Has anyone done this? Any thoughts as to what level of stiffening it would provide vs SFC's etc?

Earlier this year I had the car completely apart getting rid of the sound deadening etc and I remember thinking to myself.. hey maybe at some point I should get this all seam welded...

 

I started to on a local 4th gen, but the welder had problems

From my reading, it adds a LOT to the stiffening of the chassis. Its fairly depressing how much epoxy/glue is used to hold the car together. A few places I really want to do would be the front shock towers and rear end area like the back seat and trunk

 

Seems like A LOT of money in labor.

 

I'd think you'd really need to investigate where the tub/frame is flexing the most and focus on those regions. I'm wondering what the hardcore Sentra and NX racers are doing

 

If I was thinkin about doing this job I would prob try to find an affordable mig welder from the want ads and learn how to do it myself. The welds dont need to look very good and if they are relativly weak they will still be stronger than glue.

 

I am very tempted to do it. I have a friend with a welder who could do it for me for next to nothing. Case of beer maybe.. lol.

 

Too bad you're in Ontario, we just got the tank filled on the welder

I started doing it some spots on the 240 and IMO it's what will prevent a car from tuning into a rattlebox with mileage and years, especially if you have a stiff suspension (hell on the chassis).

 

Broaner did some seam welding on his LCAs and a few other parts, and now on his 240 he is welding and strengthening everything. Hopefully he'll chime in here.

 

Yeah that's why I think it might be good... I'm on 9/6 coilovers now and polyurethane everything and so far so good but I expect over time it'll get worse, plus the car's already 8 yrs old now. And a nice stiff chassis is never a bad thing for handling/racing.

 

What would we be looking at money-wise? I may be down for this later down the road when I go back to a coilover setup.

 

No idea. I have not gotten quotes or anything; I was planning on either doing it myself if I buy a welder at some point or getting a friend with one to do it.

 

I'm bumping this thread up for a few reasons. First, I have thought of the same thing, especially recently. Second, I am getting ready to do some work and might strip the interior and this would be a good time to weld up the seams on the car. I already have the trunk out (yeah, 5 mins, I know) and I see a lot of spots there.

Also, Lou Santiago did this on an old Nova I think on Musclecar TV. Although he had his car jacked up, leveled and suporting the frame. He was trying to get the "sag" out of an old car, but 4th gens or older would have about the same metal fatigue as some older american iron.

So, here's the reason for the bump. Can we make this the definitive thread for seam welding? Post up some pics of either what you have done, or some pics from when you had your car stripped and show us/me/others where we should be welding. Might want to break it down my generation also...

Thoughts?

 

Even if you welded all the seams, I suspect you still wouldn't get the increase in chassis stiffness that subframe connectors will give you. The OEM metal itself is thin, cheap, and flimsy, so welding it together can only help so much.

Thankfully, after years of waiting, a reputable shop is now making good subframe connectors for 4th and 5th gen Maximas...get in on the group deal while you can! http://forums.maxima.org/showthread.php?t=517967 (There are other threads with more technical info linked from that.) It's a great deal and will probably take much less work than trying to identify and seam weld everything on your own.

BTW when I get my SFCs I plan on seam welding them for most if not the entire length along the frame rails....

 

I wasnt suggesting one over the other. Both the SFC and some seam welding would be nice they should go together quite well. But since we have unibody cars not car-on-frame, it's best to seam weld everything. Even with Car-on-frame, it's best to seam weld up or box in frame rails.

As far as any chasis stiffness, the best way to tell is going to be to put a mic on the car or frame and start jacking up suspension pieces (at all 4 corners) and measureing body flex and twist. Doing this before and after is really the only way you are going to know how much of an improvement you get.

 

That would be a way to quantitate the improvement, but all reports thus far suggest that the qualitative improvement is tremendous, and that's what I care about.

Anyway, back to the topic because I agree with you that seam welding could still make a big difference, especially on parts of the car that SFCs don't cover. I'll send my pal Broaner this way and see if he has anything to add. I'm sure he has pics of seam welding he's done, but most might be for his 240SX project, which he stripped his '95 Max down to build.

 

Thanks for the heads up on this thread Tomer.

