The ultimate seat mod DIY for adding adjustable lumbar support on a Prius or any other car seat

OK fellow drivers. I've suffered the lack of lumbar support and terribly uncomfortable car seats for long enough. I refuse to give into the trap of buying a more expensive car just to get comfy seats. I'm a courier so I drive about 200 km in a day on average and my 2010 Prius which I bought used with 230,000 km is the best car for the job in terms of cost to buy and own, but the seats are garbage for this much driving. And other vehicles just don't make sense for me to buy just to get more supportive seats. Even though I could afford it, I don't want to buy something like a Lexus because I'll be using it for delivering packages. Lexus hybrids use way more gas than a regular Toyota Prius anyway. Aftermarket seats are too expensive as well and I don't want to deal with airbag issues. I do believe Toyota and all other car companies purposefully build uncomfortable seats in their economy cars to sell people on more expensive cars. I don't think it costs anything to design a seat that adequately supports your back. Another issue is that Japanese cars may also be made for smaller Japanese bodies. So here is my way of solving this problem and I hope many people follow suit if they want to save a ton of money. This DIY is for my 2010 Prius base, but it can apply to any other compact car (especially prii) as the seats designs are pretty similar for most Asian economy cars such as Honda Civics, Hyundais, Nissans, Mazdas, etc.

This upholstery DIY is brutally simple but there is about a 2 hour time commitment and a materials cost of about $44.10 US plus any taxes and shipping if you buy them on Amazon like I did. Note that this procedure may not work for power or leather seats. Heated seats shouldn't be a problem. My seats are cloth with no power or heat. Pictured below is the finished seat.




Tools and materials:
-Wire cutter and 2 pliers
-14mm socket wrench
-10mm socket wrench or a small adjustable wrench
-About a dozen large zip ties
-Some double sided tape or liquid paper glue
-An inflatable Back Lumbar Support Cushion on Amazon $26.99 (Alternatively, you can just use more layered foam shaped into a mound instead)
-A 1/2" thick 24"x24" Memory Foam Sheet on Amazon $17.11


- Below: Inflatable Back Lumbar Support Cushion on Amazon, $26.99 at the time of this writing. Take the inflatable air cushion out of the cover by detaching the hand pump valve. The cover is not used.



Pictured below right is the 1/2" thick memory foam sheet sold on Amazon. This may also be available in your local foam or upholstery store.




Step 1: Detach the seat from the vehicle.

Simply remove 4 14mm bolts and 2 electrical connectors from under the seat and fold the seat forward.


The rear bolts are covered by plastic covers. Simply pry them off from one side and unbolt.


Carefully lift the seat out of the car and place it on a thick cardboard. I used cardboard because I worked on in on my carpeted floor, but you can use a work table or the concrete floor. Whatever you do, don't do this on hardwood floor. Place the seat faced down in your work area.





Step 2: Peel up the seat back cover.

Release the elastic band under the seat bottom that holds the back flap down.


When you flip the flap up, you will see several metal link fasteners like the ones below. These fasten the top seat cover's inner flaps together and 2 tension ropes to the seat frame. Remove all of them using your pliers (Ignore the black zip tie I used in this pic. This is after I've done the work so it shouldn't be there at this point). This might be the most challenging part of the diy.



Once you've done that, you can unzip the 2 bottom zippers and peel the cover up. In the pic below, notice how the stock seat design has your entire back supported only by 2 wire-like thin rods and a flimsy plastic flap! That white foam pad between your back and the support hardware is only about an inch thick! Can you believe that that is all that is holding your back from falling through the seat?What a joke. Nobody notices this when they test drive cars for purchase. What a scammy cost cutting tactic by such a reputable automaker brand.


Unbolt the anti-wiggle straps that keep the seat cover from moving side to side as the driver enters and exits the car using a 10mm socket wrench.


(Optional) I cut the front half of the strap because this blocks the left side bolster to which I will be adding memory foam onto to maintain the bolstering. This strap only secures the seat cover as you exit the car so it's not crucial IMO. This is optional if you will not be adding cushion to the side bolsters.



Peel up the cover, paying attention to the rope configuration as you need to reinstall them.





Step 3: Place the cushions on the seat and cut it to the right shape.

