ST1300 Brake Disc / Rotor - Bolt Torque Query

[jfheath]

Can anyone with a more up to date shop manual confirm or correct this information please.

Front Brake Disc bolts 20Nm
Rear Brake Disc bolts 42Nm

Thank you.

Reason for asking

In January I placed an order for a complete set of OEM brake discs and associated bolts. Sometime this Summer, I intended to replace all 3 discs. I had assumed that there would be short supply, so parts would have to wait for availability from January, and importing stuff into the UK is now no longer the easy overnight process that it used to be. I reckoned that that would give them plenty of time to get here. As it turned out, they arrived the day after ordering them !​

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'Sometime in the Summer' turned out to be today, at least for the front discs. I had armed myself with everything that I could possible need to undo stubborn hex-socket bolts. Penetrating oil, micro blow lamp, hot water, grinding paste, Good fitting hex and torx drivers. And this morning I went into the garage fully prepared to have the 6th bolt on each wheel refuse to budge without turning the hex socket into a perfect circle. ​

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All of the bolts came out easily. Absolutely no hassle at all. This has got to be a first - so I spent the time that I had saved thoroughly cleaning the wheel since I could now get to the areas that haven't been touched for the last 9 years.​

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Then to put it all back together again. 20Nm for the the 6 x front brake disc mounting bolts ? Really ? Is that all ? The rear mounting bolts are 42Nm. ​

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Ok. 20Nm it is. It felt about right compared to how easily they unfastened. But why then is 42Nm required for the rear ones. I've checked that all 3 places in the manual give the same value - which usually reveals any discrepancy - ie The General Information Torque values, the start of the chapter 15, and the text in Chapter 15. ​

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The diagram in Ch 15 gives 22Nm for the front disc bolts - so there is a small discrepancy there, but I have found the diagrams less reliable for labelling parts.​

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I am using a UK Shop manual for 2003/2004 - the A4 Addendum (CH28) has another torque setting table which gives the same info.​

 

[DavidR8]

My factory manual has the same torque specs that you list; 20 Nm front, 42 Nm rear.

 

[Esti1300]

Hey John,

Checked my manual. It’s also the 2003 version and I get the same info you’re getting.
I also have a Clymer manual that was published in 2011 and has the exact same torque values as the SM.
Is it possible that the reason for the different values is the fact that the front disks are floating?

 

[SupraSabre]

Although, not the disk bolts, here's the others...

 

[SMSW]

My HSM for 2003 - 2011 shows the same torques, 20 and 42 nm.

 

[jfheath]

Thanks all. I guess 20 is correct. It sure felt to be around that when I was undoing the old ones.
It just seemed odd.

 

[Mr.E]

Read your scribe a few times John and excuse me if I've missed the reason - but why are you changing all 3 discs, are they all below the min thickness?

 

[ST1100Y]

20Nm for the the 6 x front brake disc mounting bolts ? Really ? Is that all ? The rear mounting bolts are 42Nm.

The wheels are cast aluminum, rear has more meat at the hub, bolts are also secured with medium grade Loctite...

 

[jfheath]

Read your scribe a few times John and excuse me if I've missed the reason - but why are you changing all 3 discs, are they all below the min thickness?

Now - there is a question.

The surface on all of them was looking rather pitted and worn out, and there was a significant lip on the outside edge - so I got the micrometer out and got a set ordered.
Always awkward to read this when it is still attached to the bike - you cannot remove it because of the lip. Before fitting, I checked again - 'cos I wanted to know what thickness the discs were when brand new. My reading turned out to be a tad out !

For Info

Front Min Thickness is 4mm. Brand new is 5mm. Mine were 4.3mm. So 70% of life used.
Rear Min Tickness is 6mm. Brand new is 7.2mm Mine were 6.3mm - so 75% of life used.

So they would have lasted a couple more seasons, but although I knew the above, before I fitted them, I decided to go ahead anyway. The surface of the old discs is quite scored and pitted, and on some days braking was quite dramatic and starting to catch me out. ie I expect an increase in braking power in proportion to how hard I squeeze the lever - and the last couple of rides, the 'little bit more' at the lever was resulting in helmet banging.

Coupled to that, my flexibility for working on the bike is getting more and more questionable by the day, and as I my total riding days are increasing by the day, it is getting all too apparent that the total riding days left (whatever that number may be) is reducing. I'd bought them, they will outlive me and I'd rather reap as much of the benefits of having them myself .

 

[Larry Fine]

Always awkward to read this when it is still attached to the bike - you cannot remove it because of the lip.

Can you count the number of knob turns required to get it off the rotor, screw it back in the same number of turns, then read it?

 

[Mr.E]

Now - there is a question.

I use a Dial Vernier but either way, they don't give us much between brand new & worn out!

Share your pain with getting these low down jobs done around the bike, the getting down isn't a problem, it's the getting back up that's difficult!

 

[jfheath]

The rear went on easily yesterday. Goodness, those rear disc mounting bolts were tight, and there was a lot of corrosion between the shoulder and the alloy. Thankfully, the threads were all OK. I wondered about putting some a smear of MolyPaste on the shoulder of the new bolts, its Ok on the back of brake pads, but decided that the new bolts wouldn't be seeing the light of day again, so didn't bother.

I used a technique that Larry @Igofar gave me when I was undoing my fork bolts. I'd never come across it before: When I got to the point where I felt that I was applying enough force. I stopped adding any more and just maintained the same pressure. The bolt started moving after a short delay.

There was also a good bit of build up between the wheel hub and the disc. A light sanding got rid of most of it, but there seemed to be some filling compound around the thread hole. As if something had been put there to allow the disc to clamp down on it - but it wasn't spread out enough for that. It could have been thread locking compound that had squeezed out, but I've never seen that before with Hondas ALOC bolts.

I smoothed it down and the new disc mounted perfectly OK.

Pushing in the outer pistons was rather easier than I had expected. My outer pistons normally offer a lot of resistance. Even when the SMC was brand new and everything had been flushed out and cleaned up. I mean - it was possible to press them both in at the same time. I'd normally have to see-saw them. Just an observation.

The SMC locks the back wheel easily, and releases it again instantly.

I remembered to syringe some fluid out of the reservoir, and forgot how difficult it is to recover the reservoir mounting bolt when it pin-balls its way towards the ground, pinging off battery housing, suspension coils, master cylinder, swing arm and brake pipes, and various other components, but stopping somwhere short of actually reaching the ground. It sounded like it was tucked inside the lower cowl, but I couldn't find it. Putting it on the side stand eventually nudged it from its hiding place, but not before I'd had the side panels and the lower fairing off to try to find it.

I'd had enough yesterday and left the garage before completing my normal checks. The large printed sign that says "Caliper Brackets are not tight" was stuck onto the screen to remind me not to ride off on it.

I need to go over everything that I have done, make sure it is all secured, that the brakes are working as they should and then go for a test ride. Always exciting, as it's downhill from here. The brand new pads are SSSShhhhh-ing on the new discs. They always do. I don't mind about that. As long as they are not doing it when I ride it back up the drive.