Changing driver's Seat Height

GAWen · March 31, 2007

I have read the article on changing the travel on the Avanti front seats, but i have a different problem. My wife, who is only 5 feet tall cannot see over the hood of our Avanti. And she is itching to drive the car. How, do I go about changing 1) the seat height (about 2 inches), 2) how do I get the front seat to travel forward an additional 4 inches? Thanks for any help guys. George Wendell, RQB 1600. BrownWtrSailr@aol.com

SBCA96 · April 1, 2007

Wow .. thats a tough one. 4 inches travel? Are you two close in height?

If you move it forward .. its not going to go back as far (obviously). If

you are 6 foot 7, and shes 5 foot ... you guys have a problem. Its got to

go 4 inches FURTHER than it already does? Blocks - maybe. I dont know.

Tom

GAWen · April 1, 2007

Wow .. thats a tough one. 4 inches travel? Are you two close in height?
If you move it forward .. its not going to go back as far (obviously). If

you are 6 foot 7, and shes 5 foot ... you guys have a problem. Its got to

go 4 inches FURTHER than it already does? Blocks - maybe. I dont know.

Tom

Tom, Thanks for the input and the suggestion, but I don't really think that is the total answer. I am 5'6" tall, and even with the seat as far forward as is will go, I have to reach REAL far to find the dimmer switch, gas (firewalling the gas pedal is a reach for me), and brake are no problem for me. But my wife, cannot/will not drive any vehicle unless her body is snugged up against the steering wheel. Heck, she even had problems driving my R-1 Automatic GT Hawk. George.

Gunslinger · April 1, 2007

Go to the Classic Enterprises website for reference to what I'm suggesting (www.classicent.com). They manufacture a seat anchor repair kit that is a piece of steel formed to match the floor ridge where the front hold down bolts attach the seat track.

See if you or a machine shop can fabricate a bracket similar in concept, but moves the front facing with the mounting holes forward four inches. If that can be done, you can either drill new mounting holes for the two rear hold down bolts or add extensions to the seat's rear brackets to continue to use the factory mounting bolt holes.

This way the seats and seat tracks don't have to be modified and there are no permanent changes to the car. It may require you either get seat belt extensions or longer belts.

I hope I've described this clear enough to understand what I'm getting at. Maybe even Classic Enterprises can fabricate them for you. They make the repair brackets as well as hog troughs. They may be able to come up with something that can work.

WayneC · April 1, 2007

<snip>
See if you or a machine shop can fabricate a bracket similar in concept, but moves the front facing with the mounting holes forward four inches. If that can be done, you can either drill new mounting holes for the two rear hold down bolts or add extensions to the seat's rear brackets to continue to use the factory mounting bolt holes.

This way the seats and seat tracks don't have to be modified and there are no permanent changes to the car. It may require you either get seat belt extensions or longer belts.

<snip>

I had some adapter brackets made for one of my (non-Avanti) cars a while ago, because I wanted to put some non-stock seats in the car. I measured mount positions carefully, removed the seat and sliders, and re-verified/measured the spacing of the mounting holes for the slider/floor and for the slider/seat, then designed an adapter to mate the new seat to the old sliders. So in my case, the adapters bolted to the bottom of the seat, then the sliders bolted to the adapters, then the sliders (with seat attached) were bolted to the floor.

It will take a little engineering work on your part to design an adapter to raise the seat and position it further forward. In my case, I did not want any additional height or fore-aft adjustments, although I was forced to alter the fore-aft positioning a little because the bolts otherwise would have interfered with each other, and the thickness of the adapter raised the seat a bit. I cannot recall how the Avanti seat attaches to the slider and the floor. Whereas I designed an adapter bracket with as little height and fore-aft differences from stock as possible, you may need to use a piece of rectangular steel tubing to gain height, and you can offset the mounts on the adapter to place the seat closer to the firewall. You may find you need a smaller-diameter steering wheel if you move the seat 4" higher.

I needed some fancy machining to fabricate my adapters, so I had them made from my design for about $60 per seat.

Here's a photo of my adapter brackets (which were painted black before installing):

The smaller holes are tapped to hold the slider-to-adapter bolts, while the "larger" holes are countersunk to recess the bolt heads of the adapter-to-seat bolts (which would otherwise interfere with the slider).

Your design would probably go between the floor and the slider and be nothing more than a rectangular steel tube with 2 holes drilled in the same relative positions top and bottom (except the upper set of holes would be shifted forward the desired distance), with perhaps a couple of nuts pre-welded in place if needed.

