Tubless conversion on cast tube type wheels

[Perazzimx14]

This is certainly a lot easier than dealing with spoke wheels.

1. Gather up a 1/8" IPS pipe tap and a schrader x 1/8" NPT air tank fitting and a roll of teflon tape. These products are available at most farm and fleet or home center stores. If you don't have or cannot find a tap either Amazon or a plumbing supply shop will carry it.
2. Remove tire and tube



3. Glop up the tap with a dab of lube (Criso actually is great for tapping aluminium.) and insert the tap into the valve stem hole. Slowly start the tap making sure it is square to the wheel. 



4. Run tap down about 1/2 way (1 rotation down 1/4 turn back to clean the tap). If you are unfamiliar with the tapping process there are lots of video's on YouTube



5. Once the tap is threaded in approximately 1/2 way back it out and screw in the fitting finger tight. You want the fitting to be snug with a 1/4 of the threads showing. If more than a 1.4 of the threads are showing run the tap in a little further (like 1/2 to 3/4 full turn) and recheck. Once you get to where only a 12.4 of the threads are showing apply 2 wraps of teflon tape (only 2 wraps you are not trying to see how much you are trying to get on the threads). MAke sure the teflon tape has not blocked the hole ion the schrader fitting then install in to newy tapped wheel. Tighten down with the right size wrench being careful not to overtighten. From finger tight tighten 3/4 to 1 turn. INstall tire and inflate. Soap the threads to see if they are leaking. If so deflate the tire and tighten 1/2 turn then repeat the testing procedure until leak free.   



Its a 5 minute project tapping and tightening the fitting.

[mtiberio]

I would add, direct the tap from the axle/cast spoke side of the rim, not the "tube" side. It is obviously easier to run it from the tube side, but the taper will be wrong. Running from the axle side is more difficult to start square, but obviously gets the taper right.

Using terms like inside and outside could be ambiguous. But you need to start and run the tap from between the cast spokes, not the tube side of the rim.

[jas67]

Hmmm, might have to do this at tire change time on my Le Mans.

[Groover]

Very clean job, but where is the food? 

[Diploman]

Using directions provided by Mike Tiberio, I did this tubeless conversion on the cast wheels of both my V50!! and SPNT about 10 years ago.  Since then, absolutely zero issues.  Not only are tubeless tires lighter, less expensive and less problematic to install than the OEM tubed version, but they are safer - less prone to sudden deflation, and easier to repair.  A very worthwhile upgrade.

[Perazzimx14]

I would add, direct the tap from the axle/cast spoke side of the rim, not the "tube" side. It is obviously easier to run it from the tube side, but the taper will be wrong. Running from the axle side is more difficult to start square, but obviously gets the taper right.

Using terms like inside and outside could be ambiguous. But you need to start and run the tap from between the cast spokes, not the tube side of the rim.

Yes do tap the wheel from the axle side into the drop center as shown. If you tap from the drop center out towards the axle the thread taper will be the wrong way. That also why I used a ratchet/socket instead of the traditional tap handle to fit between the spokes.

Jay,

If you need to borrow (or not) a tap let me know we can meetup up at the Sandwich Man for lunch.

[Perazzimx14]

Very clean job, but where is the food? 

Sorry, you're gonna have to wait until Sunday when either Roman beans and sauerkraut or Pappardelle w/ Braised Beef, Port Wine and Gorgonzola cheese will be the main attraction.

[lucian]

Something about threading a tapered wedge into a cast rim makes me nervous.
 Another approach would be to first use a piloted end mill to mill a flat seat and then tap for a standard straight thread stem with an o ring. 

[Motorad64]

Interesting!   So...you can't just use a traditional tubeless tire valve? 

[Perazzimx14]

Something about threading a tapered wedge into a cast rim makes me nervous.
 Another approach would be to first use a piloted end mill to mill a flat seat and then tap for a standard straight thread stem with an o ring.

If this makes you nervous stick with tubes. This isn't rocket surgery. Its tapping a thread that has the ability to hold 40 psi or less. A tapered NPT thread will withstand pressures substantially higher than the tire itself without stressing/fatiguing the surrounding metal.

There is no need for an end mill, CNC or even a drill bit. The valve stem opening as is, is perfectly sized for running an 1/8th".  Just thread it in and be done with it! 

[Perazzimx14]

Interesting!   So...you can't just use a traditional tubeless tire valve?

If you mean the rubber pull thur valve stems, no they will not work. The opening is not jarge enough nor is the drop center machined to accept the valve stem base or tapered top.   

[Guzzidad]

   And about the teflon tape: most people think the primary purpose of the tape is thread sealant, which it does to a certain extent. But the primary job of the tape is to lubricate the threads so you can screw the pieces together better. I spent many years pipe fitting and steam fitting and rarely used much more than 1 1/2 wraps of tape.

