Frame Size
 

I am shopping for a new bike. The online fitting tables suggest 56 cm frame for me. I am 5’ 10” 32” inseam.

I am sure this is just a starting point and 54 or 58 might be better for certain situations.

What would make me choose a larger or smaller frame that normally recommended for my size?

Following

Experience.

Knowing how you felt on a particular size frame for several thousand miles and then trying other size frames to see what that does for you.

Larger frame might keep you more upright or allow you to get more stretched out.

Smaller frame will generally let you get more drop from saddle to bars and with longer stem just as stretched out as the larger frame. You probably can't get as upright with out the stem being ridiculously angled up.

After riding excessively large frames (64, 60, 59cm) for over 45 years, I'm on a 56 cm Tarmac since this March. Very comfortable right out of the shop. The only thing I changed was putting short cranks on it. I'm 5' 11" with 34.5" legs.

Seems like starting with standard size is best for me until I have more experience.

I am also 5'10", and my inseam is 33". 56cm bikes seem a bit large to me, I prefer the nimble feel (in my opinion) of the 54 or 55cm bikes. The decision is also related to the type of roads and riding you plan to do. This all is a matter of opinion, but short quick turns and rides, smaller bike; longer rides, bigger bike. Try different sizes if you can.

When people state the frame size, you really need to find out how they measured it. Generally, the seat tube length is easy to adjust - just raise the seat up or down. The top tube length is more difficult - you can alter stem lengths, slide the seat fore and aft, and/or change the reach on the handlebars.

I second this.

I'm also 5'10" with a 33" inseam and prefer 53/54cm bikes. 56 cm bikes felt a little stretched out for me but I also prefer to run about 8.5 - 9 cm of saddle to handlebar drop. Similar to cyclic eric's comment, make sure to check out the geometry and compare reach/stack along with the top tube for the bikes you're looking at.

It seems sizing varies from one bike company to another. Specialized and Trek guide me toward 56 cm. But Ridley towards 53.5.

What is your intended use? I am 5'10" with a 32cm inseam, and went with a 56cm Surly LHT, which has rather long top tube, over the smaller 54cm, because I wanted to have the bars level or slightly above the seat. I am able to do that with the 56 easily. On the 54, I would have to have a ridiculously high stack of spacers to do that. The longer frame is also more stable at speed, especially when loaded. I know of people who have stability issued with the LHT when loaded on fast descents. I do not. My bike is dead on stable even when loaded, and when I was commuting on it, I hit 40mph on a daily basis on downhills in the Ozarks, sometimes 45mph when pushing it. One day I hit a chunk of concrete on that downhill, and kept riding. The rim had damage, but the bike remained stable. Wheelbase has an advantage, it also rides a little better.

Your needs may be different, and as someone else pointed out, a smaller fame can be more nimble. Wheel size makes a difference too. The 56 LHT with 700 wheels is less nimble than the 56 with 26 inch wheels. I went with the 26 inch wheels. If you want to run more drop, a smaller frame can work.

When comparing frames, look also at the effective top tube length. There will be differences between frames "of the same size."

Probably Specialized and Trek are measuring from the BB center to a imaginary horizontal line coming from the top of the head tube (or there abouts) intersecting the seat post.

Ridley might be just measuring to the intersection of the top tube with the seat tube as we did back in the days when most all bikes had a horizontal top tube.

Sizing varies even among different models from the same manufacturer. Don't assume because a 56 cm Émonda SLR 7 is recomended for your size, that a 56 cm in another model Trek is correct for you.

I think stability and ride comfort will be more important to me than nimbleness.

Greg Lemond says you should ride a 53 cm frame. Go ride a few. If it’s too small you’ll feel cramped, if it’s too large it will hurt. Most people ride a frame that’s too large then complain. You should feel one with the bike.

:rolleyes:

I am leaning toward the 56 cm frame at the moment since less drop from seat to handle bars appeals to me.

But it would seem this would also depend on the bike geometry. Looking at endurance and gravel bikes that already have more relaxed geometries and longer wheel base maybe a smaller frame would work. I wonder if a 54 cm frame on a Roubaix might fit similarly to a 56 cm frame on a Tarmac.

When you look at drop from saddle to bars from one model to the next, don't just look at stack height in the geometry specs. Many bike come with a lot of spacers under the stem that if not removed will leave a bike marketed as a "Race" fit just as relaxed as a bike marketed toward something else.

Trying them on is the best way to figure it out and having the experience to look for stuff like that. But also, maybe make certain you don't buy such an expensive bike that you can't afford another if this turns out to not quite be the one.

You should honestly ride each bike to see what you like.

Like another poster noted, most bikes come with quite a few spacers underneath the stem to dial in fit. Generally endurance frames have the handlebars closer and higher due to reduced reach and increased stack over a "race fit" frame.

That is what I would like to do. The issue is that local shops are not doing test rides. You can buy a bike. Ride it and return it if you do not like it. I am considering doing this, but I would really prefer to ride one right after another for a better comparison.

My existing bike works fine for the way I am riding now. I will probably just wait until things get back to normal.

The question is not correct. Each frame has its own geometry. Geometry of pure race and endurance bike is different. So often You can be fitted well on 56cm endurance frame or 54cm race frame. Now let me share my personal experience. My hight is 172cm. When I visited LBS to buy bike shop owner loooked at me and told: “You need 54cm. If You are going to participate in races buy 52cm.”

The question is not correct. Each frame has its own geometry. Geometry of pure race and endurance bike is different. So often You can be fitted well on 56cm endurance frame or 54cm race frame. Now let me share my personal experience. My hight is 172cm. When I visited LBS to buy bike shop owner looked at me and told: “You need 54cm. If You are going to participate in races buy 52cm.”

Personal proportions vary. Frame designs vary. One thing remains constant - saddles and bars can go up and down. So buy a frame by the effective top tube (ETT) length, not by the nominal frame size. Competitive Cyclist's calculator will give ETT.
https://www.competitivecyclist.com/S...ulatorBike.jsp

I wouldn't buy a bike without throwing a leg over it. I'm 5' 11'' with a 32" inseam. A previously-owned Bottecchia 57cm road bike felt a bit compact. In a pinch I recently borrowed a buddy's 15 y.o. 54cm Sirrus and it felt really small. My current 2016 Scott hybrid is an XL. Other than the standover height being a bit higher than I'd prefer, the frame is a good fit.

I have decided to wait to buy a bike until bike shops open for test rides. Perhaps more experienced riders would be able to know how the bike would fit based on geometry but at my experience level I think I need to try it out. Even then I probably won’t really know until I get some miles under my belt.

Considering the possibility of getting a used bike to ride for a while and get some experience on a particular size and geometry to get a basis for comparison.

I have a hybrid and MTB. The MTB has an aggressive fit. Maybe a bit small for me. Riding them is giving me some perspective of what I am looking for. But I would really like to get some experience on a drop bar bike.

I went through 3 used bikes before I bought my first new one, rode a double on one of them. So I had a good idea of what felt right. I bought the new bike after testing it on the bike shop's trainer, and of course reading many reviews. I knew the bike I wanted and the size before I went in the shop. IIRC they changed out the stem for me. It's the only new bike I ever bought, still ride it 20 years later. You never know, you might buy a used bike, like it, and never buy a new one.

I think using their trainer with an employee to help me with fit was a much better experience than taking the bike out on the road. It's much easier to focus down on fit issues on a trainer instead of being totally wowed by the new fast bike experience on the road. Which of course I totally had after the purchase.