Road bikes are generally designed with quite thin tires. That’s because tire width makes a difference to the speed of your bike, and road bikes generally need to be quite quick. But if you’re using it for another reason – i.e. a commute to work, then speed might not be your top priority. In that case, you might be thinking about fitting a wider tire to your road bike.
There is a good chance that a thinner tire can be used on a road bike that comes with the 23mm tires. You can typically put 23-28mm tires on road bikes without much hassle, and sometimes even 30mm. Fork width and wheel rims determine how wide of a tire you can use on a road bike.
Don’t worry if none of that means anything to you, because today we’re going to start with the basics so anyone who’s interested in this topic can follow along. So, if you’re interested in finding out more, stick with us!
Max And Min Tire Width On A Road Bike
| Width | Good for | Not Good for |
| 23 mm | Racing | Rough terrain |
| 25 mm | Road and Speed | Rough terrain |
| 27-28 mm | Endurance biking | Racing, Road, and Speed |
| 30 mm | Somewhat rough terrain | Racing |
Knowing the tire width your road bike can handle might seem a little complicated, but once you learn all about tire clearance, you’ll be able to make decisions for yourself.
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If you’re here today for some general guidance, then, as a general rule, tires between 23 and 28mm width are usually ok for road bikes. Some will go to 30mm comfortably too.
If you don’t want to figure out how to tell if the tire will fit your road bike yourself, then just head to a bike shop and talk with one of the workers there and they’ll be able to guide you further.
If, however, you want to learn more than just general advice, then let’s look a little closer at how minimum and maximum tire width have changed over the years, and then look at how wide your tires on your road bike ought to be.
Road Bike Tire Width Changes
A few decades ago you wouldn’t see anything larger than a 23mm wide tire on a road bike. The professionals used them in their tours and races, and we regular riders did too. Nothing larger than 23mm was needed because it did the job. Road bikes were only ever expected to ride on tarmac roads, and 23mm tires handled that well.
Slightly wider tires have negligible rolling resistance increase, making them quite efficient on the road, and also more comfortable to ride and better suited to different terrain (not everybody has the luxury of sticking to just tarmac roads on their commute, after all).
Wider tires on road bikes are more popular nowadays, and wheel rims are manufactured in such a way to allow for these wider tires.
Why is that important? Because wheel rims are one half of the puzzle, fork width being the other part when thinking about tire clearance. Tire clearance essentially determines the tire width your road bike can handle.
Tire Clearance: What It Is And Why It Matters
The general max/min tire width advice we gave above might not apply to every bike in every situation, so if you want to figure out the tire width that’s appropriate for your road bike, you’ll need to do a little work of your own. And what you’re trying to work out is tire clearance.
Tire clearance is essentially the gap between your tire and any other part of your bike (apart from the wheel, of course, because that would be a pretty major design flaw). This gap is important because, without it, your tire can catch on different parts of your bike, including:
- Kickstands
- Fenders
- Trailer mounts
- Rack supports
- Chainstays
- Brake bridge
- Rim calipers
- Seat post
- Seat stays
You basically need a gap so your wheels can rotate freely without the tires catching on any of these things and either A) causing friction and slowing the bike down, or B) bursting the tire entirely.
And whilst all the above parts of a bike are important, the two most important when considering tire clearance are the wheel rims and the fork width (although all the above should be considered too). So, what steps do you need to take to measure your tire clearance and work out if you can fit wider tires to your road bike?
Step One: Measure Current Tire
You’ll need some calipers to do this accurately. There will be a measurement on the tire itself, but this isn’t always accurate and with tire clearance, you need to be as accurate as possible.
Use the calipers to measure your tire width, opening them in 0.5mm stages. You don’t want to squeeze the tire or you’ll get a smaller reading than you actually have. It’s best to leave the calipers slightly loose. This means you can be more confident with the tire clearance results you get later.
Step Two: Measure The Clearance
Measure the current tire clearance between the tire as it is now, and EVERYTHING listed above (excluding the parts you don’t have – for example, you might not have a fender or rim calipers, etc.). Write down all your measurements, saying there is less room than there really is where necessary.
Round down where possible, never round up. This will just mean you get the best tire clearance possible when you work out how wide you can go.
Once you’ve noted down every possible clearance between your current tire and the different parts listed above, focus on the smallest clearance. The rest don’t matter. So, for example, if the smallest clearance you have is 5mm, this is the number you’ll carry forward into the next step.
Step Three: Work Out Maximum Tire Width
On road bikes, it’s generally advised that you leave 3mm of clearance, anyway. So, if you already have 3mm of clearance as your smallest clearance calculated above, then you’re already running your maximum tire width.
If your smallest clearance is larger than that, so 5mm, for example, then you’ll need to take 3mm off so you know you’ll still have the 3mm minimum clearance you’ll need when you fit the new tire. Follow this equation:
2 x (smallest clearance – 3mm) + current tire width = maximum tire width you can run
The reason you multiply the clearance – 3mm by 2 is that you have that clearance on either side of your tire. Let us run you through an example with the 5mm clearance below.
Say you’re currently running 23mm tires. If the smallest clearance you have between your current tire and any other part of your bike is 5mm, then here’s how the equation would look:
2 x (5mm – 3mm) + 23mm = 27mm
Your maximum tire width here is now 27mm. That will still leave the 3mm clearance you need, and it’ll mean you can ride your bike without fear of friction or failure.
And that’s it – that’s how you work out the maximum tire width on your road bike (other bikes require more clearance, for example, MTBs often need 5mm clearance because of mud build up etc, but perhaps that’s a topic for a different day).
If you find yourself looking for tires wider than 30 mm there is a good chance that you should be looking at gravel bikes instead of road bikes. You may find an article on this topic here.
FAQ
To finish, we’ve put together this handy list of related FAQs that might help you understand maximum tire width more.
How Does Tire Width Affect Comfort?
Wider tires are more comfortable than skinnier ones as they have much better shock absorption. It’s one of the reasons why you’ll always find wider tires on bikes designed to ride on rougher terrains: mountain bikes, hybrid bikes, or gravel bikes.
How Does It Affect Speed?
Greater contact patch (where the tire comes into contact with the road), the extra weight and size make a wider tire slower. Wider tires have greater rolling resistance, they’re slower.
How Do You Know The Tire Widths For Your Rim?
If you don’t know your rim size, then simply record its diameter in mm. You should have access to this information already, but if not, the diameter of the rim in mm is the standard way to measure them.
If you want to know which tire widths work with your rim size, then look up the ISO (International Organization for Standardization) recommendations for your rim size.
But note, not every cyclist sticks to these rules, as they’re guides more than anything else. If you want to use ISO’s recommendations with the method we’ve described above, though, that would be useful since you’d be able to find a compromise.
Say ISO recommended a max tire width of 26mm on your bike, and in the example above you found that you could have 27mm tires with enough clearance to work well, you might drop down to the ISO recommendation of 26mm but probably you can use a 27mm tire without any problem.
