When to use the top tether strap?

I have seen much confusion around car seats with tether straps, and those without, when to use it, rearward and forward use. So let’s clear this up in this blog post.

Firstly it’s important to remember that New Zealand allows the sale of 3 different countries standard of seat, and as such, each standard has differing requirements in regards to the top tether.

Australian car seats.

Australian standard, AS/NZS 1754

Known here as the Safe N Sound, Mother’s Choice, IGC, Infa Secure, some Safety 1st and Maxi Cosi branded seats.
Australian seats are currently identifiable as seats with height markers on the cover around the shoulder (since 2010-2012), they also have a tether strap that comes out from the top back sides of the car seat. Or a single strap that can be split off, as two straps, found on seats that install rear and forward facing, some forward facing only seats have a single strap these days, such as Maxi cos (the same as our Safety 1st complete Air, without rear facing ability).
These seats require the top tether to be used at all times, in both rear and forward facing positions, the strap must pass to the rear of the car, and in some cars will require an extension strap to reach the bolt if tucked in the far rear of the car.

In short – Always use, to the rear of the car.

 American seats

FMVS 213 – Show a yellow “S” mark (NZ Standard)

They come as bit of a mixed bag these days. The likes of Evenflo, Diono, Britax, Safety 1st, etc. They have a top tether attached and are designed for use forward facing. Some of these seats, Diono RXT, Diono R100 and Britax Boulevard can be used tethered to the front when rear facing attached to a “D” ring. All other American seats sold here need to be used with no tether when installed rear facing. The strap must remain attached to the seat shell, so it does not become a projectile risk.

In short – not required rear facing. Not all seats allow tethering to the front of the car, check your seat manual.

European seats

UK ECE 44.03/44.04.

Some have top tethers, some don’t and some tether to the front seat in front of the car seat, using 2 straps.

Brio Zento, Axkid and Britax Max Way seats use the dual straps to the front seat.
Many other UK seats sold here do not have top tethers at all, they cannot be added either. They rely on a full lap & sash seat belt for the install, wrapping around the back of a capsule (unless used with an in car base), and weaving awkwardly in and around the frame of a forward facing seat, the shoulder strap of the seat belt acts like a tether strap for the seat. Capsules often need the handle to be turned forward when used in the car if not used with a base.

In short – probably not likely to have a top tether, and if it does it typically found on rear facing only seats.


Comparison – Convertible Seats/Boosters

S170 – Safety 1st 70
MXEA – Maxi Rider Easy Adjust
ESK – Evenflo Secure Kid
CSC – Cosco Scenera
ETB – Evenflo Tribute
BSI – Baby Safe Isofix
ES3 – Evenflo Symphony E3
F90 – Frontier 90


Harness slots
CSC- 20, 26, 33 and 38cm
ES3- 18 through to 43cm (infinate)
BSI –  20, 26.5, 34 and 39cm
ETB - 21, 26, 31, 36 cm
ESK – 32, 36, 41, 46 cm
MXEA -  26, 28, 31, 33, 36, 38.5, 40, 43.5 cm
S170 -  22, 28, 32, 38, 42 cm
F90 – 29 – 48 cm

Buckle slots
CSC- 9, 13 and 16 cm
ES3 - 17.5cm
BSI –  17.5cm
ETB- 12, 17 cm
ESK – 13, 18 cm
S170 - 10, 13, 16 cm
F90 – 17, 23.5 cm

Seat width
CSC- 44cm
ES3 – 56cm
BSI –  41cm
ETB – 45cm
ESK – 47.5 cm
MXEA – 44cm
S170 - 45 cm
F90 – 48 cm

Internal width
CSC – 32cm
ES3 – 56cm
BSI - 26cm
ETB – 32cm
ESK – 29cm
MXEA – 37cm
S170 - 32cm

Legs width
CSC – 30 cm
ES3 – 15.3 cm
BSI - 26 cm
ESK – 31 cm
MXEA – 29 cm
S170 - 34 cm
F90 – 30 cm

Bum to top
CSC- 59cm
ES3 - 63cm
BSI - 63.5cm
ETB – 56cm
ESK – 73cm (HR Max setting)
MXEA – 78cm (HR Max setting)
S170 - 69cm (HR Max setting)
F90 – 60 – 79 cm

Bum to legs
CSC - 28cm
ES3 - 33cm
BSI – 33cm
ESK – 29cm
MXEA –  29cm
S170 - 30cm
F90 – 35 cm

Measurements are taken without compressing the fabric (only lightly) and shoulder and leg widths are taken from the middle shoulder slot and approx. 10cm in from the front of the leg area.


