Lotus Elan

Tyres again - Vredestein 155 HR13 78H Sprint

PostPost by: pereirac » Fri Feb 04, 2011 6:43 pm

Well tyres arrived today, 1 week for delivery from Germany pretty good. They really are HR rated and the code suggests they were made in Feb last year so well pleased. Next thing is to get them fitted to the car and give them a go, But I might wait until the weather improves a bit first.

Tyres look nice and period as well so far so good. They may not be Michelins, but they have the correct speed rating. They were made in the Netherlands as well and not some unknown city in the far east :-)

Carl
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PostPost by: LoTex » Sun Feb 06, 2011 5:18 pm

I'm currently thinking about changing out my tires as well. This will be my third set since I bought the car in 1980. I've always had 155R13s on but I don't recall what size tires were on it when I bought it. Everyone in this thread has mentioned 155R13s, but in Brian Buckland's superb manual on Elans he notes that originally the 155R13s only went on S4 and later models, prior to that (S1-S3) it was 145R13. As I have an early S2, I'm wondering if I should go for 145R13s- any thoughts on what differences if any between the two sizes in terms of handling/wear?

Thanks,

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PostPost by: Galwaylotus » Sun Feb 06, 2011 9:08 pm

This thread got me thinking and I started Googling tyres. I came across a valuable website but there's so much in it it will take a while to investigate it all. http://www.barrystiretech.com/index.html
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PostPost by: Ross Robbins » Sun Feb 06, 2011 11:16 pm

Steve,
While I understand your thought about originality, the real question for me was fit; whether a 155 size would fit on my S2. Well they do! I have now put over 5,000 miles on my S2 with 155/80 X 13 SA4 tires from Discount Tire for $39.00 each. No they are not H rated, No they are not Michelin, or Sprint but I am sure they are better than anything one could buy in the 1960's for an Elan and they are right down the street at your local Discount Tire shop. Here is a link if you are interested: http://www.discounttire.com/dtcs/findTireDetail.do?tc=KAZPA2&c=1&rcz=80123&pc=15866&ar=80&rf=true&cf=false&rd=13&sw=false&rc=CODINT&cs=155

I would strongly recommend the 155 size as they give a bit better speed per rev ratio than the 145 as well as a bit more tread area, both of which I find beneficial..
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PostPost by: Galwaylotus » Mon Feb 07, 2011 6:46 pm

Going back to the website Barry's Tire Tech, one point stood out when I read it. He was talking about speed testing (lab conditions) and his conclusion came in this excerpt.

"To further complicate matters: Almost all tire failures occur in S and T rated tires. Hardly any occur in H and higher speed rated tires.

I recommend that everyone use a minimum of an "H" speed rating."[/

The author is a tire/tyre engineer with 30+ years in the industry. It made my mind up for me - H rated tyres are what I'll be purchasing for my Elan.
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PostPost by: msd1107 » Mon Feb 07, 2011 7:00 pm

It is sometimes difficult to even find a tyre that fits our Elans.

However, an important consideration selecting a tyre is the speed rating - that letter following the tyre size or load designator.

Briefly stated, many tyres available in sizes for our Elans will be rated S or T. These are usually suitable for low speed sedans. For many of us, the minimum speed rating should be H, with modified cars getting V rated tyres.

You are not going to find any H or V rated tyres in the $50 price bracket. But to be realistic, the low weight of the Elan allows it to operate with S or T rated tyres provided you drive cautiously.

Expectations for personal safety are a personal trade off. Previous threads have addressed the relative safety driving on tyres more than 5 years past their manufacturing date - the point that manufacturers recommend replacement.

So keep all these considerations in mind.

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PostPost by: Galwaylotus » Mon Feb 07, 2011 7:35 pm

msd1107 wrote:You are not going to find any H or V rated tyres in the $50 price bracket. But to be realistic, the low weight of the Elan allows it to operate with S or T rated tyres provided you drive cautiously.

That seems at odds with owning a Lotus! :lol:
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PostPost by: pereirac » Mon Feb 07, 2011 8:10 pm

My HR rated tyres were ?53.00 each, given todays exchange rate that's not much more than $50!!

Scary

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PostPost by: Galwaylotus » Tue Feb 08, 2011 6:56 pm

pereirac wrote:My HR rated tyres were ?53.00 each, given todays exchange rate that's not much more than $50!!

Scary

Carl

Uh, Carl, I don't know where you exchange currencies but the Stg/USD rate this morning shows: 53.00 GBP = 85.4184 USD! (ref XE.com) :shock:
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PostPost by: LoTex » Sun Feb 13, 2011 4:34 pm

Ross,

Thanks for your perspective on tires. I too currently have a set of 4 that I got at Discount Tire some years back. No, I don't drive the car hard so those are always an option but I like the idea of upgrading to a better rated tire and may go with the 145s (original) instead of the 155s. I checked and 145s are not available at Discount Tire.


