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Before You Buy

Vehicle Compatibility

  • Diono convertible car seats fit in many cars, but we cannot guarantee a correct fit in 100% of the cars on the market.
  • No car seat fits every vehicle on the market.
  • The best way to figure out if the car seat will fit is to try before you buy. Most retail stores will allow you to take the car seat out to your car and see if it is compatible.
  • You can also take a look at measurements of the Diono Convertibles to assist your assessment. Measurements can be found on each of the product pages on the Diono website.

As of September 2016, Diono has approved the use of all current models of Diono convertible car seats and booster seats with Ford Motor Company’s Inflatable Seat Belts. This allowance is retroactive to previous Radian convertible and Monterey booster models.

  • Generally all Diono convertible seats install exceptionally well in most vehicles.
  • There is not one car seat on the market that can fit properly in every single car.
  • There are particular challenges with seat belts buckles that lean forward and are rigid.
  • Sometimes the belt webbing pinches and does not allow for the belt to tighten further, resulting in a loose and incorrect install.
  • It has been our experience that this is a compatibility issue with the vehicle and we would not recommend using our car seat in a seating position with this type of seat belt buckle.
  • Look carefully, there might be another seating option in your vehicle, as there can be up to five different types of belt configurations in one vehicle.
  • Radian Convertible car seats fit three across in most midsize vehicles.
  • A good rule of thumb is to have at least 51” from door armrest to door armrest.
  • You can take a look at the hip measurement of your particular vehicle.
  • Using the seat belt, instead of LATCH, for all three car seats allows more flexibility to fit the three seats side by side.
  • Install the center seat first and then the outboards.
  • Rainier, Pacifica and Olympia models feature extra deep side walls and still offer a space-saving design, as their bottom portion is narrow. With the addition of the deeper sidewalls, the top of the seat is wider than the radian rXT by 1.5?. The seats offer a space saving design that allows for a passenger to comfortably ride between two installed seats or for 2 adults to sit comfortably with a car seat installed in the center.
  • Three across can only possibly be achieved if the vehicle has over 54” of room side to side.
  • Cambria and Monterey booster seats are designed to accommodate growing children and have a wider seat base, therefore they cannot fit three across in most vehicles.
  • All car seats are designed with a 50th percentile child in mind and tested with the same size child test dummies.
  • Pediatric growth charts are used when test dummies are designed and manufactured. Anthropomorphic test dummies (ATDs) are not designed by car seat manufacturers.
  • Therefore, our testing matrixes are limited to certain size test dummies to use for testing. Since these specific ATDs fit our car seats, weight and heights are determined based on these specific test dummies. Children grow at different rates, shapes and sizes.
  • Your child may or may not be able to use the seat up to the maximum height and weight limits.
  • We typically see children outgrow the seats by height, not weight.

Read all about it in our blog post, May the Force Not Be With You. The article goes in depth about the extreme forces occurring at all points of contact between a person and their vehicle seat.

  • If occupants are not snug, this will add to the “G” forces that their vulnerable bodies will have to absorb, as they move still further until they reach the restraints.
  • The resulting impact forces and whipping action can produce severe trauma to a child’s head and neck, resulting in far more serious harm to a baby or child than from front or rear end collisions.
  • Most automobile accidents are from front or rear end collisions, however side impact crashes are typically the most deadly for children.
  • Statistics from the Children’s Hospital of Philadelphia in the U.S. show that side impact crashes represent approximately 25% of all motor vehicle accidents.
  • Unfortunately they result in some of the most severe injuries and mortality rates, and the most vulnerable are children.
  • Diono developed side impact protection for its car seats by creating a rigorous testing protocol that simulates side impact crashes.
  • The seats were evaluated on how well they contain the head, and reducing chest and pelvis acceleration. Testing was repeatedly performed in multiple facilities both in the US and in Europe.
  • Diono Convertible+Booster car seats feature deep, reinforced sidewalls that extend straight forward and are lined with thick, energy absorbing foam. Sidewalls must have proper size, shape and strength in order to contain a child, provide protection and absorb side impact forces.

While there are currently no side impact standards that any car seat manufacturer must meet, having a car seat with additional internal head wings, with a strong structure and energy absorbing foam like the radian rXT and rainier, does provide more protection for a child’s head.

