Topic: Wire wheels rusting underneath tire tube ....

[Zane]

I've completed my obligatory 10 minute search before asking a new question - I can't find anything about it .......so.....

Last week I changed my front tire.  (1976 CB 400 F stock, spoked wheel.)  With the tire off of the rim, I noticed (it was hard not to notice) quite a bit of rust on the inside.  I was tempted to paint it, but my impatience got the best of me (once again), and I simply wire brushed it as best I could, and reinstalled the tire on the rim.

Now it's winter again and I have time to do it right.  (We had 3 or 4 days of spring-like riding weather last week.)  What should I do with the inside of that rim to make it last as long as possible?  I should say that the rust seemed pretty extensive to me.  But then I don't have much experience and I'm not sure if that sort of thing is normal or what. 

Some of that nipple part of a few of the spokes inside the wheel were also rusting.  I'm not sure how to approach it all.  (In my 8 months of motorcycle ownership I've always regularly checked all the spokes, to make sure they are sound.  It's pretty easy to do, since I seem to be cleaning them all the time anyway.)

I'm also assuming that the back wheel will be in similar condition, inside.  Both wheels seem as if they're in awfully good condition on the outsides, despite being over 30 years old.  The chrome on both rims is excellent, as are all of the visible parts of all of the spokes.   I'd like to save it all if I can.

If anyone has any ideas for a fix, or any links for the problem, I'd sure appreciate a push in the right direction.

Thanks!

[supersport_CB400F]

If it's just surface rust don't panic about the area's  on the rim or spokes, if the metal has deep pits on both then you have a problem ...if it's just light then use a rust stopper and replace the parts  when you have time and money.

[Uncle Ernie]

There's rust and then there's cancer.  One way to check the spokes is to use a wrench and tap them each. They should have a ring to each- if there is a dead "thud", the spoke needs to be replaced.  On the inside of the rim, and anywhere for that matter, if the rust is bad enough, just painting over it will only cover it up as it continues to eat the metal. Surface rust can be dealt with, but if you have ANY doubt, get an expert opinion.  IMO, your wheels and tires are the most important parts of the bike- they're your contact with the pavement.

[TwoTired]

10 or 15 years ago I had a rear flat coming home after work.  I could feel it going down and two blocks from home it was flopping on the rim and very difficult to keep in a straight line.  I knew the tire was close to replacement time, so I drove the rest of the way home on it anyway.  Turns out there was rust inside the rim and the rust built a pointed spire the poked through the the rim strip rubber AND the tube.  (eyebrows raised)

I took the rim home and rotary wire brushed all the rust off 'til I could see metal again.  I had some zinc chromate paint left over from refinishing the airplane wheels, so I masked off all but the inside of the wheel and put a couple coats of the paint on the inner rim.  I let that cure, went back to the shop, and had them put a new rim strip, tube and tire on the bike. The next time I replaced the rear tire, I was anxious to see how it faired inside, since I regularly rode in the rain.  The paint had gotten a little darkened and had taken the imprint of the rim strip and tube but there wasn't a speck of rust in there.  Seems the same things that preserve airplane wheels saves MC wheels, too.

Real zinc chromate (not just the color green or yellow) can be difficult to find as the overspray is harmful for humans to breathe. (heavy metal zinc poisoning) So, wear a good mask to breathe air though while painting if you spray.  Although, in hidden areas, no reason not to just brush it on.
Any general aviation airport maintenance shop will either have some to sell you or know where you can get it.

Zinc chromate is a sacrificial paint.  If the surface membrane is broken, the nearby zinc must corrode away before the steel can oxidize.

Better living through chemistry. 

Cheers,

P.S.  If a wheel spoke doesn't ring when you tap it, it means it is loose.  If you can't tighten it to ring at hte same pitch as the others, THEN replace it.

[Zane]

Man!  Where else can a fellow get three expert opinions and experienced advice in a couple of hours, about such a specialized subject, no less?  I'm impressed (and thankful). 

TT, I remember you mentioned zinc-chromate primer in the topic a few weeks ago about painting the insides of fenders.  When I saw the rust inside my front rim, that type of primer was the first thing I thought about.  But then I remembered reading that zinc chromate primer works only if you can get rid of all of the rust, before applying the primer to the metal.  I know it's likely difficult, but can you give me a better idea of how far to go with the rotary wire brush.  (Also, what sort of brush - steel or brass ....?)

The cautions regarding spokes are appreciated.  When I remove the tire to do this job, I'll inspect the inside-the-wheel spoke parts again.  If I have any doubts I'll make a good, close-up photo of any questionable areas, and show it here.  I think it's okay, but I'll be better able to tell with this new info.

I did see a spray-can of zinc chromate primer in a local auto store last week.  I'm guessing this is the type to steer clear of though. 
http://www.plasti-kote.com/plastikote/indust/template.jsp?searchcode=PRI&product=zincchromate

I have a good friend who is into airplanes.  I'll give him a shout.  I'm pretty sure he'll know where to get the "real stuff".

Finally, thanks for the cautions regarding using this type of primer.  I'll be sure to wear proper breathing protection.

[TwoTired]

You have to get rid of any scale on the surface.  Ideally, I suppose, the surface should be bright and shiny.  I didn't do that.  I used a metal scrapper to chip off the loose stuff and then a stiff rotary wheel type steel wire brush in an electric drill.  The surface looked grey going brown in color tint.  And, if you scratched it any where with a sharp pointy, you saw bright metal.
In the ideal world I would use Metalprep or Oxisolv first, then the ZC.  But, I didn't do that and it still worked quite well.

