DIY - Chassis reinforcement ideas

One thing I notice when driving the car hard on tight twisted roads is that the chassis flexes. As I’m about to get my car repainted I was wondering what people have found to be the most useful for chassis strengthening. I know Coupeking is doing that almost as standard procedure. A lot of the work seems to be around adding welds to things like the rear wheel well to the bulkhead behind the rear seats. I’ve also seen a triangle shape being added in the engine bay between the frame rail and the firewall.

Does anyone have any experience to share in that area?
 
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eriknetherlands

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Just some images showing that e9's do flex & some reinforcements that i made / saw in other resto threads:

From a members car; the opening in the tunnel should be a flat round shape. It isn't anymore.
buckling tunnel.png



From my own car:
In red you can just make out the hairline crack. In green a weld already made by the PO... this is at the top of the tunnel, where a depression runs down both sides for the wiring harness to fall into.
20161218_223418.jpg

and another detail of the cracks; when you look closely you can see that there are actually 3 hairline cracks coming from the speed clip opening running down the tunnel.
20170113_203832.jpg


here's what i made to improve it. It now has 3 threaded bushes to accept the shifter console. It's inserted from under the body and then plug welded it into place:
20170110_064058.jpg
20170122_102852.jpg

I will not know if it is strong enough to prevent it from buckling again, untill I drive it. that'll be another 2-3 years at my speed.

Another modification is this one (i've seen it on more restorations): the sills have a middle layer that is connected only to the outer layer (just 0,8 mm thick) by spotwelds. As such it does form s closed section, but only to thin sheet. It could benefit from connecting it directly to the inner sill which is 1,5 mm thickness).
Here you see the 'open' channel, before the outer sill is placed. (Left sill, looing towards front wheel. Inner sill 1,5 mm on right, middle sill 'floating' on the left. Closing this channel with some tabs will increase it's bending stiffness immensely.

20190421_145542.jpg


These connections are best made at the lower b-pillar and lower C-pillar. Here's the pic of the lower C-pillar where the jack pick up point is now welded to the inner sill. and on the right pic you can see the b-pillar where i could have (should have ...) made the connection as well:
20190505_110503.jpg
20190421_145143.jpg


Another modification i did was under the rear seats, where the reinforcement plate sits that holds the big pin for the rear subframe. This reinforcement plate is only rigidly connected on one side to the inner sill with seams welds. the other side just is spotwelded to the 0.8 mm floor. In an ideal world, it should all be constructed in triangles. that is not the case here: the reinforcement just hangs on the wall of the inner sill, and the floor is not really strong. SO i opted to create another strong point for the reinforcement to be welded to.
In my car the floor under the the rear trailing arm pick-up points were rusted out, including the ends of the inner sill. So i needed to replace those sections anyway.
I made a new end section to the inner sill, with a larger flange that folds around the corner into the wheel well, just behind the reinforcement plate. It now connects directly to the reinforcement piece that sits under the rear seat, completing the 'triangle' to.
Gaping hole under rear right seat & New inner sill end section made (The flange in the green rectangle was my addition):

20160107_221640.jpg
20160107_230442.jpg


and lined up for welding:
20160107_232133.jpg


and here you now see how it supports the reinforcement plate. IIt was plug welded together later on from this side, so not noticeable anymore afterwards. The section left of the red line was added, in comparision to OEM shape.

20160602_224222-01.jpg


In the rear, i've reinforced the differential mount. As my trunk is quite airy at the moment; this was easy to do:
I doubled the vertical flange where the diff support is welded to:

20201102_234918.jpg
20201102_235230.jpg

then spotwelded the whole thing. The thicker welds are where it connects to the rear diff mount.
20201103_001911.jpg
20201103_002000.jpg


Now as you see, I haven't touched the front of my car. I need to open the hood still after 7 years working on the mid & rear of the car....
 

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Bmachine

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Just some images showing that e9's do flex & some reinforcements that i made / saw in other resto threads:

From a members car; the opening in the tunnel should be a flat round shape. It isn't anymore.
That is so impressive, Erik. This should make a real difference!
 
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tmh

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At that point just build a really, tight, well done cage and wrap it in leather. The car will get magnitudes stiffer than welding pieces across the floors into the rockers
I could not agree more with your point, although that box/rectangular structure connecting the rockers really should be a big improvement, Tieing in the roof as part of the cage/structure with two crossbars triangulating the left and right side of the structure behind the front seats would be the way I would go. Then tieing that together with the subframes. How much weight do you think that would add and how many hours of labor would you estimate for such an undertaking?
T.M. Hayes
 

Gazz

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There's a new Toyota out called a Yaris GR. It's one of those rare things these days - a homologation model - for the WRC. It has 259 more welds than a normal production Yaris, which is done purely to stiffen the chassis.
There are also 35.4 meters of structural adhesive compared to 14.6 meters in the standard Yaris.
If you have seen a bare metal E9 you will see just how poorly they are welded. It looks almost random in those areas normally hidden from view. Well mine was anyway so I couldn't not do it.

