I may be alone in this, but I noticed my spare was manufactured in 2012. Most sources recommend replacing them at 10 years. The current size is 165/70/17. I really liked that tire size as it was less than 1% smaller in diameter than the 235/45/18 oem tire. I couldn't readily find a new (or nearly new) tire in that size, so I opted for 155/80/17. This tire is available new from Goodyear at about $130 or Falken for about $90. It is nearly 2% larger in diameter than the original OEM, but I decided I could live with that. BTW, I opted for the Goodyear as it had a little higher load rating and I liked the tread pattern more, but the Falken would seem to be an acceptable option as well.
I don’t carry a spare in the Clarity. This does inspire me to look at the full size spare on the pickup truck, which I suspect is 24 years old. One recommendation with a different size spare is to avoid positioning it on the drive axle. In your case, a 2% difference may be considered insignificant. Otherwise, in the event of a front tire failure on a front wheel drive vehicle, the procedure would be to replace the failed front tire with a tire from the rear axle and then, position the spare on the rear axle. My observations suggest that this practice is rarely followed and that any speed restrictions are ignored as well. Does the load rating of the Goodyear meet or exceed that of the OEM tire?
Yes, the Goodyear has a load rating of 101, the Falken at 100. Both of these assume that the spare is inflated to 60 psi. Lowering the pressure would lower the load rating (probably pretty fast). The Michelin Energy Saver A/S 235/45/18 is rated at 94. You are right. Most references on the internet about this recommend that the maximum difference is 1%. This seems to be coming from BMW guidance and may be mostly pointed to potential damage to limited slip differentials. Not sure the same restrictions would apply to the Honda, and I may run the 1.8% difference in this spare for a short period if it isn't convenient to change two tires (assuming the flat is on the front).
I have yet to see a load and inflation table from a tire manufacturer, for a temporary spare that provides anything other than one specific pressure and one specific load capacity. That would indicate that the manufacturer makes no claims about load capacity at a lower or higher pressure. The OEM Michelin tire has a load capacity of 1477lbs at 36psi. Michelin specifically states that inflating the tire to a pressure higher than 36psi, does not increase the load capacity, even though the Max Cold pressure on the sidewall is 44psi.
Again, you are right. I was just trying to make the point that for temporary spares that the 60psi is "really" needed to support the weight limit of the tire. Running them at much less than 60psi for very long would tend to damage the tire, especially for a heavy car like the Clarity.
