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Vorshlag Seat Mounting Brackets

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  • Vorshlag Seat Mounting Brackets

    We have talked about the positive benefits as well as mounting challenges for installing fixed back racing seats in this forum post. I won't re-hash that again here, just know that installing a racing seat into a street or race car can be a LOT of work, and we see more of these installed wrong than we do right.

    Installing Sparco racing seats into this Audi R8 - without cutting into the carbon fiber tub - was tricky!

    One of the ugly secrets of the automotive aftermarket is how much work installing a seat can be. When we do a custom seat install it can gobble up at least 3 hours per side, and often up to 8 hours, to do it right. There can be challenges with the shape of the floor, material of the floor, narrow confines of certain cabins, and extreme height constraints.

    Add in the challenges of putting "wide winged" racing seats into a car that still has interior door panels, door glass, and a headliner and it becomes damned near impossible to "buy something" pre-made to help a DIY racer get their new racing seat mounted safely into the car, and placed where his or her body fits properly.

    We have used every major seat bracket supplier over the years and had results that ranged from "fairly poor" to "unbelievably dangerous". Normally we just ask a customer to not bring us this off the shelf garbage and make something from scratch.

    We tried to modify these bracket kits, among others. It is usually easier to start over from scratch

    Now not everyone can bring their car to us or another qualified fab shop for a seat install - although that is always preferred. Shops like our's that have installed 100s of racing seats and that compete in various racing groups know not only the technical standards required, but the engineering reasons and fabrication methods that work in the field. There are other shops that are as meticulous and experienced as we are, of course, but we've seen some "shop installs" of seats that would curl your hair.

    When you absolutely have to do a seat install yourself, the options out there can be pretty sketchy. We show in some videos in this forum thread how much slop that can exist with off the shelf brackets. Of course a slider will always allow some movement, but a fixed mounted seat should not have ANY flex. You should be able to grab the top of the fixed back racing seat, shake it, and move the CAR on the suspension. Any movement relative to the chassis is BAD. That will translate to a "sloppy" driver-to-car interface, ruining the main driver benefit of a racing seat + harnesses.

    I always said I would never "get into the seat bracket business" because the price points can be pretty low for some offerings. But after seeing SO MANY of these clunky mounts, we threw our hat into the ring and made our first foray into this market in 2014. This was our S197 Mustang (2004-2014) bolt-in seat bracket, which allowed the user to use ONE seat and ONE set of side brackets and ONE slider. It was made with 1x2" rectangular tubing, some plate, a number of threaded inserts, and a LOT of TIG welding. It was rigid and it worked.

    Well, not only was that too design (above) restrictive on what seat/side brackets/sliders would work with it in that S197 chassis, it took us over 3 hours to fabricate this bracket assembly. These tubular parts had to be manually cut, rehaped, and welded. Once all of the shaping, cutting and drilling were done it had to be TIG welded together using production welding fixtures. We sold this bracket for less than half of what our fabrication shop rate at the time, not even including materials or powder coating. We priced it that low "to be competitive" with other low end bracket kits. I would have been better off putting $200 in a box and sending that to people instead of selling these complicated brackets at that price. The numbers just didn't work with this fabricated part's labor intensive method of construction.

    In 2018 we bought a CNC plasma table, to join our CNC Mill and CNC Lathe purchased in 2014. This plasma table is a computer controlled cutting machine that slices flat plate and sheet metal with high precision, and we have been designing new parts using this tool where it makes sense. A proper seat bracket is one such place.

    In 2016 we made this seat bracket for an Audi R8, which included Sparco seats, OMP side brackets, and Cobra sliders on both sides. This design was made in-house and cut on a CNC plasma machine owned by one of my then employees.

    This design turned out SO beautifully that I decided then and there I needed a CNC plasma machine in-house. We literally moved to another building to be able to have the room for this and some other new production equipment.

    Well the Audi R8 racing seat bracket market is pretty darned small, and while we might make this design for production again someday, the reality is we are moving into a more typical car market for our customers: the S197 and S550 Mustangs.

