Windshield Fastener Torque Values

Realshelby said:

Well, so much for polycarbonate being so much more crack resistant! Noel, I don't care if you buy a windshield from me or just get another stock one.

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I think polycarbonate is supposed to be significantly more impact resistant than acrylic. The types of forces on these holes would surely be very different than a sudden impact. I can't see any way this screen is going to fall off it's way too secure at least for the time being--six screws and all. And if I stress these fractures they don't budge so I see no way for the entire hole to 'blow out' as it were those radial cracks would have to snap off perpendicular to the fracture lines and that seems nigh to impossible. 26K miles on the bike now and I already have a replacement screen but won't use it until this one gets pitted quite a bit more, or if the cracks continue to lengthen significantly. I'd like to hear if others see this who have the stock screen--perhaps this is a bad batch of polycarbonate. Thank you for the prompt I will show my dealer in case it might be covered under warranty--the local folks seem to be successful more than not with warranty claims. As you say the center screws have a built in stop to prevent over tightening so I don't think they can say I caused this. I can say for sure I haven't gone much if any over 2Nm's by feel.

ncpbmw1953 said:

I think polycarbonate is supposed to be significantly more impact resistant than acrylic. The types of forces on these holes would surely be very different than a sudden impact. I can't see any way this screen is going to fall off it's way too secure at least for the time being--six screws and all. And if I stress these fractures they don't budge so I see no way for the entire hole to 'blow out' as it were those radial cracks would have to snap off perpendicular to the fracture lines and that seems nigh to impossible.

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Polycarbonate is more crack resistant period. It is softer, that is a big part of being more crack resistant. But that is another debate altogether. I doubt your windshield will just "fall off" any time soon. There are other fasteners and the black plastic moulding that will hold also. You already have another screen. What you do with that is up to you.

Realshelby said:

You already have another screen. What you do with that is up to you.

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You mean I don't need to submit a request? Excellent, thanks

Realshelby said:

His words " the WERKS with the chunk knocked out was better than the stock screen"!

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I would take that comment was a massive cube of salt. I'm 6'4" and am ultra satisfied with the dynamic I get out of the stock screen--it's ideal for my ambient temperatures and rain patterns. I'm going to assume the QR is as quiet as the stock screen when the 6'4" rider crouches a little behind the stock screen where ALL wind noise is excluded. It can't get any better than that. I've read enough comments that QR screens for warm/hot weather doesn't quite let enough air at you. Maybe those were just a couple of folks but that was the sense I've gotten. I want some managed air flow for sure. We talked long ago about the issue of getting fully quiet while at the same time getting adequate desired air flow at that time you said something along the lines that it really was nigh to impossible w/o major design changes that I aren't feasible for some reason. So yes while the cost is a little wind noise (I use earplugs, so it's not an issue whatsoever) the benefit is excellent air flow, rain management, and noise reduction, as well as improved aerodynamics from what I read about fuel efficiency effects w/ QR screens. Truth, or fiction?

I looked at what has to break in order for the stock screen to come off from a frontal impact, and I don't see any significant issues. I showed it to one of our certified BMW mechs this morning who told me on no uncertain terms the center holes w/ radial fractures are from over-tightening. He will submit a warranty claim but he feels it will be rejected, and they are excellent at obtaining authorizations for warranty claims where appropriate. His opinion was there there was no safety risk whatsoever. Six screws, two of which even though the one has radial cracks there is a lot of strength still there, but some loss of integrity as well of course. So as a percentage deficit against a screen w/ NO fractures? My guess is that it has maybe 90-95% of the total resistance to coming off its mount in the event of a flying object with enough force to break the screen at the mount holes.

In the example you gave it's hard to say what would happen, but my guess is that this windshield would not have cracked at all--the object depending on its weight and speed of impact would either break the shield off its mount, or deflect off the screen, whereas the acrylic screen took the impact and took out a section of the screen. Which is better? Again, hard to say for sure, it would always be case-specific. It may in some scenarios be better to absorb and shatter versus have something ricochet off the screen upwards and hit the rider's helmet for example. And it may be better to deflect off rather than go essentially THRU the screen and hit the rider in the visor. Both of those scenarios are theoretically possible.

Noel, I didn't set out for this to be a windshield debate. You state what you think and I am 100% happy that you are happy.

Realshelby said:

Noel, I didn't set out for this to be a windshield debate. You state what you think and I am 100% happy that you are happy.

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Hakuna Matata!

How tight? Just making contact!! 2nm is not really even snug - I've stripped one of mine while using a pretty decent torque wrench.

Torque values are the problem. I mentioned that earlier. There are few owners with a torque wrench that could actually measure these very low values accurately. Then, because there is so little force, you may not feel the wrench signal you when you reach correct torque. On other types it just comes down to the low torque values and whether the tool is accurate at that setting.

It is very easy to over torque the windshield fasteners. It will cause problems beyond just stripping threads. There are two types of fasteners in the RT-LC screen. The outer fasteners, that go through the black plastic moulding are threaded fully to the head. The two shoulder type fasteners that go into the screen and are meant to center the screen seem to bottom out but can be threaded a bit more. One mistake that might be made is to use one of the fully threaded fasteners in the centering holes. This would certainly make it easy to overload the screen. Just remember that the shouldered fasteners go in first, then the fully threaded fasteners go in through the moulding in the outer positions.

skibumwi said:

How tight? Just making contact!! 2nm is not really even snug - I've stripped one of mine while using a pretty decent torque wrench.

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For small fasteners like these, I suggest a small beam torque wrench (Nieko or Presa brand on Amazon at ~ $20). There's a certain comfort with the visual confirmation of the load you're applying.

Why do I have one of these wrenches? I need it for installing carbide cutters in my wood planer. If you over torque the fastener, they shatter.

I found the holes in the factory windscreen were very rough. In time this can led to cracking as its a stress point. Smoothing the edges of the hole will reduce the stress factor
A larger drill bit turned by hand can clean up the rough edges
For anyone in Huntington Beach or chino area I have a like new factory shield for a 15RT
FREE but you must pickup as I won't ship
Md80jim@aol.com

Check out this article about small torque wrenches for bicycles... All the new carbon bikes require specific setting that fall with the 3NM and up range..
http://www.bikeradar.com/us/road/gear/article/best-torque-wrench-for-bicycle-grouptest-46517/