Traveling by Renfe

You must manage your luggage yourselves. 55 lb. is a lot of weight. It's unlikely you'd hit that weight unless you had something like a 29" suitcase or were traveling with a lot of books or rocks (don't ask how I know). Since no one else is going to touch your bags, no one will know whether, in aggregate, two smaller bags add up to over 55 lb.

However, re-read what I said about handling the bags yourselves. Train carriage design varies; in many cases you must go up narrow, shallow steps to get on the train. Doing that while burdened with a large or heavy bag isn't easy. (It's really hard for short people like me.) If your bag is both large and heavy, you will soon rue how much you packed. Then, once you wrestle all your worldly possessions onto the train, you have to find a place to put your bags. Large bags probably won't fit overhead, and there's limited space on the luggage racks. Moderate-sized bags (up to 24" or so) can often be placed between the seats positioned back-to-back, but larger bags probably won't fit there.

Reading between the lines of your post, I'm thinking you're not yet on the packing-light bandwagon. I think by the time you get on your first train, you will be. You do not need to pack clothes for the entire trip. Plan to do laundry and take enough clothes for about 4 days. Don't take a full bottle of shampoo or a humongous bar of soap; buy travel-size toiletries. Check out the packing forum here for all kinds of great tips: https://community.ricksteves.com/travel-forum/packing

You handle your own bags, so make sure you can lift them yourself and do limit yourselves to one bag each. There are racks over the seats for them, and sometimes racks at the end of the train. Can you lift your bag over your head? If not, it is too heavy and you brought too much.

Thank you! I appreciate this good advice.

While they may talk about a bag limit, I have never seen it enforced simply because there is no way to enforce it. You carry or find a cart for your luggage from the front door to the platform. You are responsible for getting all of your luggage on and off train in a quick time. There is no checking of luggage similar to an airline. Three bags totally 55 lbs is an enormous amount of luggage unless it is a family of six.

Keep in mind that 55 lbs is a lot and if anyone has that much, they will likely have a problems just getting on the flight to get to Europe. Many of the U.S. airlines charge extra if your checked bag exceeds 50 lbs. European airlines generally have even lower limits.

People who can't handle their own luggage become the goats of the train system. They block aisles and doorways and generally inconvenience the other riders. Don't let this become your family! I don't think you need to plan for "just in case." Weigh your bags at home, have people show they can manage themselves, and make them reduce any luggage they can't handle.

Everyone will be so much happier if they have luggage they can handle!

If the anticipated weight is primarily due to clothes, keep in mind that it can be difficult to find what you want in a suitcase packed full of clothes. For that reason, I nearly always unpack at every stop. It's an annoyance to do that (and to re-pack) even though I travel with a maximum of 4 pairs of slacks and 5 tops. Not to mention that the average number of coat hangers supplied in a budget-level single hotel room is about three.

Regardless of your travel mode you will become Luggage Mules by overpacking.
EVERYTHING you need is already in Europe so pack super light and enjoy a better journey.
Do some shopping for clothes while in Europe as they make for great souvenirs and memories. We prefer to find consignment shoppes to locate excellent buys and make for a good diversion during the journey.

Super! Thanks for all the tips