Wider track, or not? (Miata subframe into a Europa)

I thought I had found a really great solution for my rear suspension for the Europa when I found this car:

That's the rear subframe of a Miata grafted into the chassis of a Lotus Europa.  It appears like it would give me the opportunity to save the Europa chassis, and re-purpose the entire geometry of a Miata.  I really like the idea...

The catch is there is a lot you can't see in that picture... 

This is a complete Miata subframe sitting under a complete Europa chassis:

The most obvious thing to notice is that the top section of the subframe has been cut away, and a bottom connector was added. OK.

But the chassis is still sitting 4"or so too high.  What is less obvious is that the Europa chassis has been cut to let the Miata subframe sit at the proper height.  Not really a problem.  I am willing to cut as needed.  Here's a pic at the front corner:

The question is about the track width, and handling.  The less obvious part of the initial picture is that the Miata subframe in the black chassis has ALSO been narrowed.  It was cut in half, and the 2 halves were welded in separately.   The original track of the Miata is 59.2", and the Miata subframe has been installed in keeping with the Europa's original 53.3" track width. 

I like the wider look.  I intend to have large box flares, so I can make the body work.  But the track will be almost 6" wider than the original Europa front end, which I to keep.  

From a handling perspective, which is better... Keep the car track width similar front and rear, or keep the Miata geometry as originally designed?  

For the record, the car will have 2X- 3X the power of the original Europa.  It's gonna need more grip (which the wider track will help with).

I think I would like to keep the Miata subframe intact, cut the Lotus chassis as needed, narrow the rear track a little with different offset wheels, and widen the front track with wheel spacers. What's the disadvantage?

Once I start cutting, I am committed.

Wider rear track causes understeer. You can work around some of that with the usual tools , spring rates and sway bars. Trying to correct the extra track with offset will work if you can find really high offset wheels, but Miata wheels are already 38mm. You could possibly create higher offset steel wheels for the rear and lower for the front. Changing the front with spacers or offset will be adding to the scrub radius, which doesn't help handling. Myself, I'd be tempted to narrow the subframe some just because that 6" difference is a lot to correct with spacers and offsets alone. Moving the wheels in this way will move the roll center, but you may be able to compensate by having the angles of the A-arms set by raising or lowering the subframe relative to the Lotus frame. All of this involves some studying and geometry. I found this helped with understanding this stuff some....https://robrobinette.com/S2000RollCenters.htm

If you narrow the rear frame what does that mean for axels? Is there an easy fix or are you having 1 off axels made?

In reply to itsarebuild :

I think I am into custom axles regardless. 
 

SVreX said:

In reply to itsarebuild :

I think I am into custom axles regardless. 
 

If you are doing custom axles,  I would narrow it.

I don't think I quite agree with a wider rear end helping straight line traction.  Most drag cars and dragsters have narrow rear ends.

How hard would it be to put Miata front A-arms on the Lotus chassis without the Mazda subframe?

wvumtnbkr said:

SVreX said:

In reply to itsarebuild :

I think I am into custom axles regardless. 
 

If you are doing custom axles,  I would narrow it.

 

I don't think I quite agree with a wider rear end helping straight line traction.  Most drag cars and dragsters have narrow rear ends.

Most dragsters have wider rear ends than front ends. 
 

But my question is about cornering. Typically, wider track offers more grip in cornering. 
 

My question is about the relationship front to rear. There is nothing wrong with the existing subframe- it's a stock Miata width. 

DeadSkunk (Warren) said:

How hard would it be to put Miata front A-arms on the Lotus chassis without the Mazda subframe?

You mean in the front, or the rear?

I intend to utilize the Miata front hubs. Right now, trying to figure out the rear. 

Use the Mazda rear full width. Make the front track wider to match with new longer control arms fabricated to use the Lotus inner bushings and the Miata ball joints.

Attempting to stick to one focus at a time, as there's a lot to consider here...

Wider rear than front, you may be able to balance with tuning, but... you get a vehicle that needs to take a wide vehicle's path around cones while not gaining the reduced weight transfer benefits of width up front.

The path of trying to make up the difference with wheel offsets and spacers makes me uneasy. However, if you can make that all play nicely, then of course you've got this width issue knocked.

