building custom strut bar, unsure on tube dia to use

[Morphius]

If your clamp load is adequate, the plate shouldn't move due to the shear loading. The nut will still transfer load to the stud.


Also, when attaching the strut bar you want to load the front of the vehicle to drive the loading to be largely in tension. Thus mimizing the size of bar required.

 

[FIBA M - EC17PSE]

If your clamp load is adequate, the plate shouldn't move due to the shear loading. The nut will still transfer load to the stud.


Also, when attaching the strut bar you want to load the front of the vehicle to drive the loading to be largely in tension. Thus mimizing the size of bar required.

I made the holes for the studs to just fit so its not got alot of movement anyway,
When i installed it i had it on the groud so it would hold the tension and not push the towers out and cause issues

 

[Morphius]

When i installed it i had it on the groud so it would hold the tension and not push the towers out and cause issues

That's a good step. Better yet would have been to have 4 friends set on the front when you set it, but that'll work ok.

 

[NHerron]

If your clamp load is adequate, the plate shouldn't move due to the shear loading. The nut will still transfer load to the stud.

That's all fine theory wise (which I don't discredit theory practice) but real world has shown the studs have moved even under the proper clamp load and wrecked the threads. Simple as that. Doesn't really surprise me anyway, as I'm sure the cornering forces exceed what the puny clamp load exerts...

There are numerous simple ways to guarantee against the movement.

 

[Morphius]

That's all fine theory wise (which I don't discredit theory practice) but real world has shown the studs have moved even under the proper clamp load and wrecked the threads. Simple as that. Doesn't really surprise me anyway, as I'm sure the cornering forces exceed what the puny clamp load exerts...

There are numerous simple ways to guarantee against the movement.

Real world is that if it's taking out the studs (threads) the torque wasn't right or the bar is installed wrong. Clamp load is applied to every fastner on your car. Prime example is the bolts that attach the knuckle to the strut (1g) or the bolt that attaches the strut to the lower control arm (2g). Those bolts can see extreme bump loads.

 

[NHerron]

Your examples are in a WAY different situation then the strut situation. The torque value on a 2G strut to lateral lower arm is just to keep the bolt in place, the torque doesn't hold any load other than keeping the bolt from coming loose and falling out there. Whereas what *your saying* about the strut, the torque would not only be responsible for keep the stud tight, it also must keep the strut bar from sliding underneath the flange. And this is where I disagree, I just don't think it's going to be able to keep all those forces in check without some kind of reinforcement. Either an intended reinforcement or when the threads contact the brace ID.

Take for example this Pontiac Bonneville I'm working on for a friend. It comes with a strut brace from the factory so you know they have a little R&R into it. Anyway, it has a flared edge to the metal right near the securing nut flange so when the strut tower flexes in, it pushes against the flared edge. Thus, the nut wouldn't even need to be torqued to transfer the load. The hole around the studs is slotted for this reason also.

Let me know if anyone wants more pictures as I seemed to have gotten too close up to verify it's even a strut brace

 

[FIBA M - EC17PSE]

Yes take the nut off and let us see whats under it

That's a good step. Better yet would have been to have 4 friends set on the front when you set it, but that'll work ok.

Im assuming thats going to keep the towers cambered in but that would then put excess pressire om the outer section of the studs which is not going to help and could be worse anyway

When i take it off and finish the rear bar i will take some snaps and post them up and i will inspect the studs to see how they are and if its caused any wear

 

[NHerron]

I'll get them by tomorrow night

Here ya go

 

[Morphius]

Im assuming thats going to keep the towers cambered in but that would then put excess pressire om the outer section of the studs which is not going to help and could be worse anyway

You would have needed to do it when you welded it, not after.

 

[Morphius]

I'll get them by tomorrow night

Here ya go

The lip around the edge is merely to increase rigidity of the bar/mount itself. Not to trap the nut. The hole is slotted to take into account build tolerances. Notice there is no wear pattern on it from the nut sliding or moving. (ie torque and clamp load was correct.)

Here's a good read:Is a Strut Tower Bar Really Needed?

 

[FIBA M - EC17PSE]

You would have needed to do it when you welded it, not after.

When i made the sizing and cuts for the bar i tacked it on the car then welded it then placed it back on when it was still a little warm so when it cooled it pulled in a bit more.

 

[NHerron]

The lip around the edge is merely to increase rigidity of the bar/mount itself. Not to trap the nut. The hole is slotted to take into account build tolerances. Notice there is no wear pattern on it from the nut sliding or moving. (ie torque and clamp load was correct.)

Here's a good read:Is a Strut Tower Bar Really Needed?

Link doesn't say anything about how a strut bar is secured. However I did find 333lbs pushing outward at the top strut tower interesting. This is kinda what I'm talking about.

Imagine cutting a slot in a piece of metal plate. Now fit a bolt (strut bar bolt) through the slot so it can be moved either direction in the slot. Thread a nut on the bolt on otherside of plate, so it tightens against the plate. Use any size flat washer and torque value you want. NOW, equally apply the example (333lbs of force) perpendicularly to the bolt so it tries to pull it down the slot.

Take another look at that picture and notice where the RIGHT side of the nut flange ends up at. It's just where the metal starts to curl up. As said in your link, the strut bar is under tension in a turn so it makes sense why the nut flange is where it is.

With all the engineering going on with cars I just don't think they'd leave something like that all up to the mere tightness of a nut, when it's as simple as a weld, a raised bump, or curled piece of metal to keep the nut from letting the metal slide out from underneath it.

 

[Morphius]

With all the engineering going on with cars I just don't think they'd leave something like that all up to the mere tightness of a nut, when it's as simple as a weld, a raised bump, or curled piece of metal to keep the nut from letting the metal slide out from underneath it.

Let me put it this way, if that strut bar mount can't hold 330 pound in shear (clamp load), it's poorly engineered. You don't design things like this in the manner your describing. Period. The 330 lbs in that example assumes some conditions that would be hard to replicate. So, 330 lbs is generous and is nothing for that clamp load.

Stop and think about it. Look at the fastners that hold your subframes on. Why dont they have the same fastening method you are describing or claim reasoning for? Look at that strut bar. The slot is for tolerancing. Hell, the link even proves that feature would be useless as the strut towers are being pulled apart. Where is your flange even taking load in a case where the bolt ends up in the middle of the slot? It's not.

 

[agressivedsm]

Any progress on these braces? Im in the market for some now. Trying to tighten up for autox season this spring.

 

[FIBA M - EC17PSE]

Any progress on these braces? Im in the market for some now. Trying to tighten up for autox season this spring.

No not at the moment buddy, i do plan to get it finished by the end of jan as the car has been off the road for a few months so that did not help either