REVIEW: ExtendMySeat driver's seat extenders

[JimboK]

Introduction

One of the few common complaints among owners of the Toyota Prius model NHW20 (2004-2009 model years) has been an ergonomic one: inadequate legroom and thigh support for tall drivers. I am 6’4”, an owner of a 2005 Prius for 3½ years. I have considered driver’s seat comfort only fair for extended highway driving. I keep the seat as far back as possible, which provides adequate clearance between the dash and my knees. But I can’t stretch my legs as far as I would like, and because my legs remain moderately flexed I end up with insufficient thigh support. An Obus Forme seat support makes things modestly better, but I have often wanted the ability to adjust the angle of the seat bottom or move the seat further backward. (The Toyota Corolla has a simple mechanical seat bottom angle adjustment. Why can’t the Prius?!)

I have considered various aftermarket or home-grown seat modifications described on PriusChat or elsewhere, but cost, installation challenges, or potential safety issues have kept me from acting. When the ExtendMySeat Prius seat extenders were introduced, they seemed like an option worthy of investigation. This review describes my experience with installing and using the extenders. As of this writing, the extenders have been installed for approximately six weeks.

Installation

(The pictures I have here are not of the entire installation; they only call attention to my particular observations. For pictures of the entire process, I will refer readers to the excellent documentation on the manufacturer's web site. )

The extenders look solid and well made. The four bolts that accompany the extenders also appear solid, with the shanks approximately the same diameter as the factory bolts.

Installation instructions are straightforward and easy to understand. The pictures in the hard copy instructions and the video on the product’s web site are quite helpful. As the instructions state, the only tools needed are a 9/16” socket wrench and 9/16” open-end wrench. A 13 mm socket would have been nice to have, but as the instructions suggest, the 9/16” wrenches work on the 13 mm factory bolts.

Front seat removal was easy. The “A” extender (left) was installed first and attached easily. The “B” extender (right) gave a little trouble. The rear edge contacts the carpet (blue arrow), at which point there is a little “give” in the carpet where it is stretched taut across the bottom concave curve of the rear floorboard hump. The factory bolt (red circle) on this end points sideways rather than downward, so moderate sideways pressure on the extender (red arrows) is needed to compress the carpet and push the extender close enough to the bolt hole to thread the bolt. Between the angle and the small surface available to apply pressure on the extender, I found this a little awkward to do by myself and I made several attempts before getting the bolt threaded. A second pair of hands would have been helpful.




After placing the seat and trying to align the seat rail bolt holes with those on the extenders, I encountered another small problem: the front bolt holes didn’t align precisely. I attached the left front first and then found the right front offset as shown here:




I tried to manhandle the seat to bring it into alignment with no success. I considered the possibility that the rear seat rails weren’t seating properly against the extenders, so I unscrewed the left front bolt and attached both rear bolts. The fronts still didn’t line up perfectly. (The picture actually was taken after the rears and left front were attached.) I manhandled it some more and finally got it aligned enough to thread the bolts. Some assistance here again would have been helpful, though I suppose there could be a small design flaw. I am interested in hearing others’ experiences with this.

All bolts were tightened and electrical connections reattached. I replaced the rear floor mat, removed for installation. This shows the mat in place and covering most of the rearmost part of the right extender.




The mat does not cover the left extender because, as may not be apparent here, the tip of the extender is raised off the floor by an inch or so. I probably could have wedged the mats (both the factory mat and a clear vinyl ExactMat) beneath the right extender, but I wanted the mats to cover it. My only aesthetic complaint is the visible left extender, but that seems unavoidable.

Total installation time was a little less than an hour.

One lingering question I have is the torque values that should be used for the bolts. I would assume Toyota’s torque recommendations can be used, but they are not included in the instructions. I needed strong arm pressure and some leaning into the 10" wrench to loosen the factory bolts, so I tightened them with what I guessed was the rough equivalent. I’d feel more secure about such critical attachment points if I had correct torque values.

Driving Impressions

Simply put, the extenders accomplish their mission. I now have substantially more legroom of course, and I can extend my legs enough for the seat to mostly support my thighs. (I say “mostly” instead of “completely” only because my thighs extend beyond the seat.)

Only problem now is that I need longer arms! With the seat in the rearmost position I have to lean forward to get to the EV button or the MFD. That’s a small price to pay, and it’s easily compensated for by moving the seat up an inch or two. That’s still substantially better than before and I can now choose from several different seat positions. I've found myself leaving it a little further forward early in my drives as I frequently activate EV mode and then move it back a notch or two after the car reaches S3/S4 operating temperatures. On longer trips I’m sure I’ll be making occasional adjustments to reposition my legs. It’s nice to have that option now.

I've needed to adjust my arm position while holding the steering wheel. I typical hold the wheel at the 10 and 2 o’clock positions. Still wanting to rest my elbows on the console and door armrests brings my hands down to the 4 and 8 o’clock positions, something that I still am getting used to. I’ve never given much thought to a telescoping steering wheel, but it would be nice to have one now.

I activate the window switches by feel, and early on I found myself adjusting the rear windows by mistake instead of the fronts a couple of times. I have since adjusted for that.

The real test will be an extended highway trip. I have found previously that I need to stop every hour or two to stretch my legs while on the open road. I have done a couple of relatively short (1 hour) trips since installation, but I have no long highway trips (two hours-plus) planned until late September. I will update this review then.

