Should I upgrade to steel belts?

I bought my XL last year, and it came with fiberglass belts (no issues with them, and they’ve been calibrated.). I recently purchased the maintenance kit from Carbide3d, which contains steel belts.

Today I purchased a Z Plus. When I have the machine apart for the upgrade, should I replace the X/Y belts with steel? Or just the X since that belt needs to be removed anyways? Or should I just keep using the fiberglass belts until one fails?

Opinions please and thank you!

There’s a thread where some good measurements of the various belt tension moduli were taken;

The simple output of that is that, for you, assuming they were fibreglass not the polyester belts the steel cored belts are approximately 70-75% as stretchy for the same force.

If you’re going to be retensioning your belts, I’d recommend measuring the belt tensions as you do it, recording them so you can check them for changes later and balancing your Y axis belt tensions to get square movement;


I guess I don’t know what came with the machine. I assumed Fiberglass and not Polyester. Definately no metal in them because a magnet won’t stick like it does to the steel belts. I bought the machine in September, 2019. Same question either way - leave them or swap them for steel?

I, personally, would swap them out and run the newer Carbide standard belt, but that’s just me and I’ve swapped belts a few times now. Unless your old belts have an issue tthere’s not a big difference. You could keep the new ones as spares, they shouldn’t be worn out yet. It’s unlikely that you’ll spot the difference without some detailed measuring.

I’d suggest don’t over-tension them, but do balance up the two Y belts whether you swap them out or not.

There is a handy hint somewhere on this forum (I think it was mikep) which said if you blue taped the end of your new belt to the end of the old belt before removing it you could very easily thread the new belt through the pulleys and steppers just by pulling it through.


I’m cheap — I still have fiberglass belts on my XL and won’t bother to change until need be. The steel core belts on my SO3 were much easier to tension though and work really well, so looking forward to the change, but just can’t bring myself to do it before need be.


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