Tube to tubeless conversion

[tomcat24551]

The guy that mounts my tires (and who used to race bikes himself) says that it is somewhat risky to mount tubeless tires on cast wheels not marked for tubeless tires. This is because if the tire should suddenly lose air pressure when you are leaned over pretty hard, there is nothing to keep the tire's bead from sliding down into the well with disastrous results. He says he's seen it happen--on tires he's mounted without tubes on early-type cast wheels.

This is apparently why the manufacturers changed to a wheel that was made with a raised ridge at the edge of that center well--the ridge acts as a barrier to the tire bead slipping down into the well.

You can see a short discussion with drawings in the Continental Motorcycle Tire Tech manual at this site:

http://www.conti-online.com/generato...andbuch_uv.pdf

See page 133 (or 137, depending on how your browser numbers the pages).

Motorcycling is risky enough as it is. Why add to it? A good quality tube costs less than $20. I think my body is worth it!

Tomcat

[mark]

The guy that mounts my tires (and who used to race bikes himself) says that it is somewhat risky to mount tubeless tires on cast wheels not marked for tubeless tires. This is because if the tire should suddenly lose air pressure when you are leaned over pretty hard, there is nothing to keep the tire's bead from sliding down into the well with disastrous results. He says he's seen it happen--on tires he's mounted without tubes on early-type cast wheels.

This is apparently why the manufacturers changed to a wheel that was made with a raised ridge at the edge of that center well--the ridge acts as a barrier to the tire bead slipping down into the well.

You can see a short discussion with drawings in the Continental Motorcycle Tire Tech manual at this site:

http://www.conti-online.com/generator/www/de/de/continental/motorrad/themen/download/handbuch_uv.pdf

See page 133 (or 137, depending on how your browser numbers the pages).

Motorcycling is risky enough as it is. Why add to it? A good quality tube costs less than $20. I think my body is worth it!

Tomcat

Your point is valid and has merit for me because I've heard some in the "field" make the same one. Others I've talked with say that the risk is so small to be almost non-existant. I've just had to make a decision that I'm comfortable with.

Just a question however (I really am curious, not trying to prove a point). You're in a corner with a tire with a tube on it and you suddenly totally lose air pressure. How does the tube keep the tire in place on an old style rim? I don't get how a flat tube helps you.

[earlfor]

Just a question however (I really am curious, not trying to prove a point). You're in a corner with a tire with a tube on it and you suddenly totally lose air pressure. How does the tube keep the tire in place on an old style rim? I don't get how a flat tube helps you.

It doesnt help at all. The only thing a tube may do is allow the tire to deflate more slowly. A blowout on a tubeless tire is instantaneous (or close to it). With a tube, the tube will likely quickly deflate but not instantly. I dont believe either is more prone to separating from the rim.

If you blow a tire in a corner, either way, methinks there will be a problem coming shortly. LOL

Earl

[Steve]

It doesnt help at all. The only thing a tube may do is allow the tire to deflate more slowly. A blowout on a tubeless tire is instantaneous (or close to it). With a tube, the tube will likely quickly deflate but not instantly. I dont believe either is more prone to separating from the rim.

I beg to differ. The only time I have seen a tube deflate slowly is when the valve core is leaking. Any other time it has been rather dramatic.

If you stop for a moment and think about it, the whole reason you have a tube in the first place is because the tire can not hold the air on its own. Now that the tube is not holding air, how do you expect the tire to do it?

I have personally experienced a rather quick deflation (about 30 seconds) of a front tire on my KZ650 many, many years ago, with no bad concequences. On the other hand, I have also experienced a blowout of a rear tire on my KZ1300, which totalled the bike.

The fact that you have a tube-type or a tubeless tire and/or rim really does not have much to do with it. What causes the loss of air will have a much greater impact on the outcome of the situation.


.

[tomcat24551]

I guess I think of the situation this way:

Some group of engineers probably thought long and hard about putting that raised ridge next to the center well in the tubeless wheel, and there must have been good reasons prompting them to do it.

And management had to approve the extra cost--which they did, probably so the company could cover its rear end in court.

Then probably the whole industry trade group looked at the problem and approved the solution, probably again for liability reasons.

But we don't have the data the industry used in making its decisions, so I'm not willing to second guess 'em. If the wheel doesn't say "tubeless tire applicable", I use a good quality tube. I like to think the tube's bulk might tend to fill up the center of the wheel and discourage the bead from slipping into the center well, but, of course, that's just a guess.