Several things. First, if you were even considering paying someone to seam weld your car; STOP! There is no possible way you could justify paying for the labor when you could do it yourself for a fraction of the cost. If you really wanna go crazy buy a $500 MIG setup and teach yourself. There are tons of books out there. Doing the entire shell, thoroughly, of any car would be over 50 hours of labor. At a conservative rate of $40/hour thats four times the cost of the welding setup.

Second, seam welding only portions of the chassis is effective but not to an extreme extent. During the winter of '05-06 I seam welded nearly all of the the rear half of the chassis on the car. The result? My S13 is totally stripped of all interior pieces that would inhibit groans and creaks. The rear end was super tight and "vaultish" (Credit to whomever came up with that awesome word to describe a chassis.) All the while, the front end was still a groaning and grotesquely loose hooker. This winter, as you can see from the link VQuick posted, I have now tightened up the front end substaintially. I have no results yet though.

Now, on to technique. Time and time again you see people say that you have to space out the weld on the seam to stop warping. This is BS. If you do it right and take your time warping will not be an issue. Besides the sheet metal is already spot welded together, thus insuring that the overall shape of the chassis will remain correct.

So, I'm a firm believer that "stitch" welding is not required. The only difference between stitch and real seam welding is that one is ugly. I'll let you decide.

To fully seam weld without warping you basically need to do a series of spot welds or mini beads if the void is wide. Every time you run across the seam let go of the trigger and stop the arc. If you have your settings correct you should be able to lay another spot right away. Sometimes, if your going accross a larger void you'll have to give the metal a second to cool before you begin again. In order to achieve the best results you really need to spend your time prepping the area. I use a knot end wire wheel with drill chuck attatchment, a heat gun, a 1" wood chisel and a screw driver. Start by heating of the sealer and scraping out a majority of the globs with the chisel. Then go to town with the wire wheel until you get to bare steel. Then use the heat gun again and the screwdriver to get as much out of the seam as you can. You need to get as much of the sealer out of the seam as possible. I say, "as much as possible" because without some sort of harsh acid solution there is no way to get all of it out. Also, for best results, since you will be stoping and starting so frequently you should invest in an auto-darkening welding helmet. The good ones start at about $140 and go up to $300. It is a very sound investment because it will make the weld easier and prettier.

Now for pics of the process... This is last winter when I wasn't very good at it. Since then I have done the rest of the passenger compartment(Pics of that coming soon). I've left the majority of the seams forward of firewall alone because the chassis will again go under the knife next winter for a full on frame jig/cut out the whole thing and start fresh chassis buildup from the front subframe to the rear.


Check my homepage for more pics.

 

My 2 psi:


First, SFCs and seam welding are complementary. Neither is a substitute for the other. Seam welding works by taking the stress on any given part of the unibody and spreading it out across all the parts in that area, so it will be great at increasing resistance to local deformations around the suspension components. SFCs can't do that. What they can do is help the overall flexural rigidity (bending the car by the front and back) in a way that seam welding can't because they add meat to the big length of metal in the underbody. Remember, seam welding doesn't actually add any metal.


Second, since seam welding and SFCs work best on different areas of the car, having one technically increases your need for the other! Always remember this: You can never get rid of structural stress. All you can do is send it somewhere else. So, whenever you stiffen part of your frame, you are always increasing the stress that some other part of the frame (and your suspension, for that matter) will see.


Third, seam welding adds suspension noise and will increase the amount of certain frequencies of vibration. Period. So, if your car is your daily driver, consider putting down a layer of sound deadening while you have the interior and carpeting ripped out.


Fourth, if you do any chassis stiffening as significant as what we're talking about, keep at least one good source for suspension parts on your speed dial and purchase every single Energy Suspension or Pedders suspension bushing you can get your hands on. Your dampers will be working a lot harder, and you may chew up the stock rubber bushings and strut mounts faster than you'd like.


Fifth, NO mod to increase the rigidity of the 4th or 5th gen Maxima's frame should EVER be doubted. Applied with care and due consideration of the effects, yes. But never doubted. If there is any way you can do it, do not hesitate. To say that chassis stiffness is the weakest link in this car is a gross understatement.

 

I agree with everything you said and I agree with this statement to a degree. I can see that vibration would increase because the chassis now has a higher spring rate. But on a car with interior panels stiffening the chassis stops those various compenents from rubbing against each other and squeaking or rattling. So, suspension noise goes up. I agree. But interior quality of the car effectually goes up.


