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Author Topic: Tires, Tube or Tubeless: '78 cb750f comstar wheels  (Read 17054 times)

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Offline dboblet

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Tires, Tube or Tubeless: '78 cb750f comstar wheels
« on: May 11, 2008, 07:24:04 AM »
are the comstar aluminium wheels designed for tube or tubeless tires... and... if tubeless, can one use a tube?
Advantages, disadvantages?
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Offline Lumbee

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #1 on: May 11, 2008, 07:27:11 AM »
...I want to say they are tube...I'm not aware of any advantages either way...
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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #2 on: May 11, 2008, 07:31:44 AM »
I think comstars are designed as tubeless, if you run with a tube you drop the speed rating of the tyre a little
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Offline Lumbee

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #3 on: May 11, 2008, 07:35:09 AM »
...I stand corrected, though run tubes in mine...
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Offline Geeto67

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #4 on: May 11, 2008, 08:06:28 AM »
surprisingly enough there are two versions of the early silver SOHC 750 comstars - tube and tubeless. Although they were designed to be tubless some of the early ones were shipped with tubes in the tires. I have no idea if those shipped that way will leak if installed tubless.

You can run any tubless tire with a tube on just about any rim. I run metzler lazertechs on my K5 with a tube in them (spoke rim) and those tires are designed to be tubless. On my 1979 DOHC with comstars I run avon venoms tubless. Not sure what is in my 78F because I bought the bike with the shoes already installed.
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Offline GeoffT

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #5 on: May 11, 2008, 09:02:31 AM »
I have Lester alloys on mine and I am told they are meant for tubeless. I run them with tubes though. Only cos it was suggested to me that after 30 years, tubeless ones might not hold the air as well as they used to.
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Offline mick750F

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #6 on: May 11, 2008, 04:10:02 PM »
   '78 750F Comstars are tube type rims. You can use tubeless tires but have to use a tube and will lose a speed rating because of this. I'm running Dunlop GT 501's on mine.

Mike
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Offline UnCrash

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #7 on: May 11, 2008, 06:13:39 PM »
My 78 750F Comstars will run tubeless, but my mechanic couldn't get the tubeless valve stem to seat right so I said go ahead and throw tubes.

Oh No, I can only go 120mph now!   :'(   ;)

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Offline kghost

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #8 on: May 11, 2008, 07:00:13 PM »
The tubeless rims are clearly stamped tubeless
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Offline mick750F

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #9 on: May 12, 2008, 05:55:16 PM »
Quote from: UnCrash on May 11, 2008, 06:13:39 PM
My 78 750F Comstars will run tubeless, but my mechanic couldn't get the tubeless valve stem to seat right so I said go ahead and throw tubes.

Oh No, I can only go 120mph now!   :'(   ;)



  Your mechanic couldn't get the valve stem to seat right because it's a tube type rim.  ;)

Mike
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Offline 333

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #10 on: May 12, 2008, 06:14:19 PM »
I only heard of this happening once, but that's all it would take for me.  A tubeless tire on a tubeless rim with a tube supposedly pushed the tire off the rim.  We have to run tubes in tubeless tires on our spoke rims if we want decent tires.  And if you couldn't get the stem to fit, it's probably a tube rim.
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Offline detdrbuzzard

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #11 on: May 12, 2008, 06:23:13 PM »
the rim is not designed to be used without a tube nor is the valve stem seat. you may get lucky and get a valve to work and the tire may hold air but the origional design was for a tube
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Offline Terry in Australia

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #12 on: May 12, 2008, 07:03:46 PM »
Well I checked my F2 owners manual, my factory F2 workshop manual, and some old magazine articles and I can't find anything to say you can run tubeless tires on early Comstar rims. Tim (KGhost) is right, the F2 rims aren't marked "For tubeless application", but a later pair I have (19790CBX1000 front, 1982 CB900F2 rear) do.

Having said that, I'm running Bridgestone BT45's front and rear on my current 1977 CB750F2, tubeless. My other F2 ran tubeless tires as well, and I did thousands of miles on that bike, with no issues whatsoever.

Sadly this F2 has sat in the garage for three years now, and I had to re-inflate the tires when I recently re-sealed the engine cases and put it back together, but after three years, they were only down to around 20 psi (+/ -) each.

Running tubes in any tires is dangerous due to the possibility of a blowout causing a catastrophic tire failure at speed, but of course, can't be avoided on 1970's spoked wheels for obvious reasons, or earlier cast mags, due to porous castings.

This is has not been an issue with my Comstar wheels though, obviously for safety reasons I can't recommend using tubeless tires on them as I don't have any data to suggest that I can, but I do know that Comstars were designed for tubeless tires, and I can't see any physical difference in the rim design of either the "Tube" or "tubless" Comstar rim, so I'll continue to use them. Cheers, Terry. ;D

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Offline dboblet

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #13 on: May 12, 2008, 08:04:12 PM »
I can't find anywhere on my wheels where it says tubeless.  the 78 supersport ought to be an F3 according to the shop manual and serial number.  I think I'll put tubes in when I mount the tires.  The comment about catastropic failure has me wondering though.  Tubed tires have this type of failure and tubeless do not?  Hey, a blow out is a blow out in my book.  Is there reason to believe that tubed tires suffer more 'catastropic' failures than tubless.  I'm sure there is a temperature issue, and some friction component there as well.  But, at the risk of taking this to 8 pages like the thread on Cheng Shin tires, I ask "which is safer, given a properly designed rim and tire".

