Maximum stiffness and maximum ground clearance?

[Casgar 21]

Since I read the "Fastback inner rockers"-thread it got me thinking if I could have the cake and eat it too. Stiffening the chassi seems to be something most people think is a worthwhile modification, be it inner rockers or subframe connectors. The problems for me is that I'm afraid the inner rockers will interfere with my S197 seat swap (or similar moderns eats) since the space between the outer rocker and tunnel gets tighter, and the problem with subframe connectors is that they reduce ground clearance, or intrude into the cabin in the case of through-floor-connectors, which could also interfere with the seat swap.

I don't really know if any of my "problems" actually are real problems (feel free to anser), but if we assume they are, what would be the best/optimal way to stiffen the chassi both longitudinal and torsional if we ignore factors like time and money and still keeping the original floor. Let's also leave roll bars and full cages out of the question.

[fvike 173]

The floor at the seat riser is double bottomed, so SFCs cannot interfere. Convertible rockers will take up some real estate, but it should be minimal up on the seat riser. I cannot see that it should be a problem.

[Casgar 21]

1 hour ago, fvike said:

The floor at the seat riser is double bottomed, so SFCs cannot interfere. Convertible rockers will take up some real estate, but it should be minimal up on the seat riser. I cannot see that it should be a problem.

I'm 6'4" so any way to stiffen the chassi without compromising my choise of seats and seating position is my primary goal. Based on the answers I got here the seat platform will have to go, which MIGHT make both the inner rocker and through-the-floor connectors in the way.

My secondary goal would be to keep the ground clearance as close to stock as possible. This one isn't written in stone as much as the first one, but it's more of a general direction I would like to follow as much as possible. Why? Because I'm anal and don't like to see something hang lower than the floor. :) If I could be sure that just adding a panel behind the rear seat and maybe extend the front subframe somewhat would be adequate to handle ~400 bhp I would probably just call it a day, but at the moment I am not.

My backup plan would probably be something like TCP connectors and X-brace.

 

The SPEC-chassi from Roadster Shop also have some interesting things going on that I would like to hear what other people think of, like the cross-plate and tunnel support.

http://roadstershop.com/product/full-chassis/1964-70-mustang-spec-chassis/
http://roadstershop.com/galleries/1968-mustang/

[Mach1 Driver 560]

The Roadster Shop's complete chassis is a novel idea. It seems to go over the front frame rails and inboard of the rear rails- and leaves the originals in place. Its a bit pricey at $12k. I prefer to leave my car closer to stock with improvements (ok, you can call them bandaids) to the original. This is pretty cool though. I wonder how it would hold up under chassis torsion tests?

[latoracing 256]

Looking at the RS chassis, there is something that kinda sticks out to me. The front suspension does bolt to the existing frame rails, but the rest of the chassis is sitting on bushings. Their paged didn't call out what type of bushings they are, but if it were bolted up with urethane or some sort of semi flexible bushing there is instant flex aft of the front suspension. I might be incorrect in my point of view, but I would want this frame solidly attached to the unibody. 

$12K wouldn't be too hard to swallow if the chassis came with all the suspension components. Shipping might get into your wallet a little...

 

[Mach1 Driver 560]

2 hours ago, latoracing said:

The front suspension does bolt to the existing frame rails, but the rest of the chassis is sitting on bushings.

Hmm good catch. It looks like it may be bolted horizontally all the way in the back- frame rail to frame rail.

[MikeStang 247]

I can tell ya right now that if you want to pack a set of new mustang seats into one of our cars the seat riser's will have to go given your 6' height..or you could go with a MTF drop in headliner to get some head room, but the new seats from about 2010 and up are way tall..I have a set from a 2012 we test fit Into my friends 69 as well as his wife's 68 FB and it's a tight squeeze and my head almost touched head liner at 5'-9" tall.

If you want the lowest possible seat height and wish to leave the risers try a set of Fiero seats and an upholstery kit from Mr. Mike's Fiero seats...besides the fiero seats look much better than the SN seats and are more comfy

[Casgar 21]

13 hours ago, MikeStang said:

I can tell ya right now that if you want to pack a set of new mustang seats into one of our cars the seat riser's will have to go given your 6' height..or you could go with a MTF drop in headliner to get some head room, but the new seats from about 2010 and up are way tall..I have a set from a 2012 we test fit Into my friends 69 as well as his wife's 68 FB and it's a tight squeeze and my head almost touched head liner at 5'-9" tall.

If you want the lowest possible seat height and wish to leave the risers try a set of Fiero seats and an upholstery kit from Mr. Mike's Fiero seats...besides the fiero seats look much better than the SN seats and are more comfy

From what I can conclude the S197 seats are slightly lower than the SN95 seats, and a SN95 seat with a lowered seat riser is about equal to stock seat height. My reasoning is that using a S197 seat with no riser will be the biggest gain in headroom while still keeping the option for a Mach 1 look. https://www.tmiproducts.com/mustang/browse-by-vehicle/late-model-2005-12/2005-07-mach1-style-leather-upholstery-front-buckets-only.html I also feel like the MTF headliner is not the best solution since I alreay feel like the sun visor would block out my sight as soon as I flip it down. I also have a hard time believing it would let me gain 2 1/2" of headroom. It feels like the distance between my current headliner and the outside of the roof is like 1 1/2" at most, inlcuding insulation.

Does anyone have any measurements on how wide the S197 seats is at the widest part and how high off the floor that part is? I guess it would be easier to know the measurements instead of just speculating.

[RPM 1,190]

On 2/12/2019 at 1:29 PM, Casgar said:

Since I read the "Fastback inner rockers"-thread it got me thinking if I could have the cake and eat it too. Stiffening the chassis seems to be something most people think is a worthwhile modification, be it inner rockers or subframe connectors.

Since stiffening my chassis I don't classify it as worthwhile, I say it's mandatory. For me anyway, who wants a car that will handle.

The problems for me is that I'm afraid the inner rockers will interfere with my S197 seat swap (or similar moderns eats) since the space between the outer rocker and tunnel gets tighter,

This is something I didn't realize until I tried to fit a pristine set of 2007 MB CLS 63 AMG seats into my 69. I was too concerned with the width of the seat rails and not the total width of the seat.

and the problem with subframe connectors is that they reduce ground clearance, or intrude into the cabin in the case of through-floor-connectors, which could also interfere with the seat swap.

My SFC and many others don't extend lower than the bottom of the front frame rails.

I don't really know if any of my "problems" actually are real problems (feel free to answer), but if we assume they are,

Yep. You're best bet is to have a seat on hand to fit. 

what would be the best/optimal way to stiffen the chassis both longitudinal and torsional if we ignore factors like time and money and still keeping the original floor. Let's also leave roll bars and full cages out of the question.

I would think a perimeter frame would be your best bet. My Mach 1 got really stiff with SFC, inner rockers, one piece grafted seat riser w/original seat pans as the true 1 piece risers were 1" taller, an export brace and Monte Carlo bar.

I guess it would be easier to know the measurements instead of just speculating.

Even if you bought the S197 and they didn't fit, I don't think you'd get hurt reselling them.

If you remove the seat riser, couldn't you tie in some 1" square tube between the SFC and rocker for solid seat platform? I'm 6-2, and in order to gain headroom when installing the Audi A4 seats, I made non adjustable seat rails which bolt to the stock seat pan. It's my car and I don't care who can't reach the pedals. I also installed the MTF headliner. It's a bit pricey for me, but added valuable headroom. If your sun visor blocks too much of the road, don't use it.