Incorrect torque listed in manual ???

[Pete in PA]

Manual (HSM) has 31 ft. lbs. listed for rear brake disc mounting bolts. Listed at at least two places. That can't be right. If I took it that high the bolts would snap.

Front is listed at 14 ft. lbs.

So what is the correct torque?

 

[jmcarruth]

My 2003 Honda Shop Manual says 31 ft/lbs, in two places. Plus it says to use NEW bolts.
BTW, FWIW, my friend's BMW just two days ago had one of her rear disk bolts back out while underway and destroyed the rear caliper on her R1100 and nearly herself.
Lesson learned.

 

[SMSW]

As a check you might look at the size of the bolt (6, 8, 10 mm) and then go to the chart of torques for various sized bolts. If the spec'ed torque is way off the 31, then the latter might be a mistake. On the other hand, if it is a grade 6 or higher bolt (hardened steel) it might sustain higher torque. Just guessing here.

 

[Byron]

A quick search shows the front disc bolts are 6x17 whereas the rear bolts are 8x24.

 

[dwalby]

FWIW, the 1100 uses 8mm bolts (on all 3 disks) and also specs 31 ft-lb for the torque, so you don't have a misprint on the Honda torque value.

When I changed my fronts, the original bolts broke loose with what felt like much less torque than that, if that means anything. I wasn't comfortable with 31 ft-lb into an aluminum wheel either, so I went with something like 24 ft-lb, and haven't seen any of them loosen up yet.

 

[Pete in PA]

FWIW, the 1100 uses 8mm bolts (on all 3 disks) and also specs 31 ft-lb for the torque, so you don't have a misprint on the Honda torque value.

When I changed my fronts, the original bolts broke loose with what felt like much less torque than that, if that means anything. I wasn't comfortable with 31 ft-lb into an aluminum wheel either, so I went with something like 24 ft-lb, and haven't seen any of them loosen up yet.

I went with something less also.
When the caliper mounting bolts are 24 ft. lbs., and other larger bolts are lower, the torque just seems high to me.

With many mistakes found in the HSM through the years, I think this is one of them.

 

[Pete in PA]

Well I went back to it. Glad I can get to those bolts with the bike all together. Just had to put the bike in gear.

Working up from lower torques I made it up to 31 ft lbs. cringing all the way.

I guess I was wrong, 31 is correct. It just feels high.

 

[Byron]

I went with something less also.
When the caliper mounting bolts are 24 ft. lbs., and other larger bolts are lower, the torque just seems high to me.

With many mistakes found in the HSM through the years, I think this is one of them.

Another thing to consider is that the manual is correct when followed completely. That means using new bolts each time the disc is removed. That is because they are a torque to yield bold which means they are supposed to stretch a given amount when installed for the correct holding power.

May of us simply re-use the original bolts. The front caliper mounting bolts are another example. I had mine off many times doing wheel and brake pad changes. Then I felt something strange and back out one of the bolts, it had stretched and would have failed had I tried to get it to the desired torque. I replaced my bolts on that side with ones from a local Ace, that are not torque to yield bolts. There are generic torque table widely available that will give you valid torque values for various bolt types and materials. I guess what I am trying to say is you have to go with what you're comfortable with.

 

[Pete in PA]

That means using new bolts each time the disc is removed. That is because they are a torque to yield bold which means they are supposed to stretch a given amount when installed for the correct holding power.

Has this been verified? I thought we came to the consensus here that it's because new bolts come with lock tight on them from the factory.

 

[W0QNX]

Has this been verified? I thought we came to the consensus here that it's because new bolts come with lock tight on them from the factory.

I don't think they are TTY bolts from my past experience but I haven't had the ST1300 bolts off my bike. I found this bit of info:

"You can identify a torque-to-yield or stretch-style fastener by the narrow shank just below the washer face and before the thread run. A bolt of this design is intended to be installed in the plastic range and cannot be reused after being tightened once"

Since you've just had yours off where they all thread to the head? I never saw a threaded to the head TTY bolt when I was working with fasteners a few years ago.

 

[Byron]

Has this been verified? I thought we came to the consensus here that it's because new bolts come with lock tight on them from the factory.

