The Gemara in Bava Metzia 79b describes that a borrower who on-lends a donkey to a man and it's damaged, doesn't have to pay but if a woman rides the donkey he does bc they ride differently and shift their weight causing damage.
There is discussion whether this is because of the general rule that a lender trusts a specific borrower with his object and not another person (here paranthetically a woman, perhaps the spouse), whether this applies only to the borrower's spouse or only to other women beside the spouse. There is also discussion whether (1) one must pay damages if he on-lent it to a woman and (2) whether donkey rentals to women drivers were higher priced and the applicability of that in terms of paying if lent to women (see Rambam Schirus 4:5, copied below)
Rashi Nidah 014 d'lo Metartin explains - riding the donkey as women do, which sounds like that means with both legs dangling together from one side of the donkey in contrast to the 'scale-like' position with one leg dangling down each side of the donkey. [Pesachim 3b mentions women at nighttime riding donkeys standing, not sitting)
Is it possible that the concern of Bava Metzia 79B in lending the donkey to a women is that a women's different style of riding (both legs on one side) applies her weigh differently on the donkey thereby possibly causing damage to the donkey? Because if so, that would greatly impact the analysis and outcome of the above-discussed issues (which were predicated on principles general to borrowing) while the prohibition from lending a rented donkey to a woman may instead be predicated upon females' specific donkey riding style?
Daniel Gray, Toronto Canada
1) I have not seen that anyone suggests that the different way of riding would actually represent a damaging factor to the donkey.
However, I did see something in Bava Metzia that is relevant to d'Lo Metartin. At the beginning of Bava Metzia 9b, the Gemara states that if a woman rides on a donkey in town, this is an effective way of making a Kinyan. Rashi explains that a woman is not strong enough to lean on the animal because this would require holding it and it might break away from her. The Ya'avetz there cites Pesachim 3 that says that it is not dignified for a woman to ride. The Imrei Binyamin in Bava Kama cites the Gemara in Nidah 14a. One therefore may suggest that d'Lo Metartin does have a ramification in monetary Halachah: because it is a normal way of women riding, this is why Bava Metzia 9b states that there is a Kinyan for a woman on a horse in the city -- namely, when she is riding d'Lo Metartin, which is standard practice.
2) Reb Daniel, I cannot find anyone who says that he has to pay for the damage because women ride differently and shift their weight. The reason given that one may not sub-rent it to a woman is merely because she is heavier, not because of her different way of riding.
In addition, the Rashba maintains that it is only l'Chatchilah that one may not sub-rent it to a woman, but b'Di'eved if he did so he is not liable for damage, because the difference in weight between men and women is not sufficiently large for it to be considered "Peshi'ah" if one changed the conditions.
Kol Tuv,
Dovid Bloom