My wife has a Huffy rock creek bike. She wants bigger tires. I realize the bike is not worth putting money in but MY WIFE WANTS BIGGER TIRES. The rims are 1" wide on outside. The 26" tires are 1.9 wide. What is the widest tire that will fit this rim? There is plenty of side clearance front and back. Thanks for any help.

Any tire that fits in the frame should work fine with those rims. Likely something in the 2.3” range would be the frame’s limit.

Yup. Back in the day when "super wide" MTB tires became common, you would often see them mounted on pretty narrow rims. Sub-optimal, but not really a significant problem Unless the OP's wife is pushing performance limits, anything that fits the frame is OK.

The widest tire that will fit in that bike is the widest tire you can put in that rim.

Before you go any further- how much tire pressure are you running? a lot of people run way too high tire pressure on MTB's. If you are running more than 30psi, it's too high.

We tried 32 front and 35 rear.

26x2.5" might fit, more likely 26x2.35" is the biggest you'll get in the back. There's usually more room on the front, and no need to run the same size both ends. The handling won't be great but hey, it's a Huffy. The tyres should work fine, as long as you keep them inflated, when they get soft the steering will feel vague and wallowy, but too much air and they will feel harder than the 1.9s.

a more supple sidewall tire in the 2.125" size range will be worlds softer to a rider... the stock tires on huffys are low end bricks.
Try something like this...
search: Maxxis DTH Urban EXO/SkinWall 60 TPI 26´´ x 2.15
if she's not riding on mud regularly... smoother ride, easier rolling, etc.

these are great tires...
Search: Kenda Small Block 120 TPI 26´´ x 2.10 MTB

you can always stop in at your local bike shop and see what they have in stock or recommend, too.

it's not so much the width of a tire that makes it ride easy... it's the construction of the tire.

Flat resistant tires, tubes filled with slime, and thicker tubes ride badly... the thicker tubes act like an extra ply in the sidewalls.
just changing to thinner tubes will make a tire ride better.

You might also want to check out Sheldon Browns tire sizing article as 26" has roughly 4 different bead diameters. Grabbing any 26" labeled tire might be the wrong one for your rims. Kind of a long article but just scroll down a few paragraphs to the "B.S.D." heading for a quick explanation. Explains the ISO (International Standards Organization) sizing which is listed in metric measurements and printed on almost all tires. There are also some charts in the article comparing the different tire sizing systems to ISO. This is the only system that tells you what the actual BSD sizes are if you are in doubt. Tire Sizing Systems

All that is true, but 99% of the time you will bumble into the correct tire as all the sizes except ISO 559 have gone out of fashion, especially in wide. Many big box store bikes and also Specialized and perhaps others are still make bikes today with ISO 559 "Mountain Bike" rims.

I just put 2.35" tires on a narrow rim on one of my kid's bikes. They look really cool! I can't speak to how they ride. Expect a little aggravation if you install the tires yourself. First, special wide tubes are In order. Second, getting everything mounted up is a slightly different challenge (not hard, but different). More pumps to inflate. Finally, they may not squeeze between your brakes fully inflated. The little hairs sticking out of the tire may buzz the frame.