Topic: 78 cb 750F with stock honda mag wheels has tubes

[scottly]

the bead on my tube type comstars is a straight taper with  grooves radiating out from the center of the wheel (I suspect the grooves are there to keep the tire from spinning on the rim).  I've heard that tubeless rims have an extra "lip" in the tire bead area to catch the bead.

The grooves may be the big difference, as they might allow the air to leak? I've seen tubeless rims both with the extra lip, and without, but I've never seen radial grooves on a tubeless rim..

[jtb]

The comstars on my 77 are stamped "Tubeless".   Wouldn't have converted them otherwise.

[garyS-NJ]

are the comstars on your '77 stock?  I don't understand why/how the comstars on my '78 750F are not marked..  I'm thinking mine are stock.  wait do you have a K model?  rim sizes were different.

[Steve_K]

I have Henry Abe wheels and I put tubes in them.  The mechanic(who I trust in stuff like this) said I could run tubeless on either the front or rear.( I don't remember which)  He also said that the rim looks different on the inside then modern cast wheels.  So I went with tubes for peace of mind. 
Steve
 

[TwoTired]

The comstars on my 77 are stamped "Tubeless".   Wouldn't have converted them otherwise.

Well, that's good to hear.  Did you drill the stem hole to "convert them"?

I'm baffled as to why your 77 has tubeless rims, yet all three of my 750's including a 78 have non-tubeless wheels with the small valve stem hole.  2.25x18 rear and 1.85x19 front.
I checked my 79 Cx500 Comstars. Front rim is stamped "Tubeless Tire Applicable"  But, still with small valve stem hole for a tube stem.  Rear rim has a rubber tubeless stem installed!
The 81 GWing has a tubeless stem on front Comstar, and (I think) one on rear as well (It's a metal stem rather than all rubber like the front).  They are stamped "Tubeless Tire Applicable" as well.

I found this on Wiki in the description of the CX-500:
The original Com-Star wheels combine the flexibility of spoked wheels (without the maintenance burden) with the strength and tubeless characteristics of one-piece wheels. This was one of the first production motorcycles to be equipped with tubeless tires along with the CBX six. Honda introduced the Com-Star wheels a year or so earlier on the CB250T/400T Dream as well as on the CB750F2 and GL1000 Gold Wing, although these featured standard rims that demanded inner tubes to be used.

Cheers,

[scottly]

The tubeless rims I have seen use metal valve-stems, with rubber sealing washers. The washers have a lip on the inside, and I did have to open the stem holes slightly in the Morris wheels to allow the lip to fit properly into the opening. I used a tapered ream, from both sides, so the lip on the washer is free to enter, then as the nut is tightened down, the washer is compressed both radially and laterally.

[jtb]

TT, yes I drilled the hole to convert them.  They are in fact stamped tubeless.

[Old Scrambler]

FWIW..........we are paying attention to the tire specs

Please do not insert tubes in radial tires........unless you like road-rash

A local CB160 racer is now on crutches with a broken leg because he did not change the tubes after one season of racing with less than 500 miles on new Bridgestone Radials with tubes on wire-spoked valanced aluminum rims.

[garyS-NJ]

tubes in radials?  never thought of it.  just looking at my comstars I assumed they were tubeless and I initially looked for radial tires and after finding almost nothing for my bike and a little research, concluded my old gal needed the bias tires.  ended up with the BT45V's.  120-90-18 and a 100-90-19. but you can't run a tube in a radial tire?  and the road racer you spoke of had spoke wheels and radial tires, and should not have run tubes or should have just changed tubes every season?

[Old Scrambler]

Some times only certain tires are available to fit certain rims.........so if you have to mix radial tires with tubes (vintage road racing, MX, Ice-racing, Observed Trials, Land-Speed racing, etc.) the strong recommendation is to change tubes often because of chaffing at the side-wall flex. The rules-makers of the various sanctioning-bodies often require V-rated tires. The opposite is applied for observed trials and 'hero" riders in dual-sport events.

[seanbarney41]

What advantage is there to having tubeless tires anyway?...besides a small weight savings?

[Old Scrambler]

Sean......several positives for radial tires include much improved traction, especially on wet surfaces, easy-fix flats on the road (or far OFF of the road), and the weight savings - especially at high-speeds and/or on rough surfaces.

An extreme example of improved radial traction is to watch (or participate) in observed trials and muddy dual-sports events.  For our everyday CB750s, the bias-ply are just fine and usually less costly.   

[TwoTired]

What advantage is there to having tubeless tires anyway?...besides a small weight savings?

Tires run cooler.  The tube chafes on the tire carcass as it rolls and the contact area "squirms.
Tubeless, sidewalls are usually stiffer .
If the bead lock stays locked, almost all punctures go down slowly and "blowouts" are rare.

