Lower strut bolts

[jbuckl]

My arm is pretty good but after years working on CAT scanners that produce up to 26G of centrifugal force at full speed I always use a torque wrench!

Trunt, Sorry, no knowledge of cat scanners.

Automotive & Internal Combustion Engines mainly.

Since calibration, my arm has only broken fasteners that were going to break with or without a torque wrench. Aka Siezed or weak.

Have been involved with heavy lifting though . Some fasteners required geared torque wrenches…. But not that many…. Most just podgers and hammers.

What is the point that’s being made about said cat scanners?

probably the most finicky engine fastener was the kamax through bolt. (K series)

only went to yield when the engine was hot.

great design …. Mostly fully mis-understood.

[trunt]

A Cat scanner rotates up to 4 times a second last I was working, there are many heavy components spinning and some of the items on the peripheral are pulling up to 26G at full speed, so you had better have bolted it down correctly - not only so they don't come loose but also so you don't then get sued! I hasten to add that I have never heard of anything falling off, of course they are designed to eliminate any risk, even cooling fans are orientated so that the gyro effects do not put the bearings under undue stress. I was furnished with 5 different torque wrenches, all calibrated annually, all closely monitored so if one came back out of calibration you had to go back to all the jobs you used it on and recheck the torque until 5 came up OK.

But yes after years of tightening stuff up I also have the mechanical sympathy to be able to feel when things are not right.

[APS]

Today I have checked all the other bolts I have used. They were all purchased from different suppliers as they all were not available from just one.

The bolts from CW were the kit of 8 bolts for the strut to vertical link, all marked ARB T. so I have to replace the upper bolts too.


The other bolts from CW like the caliper lower bolt and the track control arm bolts are marked with 3 dashes which I think is grade 5 and should be ok.


The only other bolts I have concerns with are the 4 bolts that hold the brake discs to the hubs. These appear unmarked as to what tensile strength they are. These I have already torqued up ok to 34lb. Should I replace them ?
These came from a supplier with similar name to this forum.

[marshman]

HA! Massive can of worms.

Something at the back of my mind made me remember some "stuff" from my apprenticeship days. The 3 and 6 dash markings on imperial bolts is not the only "system" that was used. I have done some more digging and there are also "letter" grades which were used. BS1083 is the old British Standard.

This webpage has a good summary.

https://www.bolts.co.uk/bolt-grade-strengths/

To cut a long story short, imperial bolts have been stamped with a single letter on the head (in addition to the makers initials).

"S" was used on UNC and UNF bolts to indicate "high tensile". It seems from what I can see on your pictures that you bolts are all "S" which should be OK, however you have already proved that one such bolt didn't seem to be up to scratch. If you have another ARB "S" spare you could test it like I did to see if it was a one off or is a batch quality issue.

So my comment earlier that it was not a high tensile bolt was wrong - sorry (have edited my post)


I think my inclination would be to replace the ARB "S" bolts. The ones on the Disc assembly appear to be marked "S", also look to be unplated (tick) and are from a different source and so probably OK.

Looking through the new bolts I have they are all marked in the "modern" way - i.e. 3 dashes on the imperial ones and 8.8 on the metric.

[APS]

The bolts on the discs are marked S and I have these torqued to 34lb, I think these were 3/8". The ones from CW are marked T and the 3/8" lowe strut one failed about 30lb. The larger 7/16 upper strut T bolt is currently torqued to 45lb but consensus here seems to suggest I should torque it to 65lb.

I would have thought T is higher strength than S, but that might be wrong or reverse logic.

CW is checking with suppliers, ARB for view on their T bolt and for a supplier of grade 5 for same size bolts.

Waiting for CW feedback before I go and purchase or change any bolts. But yeah big can of worms.

[APS]

Ordered replacement bolts from another trusted stag parts supplier. Upper and lower strut bolts both sides, caliper upper long and lower short bolts.

The bolts arrived and the strut bolts are marked with the three dashes meaning high tensile, happy.
The caliper bolts supplied are same as before, ARB T . Not so happy.

Also the unthreaded section was somewhat shorter, should this be an issue ?

So yesterday I ordered bolts from supplier Spalding Fasteners. They arrived today, all with the three dashes and much cheaper than the stag suppliers, so super happy.

Will get back to the car tomorrow.

[APS]

Got all the bolts buttoned up, then remembered the suggestion of calibrating my torque wrench.

Marked up the 12 inch mark on the handle, weighed some weights at about 32lb on bathroom scales and set the wrench at 35lb. Clamped the 1/2 inch drive in the vice and suspended the weight by a cord at the mark on the handle. Nothing happened. Pushed down a little and the wrench clicked. So reset wrench at 33lb. Still good, a little touch and it clicked.
Took the weight up to about 50lb, same process as before and I am really surprised at how accurate the wrench was.

Still I was still hesitant with torquing the first few bolts, but no drama like before. Went round and torqued up all the bolts on the suspension and steering without any issues. Almost finished now. Just need to bleed the brakes.