Take some double sided tape or glue and stick the inflatable air cushion on the lower back portion of the seat. Position it carefully in the right spot by placing the seat upright and sitting in the chair with the cushion in place, so that you can feel that it is in the right and comfortable location.


Then, place the memory foam insulation over top of it so that you can cut it to size. IMPORTANT: be very careful not to over cut, as you only get 1 chance at this. Use a black marker to draw the lines and cut a little at a time.


Here is the shape I cut. I covered the side bolsters so that they can maintain some bolstering after the increased lumbar effect. The air cushion is underneath. Note that the seat cover is peeled only half way up. It seems that the upper back portion of the seat extremely difficult to access. If I could easily remove the entire seat cover, I would have added foam to the whole back of the seat, but I decided it wasn't necessary. Variation tip 1: You can also get creative with this by doing things like adding more foam just to the side bolsters, using different foam materials, foam densities, foam shapes etc. Variation tip 2: Instead of just adding cushions where I did, you can also add support behind the seat back foam, between the seat back foam pad and the support hardware directly behind it. For instance, you can install a sturdier flex plate that covers a larger back area with increased rigidity.




Step 4: Replace the seat cover.

Now this is the tricky part. You want to slide the seat cover back down over the cushions you've added without moving the cushions. First, thread the ropes back into their sleeves.


Then carefully slide the cover down one side at a time, bit by bit, while one hand holds the cushion inserts underneath. This part was difficult to photograph, so you'll just have to do it the best way you can. Important: At this point, sit back in the seat and test the air pump cushion for proper placement. You can still adjust its location by sliding your hand under the cover.




Step 5: Re-fasten the seat cover and install the seat back into the car.

Re-install the seat cover anti-wiggle strap(s).


Using wire or zip ties, re-fasten the securement points you released in step 2.


Pull all parts of the seat cover down tightly, zip everything back up, and tuck all the loose ends in and the seat is ready to go back in the car. Reinstall the seat back into the car using the 4 bolts, 2 electrical connections and plastic covers shown in step 1 and the job is complete.





Final remarks:

This mod made a world of difference in my car's ride quality! I even used to feel back pain when I depressed the brake pedal because of the lack of lumbar support. But now because of the lumbar support, my braking as well as my overall driving has improved, and I feel like the car is easier to drive. My head movement feels more natural and there is no more neck strain from shoulder checks. But one annoying thing is that the inflatable air lumbar cushion has a tendency to shift the air from one side to another. If this becomes more of an issue, I can easily switch to all foam at a later time. I hope this allows other people to keep driving their cars instead of losing money buying a new car due to uncomfortable seats!

And folks, trust me this is much easier than it looks. All you need is a bit of planning ahead of time and very simple tools and materials.

 

I've considered it, but I didn't want air bag issues. Also I just wanted to try this inexpensive option first and on top of that it was kinda fun.

 

Maybe later!

 

I've read that most Toyota lumbar adjustment is designed to use a mechanical bulge rather that an inflatable air bag. I've test drove a 2014 Prius V with the mechanical bulge lumbar and it was immediately uncomfortable. If I had that I'd make mods to it as well since I know it's pretty easy now.

 

One change I would make to my DIY is to use some kind of easily reusable fasteners instead of zip ties for the seat cover fastening so that you can easily make further mods later on.

Another option I thought about before doing this was to make an inflatable cushion pad that sits on the outside of the seat. This will be considerably easier but I just decided to do the hard way of actually putting it under the factory seat cover. The disadvantage of the exterior pad is the inevitable wiggle of the pad every time you get in/out and having to fabricate a custom cover and fasteners for it. It would most likely look bad too.

 

Lol didn't know they were called hog rings

 

Update: Another change I would make to my DIY is to forego the use of an inflatable air cushion and just use more fabricated foam instead because the cheap Chinese made air cushion that I used does not hold air pressure 100% all the time. It has a very slow leak which requires some periodical pumping. It's not too bad, but the right amount of foam padding would be a lot better, and this would also prevent side to side air shifts. Right now I am driving in completely deflated mode and I still feel extremely comfortable.

 

Update: I have implemeted all the improvments discussed in this thread and created a new thread detailing how I did it here:
Prius Seat Mod 2.0 (Gen 3 Prius seat upholstery DIY)