My wife and I both bought some entry level Specialized bikes over the weeked.

I got a base model Sirrus and she got the Crossroads. My tires are Specialized All Condition Sport, 700x32c and hers are Specialized Hemisphere, 700x38c.

When I we were riding on the road it seemed like she was working a lot harder than me to get the bike going. I assumed it was lack of fitness. The next day we rode again and switched bikes and I have to say I was working hard the whole time. I couldn't just ride and coast as easily.

I'm wondering if she switched out her tires if it would make a night and day difference on the tarmac. If that was the case I probably want to buy her a different set of tires.

Sorry if this is a beginner type question, it's our first bike other than the Huffy we rode back in grade school.

Tread type and pressure make the biggest differences in rolling resistance.

Go to 700 x 28's....

Rolling resistance as a result of tire width, rubber composition, inflation pressure and road conditions can certainly vary.
https://www.terrymorse.com/bike/rolres.html

There are numerous other discussions, some in great detail, on the Internet - do a simple search using the terms: bicycle rolling resistance.

To quote one of them: "In general terms, the total drag of a cyclist will consist of 80% tire rolling resistance and 20% wind resistance at 10 km/h or 6 mph. At 40 km/h or 25 mph the numbers will reverse, with total drag consisting of 80% wind resistance and 20% tire rolling resistance."

tires do make a difference. also, were you on the same gears on both bikes?

this tells me that low rolling resistance tires are important for accelerating and leisure riding, but not as important for distance riding (aerodynamics become more significant).

No. That's not the point at all. What it means is that lowering drag is of most benefit at higher speeds. What this particular quote doesn't address is wind speed. The higher the wind speed, the more an aero position helps you. Even if you're only pushing 12mph into a 25mph headwind, that aero benefit is going to save you some suffering.

It's not as though rolling resistance doesn't matter at high speeds. It does. Nobody is going to maintain 25mph+ speeds on big tires for very long. Higher rolling resistance means more work. That's an especially important consideration in long distance riding.

Long distance riders often opt for larger, heavier tires not because rolling resistance doesn't matter over long distance, but because they have added layers of puncture resistance, and a more plush ride. It's a trade off that many think are worth it, but it's a matter of personal preference.

In addition to the other comments, it could be the hub bearings are misadjusted, as these are new bikes. Sometimes they get shipped waaaay too tight.

Do the wheels spin easily on the bike when it's suspended in the air?

The thickness of the rubber in the tread and sidewall has a huge impact in addition to the other factors. Some flat-resistant strips are quite thick. Rubber has internal friction when it flexes. The thickness of the innertube is important too.

Not so. The rolling resistance does not decrease as you go faster, it's just that the wind resistance increases exponentially as you increase speed. Think of it this way: rolling resistance is constant regardless of speed (not really true, but close enough for illustrating the point), but wind resistance increases dramatcally as speed increases.

Going back to the first post in the thread and re-reading it, I'm going to assume a couple things I didn't in my first response.
1. You're both going to ride primarily on pavement (tarmac).
2. The wheels/rims are the same size on both bikes.

Given that, putting a set of Specialized All Condition Sport tires on her bike is a "cheap, easy fix" - especially as you've already confirmed that they seem to make the ride easier for both of you. Stick with the narrower width range (23-28) IF you're not going to carry any medium-heavy loads like for touring.

OTOH, you will likely find that after a couple weeks of riding, you really won't notice as much difference riding either bike "unloaded" as your muscles should have adapted and gotten stronger, your pedaling technique will have improved, and even small improvements in your basic bike handling skillls will make things llike starting from a dead stop easier. So, you could use the "more difficult" tires yourself and just live with what you have as you adapt - or temporarily put off making a decision/change for a couple weeks and see if what I said here is applicable.

Good suggestions. We are actually ride a mix between both but we're now thinking of commuting on bikes (I tested out a route that avoided the faster busier roads and it was a 45 minute ride). Rims are the same, so I'll need new tires / inner tubes. I'll check the cog but if it's a direct match to her bike (I think it is since it's two base Specialized hybrid 7 gears) and maybe we can just swap tires.

The All Condition Sport tires are horrible on anything slippery. I tested it out riding in the wet trail / mud just so I can push the bike. Only fell once but I can definitely feel the rear slipping enough to lose confidence.

Swap tires between the bikes. That costs nothing but time, and would make for an interesting experiment.

I wonder too, whether the geometry of the bikes might matter some here. The Sirrus is meant for speed. I recall that the Crossroads has the rider in a fairly upright, comfortable posture from which it may not be possibly to generate the same leg force as easily as from the Sirrus.

Easier than switching tires you might be able to just swap the wheels.

Another beginner question but these are the two cassettes, so will a direct swap be fine or will I fine slack / tension on the chain?

SRAM, 7-speed, 12-32t
Shimano, 7-speed, 14-34t Mega Range

You might need to adjust the rear derailier if you do that.

@pixel, njkayaker is correct. I had not thought about the cassette range being different. You might or might not get away with swapping rear wheels. There is risk of damage if the chain on one bike isn't long enough to accommodate the extra two teeth on the rear cassette from the other bike. You probably should not take the risk. Just swap the tires instead.

An extra 20 Watts (the difference between good and bad road tires without tread) can be the difference between working hard and blowing up, or working hard and pain.

Technically I did want to buy a bike for fitness. So working hard should be more important than distance. But so far I really love riding when there's a destination, the further it is the more satisfied I am

A beginners thought. Since you mention it and don't seem to know a whole lot yet.

If the bikes are new, are you sure the rims are straight an the brakes are centered. I know some experienced riders that make the mistake of not checking. The ap should be even on both sides of the brake surface throughout the entire circumference of the rim while rolling.

Pick up the bike rear first and spin the wheel, should spin freely. Then do the same for the front. If the rims are crooked (happens alot in new bikes) the rim could be rubbing. HEY YA NEVER KNOW!

I like to have a target too.

Too much thinking and pontification here. The short answer is yes, If you put her tires on your bike and your tires on hers, your positions would be approximately reversed. Somewhat narrower, less-heavily treaded and higher pressure tires on her bike will make it easier for her to keep up.
Your tires will go on her rims and fit on her bike, so you could swap them and see how it works. Hers will go on your rims but might not fit in your frame (I don't know how much room there is on a Sirrus). That's a 20-minute experiment that will answer your question, plus being good training for the inevitable flat tires to come.

Nobody told me when I bought my road bike that the tire air pressure should be checked before each ride. Hope the OP is doing that.

I just switched from all-weather commuter 700x25 to a faster 700x23 tire just on the rear wheel. My avg speed went up over 1/2 mph over my usual loop 25 mile course. I didn't get faster on the very steep uphills (4mph) or on the steep downhills (33mph), it was everything in between. The bike just feels more responsive and rolls easier. I'll be changing out the front tire within 2 weeks before a fun "race".

I'll put the commuter tires back on when I find myself riding solo in the dark again - they are almost flat proof and a little more comfortable on rough pavement. I've worn out 3 sets of these armadillos without a single puncture, ~7K miles.

No one told me this either. I wasn't sure if bike tires are subject to much variation from a few rides.

I only have a PSI gauge for schrader valves, and probably need to invest in a good bike pump with a built in gauge.

Oh before I went out for my first ride I seated both the tires and made sure the brakes weren't rubbing. But this wasn't by choice, I had to remove both wheels to transport two bikes in my car.