espressogrinder

I am 5'8" and 152 lbs....do I really benefit or need anything larger than a 40mm tire? Do I get the same benefits that a larger/heavier rider gets from so much volume? I understand that the road conditions dictate what is required and there is never a perfect size and tread pattern tire for everyone. Does my bike/bodyweight/40mm tires at a combined weight of 172 pounds perform to the equivalent of 200-220 pound setup rolling in 40-46mm tires? Is there a point of diminishing returns (rolling resistance, tire weight and mass) that a rider of my size does not benefit from such a large tire?

mstateglfr 

I am another 80# added to your frame and use 25mm tires, 35mm tires, and 40mm tires for road riding(road meaning things cars drive on- so paved and gravel).
For me, the tire width is based on use, not my body weight.

I use a 40mm tire for my gravel riding because all around me the gravel roads vary significantly depending on county and time of year. Sometimes really hard pack, sometimes loose, sometimes thick, sometimes thin, etc. I have found that a 40mm tire offers a good mix of performance on the harder packed surface while still floating over looser surfaces well enough to stay in control.
I think I would use a 40mm tire even if I were 175# as a thinner tire would still dig in too much for my liking...i think.

I get that idea that a lighter rider will naturally float over surfaces more than a heavier rider due simply to less downward force, but even my 10yo daughter can dig her mountain bike tire into softer single track- so it seems like loose surface is loose surface regardless of rider weight.

ATPAH

Based on my experience on various tires ranging from 23mm to 3 inches, I'd agree that tire width relates to use/terrain, whereas tire pressure varies based on the weight (and riding style) of the rider.

Abe_Froman

I'd agree with this....it just is based on how much width you need to avoid the tire slipping in between things. Think of it more in terms of a tire rolling across a sewer grate in the pavement. If the tire is 1", and the grate has a 1.5" gap....you're probably going to have a serious problem. If the tire is 2"...it is going to take a whole lot of extra weight to force the thing through there. 50lbs likely won't make any difference at all.

chas58

I'm a little heavier than you, and can use 40mm tires for everything. I even used to mountain bike race on them (they are super light!!!).

For me, it boils down to what tire pressure I want and how much of a hit I will take. 40mm tires with no suspension are not going to be happy taking a 40mm tall "hit" at speed. That means I can't go downhill on a mountain bike course with 40mm tires unless I have a lot of air in the tire to prevent it from bottoming out.

On the road I want 60-80 psi for good responsiveness
on gravel I may be between 40 and 60 psi
on technical single track I may be between 25 and 35psi.

So, I'll take a tire that matches the pressure (28-32mm, 40mm, 55mm respectively).

chas58

to address your weight/size question - determine the pressure you want, and pick your tires size based off of your weight using the original chart for pressure-size-weight:
(I know, this was made before gravel and larger tires were popular, but this chart started the whole trend:

JonathanGennick 

Part of the fun is in experimenting. Does your bike have clearance for wider tires?

DomaneS5

40c is perfect for gravel bikes, no matter the weight of the rider. Anything slimmer than 35c would be too narrow. If I need a wider tire, I ride my 29er hardtail mountain bike.

JonathanGennick 

I disagree. 40 is a good width to be sure. But a rider carrying extra weight can benefit from a wider tire. I run my 47 mm tires at 25 and 30 psi over rough ground. Could I manage those pressures in a 40 mm tire. I'm not so sure.

DomaneS5

My gravel bike can go up to 45c, but I really like the 40c's. I don't know if I'd notice much difference between 40c and 45c to justify upgrading... kinda like 25mm vs. 28mm on road bikes.

JonathanGennick 

I see your point. And does anyone even make a 45?

On 700c rims, I'd probably hold at around 40 myself. Or low 40s. Back when I had my Fargo built, I started with 2.3 Big Apples. Too tall. Worked my way down to some 1.9 Bontragers. Liked those better! And always had wanted to buy some 28" commuter tires from Schwalbe in the low 40s, but ended up tearing the parts off that frame to use on something else before I got around to buying the Schwalbes.

I'll rebuild that Fargo someday, and I'll be looking at 40-42 when I do.

The 47 mm tires I run are 650b. The outer diameter is working for me, on that smaller wheel size.

DomaneS5

45c gets into 29er territory with 1.75" tires. If I recall correctly, I've seen a few tires offered in this size on JensonUSA's site... it's been a few months.

WTB makes a 45c... the Riddler. I have 40c WTB Nano on my bike.

motorthings

i just took my 33c mudwrestlers off to put the 40c Nano TCS back on...having proven to myself that the Nano's seem faster and smoother, and hook up better in the scree.

DomaneS5

I have about 500 miles on my Nanos and they've been great... smooth and dependable on gravel, dirt and pavement. I run them around 40-45psi.

motorthings

i've been experimenting with lower pressures.
i weigh 140 and have been running 35/40 offroad without any issue

u235

It's up to you. I split my gravel bike between on and off road and use at least 40c. If I was road only (which I have been recently) I still use 40c. I don't care what advantage I might be losing in speed or efficiency, it is not making up for the flexibility, confidence, and comfort.

I've had good experience with Conti SpeedRide in my conditions. Rolled better than the Nano for me. For more MTB type conditions, I ride my heavy tank hybrid with 2.x tires. I've lost 70 lbs in the last 2 years and still use same tires, maybe just more air in them now.
Get input form others to learn something or get a different view point and experiment but in the end...Trust your own opinion as you are the one riding your bike, not those other people.

chas58

I have some 45s. I don't really use it much. Mostly I swap between 32 slicks and 40mm short knobs. If I need to go over 40mm I tend to take out the mountain bike.

RJM

Yep, agreed.

In fact, I think a good, light, hardtail xc mountain bike with the proper gearing is an excellent choice for a gravel bike.

DomaneS5

I'm paranoid about pinch flats on the gravel bike since I'm usually riding in remote areas.

motorthings

i take it you are not running them tubeless, then?

Donto

I pinch flatted last week on a mis-timed curb jump before 'cane Irma wrecked the past week. Today I went into LBS and picked up a Stan's tubeless kit, goodbye tubes!

DomaneS5

No... but wheels on gravel bike are tubeless compatible.

ATPAH

I weigh 175 and have been running my Nanos at 25/35. That may be a bit low (at least for the combination of bony dirt roads and smoother singletrack that I frequently ride), as I've bottomed-out the tire a couple times. No burps and the rim's are still true and round, but that may not last forever. Those pressures were good for less rocky trails and roads, however.

motorthings

man, you gotta go tubeless!

mstateglfr 

Why the 'gotta'?

I dont think about the tires on my gravel bike. Fill em up to the PSIs I want before riding, and then ride. Thats it.
What is being missed by having tubes? The PSI i have both tires set at seems to be a nice balance between comfort and not so flat that the tires feel slow and squishy.