bolts harness and head shearing?

[jon hill 3Participant @jonhill3]

Whilst overhauling my front breaks on my old hiace van I noticed the caliper bolts were stamped 11 (presumably a hardness rating).  The caliper mounting bolts were difficult to remove even after gallons of wd40 and eezit.  I was handling these bolts with kid gloves having sheared the heads off some m6 undertray bolts.

This got me wondering does the hardness of the bolts have a relationship to how easily the heads will shear off if rust seized or over torqued?

Also how does one go about selecting appropriate hardness of bolt even if your chosen replacement bolt is attainable?

[duncan webster 1Participant @duncanwebster1]

Bolts are rated on strength, not hardness, although the 2 are related. On a metric bolts you will find 2 sets of numbers separated by a decimal point. The first number gives the UTS in hundreds of MPa, the second multiplied by 10 is yield stress as a percentage of the UTS. Thus a grade 8.8 bolt is 800 MPa UTS, (8 * 10)/100 * 800 = 640 MPa yield. What your 11 means is anyone’s guess.

To keep the Imperialists happy, 1 ton/sq.in is 15.44 MPa, unless you’re an American when it could be 13.8 MPa, as a short ton is 2000 lbs, not 2240 as it should be

[Clive FosterParticipant @clivefoster55965]

Mrs Google suggests that 11 on the head signifies either :-

11 mm diameter thread.

or

“A Grade 11 metric bolt typically refers to a titanium alloy bolt, specifically Grade 11, used in applications requiring excellent corrosion resistance, particularly in chloride environments. While not a standard metric bolt grade in the way 8.8 or 10.9 are, Grade 11 indicates the specific titanium alloy composition.”

First one sounds more likely on a vehicle. Presumably so indicated because the diameter doesn’t match that expected from the head A/F size and skews the maximum safe torque.

Useful little guide from Bolt Depot covers ng both US and Metric markings here :-

https://boltdepot.com/Fastener-Information/Materials-and-Grades/Bolt-Grade-Chart?srsltid=AfmBOooES_-D_z2FQPDiq4EJsPdGeGEMaT-YtPTM2EcscwP3aE9vBbYA

Clive

[Michael GilliganParticipant @michaelgilligan61133]

Further to Clive’s findings … see here:

 

https://henrysautowarehouse.com/bolt-head-grade-strength-identifiers/

MichaelG.

[DC31kParticipant @dc31k]

The comments above apply to commercial bolts, bought as a fastener for use in an assembly of some kind.

It is not a foregone conclusion that an automobile maker (Toyota) would stick to the same nomenclature. When you are making millions of parts, you can invent your own system. Toyota have bolts manufactured for them, to their own specifications. They do not go down the hardware shop and buy an off-the-shelf item.

In principle, it would be possible to identify the grade of the bolt, but you would need detailed technical information from a factory (OEM) guide. That may not be available.

You can see somethig of the kind on a YT channel called Jafromobile – his interest is in Mitsubishi cars, and the factory information from that manufacturer gives details of bolt grade, length, pitch and possibly head a/f.

[Michael GilliganParticipant @michaelgilligan61133]

Ferinfo …

https://forum.ih8mud.com/threads/toyota-oem-bolt-markings.615066/

MichaelG.

[jon hill 3Participant @jonhill3]

Thanks guys for the info. I should have mentioned that the offending bolts were 12mm 1.25 pitch 17mm hex head.

 

Here is a pic of the dimensions, there is no flange to the bolt just a large steel washer.

If anyone knows of a supplier of said bolts Im all ears. Not looking to pay toyota dealership prices though.

[David JuppParticipant @davidjupp51506]

Could be worth checking with one of the many brake part specialist companies.  That way you should get the correct spec.

If in doubt, Toyota prices will be cheaper than a failure due to fitting incorrect part.

[larry phelan 1Participant @larryphelan1]

The correct bolts could be cheaper than a coffin !

[Nick WheelerParticipant @nickwheeler]

I’m a little puzzled by the OP’s problem:

 

he’s worried about caliper bolts(probably M10 or M12) having snapped off several M6 undertray bolts.      It’s not difficult to snap a new M6 bolt by being a bit heavy-handed with a normal length spanner; I’d need a long breaker bar to do that to an M12….

just how expensive are new, OE bolts? One important thing to consider is that car manufacturers often use bolts with non-standard shank diameters/lengths to attach critical components like brake calipers or suspension components. That’s compounded by Japanese standards being different to European ones for things like head sizes.

 

 

I’d have no qualms about replacing the undertray bolts with generic, cheap BZP bolts, but would probably insist on OE for the caliper mounts – especially considering it only needs four.

 

[FulmenParticipant @fulmen]

To answer the OPs questions:

1. Yes, and it’s as simple as you’d expect. Stronger bolts are stronger.

2. You can’t unless you know the actual load. Most times you can swap out a bolt for one of a higher grade, but there are cases where that can be bad too. For instance tractor power couplings tend to use 8.8grade bolts as shear pins, swapping that for a 10.9 or 12.9 could cause real damage.

[Martin ConnellyParticipant @martinconnelly55370]

Calliper bolts are probably classed as critical components since there loss or failure could result in a fatal accident. Some of these critical bolts, when bought new from the manufacturer, come complete with a band of locking compound on the thread. It is possible that these bolts are like that and they seem stuck because of that locking compound. So it may take more torque to get them out than you would expect, but then you should replace them with OEM parts to ensure they are fitted back with the same quality and quantity of locking compound. I think you need more information to be sure you are doing this job correctly. I know about this band of locking compound because I have bought brake servicing kits with new bolts supplied with it as part of the kit.

