Front seat modification. Increase thigh support.

[PetersRedYaris]

Want to add some extra thigh support to your front seats? Here’s what I did.

Note: I’m not going to give you a step by step DIY as I don’t want to insult your intelligence. I think it’s straight forward enough.

Go to your local hardware store and pick up some metal washers, and longer bolts. The amount of washers depends on their thickness as you can make the spacer anywhere from zero to 5/8 inch thick. The bolts are a M10 x 1.25 thread. 1.5 pitch is the common thread for an M10 bolt so finding a 1.25 thread may take a few stops. I used a 2 inch stainless steel class 8.8 bolt. Class 8.8 SS is about the equivalent of a grade 5. I also found some plastic caps that fit the stainless bolt heads to make them not so bright and noticeable. (Not that they were ugly, just bright…)

http://i227.photobucket.com/albums/dd181/peter0022/DSC01830.jpg

Wrap your stack of washers with electrical tape as the sides will be visible after they are installed. I know I show a nylon spacer instead of washers, but the nylon spacer cracked and this DIY now recommends metal spacers (AKA- washers).

http://i227.photobucket.com/albums/dd181/peter0022/DSC01832.jpg

The “centering pin” for the seats will need to be bent back about ¼ inch to allow the bolts to stay centered in the holes as the seat is tilted back. I also say that the max spacer thickness is 5/8 inch because any greater and you will need to “ovalize” the holes with a round file to get the bolts to thread in cleanly.

http://i227.photobucket.com/albums/dd181/peter0022/DSC01833.jpg

Finish is relatively clean and unnoticeable.

http://i227.photobucket.com/albums/dd181/peter0022/DSC01834.jpg

http://i227.photobucket.com/albums/dd181/peter0022/DSC01835.jpg

This mod works well for tall drivers. This is because, if you have the seat all the way back, the seat is extended past the rear mounts, thus by raising the front you actually lower the back of the seat base.

Caution: I take no responsibility for you altering the seat mounting system in your car. As always, use common sense and don't be a fool.

[Reddog99]

Nice write-up. I've done a similar mod (3/4" high) and highly recommend it if you're unsatisfied with the stock seat position. You appear to be using an grade 8.8 (strength rating) bolt. For safety, you should use the same as stock uses, grade 10.9.

[PetersRedYaris]

No, it.s not a grade 8.8 because it's metric and they use a different grading scale. Stainless is about the equivilent of a grade 5, and grade 5 is plenty strong. In the event of a crash, the threaded inserts would rip out of the floor before a M10 bolt would snap. Plus, there are four bolts holding the seat in place. Don't forget, higher grades of steel are stronger but also more brittle. I have seen grade 5 bolts bend but still hold while a grade 8 has snapped clean off. Basically, just don't use some crap non high grade steel bolts.

Lastly, if your concerned about safety, you can get about 1/4 inch rise and still use the factory bolts. Just make sure you have about 7 full turns of thread contact when you put the bolt back in.

[Reddog99]

First off, "8.8" IS a metric strength rating. See this site for more info: http://www.roymech.co.uk/Useful_Tables/Screws/Strength.htm

Secondly, M10 is a metric SIZE, not a strength rating.

[PetersRedYaris]

First off, "8.8" IS a metric strength rating. See this site for more info: http://www.roymech.co.uk/Useful_Tables/Screws/Strength.htm

Secondly, M10 is a metric SIZE, not a strength rating.

I am aware M10 is the size. I am also aware that 8.8 is a strength rating, but it is a class, NOT a grade. Like I said, they are measured differently. US bolts are measured in grade and metric bolts in Class. A class 8.8 bolt is NOT the same as a grade 8. See here-

http://www.boltdepot.com/fastener-information/Materials-and-Grades/Bolt-Grade-Chart.aspx

[...]your first post says the stock bolts are a grade 10.9, which is NOT correct. Again, it's a class 10.9. You can figure out the strength comparissons yourself, just remember US (grade) bolts measure strength in PSI, while Metric bolts (class) use MPa. Heres the conversion- 1MPa = 1N/mm2 = 0.2248 pounds/mm2 And you'll need to know 1 inch = 25.4mm

Have fun...:biggrin:

PS- I reread my post as can see how you misunderstood me. You do realize however that both class (or grade) and size contribute to a bolts strength. I meant that an M10 bolt is huge, and there are 4 of them holding the seat in place. So long as you don't use a low carbon bolt, they will NEVER break. In a major accident, the seat will be ripped from the car before the bolts snap...

