Continental Grand Prix 5000 Comparison: 23, 25, 28, and 32 mm Compared

It's been nearly 4 years since our Continental Grand Prix 4000S II comparison article where we compared the rolling resistance of a 23, 25, and 28 mm Continental Grand Prix 4000S II. Since writing that article, we've learned an awful lot about rolling resistance and we now know some data was missing in the original Grand Prix 4000S II comparison.

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With the release of the Grand Prix 5000 (go here for our full 25-622 GP 5000 review), we see a great opportunity to do this test all over again. Our aim with this test is to try to solve the age-old question: Does a wider tire offer a lower rolling resistance? We've now performed tests with different inner tubes and have also performed tests at the recommended air pressure (15% tire drop) and at the same comfort level (4.5 mm tire drop).

Continental now also offers a 32 mm version of the Grand Prix 5000 in addition to the 23, 25, and 28 mm versions. The availability of the 32 mm version makes this comparison even better as it gives us an additional data point to understand the differences between the different sizes even better.

This is going to be quite a long read (~ 10 minutes). If you don't have the time to read this article completely, we recommend you to go straight to the conclusion as we feel it's a good summary of this article in just a 1 minute read.

Test Set up and Conditions

We've performed all tests on the same day to get the data as accurate as possible. All tests are performed using our standard test protocol. All data used for this test is 100% comparable to all other data on this website.

In our previous Grand Prix 4000 comparison article, we used the same Continental Race 28 100 grams butyl inner tube for the 23, 25, and 28 mm wide tires. When we look at the specifications of the Continental Race 28 inner tube, we see it's only rated to be used up to 25 mm wide tires. Our previous test was flawed because that inner tube isn't specified to be used with 28 mm tires.

We have corrected this issue and have used the 100 grams Race 28 inner tube only for the 23 and 25 mm wide versions of the GP 5000. The 28 and 32 mm wide versions use the 130 grams Continental Race 28 Wide inner tubes that are rated for 28 and 32 mm wide tires.

Because we do think testing all tires with the same inner tube provides valuable data, even if we go out of the specified range of the inner tube, we've also tested the 23, 25, 28, and 32 mm wide versions of the GP 5000 with an 80 grams latex inner tube.

We've decided to do this with a latex inner tube because a latex inner tube has much less rolling resistance. Going to a bigger latex inner tube would only result in a negligible increase in rolling resistance.

The recommended air pressure (15% tire drop) test and same comfort level (4.5 mm tire drop) tests are performed with the Race 28 and Race 28 Wide butyl inner tubes to get to the most realistic real-life usage scenario.

The 28 mm GP 5000 has a maximum air pressure of 115 psi / 7.9 bar. The 32 mm GP 5000 has a maximum air pressure of 100 psi / 6.9 bar. We ignored the maximum air pressures and tested all tires at 60, 80, 100, 120 psi. Please beware of this and keep to the maximum inflation pressure when using these tires on the road.

Test Conditions

• Speed of 29 km/h / 18 mph
• Total wheel load of 42.5 kg / 94 lbs
• 700 x 17C wheel
• Temperature between 21.5-22.5 °C / 71-72 °F
• Diamond plate drum surface
• 77 cm drum diameter
• Tires are run in for 30 minutes at 60 psi / 4.1 bar

Tire Specifications, Size, Weight and Thickness Measurements

In an ideal world, all sizes of the GP 5000 used for this test would be spot on to the specified weight. Unfortunately, only the 25-622 version is within 1 gram of the specified weight. The other 3 sizes are actually quite a bit lighter than the specified weight. The 23-622, 28-622, and 32-622 are all very close to 5% lighter than the specified weight.

The higher weight of the 25-622 version comes from the slightly thicker tread thickness as it has a measured tread thickness of 2.8 mm while the others are between 2.6 and 2.7 mm. We'll have to keep the slightly higher weight and tread thickness of the 25-622 version in mind when analyzing the rolling resistance tests results as more material results in a higher rolling resistance.

When looking at the measured width of the tires, we see the 23-622 and 25-622 versions are a bit wider than specified on our 17C rim. The 28-622 and 32-622 come very close to their true size. I suspect this is the result of using the same 17C rim for all tires. The 28-622 and 32-622 versions will be a bit wider when used on 19 and 21 mm internal width rims.