Martin C

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I’m in agreement with Nick Wheeler, you can’t compare your 6mm undertray bolts with the caliper bolts, as I doubt that the undertray bolts are not even as strong as 8.8 hi tensile bolts. I also strongly recommends getting the correct bolts, as putting the wrong ones in, may invalidate your insurance, especially if your car is involved in an accident, and could cost you more than the proper bolts.

Regards Nick.

[old martParticipant @oldmart]

A lot of Japanese vehicles have a different system of indicating the strength of fasteners, which complies with standards in the USA. That 11 would be similar in strength to 12.9, or 14.9 that we are more familiar with.

I used zinc plated 12.9 bolts and flanged 12.9 nuts on the ball joints of my Fiat Panda and the MOT tester did not like them, and replaced them from the with original Fiat parts from stores and charged me an extra £8, and I got my nuts and bolts back to boot. When later, I replaced the front discs and pads, I replaced the caliper main bolts with the same size Subaru WRX ones and nobody even noticed at later MOT’s.

[bernard towersParticipant @bernardtowers37738]

Id be interested to know the MOT tester with that amount of knowlege of nuts and bolts and which go where, methinks you have been conned. Ex mot tester and motor trade for 50 plus years.

[old martParticipant @oldmart]

I had just replaced both lower wishbones, Macfereson strutts and top bearings and the MOT was at a Fiat dealer, so the tester had seen lots of Pandas. Since the replacement only incurred the cost of the nuts a bolts, I didn’t try arguing about it. He might not have been able to see the 12.9 markings, so they might have been mild steel. As it happened, the Haynes manual bolt torque recommendations for that 8mm bolt in my Panda manual was about 45 ftlbs, an error which I noticed straight away from having been in the aircraft industry, the correct torque was about 12 ftlbs.

[bernard towersParticipant @bernardtowers37738]

Sorry but still say the tester was operating outside his remit.

[bernard towers]

On bernard towers Said:

Sorry but still say the tester was operating outside his remit.

After confessing in #797099 that he doesn’t understand nuts and bolts, Bernhard assumes other MOT-testers are equally remiss, and therefore the one who spotted Old Marts’ change was a con man!

Not a con.  MOT-testers are required to check for unsafe modifications and Old Marts’ chap spotted a change and played it safe.   In contrast, Bernard would have allowed a potentially dangerous vehicle on the road.  And ignorance isn’t a good reason!

I’m not surprised.  No system is perfect, they all depend on competent people doing the job properly.  People cause lots of trouble – they’re vulnerable to knowledge gaps, illness, drink and drugs, memory lapses, dishonesty, negligence, become out-of-date or set in their ways and a few are stuffed with unjustified self-confidence.  In the past, the MOT system also suffered greatly from dishonesty, with certificates given to unroadworthy vehicles for a consideration, and customers billed for unnecessary work.

Oh, and getting away with not knowing relevant facts for 50 years doesn’t make it OK.  Never confuse luck with judgement!

Dave

[jon hill 3]

On jon hill 3 Said

 Not looking to pay toyota dealership prices though.

How much are Toyota dealership prices for these bolts?

[Michael GilliganParticipant @michaelgilligan61133]

https://toyotadirectparts.co.uk/parts/toyota-universal-parts/toyota-front-caliper-bolts/

MichaelG.

[ an interesting discussion so far … but ^^^ ]

[Robert Atkinson 2Participant @robertatkinson2]

I’m with Bernard,

The MOT tester has no remit to fail a vehicle because OEM parts aren’t fitted. Unless the bolts were obviously incorrect i.e. loose or too small for the hole there is nothing in their remit or the MOT testers manual. The only requirement for bolts in the manual is that they are not loose, insecure or missing.
The inspector is certainly not allowed to replace anything on the car or even undo it. They can’t even remove hubcaps from the wheel. If the bolts wer loose the proces is fail car, repair (with permission) and re-test.
The only exception would be if you asked the garage for a pre-mot inspection and autorised any repairs up to £xx.

Robert.

 

[Michael Gilligan]

On Michael Gilligan Said:

https://toyotadirectparts.co.uk/parts/toyota-universal-parts/toyota-front-caliper-bolts/

 

So about four times the cost of a generic equivalent. But that is still only pennies, and not worth worrying about.

 

There are places where an MOT tester should be noting non-standard fasteners; ball joint pinch bolts are one. That is the reason for inspections by disinterested persons. I recovered dozens of cars that had self-disassembled the lower ball joint to knuckle because some one had used an ordinary bolt instead of one with the correct diameter shaft that actually holds the assembly together. The damage and other costs caused are far more than a couple of quid for the correct part….

[Michael Gilligan]

On Michael Gilligan Said:

https://toyotadirectparts.co.uk/parts/toyota-universal-parts/toyota-front-caliper-bolts/

MichaelG.

[ an interesting discussion so far … but ^^^ ]

That seems pretty reasonable to me.

[bernard towersParticipant @bernardtowers37738]

Thanks Robert.

Sod needs to fully understand the role of an MOT tester.

[Robert Atkinson 2Participant @robertatkinson2]

Nick’s example of a suspension knuckle pin replaced by a bolt should be an MOT failure. Thia is becuse it is insecure. However it may be hard to detect. The tester can’t take the pin out so the only chance of detection is if it moves when checking the joint.
The test can’t check everything….

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