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.
We have an old P reg Toyota Lucida. We're looking for a next stage car seat for our 11 month old but as the buckle stalks are long we're having problems. Our britax king plus (?) doesn't fit and we're limited to which seats we can use to position the seat in.
Please could you help? Many thanks!
As there are so few seats that are suitable with buckle crunch, we recommend that you visit a retailer who gives good advice and will be willing to try seats in your car. You may want to visit a couple of retailers, including your local independent store as you may find that gives you a wider range of choice.
At 11 months your son does not have to go forward facing either, there are also seats available at the next stage which are rear facing, and the seat belt routing of these seats may also give you more choice – it’s also safer for your little one
If you have any further questions please do not hesitate to ask!
Hi, I'm a bit confused about buckle crunch!
Is it bad if any of the plasic part touched the seat? or if it is just bad being wrapped over part of the seat?
Buckle crunch occurs if any part of the plastic buckle is pressured against the plastic shell of the child seat - it should only be your seat belt webbing holding your child seat in place. The buckle should not be touching the plastic frame of the child seat.
Hello, I'm so glad I've com across your website. We're finding it a nightmare trying to find a seat that would work in our van. The buckle part of the seat belt is approx 15-20cm long from the seat, also nothing to fit isofix to and narrow seats (Helllppp!) our baby is nearly out of her maxi cosi so we're looking for a seat that isn't going to cause buckle crunch. The Halfords fitter told me that nothing would work but surely there must be something? I think the britax plus was slightly too wide which is a shame because I was after a combination seat that would go rear facing for a while and recline for longer journeys. Would the kiddy seats work?
Thank you for posting your question,
I'm so sorry to hear of your troubles finding a suitable seat! They are indeed long buckle stalks that you have, and you will struggle to find a seat that will fit. It is difficult to recommend a seat that will be suitable without seeing your van, but if you can e-mail us the following details to firstname.lastname@example.org our car seat expert will be happy to recommend some seats that may be suitable:
- your child's weight
- your child's height (the amount of space from the top of her head, to the top of the Maxi Cosi)
- The make, model and year of your van
- The details of any other cars you may fit the seat into
The Good Egg Team
Hi, we went to Halfords today to purchase two car seats. One with an insofix and one without. We couldnt find a belt fastened one to fit a ford cmax 2006 car due to buckle crunch. Im looking for rear facing group 1? My baby is currently 9 months and about 20lb. he can stay in his Jane Matrix for now but would appreciate if you could point me in the directions of some that would fit my car with long seat belt buckles.
Thank you for your comment, and we are sorry to hear of the trouble you have had finding a car seat.
Does your cmax have floor storage compartments in the passenger foot well? Also, how much space does your baby have between the top of their head and the top of their infant seat?
The Good Egg Team
My son has a maxi cosi rodifix. It is restrained by isofix but he is restrained by a seat belt. It doesn't apply to our car as our buckles are within the seat but is it something I should be wary of in other cars?
Thank you for your comment!
Buckle crunch does not occur with high back boosters, so your Maxi Cosi Rodifix will not experience it.
The Good Egg Team
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