Rims: B vs J 1

[davide82m]

I am considering changing the tyres of my caravan to stronger ones.
The caravan came with 165R13 86 R (reinforced) tyres.
I found a lot of tyres with same size and 8 PR, i.e. 165R13 94.

I believe the original rims are 5.00B and, often, I see in the tables that these 8 PR tyres need a 5J rim; but this is not always the case.

What do you think about this? Are J and B rims intercahngeable?
Just out of curiosity, why do exist J and B (and others) different profiles?

GT-RADIAL 165R13C (4.0 ~ 5.0 generic)

http://www.gtradial.it/gtradial/italy/tiredetail.asp?mastertireid=ChinaPattern000192&flag=3

GT-RADIAL 165R13C (4.50B;5.00B;5J)

http://webcache.googleusercontent.com/search?q=cache:_xMq9AyD-uoJ:

http://www.gtradial.it/gtradial/ita...ChinaPattern000191&flag=3&hl=it&gl=it&strip=0

Continental
(page 22: 165/80 R13 XL 5.00B and 5J
page 70: 165 R13 C 6PR only J allowed)

http://www.continental.co.za/Uploads/Technical Data Book_2013-2014 Pass,Van, 4x4(1).pdf

Thank you a lot.

 

[CapriRacer]

First, the tire standardizing organizations are supposed to specify the rim contours such that everything is backwards compatible. That is, if a tire was once specified as requiring a B type contour, it will always be compatible for a B contour.

When I look up a 165R13C in ETRTO (European Tyre and Rim Technical Organization), it lists only J type flanges. So I am puzzled by that.

Looking at the specs themselves (B vs J), I see that the height of the B flange is taller with slightly larger radii. The radii don't concern me, but the height does - but only a bit.

Looking in JATMA (Japanese Automobile Tyre Manufacturers Association), I see they list both B and J flanges.

I note that TRA (Tire and Rim Association - the US based group), they only list B flanges for 13" passenger car tires, and only J type flanges for ST tires (the kind for trailers)

So I suspect that there may be issues with the rim (and not the tire) in using a higher inflation pressure with a B type flange and that is reflected in both ETRTO and TRA, but JATMA is saying that it is OK (again, thinking that they are referring to the tire and not the rim).

So I suspect the issue is with the wheels and their ability to withstand a higher inflation pressure and not a tire related issue.

Then the question comes down to this: Are you considering using a higher PR and the higher inflation pressure that comes along with it? If so, there may be issues - BUT - my experience (based on conversations with many folks using trailers in the US)is that there are very rarely wheel flange issues using a higher inflation pressure - that any flange issues are because of the wheel itself and the load on it and not the inflation pressure. Obviously there would be an upper limit on inflation pressure for trailer tires, but that wheel failures don't seem to be an issue within the normal range of values for inflation pressure.

Hope that helps.

 

[davide82m]

So you confirm my dubts.

Right now I wrote to GT Radial and Hankook asking if their 165R13C can be fitted to a B rim.

Looking at the PDF at the link:

http://www.continental.co.za/Uploads/Technical Data Book_2013-2014 Pass,Van, 4x4(1).pdf

on page 91 I see that a size which is quite diferent is the G.
Maybe an higher G measure (i.e. J rim) keeps better the tyre in place with higher pressure.
I feel like probably nothing happens if I fit a 165R13C tyre to my B rim... but I don't want to test the specs myself. Mainly because a tyre coming out of the rim is not nice especially if a person is standing near it. I keep in mind that the 4 or 4,5 bar at which I would inflate the new tyre is quite a bit more than the 3,1 bar that were expected now.
And, at the end, there will be some reason if the B rims are not allowed in the ETRTO table.

It would have been nice if Popeye427 was reading us

By the way I am considering upgrading the tyres because I believe they are a bit undersized for my caravan (I still have to find a facility where I can weight the thing). It is known that in Italy, the caravan from the 70s, 80s and mis-90s have often undersized wheels.
Many users are upgrading their tyres without even knowing anything about B and J rims... and I bet even the people at the tyre shop have not a lot of knowledge.

I attach a couple of photos here to show what happened.

These tyres have always been inflated to the right pressure and I have been checking often that the tyre was not overheating.
I have to say that I discovered the ruptures in the tyre by chance because they were in the inner side. I don't know for how long they have been there.
The tyres were 13 years old at the time BUT I beliebe this kind of rupture is not due to aging because it looks like the polyester plyes have failed, right?

Thank you for sharing your knoledge in this forum.

