emptnest

The next upgrade to my C4 track car will be 5 or 6 point harnesses. I currently use only the stock 3 point belts. I have a harness bar installed which currently serves only to stiffen the car and act as a camera mount.

My seats are stock sports seats. They fit me like a glove, and hold me very firmly on track. For that reason, I am not inclined to replace the seats.

I have found a bezel system that will allow me to cut, trim, and finish proper openings through the seat backs for the proposed harnesses. However, this kit will only perform aesthetically, and will not provide any structural strength at the openings in the seat back.

Plus there is the issue of normal rotation, which allows the stock seat backs to pivot forward slightly (about 4 inches or so).

Will the harness bar and 5-6 point harness provide enough restraint that the natural pivot of the stock seat back is not a concern? Or is the stock seat so inherently unsafe that a true rigid racing seat is the only advisable option?

mnmthoele

I wouldn't go the route you are talking about. You will always have the possibility of the seat collapsing backwards. There is a reason that certified race seats do not fold.
As far as cutting your seats to put slots for seat belts to pass through, I think that would just weaken the seat back. Also I do not know which generation sport seats you have, but I have an '88 with sport seats. I am not a very big person, and I don't believe there is enough room to comfortably fit harness slots in the back. And do not put shoulder harnesses on over the outside of the seats' they will not stay put.
You would also have to cut a slot in the seat cushion to get the crotch belt where it should be located.
If you are going to upgrade to true harnesses, also upgrade the seats. It is not cheap, but is well worth it.

jaa1992

Use a real racing seat. those kits are for show, not support!
They will at least hurt you real bad in a crash, at worse kill you.

Lots of good seat options out there.

C5 Hardtop

The angles of your harness belts are critical, but I'm confused about how there would be an issue with the seat itself. What would be changing to the stock seat that would make it unsafe?

rithsleeper

I wanted to do exactly what you are describing and started to do it. Then I decided to get an omp seat used. I made a mount out of square aluminum tubing and no welding just bolts. I can change it out in about 5 min tops. I used to think my old seats held me well, but as soon as I moved to racing slicks and sat in the omp I realized how much energy I was expending. I will say a lot of people say that belts mounted through center are dangerous but I wouldn't say that (unless they go on sides of shoulders and slip off ) however I would say that they are no safer than a 3 point. I would want the proper 5/6 point safety.

Go full racing seats and you won't regret it. I recommend to all my students the first thing they should get before any upgrades are proper seats and seat time. Makes such a difference.

jaa1992

The seat is not designed to handle the extra stress where you cut the holes. If you have a tall torso the holes are in the wrong place. Short torso you have a 50/50 chance of them being in the right place.
The seat back will twist in a crash and will cause a seat back failure.

Shall I go on?

Do you really want to trust it with an impact at 150mph??

C5 Hardtop

Yes, please go on. Spend lots of time on a lengthy and detailed explanation having a summary with bullet points, facts, figures and footnotes

SouthernSon

The rules for the many different sanctioned racing venues can be very helpful in ascertaining the correct ways to install and maintain racing equipment. You might check SCCA, NASA or even the less renowned organizations such as CHUMP and WRLA. Good information to be found in the rules of all of these series.

fatbillybob

Modern theory is use any harness means you must use a HANS or similar head and neck restraint. HNR comes in 2 flavors SFI38.1 or FIA certified. SFI38.1 devices must be recertified every "x" years. FIA devices do not expire but leave it to you to routinely change the tethers like every "x" years. Some devices have both certs.

Seats come Full containment, containment, and old school. Full containment hold the body in more directions. A crash is usually not just x-y but diagonal and with secondary impact. Containment seats typically have old school features with a head halo. They provide less containment. Old School seats have some hip and side and shoulder bolstering and a "layback" and dedicated harness holes, all part of critical safety features. The only plastic seats that should be considered are FIA 5 yr seats or FIA 10 yr seats, or metal seats. I would not use any other plastic seats because they are not FIA tested meeting certain crash specs. FIA 10 yr seats least 10 years and most have integral back braces and many have head halos. Metal seats must be supported or they will fold in a crash. Do not use any metal seat supported only by the base. A metal seat should be supported by a minimum of 6-8 places bolted to a load spreading back brace usually part of the cage. The advantage of a FIA seat is that it does not have to be used with a cage. There are no harness bars that support seats. There are back braes that can hook to harness bars but I think they are dangerous not spreading the load over much needed surface area. Some look like a pole pointing at your spine. That's why if you use a back brace IMO it should only be used with an FIA 10yr or metal seat designed for use with back braces. No FIA 5 yr seat is designed to be used with a back brace. Any not expired FIA seat can also be used with a slider. A metal seat cannot be used with a slider because you can't support the seat back. Use caution when buying used seats. You have no idea if they have been in a crash or left out in the elements which degrade composites.

Good for you to think about upgrading your safety. A seat is the cornerstone of a well thought out safety system. Remember that safety is a system and there are many parts. You need to learn about things I have posted here and other things like 5pt vs. 6 pt belts, different belt certifications, hybrid cams, latch links, pelvis control, why use HNR with modern harnesses, double shear belt anchors and submarine strap departure angles to name a few. If you don't want to learn it use a trusted race shop to build you a safe car. Hope that helps.

blackozvet

here is how i set my c4 up with harness and stock seat using the harness bar.

