MB R129 Brake Caliper bolts - Replace or re-use ?

[pcn1]

Maybe one for the Mercedes guys here.

I have a 1998 SL 320. Just in the process of fitting new front discs and pads plus new pins and spring plates.
Ive read on another forum that MB recommned you fit new calpier fixing bolts after removal to fit new discs. Ive never come across this in any other car Ive done and I usually have access to the servcie manuals.
I know what a stretch bolt is, a single use item. My local MB main dealer is meant to be re-opening their parts department on wednesday, and Ive got no problem buying new bolts if that the correct thing to do. Unfortunatly there is no Haynes book for the R129 I can refer too.

My policy is, if a part is perfectly servicable then use it, if it needs to be replaced then do so. But I do get a little suspcious if this is just a cash grab when you put your car in for servicing with MB !

Any thoughts ?

Cheers

[GreenV8S]

I don't know anything about that car but I'd expect to find simple high tensile bolts. In that case I see no reason to replace them.
If you can find tightening instructions anywhere, that would make it obvious whether they are stretch bolts.

[Matt_E_Mulsion]

I'd personally just stick them back in and make sure they are sufficiently tight.

[Krikkit]

I assume you have the torque settings? Stretch bolts are usually angle-tightened as the last stage in my experience.

[pcn1]

Krikkit said:

I assume you have the torque settings? Stretch bolts are usually angle-tightened as the last stage in my experience.

I still need to find out the torque setting. If I buy new bolts at the dealer I'll ask them the correct setting.

[DVandrews]

It may be that the bolts are patchlocked with a locking compound and this may be the reasoning behind replacement. If there are obvious signs of locking compound residue on the threads, then that would confirm it. If that is the case, clean the threads and apply soft loctite and you should be good to go.

Dave

[GreenV8S]

pcn1 said:

If I buy new bolts at the dealer I'll ask them the correct setting.

How about asking them anyway? If they quote a simple torque, you'll know they aren't stretch bolts.

[Chris32345]

Just do them tight with. 2/8 ratchet

I see no reason to torque something like these

Suspension and engine parts yes Because they move and have extreme heat cycle's
But brake caliper bolts?

[PositronicRay]

When I purchased Pagids they came with the bolts.

[pcn1]

PositronicRay said:

When I purchased Pagids they came with the bolts.

I bought Brembo disc's and pads from Euro's. No bolts supplied in the box !

[Matt_E_Mulsion]

Chris32345 said:

Just do them tight with. 2/8 ratchet

I see no reason to torque something like these

Suspension and engine parts yes Because they move and have extreme heat cycle's
But brake caliper bolts?

I would say that it is pretty important to ensure that any bolts on the braking system are done up properly because the results of failure could be catastrophic.

Within the last week alone I've seen a Land Rover where a brake caliper bolt has fallen out (it had brake work done a couple of months ago), which allowed the caliper to open up and it snapped the a brake pipe clean off flush with the union that goes into the caliper. The result - significantly reduced braking effort and fluid ejecting itself all over the floor.

If you aren't a professional and don't know how tight to do a fastener up, use the correct torque figure on a suitable torque wrench and you won't go far wrong.

[HustleRussell]

Chris32345 said:

Just do them tight with. 2/8 ratchet

Two eighths

[Chris32345]

HustleRussell said:

Two eighths

Typo 3/8

[Krikkit]

Chris32345 said:

Just do them tight with. 3/8 ratchet

I see no reason to torque something like these

Suspension and engine parts yes Because they move and have extreme heat cycle's
But brake caliper bolts?

So the torque setting isn't important on a part that gets constant heat cycles (to hundreds of degrees if heavily used), constant vibration and holds on a critical safety component? Are you mad?

[pcn1]

Just called my local (Slough) MB dealer who told me last week the parts department would open to day.
Seems they changed their minds, sales and service are open but not the parts counter until further notice.

[PositronicRay]

pcn1 said:

PositronicRay said:

When I purchased Pagids they came with the bolts.

I bought Brembo disc's and pads from Euro's. No bolts supplied in the box !

No not with pads, they came with the discs.
You don't need to take the calipers off for a pad change.

[Chris32345]

Krikkit said:

So the torque setting isn't important on a part that gets constant heat cycles (to hundreds of degrees if heavily used), constant vibration and holds on a critical safety component? Are you mad?

Most garage's don't torque a brake caliper they just tighten then up with a ratchet

The exact torque isnt important as long as it tight

And most of the heat is in the brake pads and discs not the caliper and certainly not the bolts fixing then

[The Wookie]

There’s an argument for saying that if you can reach the spec tightening torque without them feeling like they’re stretching but if MB recommends replacing them then I’d suggest replacing them.

It is only a few quid after all.

I’ve experienced cheap snotty bolts on a Mini before that one wouldn’t have expected to be stretch items by the spec given, but they elongated at well below the tightening torque and came loose with a clonking caliper within a few dozen miles, before I’d even got to the dealer when they reopened the following Monday.

[GreenV8S]

The Wookie said:

I’ve experienced cheap snotty bolts

That seems to be an argument for keeping the OEM bolts and not replacing them for who-know-what aftermarket ones you found in a box.

[The Wookie]

GreenV8S said:

That seems to be an argument for keeping the OEM bolts and not replacing them for who-know-what aftermarket ones you found in a box.

Those were the OEM ones that I removed when I was replacing the disks!