Here’s the quick answer:
In basic terms, a 700x38c tire is approximately 27 1/2 inches by 1 1/2 inches (or 1.50 inches).
Easy, yeah? Sadly, things aren’t always quite as simple when it comes to bicycle tires. What’s my opinion? Well, if the bike tires that you have on your bicycle currently say that they’re “700x38c” then only ever swap them for tires that are the exact same size i.e. “700x38c”. If you replace them with a tire measured in inches, there’s a good chance that you’ll run into issues now, or some way down the bike trail (when you’re a long way from a nice handy bicycle repair shop).
Why is that? Well, there’s a few different reasons for it. We’ll have a quick look at these in a moment and then I’ll give you the details of a great replacement 700x38c bike tire and inner tube. Handy if you’re maybe struggling to track these down from other sources.
What does 700x38c actually mean?
700x38c is simply the sizing of your bike tire and is measured using what’s known as the ‘French system’.
If we break this down we see that 700 is the nominal diameter in millimeters of the tire. The following number, 38, gives the approximate tire width (again, the measurement for this is in millimeters). The c at the end harks back to a width code used in the French system (i.e. this is the bit of the tire you’d see if you’re looking at the bike wheel whilst standing in front or from the back). Thankfully we can keep it nice and simple and ignore the last “c” bit as in present-day cycling it’s normally obsolete. It’s useful to know however that it was a key component in the French tire classification system and divided widths from the narrowest (known as “a”), right up to the widest (that was known as “d”). By that system, “c” tires were ones that were almost the biggest sized width you could buy for 700 wheels.
What’s the issue with swapping from 700x38c to inches?
You’d think it was easy, wouldn’t you? Unfortunately not. You see the issue is that figures used for bike tire sizes are what’s known as ‘nominal’. Not a word that we often use in conversation, but it’s a fancy way of saying that the numbers printed on the tire wall don’t always (or ever!) match up to the reality of those circles of black rubber at each end of your bike. There’s many reasons why this is the case. Often it’s due to inaccuracies in manufacturing processes. Now and again it can be down to tire companies trying to shave off some thickness of rubber from the diameter or width of the tire (or both) in order to cut the weight of their product.
But, whatever the reason, it means that tires that are ‘roughly close enough’ will more than likely not be actually close enough at all and will give you bike problems in the (not too distant) future.
You just need to get the right product for the right job. As is so often the case in life.
Let’s take a closer look at what that means for our 700x38c bike tires.
What size bicycle tire do I need?
When buying your new tires, make sure that you choose ones that say “700x38c”.
I can guarantee that you’ll see a ton of tire sizes for sale when you look online. Sadly, as we’ve already seen, bike tires that are just about ‘close enough’ to your stated tire size will likely not fit your bicycle wheel rims correctly. This may lead to problems such as punctures. You may need to pick amongst (1) the brand that you prefer to purchase and (2) the amount of ‘tread’ or rubber grip that you want the bike tires to have. With bikes that going to be used just on the road or smooth paved trails, I’m generally a fan of smoother tires. These are likely to be faster-rolling and give less unwanted vibration as you pedal along. Bear in mind that, if you might experience slippery conditions, then it can be a good idea to move to knobblier tires that will give you more grip.
Schwalbe makes some great bicycle tires and this one shown in the image above is a really good example. It’s the perfect replacement size for your bike tires and features a durable construction and high levels of puncture resistance.
Take a good look at the tread on these bike tires and you’ll see that they have an open pattern with knobbly rubber patches along the sides. This means that these tires are good for a wide range of surfaces. Smooth for paved roads and the extra tread up the sides gives good traction on looser surfaces and allows you to cycle confidently when you’re going round corners on them.
In my opinion, this is a fantastic pick for bikes with 700x38c tires.
What bike inner tubes should I buy?
When it comes time to pick yourself a new inner tube you must make sure to match up the diameter shown on your tire (for our tires that’s 700) with a width measurement that covers the diameter shown on the tire (38 in our case). It sounds complicated, but actually it’s really easy – don’t worry! The size of bike inner tubes varies depending on how much air you fill them up with, so you’ll find them printed with the diameter and a width range, for example “700×35-43”.
For that example, an inner tube with size 700×35-43 would work with bike tires between 700×35 up to 700×43 inclusive.
This tube from Co-op Cycles is a really good option – make sure you pick the “700C x 35-43mm” tube size. Tough and resistant to puncture by thorns. Grab a Presta pump adaptor to inflate these with a Schrader (auto) style pump.
How do I replace bike tire and inner tube?
This is where the rubber meets the road – literally! If you’ve got yourself prepared and are have the right tools with you, then getting a puncture can be a little bit annoying but shouldn’t ruin your bicycle ride. You should always make sure that, when going out for a cycle, you always take a spare inner tube (or even a couple of them), a basic portable bike repair kit, two plastic tire levers and a way of inflating the new inner tube. You can either use a CO2 tire inflator for this or a hand pump. You’ll then find that it should only be an easy 30-minute task to get you back on your bike and away. It’s also a good chance to rest the legs and grab a quick snack and drink to refuel.
There are five steps to fixing a puncture:
- Remove the bike wheel
- Remove the tube
- Find the cause of the flat
- Repair or replace the tube
- Reinstall the bike wheel
For an easy how-to guide, have a quick watch of this video.