  • It is important for a child’s head to stay contained within the shell of the car seat during a side impact collision.
  • Having the head stay in line with the neck and spinal column is also beneficial and therefore, having the head wings help in this case.
  • Keep in mind though, most side impact crashes have more of a frontal component to them, thus pushing an occupants head more forward and then to the side during such a collision.

Some children may have a hard time adjusting to head wings.

  • They can interfere with their peripheral vision or make a child uncomfortable with material so close to their face.
  • Our radian r100 and r120 all-in-one convertible car seats without internal head wing provide some side impact protection.
  • The majority of crashes are frontal collisions.
  • Side impact can occur on either side of the vehicle.
  • Statistics show almost an equal amount happen on each side.
  • One side is not safer than the other.
  • Center position can possibly provide more protection as it keeps an occupant further from an intruding car or object.
  • No two car crashes are the same and it’s hard to predict which is best.
  • Install the car seat according to the user manual.
  • Most car seats on the market have between a 6-8 year expiration dates.
  • Car seats expire due to various factors.
  • Mostly, the manufacturer has tested the seats for extreme cold and hot conditions to determine how long the lifespan of the seat is before it degrades and is still able to perform properly in a crash.
  • Secondly, like any new technology, car seat manufacturers are always improving their seats and want you to take advantage of any new safety advancements.
  • Diono Convertible+Booster car seats are ahead of the curve, made with a fully integrated steel frame which is riveted together with thicker engineered plastic to withstand severe crash forces.
  • Diono Radian models expire 10 years from date of purchase and approved for the use of harness mode for 8 years and up to 10 years in booster mode.
  • Diono Rainier, Pacifica and Olympia expire 10 years from date of purchase and approved for the use of harness mode for 8 years and up to 10 years in booster mode.
  • The Monterey booster has an 8 year product life. The Monterey XT, Cambria, Hip and Solana have a 6 year product life.
  • If your child has special health care needs, whether they are physical or behavioral, a conventional car seat like Diono’s line of car seats may be suitable for your situation.
  • First, it is important to consult with your child’s doctor, occupational therapist and/or physical therapist to determine their needs.
  • Next, take a look at conventional car seats on the market to see if there are compatibility features for your child to be safely secured in the seat.
  • Diono Convertible+Booster car seats accommodate high rear-facing and forward-facing harness weights.
  • They are also designed with memory foam for superior comfort.
  • Our seats tend to be ideal for all children who come in many shapes, sizes and smiles!
  • We also manufacture a special needs high back booster for R82. It is called the Pilot. Click here for more information.

Before You Install

  • Pay special attention to the WARNINGS in your manual on pages 6-8 and on the instructional pages of the installation scenarios.
  • Watch our installation videos before installing the Diono car seat
  • Get familiar with all the parts and features
  • Make an appointment with a Certified Child Passenger Safety technician to double check your installation. Most car seats are unknowingly installed incorrectly.
  • Mail in or register your Diono car seat online.
  • Call our Consumer Care Team 1.855.463.4666 between 8:00 am and 5:00 pm PST. If you have an urgent matter or questions, please call rather than email.

Diono All-In-One Convertible car seats fold flat for storage and travel convenience.

To Fold:

  • Unbuckle harness and remove the infant cushions (if used) and take out the red carry strap from behind the cover.
  • Unfasten both fabric side panels and open fully.
  • Loosen harness: lift silver lever (Cam lock) while pulling the harness straps all the way forward.
  • Raise head support to its top position.
  • Adjust both expandable sides to their inward position.
  • Fully loosen harness straps, pads, and chest clip, move towards the top center of the car seat.
  • Place car seat on its back, push either release lever downward to release locking bolts. Keep harness buckle lifted toward the top of the car seat while folding seat bottom up to avoid pinching the buckle within the fold.
  • Fasten red carry strap on the first metal bar to secure the bottom of the car seat in its folded position.
  • You can also watch our the Folding your Diono Car Seat video and the Unfolding your Diono Car Seat video

IMPORTANT: If car seat does not easily fold completely, do NOT force it closed. Repeat steps 1-7 if needed.

