Is this a trailing arm bolt?

[Barkychoc]

http://www.margnor-online.co.uk/166f056x400.html

Not sure now I don't have an S, and should not be high tensile??

Not exactly cheap.

[phillpot]

Might be a bit short ?

S Series bolts Wiki reckons four and a quarter then says Steve Heath bolts are five inches cut down to four and a half, guess this gives a longer shank which isn't a bad thing

[greymrj]

Hi Chris, not sure about the class5 high tensile, 'class 5' I think should be GRADE 5 steel and doesn't specifically mean high tensile. I would have been looking for grade 5 class 8.8 high tensile. BS1768 refers to the accuracy and form of the thread and hex as I understand it. Yes it is expensive. Most owners should have an industrial fasteners supplier near them (google 'industrial fasteners' and your postcode?) who can supply EXACTLY what you want, or the next size longer to cut down. My replacements, with nylocks, were a LOT cheaper than that. If you want to go stainless, make absolutely sure it is the nearest equivalent tensile strength.

[mikel003003]

Do trailing arms and shocks use high tensile bolts

[phillpot]

mikel003003 said:

Do trailing arms and shocks use high tensile bolts

Good question

I've pondered this question myself, they are obviously not under tension which would be the normal application for a HT bolt (cylinder head bolt is obvious example) but are subject to shearing forces particularly if the suspension takes a "hard hit" (e.g. hitting a large pot hole)

So is a HT bolt also stronger in this application? Could/would a "normal" bolt shear if hit really hard or fracture/fail with constant use, or would it bend/flex rather than break?

[mikel003003]

Anyone know where Steve heaths stock went ?

[Barkychoc]

http://www.shengltd.com/catalog/

[TurboTony]

Grade 5 , IIRC correctly, is an American definition and an HT bolt equivalent to S grade. 8.8 is a grade applied to metric bolts and equates roughly with S grade unf fasteners. It did when I was a GKN fasteners apprentice anyway! I would be surprised if you could buy a mild steel bolt (classified as a P grade) in this size nowadays. I am sure that someone will be along to confirm or rubbish this!

[Ragtop]

phillpot said:

...So is a HT bolt also stronger in this application? Could/would a "normal" bolt shear if hit really hard or fracture/fail with constant use, or would it bend/flex rather than break?

Shear strength is roughly half the tensile strength. So a high strength bolt is stronger in both tension and shear, broadly in proportion.

Mild steel bolts tend to stretch/bend (at yield strength) long before the finally fail (at tensile strength). This is also a measure of their ductility. High strength bolts tend to have a yield strength much closer to their tensile strength, so although they carry a higher load before yielding, there is less margin between yielding and final failure (and low ductility).

To the topic in question: look at the size of the bolt and compare it with the size of the (16 gauge?) flanges (almost certainly mild steel) that stick out of the chassis and transmit the load from the bolt (high strength or not) - what's going to give first?

This is all static strength based - fatigue is a bit different (but will usually crack the welds first ).

HTH !!

G

[phillpot]

Thanks Graham.

I'm not going to be the one to do it but I reckon stainless would be ok (if you could get 9/16 unf in stainless)for the trailing arms, it is after all basically just a pivot pin?
Shocker mounting bolts on the other hand take an endless "pounding" so maybe wouldn't be so confident using stainless there although it's hard to imagine a solid 1/2" bar breaking?

(I'm thinking "standard" A2 70 stainless here, sure there are better qualities available...at a price!)

[Ragtop]

Strength for strength, stainless behaves much the same as carbon steel under fatigue loading (ie 'constant pounding'). Contrary to popular belief, stainless steels are generally far more ductile than high strength carbon steels, however they can be more susceptible to environmental effects such as stress corrosion cracking which can lead to an apparent 'brittle' fracture. As a general rule, avoid using stainless in applications that are exposed to salt and heat, and you should be okay if you have matching strength.

Learn more at:

http://www.fastenal.com/content/documents/Fastenal...

Graham

[greymrj]

Sorry if I sound unduly cautious again but please be careful. It is certainly possible to get mild steel bolts in this diameter. I was involved in rallying for a good few years. On one occasion the driver was doing some work on 'my' car at home, he couldnt find the original bolts and put mild steel bolts in two suspension mountings. After the next rally I was doing a routine check and found one bolt had sheered off at the thread directly under the base of the nut. I then found the second one and had a devil of a job getting it out as it had distorted under load. If either had failed completely the consequences would have been serious. What risks you take with your life is up to you but is it really worth risking one our lovely cars for a few pence!

[jwoffshore]

M14 is so close in diameter to 9/16" that you may as well use that. I think 110mm length is about right, or maybe 120mm, can't remember right now.

[mikel003003]

So to sum up , the safe option for trailing arms and suspension is high tensile ?

[mikel003003]

Sorry confused , what do I ask for ? Sizes I get and I understand that metric bolts use a number system to determine strength but what about the unf bolts I need for trailing arms ,grade 5 ?

Edited by mikel003003 on Wednesday 22 May 11:33

[mikel003003]

David Gerald stock trailing arm bolts , apparently there 14mm not 9/16