Lower Anchor Weight Limits: Background Info

There’s a fairly recent concern, driven by changes in car seat design and usage, that vehicle lower anchors may not be strong enough to hold heavier kids in heavier seats in some crashes. In a crash, the combined weight of the child AND car seat pulls on and stresses the lower anchors. When LATCH was first conceived, most car seats weighed well under 20 pounds and did not accommodate children heavier than 40 pounds. Today car seats are heavier, typically weighing 20 to 25 lbs, and typically accommodate much heavier children with some 5 point harnesses fitting kids up to 65 pounds. This combined higher weight, of both car seats and the children using the car seats, has driven the research and regulation changes explained below. 

How it affects you

How does this new concern regarding the strength of lower anchors affect using the car seat?

This concern resulted in a major amendment to the Federal Motor Vehicle Safety Standard 213, (FMVSS 213), which is the safety standard applicable to car seats and boosters in the US. This amendment introduced weight limits for lower anchors. 

Each car seat now has a maximum child weight limit allowed for installation using the lower anchors. After your child exceeds this weight, the car seat must be installed using the seat belt and not the lower anchors. 

Of course this isn’t as simple as it sounds because the limit depends not only on the car seat’s weight and your child’s weight but also on when the car seat was manufactured, so we’ve included the guide below to help you figure out if you can use lower anchors or if you must use the seat belt to install your car seat.

Lower Anchor Failures

Have there been any crashes where the lower anchors have failed?

There have been three failures in crash test labs, but none in real world crashes.

If a lower anchor were to break in a real world crash, it would most likely occur with a heavier child in a heavier car seat in a higher speed crash, because this scenario puts the most stress on the lower anchors. If the lower anchors do actually have a maximum weight that they can withstand, we will see this problem manifested in real world crashes only when there are more children using heavier car seats to higher weights. However, right now it’s purely conjecture that the lower anchors have a maximum weight that they can withstand… since they have never broken in a real world crash that we are aware of.

Failures in the Crash Test Lab

Failure #1: Transport Canada crash test facility using 2007 Nissan Versa

Weight: 10 year old dummy weighing 78 pounds + Britax Regent weighing 25 lbs =103 pounds total weight

Installation method: LATCH in center seat (misuse)

Misuse: The car seat was installed with LATCH in center seat, but the center is not a designated LATCH position

Notable: Tether strap slipped into vertical split between the seat backs, causing an abrupt shift of forces.

Injury: Child dummy remained in the car seat and injury measures were not serious.

Failure #2: Transport Canada crash test facility using a 2010 Kia Forte

Weight: 10 year old dummy weighing 78 pounds + Cosco Apex 65 weighing 13 pounds = 91 pounds total

Installation method: Car seat was installed with LATCH (lower anchors and tether) on the side. 

Misuse: Dummy exceeded the Apex 65’s weight limit. The Apex 65’s maximum weight limit is 65 pounds, but the dummy weighted 78 pounds.

Crash details: 35 mph frontal crash test. Peak acceleration was 46 G. Total maximum anchorage loads measured was 20,395 N.

Notable: During the test, the inboard anchor, which was held in place by two bolts, pulled through the sheet metal resulting in a failure at the attachment point.

Failure #3: NHTSA Vehicle Research and Test Center using Kia Forte buck and front loaded sled pulse. Two tests were performed in this instance.

Weight: 6 year old dummy weighing 66 pounds + Cosco Apex 65 weighing 13 pounds = 79 pounds total

First test:

Installation method: Installed with LATCH (lower anchors + top tether) on the side.

Load measurements: The total anchor loads (lower anchors+tether) was measured to be 17,330N and the total load on the lower anchors (inboard+outboard) was 11,666N

Notable: Some deformation of the sheet metal with some forward pull of the lower anchors but not a complete failure of the anchors.

Second test:

Installation method: Installed with just the lower anchors on the side (no top tether used–but note that this seat did not require use of the top tether)

Load measurements: The total measured force on the lower anchors in this test was 14,922 N. Note that this is 30 percent higher than the total lower anchor load in the first NHTSA test where the tether was attached.

Notable: Complete failure of the lower anchor hardware

Lower Anchor Weight Limit Guide

If you have a car seat made AFTER February 27, 2014:

Your car seat will state – both on a sticker on the car seat as well as in the instruction manual – the maximum child’s weight for using the lower anchors. If your seat goes rear-facing and forward-facing, be aware that the maximum child’s weight to use the lower anchors may be different for rear-facing and forward-facing.

Rear-facing: car seat manufacturers may allow the use of the lower anchors up to a combined weight of 65 pounds (child’s weight + car seat’s weight).

