Spoked rear wheel

[marcmax]

Anyone know what my options are for using a spoked wheel on the rear of a 1984 LS?

[Tony Smith]

I know that an R75/R80 stroke 7 will fit and I therefore assume that a /5 will also fit.

My question would be though - given that a sidecar places a lot of lateral stress on the wheels and that cast wheels cope with tha stress very well indeed - why would you change?

[marcmax]

This will be used on the garage queen that has been sitting neglected and unloved for the last 4 years not the sidecar tug. It was bought partially disassembled and missing a number of pieces but is a complete frame with running motor and gearbox, wheels etc. I picked up a front assembly from a YZ450 for it, which is a pretty straight forward swap, and plan on turning it into an R65 scrambler. Since it will have a 21" spoke front wheel I wanted a spoke wheel in the rear as well.

My last child (son) is off to university the end of the week and I do not have a she who must be obeyed. I need another project.

fyi - I will have a nice set of LS wheels I will be getting rid of once this progresses.

[nhmaf]

Actually spoke wheels tolerate side loads without cracking, which can occur with cast wheels.    Newer metallurgy does help, too.

[Tony Smith]

Actually spoke wheels tolerate side loads without cracking, which can occur with cast wheels.    Newer metallurgy does help, too.

I lost a lot of spoked wheels on a outfit I built, never lost a cast one though.

[marcmax]

One last question for the vast knowledge base on this forum. I have a line on a R75/7 rear wheel that I will probably buy.

The question is which brake shoes should I use? The rear brake shoes from the LS wheel currently on this bike are a different size than the standard R65 brake shoes. Does anyone know if I will need to replace them with standard R65 brake shoes or if that is even possible?

[Luca]

LS shoes definitely won't fit, they're about 1" bigger in diameter.

The 79/80 R65 shares shoes with the /7, but after 1980 all the Beemers shared different rear shoes (not counting the unique LS)

Not sure what changes were made to the shoes, brake cams, "cardan covers," etc, but if you can make an 81-on rear end work in a 79/80 R65, you should also be able to make that rear end stop a /7 wheel.


P.S.  I might be interested in the LS wheels

[marcmax]

Luca, sent you a pm.

[marcmax]

Well I found an R75 /5 rear wheel in good shape for a fair price. Unfortunately, like anything that old that is alloy, it is oxidized beyond belief. Anyone have any suggestions on how to clean it beyond sitting on the back porch with a good supply of adult beverages, a can of aluminum polish and a lot of time.

[Tony Smith]

Well I found an R75 /5 rear wheel in good shape for a fair price. Unfortunately, like anything that old that is alloy, it is oxidized beyond belief. Anyone have any suggestions on how to clean it beyond sitting on the back porch with a good supply of adult beverages, a can of aluminum polish and a lot of time.

Yep, but you need a good quality compressor, a sand blasting gun and a 40kg bag of food grade bi-carbonate of soda. I bought the Bi-carb some time back to try and it works brilliantly, but my compressor is one of those silly little Chinese direct-drive types that sell for less than $100. It cannot flow enough air and i can only do very small amounts of alloy at a time.

Hydrofluroic acid (NOT Hydrochloric) will do a great job, unfortunately it is one of the nastier substances you will ever come across. Commercial mag wheel cleaners will sometimes have minute amounts in them, but not in my experience enough to clean up a heavily oxidised piece of BMW alloy. Good old "Rust Converter" and the like will remove the white oxide in a trice, but leave the Alloy a very dark and lifeless colour.

The paint company Krylon makes a beautiful "dull aluminium" paint that looks like fresh clean alloy.

[Luca]

+1 for soda blasting.  I made a siphon gun with a small hopper out of some british brake/oil line fittings (spares hanging around the shop I used to work in), a piece of brake line, an air gun, and a tobacco can.

I got a 40# bag of sodium bicarbonate from a local feed store (they use it to treat indigestion in cows!).  Makes an absolute mess, and while it works well, it isn't going to be as fast as regular sandblasting...  but it also won't chew up your aluminum.





Or fill up a big tote container with walnut shells, put the wheel in, and strap a random orbital sander to the container.  Sit on the back porch and have a beer while your new tumbler does the work for you.

[marcmax]

I would love to use a soda blaster on it but I don't have access to a compressor. I have an acid based spray on mag wheel cleaner that I have used on some aluminum items in the past that does a nice job of cleaning. The problem with using it is that the items seem to oxidize faster once I have used it. I think I will try the spray on cleaner followed by an aluminum polish and then a good coat of wax. Or instead of the wax maybe a paint clear coat.

I am hesitant to use an aluminum polish as I don't want a smooth shiny wheel. Or even worse a blotchy looking wheel with shiny and not so shiny patches. I like the look of a satin finish aluminum.

[Luca]

I've heard a lot of people swear by plastidip.  It's a durable rattle can plasticized coating that can be peeled off when you're tired of it.  If you can get the wheels clean and chemically stable, you could try a satin plastidip clear coat.  It's priced reasonably enough to try and you're not stuck with it or hours of removal if you don't like the results.