  • A patented, energy absorbing harness component that significantly reduces the forces affecting a child’s head, neck and chest in an accident.
  • It’s a load-limiting device designed to absorb energy and reduce impact to a smaller, forward-facing child. Younger, forward-facing children (under 40 lbs) have proportionally heavier heads, but less-developed neck strength.
  • All-In-One Convertible car seats are the only car seats in the world with this energy absorbing harness system.
  • To release, simply lift up the metal cam lock and pull the harness strap away from the car seat.
  • To tighten the harness, simply ‘pull, release, repeat’.
  • When you pull the harness snug, the cam lock lever will drop down automatically.

*** AAP and Diono highly recommend keeping children rear-facing for as long as possible.***

  • Detachable base must only be used when the car seat is rear facing! Do not use detachable base when the car seat is forward-facing. If you have lost the base, you can order a new one here.
  • Confirm seat is locked in its unfolded position. Watch our video, How to Unfold your Diono Seat.
  • Confirm adjustable bottom is flush with the bottom of the car seat. Watch our video, Using the Adjustable Bottom.
  • Align posts with holes and insert base into the bottom of the car seat.
  • Slide base back until it reaches alignment mark on the bottom of the car seat and secures into place.
  • Push in the metal tab to lock base.
  • Pull metal tab out to unlock base.
  • Slide base forward.
  • Pull base away from the bottom of the car seat.
  • The Angle Adjuster is a foam block specifically designed only for All-In-One Convertible car seats.
  • It positions rear-facing Diono Convertible car seats at a more upright angle for older children and can add up to 4” more room behind the front seats for more front leg room.
  • It is to be used only with a rear-facing seat and with a child that can sit up unassisted and has complete head control.
  • Do not use for a newborn baby.
  • Slide the Angle Adjuster underneath the bottom of the Diono car seat until it touches the back of the base.
  • Install the seat per the instruction manual.
  • (Must use for all-in-one convertibles manufactured after Dec 2014)
  • Adjustable bottom MUST be extended down for children 25 lbs. and over in a forward-facing installation.
  • You can watch our video, Using the Adjustable Bottom.

Lowering adjustable bottom:

  • Lift bottom bar up and over the inside channel towards the car seat bottom to release.
  • Confirm adjustable bottom is locked in its lowered position.

Raising adjustable bottom:

  • Lift bottom bar up and over the inside channel (follow the “c” shape channel) away from the car seat bottom to secure closed.
  • Confirm adjustable bottom is locked in its closed position.


  • Send in the registration card that came attached to the car seat or register online.
  • Upon removing your car seat from the box, unfold your seat.
  • Check to be sure the area is clear of debris
  • Remove body support and infant head support cushions
  • Check that your seat is in the unfolded locked position
  • Read the manual including all the warnings in the safety section of your manual. Get to know the parts, pieces, and accessories to your car seat.
  • Determine how you will be installing your seat. (See pages 10-11)
  • LATCH or seat belt installation
  • Top-tether
  • Booster
  • Safe Stop® *Diono only. Please note: Do not discard Safe Stop® as you may need this piece later during your child’s development.

(See pages 21-29)

  • Proper harness height and max child weights.
  • Harness buckle location and installation.
  • Side impact and head support
  • Infant support cushions
  • Properly secure your seat in your car.

Double check your work. Did you do a car seat stability check? A checklist is provided at the end of this section.

There are two ways a seat belt locks for a car seat installation:

  • Switching to locking mode by pulling the shoulder portion of the seat belt all the way out until it clicks and a ratcheting sound is heard. As the webbing feeds back into the “housing” unit, it will not be able to come out until the webbing is spooled all the way back in.