 

[davide82m]

Sorry, the pictures:

 

[CapriRacer]

First, the problem will not be the tire coming over the rim. The B flanges have the higher heights so if anything, the flanges with the problems would be the J type - the ones now specified. But those aren't issues in any tire that uses J type flanges - and that's pretty much all the passenger car tires.

Second, I concur that many trailer manufacturers used undersized tires - in the US. I didn't know the problem also occurred in Europe - although it makes sense that it would. I think the idea of going up in load carrying capacity is smart.

Today, it seems that trailer manufacturers in the US are still undersizing, but not as bad as the past. Also, the internet has been helpful for identifying tire failures on these kinds of trailers. Before, the only way a trailer manufacturer would know is if they were approached by a consumer - a very unlikely situation.

Further, my dealings with trailer manufacturers is that the engineers there don't really understand how to size a tire - and once they have done it, they tend to ignore it from that point on.

And lastly, the tire failure you have isn't from overloading. Overloading is a fatigue type problem and in a tire that would result in a failure between the layers of fabric - and your cross section reveals that there are none there.

What you have is a crack in the sidewall rubber that may be the result of a manufacturing flaw and aggravated by the age of the tire. Certainly overloading (and underinflating is the same thing) might also cause this to appear sooner, but it isn't a root cause type of thing.

 

[davide82m]

. The B flanges have the higher heights so if anything, the flanges with the problems would be the J type

Maybe there is something I don't understand... but I see on page 91 (

http://www.continental.co.za/Uploads/Technical Data Book_2013-2014 Pass,Van, 4x4(1).pdf)

that the G measure for B rims is only 14,1 mm while for J rims is 17,3 mm; so J rims have higher heights. Am I wrong?

my dealings with trailer manufacturers is that the engineers there don't really understand how to size a tire

I am so shocked! It is not that hard to properly size tyres with some safety margin.

 

[CapriRacer]

. The B flanges have the higher heights so if anything, the flanges with the problems would be the J type

Maybe there is something I don't understand... but I see on page 91 (

http://www.continental.co.za/Uploads/Technical D...)

that the G measure for B rims is only 14,1 mm while for J rims is 17,3 mm; so J rims have higher heights. Am I wrong?

Opps. I got that backwards. Sorry.

And that changes all my thoughts. I now don't think the problem is inflation pressure. I'm now wondering if the issue is standardization - what with the B type flange being a pretty old flange with the J being the newer.

Nevertheless, I don't think there is a compatibility issue with the tire.

my dealings with trailer manufacturers is that the engineers there don't really understand how to size a tire

I am so shocked! It is not that hard to properly size tyres with some safety margin.

Actually it's a matter of learning.

One of the lessons from the Ford/Firestone situation a few years back was that vehicles need to specify tires such that they aren't using more than 85% of their rated load carrying capacity (at the specified pressure). It was quite common for manufacturers of SUV's to specify 100% loadings (when the vehicle was fully loaded). You may have heard about the inflation pressure specified by Ford - and it's not the inflation pressure per se that was the problem. It was the calculated load carrying capacity at that pressure.

When it comes to trailer manufacturers, they do 3 things that they ought to fix.

1) As outlined above, they need to use no more than 85% of the rated load carrying capacity.

2) They need to account for side to side and front to rear loading variation.

3) They need to get real about the speed these trailers are being towed - and specify tires that are capable of that speed.

/end soapbox

 

[davide82m]

Overloading is a fatigue type problem and in a tire that would result in a failure between the layers of fabric - and your cross section reveals that there are none there

Whould you explain a bit more? Overloading causes a very specific kind of failure? What do you means "between the layer of fabric"? This tyre has a single sidewall polyester ply (double on the very first part near the rim).

 

[CapriRacer]

Look at the last photograph. That's a radially cut section of the sidewall.

I am going to start on the inside of the tire and describe the layers going outwards - and I am only going to describe the left side of the section at first.

1) Innermost layer - rubber innerliner - typically made of butyl rubber for air retention.

2) It's hard to see, but there is a slightly blacker layer of rubber next in. That would be a layer of rubber to better adhere the innerliner to the rest of the tire. (butyl is not noted for its adhesion!)

3) Then there is a layer of ply cord. The cords themselves are white, but they are coated with a bonding agent that is orange (see the other photos)

4) Then there is the thick sidewall rubber.

You'll also notice that the left side and the right ride (upper and lower sidewall respectively) are different. If you had included the bead wire in your section, you would have noticed that the ply cords wrap around the bead and end just about in the middle of the section. That is called the "Turnup" - because the ply is turned up around the bead during manufacturing.

And if you had included the bead wires, you would have noticed that on top of the bead wires would be a triangular shaped bit of rubber that smooths the transition of the turnup. (It's on the right side of the photo.) This triangular rubber component is sometimes call a "filler" - because it fills in the area.

