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Seat Movement While Driving

 
Old 01-14-2015, 08:58 AM
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wanna911
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Default Seat Movement While Driving

How much should your seat deflect while you are driving? I mounted a gopro behind my seat instead of beside for the first time and notice the seat was moving around a bit, not a lot, but a couple of inches either direction under load. Is this normal?
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Old 01-14-2015, 09:03 AM
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YEs pretty normal. It is more apparent on video than in the car.
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Old 01-14-2015, 09:53 AM
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Strict adherence to the new PCA CCR should mitigate this.

You'll note that the rules want you to weld (it's OK, just do it yourself), drill (don't worry where) and bolt (use the bigguns) in the general vicinity of the seat brackets (again, don't worry where, just giterdone).

Once you do all of that, merely purchase sliders which "look" like they may be sound enough to do the job.

While you're at it, do the same for your passenger seat - this way you should be good to go in the alphabet classes also.
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Old 01-14-2015, 01:51 PM
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Originally Posted by KaiB View Post
Strict adherence to the new PCA CCR should mitigate this.

You'll note that the rules want you to weld (it's OK, just do it yourself), drill (don't worry where) and bolt (use the bigguns) in the general vicinity of the seat brackets (again, don't worry where, just giterdone).

Once you do all of that, merely purchase sliders which "look" like they may be sound enough to do the job.

While you're at it, do the same for your passenger seat - this way you should be good to go in the alphabet classes also.
yes and your seat will still deflect going around corners to a certain extent.
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Old 01-15-2015, 11:58 AM
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You wanna see seat movement? I remember thinking "holy crap does Leh's seat move around a lot" when I saw this video. (btw, notice the full opposite lock save at T5!!!)

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Old 01-15-2015, 12:51 PM
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Originally Posted by naroescape View Post
You wanna see seat movement? I remember thinking "holy crap does Leh's seat move around a lot" when I saw this video. (btw, notice the full opposite lock save at T5!!!)

such a great sound to hear the sequential!

not opposite lock, just a 180 .... notice how it came back nicely.... hand over hand (shufflesteering would have made that a tank slapper with most of the guys discussing that on this forum! )

noticed he ran out of RPM on the main straight.... that sucks hanging on the rev limiter there.. probably cost him another second for that.. and still a 1:21

anyway, there is nothing good about that seat moving around. containment seats are not required to have seat back braces in most orgs..... but they need them for this obvious reason.
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Old 01-15-2015, 01:42 PM
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Originally Posted by mark kibort View Post
containment seats are not required to have seat back braces in most orgs..... but they need them for this obvious reason.
Really?

You make that statement as though the FIA standard seats are homologated with back braces.
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Old 01-16-2015, 06:30 AM
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I posted a video here once, and some guys responded with "wow your seat moves a lot dude, that's not normal!"

So as a good citizen I checked the car and indeed, one of the mounting points on the floor was detached, hence the extra movement. Never noticed it while driving. Took some welding to get it fixed (until one month later the opposite side did exactly the same ... more welding to the rescue).

So check your mounting points on the floor of the car. If all is fine there and you use decent seat rails / seats (and not some Chinese knock-offs) I wouldn't worry about it.
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Old 01-16-2015, 08:28 AM
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Originally Posted by KaiB View Post
Strict adherence to the new PCA CCR should mitigate this.

You'll note that the rules want you to weld (it's OK, just do it yourself), drill (don't worry where) and bolt (use the bigguns) in the general vicinity of the seat brackets (again, don't worry where, just giterdone).

Once you do all of that, merely purchase sliders which "look" like they may be sound enough to do the job.

While you're at it, do the same for your passenger seat - this way you should be good to go in the alphabet classes also.


Well played...
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Old 01-16-2015, 09:11 AM
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Originally Posted by ir_fuel View Post
I posted a video here once, and some guys responded with "wow your seat moves a lot dude, that's not normal!"

So as a good citizen I checked the car and indeed, one of the mounting points on the floor was detached, hence the extra movement. Never noticed it while driving. Took some welding to get it fixed (until one month later the opposite side did exactly the same ... more welding to the rescue).

So check your mounting points on the floor of the car. If all is fine there and you use decent seat rails / seats (and not some Chinese knock-offs) I wouldn't worry about it.
+1,000! Found this once at Sebring during a routine check. Could have been bad if there had been contact. Without firm support, the seat moves too much, not keeping the harnesses tight. It's not the hit that hurts you, it's the sudden stop, made worse when you can accelerate BEFORE that sudden stop due to loose seat/belts...
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Old 01-16-2015, 02:51 PM
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Safety equipment is designed to mitigate fatal G-force peaks by flexing a bit in order to spread de-accellerative forces over a longer period of time.

Even PCA has recognized this by recommending a high-density foam crush area between an FIA seat and a hard seat brace.

But it is good practice to bolt your seat into the car properly.
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Old 01-16-2015, 03:12 PM
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Originally Posted by JCP911S View Post
But it is good practice to bolt your seat into the car properly.
I think this is the first step and not often enough done.

On your point about designed energy absorption, more than two decades ago, I backed into a Jersey barrier in Charlotte in a very quick 934/5. The base of the seat fractured, absorbing the shock. If there had been a post or firm attachment preventing that "give," I'd have been hurt more than just heavily shaken around!
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Old 01-16-2015, 03:28 PM
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You backed WHAT into a barrier????
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Old 01-16-2015, 03:37 PM
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WOW indeed!!!

Thanks to Chris Crisco, those Jersey Barriers are worth a fortune!!!!
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Old 01-16-2015, 04:22 PM
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Not pleasant. It was damp and I was cocky. The girder placed under the rear bumper cover prevented almost all the damage. Rung my bell, though. Proved to me beyond the shadow of a doubt, the value of composite seats and good safety equipment...
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