Uploaded August 2026 | Updated September 2026, 2 weeks ago
0Are your rims too wide for your tyres? The cycling industry is obsessed with pushing internal rim widths wider and wider, but what does that actually mean for your handling, aerodynamics, and safety?
In this quick tech deep-dive, we cut through the latest wheel trends to look at the physics of road bike tyres. We explain the difference between "Tyre Squish" (good) and "Tyre Squirm" (bad), why the Rule of 105 matters for aerodynamics, and why putting a 28mm tyre on a 30mm internal rim will ruin your bike's handling. Whether you are racing, riding all-road, or just looking for maximum comfort, here is how to find the perfect tyre and rim combination without wasting money on trial and error.
⚙️ Nerd Notes from the Video:
The Rule of 105: Popularised by Josh Poertner (Silca CEO, former Zipp Tech Director), this rule states your external rim width should be ~105% of your measured tyre width for optimal aero performance.
Rolling Resistance: When we talk about a more efficient contact patch on wider tyres (at equal pressures), the patch actually becomes shorter front-to-back and wider side-to-side. This reduces the vertical deflection of the tyre casing as it rolls, saving watts!
Safety Warning: Stretching a narrow tyre over a massively wide internal rim doesn't just ruin cornering—it violates ETRTO safety guidelines and increases the risk of a blowout. Please pay attention to the safety markings.
⏱️ Chapters:
00:00 - The hype around wide rims & tyre trends
00:45 - Aerodynamics and the "Rule of 105"
01:36 - "Tyre Squish" vs "Tyre Squirm"
02:45 - The problem with stretching tyres on wide rims
04:12 - Which rim width is best for your riding style?
05:39 - Hooked rims, sidewalls, and mixing brands
07:08 - The 0.5mm Rule: How to calculate your actual tyre width
08:14 - Summary: Aero vs Comfort vs Handling
👇 Join the Discussion:
What tyre and rim width combination has worked best for you? Let us know in the comments below!
🔗 Links & Resources:
Book a service or fit at Mapdec Cycle Works: mapdec.com
Join our Skool community skool.com/mapdec
0Are your rims too wide for your tyres? The cycling industry is obsessed with pushing internal rim widths wider and wider, but what does that actually mean for your handling, aerodynamics, and safety?
In this quick tech deep-dive, we cut through the latest wheel trends to look at the physics of road bike tyres. We explain the difference between "Tyre Squish" (good) and "Tyre Squirm" (bad), why the Rule of 105 matters for aerodynamics, and why putting a 28mm tyre on a 30mm internal rim will ruin your bike's handling. Whether you are racing, riding all-road, or just looking for maximum comfort, here is how to find the perfect tyre and rim combination without wasting money on trial and error.
⚙️ Nerd Notes from the Video:
The Rule of 105: Popularised by Josh Poertner (Silca CEO, former Zipp Tech Director), this rule states your external rim width should be ~105% of your measured tyre width for optimal aero performance.
Rolling Resistance: When we talk about a more efficient contact patch on wider tyres (at equal pressures), the patch actually becomes shorter front-to-back and wider side-to-side. This reduces the vertical deflection of the tyre casing as it rolls, saving watts!
Safety Warning: Stretching a narrow tyre over a massively wide internal rim doesn't just ruin cornering—it violates ETRTO safety guidelines and increases the risk of a blowout. Please pay attention to the safety markings.
⏱️ Chapters:
00:00 - The hype around wide rims & tyre trends
00:45 - Aerodynamics and the "Rule of 105"
01:36 - "Tyre Squish" vs "Tyre Squirm"
02:45 - The problem with stretching tyres on wide rims
04:12 - Which rim width is best for your riding style?
05:39 - Hooked rims, sidewalls, and mixing brands
07:08 - The 0.5mm Rule: How to calculate your actual tyre width
08:14 - Summary: Aero vs Comfort vs Handling
👇 Join the Discussion:
What tyre and rim width combination has worked best for you? Let us know in the comments below!
🔗 Links & Resources:
Book a service or fit at Mapdec Cycle Works: mapdec.com
Join our Skool community skool.com/mapdec
