My Experience With Chico Walking On Hard Floors
I think that it is a pretty common Chihuahua problem to be afraid of a different floor surface s than they have been used to and to be afraid to walk on hard floors. One of my Chihuahuas grew up in our house that had carpet throughout except the kitchen floor. It was never a problem because there really was no need for him to be in the kitchen or to walk on hard floors, therefore I felt no need to address it. We fed him so that the bowls were in the kitchen, but he could stand on the carpet to eat and drink.

When he was about 10 years old we moved to a bigger house and all the floors are hardwood or linoleum except the bedrooms. He would freak out and refuse to walk on them. Now it was definitely a major problem! He had to walk on hardwood floors to get to his food and water bowls and to get to the door to go potty.
A Video of My Chico When We First Moved
Now I know how important it is to expose your dog to all different surfaces. It is best, of course, to do this when he is a puppy because it becomes harder when they are older and have already developed the fear. See my post for more on this subject: How to make your Chihuahua a happy confident dog.
Why Is It That Some Dogs Are Afraid to Walk on Hard Floors
It is possible that the reason why has to do with physics and the differences in perception in humans and dogs. I don’t know about you, but I find physics hard to understand. So, I’ll try to explain it as best I can.

According to one source, in animal consciousness, there is no such thing as an absolute frame of reference; in other words, they don’t understand that something can be motionless while something else is moving. For instance, when they are riding in a car at 30, 40, or 50 miles an hour objects flashing by are to them running prey. So, when a dog walks on a floor, he has no perception that although he is moving, the floor is actually still.
If walking on carpet, they feel safe because they can get a grip, so to speak. But when they encounter a hard surface such as a hardwood or tile floor, they don’t understand why no matter how much they clench their paws they can’t get a grip or that the floor is not moving. The faster they try to run to stable ground, the faster the floor seems to be moving. It is as scary to them as a moving floor in an earthquake is to us. WOW! Who knew? I didn’t. But you can train your dog to walk on hard floors.

Knowing this now gives me a whole new perspective of why my poor Chico was afraid of the hard floor having never encountered it before. The good news is that sometimes they eventually figure it out on their own and simply adapt. But what if they don’t?
How Can I Help My Chihuahua To Walk on Hard Surfaces
There are two things you can do. You can either put runners all through your house from room to room or you can help him get over his fear. It’s really up to you. Of course, helping them to get over it takes more time and effort.
Counter Conditioning:
Start with your dog on stable ground with you standing or sitting on the hard floor just a few feet away from him. Call him to you while you have a treat in your hand (be sure he knows you have a treat). When he moves forward enough that he has his front paws on the hard floor give him a treat. Keep moving back a little at a time and give him a treat each time he moves forward toward you. If he moves back to the carpet, do not give him a treat. Continue moving back a little at a time. If he stays on the hard floor without backing up, treat him for staying on the floor. Continue backing a little at a time until he is walking on the floor.
I found the following video very helpful for helping Chico to gain confidence and get over his fear of hard floors and I think you will too.