We have a car seat system which comprises a base and a car seat. My wife, my mother-in-law and me share two car seat bases. So sometimes we might have to move the base between cars.

  • One car has latch points so that is basically the easiest to install.
  • The in-law's car has just a lap belt in the middle back seat and in my opinion is the next easiest to install.
  • Our third car has shoulder/lap belts in the back and is the hardest to install correctly in my opinion.

I can install the base tightly and securely for the first two cars. However, I can never really get it super tight with the shoulder/lap belt.

My question is...generally how tight should the car seat base be? In the installation videos, the person demonstrating just hand tightens it. However when I brought it to my local Police Dept when I installed the base for the first time, they basically used their whole body to tighten it. The officer was pulling on the belt with his hands and using his foot (and knee at times) to push base snuggly against the car.

In my mind, the tighter the better so that in case of a crash, the infant car seat has less room to move around. I can't seem to find any definitive answer online. You can't measure the tightness of the straps that are cinching the car seat base against the car.

I know that this is probably a question for the manufacturer, but I thought that I get people's educated opinion.

  • You may be able to buy the brackets to retrofit into the other cars. Usually quick to install and pretty cheap.
    – GdD
    Sep 12, 2012 at 9:30
  • 1
    "generally how tight should the car seat base be" = as tight as possible. I'm sure it varies from locale to locale, but when we had car seats, you could take them to any firestation and they'd come out and show you how to have it properly installed (as a bonus, if people came with inadequate seats, they would actually give them a new one...which was great for those that couldn't afford new ones)
    – DA01
    Sep 12, 2012 at 18:32
  • One thing to keep in mind is to periodically check the snugness of the fit. I found that over time, the seat cushion stays compressed and doesn't offer as much resistance. So, I've had to push again with my foot as I tighten the straps.
    – milesmeow
    Nov 5, 2012 at 1:16
  • Some areas have 'car seat experts' which will come to your house and check your installation. This is usually a non-profit, you can ask your local hospital for contacts. Some places also offer this service at a local police or fire station.
    – Ida
    Dec 4, 2015 at 19:15

6 Answers 6


The thing a lot of people don't know about shoulder belts is if you pull them all the way out as far as they will go, the latching system will stay engaged and will only tighten, not loosen, until it is all the way retracted again. This mode was designed specifically for car seats and children in booster seats. Children's small size makes it take longer for the automatic latch to engage in a crash. That leaves enough slack in the belt to cause concern.

The proper way to install a car seat is to put all your weight on it, tighten the lap part as tight as you can, then pull the shoulder belt all the way out and let it ratchet down until it's snug. Most owner's manuals will tell you this, and may have other instructions specific to your model. Read it. I've also heard the same advice from hospitals, police demonstrations, and our foster parenting class.

  • 2
    I put my knees on the base with all of my weight then tighten the belt. When done the base feels like it is a solid part of the car. In my Honda Element the back seats recline making it really easy to recline the seat, install the base, then bring the seat back up locking it in place. Sep 16, 2012 at 15:03
  • 1
    +1 for the, "feels like it is a solid part of the car". Any amount you can move the seat, yourself, will be greatly amplified in an accident. You do not want the seat to move under your own power. Feb 24, 2015 at 0:26

A good rule of thumb is that if you pull on the car seat, if it moves more than 1 inch from front to back, or side to side, it is not tight enough.

Not having the seat installed properly is a very common problem, that frequently goes unnoticed until there is an accident.

There are many locations in the US, and possibly other countries, that offer free car seat installation inspections. It is well worth it to take your seat to one if possible at least once, to make sure you are properly securing the seat.


I am pretty sure that somewhere in the instructions for one of our car seats it says that when the car seat is installed properly there should be no more than 1/2 inch of side-to-side movement when you push/pull on the car seat firmly. If there is anyone in the house who is going to install a car seat, it's me so anytime we have to remove a car seat (usually for cleaning) I'm the one who re-installs it. I use my whole body to install them correctly. I put my knee in the seat/base to push it down into the car with the full weight of my body, and tighten the belt by pulling with both hands. Our car seats don't move when we pull/push on them.
We used to install an infant base with the lap/shoulder strap combo, and Karl Bielefeldt is right, if you pull the shoulder strap out all the way it should catch. You will then have to practically push the seatbelt back into the slot in order to tighten it enough but it can be done. Installing infant bases is the worst because you also have to make sure that it is installed at the right angle as well.

  • +1 for the knee option. We'd have to do the same in our old Subaru. Basically, I'd climb on top of the seat. If the angle is off, a few (not many--just a few) towels strategically placed underneath can help.
    – DA01
    Sep 12, 2012 at 18:33
  • Towels work, but pool noodles cut to fit work even better. They don't compress over time the way that towels do.
    – Meg Coates
    Sep 13, 2012 at 12:56
  • You don't have to pull all of the seatbelt through the feeder. Pull just enough through to latch it, and keep the excess on the original side when you pull it out to activate the locking mechanism.
    – Shauna
    Sep 20, 2012 at 18:30
  • WHen using the latch system, it is A LOT easier to tighten the child seat. When using the car's seat belt, it is always a struggle to pull on the belt and then to lock it so that slack won't be reintroduced. I've tried in on a few cars and I always dread using the car's seatbelt.
    – milesmeow
    Mar 4, 2015 at 6:38

In the instructions I read, you should use your body weight to buckle it in, and also twist the female part beforehand to shorten it if it's not tight enough. Of course the belt has to be locked, either by a mechanism in the belt, or with a locking clip. That said though, I could never get it to be as tight as with the middle lap belt either, so that's where we put it...


I notice a lot of parents with improperly installed loose bases that move around during normal driving. I've even seen parents use the seat belt on the car seat while also using the base because their base is so loose, which is safer but unnecessary. The bases were created for the parents' convenience in taking the child in and out of the car while enabling them to remain in the carrier.

I never took the base of my daughter's car seat out of my car. When we traveled in another car, I used the seat belt to strap in the carrier itself using the seat belt slits as directed in the instructions that came with the seat. I've never seen an infant seat without the those slits.

It takes a lot of work to get those bases in properly - tight enough that the seat doesn't move with normal pressure; they really weren't meant to be transferred from car to car. The car seats themselves were created to work without the base and most often are safer than the set-ups I see many parents use.


Perhaps American cars are different, but my experiences with European cars and European car-seats is quite simple.

I put the car-seat in place, then pull the strap over and push it into the buckle. Then I pull hard on the upper part of the belt (just using both hands) and clip that into the top of the car-seat (depends on car-seat model). This is enough to prevent the seat from moving more than ½ inch in any direction.

Of course if the car has ISOFIX/LATCH mounts then it's easiest and best - as you say.

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