Oh, by the way, great looking bike Terry, great paint job.  I'm going to rattle can mine at some point as well...
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Offline Terry in Australia

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #14 on: May 12, 2008, 08:27:39 PM »
No worries mate, one of the major advantages of a tubeless tire over a tube tire is that a tubeless tire will gradually deflate if punctured, but a tubed tire can "blowout" I haven't heard of a tubeless tire "blowout", and I've had plenty of punctures on tubed tires with no real ill effect (apart from the obvious) but I've also been driving an Army Landrover 110 on a freeway at 60 MPH when I blew out a new front tubed tire, and I almost lost control. I was carrying two passengers and 3 million bucks worth of communications equipment, so that wouldn't have been good.

A mate of mine blew out a front tire on his CB750K2 in 1978 and it threw him down the road, but luckily, there was no other traffic and he didn't collect any trees or "road furniture" along the way, so he survived. His bike was fitted with Dunlop K81 tires (with tubes) in good condition. As I said before, it can't be avoided that we have to use tubes in our older bikes with spoked wheels, but I'm prepared to take a risk on my F2 with Comstar wheels. Cheers, Terry. ;D 
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Offline bryanj

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #15 on: May 13, 2008, 10:11:13 PM »
Easy way to tell is the size of the valve hole:-

Honda used a car type(but different size) pull through rubber valve on tubeless and if you want to fit a tube there was a special nut with a plain shoulder to take up the play of tube valve stem to hole.

As to blowouts try loosing an 11.00x22.5 comerecial tubeless on the steer axle when running at 97,000lb gross, proves that adrenalin is runny and brown!!----didnt do much for the Ferrari that launched on the shed casing either
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Offline dboblet

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #16 on: May 14, 2008, 06:27:55 AM »
My comstars have a metal threaded valvestem with a nut on it, so I still don't know.   It's not a rubber pull though type though... so .. probably a tube??  I'll know by the weekend anyway... darn, now I need tire irons.

 BTW.  Do I need to break the chain to get the rear wheel off???
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Offline bryanj

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #17 on: May 14, 2008, 09:16:51 AM »
Metal thread with nut is 90% probable tube UNLESS some one in the past has used a Kawasaki tubless valve, which dont seal well by the way
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Offline bill440cars

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #18 on: May 14, 2008, 08:57:38 PM »
Quote from: kghost on May 11, 2008, 07:00:13 PM
The tubeless rims are clearly stamped tubeless

          Having just gotten in on this, I was going to ask the question,"How do you tell, are they marked?" Then I saw that Tim clearly stated the answer. 8) Thanks for that Tim. I also saw that Terry of Australia, verified Tim's answer, so I'm off to check mine when I get the opportunity.

                              Take care guys, Bill ;)   
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Offline dboblet

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #19 on: May 14, 2008, 09:23:18 PM »
yes but...
can I remove the rear wheel to change the tire without breaking the 630 chain?
thanks.
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Offline bryanj

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #20 on: May 14, 2008, 09:44:56 PM »
From memory yes as long as the spindle comes out
TAKE NOTE OF WHERE THE SPACERS FIT
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Offline TwoTired

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #21 on: May 14, 2008, 09:45:18 PM »
Quote from: dboblet on May 14, 2008, 09:23:18 PM
yes but...
can I remove the rear wheel to change the tire without breaking the 630 chain?
thanks.
Yes, of course.
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Offline Terry in Australia

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #22 on: May 14, 2008, 10:21:30 PM »
Quote from: bryanj on May 13, 2008, 10:11:13 PM
Easy way to tell is the size of the valve hole:-

Honda used a car type(but different size) pull through rubber valve on tubeless and if you want to fit a tube there was a special nut with a plain shoulder to take up the play of tube valve stem to hole.

As to blowouts try loosing an 11.00x22.5 comerecial tubeless on the steer axle when running at 97,000lb gross, proves that adrenalin is runny and brown!!----didnt do much for the Ferrari that launched on the shed casing either

I must have the Kawasaki ones on my rims Bryan, they're metal, but they seal fine, as I said, after 3 years of sitting in the garage, they were only down 12-16 psi.

I didn't realise that commercial truck tires are tubeless, all Army truck tires are tubed, how do tubeless tires work on split rims? Cheers, Terry. ;D
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So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline bryanj

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #23 on: May 16, 2008, 09:07:38 AM »
They dont use split rims mate, just BIG levers to fit em
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Offline Terry in Australia

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Re: Tires, Tube or Tubeless: '78 cb750f comstar wheels
« Reply #24 on: May 17, 2008, 12:30:02 AM »
Geez it'd be fun trying to get those beads to seat on 22 inch rims Bryan? :P 
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I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)
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