Boxerworks.com

I’m new to cycling and I’m trying to find tubes for the tires I’m getting for my 1992 BMW R100R with the stock spoke wheels (not snowflakes). The tires are 110/80-18 and 140/80-17. Nowhere online has any tubes that fit this size and I find that hard to beleive. I’m wondering if I’m not understanding tube sizes and how they are listed on sites like RevZilla or not.

Am I specifically looking for a tube that has the same size as the tires? Because often sites will have what looks like I range but I can’t be sure. For example on one tube the size is listed as 130/160-17. Does that mean it would fit my 140/80-17?

Where can I find tubes for these tires and what are some good quality tubes?

I would say 130/160-17 tube would be fine. I'm not particularly familiar with tube sizes for metric lower profile tires but it's common for tubes to cover a range of tire sizes. I would usually tend to aim for the middle of the range or not far off.

I have good news for you. Your R100R wheels are tubeless, like the GS wheels of the same era.

My Haynes manual says 110/80 18 for the front and 140/80 17 for the rear.

As Melville said, tubeless. Are there tubes with your current tires? If so, you'll need valves.
On those wheels (I assume the same as on my Mystic) they are 2 different sizes. One 8mm and the other 11.
You can get the OEM (the 11 is rubber. the 8 is metal with an o-ring).

Because you identify yourself as a "newbie" I'll add some info:
Those wheels have the spoke adjusters in the hubs and the other side goes thru the sides of the rim flanges, unlike traditional spoke wheels where the spoke adjusters run down the center of the rim. So the center of this rim is sealed and the bead has a safety ridge for running tubeless. And since the spokes run down the outside of the rims, the rims are very difficult to keep clean. On the good side, they are about the strongest wheels on any bike, which is why people who take their GS bikes offroad use them.

From your post, it sounds like you're taking our advice to get stock tire sizes. Changes in tires affects steering geometry. For example, tall tire in front will increase the trail and slow steering down. This isn't to say that you shouldn't do changes. Racers make minor changes for each event. Some high performance and race bikes have adjustable suspension (steering head bearings to change the rake and trail, and swing-arm pivot to change rear squat and traction). Just make sure you understand the impacts of the changes. There's lots of engineering involved.

Best of luck with the bike.

I'd be a rebel and put tubes in it.

Some folks find that these tubeless cross spoke rims loose air, suddenly, for no reason, at high speed, and after it happens once, just fit tubes to make certain it never happens again.
The PO if your bike may have been one of them.
FWIW I am one, and use Michelin heavy duty tubes which my dealer has to order in for me with the tires.
I find that with the tubes the tire if anything runs cooler - presumably the tube conducts heat round to the rim better than air, and if the extra weight affects the handling the difference is so small as to be unnoticeable with a Ohlins/HPN set up which I tune to suit the tires anyway.

In the US, I've never seen metric sized tubes. They may make them, but since most of the need is for classic or older bikes, inch sizes are far more common. I'd think 3.00-18 for the front and 4.00-18 for the rear would be excellent.

It's always best to be smaller than needed. Tubes will expand a tremendous amount, so adapting to one size larger is not a problem. I didn't always think that way until a fellow mechanic at the shop took an old 4.00-18 tube and inflated it to 6 feet in diameter !!

A little advice though, I've done a four or five tire changes with these wheels. I would not put a tube in these. It reduces the speed rating of the tire and there is no reason to. Do not use soapy water as a bead lube. Also be very careful with the irons when mounting and dis-mounting tires on these rims as they will scratch easily. I used to use water and dish soap as a bead lube. I developed a slow leak and discovered corrosion in the bead area of the rim causing the leak. Caught it early so it cleaned up with some effort. You will absolutely need bead lube to seat the bead on these, I was never able to seat any tire on these rims without quite a bit of air pressure and lots of lube.

We had this same corrosion problem back in the '90s. We used Vaseline as a lube and never had a problem, still use it today.

I started changing tires professionally at a m/c dealership back in the mid-1960's and have tried all those formulas and compounds. I finally broke down and went and purchased some professional tire mounting lube. Man what a difference !! It turned out it costs something like $6 for a gallon. Applied liberally with a cheap paint brush, nothing is better.

After I started using it I was shaking my head wondering why I waited so long.