  • The seat belt locks at the latch plate (the metal part that is inserted into the buckle). Once all the slack is pulled out and tighten down on the seat, there is a part within the cover that cinches down on the webbing and holds it in place. Sometimes the latch plate might have to be rotated one half turn into the buckle to keep the belt from slipping loose.
  • Be sure the bottom of the car seat is adjusted to the open position.
  • Twist down the buckle stalk 1-3 full turns and then repeat instructions
  • Unbuckle the seat belt and allow the shoulder webbing to spool back into the housing unit 1-2 clicks and then re-buckle the seat in. Having a second person will make this easier.
  • Try another seating position.
  • Bracing is when the top or back of a rear-facing car seat touches the back of the vehicle seat that is in front of the car seat.
  • A rear-facing Diono car seat can touch the vehicle seat in front of it as long as it does not lift the bottom of the car seat off of the vehicle seat.
  • Most newer vehicles have advanced airbag sensors in the front passenger and driver’s seat and anything touching the back of the seat can affect the performance of those sensors.
  • Also, storing things in a seat-back pocket that weigh more than a pound or two can also affect the sensors. Storing things under the seat can also affect the sensors. Information on this subject will most likely be found in the SRS/airbag section of your vehicle manual.
  • If in doubt, call your vehicle manufacturer and ask if they allow anything to touch the back of the driver’s seat or front passenger seat.

If your car is too small or your front passenger/driver needs to move the vehicle seat back, purchasing the optional Angle Adjuster will help raise the Diono convertible seat more upright to give them more room. The Angle Adjuster keeps the Diono car seat from touching/bracing against the back of the seat. Only use the optional Angle Adjuster for children who can sit up unassisted and/or have full head control.

Booster mode in our convertible line begins when your child meets ALL of the following criteria:

  • Shoulders reach the 4th harness slot
  • At least 50 lbs.
  • At least 40” tall.

A level of maturity should be greatly considered before using the convertible in booster mode. A child who cannot sit properly positioned for the entire ride is safer in a 5-point harness.

  • The lap portion of the seat belt should fit low on the child’s pelvic bones and high on the thighs, much like on an adult.
  • The shoulder portion should lay flat on the center of the child’s collar bone.
  • Booster mode should allow for the shoulder belt to fully retract so it always lays flat against the child’s collar bone.
  • Vehicle design may vary on position of seat belt anchoring, D-ring position and/or belt system flow direction.
  • Vehicle seat design may dictate where all of these components exist. It is not possible for every belt positioning booster seat to function properly in every single make and model of vehicle on the market, just as every harnessed car seat may not install properly in every vehicle.
  • Booster mode should allow for the shoulder belt to move freely (retract) so that it always lays flat against the child’s collar bone.

If you are currently experiencing a seat belt that will not retract properly on your child in booster mode, please try the following:

  • Install the seat in a different seating position OR
  • Continue to use the car seat in harness mode OR
  • Contact Customer Service at 855-463-4666 in the U.S. or 866-954-9786 in Canada
  • Vehicle seat design and location of a seat belt may dictate if a seat belt can move freely in and out of a booster seat belt guide. It may not always be possible for every belt positioning booster seat, or every car seat for that matter, to function properly in every vehicle on the market.
  • We do not allow over-hang of any of our car seats.
  • While there are car seats which follow an 80/20 rule, all Diono brand car seats are to fit with the bottom of the car seat making 100% contact with the vehicle seat.
  • If you feel you have extenuating circumstances, please send a photo of your installed seat and our engineering team will evaluate your particular situation.


  • Infant Cushions are provided for fitting newborns.
  • You will find Infant Cushions with the box of a radian rXT, radian r120, and rainier convertible car seat.
  • You can purchase a set of infant cushions for a radian r100 convertible seat.

How long do I use the Infant Cushions?

  • There are no minimum or maximum height and weight requirements to use the infant cushions.
  • They help fit smaller children in the harness. Use your judgment based on the size of your child.
  • As they grow and “fill out”, they will not need the cushion unless they tend to be small in stature.

The harness pads and center buckle pad are required for seats produced through 2017, with forward facing. For seats produced in 2018 and later, the harness pads and center buckle pad are not required while forward or rear facing.

While older model Radian seats did not come with the larger harness pads, they still meet Federal Motor Vehicle Safety Standards 213.

  • Parents may call our Customer Care Team and order the larger harness pads, if they prefer (optional). Some parents choose this option, as the pads provide a little more comfort and keep a child from pulling the chest clip down out of position.

The Buckle Pad should always be used as it provides comfort and keeps potentially hot or icy cold buckle parts from touching a child’s body.