If the tire carcass gets a tear, a tubeless tire will still go down slowly, which gives you some warning.
If the tube pokes out of the carcass, it forms an exterior bubble, and once that is worn though or poked, the air escapes very fast, boom.

I was checking out the Goldwing shop manual, and found this drawing and entry in the Wheels and tires section.
I was rather surprised that the cross section didn't show a "bead lock" ridge feature incorporated into the rim design.  However, it does show an "inner liner" which appears to act as a tube, kinda, sealer at the bead seat area.  I can't imagine the liner would do anything beneficial to keep the bead in it's seat, though.
I've never seen one of these inner liners.  But, it makes me curious if Comstar's early tubeless designs expect the liner in lieu of a bead lock feature.
These were kind of the early days of production tubeless rims.  I wonder when the rim design changed to rim lock instead of "inner liner"?

Anyone remember back that far?

Cheers,

[scottly]

What advantage is there to having tubeless tires anyway?...besides a small weight savings?

The main advantage for me is the ability to be able to repair a puncture without having to remove the tire. Before this year's relay, I bought a very compact repair kit, with CO2 cartridges, plugs, plug needle etc. The whole kit is about 5x6x1.5". A lot easier to carry than tire spoons.

[krusty]

After reading this thread I went out to the garage and checked the rims of my recently acquired 5/78 F2. No mention of 'Tubeless' anywhere on the rims and it has tubes fitted. I checked my F2 parts list and it shows tyres with tubes, no mention of any tubeless version for this model.
I'll go with what Mr Honda has printed.

[garyS-NJ]

two tired - I thought radials had softer sidewalls which allowed them to roll over in turns and keep the contact patch large..  I think I remember reading this somewhere recently when I bought new tires for my bike annd because of this, they don't make "tall" tubeless tires like the 4"X18 square tire stock to my bike.  IDK but this roll over is exactly what I saw when I started driving with bias plys on my 68 chevell and my buddy bought a newer monte with radials.  I could see & feel the radials roll over in turns (we used to race and run together down our local swervy highway) but they kept better traction than the bias plys.  I didn't like the radials anyway because with my bais plys I could feel the limits of traction in turns by scrubbing the tires (little bumps on the steering wheel) and the tires would break traction (but controlled) with little erp", erp, erp sounds.

I would love to have tubeless radials or at least tubeless tires on my 78 but for now it is what it is and last night on the new skins (I did fork seals too), it felt like a new bike.

as for your GW illustration, I think that inner liner and chafer are features in the tire that allow you to safely run a tube.  I like that they note max puncture for a plug (0.236", what retards like someone can see hundredths or thousandths of an inch in a puncture) but they should have added that you shouldn't fix a sidewall puncture.

[TwoTired]

two tired - I thought radials had softer sidewalls which allowed them to roll over in turns and keep the contact patch large.. 

Could be.  But, I was comparing tubeless tires with tube type tires w.r.t. sidewall stiffness.
I'm not sure I've seen a radial tire in tubeless, though.
Radial vs Bias ply refer to how the cords in the carcass are arranged.  I know Bias ply tires were offered in both tube type and tubeless.

Further, the side stresses on the tread relative to rim are quite different for cars, as the tries on cars don't lean into corners as MC tires do.  They stay pretty near 90 degrees to road surface in turns.

I would love to have tubeless radials or at least tubeless tires on my 78 but for now it is what it is and last night on the new skins (I did fork seals too), it felt like a new bike.

I'm not sure I'd recommend the radials on an SOHC4.  I recall something about suspension tuning changes required due to their construction.  (memory of this is fuzzy.  Perhaps it was mixing radial and bias type on the same bike.)  However, I have no issue with using tubeless tires on the SOHC4.  It just believe it should have a tube installed inside it, unless the rim manufacturer designed it for tubeless operation.

Cheers,

as for your GW illustration, I think that inner liner and chafer are features in the tire that allow you to safely run a tube. 

That makes sense.  Although, in the drawing they clearly show a tubeless tire stem in cross section, which seems to be incongruous with the supposition. 

I like that they note max puncture for a plug (0.236")...

That's an artifact of metric conversion.  Bike engineers built in metric.  The manual's tech writers for the export market used a calculator to get inch equivalents.  They just printed what came up on the display. 

