I am sized in the grey area between 54/56 cm for sizing. My 2017 Roubaix was a tad big and had to change the stem down – even then the reach was long. In every other way, the sizing was correct. I am strongly leaning towards a 54 cm for the Tarmac. It “might” be a little small? Any insight on sizing from the forum?
Road bikes: smaller frame longer stem
Mountain bikes: larger frame, shorter stem
Most of the time
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I wonder how the smaller bike and longer stem affect handling.
Less twitchy/more leverage/more modulation. I was in the same boat and got a 54cm Emonda, over time I bumped the stem up to 110mm from 90 and the bike feels super smooth. Larger frame with shorter stem will handle twitchy-er especially out of the saddle.
Very helpful. Thanks.
My n=1.
I had a 56 De Rosa and has to go to 54 on my Tarmac.
I’m in the grey area as well. I have a 54cm 2020 Tarmac but I’m running a super short 70mm stem, though I may be changing that soon.
Is the stack adjustable on the 2021 Tarmac – doesn’t look like it.
Frame stack is not adjustable, AFAIK. Just the typical stem spacer option like most other bikes.
Anybody know how many stem spacer options, it doesn’t appear to accommodate any.
Don’t trust the website pictures. They just show those in the lowest and racy looking setup per usual roadie fashion.
All their bikes ship with a longer steer tube on the fork, and something like a minimum of 20mm of spacers under the stem at stock. They expect people to dial in the stem height they want, and possibly cut the steer tube to final height as desired.
For reference, here is the fully stock steer tube on a new Aethos, 61cm. My friend set the 5mm spacer on the bottom and there is 20-25mm of spacers on top. We did this so he can do a few rides, make sure the height he likes and then chop the steerer to make it all “pretty”.
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Thanks Chad. Picture has a integrated stem so I was a little confused.
After overthinking everything, I will have to travel, but found a 54cm Tarmac Expert. So, I will “road trip” to pick it up. Specialize will not permit the shops to ship. I will swap out the wheelset for CL50’s.
Note that the stem is designed to allow the steerer through it, like a “normal” stem, for temporary or long term use, as needed.
The bike ships with spaces like any other bike, can be added or removed, and then cut as usual.
Very helpful Chad. It seems from the video that you can lower but can you raise the stack? Sorry, if I am missing something.
You can start at the max for the steer tube they provide, which is about 20-30mm above the head tube. Going higher would require swapping to a different stem with rise.
Thanks Chad for your thorough help and assistance. I am looking forward to picking up the bike tomorrow.
If you think you’re between two sizes, always go for the smaller one.
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Picked her up today. 8 hour drive and then back. Beautiful bike. 54cm was perfect. Thanks for everyone’s help.
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Pics or it didn’t happen!! 
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Saddle will be replaced. Wheelset will be swapped for my Roval CL50’s. I will wait until I can get Aerofly II handlebars and replace the bars eventually.