With both tall and short people driving a particular car, there is a concern about whether the short ones still can drive it with the extenders installed. My fiancée is 5’1”. She doesn’t drive the car, but after installation I had her sit in it with the seat all the way forward. She had no problem reaching the pedals, and she and others of similar height or leg length should have no problem driving it.

A potential safety issue for some is whether the extenders move the driver back far enough to compromise the effectiveness of side air bags. I can’t evaluate that, but given that I don’t have side air bags, it’s not an issue for me.

[Boo]

Many thanks Jimbo for your extensive and helpful review.

[sorka]

No offense, but what good is a seat extender since the steering wheel can't come out far enough with the seat back as far as it goes in stock form? I'm 6' 5" and can't put the seat all the way back because the steering wheel is too far away for proper reach.

When is someone going to machine a splined steering wheel extender????

[Boo]

Originally Posted by sorka

No offense, but what good is a seat extender since the steering wheel can't come out far enough with the seat back as far as it goes in stock form? I'm 6' 5" and can't put the seat all the way back because the steering wheel is too far away for proper reach.

As you probably know, the two (seat back and steering wheel positions) do not necessarily directly correspond. People of the same height are not all built the same.

I know someone 5'4" tall who likes to drive the Gen II Prius with the seat all the way back. I also know 6' plus PriusChatters (nyprius, cycledrum, hill, [jimbok], et al) who have said that they enjoy the driving position with the seat modified and extended 2.5" to 4" further back than stock.

[Boo]

Intentionally deleted (duplicate post because of PriusChat timeout).

[griffycprius]

In case anyone else is wondering about the distance to the steering wheel once you place your seat to a normal upright position if you are taller and move the seat back 2-4" the reach is the same.

You can purchase these online at the PriusChat.com store.

PriusChat Shop : Toyota Prius Drivers Seat Extension - ExtendMySeat [ExtendMySeat] - $195.00

[cycledrum]

Originally Posted by sorka

No offense, but what good is a seat extender since the steering wheel can't come out far enough with the seat back as far as it goes in stock form? I'm 6' 5" and can't put the seat all the way back because the steering wheel is too far away for proper reach.

When is someone going to machine a splined steering wheel extender????

I haven't read everything in this thread, but I can respond to your question.

As you move the seat bottom back, you can compensate for steering wheel by moving seatback forward. And as knees go down by moving seat back, can lower the steering wheel. This has worked for me.

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Long story - As a 6'2.5" dude, I had the stock seat shoved all the way back and reclined the seatback for more headroom and to get down so could see traffic lights. Then the legroom blues kicked in after couple months of ownership.

After I extended the seat travel (just before these brackets came on market, darn!), it took a few weeks for me to start moving the seatback forward. I know the seatback position is correct when the headrest is 'right there' behind my head, but not pushing into it.

I am the full 2 5/8" back now, and my seatback is forward maybe 2 or 3 clicks from stock position, I lost track.

The key here is the rear of the seat must not raise up at all when extended or relocated back, etc.... the rails are slightly sloped downward, so as the seat is slid back farther, it 'buys' a tall person a wee bit more headroom so they can put the seatback forward to keep a reasonable reach to the steering wheel.

A telescopic wheel would be hot, but I'd sooner buy another car than try to make that happen.

[JimboK]

Originally Posted by griffycprius

In case anyone else is wondering about the distance to the steering wheel once you place your seat to a normal upright position if you are taller and move the seat back 2-4" the reach is the same.

It's an excellent point that I failed to address in the review that, yes, adjusting the seat back to a more vertical position can help offset the greater distance from the steering wheel. During a recent hour-long road trip I made occasional adjustments not only with the seat rails, as suggested in the review, but also to the seat back. Part of this still is experimentation to see if there is any one best combination of adjustments, but part also is allowing me to move my legs in ways impossible to do before installation.

I can see how drivers with longer legs (and a larger girth) than I might have to exaggerate the incline of the seat back. I've not needed to do that and it's not comfortable for my back to have the seat back in its most vertical position (irrespective of the extenders). So adjusting the seat back doesn't make as much of a difference for me as it could for some -- hence, I have to adjust how I hold the steering wheel.

But let me emphasize again that that is a minor issue. The added legroom is well worth the tradeoff.

[Tripod137]

Anybody find out about how the extra room effects the steering wheel airbag. Old threads about "home made" rails always metioned something about the air bag sensor in/under the seat that adjusted the steering wheel airbag deployment based on how far the seat was from the wheel. Some mentioned the need to move the sensor so that it maintained the correct distance from wheel. Is this no longer an issue? Has this not been addressed?

Any info?

(btw...my wife and I could really use these rails (6'1" and 6'0")...but I don't want to make things "worse" by adding the rails)

[hill]

I think jimbo & I did these reviews ... what ... around July 19th? ... sorry for the delay. I sent my review to the manufacturer ~ here's a copy for the rest of you folks:

As for side curtain airbag effects, whether or not the air bags are made inoperable (I'm thinking that's tripod's concern) turns on how the extension/mods are done. The extendmyseat mod won't cripple the curtain air bags. The only effect of installing the extendmyseat mod is that your head/torso are farther back ... just as if you'd tilted your seat back to get more length. JimboK touched on that a bit in HIS review.