    We own the 2018 Mustang GT above and we use it for prototype work on S550 products, including the seat bracket. This bracket bolts into the chassis at the factory reinforced seat mounting holes, and gives a rigid platform to bolt your racing seat to - either with side brackets directly (fixed) or with sliders (for fore-aft adjustment). Our brackets include mounting holes for racing lap belts as well as 2-3 sets of locations for 2 anti-submarine belts.

    Recently a customer/tester of ours lent us his 2007 Mustang GT to develop the S197 seat bracket design with, shown above. I will show both of these prototype installations and production images below, with each post dedicated to the car model we are covering.

    Thanks for reading,
    Last edited by Fair!; 08-29-2022, 01:56 PM.
    Terry Fair -
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev

  • #2

    Let's say you are not ready to put 1-piece racing seats in your dual purpose street / road course car. That is understandable, and probably wise - racing buckets can be a chore with ingress/egress, and with no tilting mechanism, hard to use with multiple drivers. They are also difficult to make work with 3-point OEM retractable seat belts, which SHOULD be what you use when NOT on a race track. As you will see below, all of these dual-purpose cars shown have 6-point harnesses AND the OEM 3-point belts.

    But if you want to be held in place firmly on a road course, a 6-point racing harnesses is the ticket - if your OEM or aftermarket tilt-back seats have a safe way to get the shoulder belts over your actual shoulders.

    We have done more than a few 6-point harness installs using OEM "tilt back" seats, and here are a few tricks with the install. Of course not every OEM seat is suitable for track use with a harness, and there are some concerns when it comes to the shoulder harness mounting, which we will comment on below.

    We have even put tilt-back aftermarket seats into cars, like this Corbeau set in a Mustang shown above. But that one had no racing harnesses...

    The most popular OEM seat we have added harnesses to is the Recaro sport seats in S197 and S550 Mustangs. This was and is an option on these cars that provides a decent amount of lateral support, and even has harness holes below the headrest for shoulder belt pass-thrus.

    On a "real racing seat" with a properly designed, aftermarket or custom built and reinforced seat bracket we will add the anti-sub and lap belts to clip-in anchors mounted to the bracket, as shown above and below. The 6-point harness above has the 2 anti-sub straps that then route up through a hole in the bottom of the seat and slide through the slit in the front seat pad. These anti-sub belts keep the main harness buckle and lap belts from "riding up over your hip" in a frontal impact, saving you a world of internal organ damage. The lap belts need to ride on the bones of your hip in a frontal impact, spreading loud through BIG HEAVY bones and not through your lower intestines of stomach, if they are sitting too high or ride up.

    With a racing seat and a seat bracket we always use the clip-in eyelets for the lap and anti-sub belts mounted to reinforced sections of the seat base, and that is a solid and safe setup. But an OEM seat doesn't have a reinforced seat bracket base for 4 more additional anchors, so we need to mount the lap and anti-sub belts another way.

    We've often mounted the lap belts into clip-in anchors mounted in holes thru the floorpan with BIG load spreading washers underneath, to keep them from pulling through the sheet metal in a big impact. It is less than ideal but can work, and many harness kits come with these washers and anchors, but they are available separately also.

    Mounting the anti-sub belts with an OEM tilt back seat can be a bit tricky, and most track oriented groups WILL NOT allow the old style 4-point belts anymore: they want to see 5, 6 or 7-point harnesses, or else the stock 3-point belts. Just assume 4-point belts are NOT LEGAL TO USE ON TRACK. They were never the safe option, in any case.

    On this Boss302 Recaro seat harness setup above we made some short steel brackets that bolted under the rear OEM seat mounting bracket. This extended the anti-sub belts back so they could slide "through the crack" in the seat - between the seat bottom and upper tilting seat back. This setup was simple and added the eyelet anchors just far enough back to reach without having to order custom anti-sub belt lengths. The ribs on the sides kept the bending loads in check, but we found a better way later on...

    The most popular and strongest version we built for mounting the lap and anti-sub belts with OEM tilt back seats in shown above, and we call this the "K brace". The four eyelets shown mount through reinforced threaded inserts welded into the 1.25" square tubing. These sit about 5 inches back behind the rear most OEM seat bracket holes (the two legs on the "K"). The rear bar section was spaced up to deal with a dip in the floor and had to be bolted through the floorpan, with a reinforcing washer underneath.

