It is not as simple as tire width, as yes, tire width does impact speed to a very small degree, BUT YOUR BICYCLE's GEARING will play a much larger role.

Look at some of the available free online bicycle gear calculators (GOOGLE: bicycle gear calculator)

Basically, if your husband's road bike has the HIGHEST GEAR of say for example 52 front and 13 rear and he is comfortable pedalling away on flat-land or downhill in this 52 front TEETH and 13 rear Teeth configuration.................he's gonna be motivatin' and moving out, AND YOU WILL HAVE ZERO CHANCE OF KEEPING UP WITH HIM UNLESS YOUR BICYCLE ALSO HAS the HIGHEST GEAR of at Least That. Why? Because for every revolution of the crank, his bike will be traveling farther in distance THAN say something with a 48 front and 14 rear configuration.

You could also have for example a lighter, even a carbon fiber bike BUT if the alloy/steel bike is also light enough and has superior gearing than the lighter carbon fiber bike, the alloy/steel bike may be in fact faster---------------------THIS ALL DEPENDS ON HOW WELL THE GEARING IS MATED TO THE INDIVIDUAL CAPABILITIES OF THE POWER-MAKER(the human rider)........................................Think of this in terms of the fit of a nice dress or a gentleman's suit-------- off the rack might be acceptable to many, but many may benefit from having a tailor make it fit you better.

Hey you recall, your 8th grade Algebra don't you......sure you do, because you may have helped tutor your kids with their homework.

There is a super simple way to compare.

DIVIDE THE NUMBER OF TEETH ON THE FRONT SPROCKET by The Number Of Teeth on The REAR SPROCKET.

MULTIPLY That RESULT BY THE Diameter Of The REAR WHEEL TO OBTAIN THE "GEAR NUMBER".

(trust me on this, USE 27 as the diameter of the rear wheel for every 700C(622mm) or 27"(630mm) bicycle wheel....

Use 26 instead of 27 if your bicycle has 650C wheel, or 26x1 3/8 schwinn (597 mm) or 26 1 3/8 industry standard (590mm) or 26 mountain bike(559mm)

TO DETERMINE THE DISTANCE TRAVELLED WITH EACH REVOLUTION OF THE PEDALS:

You Take that "GEAR NUMBER" and Multiply it by "pi" ( use 3.14 for "pi")

so this "GEAR NUMBER" x 3.14 = the amount in INCHES that the bike travels for each revolution of the pedals.

Convert to FEET by dividing that amount for inches by 12.

YOU CAN ESSENTIALLY MAKE YOUR OWN COMPARATIVE GEAR CHART.

CALCULATE FOR EACH OF YOUR POSSIBLE GEAR COMBINATIONS and COMPARE TO OTHER BICYCLES, OR OTHER POSSIBLE CONFIGURATIONS THAT YOU COULD REALIZE FROM CHANGING SOMETHING WITH RESPECT TO THE BIKE'S GEARING.

Here is a simple example:

45 teeth front sprocket and 15 teeth rear sprocket combination..........

45 divided by 15 = 3

3 x 27" wheel diameter = 81 GEAR

81 GEAR x "pi" = distance in INCHES the bike travels with each revolution of the pedals

81 GEAR x 3.14 = 254 inches

254 inches = 20 feet

Yes, this is super-simple BUT IT DOES Provide a Meaningful Comparison that even a ten year old would understand.

Your online bicycle gear calculator does essentially the same thing.

I know the using (27) for wheel diam in inches simplifies things since essentially 622mm(700C) is very close to 630mm(27" tire).

IF YOU'RE COMPARING BICYCLES WITH THE EXACT SAME WHEEL CONFIGURATIONS, IT IS NOT GOING TO MATTER, BECAUSE YOUR COMPARISONS WILL BE MEANINGFUL.

Sure, you can get more scientific but I doubt that that the differences will amount to any significant changes to your findings in most cases.

Gear ratio that the bike has and the ability of the human to spin the pedals is the MOST IMPORTANT THING, assuming all else is relatively equal in weight, etc...

Those online bicycle gear calculators can take things farther by giving you ability to see the estimated difference between PACING the pedal cadence.......

Just remember that hypothetical gearing calculation is just hypothetical UNLESS you can realistically handle such a task....

........................What some super-stud can do is meaningless to normal mortal individuals.................thus in order to benefit from gearing, you must realistically get in the ballpark (OFF THE SHELF) of what is beneficial to YOURSELF as the Human power (you as the rider!!).

You may or may not be able to keep up with someone super-strong that can make any bike really move...................................you may need to ask if he'll be more courteous and moderate his need for speed so that both of you can enjoy the ride together. Fast isn't everything. Enjoy the ride.