coil over suspension

[Art Burtt]

If you are using a coil over suspension do not use grade 8 bolts on the lower
shock mount. If you hit a big pothole like I did last night the grade 8 bolt will snap right off. Use grade 5 or 7.

[Double Venom]

OK,
DAMN, who did I promise the lower shock spacers to?
Onefastmustang? Send me your address (again) I have them ready to go!
DV

[bobcowan]

A grade 8 is extremly strong in tension, and can hold a lot of clamping force. But, that strength comes at a price. IIRC, that bolt is in single shear. Failure is inevitable.

In Carroll Smith's book "Nuts, Bolts, Fastner, and Plumbing Handbook", he states, "There is no place on a race car for a grade 8 bolt". I don't agree with that. But, I do believe there are very few places for a grade 8.

[lal Naja]

Originally Posted by Art Burtt

If you are using a coil over suspension do not use grade 8 bolts on the lower
shock mount. If you hit a big pothole like I did last night the grade 8 bolt will snap right off. Use grade 5 or 7.

What about the upper coil mount? Would not both be subject to an equal and opposite reaction?

Unfortunately I have no idea what Jaguar used as bolts for the dual Coilover shock mounts on the IRS. As the length of bolt that I need is dirfferent to the original Jag, I was thinking of machining custom Stainless steel shafts for both the upper and lower coilover mounts. Anyone have thoughts on this.

Thanks,

Arthur

[FWB]

i see scary things here on this thread......


1) you should definitely be using grade 8 bolts on you suspension. with that being said, the correct ones that is,,,,,,the point of shear should not be where any threads are, it should be on a shoulder, a spacer should be used to create a crush or pull on the bolt equal to the downward force.

2) stainless hardware, is the weakest.....look at strengths. you will kill yourself with stainless bolts on your suspension. if designing a suspension is something you have never done...please please please consult with someone who has,.


jus' sayin'

[lal Naja]

Originally Posted by FWB

i see scary things here on this thread......


1) you should definitely be using grade 8 bolts on you suspension. with that being said, the correct ones that is,,,,,,the point of shear should not be where any threads are, it should be on a shoulder, a spacer should be used to create a crush or pull on the bolt equal to the downward force.

2) stainless hardware, is the weakest.....look at strengths. you will kill yourself with stainless bolts on your suspension. if designing a suspension is something you have never done...please please please consult with someone who has,.


jus' sayin'

Fully agree with your comments. NO shear on threads. Would you please explain further your comment "it should be on a shoulder, a spacer should be used to create a crush or pull on the bolt equal to the downward force."

This is how I'm understanding your advice above. If I'm seeing it wrong please comment.

Jag lower control arm has a cross-tube running through it front to back, through which a 5/8" shouldered shaft runs, on which the twin coil-over shocks perch with 3/8" nuts and fender style washers compressing it all together.

My shocks have Poly bushes with a tubular metal sleeve through the bushes. So starting at one end (say Front) of the assembly:
3/8" nut & 3/8" ID flat (fender type) washer about 1 1/8" OD, shock, 5/8" ID flat washer, Jag cross-tube, 5/8" flat washer, shock, flat washer & nut.
When the front & back 3/8" nuts are torqued down the washers will be compressed against the shoulders of the 5/8" shaft and compressing the poly to a point that the inner metal sleeves are in crush.

Jaguar engineers would have figured out the crush equal to the downward force. Original shocks had rubber bushed so getting the rubber to move out of the way to preload the sleeves would have been no problem.

As my shocks are not Jag and bushes are poly, I have to accept that the shock producer designed the shock perch sleeves to be the right length so when torqued down the Poly will yield and all is okay. So I have to figure out how to make my 5/8" shouldered shafts the correct length.

Is my understanding anywhere near sensible engineering?

Some time ago I replaced the rear shocks on my Jeep Wrangler and I was surprised to see that the upper bolts were only 3/8" or 7/16" diameter. So thinking that the Jeep experienced a lot more off road use and the bolts holding the shocks performed fine, I considered that 5/8" stainless on the Cobra should suffice. I don't have the smarts to calculate the Kinetic impact at these sheer points on my IRS, so I love hearing from guys like you that can figure this stuff out.

