weld or bolt in SFCs

[Keego Ridah]

Check out S&W Race Cars, http://www.swracecars.com/shopdispla...ion+Components

I have this stuff on my car and i love it.

[MORNINGSTAR2101]

sorry

heh, i was just sayin

[BP_Z28]

dont believe her..she likes to play mind games!

[PACE]

Ill just say WELD IN are the way to go!!!! The bolt in squeek most of the time!!!!!!!! and come loose..... THe weld in ones comes one with the unibody....

[DanO]

i think weve had this discussion like a million and a half times before. the general consensus is to go with the weld ons

just because its the general concensus doesnt mean its correct....

"never underestimate the power of stupid people in large groups" seems to come to mind..

either way, i think everyone is biased because of things they have "read" on internet forums. This opinion is heaviliy swayed by a few members and their opinions.. and after a while it becomes fact..

I doubt ANYONE here has determined the difference or has measured it objectively. outside of "gut feeling" there is no true evidence or factual information either way.

So, I would advise you to not listen to others opinions and do the analysis yourself!! Otherwise, you'll just buy what others have persuaded you to buy. You will not notice, measure, or feel a difference between any of the designs. To get a true factual and ubiased outcome, it would require more effort than you are willing to go into. so in the end, pick one, buy it, install it.

I just caution the purchase of weld in's.. if not installed correctly it can affect (keep the frame twisted). with bolt ons, you can adjust this several times.. then weld it in if your not satisfied.

[DanO]

Ill just say WELD IN are the way to go!!!! The bolt in squeek most of the time!!!!!!!! and come loose..... THe weld in ones comes one with the unibody....

my bolt ins are fine.. nothing a little loctite cant fix if they come undone (which they have not to date)

Squeak? hmm.. possible, but not typical

I'd just rather not install them solid untill i know everything is good...

We all know welds are stronger, but sometimes the term "overkill" comes to mind.

[MORNINGSTAR2101]

"never underestimate the power of stupid people in large groups" seems to come to mind..

i dont think that this phrase applies here. in order for it to be valid, you would have to incinuate that some of the members here are, indeed, stupid. the idea of getting good ideas from people who have done this kind of thing more than once comes to mind. if a mechanic who has a history of working on my exact car advises that welding on the sfcs is a better way to go, then chances are that im going to look into it and likely go that route. but, that could just be me. thats why we ask

[JoeliusZ28]

wow.... i guess im in the minority

I'd like you to prove the strength differences between weld in and bolt on. First you would have to define the load paths.

In Torsion, the bolt ons would be equally as stiff, For longitudinal forces, the weld in may be better due to the clamp load of the front mount.

just because its the general concensus doesnt mean its correct....

"never underestimate the power of stupid people in large groups" seems to come to mind..

either way, i think everyone is biased because of things they have "read" on internet forums. This opinion is heaviliy swayed by a few members and their opinions.. and after a while it becomes fact..

I doubt ANYONE here has determined the difference or has measured it objectively. outside of "gut feeling" there is no true evidence or factual information either way.

So, I would advise you to not listen to others opinions and do the analysis yourself!! Otherwise, you'll just buy what others have persuaded you to buy. You will not notice, measure, or feel a difference between any of the designs. To get a true factual and ubiased outcome, it would require more effort than you are willing to go into. so in the end, pick one, buy it, install it.

I just caution the purchase of weld in's.. if not installed correctly it can affect (keep the frame twisted). with bolt ons, you can adjust this several times.. then weld it in if your not satisfied.

I dont think theres a single person that has ever said "bolt-ins" are weaker. Claiming that people claim it stronger, and labeling them stupid is ignorant of you.

bolts, if anything are probably STRONGER than welds, common sense will tell you that especially if the bolts are hardened. However, strength is not idea of welding in subframe connectors at all. the reason you weld is to eliminate the play, and potential twist of a bolted setup. If a rail is welded in, its not moving at all, period. A bolt in SFC will have a certain degree of play, and while your arguement will probably be that it isnt much, ask yourself just how much does the chasis actually flex in the first place? Theres not much flex there to begin with, so having any ammount of play in a bolt is significant rigidity lost.

rigidity is the reason you install SFCs, not chasis strength (unless youre well above 500 rwhp).

[DanO]

i dont think that this phrase applies here. in order for it to be valid, you would have to incinuate that some of the members here are, indeed, stupid. the idea of getting good ideas from people who have done this kind of thing more than once comes to mind. if a mechanic who has a history of working on my exact car advises that welding on the sfcs is a better way to go, then chances are that im going to look into it and likely go that route. but, that could just be me. thats why we ask

Well im not calling people stupid, just the belief that they know something inherently without any proof or test data. Automotive chasis development is a very difficult area...

Also, while most people typically get to see the results of something, the analysis or true cause and effect is usually left up to opinion. i.e. if something looks broke its probably the fault of "X" without further research. This is not the fault of anyone, just merely the fact that R&D is not in people's budget.. its usually much quicker to replace the part than find the root cause. I know there are times when i have to make educateed guesses such as these and hope they are correct.

