WHY I PUT 35MM TIRES ON A QUINTANA ROO SERVICE COURSE
When it came time to choose a new road bike, I knew I wanted the Service Course. I needed a high-performance aero bike for training, fast group rides, and the occasional road race, and the Service Course provided everything I wanted. It's developed by the same aero engineers who designed the record-breaking V-PRi, and it's the lightest and fastest drop-bar bike Quintana Roo has ever produced.
It also has one extra perk that drew me in: big tire clearance.
With clearance for 36mm tires, the Service Course is built to do battle with the road racing vanguard. It caters to riders who like experimenting with equipment in the hunt for every marginal gain. Tires are one of, if not the most important, performance upgrades you can make to any bike, and in recent years, more companies have started releasing fast-rolling high-volume road tires.
One tire in particular that caught my attention is Continental's latest 35mm GP 5000 S TR. Many consider the GP 5000 S TR to be the benchmark for high-performance road racing tires, and the 35mm version tested exceptionally well in an independent test by bicyclerollingresistance.com.
I'm a marginal gains hunter who loves experimenting with my equipment, so I decided to build my Service Course around these fast 35mm tires. I'll run through my basic setup below and answer the question many marginal gains hunters are wondering: will these tires keep up?
Why 35mm Tires?
First off, let's answer the question of “why?” For me, there are three main reasons I wanted to go big:
More Comfort
More air volume means lower pressure, and lower pressure means a tire that can absorb road chatter instead of transmitting it straight into your hands and butt. On a bike built for long training rides (most of my big training rides are 5-6 hours), that matters! A wider tire that soaks up vibration keeps you fresher for the moments in a ride that actually matter, like the last hard interval, the final sprint in a group ride, or the closing kilometers of a road race. Plus, it's just so much nicer when you smash your wheel into a pothole, crack, or bump in the road at high speed.
Lower Rolling Resistance
This can be counterintuitive, but wider isn't always slower. A larger-volume tire that can use a thinner casing and be run at lower pressure actually deforms less over rough pavement, which means less energy lost to the road. Independent testing backs this up. Gravel and mountain bike racers have known this for years. Especially when the surface is rough, wider tires have less rolling resistance than narrower tires. On anything other than perfectly smooth asphalt, a wider tire can roll just as fast, or faster, than a narrower one running higher pressure.
It's Cool, Different, and Fun
Not every performance decision needs a spreadsheet to justify it. Rolling up to a group ride or a start line on 35mm tires when everyone else is on 28s or 30s turns heads. Honestly, that's part of the appeal. Marginal gains hunting is as much about the process of experimenting as it is about the outcome. If a wider tire makes the bike more fun to ride while also making it faster, that's a win for me.
The Pros & Cons of Wider Tires
Pros:
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Increased comfort over rough or chipseal roads, reducing fatigue over long rides
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Comparable or better rolling resistance versus narrower high-pressure tires
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Improved grip and cornering confidence thanks to a larger contact patch
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Better puncture resistance from the added air volume cushioning the casing
Cons:
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Added weight from more rubber and casing material. This matters to some, and might matter more when climbing is involved
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A small aerodynamic penalty at higher speeds, since a wider tire increases frontal area. It's also much harder to stick to the rule of 105 when it comes to wheel width.
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Limited compatibility. Not every road frame or fork has the clearance to run them.
Why an Aero Bike with a 1x Drivetrain?
The Service Course frame can fit 36mm tires, but there was one limiting factor when it came to rear tire clearance: the front derailleur. With a front derailleur and a 2x chainring setup, the front mech cage will actually hit the rear tire. Eliminating the front derailleur entirely maximizes tire clearance.
This might sound like a compromise to some, but I'm actually a huge fan of 1x drivetrains (and so are some of our pro athletes like Kristian Høgenhaug and Marta Sánchez). Using the custom component request part of QR's custom bike builder, I asked the team to install a SRAM Force XPLR 1x gravel groupset on my Service Course. I'm using a 48t chainring with 165mm cranks.
With SRAM's latest 13-speed 1x gravel groupsets, a lot of the issues many riders may have had with 1x drivetrains in the past simply aren't issues anymore. I find the jumps between gears to be fairly tight, especially at the top of the cassette where it matters most, and I have ample gear range for most of my riding here in the mountains of Colorado. At this point, I'm so satisfied that I'm not sure I'll ever go back to a 2x setup.
Is a 35mm Tire the Best Tire for the Service Course?
So if you want to compare independent test data, bicyclerollingresistance.com is the place to do it. If you want to know how these tires fare on your local roads, you're going to have to ride them yourself. But I'll give you my qualitative assessment after ripping around the roads of Boulder, Colorado for the past few weeks on my Service Course.
The main thing, obviously, is the massive increase in comfort. Road buzz is gone. Cracks and potholes don't strike the same fear in me like they used to. After experiencing this, even if the tires are slower, I'm not sure I would willingly go back.
Another positive I've noticed is an increase in confidence when it comes to cornering and descending. This is nice on steep and fast mountain descents. Of course, it's also nice for the occasional jaunt onto dirt and gravel roads, which Boulder has plenty of.
The extra weight, however, is somewhat noticeable. On more than one occasion, when I've had to push hard and accelerate to prevent myself from getting dropped, I've caught myself wondering if it'd be easier with one of the narrower options.
Here's a rough weight comparison of the different GP 5000 S TR sizes:
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28mm: ~280-290g per tire
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30mm: ~300-305g per tire
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32mm: ~320-325g per tire
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35mm: ~365g per tire
Going from a 28mm to a 35mm adds roughly 85g per wheel (170g total per pair), which slightly impacts rotational weight. This matters most when accelerating or on steep climbs. Wider tires also require a bit more tubeless sealant (around 140ml for 35mm vs. 125ml for a 28mm), adding a tiny bit more rotational weight.
Is it going to be the difference between success and failure? Winning and losing? For us mere mortals, probably not. But it's worth considering if you want to leave no stone unturned. For climbing-heavy courses or fast crit racing, a narrower tire might be preferable. Otherwise, I'd take the 35mm. Want the ultimate compromise? A 30-32mm is likely the best choice.
Get the Tire (and Bike) You Want
Like every Quintana Roo, the Service Course is customizable through QR's custom bike builder. This lets you choose your paint color, drivetrain, wheels, and cockpit, ensuring your bike is dialed for your preferences and needs right out of the box.
Currently, the only tire option for the Service Course is the 28mm Continental GP 5000 S TR. This is a fantastic tire. Tadej Pogačar uses this tire. Most of our pro triathletes use this tire. It is the benchmark for road racing performance. But if you, like me, want to experiment with something else, all you have to do is ask!
In the custom bike builder, there's a nifty section near the bottom labeled “component requests.” Here, you can ask for anything, like wider tires or specific component or fit requests. I wanted 165mm cranks and my steerer tube to be pre-cut. I also asked specifically for my 1x Force XPLR drivetrain.
After submitting your order, a representative from QR will reach out to confirm your requests. You can also contact QR directly via chat, email, or phone and discuss your own custom build. This is how I got my bike set up for 35mm tires, and it's part of what makes QR special. They worked with me to deliver the exact bike I wanted.
