Is spinning at the gym bad for sciatica calf problems?

Possible: Spinning is high energy. It can cause sciatica by lower back issue or pressing of the piriformis tendon on the sciatic nerve.

as usual, it depends: If spinning doesn't worsen your made, you can continue with it.

Hard to Say: Spinning places you on a stationary bike in a flexed position for your spine. That can be irritating if the sciatica is due to a herniated disc since that can cause it to push more on the nerves. So only way to know if try it out or get more advice from your doctor or a spine specialist that can discuss your case in particular.