Kapusta

Folks, the OP pretty well stated what he is riding:

I really don't think we need to be measuring the gravel diameter or analyzing moisture content, here.

Badger6

Yup. As I implied in post #13 above, 32mm slicks. Specialized Roubaix Pro are the "budget" option at $40, the Rene Herse slick options might be a little nicer rolling, no idea by how much, and they're pricier and probably won't last for thousands of kms.

Kapusta

Actually, in my experience, they do.

Yes, you did give a rec without overthinking it Not everyone did the same.

Badger6

Good to know, because someday Big S will stop making those tires I named and I’ll need to find something else.

chas58

I'll say, the one time where slicks FAIL in the dry is riding through a rut (i.e. dry tire tracks) that run in the direction I'm riding. Tires with a side tread can typically ride out - but slicks aren't even gonna try.

Badger6

That's where you gotta relax the shoulders and loosen the grip chas58 and hope the bike tracks out. It's worked out pretty good for me so far, except that one time...

Metieval

Ruts suck period! Even with knobs! Hate them ruts!

Branko D

Well, I built it up and did some rides to suss out any issues.
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Ritchey Swiss cross

Put on the Almanzo Pros in 33mm first, going to try 32mm GP5000s too. I can definitely hear the hum of the file thread on the road when riding at over 35-40 km/hr which gets louder at higher speed, but it isn't as much slower as I feared it would be, and when pumped to 65-70 psi the handling isn't objectionable. I'll see how much I lose in terms of grip with GP5000s on gravel.

A road bike which can ride offroad is really great fun. I have to change the rear derailleur to something with a clutch, though.

Thanks for all the insights on tires 😁
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HTupolev

Same. As performance-oriented road tires go, Rene Herse slicks aren't unusually minimalist on tread rubber. The ELs are typically around 3mm thick at centerline when new, and that's almost entirely tread rubber, since the casing is extremely thin and there's no puncture-protection layer. Here's a crudely-hacked-up cross-section of a Rat Trap Pass EL:



Since they don't seem to vary tread thickness by model, the wider stuff lasts longer. But I seem to get maybe 3000-4000 miles out of a Rat Trap Pass EL. The Bon Jons wear faster, but I still get a couple thousand miles per.

jonathanf2

I just picked up 32c GK SS tires and for poorly maintained city streets they're perfect. The SS tires have similar side tread as the GK SK knobbies, but with a flat center. I did a 40mph downhill and braking was excellent with no slippage. Also acceleration on the flats is very good compared to my wider 38c GK SK and TLC tires. I'd be fine riding these tires on rough fire roads and mild dirt/gravel trails. I also want to note the 32c GK SS non-plus casing seems quite sturdy compared to GK SK and TLC plus/+ tire casing (better puncture resistance). The SS tread is raised giving you a bit of extra rubber.

Overall I'm quite happy with a 32c gravel tire, leaning towards urban roads and gravel light surfaces.

chas58

Agreed. What we sometimes forget here is that a "gravel bike" is really just a versatile drop bar bike. On skinny tires I was very limited to where I could ride at speed. On a gravel bike - even with 32mm tires, it becomes for me the ultimate urban exploration bike, commuter bike, go out my door and sweat bike, gravel bike, etc. Its my N-1 as it can do (most) anything. 32mm is the ideal size if you want speed, light weight, and crisp handling. I've used 32mm gator skins, 4-seasons, and GP5000s for urban and non chunky gravel.

msu2001la

I did 30 miles of paved riding this morning on a brand new set of Donnely PDX WC's (33mm) tubeless at around 30psi. They are fantastic on dirt/grass and really supple, but felt pretty draggy and slow on pavement.

I also have a set of MXP (smaller tread but still knobby) 33mm in tubed clincher, and by comparison those feel a lot faster on pavement, but also usually run those at higher PSI (45-50psi).

Both of these tires still feel noticeably slower than GP5000 32mm tubeless.

Kanon25

Having this question myself I moved down from 35C semi slicks with tubes to Continental GP 5000 Tubeless in 32C for gravel riding. In my case, to get to the gravel I first have to do to about 15-20 miles of on-road trip to get out of town on to the trails.

Been a couple weeks and I can report this is working out pretty well. The on-road part is no longer a drag and on gravel (compacted to semi-loose logging trails with crushed limestone and sometimes dirt with rocks) the 32C tubeless does well. Have been out a few times now, varying the tire pressure from about 80 psi down to about 60 (label says 65-87 is officially OK) and in this range it feels secure on gravel and sharp and responsive on tarmac. Am running these on rims that are 25mm internal width (wheel manufacturer says its OK to use 32c tubeless tires on these, while the tire manufacturer is more conservative saying 21mm rim width is max).