  • Harness straps should be at or just BELOW child’s shoulders.
  • Place straps over shoulders and over thighs Insert metal buckle tongs into the buckle.
  • Pull the harness strap from behind the back of the car seat to remove the slack, making the harnesses snug and comfortable on your child’s body.
  • Be sure harness pads are down and not pushing into the harness slots at your child’s shoulders.
  • Pull the adjuster strap located on the front of the car seat in between your child’s legs and remove the rest of the slack.
  • Pull harness pads (optional) up and connect the chest clip.
  • Place chest clip at armpit level.
  • Harness straps should be at or just ABOVE child’s shoulders.
  • Place straps over shoulders and over thighs Insert metal buckle tongs into the buckle.
  • Pull the adjuster strap, located on the front of the car seat in between your child’s legs, downward and remove the slack out of the harness.
  • Pull harness pads up and connect the chest clip.
  • Place chest clip at armpit level.

IMPORTANT REMINDER: Harness should fit snug and comfortable on your child, at the collar bone. Gently try to pinch the webbing at the collar bone with your thumb and index finger, as if you are massaging their shoulder. If you can pinch too much webbing, snug the harness some more. Even if you have a tight harness, you will be able to get your hand under the chest clip and near the stomach. Checking at the collar bone will give you the correct indication the harness is fitting correctly.
A harness needs to fit close to the child’s body when adjusted to a snug and comfortable fit.

  • Placing a child in a thick, puffy winter coat before harnessing can pose some danger.
  • First, it gives you a false sense that the harness is actually snug enough on your child.
  • It also makes it difficult to make it tight enough and can prevent proper placement of the chest clip at armpit level.
  • This may cause the straps to come off the shoulder during a crash and partially or totally eject your child from the seat.
  • If you live in colder climates, we realize coats are a necessity. Check out our blog post, What’s the Fluffing Problem for suggestions on how to accommodate for these situations.
  • While the chest clip is not a regulated part of the car seat it can help keep the harness properly placed on the child’s shoulders. Therefore, they are a positioning device, but not necessarily an essential piece of the car seat. In fact, chest clips are not even allowed on car seats in Europe as regulations require a “one step” process to remove a child from a harness.
  • Regardless, Diono does recommend the use of the chest clip at armpit level on its US & CA car seats.
  • The chest clip should be the last step in securing your child in the harness. Once the harness is adjusted and snug, raise the chest clip up to armpit level and connect both ends.

Shipping Information

Orders can take up to 2-5 days to ship.

Once your order has been shipped, you will receive an email with your tracking number.


Yes, all Diono car seats provide reinforced side impact protection, and some models offer the increased protection of an adjustable head support. Currently, there is no U.S. or European regulatory side impact testing requirement. A manufacturer can make the claim of “side impact safety” without meeting any standard. Diono’s radian rXT and monterey XT models were side impact tested to the widely accepted German standard established by ADAC, Europe’s largest automobile club.

If you are experiencing some forward movement on the bottom of the seat, please follow these steps to reinstall and check for tightness of your Diono convertible car seat. You should first reposition the car seat on the vehicle seat and reinstall the car seat. You then should check fo9r tightness at the forward-facing belt path. A tight car seat should move less than one inch side to side and front to back when checking only at the belt path. If you have accomplished this tight fit, your car seat is correctly installed.
Checking at the front of the car seat is not the correct place to check for a tight fit. The car seat does not get secured at the front base of the seat. All crash loads are being taken down at the forward-facing belt path, not at the front of the seat. This is the exact procedure used while undergoing crash testing.

FMVSS213 does not require child seats to achieve performance results with RF children above 22 pounds and for FF children above 50 pounds. Radian, Rainier and monterey XT meet all the performance standards with all weight children, RF and FF. Radian does this with and without using top tether.

Replacement SuperLATCH components can be ordered, but radian seats can only be used up to the LATCH/UAS capacity stated on the stickers that are affixed to the seat.

Yes, all Diono child car seats (with integral harness) are certified for use on aircraft.

As of September 2016, Diono has approved the use of all current models of Diono convertible car seats and booster seats with Ford Motor Company’s Inflatable Seat Belts. This allowance is retroactive to previous radian convertible, monterey and monterey XT booster models.