I am sorely tempted to get a Yaris GR, it looks like a hoot to drive. Nearly 270 hp from a 3 cylinder engine. And it weighs 2800 lbs.
 
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tferrer

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I could not agree more with your point, although that box/rectangular structure connecting the rockers really should be a big improvement, Tieing in the roof as part of the cage/structure with two crossbars triangulating the left and right side of the structure behind the front seats would be the way I would go. Then tieing that together with the subframes. How much weight do you think that would add and how many hours of labor would you estimate for such an undertaking?
T.M. Hayes
It depends on who you have do it. It's not an undertaking for an amatuer or you'll end up with an amatuer product. Specialty race prep shops usually do this type of work to a high level. It's worth every penny IMHO.

Weight? Not more than 100-125 pounds I should think but our cars are already fairly light... Especially when they are rusted. Well worth the investment if you want to add HP and improve both handling and safety...
 

Gazz

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A lot of thought put into your car Erik. Just be careful that the torsional forces aren't moved to non strengthened areas like the roof.
Unfortunately much of the work Erik is doing is only achievable on a stripped car.
I did a lot of welding around the trans tunnel and where it meets the engine bulkhead.
Every bit helps but in the end unless you are planning on racing, ( in which case you would have a roll cage ), we have to accept the flex as an E9 characteristic.
Be good to have a section of the site titled something like "Mods and Fixes" for worthy contributions.
 

aguirola

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Thanks for the various input information, great stuff.
They are wonderful solutions to cars that are to be restored.

I would like the source for the shock braces, as that, and possibly the diff support, as they are about the only options,
as I am not going to tear up my rustless car.

Regards, Alberto
 

eriknetherlands

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Which website used to have the pics?
I think I can dig them up.

Unfortunatly, no luck.
I've searched the WayBackMachine (waybackmachine.org) and although quite some info and pics are stored from around 2015 from the website of CoupeKing, the pics we're looking for were just one level 'deeper' then what was stored on the waybackmachine's servers.

Anyone else shared pics before of these modifications? Even if the website is currently offline, the waybackmachine may have archived them anyway.

anyway, I did find a pic of the thing we were initially looking for; it was on our own website all along:
1615885979258.png



see thread #159 from @bdigel in:

See the extra triangle between the firewall and chassis leg where the mouse pointer is?
I've seen also different version, where the top surface of that triangle is not horizontal but angled, climbing up towards the firewall.
Don't forget that the fuel and brake lines run through this corner.
1615885392187.png
 
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Gazz

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I did this mod myself and when you look at the flimsy intersection of the chassis rail and the bulkhead it seems to be such an obvious thing to do. Predrill the bracket for the fuel lines before you weld it in. I drilled both brackets in case I needed to run something through the other side as well. Once the engine is in you will NOT be able to access the bracket to drill it; even from the wheel well side.

Rack and pinion steering set up there. Nice.
 

Bmachine

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Unfortunatly, no luck.
I've searched the WayBackMachine (waybackmachine.org) and although quite some info and pics are stored from around 2015 from the website of CoupeKing, the pics we're looking for were just one level 'deeper' then what was stored on the waybackmachine's servers.

Anyone else shared pics before of these modifications? Even if the website is currently offline, the waybackmachine may have archived them anyway.

anyway, I did find a pic of the thing we were initially looking for; it was on our own website all along:
View attachment 114435


see thread #159 from @bdigel in:

See the extra triangle between the firewall and chassis leg where the mouse pointer is?
I've seen also different version, where the top surface of that triangle is not horizontal but angled, climbing up towards the firewall.
Don't forget that the fuel and brake lines run through this corner.
View attachment 114432
That’s the one I was thinking about! Yes indeed, it does seem like an obvious thing to do!

Thank you Erik.
 

m5bb

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I wonder what the guy that posted the E9 with a V8 S62, is doing to reinforce the whole car.
Talk about flex?
did-somebody-say-flex.jpg
 

sfdon

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we finish with Vbx1
 

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sfdon

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And then a layer of soundproofing...
 

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JamesE30

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Funny to hear that. I visited a workshop in Czech where they do that. I wondered how much it helps..

This is the only pic I took showing it but you can get the idea:

B374177C-380F-4FBA-A025-B2A6E0347135.jpeg
 
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