Dhr01

New Bike

I am considering buying a new Trek bicycle with hydraulic disc brakes (Shimano 105 group set). To transport my bike, I take the
wheels off and put everything in the car trunk.I was told that when the wheels with the brake rotors are off the bike and if the brake
control levers are depressed, the hydraulic pistons will expand and prevent the wheels from being reinstalled. The brakes will need
to be bled to reinstall the wheels.

Is this correct?

Troul 

That is correct to assume.

wolfchild

You can buy special inserts which you can put inside your brake caliper to prevent this problem... Some bikes with hydraulic brakes even come with them.

Mojo31

Or, you can fold a business card in half, and stick them in between the pads.

Elvo

Or, you can put an insert prevents the brake levers from actuating

Troul 

A folded over cereal box flap with a bread tie works. That bread tie is essential if the bicycle is roof mounted without the front wheel installed.

Koyote

No. All you have to do is insert a plastic tire lever in between the pads and push them back into place. Alternatively, just don’t pull on the bloody brake levers while the wheels are off the bike. Or use the plastic inserts that any shop will give you for free.

Troul 

if there's enough of a gap to pry both sides open & each piston is equally extended out.

WhyFi

Someone's trying to scare you.

As mentioned by others, Shimano has orange spacers that you can stick between the pads. Shimano also has yellow lever lock thingies that slide in under the levers and keeps both the brakes and the shifters from being actuated. I take long road trips regularly and I use both, though I could probably get away with just the lever block thingies.

I took a screen shot of a video with the lever block - they came with my levers when I built up my bike and I would expect that the shop that you buy from would have a box of 'em laying around if you ask.

WhyFi

No, it's not.

vespasianus

As people have said, you can use the travel block that any shop can give you. Most shops will give you them for free. I have 5-6 in my car and another 10+ in my garage.

Also, all you may need to do is push the pads back, no bleed needed.

Koyote

That's not really an issue.

Do you have any experience with this problem?

Chuck M 

This has always worked for me. Even putting a 56cm frame and both wheels in the confines of a Honda Civic in the dark I have yet to inadvertently bump one of the levers. Additionally when I do need to trunk my bikes instead of using a rack, I prefer it to be my disc brake bike over one of them that I have to wrest a tire through rim brakes.

Troul 

Yes. Not all pistons travel the same distance & can pose a problem when trying to pushing it back into its bore.

WhyFi

I can't say that I've ever seen a piston that didn't back off enough to slide in a thin blade when the lever was released. Or, if nothing else, you could just remove one screw and remove the pads to give yourself plenty of room between the pistons.

Troul 

given how many economical quick solutions there are for preventing an issue, their is no reason for disregarding taking the precautions in preventing problems.

WhyFi

Sure, but there's also no reason for boogieman scare tactics and letting someone believe that they may need a bleed job because their lever got depressed. It's silly.

biker128pedal

I use the orange spacers which I had to ask for but did not know to ask for the lever locks. New to me. I think the sops are hoarding them to sell on eBay.

Troul 

IMO; It's a scare tactic if the operator doesn't know what to feel for during the use of the brakes.

WhyFi

I honestly have no idea of what you're trying to say.

Koyote

I think that makes two of you.

Troul 

dont be scared.

Troul 

It's not any tactic, it's an awareness of what the risk is if the brake pistons are overly extended.

WhyFi

A) you're moving goalposts. We were talking about the scenario of pads being squeezed so tightly that nothing short of a bleed job could rectify the situation, which is just implausible
B) pistons aren't going to be overly extended unless the pads are removed

I think it's fair to assume that there's no compelling reason to continue here, so I'll bow out.

Random11

I don't know whether this is correct, but when I bought my bike, it came with those orange inserts and the shop told me to put them in when I take off the wheels, so I do. It's easy to do and I've never had any problems. So if you're removing your wheels, just put the tabs in.