If you’re considering the Cannondale System Six, the detailed size chart below provides a starting point for selecting your ideal frame size.
According to Cannondale, the System Six is designed with an aggressive frame geometry for racing, while ensuring riders achieve a balance between comfort and aerodynamic efficiency.
This design puts you in a lower and more extended riding position. From my experience, this bike might not suit the everyday rider. Alternatively, you can consider the all-rounder and lighter Cannondale Supersix EVO.
According to Cannondale’s sizing chart, there are seven frame sizes tailored for riders between 5’3″ to 6’9″ (160 to 205cm).
| Bike size | Rider height (in) | Rider height (cm) |
|---|---|---|
| 47 | 5’3″ to 5’7″ | 160 to 170 |
| 51 | 5’5″ to 5’9″ | 165 to 175 |
| 54 | 5’7″ to 5’11” | 170 to 180 |
| 56 | 5’10” to 6’2″ | 177 to 187 |
| 58 | 6’0″ to 6’4″ | 182 to 193 |
| 60 | 6’2″ to 6’6″ | 187 to 198 |
| 62 | 6’5″ to 6’9″ | 195 to 205 |
Important things to consider
Selecting the right size involves more than matching your height to a frame size. Here are important things to consider based on my experience of buying and owning many bikes in the past.
Brand-specific sizing
While the Cannondale System Six comes in seven sizes from 47 to 62, it’s important to remember that sizing can vary between bike brands.
For instance, you can ride a size 51 Cervelo S5 but not necessarily a size 51 Cannondale System Six. From my experience, it’s best to compare the stack and reach measurements instead of just the size labels.
Understand the stack and reach measurements
From my experience, the Stack and Reach are the most critical measurements to ensure the ideal bike fit.
If you already own 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 Cannondale System Six’s measurements. Then, pick the closest size.
- Reach is the horizontal distance from the bottom bracket to the center of the head tube. It affects your riding posture, with a longer reach offering a more aggressive stance and a shorter one providing a more relaxed position.
- Stack is measured vertically from the bottom bracket to the top of the head tube. The stack height determines the relative height of your handlebars to your saddle. A higher stack offers a more upright position, ideal for extended rides and riders with lower back flexibility concerns.
Things get trickier if you don’t currently own a bike. In that case, use the chart above as a starting point and consult your local bike shop. Alternatively, consider getting a professional bike fit. The bike fit report provides you with a Stack and Reach measurement, which you can use as a reference.
What to do if you fall between sizes?
It’s common to fall between two bike sizes for the Cannondale System Six.
If you’re having this dilemma, 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.
Having said that, generally, I’d recommend sizing down for most cyclists.
A 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.
A 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 long legs with a shorter torso, consider sizing up to avoid having too much exposed seatpost. The Cannondale System Six seatpost is relatively short at 330mm and have a minimum insertion length to ensure safety.
- If you have short legs with a longer torso, consider sizing down and using a longer stem to extend reach.
Go for a test ride
Always try before you buy. Visit a local Cannondale dealer, test different sizes, and find the one that feels right. Reputable dealers often offer test rides, especially if they have your size available for a demo.
Cannondale System Six frame geometry (2018-2023)
The geometry chart below applies to all Cannondale System Six models from the following:
- Years: 2018, 2019, 2020, 2021, 2022, 2023
- Models: LAB71, Hi-MOD, 1, 2, 3, 4
- Frame material: Carbon
The frame geometry measurements are explained in this article.
| Frame Size | 47 | 51 | 54 | 56 | 58 | 60 | 62 |
|---|---|---|---|---|---|---|---|
| Rider Height (cm) | 160 to 170 | 165 to 175 | 170 to 180 | 177 to 187 | 182 to 193 | 187 to 198 | 195 to 205 |
| Rider Height (ft) | 5’3″ to 5’7″ | 5’5″ to 5’9″ | 5’7″ to 5’11” | 5’10” to 6’2″ | 6’0″ to 6’4″ | 6’2″ to 6’6″ | 6’5″ to 6’9″ |
| Stack (mm) | 500 | 520 | 540 | 560 | 580 | 600 | 620 |
| Reach (mm) | 375 | 381 | 386 | 392 | 398 | 403 | 409 |
| Top Tube, Horizontal (mm) | 514 | 529 | 544 | 560 | 576 | 592 | 609 |
| Seat Tube (mm) | 385 | 433 | 482 | 530 | 553 | 577 | 600 |
| Seat Tube Angle | 75.1° | 74.7° | 74.3° | 73.9° | 73.5° | 73.1° | 72.7° |
| Seat Tube Angle Effective | 74.5° | 74.1° | 73.7° | 73.3° | 72.9° | 72.5° | 72.1° |
| Head Tube (mm) | 88 | 114 | 128 | 149 | 172 | 193 | 214 |
| Head Tube Angle | 71.2° | 71.2° | 73.0° | 73.0° | 73.0° | 72.9° | 72.9° |
| Standover Height (mm) | 680 | 723 | 762 | 798 | 821 | 843 | 863 |
| Wheelbase (mm) | 974 | 989 | 975 | 987 | 1000 | 1012 | 1024 |
| Front Center (mm) | 582 | 595 | 581 | 593 | 605 | 617 | 629 |
| Chainstay (mm) | 405 | 405 | 405 | 405 | 405 | 405 | 405 |
| BB Drop (mm) | 79 | 74 | 72 | 72 | 69 | 69 | 69 |
| BB Height (mm) | 261 | 266 | 269 | 269 | 271 | 271 | 271 |
| Fork Offset (mm) | 55 | 55 | 45 | 45 | 45 | 45 | 45 |
| Fork Trail (mm) | 58 | 58 | 57 | 57 | 57 | 58 | 58 |
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.