spencertimm

Hi all - new here so hopefully this is in the right forum. I am searching for a new bike and I need a higher stack/lower reach (read: endurance) bike. However, I’m also considering sizing down. I have always ridden size 58 (my previous bike was a Synapse and my current bike is a Giant TCR), but my bike always feels a little big and I’ve had to decrease my stem length to 80 mm or so. I figured I’d check here whether there are any downsides to choosing a smaller frame size. I am 74 inches tall with a 34.5 inch inseam for reference.

thanks!

Iride01 

Saddle height is the one thing that will be pretty much the same distance for you on most any bike you ride of the same genre of bike (road bike to road bike, mountain bike to mountain bike, cruiser to cruiser, etc).

What will affect you when sizing down on the same model of bike is that the frame stack will be lower and you will have more drop from the saddle when at it's correct height to the handlebars. To a lesser extent you might be cramped with your knees to close or your reach to the bars too close. Depends on the exact model of bike and how they scale the geometry for other sizes.

I'm 71" tall with a 34.5" inseam. I use to ride a huge 25" Schwinn from the 70's comfortably, then sized down to 60 and 59 cm bikes from those vintage days. I now ride a 56 cm Specialized Tarmac and wonder what a 54 cm Tarmac will have been like.

That would mean 21mm (≈.8") more bar drop for me that I could make up in spacers under the bar if I didn't like the drop, but the bars would probably look silly high on that bike. A 54 cm Specialized Roubaix with no spacers under the stem will probably give me the same saddle to bar drop that I have now on my 56 cm Tarmac with 15 mm of spacers under the stem.

So when you size down you might need to consider changing to a different model of bike if you can't deal with the increased bar drop for your position.

Welcome to BF!

cyclezen

This ^^^
A TCR is their low stack/performance race geometry model. Go with more 'upright' endurance model/geometry in any brand, if you want shorter reach.
You're right in the zone for the 58ish geo , and going to a 56ish isn't going to do anything, except give you a lower stack - sometimes as much as 2 cm... seat angle is almost always the same for both sizes, so your seat location will be the same, fore/aft, given the same height setting.
Ride On
Yuri

qwaalodge

Downsizing will also likely have smaller stack so might go against your preferred setup but you can always have the steerer tube longer and add spacers under to raise the stack.

But assuming the stack did not change, shorter reach tends to improve comfort so downsizing isn't bad at all. The only possible problems with downsizing is toe strike and if the reach is too short, your knees might be banging the handelbar.

TdF pros tend to use downsized bikes. I know we shouldn't be copying pros but if you have to downsize for any reason, then go for it.

cloudswimmer

I’d add keep an eye on toe overlap with a smaller frame .. if that’s something that would bug you.

beng1

There are lots of old road bikes laying around that can be had for pocket-change. Buy one in the size you want to try and fiddle with it. I did this a year ago and found that I have probably been riding a too-big frame most of my life. I am a hair under 6'3". I can do most all riding with a 25" frame very well, but I have found that an inch smaller frame has benefits in fast riding positions and comfort.