[PetersRedYaris]

Here, I'll make it easy for you. Here a conversion calculator-

http://www.chapelsteel.com/mpa-psi.html

If you want to enter the numbers yourself, you will see that my origional post stated that a class 8.8 is about equal to a grade 5, which is correct. A class 10.9 is almost identical to a grade 8.

Now that that's sorted out, If you want to say a grade 5 bolt isn't strong enough for this application, that can be your opinion.

120,000 PSi vs. 150,000PSI, BOTH will hold. And of course people are welcome to find a longer class 10.9 bolt to do this mod if they wish.

[Reddog99]

Over-reaction? Maybe I had too much coffee this morning. :redface:
But I'll stand by my admonition about recommending, in a public forum, lower strength bolts for a safety related item like the seat hold-down bolts. There are a whole lot of people here who might follow that advice. Are you willing to take responsibility if someone got hurt because of it?

And remember, in a front or a rear collision, the major load on the seat would be taken by just two bolts, not four.

The original bolts are 10.9, so it's not my OPINION, it's Toyota's judgment about what is appropriate.

[jonismyname]

i did this yesterday. i like it. if others are considering it- don't be scared. bolts are plenty strong enough. it changes the dynamics of the seat dramatically and ended my shopping for a new seat (for now at least...)

if pull out strength were an issue, a coarser thread (deeper thread) would've been used, and if sheer strength were an issue, a larger diameter bolt would have been used. i used a class 8.8 bolt, and have no regrets.

[yaris-me]

The pin near the bolt hole, does it have a structural function or just a mounting guide?

[Tamago]

The pin near the bolt hole, does it have a structural function or just a mounting guide?

that pin takes a good portion of the load in an accident

and the seat just holds your butt off the ground, it doesn't take any lateral load in a head on collision.

the seatbelt does, however.

[Pitt Yaris]

Good mod. I don't have a problem with the seats, but being 6'0, I think it'd be good to do this mod. I'm definitely doing the passenger seat too since one of my main passengers is 6'2, or 6'3".

[mikenacarato]

im 5'6" and im going to do then when i get home as well, maybe not as high though. hopefully it will give more of a sporty feel.

[YarisSedan]

I did this mod but used the factory bolts and didnt have to bend the pin. Made the seat much more comfortable. I used head bolt washers and just jammed as many as i could fit in there lol. So they look like a oem fitment since they are black and ofcourse they are strong. If anyone is in the bay area and wants some i got a bunch of them still leftover.

[Pitt Yaris]

Yaris sedan, so all you purchased was washers, and used stock bolts/everything else? How much difference did it make?

[YarisSedan]

Seat feels more comfortable. Helps keep your bum from getting store on really long trips and your theighs are more supported. And feels less like you are driving a minivan since you are tiled back a little bit instead of sitting up so high. Best part of it is you can always put it back to factory whenever you want or if you sell the car. without any signs of what you did.

[Pitt Yaris]

Sounds good, I guess I'll have to go out and purchase a pack or two of washers in the next day or two.

[Carson]

I'm 6'4" and I never had any complaints about the yaris but I did this today and it's great. It feels sportier and increases head room. Thanks for the write-up.

[Wayboo]

Thanks for the good info on the seat mod I just bought a Yaris and the seat is not comfortable at all I was looking to replace it for the foam is also to firm I will try your spacer mod and see if that helps and it would be nice if the steering wheel was'nt so ackward to reach,I just joined this Yaris site and look foward to the good ideas ya'll have.

[swidd]

So... am I just weak, or are those bolts near impossible to unscrew? I couldn't do it... When I tried using a drill, the extension part I insert into the drill broke off, and didn't move the Toyota seat screw at all... :cry:

[derickveliz2]

So... am I just weak, or are those bolts near impossible to unscrew? I couldn't do it... When I tried using a drill, the extension part I insert into the drill broke off, and didn't move the Toyota seat screw at all... :cry:

I'm about to take the front seats out, I'll let you know :frown: :frown: :frown:

.

.:eek:

.