In the end, every rider has to make a decision he's comfortable with.

Tomcat

[argonsagas]

I beg to differ. The only time I have seen a tube deflate slowly is when the valve core is leaking. Any other time it has been rather dramatic.

If you stop for a moment and think about it, the whole reason you have a tube in the first place is because the tire can not hold the air on its own. Now that the tube is not holding air, how do you expect the tire to do it?

I have personally experienced a rather quick deflation (about 30 seconds) of a front tire on my KZ650 many, many years ago, with no bad concequences. On the other hand, I have also experienced a blowout of a rear tire on my KZ1300, which totalled the bike.

The fact that you have a tube-type or a tubeless tire and/or rim really does not have much to do with it. What causes the loss of air will have a much greater impact on the outcome of the situation.


.

I have experienced blow-outs and slow losses with tubes and tubeless tires. On the bike I have never had a blowout on the front, and only a slow loss on a tubeless tire.



I have been very lucky as most flats in my experience have occurred due to puncture, and the leak was unimportant as I discovered the problem while the bike was parked.

In the car I have had tube tires go slowly and RIGHT NOW. It is not the tire itself that retains pressure when the tube is punctured, but the remaining pressure within the tube that keeps it pressed against the inner walls of the tire that can slow the release. This usually happens in the case of a small puncture, and where the casing of the tire is not severely damaged. Severe damage to the tire casing leads to a like damage of the tube, which means an instantaneous and total loss of pressure.

[earlfor]

I beg to differ. The only time I have seen a tube deflate slowly is when the valve core is leaking. Any other time it has been rather dramatic.

.

I did say a tube MAY allow the tire to deflate slower. It depends on the size of the hole.

Earl

[themess]

Tires loose air through several routes:
1) spoke holes! Cast rims are needed to hold air.
2) Between rim and bead - The rim and bead profiles must match each other quite closely. The rim must be smooth and free of rust. Bead wire is stiff, and it usually kinks when a tires is dismounted. Kinked beads seal poorly. Rubber around the bead must be soft enough to fill in mismatches between bead and rim, but mounting and dismounting damage the rubber easily.
3) Through the valve - Usually not a problem, but valves should be replaced with tires to be safe.
4) Through the tire itself - Most types of rubber are porous. Everyone knows that balloons lose air quickly. Thick rubber holds air better. But tire cords bleed air quickly. The thickness of the sidewall, the thinnest part, is what matters most, and the distance from the inside of the tire to the nearest cords.
Inner tubes are made from butyl rubber, which is much less permeable to air than normal rubber. Butyl rubber tears very easily. Tiny amounts of contamination can make a tube leak or tear. Lots of tube factories are too dirty, and contamination is common in them.
Tubeless tires have an innerliner on the inside of the tire. Innerliners ae made from chlorobutyl or bromobutyl rubber. Butyl rubber holds air better, but it won't stick to the rubber in the tire carcass. Chlorobutyl and bromobutyl rubbers will stick. The innerliner must surround the bead, to seal against the rim. Butyl rubbers are hard, so they don't seal well against the rim unless the rim is clean and undamaged, and the bead is molded exactly and undamaged.
The innerliner is made in several thin layers, so thin that you can almost see through them. The chance that one layer will have a small imperfection is relatively high, but the chance that two or three layers will have imperfections at exactly the same place is very low. Because the innerliner adheres to the tire carcass, it can't rip or tear if it is suddenly punctured. Usually. Damage to a sidewall can cause the sidewall to tear completely open. When a clean puncture occurs in the tread area, a tubeless tire will probably hold air much longer than a tubed tire.
5) Through the rim itself. Some processes for making rims let the metal itself be porous enough to leak air out.

I don't know why tube type rims don't have the hump to help keep the bead seated in case of pressure loss. Here's a guess. Maybe someone figured out that, when the bead stays seated despite air loss, the driver is much less likely to lose control. Manufacturers (or the DOT) might have decided that when rims were made to accomodate tubeless tires, the bead lock feature should be incorporated at the same time. Just a guess.

The first GSes had spoked rims and tubes. I think that in the second model year, GSes sported cast rims. GSR has had many threads on this topic. It seems that the first cast rims were not suitable for tubeless tires. I'm pretty sure that all 1982 and later cast rims were good for tubeless tires, and think that most 1980s and 1981s were also.