I have learned that the most obvious answer is not always the correct one. There have been failures in testing that have boggled the mind and caused hundreds of thousands of dollars to find the true cause.. and sometimes it could be due to simple things like improper bolt torque or it could go as far as improper mettalurgical make up... These results need to be reviewed and reproduced to determine that it was the true cause.

In the end, its usually much cheaper to make something significantly stronger than ever needed just so R&D does not need to be performed to develop the proper componet

If something looks weak.. throw 10000X the strenght at it.. thats the aftermarket way of life

[csmith4153]

I like Bolt in for 2 simple reasons.

1) They can alway be taken off for what ever reason.
2) I didnt want to weld something to my new 25k SS!!!!!

There are so many different connecters out there, there something for everyone.
From $100 weld in 2 point to $360.00 powder coated bolt in 3 points (That can be welded in).

[JoeliusZ28]

If something looks weak.. throw 10000X the strenght at it.. thats the aftermarket way of life

not sure if you read my post before, but strength isnt the goal of welds in this application. (or more specifically the reason they are chosen over bolt in).

[tenpin842]

My car being a T top car with my massive HP monster 305!
My car actually does twist. I even have a rip in the body. If you follow the top of my drivers side door (towards the rear of the car) The center section (not sure what its called) has about an inch where you can see the metal tear.
So I need mine installed before I repaint it.
I plan on keeping my car, so welding was fine.
I lowered my car, so I got the tubular ones. they tuck up alot better then the rectangle tubing.

[DanO]

not sure if you read my post before, but strength isnt the goal of welds in this application. (or more specifically the reason they are chosen over bolt in).

I did, but my comment was a blanket statement in aftermarket products.

and i dont think you are correct in the reason why "most choose weld in" i can bank on the fact that most choose it because they think its stronger or the internet said it was better.

While your reason may be a good arguing point and has validiity, its not the reason people choose one over the other.

I'm well aware of torsional and bending rigidity of chassis.. if you want, we can get into natural frequency's, suspension geometry, damper tuning, and spring rate and its impact on chassis stifness.. But in the end, i guess im just too picky to make a broad statement that one is better than the other. There will always be situations where each design is better and its up to the persons own choice.

[JoeliusZ28]

touche. i can agree with your blanket statement, however no one mentioned strength in this thread, you did

where i disagree with you is that idont think the rigidity of a bolt, vs weld is much of an opinion, that can and has been proven by measurement tests that you speak highly of.

and sub frame connectors are going to perform and have the same benefit in comparison[to each other], no matter what the natural frequencies, suspension geometry, damper tuning, and spring rates are. All of the things you mentioned there are going to affect forces which will remain constant before and after an SFC install.

[DanO]

touche. i can agree with your blanket statement, however no one mentioned strength in this thread, you did

where i disagree with you is that idont think the rigidity of a bolt, vs weld is much of an opinion, that can and has been proven by measurement tests that you speak highly of.

and sub frame connectors are going to perform and have the same benefit in comparison[to each other], no matter what the natural frequencies, suspension geometry, damper tuning, and spring rates are. All of the things you mentioned there are going to affect forces which will remain constant before and after an SFC install.

I agree the total deflection per unit load of a generalized welded component will be less than a bolt. However, there is a few factors you did not account for.. what is "the load" on that bolt. Nobody has measured what force that bolt is actually seeing. this is critical to determine if bolts are adequate.

And to bring it one step further, there is Tension that is preloaded into the bolt via 'torque' therefore the load required to move or lift that bolt increased significantly. A weld does not have this "preload" or clamping force. Depending on the geometry and loading conditions, i can argue that either one may be more or equally as rigid. There are calculations that can show how "rigid" a properly torqued fastener can be in tension and how much clamp load it can provide.

For example if you have a 100 lb/inch spring, under a free state condition it would deflect 1 inch for every 100lbs placed on it. However, if you then 'preloaded' that spring to 800lbs and then placed 100lb weight on it.. it wouldnt deflect.. Untill you reached the 800 lb preload.. then you would need 900 lbs for it to deflect one inch from the preloaded state and it would continue to deflect one inch for every 100lbs thereafter.. Bolts are esentially just very stiff springs with lots of preload.

Also, as the chassis gets stiffer, the natural frequency rates (ride rate) would increase as well. You can calculate it like two springs in series and determine where the point of diminishing returns lies. You only want to make the chassis stiff enough to not add significant impact to the suspension stiffness (no point in adding extra weight). Likewise, As you increase the suspension stiffness, you also would want to increase the chassis stiffness (rigidity, natural frequency, etc). in a VERY BASIC sense, there are two "springs" you need to worry about... suspension springs and chassis rigidity. (there is also, tires, swaybars, compliance, aero loads, etc.. but we wont go into that)

So my statement there, is that the vehicle is a system, you mess with one thing, there are others that are affected. The degrees to which are affected still need to be determined, however.