Cheers,

[garyS-NJ]

When I was researching tires for this change, the question of radial vs bias came up and I read some stuff saying that the old bikes were designed with suspension for a bias ply tire but also found some writer riders that said they put radials on their older "bias ply design" bikes and found a great improvement in ride/handling.  My decision became easier because the radials were much more expensive and hard to get in my sizing (and the selection became even tighter when I looked at actual mfr specs for OD which differes from the width X aspect ratio.  I wanted to maintain the relative "stance" of my 750F with the rear a 1/2 taller than the front.).

that said, and with minimal research, I tend to believe that motorcycle tires are trending towards radials (and I don't think any radials run with tubes).  given the option, I'd try a set of radials on my 750F maybe with a wheel change that will get me a wider tire.).  just think about it, there are already so many variables in terms of tire types and fork oil that people use and get used to and debate..  I ended up with the BT45V's in 100/90/19 and 120/90/18 because they were rated for my rims while the avons I really wanted would only spec a 110/90/18 for my 2,15" rear rim (and give me a 0.6" height delta vs the 0.4" delta from the bridgestones).  I also made my own mix of fork oil (2oz straight 30, 2oz ATF, 1,5oz bahr jack oil) and the package rode like a dream last night (I cleaned/scuffed the tires after mounting so I felt ok leaning on it last night.,.).  looking forward to see how the all balls fork seals hold up to my fork oil mix.

[shinyribs]

FWIW, I recently changed from bias ply to radials on my 76F and LOVE THEM! Of course, I also changed from Dunlop 404's ( hard as a brick) to Shinko 712's ( super gummy) . Either way, the radials seem fine. The 712's do seem to have a rather steep profile and it feels a bit twitchy in parking lot type situations,but they just lay into a curve soooo smooth. I hear some guys on here talk about the CB750's needing to be pushed down to lean into a curve-not with my 712's-it falls into a curve,ya gotta pull it back UP !  I got off point.....

[garyS-NJ]

I don't think that shinko 712 is a radial tire.  especially at the price.  even the shiko site is silent on the construction except to say 4 ply nylon (which I think is bias ply).  Sticky/gummy IDK, perhaps compared to your old dunlop..  I think riders with new tires feel confident and push the tires harder (I know I do as I rode my old skins like I was on ice...).  but a rounder sidewall will make the bike lay over in a turn easier as will less rake.  You may well have gotten less rake by changing the angle of the neck by increasing the height delta between back and front. less rake is a more "agressive stance and will be easier to flop, twitchyer, and less stable in the straights.   My '78 cb750F stock tires diameters have the rear tire 0.5" taller than the front tire.  I had some head shake on decelleration (granted my tires were old and one fork was leaking bad) and recognizing that I was getting rounder sidewall tires, and a bit taller, and I wasn't racing twisties, I was cautions and selected my BT45V's over the avons because the BT's gave 0.4" delta where the avons gave 0.6".  I can't say what got rid of the headshake (cause it's gone with the new tires and slight balancing, and the fork seals) but my bike also seems to lay over easier now as well as run easier straight and over highway grooves.

BTW, I bought a shinko 230 tourmaster for the front of my yam XJ550 and look forward to when I get the matching rear.  nice tire for the money and it's V rated and supposed to be for long high speed running.  your 712 is also considered a cruiser tire but is H rated.  I 've heard the BT45's will wear out soon but I bet they are grippy in all weather and that's most important to me (rather change a tire than a body part).

[shinyribs]

My Shinkos are labeled 100/90R19 and 120/90R19 . I didn't check any literature,but it was my understanding that the 'R' denoted radial. But I could be wrong...I've been wrong before...once,I think?

[freedomgli]

Please do not insert tubes in radial tires........unless you like road-rash

A local CB160 racer is now on crutches with a broken leg because he did not change the tubes after one season of racing with less than 500 miles on new Bridgestone Radials with tubes on wire-spoked valanced aluminum rims.

Yikes!  I'm going to run Continental's new radial race tire for classic bikes (ContiRoadAttack 2 CR) and my supplier didn't mention anything about tubes being an issue.  A quick Google search shows Bridgestone offers an inner tube marketed for use with radial tires but not in the size I need.

[freedomgli]

I fired off an e-mail to Continental just to confirm it's OK to use a regular inner tube (such as Continental E18 or Michelin 18 MF TR4) in their ContiRoadAttack 2 CR tire.  A press release from Continental says, "All are tubeless but can be fitted with an inner tube when used on tube type wheel rims."

http://www.classicmechanics.com/news/2013-01/hi-tech-tyres

[Davidov]

Just to pitch in with the original question.

My 78 750F with Comstars had a tube when I broke it down. So I put a new tube in with the tire replacement.

I'm glad Shinko 712 tires came up, which was a question of my own.

I am running tubes with Shinko 712 tires front and rear. The motorcyclesuperstore.com site lists them as tubeless 4-ply. On this site, all the radial tires are described as "radial".
It never crossed my mind that the 750 could only run bias ply 

[RSchaefer]

Some have done the dyna beads in lieu of rim weights.  You should consider the All Balls roller bearings as they are relatively cheap and a big improvement.  I tried and tried to loosen the lower Allen bolt and got a recommendation from the forum to use a compressor run socket wrench, which I had not tried.  I hit it with the socket wrench and it came right out.  I suspect its the jolt from the compressor that broke it loose.