DC_Cycle

Hi All:

I have a 2021 Specialized Diverge Elite E5 (info) that works great as a gravel bike. However, I'm doing lots of long (75+ mile) paved rides these days and every little bit of speed would help me.

As a simple step, I'm thinking of changing out the current stock Specialized Pathfinder 700x38C gravel tires for road tires. Any thoughts on whether road tires would buy me a noticeable difference in ride speed on pavement? If so, any recommendations on which tire models and widths to try for someone with only so much money to spend? I've seen in another post that people generally like the Vittoria Corsa Control 30mm and Grand Prix 5000 32mm.

Picture of my current gravel setup attached.

Barrettscv 

Without a doubt the 700x32 Continental 5000 upgrade will improve your pace and increase your daily mileage range. The reduction in rolling resistance is substantial;

https://www.bicyclerollingresistance...gravel-reviews

Darth Lefty 

I've written about this before and it might be seen as a hot take, but I think the heavy-duty forks on gravel bikes need the big soft tires to make a decent ride. Fortunately there are plenty of big slicks right now for just this purpose.

woodway

If you can afford it, get a 2nd set of wheels. I've got a Ti Cross Bike that I ride both road and gravel. Two sets of wheels - set one has 700x32c GP5000 mounted for road riding, set two has 700x45c Gravel Kings Mounted for gravel riding. Takes but a minute to swap them.

goingup

Tires will have some impact, but I would not expect it to be as large as you might well be imagining. Keep in mind that rolling resistance tests are done under an ideal lab conditions whereas the roads that many of us ride on are far from that (even if not always fully gravel). The GP5000 may still be faster on a moderate road condition, but the difference is likely reduced when presented with the real world.

Perhaps more importantly, rolling resistance is only a small component of the forces acting against you. At 30kph, 90% of the resistive force is from the wind. (I'd link to the site making this claim, but not allowed as a new member - you might search for something like "fascinating-aerodynamics-bikepacking-bicycle-touring" to find it. Bicycle Quarterly also has an interesting article on the subject.)

I note that your riding position looks rather upright - both the stem position (although difficult to see clearly in your picture) as well as the brake hoods. Clothing is another factor - loose fitting clothing is a much larger factor than rolling resistance, as is what sorts of stuff you attach to your bike (and where).

I'd look over your clothing selection, and see if you can adapt to a more aerodynamic position before necessarily spending a bunch of money on tires (and maybe wheels) that might not make all that much of a difference.

mstateglfr 

The rolling resistance website linked is a helpful start, but leaves much to still guess.

I don't run a 32mm road tire at 44psi or 33psi, which are the listed free options. I would guess that at 65-70psi, the 32mm gp5k would be at 12w of rolling resistance.

Then you can see the 42mm Specialized tire was tested and you have the 38. So if that 38 were run at 50psi, then it would probably be 20w of rolling resistance.

Compare 12w to 20w, that's a best guess using the actual widths you want and general tire pressures that would likely be used for road riding in the given widths.
You will drop something like 370g of combined tire weight by going from the 38mm Specialized to the 32mm GP5k tires and that is nothing to ignore as it's over 3/4 of a pound.


As mentioned though, your riding position is going to be a huge difference maker on speed as you are a way bigger drain on speed than the difference between those two tires.
Figure out how to ride long stretches with your elbows bent and tucked with your hands on the hoods.

Random11

My guess is that you won't notice much difference. I have a Diverge with 700x38c tires and a Cervelo Caledonia with 700X30c tires, and ride the bikes interchangeably over paved roads. I do notice that the Caledonia accelerates more quickly and seems a bit faster up hills, but, with no scientific measurements to go on, I don't think my overall ride time is noticeably faster on the Caledonia than on the Diverge. I find them both equally enjoyable to ride on paved roads. I'm talking about two different bikes, not just different tires, and the Caledonia is lighter than the Diverge. Unless you're trying to squeeze out every last bit of speed, I'm doubtful that you'd notice much difference with thinner tires.

grant40

Tubular tires

cyclezen

The 'motor' aside - Wind resistance is definitely the 800 lb gorilla in defining available speed... and of all the elements, the rider posture/position makes the biggest difference. So that would be the place for biggest gains also.
In another thread, someone posted a very interesting URL showing a comparison of different rider positions and the effects on wind resistance on power equivalency requirements - the primary idea of the article was to compare recent UCI banned positions - but its quite enlightening on the most popular rider positions in general...
UCI Banned Road Bike Positions Aerodynamics
clothing, of course, can have a great affect on wind resistance. There are marginal gains to be had with the bike, most are in setup - but at an expense when it comes to 'aero' gear..