Edited April 1, 2007 by WayneC

James T · April 11, 2007

George,

The writeup I posted about extending an Avanti's seat travel can easily be used to extend it forward toward the dash instead of backward toward the rear seat. The key is to reverse the direction of the cut metal pieces. I accidently did this when I was distracted by a phone call and the result is exactly what I think you are looking for - the normal seat travel in total distance is maintained, the seat is simply shifted forward relative to the pedals and steering wheel by the length of the cut metal strips. Re-read my post and where the directions say to mount the strips to the seat track with the extensions facing rearward, simply reverse that so the strips are facing forward. Everything else would be the same, with one exception. To raise the height you can simply put spacers (washers will work) between the seat track and the metal strips. When I bought my '77 the previous owner (who was about 5' 9") had done this. If I recall correctly, he had used three washers that raised the seat about 1 ". You just add more washers if you need more height. Also, by raising the seat relative to the track, you should not have to modify the seat track to clear the bolt head. Note that this procedure can be easily reversed and returned to stock configuration in about 15 minutes per seat.

I didn't stress this in my original post but should have - modifying a seat mount is DANGEROUS BUSINESS AND I AM NOT RECOMMENDING YOU DO IT. Should you choose to ignore that advice, be sure to use at least Grade 5 hardware and nuts with nylon inserts when doing this, and then make doubly sure that all bolts are very tight. In case of an accident, the seat's mounting to the car is all that prevents the internal launch sequence from being initiated.

SBCA96 · April 11, 2007

Good points, modifying anything can be dangerous, always stick to the

basic design, at the least matching it. Do not use stainless hardware

unless it is graded hardware, most basic stainless hardware is only about

grade 2, which is bin bolts at Home Depot. Grade 5 should be used, its

not recommended to use grade 8 due to reduced shear strength.

As for the seat mounting holding you into the car, thats not entirely true,

its actually the seat belt that will be your friend in an accident. The seat

mount will keep you in place during those hard 0-60 runs.

Tom

I didn't stress this in my original post but should have - modifying a seat mount is DANGEROUS BUSINESS AND I AM NOT RECOMMENDING YOU DO IT. Should you choose to ignore that advice, be sure to use at least Grade 5 hardware and nuts with nylon inserts when doing this, and then make doubly sure that all bolts are very tight. In case of an accident, the seat's mounting to the car is all that prevents the internal launch sequence from being initiated.

GAWen · April 12, 2007

Good points, modifying anything can be dangerous, always stick to the
basic design, at the least matching it. Do not use stainless hardware

unless it is graded hardware, most basic stainless hardware is only about

grade 2, which is bin bolts at Home Depot. Grade 5 should be used, its

not recommended to use grade 8 due to reduced shear strength.

As for the seat mounting holding you into the car, thats not entirely true,

its actually the seat belt that will be your friend in an accident. The seat

mount will keep you in place during those hard 0-60 runs.

Tom

As always you folks have provided excellent insight into solving a simple problem. I will include all your input (modified, of course, to suite my needs) into changing the seat height and travel on my Avanti. Now, on to my next project, improving the brakes on my car. SteelTech seems to have the combination I am looking for. However, Turner Brakes is another avenue for me, except for the rear brake setup, as I have a flanged axel, vice the tapered axel. Now to convince the wife that the Avanti needs that much of a investment.

SBCA96 · April 12, 2007

Turners/Steeltechs 11 inch setup requires an interference fit load bearing spacer to

be heated red hot and installed on the spindle. Rotors are 100 a piece. Steeltech's

12 inch setup is a bolt on, requiring no spacer rotors 170 a piece. My Mustang uses

the factory hub, 11 inch rotors are 25 a piece, but the setup requires modern steel

wheels, so the initial investment is about the same, replacements are dime-a-dozen.

I am getting 10 sets made for sale, but I wont be selling kits for liability reasons. It

will be up to the buyer to purchase the calipers, mounting bolts, studs, rotors etc ....

I have all the part numbers of course, I have posted in previous threads. Just for

your consideration .. best to look at all possibilities. Happy hunting.

All have their pros and cons.

Tom

SteelTech seems to have the combination I am looking for. However, Turner Brakes is another avenue for me, except for the rear brake setup, as I have a flanged axel, vice the tapered axel.

ernier · April 12, 2007

The turner installation was very easy, I gathered my parts, rotors were under $60 each BTW, but Iif I had to do it all over again I would just buy the whole thing from Jim. Took only a couple of hours to do. There have been issues cited with SteelTech's customer service and I can't imagine needing any more brake than the Turner front disc and the drum rear.

