Topic: To Tube or Not to Tube. That is the Question.

[Imago]

What's best when using a tubeless tire (Metzeler Lasertec) in a 1978 Comstar rim?

I've checked the site here and there doesn't seem to be a definitive answer...

[cmonSTART]

Well, Comstar rims were designed to run with a tube. 

But, I know a few people running w/o tubes and are doing fine.  Me?  I owned a GL with Comstars and always ran tubes. 

[crazypj]

early Comstars were designed for tubes.
You can run them tubeless but you may have to drill valve hole for a tubeless valve.
 You also need to keep a close eye on tyre pressures as there isn't the MT 'bump' to keep tyre seated if presure drops
 

[cmonSTART]

Early Comstars, you're correct. 

My '81 GL IS designed for tubeless. 

[TwoTired]

What's best when using a tubeless tire (Metzeler Lasertec) in a 1978 Comstar rim?

I've checked the site here and there doesn't seem to be a definitive answer...

I gave you a definitive answer in your other thread.  Rather, I think you are asking for a popular answer.  Or possibly, one that agrees with your personal desires.

The rims were NOT designed to bead lock to tubeless tires and therefore need inner tubes, which is the configuration that was delivered from Honda.
Tubeless tires require a rim designed for them, and the 78's Comstars are not.

Because others do it, is in no way a justification for behavior or practice, imo.
Consider: buffoonery...or murder for extreme examples.

Tubeless tires require a seal between rim and tire in order to hold air.
Tubeless rims have a mechanical feature to hold the bead in place, even without air pressure.
Comstars do not have this feature.  So, the air pressure is the only thing holding the bead in place.  Works OK as long as there is full pressure in the tire.  However, if the pressure gets low via a puncture or neglect, the bead can shift on the rim causing a sudden loss of ALL pressure, with the additional feature of the tire sidewall moving sideways on the rim.  Lateral stability is suddenly lost, with the likelihood that the onset was a bump or road hazard encounter.   So, you'd be adding unpredictable behavior to an undesirable encounter.

If you think that risk is so low as to eliminate the tubes, then you can do whatever you want on your own responsibility.  Personally, I think there are enough risks without adding that one to the pile.  My skin may be old a decrepit, but I don't fancy the process of replacing it.

Good luck!

[Imago]

What's best when using a tubeless tire (Metzeler Lasertec) in a 1978 Comstar rim?

I've checked the site here and there doesn't seem to be a definitive answer...

I gave you a definitive answer in your other thread.  Rather, I think you are asking for a popular answer.  Or possibly, one that agrees with your personal desires.

The rims were NOT designed to bead lock to tubeless tires and therefore need inner tubes, which is the configuration that was delivered from Honda.
Tubeless tires require a rim designed for them, and the 78's Comstars are not.

Because others do it, is in no way a justification for behavior or practice, imo.
Consider: buffoonery...or murder for extreme examples.

Tubeless tires require a seal between rim and tire in order to hold air.
Tubeless rims have a mechanical feature to hold the bead in place, even without air pressure.
Comstars do not have this feature.  So, the air pressure is the only thing holding the bead in place.  Works OK as long as there is full pressure in the tire.  However, if the pressure gets low via a puncture or neglect, the bead can shift on the rim causing a sudden loss of ALL pressure, with the additional feature of the tire sidewall moving sideways on the rim.  Lateral stability is suddenly lost, with the likelihood that the onset was a bump or road hazard encounter.   So, you'd be adding unpredictable behavior to an undesirable encounter.

If you think that risk is so low as to eliminate the tubes, then you can do whatever you want on your own responsibility.  Personally, I think there are enough risks without adding that one to the pile.  My skin may be old a decrepit, but I don't fancy the process of replacing it.

Good luck!

I checked back, and yes, you did provide a definitive answer and I stand corrected. Tubes it is!

Can I ask what make you'd recommend?

[cmonSTART]

What's best when using a tubeless tire (Metzeler Lasertec) in a 1978 Comstar rim?

I've checked the site here and there doesn't seem to be a definitive answer...

I gave you a definitive answer in your other thread.  Rather, I think you are asking for a popular answer.  Or possibly, one that agrees with your personal desires.

The rims were NOT designed to bead lock to tubeless tires and therefore need inner tubes, which is the configuration that was delivered from Honda.
Tubeless tires require a rim designed for them, and the 78's Comstars are not.

Because others do it, is in no way a justification for behavior or practice, imo.
Consider: buffoonery...or murder for extreme examples.

Tubeless tires require a seal between rim and tire in order to hold air.
Tubeless rims have a mechanical feature to hold the bead in place, even without air pressure.
Comstars do not have this feature.  So, the air pressure is the only thing holding the bead in place.  Works OK as long as there is full pressure in the tire.  However, if the pressure gets low via a puncture or neglect, the bead can shift on the rim causing a sudden loss of ALL pressure, with the additional feature of the tire sidewall moving sideways on the rim.  Lateral stability is suddenly lost, with the likelihood that the onset was a bump or road hazard encounter.   So, you'd be adding unpredictable behavior to an undesirable encounter.

