What Size Inner Tube Do I Need? — Complete Guide
Getting the wrong inner tube is one of the most common mistakes cyclists make. This guide explains exactly how to find the right size — in under two minutes.
Step 1 — Find your wheel size
Look at the sidewall of your tyre. You'll see a number like one of these:
- 26" — the most common size for mountain bikes, hybrid bikes, and older leisure bikes
- 27.5" (also written as 650b) — modern mountain bikes
- 29" — larger mountain bikes and some gravel bikes
- 700c — road bikes, gravel bikes, and most hybrid/commuter bikes
- 20" — folding bikes (Brompton, Dahon) and children's bikes
- 24" — children's bikes and some older MTBs
The wheel size on your tyre must match the wheel size on your inner tube. A 26" tube will not fit a 700c wheel, even though they look similar in size.
Step 2 — Find your tyre width
The second number on your tyre sidewall is the width. It looks like this:
- 26 x 1.95 — 26-inch wheel, 1.95-inch wide tyre
- 700 x 28c — 700c wheel, 28mm wide tyre
- 27.5 x 2.10 — 27.5-inch wheel, 2.10-inch wide tyre
Inner tubes are designed to fit a range of widths — for example, a tube labelled 26 x 1.75–2.35 will fit any 26-inch tyre between 1.75 and 2.35 inches wide.
You don't need an exact match — you need a tube whose width range covers your tyre width.
Quick reference:
| Tyre marking | Tube to buy |
|---|---|
| 26 x 1.75, 1.95, 2.10, 2.125, 2.35 | 26" tube, 1.75–2.35 width range |
| 27.5 x 1.75, 2.10, 2.25 | 27.5" tube, 1.75–2.35 width range |
| 29 x 2.10, 2.25 | 29" tube, 1.75–2.35 width range |
| 700 x 23, 25, 28 | 700c tube, 18–25mm or 25–32mm |
| 700 x 32, 35, 38 | 700c tube, 32–47mm |
Step 3 — Identify your valve type
There are two valve types used on bikes in the UK:
Schrader valve (also called an American valve)
- Wider, shorter valve — identical to a car tyre valve
- Can be inflated at any garage or with a standard pump
- Common on mountain bikes, hybrid bikes, and leisure bikes
- Easier to use for most people
Presta valve (also called a French valve)
- Narrower, longer valve with a small locking nut at the top
- Requires a Presta-compatible pump head (most quality pumps have both)
- Common on road bikes and higher-end mountain bikes
How to tell which you have: look at your current tube or wheel rim. Schrader rims have a wider hole; Presta rims have a narrower hole. You cannot fit a Schrader tube into a Presta rim.
Step 4 — Check valve length
Valve length matters if you have deep-section rims (common on road bikes). Standard valve lengths are 40mm and 60mm. For most mountain bikes and hybrids, 40mm is sufficient. If you have deep rims, choose 60mm or longer.
Common questions
Can I use a slightly different width tube? Yes — tubes are stretchy and will accommodate a range of widths. A tube rated 1.75–2.35 will work fine in a 1.95 tyre. Don't go too far outside the stated range or the tube may be under-stressed (too wide) or over-stretched (too narrow).
My tyre says 26 x 1.75 2.125 — what does that mean? This means the tyre fits wheels with an inner diameter of 26 inches and suits tube widths from 1.75 to 2.125 inches. Any 26" tube covering that width range will fit.
What's the ETRTO number on my tyre? ETRTO is a European standard sizing system. It looks like 47-559 (width in mm x bead seat diameter in mm). 559mm = 26", 622mm = 700c/29", 584mm = 27.5". If you're unsure, use the ETRTO number to match tubes precisely.
I have a 26" tube but it won't fit — why? Check the valve type. A Schrader tube won't fit through a Presta rim hole. Also check the width — a very narrow tube (e.g. 1.0–1.5") won't stretch to fit a 2.10 tyre.
Can I replace a Presta tube with a Schrader tube? Only if your rim has a Schrader-sized hole, or if you use a rim adapter. Most MTB and hybrid rims accept Schrader valves. Road bike rims typically do not.
Which tubes does Peak Bike Station stock?
We stock Impac inner tubes in the most common sizes for mountain bikes and hybrid bikes — all with Schrader valves, which are the most practical choice for most riders in the Peak District.
- Impac 26" MTB Inner Tube — 26 x 1.75–2.35, 40mm Schrader — fits most 26" MTBs and hybrids
- Impac 27.5" MTB Inner Tube — 27.5 x 1.75–2.35, 40mm Schrader — fits modern 27.5" MTBs
- Impac 29" MTB Inner Tube — 29 x 1.75–2.35, 40mm Schrader — fits 29er MTBs
All available in store at Peak Bike Station, Hadfield — or with free UK delivery on orders over £18.
Carrying a spare on Peak District rides
If you're riding the Longdendale Trail or Trans Pennine Trail from Hadfield, we always recommend carrying a spare tube. A puncture on a trail is far easier to fix with a fresh tube than a patch kit — swap the tube, ride home, repair the punctured one later.
Pair your spare tube with a Zefal EZ Max CO2 inflator for a fast, lightweight inflation solution on the trail. Also see our Weldtite Puncture Repair Kit for a reusable alternative.
Peak Bike Station is based at Hadfield station, Derbyshire — 50 minutes from Manchester Piccadilly on the Glossop line. Inner tubes in stock for collection today, or order online for free UK delivery over £18.