Charley Hoyt

No offense intended... Don't do this. You would be safer with a 3 pt seatbelt. The seat belts in this picture are too far apart to safely use a HANS device and you should really use a HANS if you have a 5 or 6 point harness.

Charley

blackozvet

No offense intended, I would not be safer with a 3 pt seatbelt.

The S.A.E. conducted crash testing using cadavers to compare 3 pt seatbelt to 4 point harness, in all crash testing less injuries were received by (the already dead) bodies.
They just fitted 4 point harnesses into sedans fitted with a seatbelt and stock seats.
here is a link to the conclusion (you have to pay for the access to the full results)
http://papers.sae.org/2003-22-0017/

I run in street registered class, we are not allowed to have roll cages and therefore no hans device is allowed unless running a full cage. We can run 3 pt / 4 point or 5/6 point with a suitable seat.
I believe a lot of Organisations use the 'no roll cage no hans device' rule.

I have run this 4 point and harness bar for 2 seasons, and it straps me into the seat far better than the seat belt does. My mrs. drove my car last sunday at hillclimb, she used the seatbelt for the first half of the day and the harness for the second half, she sd the harness was FAR better than the seatbelt.

The OP has a c4 and is asking about using a harness with the stock seats, my contribution to the discussion is a photo on how it can be done.

I know its risky wading into a harness/seat discussion as you get the usual "you must have a full cage, race seat, 6 point harness and hans device or you will die" but there are people who are just starting out on the modifications trail and slowly transitioning their road based car into a track car and doing the mods as time and money, and the controlling organisation, allow.

rfn026

You want to keep in mind that if your seat breaks up in a crash all of your belts are useless.

If you're serious you'll want an FIA approved seat.



Here's an article I did couple of years back on seats. The information is still good.

Richard Newton

fatbillybob

Yes but we know 4pt harness that is not ASM is bad. You skip 4pts and go right to 5 or 6 once you leave street 3pts. There would be very different results if testing 3pt vs. 5/6. In 2016 there is no reason to not do 6pt if you can install 4pt because you can install the 6pt parachute style.

If your class allows 3/4/5/6 pt then the only way to add 4+pts properly is to use a "harness bar" Typically those are installed between shoulder seatbelt anchors. That means a HANS or other HNR can be used and should be used. In the old days there was less basilar skull fracture because belts were made of nylon and had greater stretch. Only the cheapest of the cheap are made of nylon anymore. In fact I can't think of any. Belts today are often polyester with very little stretch. Retention is the rule of the day. That means modern belts use HNR. Also. cars are faster and impacts can be greater. In the 80's a vette had 250hp, 90's 350hp, mid 2000's 500hp. Dorces on your body are increasing as are safety concepts. I would check your rules. I would be very surprised if HNR is not allowed. If so I would run with someone else.

SouthernSon

You got that right!

Charley Hoyt

No offense taken. You are welcome to your opinion. It is your car, your money, and your life. We all evaluate the risks of track driving and have different tolerance levels of what is acceptable. I don't know who told you that you need to have a roll cage to use a Hans because it is just not true. I have no doubt that the harness holds you in place better than the three point harness, but that doesn't make it safer. The article you posted was so high level that it really didn't have much value. The facts are that factory seat belts are engineered with tear strips that slow your movement forward so That you have a reduced velocity when you hit the airbag. They are designed to work together. Racing harnesses do not stretch much so your body is held in place but your head ,with the added weight of the helmet, continues to move forward. According to the testing that HANS did there is enough force in a 40 mph crash to cause a fatal basil fracture. So if you are comfortable taking that risk, go ahead... I wish you the best of luck. For driving a harness is great because it holds you in the seat so well... But being held in the seat so firmly is also why a crash with a harnes can be fatal with out a Hans.

Charley

rfn026

Pay attention to what Charley just said.

Years ago I was doing some work with the folks at Schroth. I was going to install their belts in my C4. They wouldn't sell (or give me) any belts. The said that using a 5-point system with stock Corvette seats was simply too dangerous.

They felt the shoulder belts would slide off in an accident.

My feeling now is that if you're going to keep the stock seats in place then the stock belts work just fine in an accident.

I have used a lap belt on some cars with the stock belts. The lap belt was only to hold me in place. I never thought of it as a safety item.

You have to think about the total system. Adding things randomly will not improve your safety. Stock seats with a 4-point belt system won't make you safer. It might actually make your car less safe.

As Charley pointed out being held securely in the seat as you drive and being safe in an accident are two very different things.

Richard Newton
Is Your Garage on Fire?

Bill32

Charlie's right.

In fact, if I saw that setup in my Tech Inspection line, I doubt if I would issue a Tech Sticker to go out on the track.

fatbillybob

Crashes also not 1 dimensional. A lateral hit with those belts with nonretentive stock seat = belt dumping.

Captain Buddha

Get a full containment racing seat, proper harnesses, proper installation, a head-neck restraint and go play! I "put" my car into the wall a few weeks ago...sideways (lateral hit)...that RaceTech seat did it's job...as did the Schroth harnesses, etc....sure I was a little sore but that was it. I walked away. Would it have been different with lesser equipment? I'm not going to find out.