I work near the weekday departure point of an area bike club. Is there an issue with leaving my bicycle in my car inside of a secure parking lot for the entire day?
Theft is not a concern I am wondering about the heat of being in a closed vehicle under the sun?
Thanks in advance, Colin
About the only thing I’d worry about is tire blowouts if it was a really hot day. If you let some air out of the tires you should be fine.
The smell.
I’ve been doing this sort of thing for a couple summers now and have never had a problem with it.
As long as the bike is in the trunk and not exposed to direct sunlight, the heat issue shouldn’t present a problem.
I do this all the time. I crack the windows a bit and put a towel over the bike. Otherwise I’ve had no problem with leaving it in the back seat in the hot AZ summers
I’ll repeat what’s already been mentioned - roll down a window a bit, let a bit of air out of the tires and throw a sheet over the bike.
Tire blowouts shouldn’t be a problem. According to Zipp it takes a 10 degree (F) increase in rim temp to increase pressure 1lb. That means that your rims need to get into the 300 degree+ range to be anywhere close to causing problems. This can happen if you’re braking a lot on a long descent but its pretty unlikely to be a problem inside your car.
I let air out of my tires when I leave them in a parked car too but only out of an abundance of caution. If I didn’t have a pump in the car, I wouldn’t think twice about leaving tires pumped up to 125 in the car even if it was going to be hot.
You’re sure to get complaints from the SPCB (Society to Prevent Cruelty to Bicycles), maybe even get arrested.
Freek! 
Makes sense, but all I know is once I left my wheels in my trunk and when I got them the next day one was flat. Probably a small thorn or something I wasn’t able to find, but I’ve been paraniod ever since.
I’d definitely drop the pressure a bit if you’re running near max pressure and intend to leave the bike in the car on a hot day. This assumes that you inflated the tire to pressure under cooler temps prior. I’ve had mountain bike latex tubes blow up in both tents and the car under high heat. I think the Zipp comment is intended to alleviate the concern that the carbon wheels do not dissipate heat as well as aluminum rims during braking. The fact is that extended time in the car will equalize the air temp between car interior and tire. If you inflated your tires under 70 degree temps, and left in in the car of a hot day, you could see a rise to 120+ degrees. That would obviously make a significant jump in tire pressure.