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Old 12-03-2012, 07:44 PM   #1
bikecat OP
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Wicked Replacing BMW nuts, washers etc

Hiya,

I am thinking of replacing stock nuts and washers with stainless steel ones. Any downside to this? For example, I am thinking of replacing items 2 and 3 below



with this one-piece item:



Views?
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Old 12-03-2012, 07:49 PM   #2
Airhead Wrangler
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It'd probably work alright, but the wave washer acts as a lock washer. That one piece deal might back itself out. It'd probably work fine alright though.
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Old 12-03-2012, 11:29 PM   #3
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The stainless nut alum head and steel stud will set up recipe for galled threads and a busted stud in the valve cover.
I'd stick with stock BMW in that area. If your worried about it looking bad get some high heat silver and black paint and just touch it up with a brush.
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Old 12-04-2012, 12:30 AM   #4
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Beside the already stated galvanic reaction problem when mixing dissimilar metals, the washer acts as a smooth surface for the nut to tighten against so the torque applied to the nut can be more accurately measured.

As an example of the opposite, what if the surface the nut was turning against had a few heavy scratches/ridges? Then the nut would feel tight to turn even though the bolt was not being stretched very much. The stretch in the bolt is what compresses/clamps whatever is between the bolt head and nut. The most common extreme example of car makers being sensitive to this is in head bolts where they specify to NOT re-use them because each use polishes the bold threads which throws off the torque to stretch ratio.

The really cool solution to this all (which no-one except some military and probably aircraft/spacecraft folks do) is to not use torque but instead nut turns past initial contact. For this you need to know the bolt material, diameter, pitch, and the length of bolt that will do the compressing (the stretched part). You then turn down the nut to make contact with the washer, and then turn the prescribed number of turns to get the desired stretch/compression. Cool stuff.
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Old 12-04-2012, 02:08 AM   #5
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Very many of the various nuts bolts and spindles on my bikes are SS, I have never suffered from any galvanic reaction and or galled threads on my bikes, I'm sure that it is possible in theory but not in practice,I do use a smear of copper grease on the threads.
There are also a variety of wave washers available in SS. It is also very possible to over think torque values in airheads, the only places I use are torque wrench are the cylinder head bolts and the swinging arm, otherwise some sympathy for the nuts bolts you are dealing with works.
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Old 12-04-2012, 04:24 AM   #6
rambozo
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+1 on what chas said

Almost everything on my /7 is stainless and iv had no problems,
from axles to carb top screws, i get mine from shaw stainless in
England, he specialises in BMW and Moto Guzzi and it's very good
quality, down to the correct waverly washers. There's a lot of poor
quality ss out there so be careful

I rarely use a torque wrench outside of an engine or gearbox, it's
down to how much experience you have too though, be sensible
with force and if you're not confident enough use a torque wrench
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Old 12-04-2012, 08:39 AM   #7
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Where I live I can toss a rock and here it go splash into the ocean.
Galvanic reaction is a way of life here. The op's stated location is the tropical far east, I would think that that kind of environment would be ripe for rust, just like my own home.
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Old 12-04-2012, 09:07 AM   #8
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Our roads over here are salted in the winter. I have also noticed that yachts combine SS and aluminium.
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Old 12-04-2012, 02:28 PM   #9
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"It is also very possible to over think torque values in airheads"

After nearly fifty years of motorcycle ownership and ten years on motorcycle forums, I do find our American friends over analyse stuff as well as an unhealthy reliance on bloody torque wrenches. We should remember that in the main, motorcycle engineering is only one step up from Lego not one step down from nuclear physics
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Old 12-04-2012, 02:57 PM   #10
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Stainless is for boats.
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Old 12-04-2012, 04:00 PM   #11
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In my climate if it's good enough for boats it's good enough for me

Sorry to disagree supershaft, I like your posts because you seem to ride similar to me, I
rev till the engine says no, not the counter, but one thing I don't like is rust, plenty of
grease and good quality stainless is hard to beat. Paint is okay until you put a spanner to it

Good proper rated stainless is dear but if you live in a place where it rains almost constantly
and the roads are salted in the winter it's worth it
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Old 12-04-2012, 05:33 PM   #12
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Thanks for the views and replies.

I have decided against it because the underside of the nut has groves that will mark / wear the surface of the cylinder heads. Pity, I was really hoping to replace 2 components with one.



I had used SS bolts to replace stock ones without problem.

The washer that BMW has on this part is really thin, I wonder how useful is that and will it matter if I replace the washer with a thicker one. Does it matter if the inner diameter is slightly bigger?

Cheers
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Old 12-04-2012, 05:51 PM   #13
disston
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I use the ordinary nuts but no washers on the rear side of the valve cover. I don't notice any exceptional amount of wearing of the Alumninum but I guess there may be some. Like It will be noticeable in 50 years or so.
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Old 12-04-2012, 06:04 PM   #14
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Quote:
Originally Posted by Paul_Rochdale View Post
After nearly fifty years of motorcycle ownership and ten years on motorcycle forums, I do find our American friends over analyse stuff as well as an unhealthy reliance on bloody torque wrenches. We should remember that in the main, motorcycle engineering is only one step up from Lego not one step down from nuclear physics
Guilty as charged. We overcomplicate everything. During the space race NASA spent millions developing pens that would write in zero gravity. The soviets just used pencils. I try to be more russian than american with engineering problems.
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Old 12-04-2012, 06:05 PM   #15
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Quote:
Originally Posted by chasbmw View Post
Our roads over here are salted in the winter. I have also noticed that yachts combine SS and aluminium.
They do it ,but it causes all sorts of trouble. Anywhere you have winches or other hardware attached to an aluminum mast with stainless, it's almost guaranteed to give trouble next time you go to disassemble it. On bikes though, I've never had stainless fasteners cause trouble.
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