Whatever I end up using has to be custom made for my application. So all advice is appreciated so I don't have to have do-overs.

Thanks

Arthur

[jagrolet]

This arguement over bolts,nuts,lock washers,fittings is as old as the hills.
I started driving "open wheel" competion cars in the late 60"s early 70"s,when you really had to rely on military surplus to get real quality fastners.

Now,the aftermarket (ARP) sells new quality products at moderate pricing.Alot of design methods and criteria were of individual thinking,and fastener useage was like a "black art" amongst the race car people. The people that i was affliated with,were of the aircraft bent,so we followed those disciplines,witch i think to this day are tits.

I have to say that Caroll Smith"s book Prepare To Win,is THE ONLY book to be used in the prepping of any high performance car.Also,Tune to Win and his book on hardware are fantastic,and should be decision makers for everyone.If only he wrote about women! And Engineer to Win,in my opinion,is the first and last word on all issues on anything that makes noise,is loud,goes fast,runs on some type of fuel,gets hot,and puts a grin on you.Whooa,maybe he did write about women.


Anyhow,take Caroll"s advice,on design and applications,and you will not go wrong.






0












0)

[FWB]

while i can't comment on a jag i was referring to coil over shocks. the bottom mount is usually an eyelet in most applications. the bolt runs through a sleeve the force is mostly downward. a bolt that is fully threaded is the wrong bolt to use, a bolt that is loose where the nut is will shear there. to compensate by using a lower strength fastener thinking it will bend instead of break is dangerous. any fastener for brakes , suspension or load bearing in the engine should be carbon steel, not stainless,,, stainless has wonderful anti corrosive properties but absolutely lousy strength. lets take a 1\2 inch bolt for instance a good quality carbon steel bolt will have in the neighborhood of 170,000 psi strength while its comparable stainless 18-8 ,304 or even 316 will have up to 40% less strength in fact if you check fastener suppliers stainless hardware doesn't carry ratings like other bolts......why.....
because a grade 3 carbon steel bolt will out perform the stainless one.
stainless for your intake manifold at 30 ft\lbs fine works for me but stainless on the suspension.....good luck.....grade 8 bolts are not all the same either it is a standard to be met to achieve the grade designation. some fasteners far exceed the rating.

a good place to see some info is actually on McMaster-Carr's web site they do show strengths of fasteners, as a comparison.

[FWB]

here is a chart showing yield strengths and tensile strengths.


Hex Bolt Identification Guide - Engineers Edge

[bobcowan]

Originally Posted by FWB

i see scary things here on this thread......


1) you should definitely be using grade 8 bolts on you suspension. with that being said, the correct ones that is,,,,,,the point of shear should not be where any threads are, it should be on a shoulder, a spacer should be used to create a crush or pull on the bolt equal to the downward force.

2) stainless hardware, is the weakest.....look at strengths. you will kill yourself with stainless bolts on your suspension. if designing a suspension is something you have never done...please please please consult with someone who has,.


jus' sayin'

Both of these statements are false.

Just because it is a suspension component, does not mean it must be a grade 8 fastner. Go back and read the original post. You should choose the proper fastner for the specific application. A "one size fits all" way of thinking will cause problems. Using a grade 8 bolt in a single shear application is not a good idea; it will flex, and eventually fracture.

Stainless hardware is not the weakest. Ungraded fastners are the weakest, regardless of the material they are made of. You can buy grade 8 SS, and they have the same strength as every other grade 8 fastner.

As said above more than once, if you have not read Carroll Smith's book(s), you should. You'll find it very enlightening. At least, I did.

[lal Naja]

Originally Posted by Art Burtt

If you are using a coil over suspension do not use grade 8 bolts on the lower
shock mount. If you hit a big pothole like I did last night the grade 8 bolt will snap right off. Use grade 5 or 7.

Art, Did this happen on front suspension.?