Now some basic principles:

Composites tend to fatigue fail between layers, and not through layers. This is as true for carbon fiber as it is for ply cord/rubber layered tires. (Please note that we are discussing fatigue failures, not strength failures)

Typically, a ply fatigue failure will be between the filler and the inside ply cord (as opposed to the turned up ply cord) - and it will follow the ply cord line, not through it. Please note that these kinds of failure are fairly rare as there's been over 100 years of experience of designing this area of the tire, and it is very well understood. (But, admittedly, sometimes there are failures in spite of all that experience.)

But in radial tires, the most highly stressed area is the edges of the belts. A failure in that area is typically between the 2 belts with the top belt detaching from the lower belt as a unit, with the tread rubber still attached to the top belt - commonly called a tread separation. A more technically correct version of the type of failure is a "belt-leaving-belt separation". This is the usual failure for an overloaded (underinflated) radial tire.

But cracks in the lower sidewall area are generally attributed to a combination of a discontinuity in the rubber (in tire manufacturing terms, a "foldover") where the outside rubber folds over itself - and the oxygen attacking the rubber. (I see no other signs of aging cracks, so I am completely discounting age as a factor here).

In the case of a foldover, the severity can be very slight and very severe. The crack will start at the foldover, but not necessarily follow the foldover as the crack grows. Plus, fatigue cracks in the sidewall area tend to be smooth and not jagged (like in the photo) This tells me the crack is trying to follow some sort of discontinuity.

And if you've observed fatigue type failures in other materials, there are typically stress marks before a crack appears - and there are none of those in the photos.

So I think this is likely a manufacturing defect (oh, and I've been trained not to use that word, so I hope you'll excuse me for lapsing into the vernacular.) - a slight one that ordinarily wouldn't have caused an issue.

 

[davide82m]

I love reading nice posts like your one. In my opinion, it is incredibly interesting.
Thank you very much for sharing this information!
By the way, I would like to know more about tyre construction, typical failures and so on. Is there a book which I may read? Other sources. On the internet I find only superficial information and nothing even close to the information you gave on your last post.

Can it be that the failure of my tyres may have been caused by a pothole? The tyres have always been full loaded...

 

[davide82m]

Moreover, I would like to point out that the section of the sidewall in the previous photo is a section of a "healthy" part of the tyre. The section of the bad part is here. It looks like the break gets even inside the "triangle", right? Does this change your diagnosis?

 

[davide82m]

 

[davide82m]

In the last photo you can seed the jagged profile of the cut (don't pay attention to the under cords I cut them).

 

[CapriRacer]

David82m,

Thanks for the additional photos - and yes, that does change things - and this is a part of a disagreement I used to have with other people's diagnosis.

I think that crack is coming from the inside out. I think the crack is the result of impact damage. Not enough damage to fail the cord, but enough to fail the adhesion on the inner ply cord. Instead of following the ply line, the crack is choosing the path of least resistance - which would be the damaged area of the tire. It's a compression failure.

And you've asked about books on the subject.

There are several that I have used over the years.

Rex Grogan had a series of books. Here are some titles that I lifted from a web site:


An Investigator's Guide to Tire Failures
Tire Examination Methods for Police Accident Investigators
Tire Marks as Evidence
The Role of Tires in Motor Vehicle Accidents
At the Scene of the Crime

The latest one is by Tom Giapponi - Tire Forensic Investigation - Analyzing Tire Failures

 

[CapriRacer]

Gosh, I wish this site had an edit function.

Nevertheless, what I forgot to add was that everyone needs to be very careful about what they read on tire failures on the internet.

First, there are websites run by lawyers and they aren't offering truly scientific explanations. They are soliciting business and using the web site to help poison the pond - that is getting uninformed people to buy into a particular line of thinking that supports any plaintiff they might get.

It is sometimes hard to tell that a particular site is run by lawyers, but the key would be if they provide some contact info. That usually reveals a law firm.

Second, is that many folks are offering opinions that are way out of their level of expertise. An example is the use of the term "belt shifting". If someone uses that term, they are just repeating something they heard and just don't have to chops to defend the use of the term. (BTW, belts don't shift. They are locked into the rubber matrix and the term is used to either describe a separation, or is used to incorrectly diagnose irregular wear - thinking that the irregular wear is really a symptom of the belts having changed position.)

But if you want more help, I have a web site that I use to explain some things about tires:

http://www.barrystiretech.com/index.html

You can contact me through that web site. I do answer questions.

 

[davide82m]

Thank you!
I already read a good part of your very interesting website.