On loose descents at speed my style is to be a bit more careful and more technical, and in the corners cut back on the speed a little, but but that’s common sense in all cases really. But actually the tire tracks better through the corners with this 32mm tubeless than the semi slick with file tread that I had used before.

Visually, 32mm it doesn’t look like a lot of tire volume but it’s enough - the tire feels nice and stable on the wide rim.

I don’t know why it took me do long to brave this. Should have done it way earlier. Less is more. I’m not very good with taking photos while out but here are a couple of the basic type of gravel. I can’t find any photos of the rockier downhills.

ksryder

Going the other direction -- I just got a second wheelset for my gravel bike so I could have road wheelset and a gravel wheelset. And by "road" I mean 700x40mm tubeless. Challenge Strada Biancas.

I've used the 32mm Strada Biancas in the past as road tires and I loved them, now Challenge offers them in tubeless and wider so I wanted to try them. Did >80 miles on asphalt Saturday and 30 miles mostly asphalt but some gravel on Sunday.

Honestly my average speed on Saturday was a bit lower than I expected but it was really, really hot and pretty windy, and it was a solo ride with some steep rollers so I don't know if this is a good sample or an outlier. As far as ride quality, they're great. Super smooth and comfortable. I had the PSI a little too low so they got a little squirrely in the corners but once I pumped them up to 40psi they were great.

For the limited amount of gravel I've had them on they're surprisingly capable. There's no tread so I have to remain seated during steep climbs but honestly that's not really different from my other gravel tires with a file tread.

We'll have to see how they do on a fast group ride. I wanted a fat slick tire for road rides but with the option of getting off pavement if the mood strikes me or if there's a detour, etc., and so far they seem like a good option for that.

msu2001la

Good examples and that looks like a really great place to ride.

I ride roads like your first two photos on 32mm GP5000's all the time and find it to be a perfect combo. The 3rd photo would give me pause... I'd probably slow down and gingerly pick my way through something like that, and if it went on for miles I'd want more tire. Those larger rocks can be tricky on narrower tires.

The 4th photo is getting to the edge of what I'd be comfortable riding a road tire on. It looks perfectly passable but I'd probably be more comfortable on something like a 35mm tire.

I don't think any of those roads would require, or even benefit from a treaded tire. Slicks would be fine, it's mostly just a volume game for providing more cushion and protection from sharp rocks.

msu2001la

Update to this. The PDX's weren't slow and draggy, my front brake was. Somehow my caliper got knocked out of alignment and I didn't notice - and oddly the rotor rubbing wasn't making any noise. It wasn't until after I got home and was cleaning my bike that I noticed the front wheel wasn't spinning freely.

After fixing that, things felt very normal on the PDX's. They feel basically the same as the MDX's on pavement, which is to say fast... but slightly slower than the GP5000's.

As an aside, I managed to find the top half of a broken beer bottle hidden in the grass while warming up for a CX race yesterday. It cut 1" long gash in the sidewall of my brand new PDX WC tubeless tire - causing instant flat and blew sealant all over my bike. I took the tire off, used a dollar bill to boot the gash, and inserted a tube into the tire - all just minutes before my start time. I rode the entire race assuming it would go flat at any moment, but it held with about 35-40psi, and got me through the Cat 4 race and also was good for the 15 mile ride back home after. I'll be buying a new tire, unfortunately.

mstateglfr 

That is a brutal incident and some great in the field fixing!

Kanon25

I have done more stretches like the one in the 3rd photo on the 35mm semi-slick and it was no different, still need to just take a little bit off the speed and pick your path and all is fine. But yes, on 32mm that kind of gravel it's fine and even fun in stretches - but maybe not miles on end. If the trail is like that the entire time, that's really more getting into MTB territory anyway - 40+ tires and flat handlebars.

4th photo was perfectly OK on 32mm at tubeless pressures. No worries at all.

chas58

I've done this for years. Some comments:

I don't run those tires more than 60psi (well, I'm hookless, and that is the max psi they are rated for hookless). But I wouldn't go more if I could.
That is the rear, in the front I'm more like 45psi (cause - weight distribution).

If I'm going to be doing more than 1/3 of the ride on gravel, I'll put a 40mm gravel tire on the front (Terra speed, so its fairly fast).
Realistically, you probably get 70% of your power loss through your rear wheel (+/- 10%), so there isn't much of a disadvantage to putting a fast gravel tire on the front. The advantage is being able to run harder through that chunky stuff, and 32mm tires are a nightmare if your front tire sinks into soft gravel.