Test Results

Rolling Resistance Test Results with a Latex Inner Tube

We've started out with simply testing all sizes of the GP 5000 at the same air pressures and with the same inner tube. This is basically the same scenario as our Grand Prix 4000S II comparison test from 4 years ago. This time we've used an 80 grams latex inner tube instead of a butyl tube. We've decided to use a latex tube to minimize the influence of the inner tube on the total rolling resistance.

From the results above, we can quickly draw the same conclusion that we got from our test from 4 years ago: At the same air pressure, a bigger road bike tire has a lower rolling resistance.

Please keep in mind that the 25-622 sized GP 5000 is the only tire that is slightly heavier than the specified weight. I suspect if we got a 25-622 version that is also 5% lighter just like the other sizes, it would be 0.2 - 0.3 watts faster and fit right in between the 23 and 28 in the chart above.

Rolling Resistance Test Result with Butyl Inner Tubes

We've now substituted the 80 grams latex tube for a 100 grams butyl tube rated up to the 25-622 size for the 23-622 and 25-622 sizes and a 130 grams butyl tube rated up to the 32-622 size for the 28-622 and 32-622 sizes.

With the butyl inner tubes, the bigger tires still have a lower rolling resistance at the same air pressure. We do see that the 28-622 size is now closer to the 23-622 and 25-622 sizes because of the step up from the 100 grams inner tube to the 130 grams inner tube. It looks like the difference has been closed up a bit by going to the right sized inner tube for the bigger tires.

We still see the 25-622 size has a slight handicap because of its 5% higher weight and tread thickness. It should be very close to the 28-622 when both have the same tread thickness.

Rolling Resistance at Recommended Air Pressures (15% tire drop)

We've also tested all sizes of the GP 5000 at the 15% tire drop air pressure which is a value that is very close to the air pressure that is recommended by most tire manufacturers for a given tire size.

Please be aware that the 15% tire drop air pressure results in a bigger tire giving a more comfortable ride. This is because 15% tire drop, when expressed in an exact height measurement, results in a higher value for the bigger tire because its height is also higher.

As can be seen from the table above, 15% tire drop for the 23-622 is 3.2 mm and 15% tire drop for the 32-622 is 4.5 mm. This means the 32-622 effectively acts as a 40% softer spring when compared to the 23-622.

When we analyze our rolling resistance test results at the 15% tire drop air pressure, we see that the tables have turned and the larger tires do not have have a lower rolling resistance anymore! As we've explained that's mostly because the bigger tire will give a more comfortable ride.

But wait...

In the previous tests where we tested all tires at the same air pressures, the bigger tires had a lower rolling resistance. At the same air pressure, a bigger tire will be less comfortable as tire drop will be less and subsequently works as a harder spring.

Rolling Resistance at the Same Comfort Level (4.5 mm tire drop)

We've adjusted all air pressures to values that provide the same comfort level (4.5 mm tire drop) and what do we see... a flat line! All sizes of the GP 5000 now have nearly the same rolling resistance. We even see the 25-622 being the slowest (by 0.2 watts) which can be traced back to it being the tire with the highest tread thickness.

We feel the rolling resistance at the same comfort level is the most important part of this test as it equals the playing field for all tires. We have now learned that going to wider tires does not directly result in a lower rolling resistance but only if you're ok with giving up comfort at the same time.

So why not just run 23 mm tires and get the aero benefit? At some point, a 23 mm tire isn't able to provide the same comfort level as a 32 mm tire anymore. The smaller tire will start bottoming out and you'll get pinch flats when the inner tube gets squeezed between the tire and rim.

Conclusion

A bigger road bike tire (at least the Continental GP 4000 and GP 5000) provides a lower rolling resistance at the same air pressure. You do have to realize that at the same air pressure, a bigger tire will provide a less comfortable ride.

At the 15% tire drop air pressures, which are very close to the recommended air pressures for a given size, the tables are turned and a bigger road bike tire will have a higher rolling resistance. The higher rolling resistance of the bigger tire is because it provides more comfort at the 15% tire drop air pressure.

We feel the ultimate test is adjusting all tires to the same comfort level. When all tires are adjusted to the same comfort level, rolling resistance is nearly the same (0.2 watts max) for all sizes of the GP 5000.

We now feel picking the right size tire is more a matter of looking at what level of comfort (and grip) is required. At some point, a smaller tire isn't able to provide the same comfort level (and grip) as its bigger counterpart because it will start bottoming out.

If you want to go as fast as possible, choose your required comfort level and pick the smallest tire that can provide that comfort for you.

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