Author Topic: Tires, Tube or Tubeless: '78 cb750f comstar wheels (Read 17199 times)

dboblet · « **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?

Lumbee · « **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...

troppo · « **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

Lumbee · « **Reply #3 on:** May 11, 2008, 07:35:09 AM »

...I stand corrected, though run tubes in mine...

Geeto67 · « **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.

GeoffT · « **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.

mick750F · « **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

UnCrash · « **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!

kghost · « **Reply #8 on:** May 11, 2008, 07:00:13 PM »

The tubeless rims are clearly stamped tubeless

mick750F · « **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

333 · « **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.

detdrbuzzard · « **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

Terry in Australia · « **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.

dboblet · « **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...

Terry in Australia · « **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.

bryanj · « **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

dboblet · « **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???

bryanj · « **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

bill440cars · « **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.

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

dboblet · « **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.

bryanj · « **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

TwoTired · « **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.

Terry in Australia · « **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.

bryanj · « **Reply #23 on:** May 16, 2008, 09:07:38 AM »

They dont use split rims mate, just BIG levers to fit em

Terry in Australia · « **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?

bryanj · « **Reply #25 on:** May 17, 2008, 02:40:52 AM »

Special tool Mate, cariable 30-50 ltr ish air tank with a nozzle that blasts the lot straight into the casing over the rim in a split second---tyre dont stand a chance! Better than the Tractor pulling people who run there tyres tubless to save weight---they get them out by filling the casing with easy start and throwing a match!!!!

Pillage · « **Reply #26 on:** February 08, 2009, 08:15:52 AM »

Well alright, the SEARCH function actually worked out for a change!
Thanks for the info Terry, I need new tires on my 78F. It clearly has tubes installed but the rims are clearly marked Tubeless. Anyway that's what I'll try to do. I've had great luck with Bridgestone BT54's, BT020 & BT021's over the years so the BT45's seem like the logical choice. Thanks again,
Pillage
BTW, You've got a very sharp "F", nice pic.

Quote from: Terry in Australia 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.

eldar · « **Reply #27 on:** February 08, 2009, 08:25:45 AM »

I wonder if anyone has sealed their rims and run tubeless spokes? I know on the Tiger, I think it is a triumph, they sealed the rims and ran tubeless.

I would be we could seal our rims just fine but it is probably the rim lip that would not hold. I will have to check out a tubeless tire sometime to see. I would like to do tubeless but it is not a driving force.

754 · « **Reply #28 on:** February 08, 2009, 08:32:33 AM »

BMW also uses sealed laced rims, claim they have to be factory resealed after replacing spokes, but I have a hard time believing that..

KRONUS0100 · « **Reply #29 on:** February 08, 2009, 08:32:59 AM »

I run 78 comstars on my 76 750F without tubes......8700 miles there abouts, no problems. the rims are not stamped either way.

eldar · « **Reply #30 on:** February 08, 2009, 08:56:18 AM »

Well you know bmw, they want to do all the work and rape you sideways.

cafe750 · « **Reply #31 on:** February 08, 2009, 12:16:53 PM »

Quote from: 754 on February 08, 2009, 08:32:33 AM

BMW also uses sealed laced rims, claim they have to be factory resealed after replacing spokes, but I have a hard time believing that..

The wheels on the newer larger BMW's don't need resealed as the spokes aren't laced into the center of the rim. They're laced into the edges of the rim, so that standard tubeless tires work on them. The older bikes, and the smaller F650's still use standard rims with tubes inside.

Um, Eldy, shop rates at my shop are the same as all the other local motorcycle dealers, and if a person wants to do their own work, we'll tell 'em how to do it, with common tools. The parts cost the same as the ones for my Hondas, so, I'm sorry you've had a bad experience with Beemer shops, but don't knock 'em all....

eldar · « **Reply #32 on:** February 08, 2009, 07:37:03 PM »

I do not have a beemer. They are the same as any dealer and charge a lot. Fail to see why you got so jumpy on that. If I went into university motors, I would get charged a #$%*load but then they just built a new shop.

Same goes with auto shops. Some are ok but 95% charge a lot.

cafe750 · « **Reply #33 on:** February 08, 2009, 07:42:10 PM »

Quote from: eldar, Master of the K8 Thunder! on February 08, 2009, 07:37:03 PM

I do not have a beemer. They are the same as any dealer and charge a lot. Fail to see why you got so jumpy on that. If I went into university motors, I would get charged a #$%*load but then they just built a new shop.

Same goes with auto shops. Some are ok but 95% charge a lot.

Well, being that I'm a parts guy at a beemer shop, I get a little touchy when someone says "Well you know bmw, they want to do all the work and rape you sideways. " Thats all.

eldar · « **Reply #34 on:** February 08, 2009, 08:23:01 PM »

Well I feel ALL autos and bikes are overpriced but that is just me.

Terry in Australia · « **Reply #35 on:** February 11, 2009, 03:40:16 AM »

Quote from: Pillage on February 08, 2009, 08:15:52 AM

Well alright, the SEARCH function actually worked out for a change!
Thanks for the info Terry, I need new tires on my 78F. It clearly has tubes installed but the rims are clearly marked Tubeless. Anyway that's what I'll try to do. I've had great luck with Bridgestone BT54's, BT020 & BT021's over the years so the BT45's seem like the logical choice. Thanks again,
Pillage
BTW, You've got a very sharp "F", nice pic.

[/quote]

Go for it mate, the BT45's are the best tire I've ever had, and I'll continue to put them on every bike I buy, until something better comes along.

And thanks for the compliment, I must clean that old bugger up and take it for a ride, it's covered in about an inch of dust at the moment, ha ha!

On second thoughts, my favorite riding country is still on fire, so I might have to wait a tad longer............

fishhead · « **Reply #36 on:** February 11, 2009, 06:16:17 AM »

Here's a link showing the difference between the tube type rims and tubeless rims (Kawasaki, Honda will be very simular). The ridge on the tubeless rim looks bigger than it actually is, but will be there on a tubeless rim to keep the bead from loosing it seal.

http://kzrider.com/index.php?option=com_fireboard&Itemid=107&func=view&id=208793&catid=5#208793

I dont know if you have to sign up to see the link.

eldar · « **Reply #37 on:** February 11, 2009, 07:52:45 AM »

Seeing that difference, I have to wonder if it might be possible to weld a uniform bead to create that ridge on both sides.

I suppose everything has to be weighed against the safety factor and how much a person wants to risk.

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Author Topic: Tires, Tube or Tubeless: '78 cb750f comstar wheels (Read 17199 times)

troppo

Pillage

eldar

eldar

eldar

eldar

eldar