I recently read a road test on a 74 Avanti II. With the factory set up the road testers recorded 60-0 in 140 feet on 70's tire technology. So, a properly set up stock system provides some credible performance and unless your car is experiencing poor stopping characteristics you may feel the whole thing wasn't worth the effort. My car did not stop well, the rotors were too thin and heated up quickly and subsequently caused the brakes to fade on high speed stops. But the cost of new rotors would have come close to the Turner kit and the subsequent sale of my stainless sleeved calipers and hardware pretty much paid for the upgrade so I took the plunge.

Bigger is not always better...after you lock them up it's all tires and suspension. Unless you're planning on doing some road racing the disc/drum set up will serve you well, and front brakes designed to stop 4700 lb station wagons may be overkill on a 3500 lb car, IMHO.

Ernie 64 R2

SBCA96 · April 13, 2007

Actually, with brakes bigger is most definately better. The idea is to get as

much braking force WITHOUT locking up the wheels. Once you lock them

up, all bets are off, and you are correct - might as well had 4 wheel drums

at that point! My 1960 Hawk was REALLY good at locking up with the 11"

finned drums up front. I modified the side of a Subaru wagon trying to get

the car to stop once - a futile effort.

The larger the diameter rotor, the more effective surface area you have per

each revolution of the tire. Studebaker discs were good in the day, but the

brake fade is the enemy. I was trying to develop something that could use

parts from a production run of a model, not just one or two years. Studes

disc brakes ended up on the REAR of Jags by the late 60s/early 70s. The

Turner 11 inch setup uses a rotor for a lighter car, the late 60s Mustang. It

is on par with the GT 11 inch rotor, though the caliper is larger on the newer

design. This allows the use of a larger pad, and an optional two piston. I

did some testing with a Gtech and got a 148 stop from 60. I am not totally

positive I had the Gtech setup right, but the numbers fell between a 65 GT

roadrace Mustang (144 feet) and another 65 Mustang with 13" Baer brakes

at each corner (155 feet) so I didnt keep trying to see what I could get down

too. I did notice that the MORE I tried stopping, the faster/better it stopped.

Keep in mind our Avantis arent exactly lightweight! (I used 3500 pounds).

I havent had a chance to test the 13" Cobra setup yet, the Avanti has been

down for the last few months with a broken power steering and other projects

have taken priority. I will post the latest results when I have them.

In my opinion, unless you are going for a stock rebuild, ditching the Stude

setup is worth while, at 175 dollars a rotor, and 110 each for wheel cylinders

(4 per car) that is certainly not the cost effective route - ending up with late

50s technology European brakes.

FYI, I priced the Turner rotors on Autozone's website last year, they were a

special order item and around 95 dollars each. If you found them cheaper

thats a good thing! Did you buy the modified calipers from Turner, or grind

the housing yourself? Also the brake pads, did you buy his special modified

ones or cut the wear tab off and grind it down yourself? Reading Turners

website I thought it was odd he didnt design his brackets to use "off the shelf"

parts, I hate voiding product warrenties.

Tom

ernier · April 13, 2007

The rotors for the Turner set up seemed to be available everywhere. My parts guy had to get them from a local wharehouse but that was still a same day deal. The grinding on the calipers is a little node that may serve a purpose in the original casting or on the assembly line, my guess if you did have a defective caliper no one would know it's missing. The pads I use are from Hawk, at the time my son was doing CAD design for a company called "Racing Brake" and they came highly recommended from lots of their customers, and I don't remember them having the wear sensor. The calipers are the same as the ones on my El Camino and if I'm not mistaken the same as a GN Regal. Both of those vehicles are heavier than the Avanti so combined with the master I have from some huge Chrysler I felt I had enough braking capacity.

Surely, if we were to be constantly in a situation where repeated high speed stops were the norm bigger would definately be better. For the street use my car and lots of other Avantis experience I think the benefits of 11" vs. 12" would be nil. A kit like Jim Turner's that is simple to install and is relatively cost efficient is all most Avanti owners need. Combine that with his customer service and for an Avanti owner wishing to improve their car's braking with the least amount of hassle I believe Jim Turner's are the way to go.

The work done on your brakes is impressive, for sure, and looking at Nimesh's Baer setup I do have "caliper envy". But for me, my Turner front brakes and my drums in the rear do the job.

ErnieR