This is definitely true. As chassis stiffness increases the chassis spring rate increases as well and loads on suspension components increase exponentially. Even ES bushing will have a tough time dealing with the loads a fully seam welded and SFC'ed/caged car will put on them. Everywhere possible switch to high quality spherical heim joints. The problem is that there are no products like this available for the A chassis' for retail.


Definitely agree. This holds true to nearly all production cars produced.

 

Thanks for the informative posts, guys. I can see that a stiffer chassis will increase stresses elsewhere, but I question that it's actually going to put more stress on the dampers. Say 1/2" of flex is removed from the chassis. That means that the damper will travel a bit farther and also a bit faster since the chassis play has been reduced, but is that really going to harm the dampers? They're not bottoming out, just moving a bit more. I can see that there may be a bit more wear but not "a lot" more wear. With manufacturers greatly increasing the stiffness of production cars in the past 5-8 years, have they also upgraded their OEM dampers? I haven't heard anything to suggest that this is the case. I'm just thinking aloud here.

 

What I said was that they'd be working harder. More travel and faster motion mean more stress by definition. What I think you're trying to get at is whether that extra work and stress will significantly shorten the life of a damper. That depends on spring rates, wheels and tires, tire pressures, roads, driving style, and of course which dampers you have.

You may also be getting at whether the life of your dampers would be shortened so much that that offsets the benefits. My answer to that is a very emphatic "no".

You're not likely to hear anything of the sort unless you specifically ask someone who would know. Companies always design the car and then select whatever dampers they can get (or make) to suit the purpose. Given that so many factors on which the durability of a damper depends -- vehicle weight, tire technology, suspension geometry, etc. -- have been evolving (sometimes rapidly) over the years, the dampers themselves have had to change with those things and it's hard to say whether they have become more durable "overall".

 

Good points, and yeah, it seems the benefits of chassis stiffening pretty much trump any drawbacks.

 

I discussed having this done with a local guy who does only this to cars day in and day out, he said it won't be cheap, but it would help a lot...I just haven't had the time to leave my car with him lately, but this thread rekindled the idea so maybe I should pay him a visit...

 

Read Broaner's post, it will probably be upwards of $2k to get someone else to do it for you. You can do it yourself AND have a badass MIG welder of your own (to install SFCs maybe ) for a small fraction of that cost.

Then again, if you have no free time, it might be worth it. Personally I think it'd be a cool project, you can't majorly screw up your car by doing it and the car will be driveable or close to it for the most part while you're in the process.

 

1. For $500, all you're going to get is a mediocre MIG welder. even if you buy one used, you're still not going to get anything terribly impressive for that price.

2. done wrong, you CAN do some major damage to the chassis. Minimum problem could be burning holes in the chassis and weakening it. worst would be possibly tweaking the frame from heat damage. you DO in fact need to work your way through the car, gradually and evenly. If you just start at the left rear and work your way to the right front, the chassis is going to warp and tweak, and you will NEVER get it fixed. you need to do things slowly and evenly. couple inches at a time, both sides at a time. keep the frame as cool as possible as well. that means that you DO NOT just lay down a bead from one end to another. do an inch or two, then go to the other side while that's cooling down. hit the other side, then go to the other end of the chassis and hit a couple spots up there.

I've seen more cars screwed up because of seam welding than anything else people try to do at home.

 

Anybody have an opinion on seam welding vs chassis foam? Would one complement the other? Different corners vs structures? Ignoring fire, cost, time, and messiness of either of course.

 

Well in that case I stand corrected. With my severely limited welding knowledge I was relying mostly on others' information here, my apologies.

 

Yes.

There is some overlap, but definitely not 100%.


Think about it this way: Seam welding spreads load out, and chassis foam adds strength. There is a place for both.

Chassis foam will also add weight and help deaden vibration. Seam welding will do neither.

 

1. For $500 you can get a Hobart 180. That will do everything an automotive hobbyist could want. Of course doing 1/4" is a bit tough but how often is somebody going to weld a 1/4" piece on a 3,000lbs car?

2. Generally I agree. Still, anyone with average intelligence could teach themselves to properly do the job.