Making a Height Adjustable Driver's Seat for 2009 Prius

** Initial project completed 1/19/10. 3 weeks & 5 days working every day at it along with full time job. Main thing I would do differently (besides not buying this car again ) is spend about $200 more and start with a brand new Corolla frame to save time of finding a good used seat and polishing its frame. **

12/24/2009 -

I will be using PriusChatter 'Solar_Powered's method for making a height adjustable 2nd generation Prius driver's seat using a Prius seat and a Corolla seat, described in .pdf below. Many thanks to Solar_Powered !

View attachment Prius_Height-Adjustable_Seat.PDF

I bought a driver's seat out of a 2006 Corolla LE today from a junkyard in San Jose. I'll use its frame and my 2006 Prius seat purchased May 2009 for making a mechanically height adjustable seat with airbag for my 2009 Prius.

The seat, which I'll call a priolla seat (it's a hybrid ), will also be mounted 2 5/8" back (equivalent to about 4 extra 'clicks' back). The height adjustment modification alone does not provide more backward seat travel than Prius seat. But the height adjuster allows the back of seat bottom to lower about 2" more than a Prius seat.

I can get a better view out of the windshield and side windows, increased thigh support due to tilt down of back of seat bottom, and more legroom (by mounting further back with 'extender' braces).

Lack of telescopic steering wheel in the 04 - 09 Prius will limit usable adjustment, but this mod will be a big improvement. Many of the lower end Toyotas from years 03 - 08 did not have telescopic steering wheel (i.e. Corolla, Matrix).

Measured Weights

Prius seat - 39 lbs.
priolla seat - 41 lbs.

The Corolla seat below was $273 with tax, a little surface rust on frame which is common from salvaged vehicles, but it's cleaning up nicely, is solid and most importantly, not bent. The car had no hits on the doors.

This Corolla seat was tough to find. Over the last month, I checked out one 60 miles away that was bent, had another one shipped to my house (using www.car-part.com ) with a bent frame, and drove 60 miles to pick up a paid for seat (through car-part, LKQ) shipped in from Utah, to find it totally rusty (must have sat in snow, got refund). Every other junk yard in the phone book said, no, they do not have a Corolla seat.



The seat fabric and trim is Beige, but I have a light Gray 05 Corolla seat (whose frame is bent, argh) and my 06 Prius seat to use for parts to meld into the seat above.

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1/25/10

This is what I think is mainly wrong with the Gen2 driver's seating -

1) No telescopic steering wheel / wheel quite close to dashboard
2) Limited backward seat travel
3) No seat height adjuster
4) Fairly short / small seat bottom with poor contour IMO
5) Awkward placement of brake pedal (centered in front of seat and too close)
6) For some, not enough lumbar support
7) Touchscreen placement lifted from Gen1 design, mounted high and recessed in dash, may very well have precipitated the limited driver's seat travel.

The 2004 - 2009 Prius driver's seat bottom portion of the frame is set (with thick steel brackets) 2 inches out of 2.5 inches up. IOW, it is 80% or most of the way up. A tall person may have enough headroom with the Prius' dome shaped roof, but how can a tall person see upward out of the steeply slanted windshield?

I think Toyota ought to have offered height adjustable driver's seat in all Prius' by 2006 or 07, a year I believe they made a number of upgrades to the 2nd Gen car. Italy and likely more countries had the left side height adjustable driver's seat. Many countries had the right side HA seat too, including Japan. Given average heights are less in Japan, why would they be offered a seat that can drop lower to the floorboard and not the US, North America?

This mod is not so easy. Requires tools, space, money (I've spent nearly $2,000 in this big mod and several minor ones as of Sept. 2010), time, at least 2 seats you're willing to alter, mechanical skills, and, quite a bit of determination.