Wheels/tires can have a very positive effect on overall speed, realized in increasing gains as one adds 'terrain' and climbing. It has been shown that fast descending doesn't compensate for the climbing time.
Lighter/faster wheels and faster tires also can have a great effect on rolling terrain. When one can power up a roller, maintaining a higher relative speed, the overall avg speed will rise quite a bit.
If one bogs down on short uphills, the overall ride speed can suffer greatly.
If I were to use one bike for both road and gravel riding; I would most certainly opt for a wheelset for each ride type. Changing tires whenever a decision comes up between road or gravel, would be a PITA. and settling for gearing which would be a poor compromise in either, would also bug me tremedously. I can;t imagine needing a 34,36, or 40 + in any road situation, including really long and steeper climbs... But I would certainly want closer gear ratios than my gravel cassette offers.
Ride On
Yuri

t2p

Specialized Pathfinder 700x38 vs Continental GP5000 700x32 (and similar)

??!

the difference in long road rides should be very noticeable and significant

the tires will weigh less - especially with a smaller tube included - and should have less rolling resistance

and many more tires should make a difference ... including the Continental GP4S ... Panaracer Gravelking slicks ... etc etc etc

install those tires and you will wonder why you didn't make the switch sooner

Badger6

What pressure are you running the Pathfinders at? The tread is good on that tire for gravel, but the carcass of the Sport is pretty harsh (60tpi). Upgrading to the Pro tire would be a huge improvement, but for long road rides...

Have you considered a large volume slick, such as the Specialized Roubaix Pro 30/32? My first true gravel bike—and now do everything/commuter—Diverge Mk1 came fitted with those, and I’ve tried lot of other tires and kept going back to them because they offer the best balance between durability, puncture resistance, and rolling resistance IME. I run them tubeless at 45psi, and they are plenty comfortable for Imperial Century plus rides that might/might not cover all sorts of surfaces despite being “road” routes. They are hard to source these days, but they are out there.

DC_Cycle

Thanks for all the replies. Will start with adjusting my riding position (the low lying fruit) and then may tackle tires/wheels with time.

Atlas Shrugged

There is no speed difference from a narrower tire if you went with a supple 38mm tire which would be my advice. Panaracer GravelKing slick or Rene Herse, but there are plenty of options. No advantage to going 32mm.

https://www.renehersecycles.com/why-...re-not-slower/

Koyote

This.

If your 'gravel' is really just smooth-ish dirt roads, and you don't regularly ride in mud and other nasty conditions, then a smooth 38-40mm tire will be perfect.

Kapusta

I my experience, swapping tires can make a noticeable difference.

However, the biggest difference has been tire construction, not size..

rosefarts

The “approach” to some gravel roads in my area are so steep mountainous paved roads. As such, I’ve ridden them several times on both a 18lb road bike with 25mm GP 4000’s and a 22lb gravel bike with 38mm Gravelkings.

I’m pretty evenly split on my PR’S on certain paved segments between both bikes.

The road bike feels faster but at the end of the ride, there is very little difference.

Herzlos

Changing to narrower road tires will help you out a bit - the slick profile should run a bit smoother and you'll save weight which is a bigger deal when it's on wheels than elsewhere. If your wheels are tubeless compatible then going tubeless will save you a bit more weight too as well as making it less likely you'll get taken out by a puncture.

You'd need to measure your inner rim width (it may be written on the outside so check that first) to see how small a tire you can fit. Obviously smaller tires will require higher pressures so will be less comfortable, but dropping from 38mm to 32mm shouldn't be too bad. I'm not sure I'd want to go much narrower than that even if they would fit.

Then your gravel bike will be more of a comfort road bike.

Badger6

I’m going to politely disagree and agree at the same time. Until April 2021, my gravel ride was 2015/16 vintage and cleared 35s max. I rolled 32mm slicks on it (inflated to 34), and they were perfect for exactly the conditions you describe. When I got a “modern” gravel bike that would clear 47s, I started on 38s and eventually moved to 42s with a slick center section. The comfort was sublime and nothing I want to reduce, but the 32s on the older bike still roll faster on pavement, and aren’t uncomfortable. I’m split on which is actually better…one is faster, and one is more comfy, but the differences are minimal.