Have you had a chance to inspect the bolt on the other side and can you see any visual stress.

Do your shocks have Heim Joints or poly bushes?

Hope you did'nt do any damage to the car.

Arthur

[tcrist]

Art,
How long and how many miles on this suspension with the grade 8 bolts before one broke?

[Scoober]

In high vibration or thermal areas the harder the material(higher grade) the less elastic it is and the more prone it is to fracture in those situations. The softer materials are more stetchy(for lack of a better term) and can accomodate more vibration and thermal changes. Most people that work on cars have put too much torque on a fastener and have had it break at some point or another. This has stretched the bolt beyond its elastic limit, most often under the head or thread area(smallest diameter) and you will see it neck down a bit. In shear type of assemblies the part hold the loads and the bolts are used to create surface friction between the parts, never use a bolt as a pin in a shear assembly!! lugs are holding the wheel to the hub and create high friction rate between the two surfaces, lugs too loose and you will shear the lugs off under acceleration or braking. All fasteners stretch to create clamp load and there has to be the right amount of stretch to allow for expansion under loads or if there is contraction like in gaskets.

[FWB]

Originally Posted by bobcowan

Both of these statements are false.

Just because it is a suspension component, does not mean it must be a grade 8 fastner. Go back and read the original post. You should choose the proper fastner for the specific application. A "one size fits all" way of thinking will cause problems. Using a grade 8 bolt in a single shear application is not a good idea; it will flex, and eventually fracture.

Stainless hardware is not the weakest. Ungraded fastners are the weakest, regardless of the material they are made of. You can buy grade 8 SS, and they have the same strength as every other grade 8 fastner.

As said above more than once, if you have not read Carroll Smith's book(s), you should. You'll find it very enlightening. At least, I did.

his book is written 40 years ago and the whole world including metals has changed along with it.....you state exceptions in which i too agree on. it sounds as if we do agree but you can't resist a good argument if though the talking points are identical.

i think scoober has stated it as it should be.......nuf said....

[Ralphy]

We just had a situation here in ATL. A Decorative railing on a overpass in downtown Atlanta fell onto I75 North late Saturday. Either the bolts were made of suspicious material or they didn't use enough fasteners. They removed the entire railing last night from the 7 year old bridge. Luckily no one was hurt.

EXCLUSIVE: Moments After 17th Street Bridge Collapsed

Maybe caused of a single bolt.
Officials: Bolt May Have Caused Fence Collapse

[Art Burtt]

About 3,600 miles

[Art Burtt]

I called Heidts and ordered a new bolt with lock nut and a new aluminum spacer. They sent me the wrong bolt (too large) and a lock nut with fine threads, the bolt has coarse threads, plus the spacer was wrong because the hole down the center of it was too large and it was steel instead of aluminum. Went to Tractor Supply and got the right bolts and nuts (I changed both sides) and I made a spacer out of large washers. I'm still hoping they can send me the correct spacer as it has a tapered end which fits the mount on the Mustang 8.8 rear.

[tcrist]

Art,
Check with ProShocks. They might have the correct spacer.

edit:
I looked at their web sight and do not see spacers mentioned. DV was going to send "onefastmustang" a spacer. You might want to check with him to see if he has any more or knows where Don got them.

[Bobcat]

Why don`t you use AN hardware ( bolts ) on the shocks/mounts ? Really not that expensive , around $2 to $3 /bolt .... it`s what the NASCAR teams use . A friend on mine used to be a team manager for an IMSA pro team and that`s all they use on the suspensions . When I checked my car , I found several things I needed to change ... and one was the grip length of the bolt ( unthreaded part ) was too short and part of the threads were on the shock mount support bracket . In addition , since I was changing to competition shocks with spherical eye mounts , this can and will put a more concentrated load on the bolt than a standard shock mount .
On your spacers , I had a machine shop machine exactly what I needed out of some thick wall tubing .... everyone`s spacers were either too long or too short .
Since I track the car some , this is something that helps me sleep a little better .
If interested , I can give you the company in FL I got my hardware from .