Bikes
Will that part actually fit?
Frame sizing, tire and rim clearance, and cassette fit — worked out from the manufacturer's own published numbers, so you can check your bike before you order.
Start with one of these questions
“The chart says I'm between sizes, and two 'mediums' are different. Which do I order?”
Why two bikes both called "medium" can differ by more than a size, and how to use published stack and reach to order the right one — including how to compare a candidate against a bike you already ride.
Size it from the geometry“My rim says 622 x 19C and the tire says 700 x 35C. Will it fit?”
Bead seat diameter is what governs, not the 700C or 29er label. How to check diameter, match tire width to internal rim width, and find the pressure ceiling that applies if your rim is hookless.
Check the fit and the pressure limit“Same number of speeds, but the new cassette won't go on the hub. What do I buy?”
The freehub body decides which cassette fits, and matching the speed count proves nothing. How to identify the body on your wheel, plus the two follow-on checks for chain and derailleur capacity.
Identify your freehub
Five numbers worth knowing
Labels mislead and size letters are not measurements. These come from published geometry, standards designations and manufacturer compatibility documents.
- A tyre fits a rim only if the bead seat diameter matches. That number, not the marketing label, is what governs. 700C, 29-inch and most modern '28 inch' are all 622mm. 27.5-inch and 650B are both 584mm. And Schwalbe states that three different diameters — 559mm (mountain), 571mm (triathlon) and 590mm (Dutch touring) — have all been sold as '26 inch'.
- A frame size letter is not a measurement, and it is not consistent even within one brand. Canyon's own published geometry gives the Endurace CF 7 Disc in size M as stack 590mm / reach 378mm, and the Ultimate CF SL 8.0 in size M as stack 567mm / reach 391mm — 23mm apart in stack and 13mm in reach, same manufacturer, same letter.
- On a hookless (straight-side) rim there is a pressure ceiling that overrides the number on the tyre sidewall. ENVE states the ETRTO/ISO maximum for hookless is 5 bar / 72.5 psi, and 4.5 bar / 65 psi for 30-34mm tyres; Zipp states its TSS rims must never be inflated above 5 bar / 72 psi. Schwalbe states hookless rims may only be used with tubeless-ready (TLE/TLR) tyres.
- A cassette fits the freehub body it was designed for and nothing else. Shimano's compatibility document C-731 lists five spline patterns with different tooth counts and lengths: MICRO SPLINE (23 splines, 26mm), HG spline L2 (18 splines, 37.65mm, road 12-speed only), HG spline L (9 splines, 36.75mm), HG spline M (9 splines, 34.9mm) and HG spline S (9 splines, 31mm). SRAM states its XDR body is 1.85mm longer than XD.
- Matching the speed count does not establish that a part fits. KMC's product page for its X12 12-speed chain states it is not compatible with SRAM T-Type, eTap or Flattop — all of which are also 12-speed. The governing fact is always the manufacturer's stated compatibility, not the number of gears.
Who this is for
People who already own or have chosen a bicycle and are blocked on one specific fit-or-fit-it question: which frame size to order, which tyre will actually mount on their rim, or which cassette will actually slide onto their freehub. It is for the person standing at a checkout page or holding a part that will not go on, not for someone browsing for a new hobby.