[swidd]

Please do. I tried again, with a socket wrench. No success. I'm thinking it may be welded from the bottom or sealed with very permanent lock-tite... Or that going to the gym didn't help my strength...

[cali yaris]

that is a starz bolt. it's on there real tight, but you can get it off, it is not welded.

get a short pipe to increase the torque and use the correct socket for that bolt.

[swidd]

lol, I configured my socket wrench short, and was able to twist the bolt about 1/2 rotation, and then that socket head (actually converter piece) broke too! I bow to the mighty Yaris... Now my whole 40 piece socket wrench kit is useless without that converter piece.

[RedRide]

As somone who has worked for Ford (in assembly) in the '70s, I can testify that seat bolts are given the upmost importance both in strength and torque right up there with seat belt mounting bolts.

I suspect that perhaps loctite is is used to secure them.

[sbergman27]

Or, you can do what I've done on certain cars, and buy a bath towel from Walmart to put under you that you can fold, easily, in various ways, to provide support wherever you need it on a long drive. Works great. And I've never heard anyone seriously question the hardness of Walmart's towel bolts.

[swidd]

Alright, it finally gave in. Brute force!! ... And $5.99 to auto zone.

Just so I'm sure, I can disconnect the wire harness under the seat and remove the seat, and continue driving with the seat removed for a few days without the airbags deploying?

[Wayboo]

Seat mod works great thanks:wink:

[frostbitten]

yup

Seat mod works great thanks:wink:

[Kiteless]

Hey drudging up an oooold DIY thread here. So I get severe leg pain on long drives (3+ hours) because I am 6'2" and I guess I don't really get any support on my right leg. If I lift the seat up in this way so my leg hopefully has a little support and I am not using the muscles on my inner thigh for hours and hours and hoooours to keep my leg in place and work the gas petal, this will hopefully gibe my leg a little more support? Also I think a DIY cruze control would also help since I would not have to mind the gas petal on long drives.

But does anyone else have this particular leg pain or am I just borken? Thanks all.

- Jason

[cali yaris]

^ Lifting the front of the seat with a spacer or washers will help a lot.

[darthmynock]

So, that is why I can't stand long trips 3hrs or +, b/c of the pain on my leg?

Adding this to my to-do list !!

ty
!!

[LugNut]

Just did this mod on the driver's seat. Went with 5/16 inch lift; will see how it goes then decide to raise/lower and if to do the passenger's side.

The bolts I bought were 50 mm long, and seemed too long by about 5 mm but worked. I had to loosen the rear mounting bolts to allow the rails to move a bit (don't loosen more than 1.5 turns, or the chair can't fully slide back and forth while completing this mod.) so that I could get the new bolts started in the front.

All four original bolts were E10 headed Torx(R), and weren't that hard to loosen with a 3/8 inch breaker bar.

[Radvr6t]

Did this and surprisingly noticed the 5/8ths difference!

[JimKellyfan]

I was thinking of putting a small igloo cooler on end and sittin on that.
Not really, I was wanting to sit lower actually. I nearly cannot fit in without bangin my head now, and nearly touch the ceiling where I sit now.
Future mod, no rush.
I had a van once, captain chair install without the riser.
Made you feel like a midget drivin it.
I took my time bolting down the passenger side, and had some fun with my friends for awhile one summer, putting em on their back on take off.
I also had threaded rod as a lock and latch on my driver door.
Those were the days with a rednecked out rat rod van I got for someone owing me 75 bucks and the payoff.

[driverofchuckles]

just did this. took all of 5 min! the difference is AMAZING! it was also my first official "mod" :D i now have mod fever. i want to do it all! my Chuckles (when you're 6'4" and you unfold out of a Yaris it's the usual reaction.) will be epic!

(side note: technically it's Chuckles II as my beloved '93 two door tercel, most basic model out there, was Chuckles I. since this car drives, handles, and feels like that one the name fit)

[YarMatey]

Just picked up the hardware to do this mod. This is my second Yaris and I don’t ever remember having the arse and leg pain for long drives with my first one but I’m happy to have found this mod and hope it helps!

Only reccomendation I can make for other who want to do this mod is to be careful about mixing stainless with other metal types. If moisture is introduced the stainless will react and start to corrode the other metals touching it, which could be a safety concern if it’s the seat track mount.

Great informative write up though! Thanks a bunch!