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** Disclaimer - This is a do-it-yourself type of project which voids the warranty of driver's seat when installed in car. It most likely affects the front and side seat airbag functionality, and could compromise safety in a collision. Using a seat like this is at your own risk of serious injury or death of yourself, other persons and could cause major property damage. **

 

I put the Corolla seat bottom into full up position for disassembly and cleaning.

The frame is upside down. The fat round bar of seat bottom can lower about 2.5" into the plastic notch shown in pic. It also moves back about 1".

In the Prius frame, that round bar is fixed about 2" above the plastic notch and ~ 1/4" forward ... so the Prius seat is 80% fully up.



Next is to remove fabric and foam from seatback, then get into the tough job of removing the mounting feet (Corolla mounting feet do not fit into Prius, must weld Prius feet on).

 

Tada, one naked Corolla seat. The seatback, except for the top headrest bar, is a 'spittin' image' of the Prius seatback - identical. The lower section can accomodate both Prius and Corolla seat bottom foam, and has mechanical height adjustment.



I had an evil thought when driving home after shopping well over an hour for special hose jaw pliers to release the headrest supports ...

to ceremoniously destroy the used Prius seat frame at the end of this project ... hehe

anyrate, back to work

 

edit - ** the frame is not tweaked or bent. Something not locked in place when looking at it last night, wshew, what a relief **

Oh darn, the 06 Corolla seat frame appears tweaked when looking into the front of seat bottom, and a level shows the back bar and front pan are not in horizontal alignment.

I have a plan B in place which is to buy a new Corolla frame from Toyota, $425 + tax. I'd like to avoid that.

 

I got the Corolla seat stripped down, so I'll show how it sits in the car.

With seat centered, can see how different the Corolla feet are from Prius floorboard. Prius feet go inward.



Checking clearance between the frame and nav unit shroud. There is one connector that may bump the shroud while sliding, but shouldn't be hard to find a workaround.

Wallace and Gromit made it into the photo, my favorite book to use for a prop



There is plenty of room for the height adjuster handle. I have a Gray handle too.

 

I just got through sweating a bit while removing the seatback foam from my 2006 Prius seat. Look at that bad boy airbag hanging on the side. There's danger labels written in 4 languages on the side of it.

Such a shame, this frame is so clean. It just doesn't have the feature I really want. C'est la vie. Gotta make the best of it from here.

 

I was like ... don't .. drop ... the airbag. It's in a shoe box tucked away for a while.



I will cut the feet off the Prius frame and drill, chisel and pry the feet off Corolla frame. It might take a couple weeks to build this frame because of needing the services of a professional to TIG weld the Prius feet and headrest support bar on Corolla frame.

 

Note - wear a dust mask when cutting. I did everytime after this photo. Makes goggles fog up. Better than breathing metal dust.

I am cutting the left front Prius foot off the frame (cold in garage). Actually, I'm not cutting the foot itself ...



... I'm cutting the weld between seat rail and an extender brace which already has a foot welded to it (see below). I need to get my face back from the work in this photo. Tasting metal dust, not fun. I did the extender mod in May, before the www.extendmyseat.com brackets came out.

Reusing these feet will save me time and money in not having to buy another Prius seat for its feet, nor having to drill and pry those feet off.

Pic below the welds are underneath the brace on 3 sides of the foot. The silver bolt is reinforcement. The burned area is where it was welded onto the Prius seat rail.

There is a bend in the brace such that the seat rail is in the same plane as stock mount. This is necessary so the left rail will sit flush on the left rear mount foot. I wish the steel plate was a heavier gauge (I think it's 12), but it has not bent of course, and if it did in a bad way, well, I would sell the car.

 

Before starting to cut more, I wanted to point out the 'height' of the Prius frame -

The horizontal bar is a little over 2" above the plastic notch (hard to tell from camera angle, but it is) and directly above it. This means the Prius seat bottom is over 80% the height of the Corolla seat in full up position, or most of the way up. This puts me too high in my car such that I often cannot see traffic lights or building signs very well and end up needing to duck down a lot to see.



... and as this photo shows, it's fixed there. That is one beefy bracket.



