[herr_oberst]

LeMans was originally for Sports Cars, not pure racing cars.. As the cars became increasingly sophisticated, rules makers made sure that some of that heritage continued, with the spare tire rule (and there is also a space for luggage, too. I'm not making that up - the 956 had that, too, and one year, when the Andretti's, Mario and Michael were scheduled to race together in the Kenwood sponsored 956, the rulesmakers decided that the "luggage space" didn't adhere to the regulation and they almost didn't get to race the car))

I'm not sure when those rules finally disappeared, but the 917 was definitely one of those that had 'em.