[jas67]

Yes do tap the wheel from the axle side into the drop center as shown. If you tap from the drop center out towards the axle the thread taper will be the wrong way. That also why I used a ratchet/socket instead of the traditional tap handle to fit between the spokes.

Jay,

If you need to borrow (or not) a tap let me know we can meetup up at the Sandwich Man for lunch.

Thanks, I'll keep that in mind.
I've got a pretty complete set of metric taps.

We can still meet up for lunch sometime, though I don't work near Sandwich Man anymore, I'm over in Middletown, on Fulling Mill Rd, near the turnpike interchange.

[Perazzimx14]

I'm familiar with the FMR facilities. I'm only a few miles away on 17th street.

Lots of options for lunch around Bass Pro or Eisenhower Blvd.

[mtiberio]

Something about threading a tapered wedge into a cast rim makes me nervous.
 Another approach would be to first use a piloted end mill to mill a flat seat and then tap for a standard straight thread stem with an o ring. 

If these rims were brittle, I'd be more concerned. Since the material behaves in a manner that garnered them the name "lead butter" I'd expect them to deform rather than fail catastrophically, but as always assume your own risks, YMMV.

[Perazzimx14]

Hmmm, might have to do this at tire change time on my Le Mans.

The nice thing is you'll loose around 3 lbs of unsprung rotating by weight ditching the tubes. The bad news is losing 3 lbs is like throwing a deck chair off the Titanic.

[Chuck in Indiana]

The nice thing is you'll loose around 3 lbs of unsprung rotating by weight ditching the tubes. The bad news is losing 3 lbs is like throwing a deck chair off the Titanic.

[Rough Edge racing]

 If you look on a place like Ebay there are metal threaded stems for tubeless that will fit the the smaller diameter tube type stem hole...No need to drill and thread ....Or you can simply drill out the stem hole... I recently installed tubeless tires on my 79 Triumph T140D with original Lester cast wheels, used the small diameter stems so the original wheels are not altered..And the rims had safety beads...
  Tire manufacturers do not recommend tubeless tires on rims without a safety bead..

[Perazzimx14]

If you look on a place like Ebay there are metal threaded stems for tubeless that will fit the the smaller diameter tube type stem hole...No need to drill and thread ....Or you can simply drill out the stem hole... I recently installed tubeless tires on my 79 Triumph T140D with original Lester cast wheels, used the small diameter stems so the original wheels are not altered..And the rims had safety beads...
  Tire manufacturers do not recommend tubeless tires on rims without a safety bead..

Thee are many way to skin this cat. With my method the valve stem hole is not drilled out any larger only tapped as the existing hole is perfectly sized. If you want to go back to tubes simply remove the air tank schrader and reinstall the tube. Thought the wheel is technically "altered" the act of tapping the existing valve stem hole didn't alter it to a point where its even noticeable or have any effect if you wanted to go back to stock. Also the way I did the conversion I already had the tap and the air tank schrader's are available locally so it wasn't an order parts and wait. It was come home and 10 minutes later have the tubeless conversion done. 

Again this is the way I did the conversion and feel 100% confident in this method. I am not suggesting this is the only way or even if others should do this. That is a decision each individual will have to make for themselves. 

[Rough Edge racing]

 Don't take me wrong, I find your tapping the hole to be clever... But from what I read on here, not everyone is clever and may prefer an installation using no sharp tools 

[F-22]

Is the cast wheel bead edge the same for tube type or tubeless tyres? I think some late 70's Suzukis had "for tube tyres" written on the cast wheels (or did it say "for tubeless tyres" ? not entirely certain).

[Groover]

I got this one ... I've researched the c*rp out of this and... The cast wheels used on the G5, Convert, LM, SP from that era (or I should say at least the ones on my '81 G5 for sure) have the following markings which indicate the type of contour/profile of the rim.

These are the markings on my 1981 G5 Cast wheels - CP2 & WM3 (should be the same as the ones on Perazzimx14's SP1000)



I've collected this information over the years on various sites out there:






My personal conclusion is that these rims are safe to run tubeless because of the additional CP3 profile (contre pente - reverse taper locking the tire in) however, these are still not considered "tubeless" and bigger motorcycle tire shops won't mount tubeless tires on them without the required tube because technically they are not tubeless rated. Anyway, all at your own risk - these are just my findings.

More reading on this can be found here: http://bmwmotorcycletech.info/section6.htm

[Kiwi_Roy]

I have converted several guzzis to tubeless, I like your method much better than the the stems with a nut I put on my Cali II

I have had some kickback from the tire shops but at the end of the day money talks.

[mtiberio]

If these rims were brittle, I'd be more concerned. Since the material behaves in a manner that garnered them the name "lead butter" I'd expect them to deform rather than fail catastrophically, but as always assume your own risks, YMMV.

Actually, I think it is only about 1 pound (unless you run thorn proof dirt bike tubes). But that one pound is unsprung, and rotational mass, so it is important.