new doubt about servicin my bike: steering axle

[pioppiny_81]

hello boxxer lovers,
I just finished servicing forks, thanks to your advices.
But I'm stuck in the mud of doubts again,
I discovered that the steering axle top threads are very worn, they seems to be stepped due to loose tightening(?), threads of the sector ring are in the same condition...
What do you suggest me?
put everything back together and don't worry or disassemble the axle from the lower brace and make the new piece on the lathe??

thank you all

[pioppiny_81]

thread is an M28x1.5, correct?

[gspd]

Hard to say without the actual parts in hand.
I'm assuming you're talking about the steering stem.
I've never heard it referred to as a steering axle.
Are the threads damaged but not stripped?
If you have the skill and equipment to easily make a new one on a lathe, by all means do so.

As a BMW master technician the only possible answer is to replace any steering component that has even the slightest wear to avoid instant death (and lawsuits). Period. There is no other option. Cost should never be a consideration. This is what you are taught at 'BMW' school.

Another possible viable real world (of the not so rich and famous) solution would be to wrap a bit of teflon tape around it, torque and adjust everything correctly, and see if it lasts another 20 or 30 years.

Only your mechanical knowledge, experience, budget, and planned usage can determine which is right for you.

[Rob Frankham]

Like GSPD, I'm working on the assumption that you are referring to the steering stem... this isn't a judgmental comment, I just wish to ensure we're talking about the same thing.

The steel stem can be pressed out of the lower fork yoke (triple tree in american) and, while there is no reason why it is impossible to make up a replacement, be aware that the stem is located in the yoke by a quite fine spline. The tightmess of the joint and the integrity of the steering is dependant on that spline. I'm no machinist but I can't see how that would be replicated on a lathe without special tooling. To my mind, a better answer would be to source a replacement bottom yoke/stem assembly with an in tact thread. It should be possible to source a pre-used lower yoke assembly from one of the various dealers without too much expense or trouble.

Rob

[pioppiny_81]

yes I'm referring to the steering stem, sorry for my English,
the joint between steel stem and aluminium lower yoke is a simple interference fitment, once disassembled with a press and heat, I was just thinking of measuring the male part on the axle (with micrometer) and having this simple part done by the lathe(not by myself).
My doubt is only the type of steel to use.

I'm afraid buying a new steering yoke might have the same problem

[Rob Frankham]

To be honest, I've never seen a yoke with the extent of damage to the thread that is evident in your photo... I don't think you'd ever see anything like that again, especially if you were buying from a reputable second hand parts specialist.

As I said before, the stem is a splined fit into the aluminium yoke and I doubt that there is a simple way of reproducing it with a lathe. Granted a good machinist could probably match it but that would probably be expensive. To illustrate, below is a picture of the yoke on an accident damaged ('81) R100RS where the steering stem has been pulled through the yoke. You can clearly see the splines.

9-4-04-lower yoke.jpg (213.71 KiB) Viewed 642 times

Rob

[gspd]

I doubt that there is a simple way of reproducing it with a lathe. Granted a good machinist could probably match it but that would probably be expensive.

+1
Gotta agree with RobF on this one.
Probably cheaper to buy one than to have one custom made.

I've seen a lower triple clamp break from a bad crash, but I've never seen the splines pull out like that.
I would have assumed that the top threads would have let go before pulling the stem up through the lower triple clamp.

It's hard to determine the actual location and structural 'torquability' of those threads from the overly magnified pic.
Depending on the model there are a lot of threads holding that assembly together and they are not terribly stressed in normal use once the play is set and the 2 nuts are locked together sandwiching the upper triple clamp. (Not sure of the year and model)

New nut(s) might solve the issue if you're on a budget. The worse that can happen is that the threads won't hold and you'll know that after a few rough road rides. If the thought of trying that scares you, I'd suggest looking for a used triple clamp (or a new one If cost is no object).

[melville]

I doubt that there is a simple way of reproducing it with a lathe. Granted a good machinist could probably match it but that would probably be expensive.

+1
Gotta agree with RobF on this one.
Probably cheaper to buy one than to have one custom made.

I've seen a lower triple clamp break from a bad crash, but I've never seen the splines pull out like that.
I would have assumed that the top threads would have let go before pulling the stem up through the lower triple clamp.

It's hard to determine the actual location and structural 'torquability' of those threads from the overly magnified pic.
Depending on the model there are a lot of threads holding that assembly together and they are not terribly stressed in normal use once the play is set and the 2 nuts are locked together sandwiching the upper triple clamp. (Not sure of the year and model)

New nut(s) might solve the issue if you're on a budget. The worse that can happen is that the threads won't hold and you'll know that after a few rough road rides. If the thought of trying that scares you, I'd suggest looking for a used triple clamp (or a new one If cost is no object).

Yeah, I'm kinda with the 'new nuts' plan. You'll have to buy them anyway, so get them first and see how they feel threading on to your current stem. I have a couple out of the bike right now and none of them look like your part, but I'm not using the electron microscope that you're using.

[jackonz]

Looking at the threads I would say that the nut has been loose and fretting, making a new one would be very expensive and then machining lining up the slot in the shaft so the steering lock works will be a challenge, as for material your looking at 4140 steel.

I could make one easily but getting the spline right involves knowing the original OD BMW made the splined section to then cutting the splines, too small or too big result disaster.

Best bet is a used one.

[pioppiny_81]

watching used parts I found this

Screenshot_2023-02-03-06-56-14-645_it.subito.jpg (1.23 MiB) Viewed 618 times

Screenshot_2023-02-03-06-56-25-334_it.subito.jpg (790.93 KiB) Viewed 618 times

so I thought that there isn't any spline but could be not clear from the photo.
Mumble mumble, maybe you're right, entire operation don't worth the money
In the end I can try to find something used, here in Italy is not simple , I have a few ads to choose from, have you got some European websites to suggest me?

thank you all so much for your time!