    The two pictures above show the K-brace bolted into a S197 Mustang and with the belts clipped into the eyelets. You can see the legs of the "K" mounting under the back of the stock seat brackets into the OEM reinforced holes in the floorpan. The other 2 holes in the K-braces were bolted through the floor with reinforced washers. This arrangement allowed the seat to be slide all the way back on the OEM sliders and the anti-sub belts could still slide "through the crack" in the seat without having to double back on themselves.

    The anti-sub belts then slid between the seat base and back through the crack, and you just SIT on top of these two belts, which wrap around and up under your crotch. The lap belts then come in from the sides and the shoulder harnesses from above to make the 6 point harness "cage" around you. This setup still allows the anti-sub belts work without a hole in the seat bottom, like a true racing seat would have.

    Of course this is "less ideal" than a real racing seat but still better than the OEM 3-point belts would provide, and they can be tightened to properly hold you into the seat. Everything is a compromise in racing, and in our view this one is worth it. We've done this type of install on over a dozen cars and nobody has complained - and it solved the 6-point harness problem while keeping the OEM seats (most of which have seat mounted airbags, which makes them safer in almost all crash situations). For street driving the driver can use the retractable 3-point belts, which work better for normal street use.

    Of course the shoulder harnesses need a solid place to mount from, and that is NOT a "bolt in harness bar". We DO NOT recommend harness bars for use on track driven cars, as they can and do buckle in a heavy frontal impact. A properly designed and installed 4-point roll bar (see above) is really the only safe solution for mounting the shoulder belts. A full 6+ point roll cage is actually more dangerous on a street car (where you are not driving with a helmet) than a 4-point, which has no bars right next to your head to cave your skull in.

    And before you ask, no, we don't make a production K-brace kits to sell for these Mustangs or anything else. Why? Because they are very labor intensive to make, and offering them for people to install themselves is not a viable option. We can't charge enough and most people wouldn't pay it anyway. People have copied this idea and we just wanted to share what we fell is "the right way" to mount 6-point harnesses in a tilt back OEM seat. You can possibly use these images and have a local fabricator make something similar.

    Last edited by Fair!; 03-04-2021, 11:47 AM.
    Terry Fair -
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev


    • #3

      As you can see above we have a solid option for "side mount" fixed back racing seats. We have this down - and this time I will talk about more tilt back / bottom mount seats.

      We have been doing more and different seat mounting brackets for more styles of seats lately...

      We have been selling and installing Cobra, Sparco, Recaro, Racetech and other brands of seats for ages, but the Corbeau RRB (above - 2016 install at left, 2021 version above right) was always our go-to for reclining seats. These types of seats are more appropriate for a real street driven car, as a fixed back racing seat often makes the back seat inaccessible, are less comfortable on the roads, and fit fewer people. The styling can be polarizing but each model usually comes in 4-5 materials, options, colors, stitch patterns.

      We just finished a new seat bracket design (4th revision!) for this "bottom mount" reclining seat on my our 2006 Corvette C6, above. This is a Corbeau RRS seat, which is the same on the torso as the RRB, but is easier to get into (yet has less leg support as the RRB).

      Corvettes come with absolute GARBAGE seats, right up until the C7's optional Sport seats. On track these blah C6 seats (even the Z06 version) feel like sitting on a park bench! We had to re-think our entire seat mounting bracket designs to work with the very different spacing of the bottom mount Corbeaus...

      Above left is one of our many seat bracket bases for side mounted fixed back seats. The width for the side brackets or sliders is VERY different than the bottom mount sliders used on reclining seats like Corbeau. The sliders are also much more substantial on the Corbeaus, more like the OEM sliders - which are often part of the seat mounting structure.

      Instead of re-designing our side mount style seat base brackets, we started over - and mimicked the OEM seat bracket/slider combos. We needed to add the tilt into the brackets, like the OEMs, so the seat sliders forward it also goes UP. On a side mount style seat we can just pick different holes in the side brackets to get the tilt right. Lots of other changes were needed, so it is a whole new seat bracket design.