The first photo also shows one would not gain any more seat travel backwards than a Prius by only doing the height adjuster addition with Corolla frame.

Trivia maybe, but just so you know.

 

I bought a brand new Prius seat foam cushion, $198 from Toyota. I carved up the other one in an attempt to better the seat. I'll be happy to cut the semi-circle to make room for the round height adjuster mechanism.

 

Lucky me, I was able to cut all 4 Prius feet off the 2006 frame (they had been welded allowing seat to slide 2 5/8" further). If it had gone wrong, I would have needed to buy another used Prius seat for a couple hundred bucks. These feet are in good shape and can be re-used for the Corolla frame.



Next is to remove the 4 Corolla mount feet from the frame. I drill a pilot hole through each rivet and spot weld of each Corolla foot. I cut the prongs off the front feet with a dremel rotary and cutoff wheel. I'll widen the holes just enough to chisel off the rivet head but not drill into the rail, then remove the rivet. The spot weld is quite difficult to drill through and requires special bits. I widen that hole enough so it's not too difficult to pry the foot off (you do not want to twist the seat rail, so never pry to the side!)



I don't have a drill press, so I'm the human drill press



This is a big project. It will take at least 2 more weeks to get a height adjustable seat in the car.

 

Now that is a beautiful sight ... 4 Corolla feet removed from the seat rails, ready to take on Prius mounting feet. But first, the Corolla headrest support bar gets removed.

 

I sat down to do a little planning with both frames side by side. Noticed the Prius front 'pan' (I think it's called) sits higher than the Corolla, which is adjusted to max height. Hmmmmm. More kneeroom under steering wheel? Maybe.

 

I spent part of the day polishing all the 'nooks and crannies' of the frame while watching (more like listening to) football. Then I washed the car.

I'll be talking with the metal shop soon to get scheduled in for welding.

 

I talked to my welder at a large metal fab business this morning and he's available to work. Goal is to get the Prius headrest support welded onto the Corolla frame this week for sure.

This weekend I'll bolt the front braces on, pull the original seat, set the frame in car and get it ready for welding the feet next week.

That's the plan.

 

Oh darn, I hit a surprisingly tough part of the project - cutting the headrest support bar off. It must be done ... on both frames. The Prius seatback foam/fabric will not fit over the Corolla upper, and if can't get Prius seatback foam, then no airbag. This is not an option.

This cutting near round tubing makes cutting the feet off the seat rails (like I did last week) look easy. Rough night, 3 trips to the harware store too.

I'll pick it up tomorrow.

 

Obviously I will need to pull the headrest bar straight up to remove it, so the first step will be to grind the weld beads flat on the round bars.

Note - Rotary 'Dremel' cutoff wheels are very versatile. They work better than a grinding bit for removing weld beads.

I should be able to remove this headrest bar tonight.

 

Oh boy, cutting off the headrest bar officially stinks. The weld beads are also hidden under the metal so it becomes a game of how much frame to remove to get the part off. Meanwhile, I don't want to cut into the frame because, it's the darn seat frame!

This is the worst part of the project - tedious and no fun.

 

Good news! One side of the headrest bar finally released and let go.

I found the key is to cut each bead flat, then cut underneath the frame, tangent to the round headrest bar. You have to work all 3 beads enough until the bond gives out.

The other side also looks challenging as it has a spot weld also, argh.

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This is the one part of the project where I've had faint thoughts that it may not work out. But, failure is not much of an option. I'm not just doing this for fun, I'm doing it to keep the car. If this fails, I'm finished modding the driver's seat, I will try to sell the car, and I will not be buying any other car soon. That would stink.

 

Wshew, one down one to go. Seems I used the right tactic to cut the Corolla headrest bar first to get experience.



I cut right into the Corolla bar not knowing quite how to do this, but this bar gets thrown away anyway. Perhaps a little more plannning and I would have known to cut tangent to the bar. Now I know.