I'm sitting here wondering whether there's something we know about how the DeltaWing worked that would help us think more clearly about width disparities.

In reply to SVreX :

In the front. If you could ultilise  Miata upper and lower  A-arms attached directly to the Lotus frame, at the stock Miata track width, the rear could be left alone with stock geometry. The biggest problem at the front is probably how the body sits relative to the frame and suspension. Is there enough room for Miata components? The lower arms have the rear mount point well back, but that could be modified possibly. There is welding involved no matter what you do, front or rear. For my Corolla I built the front end to use all stock Miata components because it's a good handling car. Then I have to build/adjust my choice of rear suspension to follow the front through corners. Any autocross car will only go through a corner as fast as the front allows, then the rear has to be made to follow.

In reply to DeadSkunk (Warren) :

Gotcha. 
 

Should be room, but that's a question for another day!

Im not gonna eliminate welding. I will definitely be welding.  I'm just trying to simplify design. 

In reply to SVreX :

I’d cut it then

Wider rear track means less weight transfer at that end, which means more grip. If the front end stays the same, this does mean more understeer. Unlike messing with roll stiffness, you do gain grip overall.

Narrowing the Miata rear will lead to different roll centers. I think one of the big secrets to the Miata's handling is very little movement of the roll centers, and I suspect that narrowing the rear will change that. I'd concentrate on widening the front. On the MG, I abandoned my plans of keeping the Miata front subframe and just ended up attaching my own pickup points (maintaining the Miata geometry) to the car.

In reply to Keith Tanner :

That's about what I was thinking. You're better at verbalizing it than me. 

SVreX said:

wvumtnbkr said:

SVreX said:

In reply to itsarebuild :

I think I am into custom axles regardless. 
 

If you are doing custom axles,  I would narrow it.

 

I don't think I quite agree with a wider rear end helping straight line traction.  Most drag cars and dragsters have narrow rear ends.

Most dragsters have wider rear ends than front ends. 
 

But my question is about cornering. Typically, wider track offers more grip in cornering. 
 

My question is about the relationship front to rear. There is nothing wrong with the existing subframe- it's a stock Miata width. 

Ah, I gotcha.  When you referenced the power, I assumed you meant straight line grip.

I'd narrow the front Miata subframe to the same width as the rear & use it. Or build a tubular one that's the same width as the rear, but keeps the Miata geometry.

In reply to Keith Tanner :

That's exactly what I'm doing,too.

Did you get a chance to look at the Zamboni chassis? The top rails ran straight into vertical surface of the miata subframes and were welded on. Do that and land the roll cage rear down tubes on top of the subframe and you should get a rigid enough structure.

A slightly different option if you want to keep the subframe removable: cut off the rear horns of the lotus chassis, rotate them 90 degrees so the channel opens to the sky. Bolt them to the top of the subframe and weld the fronts to the top of the y portion of the chassis. Brace and box as needed and drop the rear down tubes of the roll cage on the subframe in this plan as well.

I would keep a full width subframe no matter what. You want a widebody so this gets you closer. You also are going to shove a longitudinal trans in there right? Those A-Arm mounts get pretty close together at the bottom and narrowing the subframe makes them pretty tight.

In reply to MrJoshua :

I've checked that. I have plenty of clearance for the trans I am using, even if I narrow it. 

I'm actually thinking of splitting my Europa body down the middle and widening it.  Of course I don't plan to use the Europa chassis at all.

SVreX said:

In reply to MrJoshua :

I've checked that. I have plenty of clearance for the trans I am using, even if I narrow it. 

That's very cool. You have room for the exhaust over the top of the subframe if needed right?

In reply to MrJoshua :

Exhaust can go over the engine and subframe. 

SVreX said:

 The original track of the Miata is 59.2", and the Miata subframe has been installed in keeping with the Europa's original 53.3" track width. 

+1 to what others have said (maintain stock track width).  But FYI the above is NC or ND track width.  NA/NB (which is what is pictured right?) are in the 55/56" range (depending on wheel size/offset)

In reply to ProDarwin :

Oh really?  I missed that. 
 

That helps quite a bit!