Tubbing the front wheel wells affect shock tower rigidity

[Tangerine_sky]

I am thinking about tubbing my front wheel wells to fit 18 X 10 + 18 wheels wrapped in 275s. My only concern is that cutting out the stock wheel well is going to weaken the shock tower. Has anyone on here done this or have any input on how this would affect the chassis?

[Matt93SE]

If you don't replace the factory metal with something as strong or stronger, then yes, it will weaken the chassis some. Whenever you do the mods, you need to keep in mind what you're cutting out and be sure to replace it with something stronger. With that much tire, you'll need something quite a bit stronger to replace.
i.e. Don't use aluminum cans for the tub!!

[Bumnah]

Wouldn't welding aluminum to the factory steel be a bit tough?

[Matt93SE]

That's part of my point.

Mazda has actually figured out a way to weld/bond steel and aluminum. I don't know how well it works, but they were bragging about it when the latest MX-5 came out since they used aluminum for the skin and bracing on the hood, but the brackets and fasteners are steel. I remember a tech article about them finding a way to weld the two together for more strength.

[Bumnah]

I believe the R8 is using something similar as well. I just assumed it was a super strong adhesive. I suppose you could always rivet the pieces together.

[Longfellow]

18ga sheet metal was what I used. Worked pretty well for me. Dosnt hurt to bead roll the center a few times.

[Umai Kakudo]

I plan on doing the front tub modification a bit differently.

Instead of the usual tub route I will cut out the front fenders, reinforce the strut tower with tubing, and then use fiberglass or composite to make fender liners to keep the engine bay clean of junk and manage airflow around the wheels.

This should be much more rigid and a good option if the rules allow.

Inspiration


















The only way to know for sure how it affects the chassis rigidity is to do a before and after test. It is fairly straightforward to set up a lever system and use dial calipers to work out the amount of deflection.

Here is a good example of how it is done:



Video of Griggs Racing fixture to measure upright/strut deflection.

http://www.youtube.com/watch?v=9hPRD5tY-ss

I haven't seen anyone do something like this to a 240sx.

[Epstein]

I did chassis rigidity once by jacking the car up by the front toe hook and measuring 3 points per side on the frame rail before and after. That only gave me a 3D nightmare which I quickly abandoned.

So no one is going to post pics of the R34 Nismo Z-tune that has it's strut towers reinforced by bonded and riveted carbon fiber overlays?

BTW, F-ing sweet pics from Turbo Mag. Too bad we won't ever see import tech and quality info like that with them (and SCC) gone. Maybe Modified Rag will accidentally weld something on a day when the half naked Hispanic models are off. But I digress....

[Tangerine_sky]

Lots of good examples but I am not ready to build a tube structure for the front end. The rigidity test seems straight forward but I don't have access to that type of equipment. I was hoping I could just do tubs similar to longfellow's and retain at least close to stock strength in the shock tower.

[Matt93SE]

I would say you should be fine, assuming you make them out of proper thickness sheet metal. (look at whatever the stock stuff is and go that thick or slightly thicker, and be sure to keep/add some ribs to the metal to increase stiffness.

[Longfellow]

Stock metal is 20ga, I used 18ga. I can stand on mine and it dosnt do anything. But I would suggest doing a bead roll down the center of the tub for more strength.

Here is the thread I copied mine off of, pretty much step by step in pictures.

http://www.freshalloy.com/forums/showthread.php?t=186918

[Matt93SE]

Here is the thread I copied mine off of, pretty much step by step in pictures.
http://www.freshalloy.com/forums/sho...d.php?t=186918

I see you reading that thread..........

[jmauld]

What car are you driving that you need to tub the front end to fit 275's under?

I've got a S14 with 285's under the front, although, I am using a 18x9" rim. I get a tiny bit of rubbing when turning at full lock, otherwise everything clears.

[Longfellow]

And when your suspension compresses when going through a tight turn at anything over 50mph you still dont rub? How high is your car?

Tubs help out mostly with height issues. When your car is some what low to the ground then you need more height for suspension travel more than anything. Tubbing my car gave me over an inch of clearence above the tire.

[racepar1]

On the s-chasis cars the REAL limiting factor in front suspension travel is the wheel wells. The ONLY way to really make any difference in bump travel in the front is by tubbing the wheelwells. You can do whatever you want with the shock length and position but it will get you almost nothing. Increasing the amount of useable bump travel in the front suspension is probably the single best thing you can do for our cars suspension. S-14's and s-15's have more room in the wheelwells though so tubbing an s-14 is less necessary then an s-13, but it still helps.

As for rigidity, OBVIOUSLY whenever you modify an important load bearing structure on ANY car you must do something to re-enforce it. I honestly don't think that most people out there tubbing their wheelwells on 240's do enough additional re-enforcement. This is inevatably going to actually increase the weight of the car some, but the benefits are huge. If you do it right you can significantly increase the amount of compression travel of the suspension AND you can actually make the strut towers stronger.