This post entails a review done by New Zealand Child Restraints on the Britax Frontier 90 combined booster seat, dated October 2013. To see a larger image, click on the photo.

Brtiax Frontier 90

Britax Frontier 90

Basic seat facts:
Forward facing 11 – 54 kg (76 – 157 cm) At least 24 months old.
Harness mode to 40 kg
Maximum height – 157 cm
Standard – NZ “S” 1754 New Zealand + American FMVS 213.
Lifespan – 9 yrs

The Seat:
9 – height slots –  Adjustments from 29 – 48cm
Maximum booster slot height – 54 cm
2 – buckle slots – 17, 23.5 cm (from back of seat)
Seat width – 48 cm (across leg area)
Shoulder width – 32 cm
Leg width – 30 cm
Crotch buckle length -16.5 cm (Including buckle head)

Bum to top  - 60 – 79 cm
Bum to legs – 35 cm

Shell height – 71 – 91 cm
Back width – 34 cm
Base depth –  41 cm

Chest clip
locking clip
Cup Holder x2
Push in lever to adjust harness.
Padded cover
Single engaging buckle tongues
Latch and top tether attachments
Easy install method

About the Frontier 90

A very generously sized combined booster seat (forward facing only) for children from 2 yrs. of age to they no longer require a car seat. This seat will fit many children to at least 8 years of age, quite possibly longer.

The seat harness is easy to adjust with one hand, just squeeze the lever on top of the seat head rest, and slide the headrest up, or down to the desired position (at, or above the shoulder). With 9 height adjustments is easy to move when needed to help maintain it as closely to the shoulders as possible.

The seat shell features plastic with steel reinforcement. It’s heavy but like other seats on the market, very solid and offers less flex during an accident.

Installation is a breeze, sit seat in the car, open front plate (under the child’s bottom) by sliding the buttons towards each other. The panel opens upwards, feed the seat belt into the belt path, passing both parts of the webbing through behind the armrests. Buckle the seat belt in, remove slack – no compression of the seat needed, and does not need to super tight, just a gentle pull, snap front panel back into place. The seat does not move, if so, open panel and pull a little bit more slack out (may be needed in cars with leather seats) and re-engage the front panel.

Top tether not required with children less than 29 kg (though can be used at all times, and should be where possible).

Seat also features isofix attachments, though with the super easy install method, it’s not like you’d need to use them.

Available in Onyx fashion, black with beige pin stripe, check patterning. Nylon fabric, easy to clean and wipeable.


- Super easy to install
- High shoulder slots will last children to booster age easily
- Front recline lever
- Latch attachment slots to store away when not in use

- Heavy seat
- Headrest foam may break easily if child pulls on it (while seated/mid tantrum)
- Headrest cover does not seem to fully cover headrest, which may help with above mentioned issue
- Awkward to carry

Expected retail price of this seat $549, from:

1013a Dominion Rd
Mt Roskill

(Corner of Mt Albert and Dominion Roads, Enter driveway on
Mt Albert Road between Church and Christian bookshop).

Shop hours are Mon-Fri 9am to 4.30pm
Saturday 9.30am to 3pm



Please note, the “Frontier” model has existed in the US since 2007, they have had various models and features have differed between these. The model being sold here is the Frontier 90, this seat has the Click Tight install method, no side impact cushions, cup holders are solid back, the arm rests are fixed and cannot pivot. Some of the stores selling them have used the incorrect stock image. The images shown here are of the correct model, as sold at Kiwibaby.

Expressions expressed in this Blog are that of our own and not influenced by a third party or sponsoring company. Images used on this page are our own, stock photos, or images used with parents permission. Please do not use without permission.