If you think that risk is so low as to eliminate the tubes, then you can do whatever you want on your own responsibility.  Personally, I think there are enough risks without adding that one to the pile.  My skin may be old a decrepit, but I don't fancy the process of replacing it.

Good luck!

I have to say the gentleman above has a point.  It's why I've always run tubes in my old Comstars. 

[grcamna2]

+1 on living to see another ride as per TT;my early 80's Suzuki GS1100E's came with tubes...but a number of my customers bikes would come in w/ a steel tubeless valve stem installed and I replaced tires on them and would send them out again tubeless until I spoke to a few of my supporting Dealerships...needless to say they warned me about the liability issue at stake."I couldn't purchase enough insurance to pull a stunt like that" was the way one very helpful and caring head mechanic explained it to me on one occasion;I have LOTS of used steel valve stems from those days .

[crazypj]

I knew I had pics somewhere, had to search though photobucket to find them
Tubeless rim profile


Tube profile

[Danno]

just an example but in my youth my cousin went tubeless on his enduro which was a small bike 125cc we were on the road from his house to mine I was in my truck and when we went over the railroad tracks which was not all that rough but it was on an angle and a bit of a bounce the back tire deflated and came off the rim the bike itself was not very old 84 at the time and he layed it down it was not very pretty after that

[MoMo]

To be safe or not to be safe should be the title ...Larry

[scottly]

Just when did they start running tubeless tires stock with Comstars? I found a Honda ad for the 1980 750 and CBX that touted tubeless tires, and I think the 1979 models of those bikes also came with tubeless tires. Are there any markings on the '78 rims, such as TL?

[cmonSTART]

I think the only ways to tell what rims you have is to look at where the valve stem goes through, and look to see if you have the bead ridges around the inside as seen above.  I think Comstars went tubeless in 1980.  For sure, my '81 Goldwing Comstar rims are designed to be tubeless. 

Keep in mind you can run tubeless tires on either rim, but you will have to run tubes inside the tubeless tire in the older rims, which is fine.

[scottly]

I have a Kawasaki Morris-clone rim, from an '82 GPZ 550. It is marked in raised cast lettering that it is tubeless, yet it does NOT have the bead ridges.

[Imago]

I think the only ways to tell what rims you have is to look at where the valve stem goes through, and look to see if you have the bead ridges around the inside as seen above.  I think Comstars went tubeless in 1980.  For sure, my '81 Goldwing Comstar rims are designed to be tubeless. 

Keep in mind you can run tubeless tires on either rim, but you will have to run tubes inside the tubeless tire in the older rims, which is fine.

My new Metzeler Lasertec's on the way for my new (to me) 1978 750F, as far as I can tell one of the last SOHC's made. The current tires are Avon's circa 1987 so are well past their prime.

When I get the old tires off I'll take some photos of the inside of the comstar rims and share them here.

Any recommendations on good tubes?

 

[BobbyR]

Metzler makes natural rubber tubes. A few bucks more but worth it.

[Imago]

Metzler makes natural rubber tubes. A few bucks more but worth it.

Metzeler tubes in Metzeler tires... sounds good to me. Now to check the web for prices...

[Danno]

My 79 750 had tubes and no shoulders to go without they were comstars it may have been something they added in 79 though because mine was an early one it was a late 78 dohc

[crazypj]

A I said earlier, you can run tubeless on ANY Comstar, but, if tyre pressure drops tyre can fall off rim.
 Yamaha did the same with their cast wheels and I have little doubt Kawasaki, Suzuki and Harley were the same.
I heard stories about California Highway Patrol having first issues with their HD's and Kawasaki's which led to the MT standard being introduced in the mid/late 70's
They were using tubeless tyres on rims not specifically designed for tubeless.
 Don't know how much truth is in the story, I was in Britain at a Honda dealers when I heard it from Honda Rep (around 1978)

[the technological J]

is there a down side to tubes? im missing the "big deal" here... so what is the big deal in using tubes if theres any question why get rid of em?

[TwoTired]

is there a down side to tubes? im missing the "big deal" here... so what is the big deal in using tubes if theres any question why get rid of em?

A tire "squirms" while turning as it contacts the road and then departs contact.  The squirm creates friction and heat.  So, a tubed tire generates more heat while driving as the tube rubs against the tire carcass.  The heat generation increases with speed as centrifugal forces add to the tires resistance to flexing.  It is this reason why the speed rating of the tire is reduced one letter when using tubes in a tube tire.

So, if you buy V rated 149MPH tires, they are demoted to H rated 130MPH tires.  H rated tires become U rated 124MPH tires and so on.

There other "drawback" and one reason why Tubeless has nearly taken over the current market, is blowout avoidance.
If the tire carcass happens to split, the tube can poke or bubble outside the tire carcass, where any damage then causes nearly instant loss of pressure and often loss of control.  Tubeless tires avoid this particular failure mode and air loss is most often gradual, which allows the operator some time to deal with the let down.  In the early days repair was cheaper too, as they used to use plugs in simple punctures without removing the tire from the rim.  I think this practice has largely been replaced with an internal patch.  Interestingly, a patched tubeless tire ALSO loses one letter of speed rating for each patch installed.

Tubeless tires CAN still blowout from a bead separation or severely damage sidewall.  But, the latter also applies to tube type tires.

Cheers,