If in between two sizes, is there a general preference for going smaller or bigger?
I’m a 5’5 woman with a 31.5 inseam. When looking at bike companies’ sizing charts, I pretty much always end up in the “overlap area†anywhere between 48 to 52 (some bikes even going to 54).
I have been riding on the road anc dirt competitively, riding 50-52cm road bikes (currently on a Felt 51cm, a 52cm scott cx bike and a scott medium mtb which all feel great). I have an old cervelo size small on which I’ve done occasional TTs that seems to work but they were always short TTs.
As I’m switching to triathlon (long distance) and looking for a nw bike, my natural inclination was to go with similar sizing and I was more specifically looking at the Felt ia and Scott plasma in size Small.
That said, reading about “pro bikes†to get some ideas, it seems that pro women triathletes who are my size are typically more on 48cm / XS bikes and girls on Smalls are much taller… I know a bike fit is individual but I was wondering if there’s a general rule of thumbs about going with smaller?
I’ve tried both, I am not used enough to the position to say which one feels the worse.
I guess it means that there is no terribly wrong answer but I’d be grateful for advice.
When i first asked this a few years back I was told “more machine is better†and to size up if all things and fit were equal.
I am in between Medium and Large for a speed concept. I’m going with the medium after discovering that the large doesn’t allow the arm pads to be positioned lower (if by chance I want to do that in the future). In addition, the arm pads are positioned behind the steer tube, to accommodate my reach. I don’t like it esthetically, or from a handling standpoint. IMHO, I’d go smaller, but I’m far from an expert in this arena.
Can you get a solid test ride in on both bikes?
If not, in this case, I would go smaller. You have the same inseam that I do, but I’m a bit over 6’. A smaller bike will allow you to get lower which is likely to be more aero. If you don’t need to get super low, depending on equipment choice, you would be able to pedestal your bars, which is more aero that a big head tube.
My question won’t help the OP but I’m curious - why are two pad pedestels more aero than one longer headtube?
I’m a competitive cyclist and I have the same measurements as you. I ride 51cm Cervelo road bikes (w/170 cranks) and 48cm TT bikes (w/165 cranks). Each size has worked great for me. Remember you can modify and fine-tune your desired fit with varying stems and saddle positions, etc.
My question won’t help the OP but I’m curious - why are two pad pedestels more aero than one longer headtube?
I don’t know enough to know why. I think I saw it in a test posted on this forum a couple of years ago. My surmise is that the two pedestals present less frontal area. iirc, there was some speculation about getting the base bare in front of the knees. But I’m just not 100% sure.
Unfortunately, I can’t. I’ve only been able to do short test rides; too short to really assess and also not able to really tweak the fit. I’m flexible enough that nothing feels terribly wrong and because I’ve been used to be on larger rather than smaller bikes, they feel more “natural†which doesn’t mean that they are the best options. I’ll try to figure a way to borrow or rent a 48cm; I have an old 51cm cervelo P2 so I know it works, at least on short TTs (and from what I understand P2s size “largeâ€) but I want to see how I’d be on a smaller size.
Thanks. That’s helpful.
As a rule of thumb, generally smaller is better than bigger. Assuming it’s traditional stem (not integrated), it’s possible to reasonably make a small bike “bigger” for fit purposes in terms of reach and stack. Can also raise the saddle height. On the other hand, it’s nearly impossible to make a big bike “smaller.” Additionally, generally speaking, the injuries that come from riding too “big” a bike can be far worse than injuries that come from riding too “small” a bike. Just my two cents, FWIW and YMMV.
If in between two sizes, is there a general preference for going smaller or bigger?
I’m a 5’5 woman with a 31.5 inseam. When looking at bike companies’ sizing charts, I pretty much always end up in the “overlap area†anywhere between 48 to 52 (some bikes even going to 54).
I have been riding on the road anc dirt competitively, riding 50-52cm road bikes (currently on a Felt 51cm, a 52cm scott cx bike and a scott medium mtb which all feel great). I have an old cervelo size small on which I’ve done occasional TTs that seems to work but they were always short TTs.
