BMW M3 Forum (E90 E92) - View Single Post

Richbot · 02-06-2012, 08:17 AM

If the goal is staying put in the seat, www.cg-lock.com spend $60 or whatever and use the stock belts, and get a racing bucket that works with the OEM belts if you still don't feel like you're held in place. After that it's time for monkey barz. What Richard said is absolutely true. You can probably go with a lot of the compromised solutions out there for getting a harness in the car, and you might be ok even in a crash, but it's not that much harder to go all the way and do it right. In the end only you can decide what balance of risk and hassle you're willing to deal with.

There are plenty of people who won't agree with what I have to say, so take some of what I'm about to say with a grain of salt, but I've crashed enough and seen enough bad outcomes to know you don't screw around with this stuff.

You can go one of two ways, either use the OEM safety systems with some slight enhancements, or go all the way with racing-style safety gear. In my opinion, there is very little in-between here, both approaches are designed to work as a system and you can't pick one part here and one there and expect a good outcome, even though many have lived to tell about it. Safety gear used improperly is sometimes more dangerous than none at all.

I think it's safe to say that mounting a lap belt to the seat mounting bracket is a bad idea, though I'm sure many have lived through it just fine.

The sub strap is for travel limiting, it is not designed or intended to do anything more than hold you in the correct orientation so the lap and shoulder straps can do their jobs. The lap belt and shoulder harnesses do the majority of the work in a crash. A less robust mounting for the sub straps, or even piggybacking on the lap belt mount, is usually fine.Even the sub strap should still be anchored separately from the seat though. The seat moves a lot more than you'd expect in a crash and you want the belts to be independent from the seat so that you don't lose tension when the seat moves.

Those b-pillar bars should really only be used to keep the harnesses in the right place for low-speed stuff like autocross, in my opinion there is too great a span and everything I've seen bolts in and is made of 1" tubing or smaller, which isn't crashworthy at all. The loads on a shoulder harness in a 10+g crash are huge.

If the goal is safety, you have to think about what's going to happen when you're taking the car off a sweet jump and doing a backflip, not just what works to get the thing in the car and mounted. Once you go start thinking along those lines, logic dictates you need to do at least a half cage and a racing bucket to provide roll support and a solid foundation for the harnesses to work from.

02-06-2012, 08:17 AM	#9
Richbot Major General 2759 Rep 5,483 Posts Drives: Jerez Black E90 Join Date: Sep 2007 Location: STL iTrader: (5)	If the goal is staying put in the seat, www.cg-lock.com spend $60 or whatever and use the stock belts, and get a racing bucket that works with the OEM belts if you still don't feel like you're held in place. After that it's time for monkey barz. What Richard said is absolutely true. You can probably go with a lot of the compromised solutions out there for getting a harness in the car, and you might be ok even in a crash, but it's not that much harder to go all the way and do it right. In the end only you can decide what balance of risk and hassle you're willing to deal with. There are plenty of people who won't agree with what I have to say, so take some of what I'm about to say with a grain of salt, but I've crashed enough and seen enough bad outcomes to know you don't screw around with this stuff. You can go one of two ways, either use the OEM safety systems with some slight enhancements, or go all the way with racing-style safety gear. In my opinion, there is very little in-between here, both approaches are designed to work as a system and you can't pick one part here and one there and expect a good outcome, even though many have lived to tell about it. Safety gear used improperly is sometimes more dangerous than none at all. I think it's safe to say that mounting a lap belt to the seat mounting bracket is a bad idea, though I'm sure many have lived through it just fine. The sub strap is for travel limiting, it is not designed or intended to do anything more than hold you in the correct orientation so the lap and shoulder straps can do their jobs. The lap belt and shoulder harnesses do the majority of the work in a crash. A less robust mounting for the sub straps, or even piggybacking on the lap belt mount, is usually fine.Even the sub strap should still be anchored separately from the seat though. The seat moves a lot more than you'd expect in a crash and you want the belts to be independent from the seat so that you don't lose tension when the seat moves. Those b-pillar bars should really only be used to keep the harnesses in the right place for low-speed stuff like autocross, in my opinion there is too great a span and everything I've seen bolts in and is made of 1" tubing or smaller, which isn't crashworthy at all. The loads on a shoulder harness in a 10+g crash are huge. If the goal is safety, you have to think about what's going to happen when you're taking the car off a sweet jump and doing a backflip, not just what works to get the thing in the car and mounted. Once you go start thinking along those lines, logic dictates you need to do at least a half cage and a racing bucket to provide roll support and a solid foundation for the harnesses to work from. __________________ Last edited by Richbot; 02-06-2012 at 08:50 AM..
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