Polygon Siskiu T8 Geometry, Sizes & Bike Fit

Polygon Siskiu T8 geometry (2026), compare stack, reach, and every supported size, then open the TrainCraft calculator with this bike preselected.

Supported sizes

S, M, L, XL

Family

cross-country geometry

This bike is tuned around efficient climbing, technical handling, and a compact off-road cockpit.

What to compare

Stack, reach, setup

Use this guide to compare stack, reach, and XC cockpit assumptions before choosing a frame size.

Check my size with measurements Compare geometry first View original geometry source

Quick size check

What Polygon Siskiu T8 size fits you?

Get an instant frame estimate, then continue into the full fit report to check cockpit reach, bar drop, and setup risks before you buy.

No account needed for this check. The full report keeps this bike preselected.

What you get after the size check

A complete setup now. A Fit Passport when you sign up.

A paid report unlocks the complete setup and print-ready PDF for this bike. No account is required. Create a free fit profile separately to save and reuse your fit.

Paid report for this bike

Compare every size and get saddle position, cockpit coordinates, stem, spacers, bar width and crank length. No account required.

Print-ready PDF included

Export the paid report as a clean A4 PDF to keep, print or take into the workshop when this bike is being set up.

Free Fit Passport for ongoing fitting

Create a free fit profile to save measurements and reports across devices, prefill new fits, recalculate after profile changes, fine-tune by symptoms and get the lower in-app report price.

Check my size and see my options

Geometry and size breakdown

Use the geometry table as context, then enter your measurements above before opening the full fit report.

Size	Stack	Reach	Top tube	Head tube	Stem	Crank	Size check
S	604 mm	440 mm	568 mm	89 mm	45 mm	170 mm	Check with my measurements
M	609 mm	465 mm	595 mm	95 mm	45 mm	170 mm	Check with my measurements
L	622 mm	485 mm	619 mm	110 mm	50 mm	175 mm	Check with my measurements
XL	636 mm	505 mm	644 mm	125 mm	50 mm	175 mm	Check with my measurements

How to use this guide

Start with the size table to narrow the geometry range you actually want. Then open the calculator to compare that geometry against your body dimensions, flexibility, and fit priorities.

The TrainCraft bike fit tool models saddle height, cockpit reach, and bar drop using the frame geometry plus stock cockpit assumptions for the Polygon Siskiu T8.

That is more useful than a generic height chart because two sizes can both fit your height while requiring very different stems, spacers, or saddle positions.

FAQ

What sizes are available for the Polygon Siskiu T8?

TrainCraft currently tracks these Polygon Siskiu T8 sizes: S, M, L, XL. The calculator uses each size's published geometry and stock cockpit assumptions to compare fit outcomes.

Can I use the TrainCraft calculator for Polygon Siskiu T8 sizing?

Yes. Open the calculator from this page to preload the Polygon Siskiu T8, then compare sizes against your body measurements, fit priorities, flexibility, and riding posture preferences.

What should I compare on the Polygon Siskiu T8 before picking a size?

Start with stack, reach, effective top tube, and the stock stem/crank setup. TrainCraft uses those numbers to estimate cockpit reach, bar drop, saddle position, and how much adjustment headroom each size leaves.