Koyote

I think we are in agreement. My recommendation of a 38-40mm tire was based on the same logic: smooth dirt roads can easily be ridden on 32mm, while 45mm would be more comfy; 38-40 is sort of a sweet spot. But yeah, if comfort is prioritized over speed, wider is better.

fwiw, my tires are almost 45mm wide, while most of my friends ride the same roads on 38-42mm tires. I like 'em wide.

msu2001la

I don't know anything about the Pathfinder tire in particular, but I frequently swap between GP 5000's (I've run both 28mm and 32mm, both are equally fast) and various 33mm-35mm gravel/cx tires and the difference on smooth pavement is very noticeable. Not only do the GP5000's roll faster than anything else, they're also quite a bit lighter which allows the bike to accelerate faster.

Beyond tires, I'd consider upgrading the wheels on that bike. A second set is helpful for swapping, and also an opportunity to get something more aero and/or lighter.

chas58

Huge difference going to GP5000s. Huge being ~10% or 2mph at 20mph. What else can make that difference (besides rider position, lol).

I've been riding GP5000s on very fast club rides (25-30mph) on my gravel bike. Everyone else is on 25mm tires at ~100psi. Yet my power readings are 5-10% lower than most of of the other riders. With the crap asphalt we have here, the bigger tires are faster (our asphalt is worse than some of our gravel). I've oversized them a bit to 38mm - and everyone else assumes I'm working harder than them. They really look a LOT larger than 25mm tires, yet are fine on MUP, chloride covered dirt, and rough asphalt (I run around 40psi).

Unlike the above posts, I'd really recommend the 34mm Schwalbe Pro ONE TLE. Realistically is is only 1mm larger than the 32mm GP5000, but it seems to me to be a lot more robust.

I'm a little luke warm on the aero. It depends a lot on your apparent wind, but my long solo rides tend to be at speeds where aero doesn't make too much difference (unless it is a windy day of course).

tFUnK

The difference between my road bike and my gravel bike is about 2mph in average speed. Apart from the 38mm knobby tires (vs. 25mm slicks), the gravel bike also has a small handlebar bag, and I tend to ride in baggier clothing when on the gravel bike (though I also do t-shirt rides on the roadie). But otherwise, my gravel bike's geometry isn't too different from my road bike's geometry. I guess i can try some 33mm slicks and ditch the handlebar bag and see how much of that 2mph difference is gained. This is a long-winded way of saying that you might expect up to (but probably not quite) a 2mph improvement in average speed with a set of slicks, all other things equal.

biker128pedal

I have Domane SL6 with two sets of wheels. The Paradigm 25s it came with now have Bontrager GR1s 35mm (measure 37mm) set up tubeless. The second set are Aeolus Pro 51s with GP5000 25mm F and 28mm rear. Same course same by road segments. Comparing down hill and on flats about 3 mph difference. Up hills about 2. Not huge but makes a difference on a long ride. The GR1s are smooth on rough surfaces. The Colonial parkway in Va from Jamestown to Yorktown is concrete but exposed River stones. The GR1s are slower but less taxing.

I’d go 28mm or 30mm for the road. Second set of wheels if you can swing it. I have no issues with brake disc alignment. Oh for road getting some latex tubes for F & R to try when the new rear tires arrives.

chas58

I got that 2mph back just by using GP5000s. Really, not much difference between that and a pure road racing steed in my case.

sean.hwy

I have a few bikes and several wheels with different tire combos.

aero road bike carbon wheels 28mm gp5000 fastest

gravel bike with same exact carbon wheels and 28mm gp5000 wheels ( about 0.5 to 1mph avg slower than systemsix aero bike ) close enough for me as non racer I sold me aero bike

gravel bike carbon wheels 32mm gravel king slicks ( probably another 0.5 to 1.5mph slower that gravel bike with 28mm gp5000 tires ) this is the sweet spot for me. close enough to gp5000 speed and I can ride off road

gravel bike 38mm + knobby tires proper off road tires. way slower. night and day slower. I only put these on if I am riding 100% in the dirt.