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Do You Ever Replace Your Seat Bolts?....

 
Old 08-01-2010, 10:40 AM
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jrgordonsenior
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Default Do You Ever Replace Your Seat Bolts?....

Yesterday at Cal Speedway a full race 930 got T-boned in the driver's side turning into the infield (T3) off the banking. A 996 overcooked the turn and broadsided the 930 breaking off 2 of the drivers seat bolts. Consequently he hit his head hard on the roll bar above and was transferred to the local hospital for a CAT scan and observation. Thankfully he's OK, and was released late last night.

So we got to discussing the bolts that sheard over a glass or 2 last night. Should they be a maintainance item that you perodically replace? Has anyone ever heard or seen a TSB
for replacing seat bolts? I think I'll be ordering some come Monday morning.....
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Old 08-01-2010, 10:47 AM
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i haven't.
but i will do so every year now.
cheap insurance, why chance it.
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Old 08-01-2010, 11:09 AM
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do you know what grade bolts he was using?
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Old 08-01-2010, 11:20 AM
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Originally Posted by DanR View Post
do you know what grade bolts he was using?
I don't but that's a great question. I assume they're sourced only from Porsche. They're not very thick, maybe 1/4 or 5/16 of an inch, and they tighen as they go in....
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Old 08-01-2010, 11:27 AM
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and size? The stock bolts I have seen are tiny. I went to 1/2" grade 8.
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Old 08-01-2010, 11:29 AM
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The bolts will fatigue from tensile loading and unloading but if bolts failured in shear new ones may not make much difference unless old ones have been damaged by being loose. Someone should send the failed parts to a metalurgical lab for inspection.
Phil
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Old 08-01-2010, 12:06 PM
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It's a relief hearing the driver is OK.

I don't think a seat bolt should be any less than a 12.9. I suspect on impact the bolts are under tremendous load.

I think the belts are more suspect and should be checked because they would have had to stretch a lot for the driver to hit his head. (4" is normal I think but the old cars don't have much room) They pass through the seat and are bolted to a different location. Maybe the seat should be lower to compensate.
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Old 08-01-2010, 12:32 PM
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I replace mine every time I exchange the seats and use the Porsche OE bolts. Non OE bolts are easily sourced at a hardware store but I question their tensile strength. It costs just a few bucks every time it's done, a small price to pay for safety.
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Old 08-01-2010, 01:32 PM
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A seat bolt with fail in one of 3 ways. Faituge due to crack initiaion. Overload, or the seat mount in the chassis will fail.

I would guess the bold failed in overload. In that case a new bolt would not have done anything to help. If the seat mounts in chassis failed a new bolt would not have done anything. If the bolt failed from fatiuge induced crack than replacing the bolt would have helped. However bolts are not loaded such that they are subject to fatigue. That normal torque applied loads the bolts more than the person in the seat will. As such there is not crossover point to induce Low Cycle Fatigue.

So changes are high that "old bolts" were not that cause. Unless of course these bolts were damaged in some way.
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Old 08-01-2010, 02:15 PM
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A full race car using street car mounting hardware? Not a good combination. I check all my seat and belt hardware before each event.
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Old 08-01-2010, 02:25 PM
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Originally Posted by M758 View Post
A seat bolt with fail in one of 3 ways. Faituge due to crack initiaion. Overload, or the seat mount in the chassis will fail.

I would guess the bold failed in overload. In that case a new bolt would not have done anything to help. If the seat mounts in chassis failed a new bolt would not have done anything. If the bolt failed from fatigue induced crack than replacing the bolt would have helped. However bolts are not loaded such that they are subject to fatigue. That normal torque applied loads the bolts more than the person in the seat will. As such there is not crossover point to induce Low Cycle Fatigue.

So changes are high that "old bolts" were not that cause. Unless of course these bolts were damaged in some way.
+1

Makes sense to replace the hardware with new when you are replacing seats or belts, but replacing undamaged properly torqued seat bolts every year won't make your car any safer. Don't give the SFI any new ideas
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Old 08-01-2010, 03:58 PM
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Smile Might be time to consider Kirkey...

Check out their seat mounting:
http://www.kirkeyracing.com/index.ph...wh=30&pn=99200

Their Club Racer seat look pretty good to me,,,,

Then of course there is The Joie of Seating NASCAR seats......can't post their seat specs...just Google NASCAR Racing Seats..Joie will be one of the top hits.

Last edited by Martin S.; 08-01-2010 at 04:14 PM.
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Old 08-01-2010, 04:02 PM
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Does anyone know the DIN spec for the OE bolts? Ages ago I tried to locate it but was unsuccessful.
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Old 08-01-2010, 04:24 PM
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Sean F
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Originally Posted by MUSSBERGER View Post
A full race car using street car mounting hardware? Not a good combination. I check all my seat and belt hardware before each event.
+1

don't use the OEM hardware or the original seat rails in a race car. 4 small bolts into 18 gauge sheet metal is a bad combo. build a new structure between the sill and the tunnel just above the floor boards and add additional fasteners.
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Old 08-02-2010, 08:30 AM
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Originally Posted by Sean F View Post
+1

don't use the OEM hardware or the original seat rails in a race car. 4 small bolts into 18 gauge sheet metal is a bad combo. build a new structure between the sill and the tunnel just above the floor boards and add additional fasteners.
spot on. Asking a street setup to do a track job. Big strong 5 or 6 point belts all well bolted holding a driver in a seat bolted to folded and formed sheet metal. A reasonable hit will exert more energy into the seat base than is needed to lift the car. If you don't think you could crane the car by the seat mount it could stand to be improved. Once the seat comes loose the rest of the safety systems are all compromised.
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