halacha - bicycle on Shabbat?

Is riding a bicycle on Shabbat permitted within an eiruv, being ridden only on pavement (so no unintended plowing), for transportation and not exercise, and with the understanding that repairs aren't possible (so you'd have to get off and walk it)?

Answer

There are several issues that poskim have with a bicycle on Shabbat:

• Carrying/transferring in a public domain. (The bike is not considered part of the rider.)


• The bicycle may break, causing the rider to perhaps forget himself and fix it.


• Riding a bike is uvdin d'chol (weekday activity), and not appropriate on Shabbat.


• One might ride over soft soil, thereby transgressing the biblical prohibition against plowing. (Though the transgression in this case, I think would be Rabbinic.)


• A bicycle is muktza, as its primary use is for riding in public domains, which is generally hotza'ah (carrying), thus it is a kli shem'lachto l'issur (utensil that is designed primarily for a prohibited use).


• Even in a walled city, or one with an acceptable eruv, one may inadvertently ride outside of the eruv, or even outside of the t'chum shabbat.

For one or more of these reasons, many contemporary poskim prohibit riding a bicycle on Shabbat, though there have been those that have permitted it. As Joshua Lee linked in the comments, see here for a short discussion.

You implied in your question that perhaps riding a bike would be permitted with the understanding of the reason behind it being potentially prohibited, such as with the understanding that one may not ride over soft soil, or with the understanding that repairs may not be done. In general, the knowledge behind the reasoning of a rabbinic prohibition does not entitle one to transgress it. For example, the Sages felt it was necessary to forbid dancing on Shabbat, lest one come to bring musical accompaniment and further come to fix the instrument(s) if they break. This holds even if one understands that it is forbidden to fix instruments on Shabbat. We are still worried he may come to transgress a biblical prohibition.