2023 Specialized Tarmac SL8 Size Charts and Guide

In this article, our road bike specialist Bernard Lu guides you on how to find your ideal Specialized Tarmac SL8 size.

Experienced cyclist turned writer with 7+ years working in bike shops, overseeing retail and workshop operations.

This sizing guide helps you find your ideal Specialized Tarmac SL8 size.

The Tarmac SL8 retains the same geometry as its predecessor, although there is a difference in the stack and reach measurements. Upon further inspection, I found the SL8 and SL7 indeed have the same geometry, taking into account two new measurements, Stack to Stem and Reach to Stem.

Rouleur’s review of the SL8 also confirms this finding.

There are seven Specialized Tarmac SL8 frame sizes for cyclists from 4’8″ to 6’5″ (142 to 196cm). Both S-Works and non-S-Works versions have the same sizing and apply to both male and female cyclists.

Bike sizeRider height (in)Rider height (cm)
444’8″ – 5’1″142 – 155
495’1″ – 5’4″155 – 163
525’4″ – 5’7″163 – 170
545’7″ – 5’9″170 – 175
565’9″ – 5’11”175 – 180
585’11” – 6’2″180 – 188
616’2″ – 6’5″188 – 196
Specialized Tarmac SL8 size vs rider height chart. Source: Specialized

Important factors to consider

S-Works Tarmac SL8 SRAM Red eTap AXS (Red)
S-Works Tarmac SL8 SRAM Red eTap AXS (Red)

There’s more to a good fit than height beyond the sizing chart. Here are important things to consider from my experience working at the bike shop selling Specialized bikes.

Specialized sizing vs. other brands

Specialized sizes their bikes such as 44, 49, 52, 54, 56, 58, and 61.

These numbers provide a general indication of the frame size. However, they may not be consistent across other bike brands. What constitutes a size 52 in a Specialized could be different in another model with a similar sizing, such as Cannondale Supersix Evo or Trek Emonda.

Understand the stack and reach measurements 

If you’re upgrading from the Tarmac SL7, remember to double-check the stack and reach measurements. The Tarmac SL8 has a higher stack (+10mm) and shorter reach (-3mm) compared to the Tarmac SL7.

If you currently have a bike that fits you well and is comfortable, use that as a reference point. 

Find out its Stack and Reach measurements and compare them against the Tarmac SL8’s measurements. Then, pick the closest size.

  • Stack is the vertical distance from the bottom bracket to the top of the head tube. Stack height influences how high your handlebars will be relative to your saddle. A higher stack leads to a more upright riding position, which can be more comfortable, especially for longer rides, older riders, and those with less flexibility on the lower back.
  • Reach is the horizontal distance from the bottom bracket to the center of the head tube. It determines how stretched or compact your riding position will be. A longer reach results in a more stretched-out, aggressive riding posture, while a shorter reach promotes a more upright position.

The Stack and Reach measurements can be found in the geometry chart below.

Size up or down, if in between sizes?

Compared to other brands, the sizing for Specialized Tarmac SL8 is relatively easy. However, there will be some cyclists that fall right on the upper end of the smaller size and lower end of the larger size.

If that’s you, there are many things to consider, such as your legs-to-torso proportions and the final look of the bike, taking into consideration the number of spacers, stem length, and the amount of exposed seatpost.

Generally, I’d recommend sizing down (go for the smaller of two sizes) for most cyclists.

Here’s why. 

The smaller frame has more room to extend reach, and increase stack. It’s easier to make a smaller frame bigger than vice versa. However, there is a limit to these corrective measures to avoid having too many spacers (30mm+) or too much exposed seatpost, which makes the bike look out of proportion.

The smaller frame is also stiffer, more maneuverable, and marginally lighter. If set up right, it’ll have more exposed seatpost, leading to more comfort due to increased seatpost flex.

If you have a normal legs-to-torso proportion, opting for the smaller size would be a better choice.

  • If you have longer legs with a shorter torso, consider sizing up to avoid having too much exposed seatpost.
  • If you have shorter legs with a longer torso, consider sizing down and using a longer stem to extend reach.

Test ride before you buy

Visit your local Specialized dealer to try both sizes. Most Specialized dealers can provide a test ride if they have a bike in your size in their demo fleet. Specialized also conducts a bike demo day annually for you to try out their bikes.

Specialized Tarmac SL8 frame geometry (2020-2023)

S Works Tarmac SL8 Stack and Reach
S Works Tarmac SL8 Stack and Reach

The geometry chart below applies to all Specialized Tarmac SL8 frames from the following:

  • Years: 2023
  • Models: S-Works, Pro, Expert
  • Frame material: FACT 12r carbon (S-Works), FACT 10r carbon (Specialized)
Frame Size44495254565861
Rider Height (cm)142 to 155155 to 163163 to 170170 to 175175 to 180180 to 188188 to 196
Rider Height (ft)4’8″ to 5’1″5’1″ to 5’4″5’4″ to 5’7″5’7″ to 5’9″5’9″ to 5’11”5’11” to 6’2″6’2″ to 6’5″
Stack to stem (mm)509522535552573599620
Reach to stem (mm)363372377381393400406
Stack (mm)501514527544565591612
Reach (mm)366375380384395402408
Top Tube, Horizontal (mm)496509531541563577595
Seat Tube (mm)433445456473494515545
Seat Tube Angle75.5º75.5º74º74º73.5º73.5º73º
Head Tube (mm)99109120137157184204
Head Tube Angle70.5º71.75º72.5º73º73.5º73.5º74º
BB Height (mm)266266266268268268268
BB Drop (mm)74747472727272
Fork Trail (mm)71635858555552
Fork Length (mm)370370370370370370370
Fork Offset (mm)47474744444444
Front Center (mm)572574577579592606613
Chainstay (mm)410410410410410410410
Wheelbase (mm)97097397597899110061013
Standover Height (mm)723735746768786808834
Stem Length (mm)801001107090100110
Seatpost Length (mm)300380380300300380380
Specialized Tarmac SL8 (2023) frame geometry chart. Source: Specialized
Bernard Lu at Mr.Mamil

Bernard Lu has 7+ years of experience working in a bicycle shop, overseeing the retail and workshop operations. He’s a qualified bicycle mechanic who understands a cyclist’s needs and speaks the same cycling lingo.

If you meet him at the cafe, he will happily talk to you for hours about all the intricacies of bikes and cycling tech. Just buy him a coffee next time you see him.