Forward-facing: car seat manufacturers may allow the use of the lower anchors up to a combined weight of 69 pounds (child’s weight + car seat’s weight).

Note: A car seat manufacturer can choose to be more conservative and set the lower anchor weight limit LOWER than the 65 or 69 pounds combined weight. For this reason it is critical to read the instructions to your child’s car seat.

If you have a car seat made BEFORE February 27, 2014

Here’s where it can get a little complicated.

First, read car seat’s instruction manual, which is typically available as a PDF on the manufacturer’s website. If you can’t locate the manual, call the car seat manufacturer and ask.

If the car seat’s lower anchor weight maximum is higher than you were expecting (or is higher than on the same seat made after Feb 27, 2014), please understand that the new limits are NOT retroactive. However, you many still take the more conservative route and follow the new limits, even on an older seat, as seat belts are a very safe and very effective way of securing a car seat to the vehicle, so long as you get a tight installation.

Also, check to see what your vehicle manufacturer has to say. Some will give a weight limit, others won’t. This table is the most up to date information from the vehicle manufacturers regarding their current lower anchor weight limits. The information in the table is taken from the LATCH Manual by SafeRideNews and in some instances the information in the LATCH manual is the ONLY published, vehicle manufacturer-approved source of the information.

Do the lower anchor weight limits also apply to boosters?

Short answer: NO.

To clarify, first lets define “booster:” a booster is a seat the child sits on and the child uses the vehicle’s seat belt across them. If the child is using a 5-point harness that comes from their car seat, then they are NOT using a booster, and are instead using a car seat.

This confuses many parents because there are lots of seats that start out as 5 point harness car seats and can then turn into boosters. These seats are sometimes marketed as all-in-one seats or harnessed boosters.

Some booster seats now come with lower anchors. There is NO WEIGHT LIMIT to the lower anchors for booster seats because the booster is not the restraint and does not take the force of a crash. This is different from a car seat with a 5 point harness where the car seat DOES take the force of the crash and pulls on the lower anchors.

My child exceeds the weight limit of the lower anchors. Do I have to buy a new seat?

No! So long as the child is still within the weight and height limits for the 5-point harness, you can continue to use the car seat but must install it using the vehicle’s seat belt instead of the lower anchors. You should continue to use the tether on every forward facing car seat as it significantly reduces the chance of brain and spinal cord injuries.

My child exceeds the weight limit of the lower anchors. Does this mean my child has to go into a booster now?

No! Your child can continue to use a seat with a 5 point harness so long as they are within the weight and height limits for the 5 point harness on that seat… just make sure you install the car seat using the vehicle’s seat belt (and the tether), not the lower anchors.

Can I use the lower anchors AND the vehicle’s seat belt?

No, unless the child’s car seat specifically allows this.* You do NOT want to do use both the seat belt and lower anchors because the car seat is not tested with this double installation method. Doing this turns your child into a guinea pig! If it turns out to not work well in a real crash your child will suffer the consequences. Trust the manufacturer that they know their seat better than you do – if they don’t specifically tell you to do something, don’t do it. Children shouldn’t be guinea pigs.

*Note that some manufacturers do permit and/or require this type of installation method. The Nuna Pipa and Clek Foonf when used forward-facing are currently the only car seats which permit this.


Do tether anchors have weight limits too?

Currently no car seat manufacturers  state a tether anchor weight limit. Some vehicle manufacturers are stating weight limits on their tether anchors though.

As Child Passenger Safety professionals, the idea of a tether anchor weight limit deeply troubles us because we try to base our recommendations on evidence, not on theories. Limiting the use of tethers exposes a child to proven risks in the hopes of preventing what remains only a theoretical risk (i.e., the tether breaking). Even if the worst case scenario should happen and the tether should fail in a crash, it’s likely to break towards the end of the crash, after it has helped manage a lot of the energy of the crash. In this situation the tether would likely still offer significant benefit to the child. A potential risk from the tether breaking in a crash is that the metal hook at the end of the tether strap could fly and hit the child; however, without the tether, the child stands a significantly increased risk of hitting his head on hard structures like the window, door frame, or the back of the front seat.

We’re not alone here. NHTSA (the federal government) also feels strongly that tethers should always be used. Here’s what NHTSA has to say:

“NHTSA has tentatively determined that consumers should be instructed to always attach the CRS tether when restraining a child in a forward-facing CRS with an internal harness. Further, we believe that the instruction is appropriate when the CRS is installed using the lower anchorages of a child restraint anchorage system(79) and when the CRS is installed using a seat belt. The instruction is simple and would increase the ease of use of tether anchorages. The agency requests comments on this issue.