      We will take what we have learned on this Corvette bottom mount seat bracket design and transfer that other chassis soon. Just something to think about for the future, if you are looking at a seat upgrade and don't want to jump right into fixed back racing seats... more soon!
      Terry Fair -
      2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
      EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev


      • #4
        C5 and C6 Corvette

        Mounting an aftermarket seat into a Corvette C5 or C6 model is extremely challenging - especially with the interior panels, door panels and carpet in place. That is what most dual purpose cars have, so we will dedicate this post to those models.

        The stock C5/C6 seats are utter and complete garbage - but they fit the tight confines of of the C5/C6 cabins.

        The back of the stock C5 and C6 seats are pretty compact, but they have to be to fit the VERY small confines of the interior, as shown above. The seat has to "nest" in the angled, narrow channel next to the VERY tall tunnel. The floor is flat and is made of composite, so there's not any "metal" area to put anchors into.

        As a side note the C5 and C6 seats are interchangeable, at least physically - there are likely wiring differences. And there is no real benefit from base C6 or C6 Z06 seats - they are all pretty poor.


        This Sparco EVO 2 seat was more of a challenge to mount than any previous car we've tried to put this seat into - even an NB Miata!

        We tried all manner of pre-made seat bases and they ALL raised the seat so much that taller drivers (over 5'10") simply DID NOT fit. We ended up making a seat base and slider to fit this seat into a C5, but it was a challenge and took many revisions.

        After many fittings and redesigns we finally got this seat to fit the owner (Erik, shown) and me, with a 5" height difference between us. That was a tremendous amount of work, and we even had to make our own side brackets to get the seat low enough. We chased every single millimeter on this seat install and the "wings" for shoulder support still touch the door panels.

        Our seat bracket base isn't light, but it is SHORT and STIFF, and with the slider, side brackets, seat and mounted anti-sub and lap belts it weighs 41 pounds. We put this setup in our C6 and it works fine, too.

        The difference between having the stock seat or an aftermarket seat "just mounted" with a store bought bracket and getting the seat fitted PROPERLY is huge. The C5 above went from a real bear to drive (shifting, steering, etc) to setting Top Time of Day. It is a massive difference in driver comfort as well as keeping your body planted to the seat, when using real harnesses.


        Another option from Sparco that we have seen used in a C6 is this Sparco ERGO / ERGO II.

        This is kind of a .... weird looking seat, and not one of my personal favorites, but it has one unique feature - the removable halo "wings". For a dual purpose car, where you want better visibility laterally for street driving, this is a nice feature. You can unbolt these wings and street drive the car, then bolt them back in for track use.

        One of our customer's, Alex T, bought this seat from us and installed it with the AMT seat base and it barely fit his C6 Grand Sport.

        If you look closely the seat head rest is smashed to fit under the roof and door seals, so ... you were warned.


        The best fitting halo style seat we have ever seen installed into a C6 with interior was this OMP seat shown below.

        I bought this for our lobby back when we kept 10-20 seats on hand for test fitting, and it turned out to be the "magic" seat that had a narrow enough halo to fit within the tight confines or a C6 (and likely a C5 as well). Good fitting seat, too.

        This was sold to a customer and mounted to his C6 Z06, as shown above. Again, best fitting Halo seat we have ever seen and the windows rolled up and down, it didn't bang into the door panels, etc.


        Last but not least is this Cobra Suzuka seats we put into a C6 ZR1 back in 2013. This is a great fitting seat with more leg support than a Sparco EVO, and better quality, too.

        Honestly if we had a better way to buy these seats we would use them more often, but our wholesale + shipping costs makes this a money loser for us.

        This was a really tough install and we were once again fighting for millimeters everywhere, for this tall driver in a car with a full interior.

        We had to trim some carpet, tweak the mounting brackets, lower the seats and use every trick in the book to make these WIDE seats fit in the tiny interior of the C6. I do not wish this job on anyone - we took 12 hours to mount both seats and had to write off a bunch of work to make the customer happy.

        Thanks for reading,
        Last edited by Fair!; 08-29-2022, 01:56 PM.
        Terry Fair -
        2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
        EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev