Discount Tire refused to sell me any tire for my Fiero with less than a load index of 93. This totally pssed me off because I'm standing there with 91 rated tires that I took off it. And what really ticked me off is that the 93s were not in stock. I called BS on the 93 as ridiculously over conservative (1433 lbs each) but they would not budge. I can't find anywhere what Pontiac recommends, but my math from the door decal comes out to closer to a 74 rating. Anyone else run into this?
there are about 600 lbs. on each front tire and 800 on each rear tire.....They must be doing that for warranty reasons, and they probably don't have any information on the Fiero, so the software goes to some default. I can recommend Tire Rack, who would ship tires to the shop of your choice.
[This message has been edited by Gall757 (edited 04-13-2014).]
I don't know what the spec is but I've about had it with Discount tire. I have no idea where they got that 93. But when I need front tires, I'm ordering them from Tire rack and get them mounted at NTB.
Discount tire has bf Goodrich 90 front/93 rear in jacksonville FL
I refuse to believe that's the correct number for the Fiero.
I just got off the phone with the Discount Tire District Manager. He claims the numbers come directly from the manufacturer. I seriously doubt that GM/Pontiac recommended a load range of 90/93 for the Fiero. My calculations show it's closer to 67 front /80 rear. He said if I'm right he'll give me the tire for free. I don't know that he will admit the computer is wrong, but I believe the the door jamb sticker over the Discount Tire database.
That's the rear axle weight....2000 lbs. sounds about right (for both tires). gtoFormula says that EACH tire has to support that weight.....and maybe Discount Tire thinks that way too. I presumed that the dynamic changes that happen are built into the safety factor of the numbering system, and the consumer just worried about how much weight was on each tire to arrive at the right index number....(like you just did by dividing the number by 2).
[This message has been edited by Gall757 (edited 04-15-2014).]
After a couple of calls to the district manager for Discount Tire he admits he doesn't know how load index is calculated. I'm still trying to figure out how you get from GAWR and GVWR to load index but nobody I've talk to knows. This is why planes crash and ferrys tip over, because people get sloppy and don't know how any of these specs they toss around actually are derived. I guess I'll just give up and buy the higher load tires and save my energy for the next fight, and that is when I want my new tires in the front.
Tire Load Index is normally figured by taking the GVWR and dividing by 4 and then using a Load Index Chart like this one to find the Load Index Number.
But the Fiero is a different animal because the rear is heavier than the front, so I would use the GAWR for the Front and Rear respectively and divide those numbers by 2 like you have done in the post above. I would ask the guy if he thinks your Fiero weighs 5,732 lbs because the tires they are trying to sell you are rated for that heavy of a car. If thats a no-go, call corporate, they apparently need some re-training on tires.
Just go to whatever store you want like TireRack, and buy whatever size you want out the door and have them mounted somewhere else. No one needs to know what kind of car theyre for to mount them. I run into this crap all the time. Ive wanted a battery for everything from my boat to just to charge my RC cars at the track. I got one for my Cessna and just gave them the battery number I wanted. They insisted on knowing what make and I stumped them when I said 77 Cessna...same for the boat, told them 86 Tahiti. They said they werent listed and I just said no kidding, now Ill have my battery please. I hate it when stores wont sell you what you want. If they dont want my money, I just go elsewhere.
You are right. Discount Tire is obviously wrong. If he's going to give you free tires for being right, he better start giving.
Even with a 10% overage on the weight, the minimum load index required still wouldn't be 93. To be a minimum of 93, the car would need to weigh almost double what it actually weighs. I would just buy tires from Tire Rack or somewhere else though, especially if he doesn't give you the free tires like he said he would.
You are right. Discount Tire is obviously wrong. If he's going to give you free tires for being right, he better start giving.
Even with a 10% overage on the weight, the minimum load index required still wouldn't be 93. To be a minimum of 93, the car would need to weigh almost double what it actually weighs. I would just buy tires from Tire Rack or somewhere else though, especially if he doesn't give you the free tires like he said he would.
Yeah I'm done with Discount Tires... the District Manager insists his computer is right...even though he can't explain how. Anyone that thinks a Fiero needs a tire with a load index of 93 doesn't know anything about tires. Anything over 90 is overkill. Roger is right... either sell me the tire or I'm walking... no need to know what I'm going to do with it.
Yeah I'm done with Discount Tires... the District Manager insists his computer is right...even though he can't explain how. Anyone that thinks a Fiero needs a tire with a load index of 93 doesn't know anything about tires. Anything over 90 is overkill. Roger is right... either sell me the tire or I'm walking... no need to know what I'm going to do with it.
Sorry to say the vast majority of Discount Tire's customers are there for a completely different experience. They are not aware of any 'indexes' or 'ratings'...they want a tire that goes around and if something goes wrong they want to take it back and throw it through the window of the store..... So considering that they have to offer a mileage warranty, the Discount people get bound up by red tape....follow inane rules and don't think, your only choice is to buy from somebody else. It would be interesting to hear if they would sell you a tire of your choice even if they did not mount it.
