For most, if not all, manufacturers, this will void your frame's warranty.

Is this the OP's first skinny tire bike? If so, you may need to adjust your expectations a little bit. Try riding on 23's or 25's and go back to your 28's. I guarantee the 28's will feel like fluffy clouds.

You can drop a lot of money into this for carbon bars, carbon seat post, thicker tape, new(larger or more supple) tires. Do what you like, but if this is your first experience with bike with sub 30mm tires, just give it some more time to adjust.

That's not what most current studies show.

Then again, I don't know what you mean by "big, fat, low pressure tires", 5" at 8 PSI?

While I don't disagree with the fundamental argument, in addition to not being precise in the difference in volume using the circular sections shown, a tube is not circular in section, unless you're talking tubular. A not insignificant part of the tube is exactly the same size regardless of the tire size unless you change rims.

For example:

http://4.bp.blogspot.com/-LP9qaO066E...sentials02.jpg

Actually you are the only one who has mentioned being slowed down by fatter bigger tires. I only posted that they suck more of my energy from me. And that has been my experience. Granted the studies imply that isn't the case during testing... and I am not arguing with test results.

Heck... I love my big old 700 35c gravel bike tires... it's a great ride both in comfort and on wet/slick roads. But the bigger HEAVIER tires (or even just wheels) do require more energy to get spinning... or increase their speed. I also realize.... that as far as rolling resistance.... the weight doesn't appear to be well represented in testing (particularly cyclists weight).

But all this is academic and has nothing to do with my advice to the OP... which I stand behind.

This is definitely possible. This is my first bike as an adult. I’ve been riding it regularly for over a year but have limited experience riding other bikes. Therefore, I’m really not sure how the ride quality on my bike compares to a typical bike.

I will say the LBS mechanic I spoke with seemed to agree with you. He said my tires were already plenty big and going even wider wouldn’t make a big difference.

The ride quality issue is not apparent when I’m on the roads. But I prefer the greenways because of the scenery and lack of cars. I’m fortunate to live in an area that has an excellent trail system.

My bike is so comfortable that going over bumps is the only thing that helps keep me awake.:lol:

Sorry, I guess I don't know what you mean by "sucking more energy". Any understanding I have of that would go along with being slower. But maybe you mean something different.

What tires do you have on your gravel bike?

That's OK... I don't know what lab equipment you used to measure the rolling resistance of your tires either. So... unless you just "read" something from somewhere.... wouldn't we just be sharing links if we didn't report our own actual experience?

I just bought the bike last January and I am still using the stock tires. I use the bike primarily for a winter/rain bike. I've post on the forums about it a few times. It has Schwalbe G-One tires.

At the only place it matters...where the rubber hits the road, literally...the tire's profile is round...ish. It's actually kind of squashed but that still doesn't matter too much. The footprint on the road is an ellipse and changing the diameter of the tire only changes the area of that ellipse slightly and the volume of the tire above that ellipse changes very little even when going from a 23mm tire to a 40mm.

Yes, a wider tire lets you drop the tire pressure for a more comfortable ride.

But in terms of performance, quality/suppleness matters too. Not sure how happy you'd be riding slower when you could be riding both more comfortably and faster.

Someone above recommended Compass tires. I hear they're excellent, but $$$ for a pair.

There are cheaper (though not cheap) options.

I just replaced a pair of 28mm Vittoria Randonneur IIs with 28mm Continential GP4000SIIs. The Randos were nigh bulletproof, but compared to the GP4000s, they're like pedaling through mud. No joke, I'd say I picked up 30 watts/2mph just by changing tires. I'm exceedingly happy with the GP4000s.

When spring rolls around, I'll probably try the GP4Seasons in 32mm as my road tire for my gravel bike. In fact, that's probably what I'd recommend you try. A tiny bit slower than the GP4000s, but (allegedly) better durability.

I have only anecdotal evidence, but would not consider a carbon seat post. I met someone last week who had a catastrophic failure on one, and to prevent impaling himself, took a fall and badly fractured his forearm. Years later he rides a recumbent due to injuries sustained in that fall.

Using a too narrow seat post with shims (as one suggested) also sounds, to put it mildly, like not the best advice.

Tires and wheels, and the rest of the bike in good order will make a difference, a better saddle, and preparing for bumps, moving slightly off the saddle, as if on a horse :), or maybe even considering a steel framed bike might also help.

I didn't review the thread again(so you may have already done this), but why don't you try putting in 5-10 psi less in your tires when you plan on riding the greenways. It won't cost you a thing. Just because the tire says max psi is 120(or whatever), doesn't mean you need that. I am about 250 lbs on 28s and ride at 80/85 F/B.

He is 100% wrong. Period. Fact.

The area of the tires contact patch is not a function of the tire size. It is primarily a function of the tire pressure. A small tire and a large tire with the same pressure will have pretty much the same contact patch.

However, the larger tire can be run at a lower pressure, and therefore will have a greater contact patch.

The change in contact patch area is inversely proportional to the change in air pressure.

Using this tire pressure calculator for comparison purposes, consider a tire supporting 80 lbs.
For a 23mm tire, you get 82 psi recommended.
For a 37mm tire, you get 36 psi recommended.
Do the math and that is an 228% increase in contact patch size.

However, I don't understand why you think the size of the contact patch is the important thing to be focusing on here. It is not what determines ride comfort (though it is directly proportional to tire pressure, which does have a lot to do with ride comfort).

Also, I don't understand why you are focusing on the volume of the tire above the contact patch (or what you even mean by that). What is the significance of it?

Agreed. He is dead wrong.

Yep.

I won't argue about speed, energy sapping, acceleration, climbing, etc., because there are so many other factors of the tire's design that affect everything. It's a complex recipe, and there are certainly some compromises here and there. But increased air volume = increased comfort, plain and simple. It doesn't get any more simple, really.

Get an old school steel framed bike. Can't beat them for comfort.
Jon

The entire tire system is part of the suspension. It's not the cross section alone and it's not the contact patch alone, although those both can have a small effect. The biggest part of a tire's squishiness is from the fact that air compresses. If that were not the case, then tire pressure would affect only the size of the contact patch, not comfort. A lower pressure allows the entire volume of the tire to have a small increase in pressure when the contact patch changes as a result of hitting a bump. The higher the pressure, the less the air can compress, which means the contact patch will not change as much meaning there is less compliance and a harsher ride.

I thought I pointed all this out way back on post 3. Surely no one is arguing that I was wrong about that :eek: