Cars get pretty damn hot, and plenty of cyclists are more than happy to leave bikes and gear locked up in sweltering temperatures. But cars can get extremely hot: according to HeatKils.org, when it’s only 21 degrees Celsius outside and sunny, a car can get up to 45 degrees within an hour. When it’s 37 degrees, a car can easily heat up to 77 degrees.

Kevin Haviland, head mechanic and team manager for Norco Factory Racing, has seen his share of hot car disasters. In fact, his best advice is that if it’s hot enough that you would hesitate to leave a child or a dog in the car for any amount of time, your bike probably shouldn’t be left in the heat, either.

Here are key items of your cycling gear that you shouldn’t leave cooking in your car on a hot day:

Already-Inflated Tyres

There’s a reason that Ironman races allow athletes to pump up their tyres on race morning: because overnight, heat can potentially swell an inflated tyre and cause it to explode. The same applies to any tyre that’s pumped up to its max PSI in your car, says Haviland.

Bikes with Hydraulic Gear

Really, any liquid that goes on or in a bike shouldn’t be out in temperatures above 43 degrees. Haviland points out that almost all chemicals on the bike – from the oil that keeps hydraulic brakes working to chain lubes to degreasers – all have temperatures listed on the containers, and most say to keep the liquids under 48 degrees. After that, their efficacy goes down, and in hydraulic brakes, fluid might even evaporate.

Chamois Cream

Because chamois cream is hard to use when it’s liquified…

Your Neon Bike Frame or Helmet

The problem with the now-trendy neon paint on a lot of bikes, Haviland says, is that it has the tendency to get ‘sunburned.’ Unless your bike is in the trunk or blocked from the sun, you risk fading your paint a lot faster by leaving it in your backseat.

Gummies, Gels, Bars

Any food that you don’t want to be melted into should probably be stored somewhere cool – especially gummy packs, like Chomps from Gu, which can easily melt into a single, massive gummy. But if you don’t mind the mess, you’re probably still safe eating your super-heated sports nutrition. If your bar includes perishable ingredients, it’s still probably best to mind where you leave it.

CO2 Cartridges

Similar to not bringing CO2 cartridges on a plane, leaving them in a hot car is equally potentially hazardous. Likely, you’ll be fine, but pro racer Sarah Kauffman says, “I had a CO2 canister explode in a hot car! It was in a backpack and the pack was blown to pieces!”

Your Gross Chamois & Wet Kit

If you’ve used a chamois cream, particularly a petroleum-based one, you really need to clean your shorts ASAP. Leaving them sitting in a hot car is like putting a petri dish of bacteria into a moist, hot environment. The smell alone should convince you, but if that’s not enough, think about the amount of times it’ll need to go through the rinse cycle to guarantee all the sweat, cream and bacteria are gone. Grossed out? Good. Incidentally, leaving wet workout clothes in your car is also the worst thing to do for your car’s interior: cyclist Iain Banks points out that a wet kit and wet shoes can stink up your car for weeks.

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