Big difference between road bike and gravel bike with road tires?

I’ve been doing this on 24x24 spokes on a few sets of LB.

I have only had them for about 5 months, but no issues at all. I got the DT350 hubs and Sapim X-Ray spokes. The rims were perfectly true and no visible defects. I know that doesn’t mean much, but there’s a lot of local people that have ridden their MTB rims for years with no complaints or issues.

The ordering process is a bit weird if you order from China (Global warehouse). Even though it seems like you can place an order on the website, they will email you and you sort out the finer details before your order is really complete. If you order from Vancouver (NA warehouse), you can talk to them directly on the phone for your order. It might be different right now due to COVID.

The hardest thing about it all is that LB gives you so many options and in the end the wait time for some of those choices varies a lot. That’s why they contact you - they help you figure out what meets your needs for spec, timing, budget. And prices are kind of negotiable when they don’t have exactly what you want or the wait is long

I could, but I already ordered the GRX crank when it was on sale (and in stock). Plus it has wider gearing (48/31) which is part of the advantage of GRX. So, I might as well use the new crank.

Right now, I’m 100% road… just the Synapse. :grin:

For what it’s worth, the Diverge will replace my Synapse and add substantial gravel capability with a second wheelset. I looked at everything else (Topstone, UP/UPPER, Exploro, etc) and, IMHO, the Diverge made the most sense. I like the idea of having some suspension (FutureShock) plus a compliant rear (with no dropper), and I like the great tire clearance of the 2021 Diverge.

Don’t really understand that. Rolling over stuff has to do with the outer tyre diameter, which is supposed to be the same for 700c and 650b? The advantage of 650b is that you can run a bigger tyre (more volume).

Honestly, I dunno. I have two friends who recently went gravel (I can honestly claim to be the cause for both, one sold his MTB seeing no purpose in it anymore) and both claim they tested 700 v 650 and claimed the 700 gave them better rollover than the 650s. That’s all I’ve got.

I love my 650b DT Swiss 1400s and have no intention of replacing them with 700s or putting road wheels on that bike (I’ll change the rubber as conditions warrant).

[edit: change “to intention” to “no intention” for clarity]

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650b can be larger or about the same as 700c, but only when comparing apples (700c road tires) to oranges (650b road tires). The concept of road plus kind of renewed interest in 650b by noting that 650x47mm was the same diameter as 700x28mm, so it wouldn’t affect the geometry of the bike, if you have the tire clearance.

However, if you have gravel tires on both wheels, the 700c will be bigger for sure. The difference in radius will be 19 mm at the same tire width, which is 5.6%. In my opinion and experience, that doesn’t matter on gravel. The bigger difference will be in inertia (higher for 700c), assuming you compare similar spec wheels.

Here’s a comparison of tire radii and volume. Volume is proportional to comfort

Tire Size, Radius, Volume

Radius is what affects bb height, handling

700x25 is 340 mm radius, 1.0 L

700x28 is 343 mm radius, 1.25 L, same radius as 650x47 but only 37% of the volume

700x32 is 347 mm, 1.65 L

700x38 is 353 mm, 2.35 L

700x42 is 357 mm, 2.9 L, this is 11 mm higher BB than 650bx50 and 74% of volume

700x44 is 359 mm, 3.2 L

650x42 is 338 mm, 2.7 L

650x47 is 343 mm, 3.4 L, same radius as 700x28 but 272% volume

650x50 is 346 mm, 3.9 L

650x54 is 350 mm, 4.6 L

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Thanks, that’s a excellent information! Of course 650b and 700 diameter depends in the tyres in both wheels!

To be honest, I would assume the biggest factor for “feel” will be tyre pressure, regardless of the size/volume…

Tire pressure and tube (latex are magic carpet ride) make the most difference for comfort, but tire size dictates what pressure your can run without flats. Plus width plays a big factor in rolling resistance.

I’m finding more and more (trustworthy) sources saying the opposite: that they’ve always thought width would play a big factor in rolling resistance, but that when finally testing it rigorously they’re discovering that it’s not. The change in the shape of the contact patch and other factors mean that you win some, lose some, and the net change is not very large at all. Wider you get more hysteretic losses but less suspension losses.

The most striking (and concrete) comment was from Jan Heine at René Herse. He wrote on their blog that they tested the same tire, same casing, in different widths, and that they found little difference in speed between any tires within 25 to 54mm of width. That’s a huge range… but assuming they’re right, and I have no reason to believe they’re not, it’s also fantastic news.

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There is a test on BRR of the GP5000 in every size. Then they adjusted tire pressure to 15% of compression they found that rolling resistance was about the same from 23mm to 32mm.

https://www.bicyclerollingresistance.com/specials/grand-prix-5000-comparison

In their conclusion they do say that the fastest tire is the smallest that provides the level of desired comfort.