If consumers were provided the simple and straightforward instruction to always attach the tether on the subject CRSs, we believe that tether use would increase, to the benefit of child passengers. In tests of a restrained dummy in forward-facing CRSs with harnesses, researchers found reduced head excursions due to tether use in frontal sled tests conducted at different speeds. (80) Field data indicate that the most common injury to children restrained in child restraints is a head injury, and the source of injury is often contact with vehicle structures in front of the child restraint, such as the vehicle front seat back. (81) We tentatively conclude that the use of tethers would reduce the magnitude of head excursions, and that reduced head excursions would result in fewer and less severe head injuries. (82)

Test data indicate that tether anchorages are extremely robust and would be reasonably able to withstand crash forces generated by virtually all restrained children in the subject CRSs. As explained below, NHTSA (a) estimated the dynamic loads that are imparted to tether anchorages in 47-56 km/h (30-35 mph) crashes; (83) (b) assessed the strength of current tether anchorages through quasi-static laboratory testing; and (c) analyzed those data to estimate the dynamic loads that current anchorages would be able to withstand. NHTSA has tentatively determined that the analysis shows that tether anchorages are sufficiently strong to warrant an instruction that they should be used with all children restrained in a forward-facing CRS with an internal harness.”

Note: Recaro was the only car seat manufacturer to specifically prohibit using the tether for heavier children. The Recaro ProSport initially did not allow the use of the tether when the child weighed more than 52 pounds. However, since the 2014 recall on the ProSport, Recaro changed their policy and ALWAYS wants the tether used on the ProSport, even including the ones that stated to stop using the tether after 52 pounds, when the child is using the 5-point harness, up to the full 90 pound capacity of the 5 point harness. For more information, see here.

What are the car seat manufacturers doing in light of the lower anchor weight limits?

Many car seat manufacturers are getting more innovative with the design of their seats to make installation easier for heavier kids. Many car seats are now optimized for a seat belt installation, making the LATCH weight limit irrelevant.

Easy-to-use seat built-in seat belt locking devices make a seat belt installation easier in many vehicles. These include:

  • Britax’s “ClickTight” technology 
  • Graco’s “SnugLock” device
  • Chicco’s seat belt lockoff device

Other manufacturers, like Clek, have approached the issue from a different direction. When using the Clek Foonf forward-facing, you can use the lower anchors to the full maximum of the seat (a child’s weight of 65 pounds) despite the fact that the car seat itself weighs 32 pounds. How is this possible? Clek did extensive testing to show that on their seat using the rigid lower anchors plus the vehicle’s seat belt plus the tether is very safe when the seat is used forward facing. The seat belt is the “back-up plan” so that should the lower anchors not be strong enough, the seat belt will hold. The Foonf’s crumple zone technology (REACT system) requires the use of the lower anchors so installing the seat with just the seat belt plus tether forward facing would mean missing out on this great feature of this seat.

What about the Sunshine Kids/Diono car seats with SuperLATCH?

It depends on whom you ask and when your seat was made. But first, an explanation of SuperLATCH. SuperLATCH is a stronger lower anchor connector – as it has 4 metal “teeth” instead of the typical single metal “tooth”. This picture here shows a regular lower anchor connector on the left and a SuperLATCH connector on the right. SuperLATCH has nothing to do with the lower anchor in the vehicle – it is simply a stronger means of connecting the car seat to the lower anchor in the vehicle.

If you believe that the lower anchors in the vehicle are strong enough to hold any weight of child + car seat, then you would side with Sunshine Kids / Diono on this issue and feel comfortable using their seats with the lower anchors + tether to the maximum weight allowed for the 5 point harness (65 or 80 pounds depending on which particular seat you have). If, however, you believe that the lower anchors in the vehicle may not be strong enough to hold any weight of child + car seat, then you would choose to ignore the issue of superLATCH and would stick to the 65 or 69 pound combined weight.

All Diono seats made after Feb 27, 2014, even those with superLATCH, must comply with the new government regulations. As such, the lower anchor weight limit is a child’s weight of 35 pounds for rear-facing and 40 pounds for forward-facing on the Diono Radian seats.

Note: superLATCH – namely Sunshine Kids/Diono’s permission to use the lower anchors beyond the vehicle’s stated lower anchor weight limit – ONLY applies to vehicles model year 2006 and newer. For vehicles 2005 and older, you must consult the vehicle manual for the lower anchor weight limit.

Do seat belts have weight limits?

Seat belts are tested to withstand at least 6,000 pounds of force – and can hold even very large adults.