700c x 40mm or 650bx 47mm

carytb wrote: If I'm being honest with myself I value comfort more than outright performance. Thanks

I will put my very unpopular opinion here:

My backstory - I am 6'2'' and 150lbs on a heavy day. 

I think 700x40 is a total pig of a tire size. Slower than 700x35 on pavement by a big margin, not much better in the soft stuff than 700x35. The wheel gets really big, and really slow feeling.

My 650x47 setup is MUCH faster rolling on pavement, much better feeling in the soft stuff.

For the record my 700c wheels were 1500g, with 500g tires. My 650c setup is 1700g+, with 500g tires. The 650c SHOULD feel worse given more rotational weight, but the reality is they just work better. Ideally I would rebuild my wheels with lighter rims and have 1500g 650c wheels, but I have other things to buy first.

The reason I tell my weight is the amount of man I use to push the big tire down the road - it makes a difference. There is a reason really big dudes love a Cutthroat with 29x2.1 tires - they are 225lbs of muscle moving the bike down the road. I am a wee fellow and feel the 700x40 is really just the worst of both worlds. Not fast on pavement, not floaty in the soft stuff.

Also, FWIW, I have ridden 29er mountain bikes exclusively since 2007. I have never even owned a 26 or 27.5 mountain bike. So one would think I am a big wheel fanatic, but the back to back riding showed me if 700x35 doesn't cut it, 650x47 is the answer. 

Of course, your mileage may vary.

PoolBoyMatt wrote:

I will put my very unpopular opinion here:

My backstory - I am 6'2'' and 150lbs on a heavy day. 

I think 700x40 is a total pig of a tire size. Slower than 700x35 on pavement by a big margin, not much better in the soft stuff than 700x35. The wheel gets really big, and really slow feeling.

My 650x47 setup is MUCH faster rolling on pavement, much better feeling in the soft stuff.

For the record my 700c wheels were 1500g, with 500g tires. My 650c setup is 1700g+, with 500g tires. The 650c SHOULD feel worse given more rotational weight, but the reality is they just work better. Ideally I would rebuild my wheels with lighter rims and have 1500g 650c wheels, but I have other things to buy first.

The reason I tell my weight is the amount of man I use to push the big tire down the road - it makes a difference. There is a reason really big dudes love a Cutthroat with 29x2.1 tires - they are 225lbs of muscle moving the bike down the road. I am a wee fellow and feel the 700x40 is really just the worst of both worlds. Not fast on pavement, not floaty in the soft stuff.

Also, FWIW, I have ridden 29er mountain bikes exclusively since 2007. I have never even owned a 26 or 27.5 mountain bike. So one would think I am a big wheel fanatic, but the back to back riding showed me if 700x35 doesn't cut it, 650x47 is the answer. 

Of course, your mileage may vary.

I make the 650c blunder often. I equate 650b as small mountain, 650c as "small road". Yes, 650 road uses the same rim size as 650 mountain. It is something I stumble around on all the time.

I guess I should be even more specific:


my 700c wheels weighed in at 1500g (Crest laced to 350s) and I really liked them with a tire that measure 35/36 at full pressure. It was a dreamy ride. Even with "pedestrian" tires like a Specialized Roubaix 30/32 (measured 35-36mm at 40psi after stretching time). 

My 40 tires were a set of Terrene Cannonballs. They made the bike feel dead. The bike isn't snappy, it isn't good.  My thought is once I get a low enough tire pressure the tire doesn't just bounce off the rocks in the road, it feels really, really dead on pavement. I was running around 28psi. Years back I rode 700x40 Schwalbe tires on my Cross Check. Reminded my very much of the same feeling. Didn't have any snap, didn't shred singletrack better than my 35s. 

I didn't pull of a set of Bon Jons ExtraLight Tubeless and install a 27tpi wire bead. The tires are pretty much spot on comparable products.

My 650 setup is a set of stock DT Swiss wheels with 350 hubs and a DT mountain rim - over built for what I need on my drop bar bike. They weigh in around 1700-1750g. I can't remember. I just knew it was around 200g+ more than my 700 wheels. I run WTB Horizons. I am running those at 30-32 front, 35 rear. Why so much more? I decreased pressure until they felt like the didn't bounce around uncontrollably on gravel. (A low enough pressure to conform to rocks smaller than egg.)

I am employed in the bike industry and have the same feeling about 700x40ish tires everytime I hop on a bike with them. It just doesn't FEEL good. Reminds me a lot of 29x3. The thing has no snap, without ENOUGH added benefit.

Like I concluded my last post, your mileage may vary - but I don't think it is a product of crappy tires, I think I was dismissed as comparing apples to oranges when I laid of the weights that explained why due to the weight my 700c should be better, but alas I feel better on the 650.

I have also spent a ton of time "underbiked": racing rigid mountain bikes in the Ozarks for 50 mile and 6 hour events, I have done Rouge Roubaix road race on tubed 700x25 tires, and I have raced gravel races on 700x32 Vittoria TNT tires (the conti gator skin of tubeless tires). I don't feel like I need a ton of bike. So again I say 700x35 (fast) or 650x47 (full comfort and still feels fast)

Your mileage may vary, but I am running 650 for at least the next year.

PoolBoyMatt wrote:My 40 tires were a set of Terrene Cannonballs.

Found the problem

chunkyhugo wrote:There was a lot of discussion about this before last year's Reiver. I think people feel daunted by the prospect of a 200k gravel event and worry about all sorts of things. My bike handles a maximum 700 x 38 tyre, so I'm more limited than some people, but I used Clement x'plor 36 tubeless and had no comfort issues at all. The tracks are quite good surface wise, with only the occasional rougher sections.

carytb wrote:

Thanks, that's good info. I think I'll see what the Knard 41's I've got are like running tubeless then I'll make a decision.
Cheers