I looked at the plasticote link you posted.  It looks like real zinc chromate to me.
I can't get that at the local stores around here.  Only through aircraft supply.  The Tempo brand is what I had.

If you can find Zinc Phosphate, that would be better to use on steel surfaces.  The phosphate would bind better to steel.  Chromate binds better with aluminum, but still adheres well with steel.

http://www.eastwoodco.com/     Has many rust related products for restoration work.  Browse.

I have also used their Oxisolv to remove rust after the loose scale was knocked off.  It dissolves the rust and leaves a zinc phosphate coating.  You'll still need to paint this, though, to provide a moisture barrier.  But, this is also a very good preservative system.

And they make a "rust encapsulator" coating that really seals out the atmosphere after it hardens (takes awhile).

The Zinc chromate I used was pretty fast drying.  I put on two coats, three hours apart during the summer heat.  The rim was just ready to use the next evening.  I should have let it dry another day, really, as it was still softer than I would have liked.  But, it still worked out okay.  It was quite hard when I saw it again years later.

Cheers,

[Zane]

Thank you very much Lloyd.  The diversity and depth of your knowledge and extent of your experience seems surpassed only by your generosity with your time and your willingness to help.

Even with the few examples here, about bad spokes, it's pretty evident to me what a disaster a failure in a spoked wheel can be.  I plan to invest some time and a few bucks in not only preserving these old wheels, but in making them as safe and secure as I'm able.  They're a lot of work, that's for sure, and definitely a labour of love; but they look so darned good when they're right - all shiney and clean.  I guess I'm new enough; I still find it worth the effort.

 

[n9viw]

Having never worked with zinc chromate or phosphate, I can't speak to either. However, I HAVE worked with Eastwood's Rust Encapsulator, and I can justifiably say that it's not worth the can it comes in. I used it on my wife's '82 Jeep CJ-7, followed all the instructions to a T- brushed off the loose bits, wiped the area down to get rid of oils, painted it on in the appropriate temperature/humidity, waited a good long time for it to set up (took several days), and primed and painted over it. The rust was back within a year, pushing up on my recent paint job.
What I've fallen in love with instead is POR-15 (http://www.por15.com). Used that on my '82 Jeep CJ-8 Scrambler, and can't scratch it with a chisel. You could be a motley fool and still get this stuff to work. A friend of mine even painted it over scale rust on his axle housing, and the POR-15 bound that stuff up so tight it may as well be part of the axle housing again. Only drawback (not an issue inside a rim) is that it isn't UV-stable, so it must be topcoated with an opaque (paint). They also make fuel tank repair kits as well, and I can testify to those, too- sealed up the inside of my CB750's tank when I thought it was a goner. No Kreem for me, POR-15 does it! (and no, I don't work for them or get any kickbacks, just gotta remark on a great product!)

[TwoTired]

I haven't found a problem with the rust encapsulator failing... yet, anyway.  It's been 4 years.  But, I also prepped the metal with the Oxisolv, too.  So, there is zinc phospate under it.

I subscribe to the old addage that 90% of a paint job is in the prep.  Usually when I try and cut corners.  I then do the job twice. 

Cheers,

[Zane]

So it's been a year since I painted the inside of both of my rims with the zinc chromate primer.  I had both wheels apart last week (to replace the spokes and tires) and there was no rust at all.  I ride in a lot of different conditions, including a little snow this year, so it's not like my wheels have it California easy, either.

I'm pretty happy about no rust - it makes the work worth the effort.

Thanks again all .....

Zane

[ProTeal55]

When I changed my wheels I just took a wire wheel to the surface rust (under the rim strip), and then sprayed a few coats of rust-oleum paint on their..

[TwoTired]

Zinc chromate is a proven formulation that has existed since the... well I don't know, before I was born anyway. 
It functions based on well-known and understood chemical principles.

Rust-Oleum is a clever brand name whose formulation can and has changed frequently,  Their formulation also varies with the locale in which it is sold.

I used white Rust-Oleum on a tin roof of a shed building 5 years ago that was beginning to rust.  Within a year, the rust specs began to poke through the coating.  About 30% of the roof is now quite obviously rusty.  I can't see how Rust-Oleum did anything to stop the rust.  It primarily hid it with color temporarily, making it a superficial aid, at best.  I did NOT scour the roof of all surface rust before the generous coating was applied, partly because I wanted to see if the product had any rust inhibitive properties.  (The other parts were access issues and a bit of laziness.)

As a result, I do not believe there is any active component in Rust-Oleum to negate rust.  The rust preventive component offered is to seal the surface, denying the steel access to oxygen and water.  I believe other brands will do this equally well, if not better.  (Rust is porous and any overcoating will trap oxygen and moisture within it, leading to more rust.)

I'm going to have to paint the roof again this summer.  I'm going to use two coats this time.  The first one will be zinc-chromate.  The second one may be Rust-Oleum, only if it is on sale cheaper than the store brand.

Cheers,

[Zane]

I should probably add that, before applying the primer 13 months ago, I gave the insides of the rims a (gentle and sensitive) bead blast.  (It wasn't so much a "blast" as a kind of push - I held the nozzle a long ways back, and just hit it until the rust blew away.)

After that cleaning they looked good, and I cleaned the rims with compressed air is if my life depended on it.  Since the wheels were complete with spokes at the time (and all the little nooks and grannies they create) I wanted to be as thorough as possible getting the blasting stuff out of there.

I made four carboard discs and masked the wheels right to the edge.  The rims were pretty easy to prime at that point.  I used a good quality zinc chromate primer I bought from a marine supply store. 

The instructions for the primer said it could be top coated but I decided to see if the primer would work on it's own ...

..... and with pretty good quality preparation, it did.

Cheers...