Sorry to say the vast majority of Discount Tire's customers are there for a completely different experience. They are not aware of any 'indexes' or 'ratings'...they want a tire that goes around and if something goes wrong they want to take it back and throw it through the window of the store..... So considering that they have to offer a mileage warranty, the Discount people get bound up by red tape....follow inane rules and don't think, your only choice is to buy from somebody else. It would be interesting to hear if they would sell you a tire of your choice even if they did not mount it.
I though about that tire through the window trick since they are still running that ad after about a billion years.
Considering that I came in with the wheel in my hands and they never saw the car in question they probably wouldn't even sell it regardless if the computer wasn't happy. Next time I'm going to say I have an 85 Benz...and when they ask the model I'll say an 1885 Motorwagen. I wonder if that's in their computer?
I though about that tire through the window trick since they are still running that ad after about a billion years.
Considering that I came in with the wheel in my hands and they never saw the car in question they probably wouldn't even sell it regardless if the computer wasn't happy. Next time I'm going to say I have an 85 Benz...and when they ask the model I'll say an 1885 Motorwagen. I wonder if that's in their computer?
1962 Messerschmitt KR200. Almost certainly won't have that (the web site doesn't). A Benz will probably be in the database.
Originally posted by jscott1: if they have the 1885 Benz I would be impressed.
Ah right. Read 1985 instead of 1885 there. But I'll be impressed if you manage to mount 215/60-15 tires on those wheels, too.
They don't have anything in the database older than like 1952 though, it seems. You can check on the web site. And the web site lists the lowest load rating in matching sets of tires for the 15" Fiero wheels to be 90 front, 93 rear. So yeah, I'm sure their database is stupid. Whoever entered the info did it wrong.
Originally posted by David Hambleton: Maybe you could get free tires from Discount Tire if you show them the TireRack website info:
Serv. Desc: 91S
Even the DiscountTireDirect site shows the same load rating:
Tire Size P215/60R14 91S RWL
Unfortunately, those are still a load rating of 91, which is way more than is really needed on the Fiero. And I doubt it would sway the DM to give free tires as a point of being proven only slightly correct, when the argument is that the requirement is much lower than that.
Unfortunately, those are still a load rating of 91, which is way more than is really needed on the Fiero. And I doubt it would sway the DM to give free tires as a point of being proven only slightly correct, when the argument is that the requirement is much lower than that.
Yeah the smoking gun would be if I could find something from Pontiac or GM that stated the correct load index. But my research suggests load index didn't exist until 1991. I doubt Pontiac went back and created indexes for all their cars no longer in production.
The 1995 Toyota MR2 is listed as using tires with a load rating of 91. That might be an appropriate similar comparison...
Listed as how? Those are the only tires available to purchase from that vendor in that size? It could be that they only have tires with load ratings that high, that will fit the Fiero.
http://www.sizemytires.com/make/toyota/mr2 Heck, this site shows the MR2 with multiple different load index values being used, Was the 93 MR2 really 1000lbs heavier than the 92 model? Also note this site doesn't even list a load index for the years prior to 1992.
It seems like all these tire companies are incorrectly taking the full weight of the vehicle, dividing by 2, and calling that the load index. Understandable if you have hydraulics and want to bounce up onto a single wheel. But in normal conditions, there's no way a single wheel/tire in a Fiero is going to have to bear half the weight of the entire car.
It seems like all these tire companies are incorrectly taking the full weight of the vehicle, dividing by 2, and calling that the load index. Understandable if you have hydraulics and want to bounce up onto a single wheel. But in normal conditions, there's no way a single wheel/tire in a Fiero is going to have to bear half the weight of the entire car.
Yeah my research shows that the Federal Motor Vehicle Safety Standard (FMVSS) 109 was changed in 1991 to require load index to be printed on the tire. I don't know what they used before that time, or if manufacturers created load indexes before that time either. Trying to research per-internet occurrences is really difficult. So for us with 80s cars and earlier there is a lot of misinformation floating around out there.
OK, let's look at more modern hardware. I have a 2005 Ford Freestyle, so I looked up what they recommend for that. Gross Vehicle weight is 5,379 lbs. Divide that by 4 and you get 1,345 lbs.... but Tire Rack is recommending an index of 100 for that car, which is 1,764 Lbs. That is a very big safety factor, but not half the weight of the car. I think they are making this stuff up as they go along. The DOT made them do it, so they are doing it......but they don't care if it's wrong.
OK, let's look at more modern hardware. I have a 2005 Ford Freestyle, so I looked up what they recommend for that. Gross Vehicle weight is 5,379 lbs. Divide that by 4 and you get 1,345 lbs.... but Tire Rack is recommending an index of 100 for that car, which is 1,764 Lbs. That is a very big safety factor, but not half the weight of the car. I think they are making this stuff up as they go along. The DOT made them do it, so they are doing it......but they don't care if it's wrong.
I totally agree. I guess I'm bored because I just read FMVSS 139, (which replaced FMVSS 109 for cars built after 1975) and there is no mention of a safety factor or derating for passenger cars. The only mention of a safety factor is 10% for light trucks when fitted with passenger tires. The FMVSS calculates load index the way you would expect GAWR / 2 = load... look in table for load index. End of story.