The change from tube-type to tubeless cast rims seems to have been what manufacturers often call a "rolling change". A better part gets built into some bikes before the specs require it. Some riders have successfully used tubeless tires on cast rims not marked tubeless. So we know that before the word "tubeless" was cast into the rim, the quality was there. But we don't know how when this started. Nor do we know if all models changed this way at the same time. Or even if the front rim was OK for tubeless and the rear rim on the same bike wasn't.

A well made, well designed tubless tire, mounted properly on a well made, clean rim with a good valve, unless it is damaged, should not need to have air put in it more than once per year. I once ran a set of car tires 2 1/2 years without adding air. Minor problems with the rim, valve or kinked beads might require adding air every couple of months. If you have to add air as often as once per month, there is a problem that should be found and repaired. That being said, bikers should be checking air at least monthly with a gauge, and at least weekly with a thumb.

(I worked a long time in tire factories.)

[rphillips]

I'll say this again, at the risk of being wrong. I don't remember tubeless motorcycle tires, per 1979. If there were no tubeless tires when the early cast wheels were made, why would any co. stamp "TUBELESS" on the rim. I would rather think the cast wheels came first, then the tire mfg realized the cast wheels, with no spoke holes, would hold air without the use of tubes, and then started the tubeless tires. If the tubeless tires came first, they had to be tested on wheels that didn't have "TUBELESS" stamped on them, as nobody would put "TUBELESS" on the rim, if there were no tubeless tires. After the introduction of tubeless motorcycle tires, of course the bike mfg wanted to advertise you can use these new tubeless tires on our rims, thus the "TUBELESS" stamped rims. Who knows where to find out when the tubeless motorcycle tires were introduced for normal customer use?

[hp1000s]

Excellent discussion on an interesting subject....alot of great and informed input! Thanks,
Hugh

[tomcat24551]

Here is a little more info that I probably should have put in an earlier post.

I bought my '79 GS 850 in 1980 from the original purchaser when it had 4500 miles on it. The bike's manufacture date is 12/78.

The front wheel is the original Suzuki OEM cast wheel (MT 1.85x19) by Enkei and it has a date 11/78 embossed into it. It is not marked "Tubeless Tire Applicable".

The rear wheel is also original Suzuki OEM cast wheel by Enkei and it has the date 10/78 embossed into it. It is size MT 2.50x17 but it is clearly marked "Tubeless Tire Applicable".

So, for what it's worth, here we have a tubeless wheel made a month before a narrower, identically appearing but tube type wheel. I would have thought that the natural evolution of design would have put the tubeless wheel later than the tube type. What gives?

Maybe the narrow width of the front wheel is the problem. Later 850's with front wheels marked "Tubeless Tire Applicable" used an MT 2.15x19 wheel--but they also have the raised ridge.

I replaced the rear tire on this bike in Aug 2004, but to be honest, I don't remember if I ever noticed whether it had a raised ridge on both sides of the wheel's center well or not. I have never been concerned because the wheel says to go tubeless and that's what I do. I use a tube in the front 'cause that's what it says to do (so to speak)!

There was a British guy named Tony Mills who used to manage Dunlop's Motorcycle Tire operations in the U.S. in the 70's and 80's, I think. If anybody in New York knows of him, they might be able to get him to shed some light on this tube vs tubeless discussion.

Tomcat

[themess]

Iteresting info, tomcat. You have established that at least some 79s came with tubeless cast wheels, and that my theory of a "rolling change" is quite possible. If I had your bike and wheels, I'd probably choose tires the way that you do. Or else buy a newer front rim on Ebay to go to tubeless all around.

[jknappsax]

Argonsas, Earl

Argonsas, You're absolutely correct about Slime and centrifugal force. DUH, what was I thinking? Oh, that's right,NOTHING! But it's the FIRST time that has EVER happened!
Earl, that's a great solution for this! I never thought of this, and I use barrier paint!

[boris]

well ive just gone from tube to tubeless on non tubeless marked rims lol
will keep my eye on them to see if their is any loss of air

my bikes a gs450e 1987
so im hoping that by 1987 stock they had sorted the porus issues out

[GS750GUY]

Tube to tubeles wheels

I mounted new tubless tires on my 1978 originally tubed cast wheels a month ago, used soapy water to check for leaks at the time of mounting, found no bubbles, inflated to 25 lbs and they have been at 25 lbs ever since.
GS750Guy