I guess that I wold first try to reason with them. I would point out that one reason I rented there in the first place was because bike parking was allowed. I would show them how lousy their idea of where you should park is. If other tenants are affected, I would organize some kind of group action.
If that didn't work, I would probably try some threats. I would tell them that when I signed my lease, it was with the understanding that there would be parking for my bikes. If there was no parking, I either would not have rented there, or I would have asked for a substantial reduction of the rent. Since they have arbitrarily reduced the value of my apartment by removing the parking for my vehicle, I would consider the lease to be null and void and I would feel free to move out without any penalty.
(You should probably check the law on this before you actually break the lease. I think the premise is that they actually broke the lease by reducing the value of your holding, without providing a replacement or even giving you reasonable notice.)