I think Discount Tire uses a random number generator to come up with load index and then they quote some generic safety bull crap to justify it with no science or facts backing it up.
Originally posted by jscott1: I totally agree. I guess I'm bored because I just read FMVSS 139, (which replaced FMVSS 109 for cars built after 1975) and there is no mention of a safety factor or derating for passenger cars. The only mention of a safety factor is 10% for light trucks when fitted with passenger tires. The FMVSS calculates load index the way you would expect GAWR / 2 = load... look in table for load index. End of story.
I think Discount Tire uses a random number generator to come up with load index and then they quote some generic safety bull crap to justify it with no science or facts backing it up.
I don't think it's just Discount Tire. Everyone seems to have wrong info, from what I can tell, even Tire Rack (though at least they have a chart you can look at, even if you can't buy tires at the requisite load index for the Fiero from them).
But yeah, I totally agree it's a complete mess. Load index was probably made up by insurance lobbyists, to avoid paying if the tires on your car fail, and don't meet the "required" minimum load index.
I must have really pissed off the tire gods... Next day taking the car for a little cruise with the 95 load index tire and BAM! Hit a pothole and damaged both right side wheels. That ridiculously strong tire transmitted all the load into my wheels apparently. So off those wheels come anyway until I can figure out what to do next.
The pot hole edge deformed the tire far enough that the pot hole edge bent the wheel. The sidewall was squished in between. The lower the profile of the tire the more likely that is to happen. No sidewalls are stiff enough to bend the wheel.
The pot hole edge deformed the tire far enough that the pot hole edge bent the wheel. The sidewall was squished in between. The lower the profile of the tire the more likely that is to happen. No sidewalls are stiff enough to bend the wheel.
Yeah I'm sure you are right, but I got less than 24 hours of use out of the tire before this happened. And the tire never lost pressure. I guess the bead is sealed tight to the rim. Other than how it looks the ride is unaffected. But I'm still taking them off to see if I can get them repaired.
Yeah I'm sure you are right, but I got less than 24 hours of use out of the tire before this happened. And the tire never lost pressure. I guess the bead is sealed tight to the rim. Other than how it looks the ride is unaffected. But I'm still taking them off to see if I can get them repaired.
How deep was that pothole? To me it looks like the sidewall rubbed the side of the pothole, and the rim hit the edge when you fell in. Must have been a big pothole, and you managed to hit it in exactly the wrong way to cause such damage. Complained to the city yet?
The obvious downside of low profile tires and 32# of air.
Sidewall strength is an issue also. Some tires are just too flexible when it comes to the sidewall. With low profile tires I would lean towards run-flats or other technology/manufacturer, where the sidewalls are stiffer.
Sidewall strength is an issue also. Some tires are just too flexible when it comes to the sidewall. With low profile tires I would lean towards run-flats or other technology/manufacturer, where the sidewalls are stiffer.
Low profile tires are going to have less flexible sidewalls anyway, simply because the sidewalls are shorter and there is much less potential for the wall to flex. That's why they are harder to mount than taller profile tires.
How deep was that pothole? To me it looks like the sidewall rubbed the side of the pothole, and the rim hit the edge when you fell in. Must have been a big pothole, and you managed to hit it in exactly the wrong way to cause such damage. Complained to the city yet?
No the sidewall didn't rub, it's smooth as butter.
I was going no more than 20 mph but I hit the hole square on the edge apparently. I had hit that hole before in my truck and barely noticed it so I was unprepared for that level of damage. And yes I reported it but doesn't help me any, The city has 2 weeks to fix it and THEN if someone hits it they are liable. The first person gets nothing but bad luck. We don't have freezing temperatures, but apparently the 100F+ heat is just as bad on crumbling the pavement.
The more I look at it I think the tire itself caused that damage. I don't think the tire could have deformed enough for the pothole to make direct contact with the wheel. Not at 32 psi as they were freshly mounted. Maybe if they were low on pressure, say 20 psi.
[This message has been edited by jscott1 (edited 04-22-2014).]
Sidewall strength is an issue also. Some tires are just too flexible when it comes to the sidewall. With low profile tires I would lean towards run-flats or other technology/manufacturer, where the sidewalls are stiffer.
We finally agree on something Personally I like taller tires and higher air pressure. They ride and wear a lot better to me.
Originally posted by jscott1: The more I look at it I think the tire itself caused that damage. I don't think the tire could have deformed enough for the pothole to make direct contact with the wheel. Not at 32 psi as they were freshly mounted. Maybe if they were low on pressure, say 20 psi.
When a tire is flat & the bead is still in place, the sidewalls are folded double & squashed together. When the weight of a car hits the edge of a pothole, the tire absorbs the impact by flexing. A low profile tire has much less distance to flex before it is squeezed between the rim & the pothole edge. If the impact is sufficient to bend the rim, the rim will remain bent, while the tire will resume its previous shape. At the instant of the rim bending, there will be no air between the folded over sidewall surfaces. The rubber will absorb a lot of punishment and likely prevents the rim from cracking.
A Benz will probably be in the database.
