[stuckinthecity]

Proper fit isn't decided in numbers.

You're not going to know unless you build up each bike using the contact points, and ride each for several hours. You might surprise yourself and find that you have a very strong opinion in the end. Take your time, for there is indeed a difference between two adjacent bike sizes.

Just about anything is endurable for a two hour ride. But by hour six that nice stretch in your shoulder, lower back and pelvis that you started out with on the larger frame at the beginning of the day might turn into sharp pains by the time the ride is over.


My natural inclination is to go for the larger size bike because there's less seatpost/stem etc.

[Mark McM]

Proper fit isn't decided in numbers.

You're not going to know unless you build up each bike using the contact points, and ride each for several hours. You might surprise yourself and find that you have a very strong opinion in the end. Take your time, for there is indeed a difference between two adjacent bike sizes.

Just about anything is endurable for a two hour ride. But by hour six that nice stretch in your shoulder, lower back and pelvis that you started out with on the larger frame at the beginning of the day might turn into sharp pains by the time the ride is over.

Why would you have a "stretch in your shoulder, lower back and pelvis" on the larger frame if you set up the contact points the same on both frames?

[jimcav]

i've ridden 54 to 58, and the obvious stuff is most apparent INDEPENDENT of frame size--fork trail and HTA on the handling quickness or stability, short chain stays or shorter wheelbase-- these are more theoretical impacts as I honestly don't think i can ride hard enough to notice a difference in turning for a change in wheelbase, but i definitely climb a bit better with shorter stays (having moved same wheels and same gearing on several bikes).

[MesiJezi]

I recently moved down from a 58 (slightly large) to a 54 (slightly small). I'm really digging the 54. Obviously "twichyness" is more of a function of fork rake and head tube angles... but the smaller bike feels more nimble and controllable. I also prefer the look of a longer stem and more seatpost showing... but that's not performance related.

Drawbacks--possibility of toe interference with the front wheel on the smaller size. Easier to hit the chainstays with your heels on the smaller size.

[Peter P.]

Since the OP is specifically mentioning sizes 56 and 58cm, I'll focus on what I usually see as changes in geometry as the frame size increases, particularly in these two sizes.

I think the biggest change you'll experience will be a difference in front end handling. For some reason manufacturers try to keep the wheel base similar across a range of sizes and one way they do that is by increasing the head angle. At the same time they decrease fork rake in an attempt to keep the trail numbers similar. Steeper head angles mean faster handling bikes so in many (but not all) cases the larger size will have quicker steering; at least that's my experience.

[fuzzalow]

In strict terms of looking at the frame geometry specs between adjacent-sized frames, there won't be a lot of difference, in millimeters, between two frames. So I do not attribute handling changes on a bike to some overwrought idea & belief that those millimeters in geo, trail and whatever mumbo jumbo chassis spec brings tumult in a difference to how a bike handles.

It isn't the bike. It is what you do with it. How you fit into it which, as consequence, effects the style and manner in which you ride it. It is down to the all important way in which where the rider weight is carried along the wheelbase of the bike and how between the contact points the rider's weight is distributed.

I have done this on sizing down from a 56 Colnago c40 to a 54 Colnago c50. This was done after the c40 didn't work out so well because I emphasized the wrong parameter in choosing the frame size. I had been gravitating my fit & position to long 'n' low and I went with a 56 in prioritizing toptube length chasing the "long" part of that equation. It was the wrong choice. So after struggling with that fit for a while and failing I figured to have a go with prioritizing the next frame on the "low" part of the equation. That put me back on the track in the right direction and contributed another puzzle piece I learned about fit & position theory.

I never gave any note to overlap with the front wheel - it's not material except in low speed which is of marginal importance to what is worth considering in choosing a new ride as a race bike.

That's the background. To finally answer the OP, handling changes due to frame size is impossible to answer because how the frame really works is wholly dependent on how it is used. The misnomer "easy as riding a bike" is very damaging. Don't get D-K'd with answers in cliches. There's a lot of skill involved in sport cycling. And the millimeters matter but it depends on when and where these millimeters apply to know if they will drive a result in something that actually matters.