This is an "assumption" I made based on information in the Honda Service Manual. Take a look in the General Information Chapter 1 Torque Values. Under standard torque values it shows 7 lbf-ft for 6 mm and 16 lbf-ft for 8 mm. However, with regard to the rear disc bolts, 8mm, the manual calls for them to be torqued to 31 lbf-ft. There is also a note under Remarks for Note 6. Note 6 reads "ALOC bolt/screw: replace with new one." So, here is where my assumption comes in; Since the bolts are torqued 15 lbf-ft over standard and they are calling for new bolts to be used my assumption is that the bolts have been over torqued to set the load and thus stretched. Another part of my assumption is that there is a Note 2 that reads "Apply a locking agent to the threads." yet it is not used for these and many other fasteners. So if the bolt was expected to be stretched and replaced every time it must be a torque to yield bolt, otherwise they would have just given it a remark with Note 2 listed instead of Note 6.

I could be wrong but that is my reasoning. As a side note, like a lot of you I inspect and re-use bolts 99.9% of the time as long as there are no visible signs of fatigue or stretch. I have had 1 front caliper mounting bolt stretch after many times in and out. I was lucky and felt something was wrong and removed it to inspect and discovered the stretch that wasn't there before I tried to re-use it.

 

[RaYzerman]

In comparison, the disc bolts are 13 ft. lbs on the FJR, 6 mm. They say use new as well, but I reuse with loctite. If I am going second time around, I will put in new ones every other one. I'm not following the rules either, but it's whatever you're comfortable with.... and yes I would cringe a bit at 31, probably would go with a tad less if it were me (provided you use loctite).

 

[jmcarruth]

This is an "assumption" I made based on information in the Honda Service Manual. Take a look in the General Information Chapter 1 Torque Values. Under standard torque values it shows 7 lbf-ft for 6 mm and 16 lbf-ft for 8 mm. However, with regard to the rear disc bolts, 8mm, the manual calls for them to be torqued to 31 lbf-ft. There is also a note under Remarks for Note 6. Note 6 reads "ALOC bolt/screw: replace with new one." So, here is where my assumption comes in; Since the bolts are torqued 15 lbf-ft over standard and they are calling for new bolts to be used my assumption is that the bolts have been over torqued to set the load and thus stretched. Another part of my assumption is that there is a Note 2 that reads "Apply a locking agent to the threads." yet it is not used for these and many other fasteners. So if the bolt was expected to be stretched and replaced every time it must be a torque to yield bolt, otherwise they would have just given it a remark with Note 2 listed instead of Note 6.

I could be wrong but that is my reasoning. As a side note, like a lot of you I inspect and re-use bolts 99.9% of the time as long as there are no visible signs of fatigue or stretch. I have had 1 front caliper mounting bolt stretch after many times in and out. I was lucky and felt something was wrong and removed it to inspect and discovered the stretch that wasn't there before I tried to re-use it.

If the mfg says to replace a high torque, critical fastener with a new one, I always replace it. This does not apply to the front brake caliper bolts (23 ft/lbs)and the huge rear brake stop bolt (51 ft/lbs) which I have cleaned and reused with Loctite many times. My theory for these bolts is that Honda says to replace them to renew the locking agent that comes on them. No problems in 94k miles on my ST.

 

[Pete in PA]

I think a lot of critical fasteners have the replace recommendation placed on them due to MFG. liability. I torqued those bolts down and loosened them several times. I didn't notice any change. I'm calling it good.

Thanks for all the replies guys. :bow1:

 

[dwalby]

I think a lot of critical fasteners have the replace recommendation placed on them due to MFG. liability.

I suspect there's a lot of truth to that. Its not the bolts themselves that seem special, its the parts they hold on the bike that would cause serious problems if they failed. And I believe people have said that they also come from the factory with a thread locking agent pre-applied to the bolt, so they know its the right amount in the right place. Not 100% sure about that last part, I've never bought new ones for anything yet.

 

[The Dan]

TTY bolts in the automotive industry will say to torque to a number and then add a degree to stretch the bolt.....torque to 40ft and add 90?

 

[dwalby]

TTY bolts in the automotive industry will say to torque to a number and then add a degree to stretch the bolt.....torque to 40ft and add 90?

I was going to mention that earlier, but I wasn't sure if that was always the case. The one time I know for sure that I was using TTY bolts, that was the procedure. Start with an initial light torque to seat it in, followed by a degree spec to stretch the bolt. The bolts also had the reduced diameter between the head and the threads that someone else had mentioned earlier.