As I’m switching to triathlon (long distance) and looking for a nw bike, my natural inclination was to go with similar sizing and I was more specifically looking at the Felt ia and Scott plasma in size Small.
That said, reading about “pro bikes†to get some ideas, it seems that pro women triathletes who are my size are typically more on 48cm / XS bikes and girls on Smalls are much taller… I know a bike fit is individual but I was wondering if there’s a general rule of thumbs about going with smaller?
I’ve tried both, I am not used enough to the position to say which one feels the worse.
I guess it means that there is no terribly wrong answer but I’d be grateful for advice.
if the fit is not the problem: smaller=lighter
One thing I’d add is to consider whether the type of bike you’re looking at - is more ‘long and low’ or ‘tall and compact’, if that makes sense. I’m 5’2" and change, but have a long torso. My 2 Felt bikes (size 47 and 45) feel pretty good, my Lapierre (46) I think is borderline short front-to-back… you start to feel like the front wheel is way under you instead of out in front. Additionally, something I didn’t discover till later, is I have a wicked toe overlap issue on the Lapierre. Like, turn the wheel 1.5" in either direction and bad things are going to happen if your foot’s in the wrong place. Might not be an issue if you don’t have a lot of 180-degree turns to negotiate, but I do and it’s a pain in the ass. If you’re borderline, the bigger frame should mitigate that problem somewhat.
Which size is better will depend on the bike.
For the Felt IA we were told in the IA thread by superdave who used to work at Felt that you should get the largest frame that fits. For the Felt IA the larger frame will be more aerodynamic. I ended up choosing a 54 IA10 over a 52.
For other bikes smaller could be better. Its tough to tell without testing them.
I know a bike fit is individual but I was wondering if there’s a general rule of thumbs about going with smaller?
New bikes tend to have high stack. I’m 6’ with a 33.75" inseam and I’d ride a 51 in a new Cervelo just to get the stack right (horizontal stem with low stack bars).
To get optimal adjustability + aero I think a small frame with good bars that pedestal and tilt the pads and extensions is the way to go.
Also depends on how you prefer a bike to handle.
Larger frame with a short stem will handle a bit twitchy compared to a smaller bike with a longer stem which will have more of a flow to the handling. This might explain in a bit better: https://youtu.be/B69I_uayeMA
One thing that I see constantly ignored is weight distribution when people talk about “fit” on a bike. Fit is more than just your contact points, it’s how the entire bike PLUS the rider work as a unit – where your CG is in relation to the wheels, and how that weight distribution interacts with the bike’s geometry. Going smaller will often get more weight on the front wheel, which isn’t always a good thing.
I’m in between a 52 and 54 on a Specialized road bike. I tried both and they both felt okay, so I’m not sure if there was a right and wrong one. Someone told me that the conventional wisdom is that a smaller frame is better because it’s stiffer, but I don’t know if that’s true of modern carbon frames, or of frames where the tube diameter changes with frame size.
I went with the smaller frame. For me, the only downside is that in a tight turn, like making a 180 on a narrow bike path, my shoe can touch my front wheel, which could potentially lead to a flop. That’s with a midfoot cleat mount, though.
A lot depends on the integration of the front end, or lack of.
If it is one of the older carbon P2s, then it is a longer reach and lower stack bike than the new P2s. The 51cm older P2 actually measured the same as the older carbon 51cm P3.
On the new P2, you would be a 48cm to get the same/similar stack, but the reach would be about 2cm shorter. If your fit is close to perfect and everything else was the same (bars, aerobars, saddle, cranks), you would need a 2cm longer stem on the 48cm new P2 to get your current fit.
I was once told that your bike will always be more aerodynamic than your body, so if the fit works then size up if in-between sizes. Good luck!
My question won’t help the OP but I’m curious - why are two pad pedestels more aero than one longer headtube?
Drag is a function of Cd * A. The Cd of an airfoil(s) is going to be about the same, but the width of the headtube is going to be probably at least 1.25 inches to fit a headset bearing in there. The width of each pedestal is about 1/4". You make the fat part of the front end , which is the headtube, as short as possible. Then add the skinniest pedestal you can to minimize A. The Sky Pinarellos with the Ti 3D printed bars are a good example.