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PostPost by: Ross Robbins » Sun Feb 13, 2011 9:35 pm

Steve,

I don't know where in the USA you can get 145 X 13 tires. Perhaps at Coker Tire, Universal or Lucas, the three vintage tire companies I know. I bought some repro Pirelli Cinturatos for my Elite from Lucas but boy are expensive and they are not as good as the SA4 tires on my Elan in my opinion. My understanding of the speed ratings on tires is that an H rating is for sustained speeds up to 130 mph while the S rating is up to a sustained 112 mph and T is 118mph. I don't know about you but the only place I have ever gotten close to needing a higher rating was when we went around Talladaga Speedway at LOG 29 and for about five minutes I was near 100 mph. At that point I was more worried about overheating and oil pressure drop than I was about my tires failing. :oops:

I drive quite "briskly" as anyone who knows me will attest and I find the S rated SA4 tires in the 155 size to be very smooth, predictable and tenacious enough for any road work and some light track work. I guess I don't know what all the fuss is about for H rated tires for a street driven Elan. :roll:
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PostPost by: Ross Robbins » Sun Feb 13, 2011 9:39 pm

Oh, I forgot to mention that the biggest issue we all face is time...that is, tires that are degraded by age well before their tread is significantly worn down. I would be much more concerned about an H rated Michelin that was eight years old than an S rated SA4 that I fitted last year. This is especially true for cars spending a lot of time in the sun and in a built up area where there is industry as ozone is a bitter enemy of rubber.
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PostPost by: Galwaylotus » Mon Feb 14, 2011 11:34 am

I certainly agree with the tyre aging issue. Regarding the H rating, Barry's Tire Tech website, written by a tyre engineer with many years in the industry has the following conclusion:
"To get a tire to pass an H speed rating almost requires the tire to have an overlay - commonly called a "cap ply" and nylon is a commonly used material.

This overlay restricts the growth of the tire due to centrifugal forces as well as the movement caused by the standing wave. Not only does this result in reduced stresses in the tire, it also reduces heat generation.

Adding further overlay layers results in higher speed capability. That is, you achieve higher speed capability with just changes in construction. Rubber compound changes are almost incidental.
To further complicate matters: Almost all tire failures occur in S and T rated tires. Hardly any occur in H and higher speed rated tires.

I recommend that everyone use a minimum of an "H" speed rating."


I'll certainly be looking for H-rated tyres for my Elan.
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PostPost by: Galwaylotus » Mon Feb 14, 2011 1:01 pm

...and a bit more from the same page.
"Are there situations where the actual speed a tire is capable of withstanding different than the test would indicate?

The answer is: "Yes!"

Normally, new tires are tested. John Baldwin tested some older, but unused tires and found that the speed capability had deteriorated 2 steps. Ref: J. M. Baldwin, "Field Aging of Tires, Part 1" presented at a meeting of the Fall, 2003 meeting of the American Chemical Society - Rubber Division

This makes sense against the backdrop that rubber degrades over time. Even a really old tire has trouble just holding air pressure without coming apart. This was not an exhaustive study. It was only done to illustrate a point. I think further work needs to be done in this area.

What about the speed capability of tires that are inflated to a lower pressure, but properly loaded for that pressure?

John Baldwin (again) also tested this and found a 2 step drop there as well. This was also not an exhaustive study and more work is needed. Ref: J. M. Baldwin, "High Speed Testing Of Tires and the Use of Constant Deflection," presented at a meeting of the Tire Society, Akron, OH, September 23-24, 2003.

Hopefully by now you will realize that the speed capability of a tire could be quite less than the speed rating. If you add up what is known, you could be looking at a 6 step drop - and those are just the issues that are known!"


This is a site worth viewing. http://www.barrystiretech.com
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PostPost by: summerinmaine » Mon Feb 14, 2011 4:45 pm

Galwaylotus wrote:I certainly agree with the tyre aging issue. Regarding the H rating, Barry's Tire Tech website, written by a tyre engineer with many years in the industry has the following conclusion:
"To get a tire to pass an H speed rating almost requires the tire to have an overlay - commonly called a "cap ply" and nylon is a commonly used material.

This overlay restricts the growth of the tire due to centrifugal forces as well as the movement caused by the standing wave. Not only does this result in reduced stresses in the tire, it also reduces heat generation.

Adding further overlay layers results in higher speed capability. That is, you achieve higher speed capability with just changes in construction. Rubber compound changes are almost incidental.
To further complicate matters: Almost all tire failures occur in S and T rated tires. Hardly any occur in H and higher speed rated tires.

I recommend that everyone use a minimum of an "H" speed rating."



I'll certainly be looking for H-rated tyres for my Elan.



This is the explanation I received years ago: That there was a major breakpoint in the construction techniques for tires between the S/T and below versus the H and above. It's the main reason why I try never to buy any but H rated tires.
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