Bicycle Mechanics - bike in the trunk

Can leaving your bike in the trunk of your car, for extended periods of time, be bad for it? I ask this because the car can get pretty hot when the sun is beating down on it as well as the possibility of more exposure to moisture and such. My concern is if it will cause damage to any parts of the bike and such. Maybe I should have put this in general forum, but wasnt sure if people who work on bikes would have a better understanding.

The only thing I would worry about would be the tires and the brake pads, if you leave them in the sun all the time they might dry out and become brittle, but I think you would have to leave them in the sun for an extremely long time for that to happen. Other than that I don't think you have anything to worry about, just cover it up with a white cloth to keep it out of direct sunlight.

Keeping your bike as junk in the trunk won't hurt it. Only possible downside is your tires exploding because of the increase in heat.

I guess it isnt that hard to put the bike in the house and avoid exploding brittle tires. :)

I guess it isnt that hard to put the bike in the house and avoid exploding brittle tires. :)

If that is really a potential, then I think I should warn you... take the car's spare tire out and put it in the house too. :D

Admittedly a car tire is thicker, and the compound is probably slightly different, but I wouldn't think the trunk would be significantly harder on a bike tire than on a car tire... And people always leave our spare tires in the trunk, and have since before any of us were born. As with a spare tire, be sure to replace the tire every few years... My guess is that aging may accelerate but it won't be days, weeks or months, it will probably be years before it ages to an unsafe point... and I urge you to put enough miles on your bike to wear them out before then.

Of course this is strictly hypothesis, and I am willing to retract if anyone has evidence otherwise.

The only problem I see with storing a bike in the trunk is wear and tear pulling it in and out.

A fellow I work with has an older Univega he tosses in the trunk routinely. He's always scratching the paint, banging the derailluers out of adjustment, tearing bar tape.... stuff like that. It was a nice looking, well running bike when I sold it to him - looks and runs like a beater now.

But maybe it's just him.....

Is there any possibility of lubricants thinning out in the heat and draining out of bearings? I once had this happen to a camera tripod I left in my trunk one particularly hot summer. After leaving it untouched for a couple of months I noticed a little pool of oil had formed under the ball head. I know the wheel bearing grease I use (Lubrimatic) is rated for something like 400F, but I'm not sure about other brands.

It's not nearly as hot in the trunk of a parked car as in the passenger compartment. The passenger compartment is like a greenhouse.

Just ride the bike so it has no reason to be in the trunk. That said I think if you want to maintain the best looking bike hang it on the wall and polish it nightly. My bikes look like crap after riding them all day.

I guess I should probably have explained it better. I have to put the back seat down to get the bike in the back, so it is exposed to the main compartment, which is hotter than a normal trunk.

I guess I should probably have explained it better. I have to put the back seat down to get the bike in the back, so it is exposed to the main compartment, which is hotter than a normal trunk.

Even so... as I recall, you live somewhere in PA (Covered Bridges ride info)... I don't think that even if you have special coating on your windows to ensure the hottest possible car interior, your car would get as hot as a trunk in Florida, and yet, they keep their spare tires in the trunk... :D

But, you are the one who has to ride it and trust it... so it is your call.

My larger concern would be UV, and even that is less than if it were outside, since glass blocks some UV.

I guess its not so bad then. ofcourse, I always take it out when I visit my grandmother in philadelphia, otherwise I would have a smashed window and no bike.

I guess its not so bad then. ofcourse, I always take it out when I visit my grandmother in philadelphia, otherwise I would have a smashed window and no bike.

I hear ya brother. I empty the car of everything and kiss the car goodbye whenever we go to Philly to visit relatives. The idea being that if it is still there in the morning it is a great surprise and joy. If not, it is how I expected it to be.

Your car tire gets hotter when you drive than when sitting in the spare tire well.

one thing to be aware of is that hydraulic fluid can expand, jamming the brake on. I've had this happen with one of the awful, and old, wendler hydraulic brakes. It was an amusing and educational incident. I doubt the bike was at any risk though.

- Joel