When child seats are fitted with the adult seat belt, it must be the webbing of the seat belt holding the seat in place, not the seat belt buckle. If any part of the plastic seat belt buckle casing is on or over the plastic frame of the seat, it is an unsafe fit, which is called buckle crunch.
Buckle crunch typically happens in vehicle's that have the female buckle on a long stalk, causing it to protrude out of the vehicle seat.
However, buckle crunch can happen on buckles with a shorter stalk, if the wrong car seat is used.
Buckle crunch is dangerous, because the plastic casing of the seat belt buckle is bent on or over the plastic of the child seat. This puts pressure on the casing, and in a collision, the casing could shatter - causing the car seat to not be safely restrained.
The seat on the left is the Maxi Cosi Tobi, which is a forward facing group 1 seat that often avoids buckle crunch. The seat on the right is the Axkid Minikid, which is a rear facing group 1,2 car seat that also often avoids buckle crunch.
If your vehicle has ISOFIX, it is useful to use it, as this removes the need for the adult seat belt. It is important to visit a retailer to buy an ISOFIX seat, as not all ISOFIX seats fit all cars. ISOFIX child restraints are normally classed as 'Semi Universal', and have a vehicle compatibility list.
If you have checked your child’s car seat and found it has buckle crunch (example above), try fitting it in a different seating position in the car. Occasionally the seat belt buckle length differs, and moving the seat to a different position solves the problem.
You can also check your model of child seat, on some seats there may be several ways to secure it, with one of those methods avoiding buckle crunch.
As an example, the Britax First Class has an alternative buckle routing:
No, only seats which use harness to restrain the child, and occasionally an impact shield, can have buckle crunch. It is dangerous because the seat belt is holding the child seat in place, and the child seat is restraining the child with a harness. In a collision, this puts a lot of pressure and force on the child seat, seat belt and buckle.
High back boosters and booster cushions do not get buckle crunch, because the booster is simply a 'belt positioning' device, which lifts the child up so the adult belt can fit them safely.
It is not dangerous for the buckle to sit over the frame of a high back booster - although you do need to make sure the buckle doesn't sit under and behind the frame of the seat, as this gives an unnatural belt route.
Hi, my little one is 10 months old and weighs 9.5kg and is about to grow out of his current car seat. We have just changed our car to a Vauxhall Zarifa (2002) and went to Halfords today to look for a new seat. But after trying a few out we couldn't get one to fit because of the long buckle stems. Ideally we are looking for a 123 seat but would consider any other options.
Thanks for your enquiry.
It may be difficult to find a seat which will fit. I can suggest the Britax Evolva, which may have to be used in full recline - it is worth getting it checked in store though as the Zafira's have very long buckle stalks and the Evolva may still buckle crunch.
Another group 123 car seat to consider is an impact shield seat. These use a shield instead of a harness to secure your child, and they can be very good at avoiding buckle crunch.
You may also want to consider a group 1 car seat, as the Britax First Class and Maxi Cosi Tobi can both be very good at avoiding buckle crunch.
Lastly, group 0+ infant seats are suitable until your baby is 13kg, or until the top of his head is level with the top of the seat - please don't worry if his feet are hanging over the edge, they are in no danger. Your little one is safer rear facing, so if the top of his head is still within the top of the seat, you have a little longer left.
Hi, my daughter is 19mths old and currently using a maxi visit acids in our Vauxhall meriver 04. I had a friend in the car yesterday who works in John Lewis with car seats and she said the car seat had buckle crunch and wasn't right. Can these be fitted in this car? I had it originally fitted in halfords but that was a 4 years ago when my eldest was small. Same car and same seat tho.
Thinking of trying it in the middle to see if it changes. Starting to panic now.
Thanks for your comment.
Your friend is quite right, the Maxi Cosi Axiss is very likely to buckle crunch in the Vauxhall Meriva. It would be worth trying the seat on both sides of the car, as sometimes the buckle length can differ. You could try the seat in the middle too, however middle seating positions are often unsuitable for child seats.
If you find that you need a new seat, please don't hesitate to contact our experts on email@example.com, and they will be happy to suggest some seats to you.
The Good Egg Team
Hi, I wonder if you've any suggestions. We currently have a Joie iAnchor but are experiencing some problems so I returned to Mothercare today to try out some alternatives. I only oaid £145 and can't spare a great deal for a replacement so I was looking at a belt in options as they are generally cheaper than isofix. An advisor installed the Joie Steadi in erf mode and said it was unsafe due to buckle crunch. I asked to try the others but was told the problem would be the same. All other belted erf seats were only suitable to 13kg which my son almost weighs now so they aren't an option. Mothercare recommended the Cybex seat but at £400 it's just not an option. We also need a seat that can be belted as it will occasionally be installed in Granny's car which doesn't have isofix. I have a Suzuki Splash and the Joie website says the Steadi, Stages and Every Stage are all compatible so I'd thought providing they fit securely we'd be sorted but now this! I have 25 mum friends and none of them have ever heard of buckle crunch! It seems impossible to find a car seat that is actually safe!
Thank you for your comment.
The Joie Stages and Everystage are typically very good at avoiding buckle crunch when in rear facing mode - however, they are likely to buckle crunch when turned forward facing with the harness in your car.
If you would like any other seats recommended, please contact our experts directly on firstname.lastname@example.org
The Good Egg Team
Hi. I am looking into buying a Nissan Qashqai+2 do you know if the Maxi Cosi Mobi is compatible? Thank you
Thank you for your enquiry.
Extended rear facing car seats are largely approved as semi universal, and will have a vehicle compatibility list, which can be found on Maxi Cosi's website. This is where you can find the information as to what cars your Maxi Cosi Mobi will safely fit into
The Good Egg Team
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