Up Selling - Sanity check

bpjthornton

bpjthornton

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Aug 24, 2011
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I as hoping to lean on your wisdom....

In addition to some of my exotic/unreliable/dream/shady (delete as appropriate) motorcycles I have a 2014 BMW GSA 1200. Its a bit of a tractor but its never missed a beat and it fits me like a glove.

Its due for a service in two weeks. Between now and then I was going to change the front discs and pads, save some ££££. I phoned the service centre to update them that the bike no longer needed discs. They were cool with that, but they advised that all the disc bolts should be renewed. I asked if they were stretch bolts, he said no but they recommend fresh bolts with loctite. I have loctite......... but wonder if I'm being 'up-sold'.

Thinking aloud...... the bolts primary work is in shear, guess they have a plain portion which should sit against the discs. The bolts aren't working in tension so replacing them seems silly?

Cheers

Ben
 
bpjthornton said:
I as hoping to lean on your wisdom....

In addition to some of my exotic/unreliable/dream/shady (delete as appropriate) motorcycles I have a 2014 BMW GSA 1200. Its a bit of a tractor but its never missed a beat and it fits me like a glove.

Its due for a service in two weeks. Between now and then I was going to change the front discs and pads, save some ££££. I phoned the service centre to update them that the bike no longer needed discs. They were cool with that, but they advised that all the disc bolts should be renewed. I asked if they were stretch bolts, he said no but they recommend fresh bolts with loctite. I have loctite......... but wonder if I'm being 'up-sold'.

Thinking aloud...... the bolts primary work is in shear, guess they have a plain portion which should sit against the discs. The bolts aren't working in tension so replacing them seems silly?

Cheers

Ben
Click to expand...
Though the force of the disk is perpendicular to the bolt axis, the bolts are not subject to shear force. The force of the rotor is transmitted to the hub through friction, which is generated by the tensile force of the bolts. If the bolts have insufficient tension, the friction will be reduced and the disk will then shear on the bolts- and the bolts will fail quickly.
As to their advice that you change the bolts, I suspect it's more a CYA than a technical necessity. Hardly seems worth an upsell unless the bolts are $10 each, which I suppose they can be from BMW.
 
Take a look and see what AN bolts of that size cost.
 
Does anyone think these bolts are going to sheer off under braking ?!?

Can’t see it myself.

CYA / upsell.

No need to change them IMHO.
 
The bolts have pre-applied "patch-lok" on the assembly line. (A time saving variant on loctite) the bolts are totally reusable. The liability faction demands the absolute same condition be met in the field. The accounting department loves it too.
Sheer & utter bullshit it is.
Liquid (or paste) loctite applied by a mechanic is very much the same result.
I caught our local (MAX BMW, Hampton, NH) pulling the same (worse) shit on a friend who is a bit gullible. Had his GS1150 towed there for a no-start, which they attributed to pitting on the valve seats. It was really only a weak battery. Also, they had removed the transmission, quoted him $3600 for a new transmission, citing input shaft spline wear. The bike had only 21,000 miles, owner made no mention of any drive train related issue.
"Well, all the ones we see need that."
I negotiated paying for the new clutch disc & putting it back together.
Full-on pirates.
 
concours said:
The bolts have pre-applied "patch-lok" on the assembly line. (A time saving variant on loctite) the bolts are totally reusable. The liability faction demands the absolute same condition be met in the field. The accounting department loves it too.
Sheer & utter bullshit it is.
Liquid (or paste) loctite applied by a mechanic is very much the same result.
I caught our local (MAX BMW, Hampton, NH) pulling the same (worse) shit on a friend who is a bit gullible. Had his GS1150 towed there for a no-start, which they attributed to pitting on the valve seats. It was really only a weak battery. Also, they had removed the transmission, quoted him $3600 for a new transmission, citing input shaft spline wear. The bike had only 21,000 miles, owner made no mention of any drive train related issue.
"Well, all the ones we see need that."
I negotiated paying for the new clutch disc & putting it back together.
Full-on pirates.
Click to expand...
That sounds awful. When you find a mechanic that diagnose efficiently and you trust ........ you are onto a winner.
 
" just as well we checked your oil " dosnt get what it used too . ( Engine out and 2 weeks stay in hicksville )

But theyre all trying the ' modern consumer appliance ' trip , these days . Sadly . Modern Logic !

 
bpjthornton said:
I as hoping to lean on your wisdom....

In addition to some of my exotic/unreliable/dream/shady (delete as appropriate) motorcycles I have a 2014 BMW GSA 1200. Its a bit of a tractor but its never missed a beat and it fits me like a glove.

Its due for a service in two weeks. Between now and then I was going to change the front discs and pads, save some ££££. I phoned the service centre to update them that the bike no longer needed discs. They were cool with that, but they advised that all the disc bolts should be renewed. I asked if they were stretch bolts, he said no but they recommend fresh bolts with loctite. I have loctite......... but wonder if I'm being 'up-sold'.

Thinking aloud...... the bolts primary work is in shear, guess they have a plain portion which should sit against the discs. The bolts aren't working in tension so replacing them seems silly?

Cheers

Ben
Click to expand...
The bolts will never fail in shear - but tension?
The only way to really know if they're safe to reuse is to look at the diameter & grade of the bolt together with what torque has been applied.
3'8" (10mm) , even 5/16" (8mm) structural (Gr8.8) torqued to 35ftlb won't need replacing (eg head bolts) but if they have been torqued to the plastic zone (eg Norton crank assembly bolts/studs and big end bolts) should never be reused IMHO.

BTW - they are working in tension.

Cheers
 
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