If you don’t want to be the fastest out there then you leave little on the table by going with a 28 or 32mm tire. Cornering and responsiveness could be compromised on the larger tires if your rim isn’t wide enough. And the wider you go the harder it is to aero optimize with a rim of the right width.

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Although I’d add that this is only true on very good road surfaces where the rolling resistance tests in the lab are close to real-world conditions.

If your roads are sometimes in less-than-great conditions, a wider tire will not just be more comfortable, it’ll have more traction and thus, be faster for the same reason that in most circumstances, modern fullys are faster than hardtails. A hard narrow tire might be bouncy and you lose contact to the road. A wider tire will stick to the road more and give you a better, safer and ultimately faster ride.

I’m not disputing what you are saying and personally I do want to build my next race bike with the ability to run a 28mm (30mm actual) tire on a 30mm wide rim so that it’s still aero optimized.

But, I’m not sure the data is clear on the concept. If 32mm or 40mm tires were clearly faster then pros would be riding them instead of 25mm tires. The pros don’t even go very wide at Strade Bianche. They are running 28-30mm tires.

In this Silca blog post they are showing the break point on “course asphalt” to be 95psi which sounds high to me. Even on “roughened concrete” the break point is still 70psi. It’s not quite making the case for running 32mm tires @ 50 or 60 psi.

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Lowest rolling resistance will always depend on the surface, as that data shows. Drum tests are flawed because they use a round surface (the drum) as a substitute for the flat road. They also have no rider on the bike, so you lose all effects of human body hysteresis, which are large.

As you said, aero is the main downside to wider tires. I chose wheels aero optimal for 30 mm (actual width) tires. That, plus latex tubes and a forgiving seatpost, mean all the world to comfort. My bike (Cervélo Aspero) is consistently called stiff. But with my setup, it’s wonderfully comfortable. Frame stiffness has very little impact to comfort. It’s all tires/tubes/pressures and seatpost.

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I’m familiar with these graphs.

But traction ≠ rolling resistance. Traction, needless to say, is important for cornering and braking — and on very bad roads also for propulsion. Sometimes you need to trade better traction for higher rolling resistance, and making that trade can be worthwhile in that it will make you faster overall.

This is why modern full-suspension mountain bikes are, in most conditions, faster than hardtails. They offer better traction (which among other things results in better power transfer), fatigue the rider less and are more capable downhill.

Road bike pros are very conservative, and I wouldn’t use them as a meter stick. Plenty of teams stuck to box section rims on the cobbles long after that was necessary. You hear stories of people riding ungodly pressures (which can be even higher on tubulars, yay!), because that’s what the common lore is.

Pros are also limited by their sponsors. Most road frames are limited to 28-32 mm tires — at least as per manufacturer specs. So 32 mm might be the widest tires pros can ride without running into trouble with their sponsor.

Furthermore, races on the cobbles (or other bad road surfaces) only have sections that are on cobbles. So you in practice you need to find a compromise between being fastest on the smooth road and being fastest on the cobbles. You could also think of races like the Belgian Waffle race, where the really fast guys apparently just use road bikes and either have great bike handling skills and/or make up for all the time they lose on the technical sections by hauling rear-end on the road.

As an aside, a few years back GCN tested a road bike vs. a cx bike vs. a hardtail mountain bike, and the mountain bike was fastest, the CX bike was in second place and the traditional road bike last. (Although the bit they chose looked quite gnarly and yes, I know, this isn’t a scientific test.)

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Have you tried covering up the paint to see if that slows you down? All gray and black?

Huh?

The bike you ended up with, the color scheme looks fast… just an out-of-context joke.

Haha my bad, yes, it does look very fast. Not going to lie, that pink and yellow fade paint job sealed the deal for me.

I’m thinking of going the N=1 route (gasp!!!) and would love some input. I currently have an aluminum Cannondale Topstone (with a mix of 105 shifters and GRX derailleurs) and Canyon Endurance CF SL 7.0 (105 level). I love them both, but was thinking of going the N=1 route with a Lynskey GR300 with 2 wheelsets and GRX Di2. At my level, frankly the Topstone is just as fast as the Endurace when each is running my 50 mm carbon wheels and GP5000 TL’s.

I’m 6’5" and working (slowly!) to get down to 200-ish lbs. I’m as aero as a billboard and can’t be a weight weenie even when (if) I hit 200 lbs. I figure the Lynskey might be 4 lbs +/- heavier than the Endurace (currently 19.5 lbs) and I can set it up in a similar position. I don’t race, but want to comfortably join fast group rides (21-22 MPH at my LBS), do long road rides/centuries, and gravel rides (D2R2, unPAved).

With the COVID craziness, I might not lose my shirt selling the bikes I have now and moving to the Lynskey. Is this crazy? Is there any reason to think that bike would hold me back for the fast group rides?