QuestionQUESTION: Hi Barry....I'm in a real jam and hope you can help me out. Excuse the length of this email, but I've done a lot of research and wanted to let you know what I've learned.
I have a 1990 Bentley Turbo R which came with Avon "Turbospeed" Tires - 255 65 R 15. I learned by research that these are "V" rated tires with a load factor of 106. Unfortunately, they are no longer made which is my problem.
The only tire available in this size is the Goodyear Eagle LS which is an "S" rated tire with a 105 load rating. Thus, I know it will fit and run. But, I also know the performance will be less than with a "V" rated tire.
Obviously, I don't drive this car much and I rarely go over 60 mph with it. Nor does it lend itself to aggressive driving. Net, I drive it pretty cautiously.
I checked the Bentley owners club and most people seem to be either resizing the wheels (later Bentley's came with 17" wheels, but this is a $2,000 expense for new rims and adapters because they are not designed for my car), or using "V" rated tires that are close in size, but not exact, e.g. 255 70 and 275 60.
Any advice you might have on what to do what be greatly appreciated. Thanks...Rich
ANSWER: Rich,
This is quite a conundrum.
First we know the original tire size will fit in the fenderwells. The Load Index is not a concern (long story), and while I ordinarily recommend using S rated tires, there aren't a lot of options.
A P255/70R15 or a 275/60R15 might run into rubbing problems. If no one has tried one of those, then it might be worth the effort. While I don't have the dimensions of the fenderwells, a 275/60R15 is only 3/4" wider, so it is likely that it might fit. This would make quite a visual statement on this car.
---------- FOLLOW-UP ----------
QUESTION: OK, Barry. I've now got more information and two alternatives:
1) Use the Goodyear EagleLS "S" rated tire with a 105 load factor; or
2) Use a 235 70 V rated Goodyear Eagle RS-A with a load factor of 102. This is the tire size that was used on the nearly identical 1990 Rolls Royce.
I think I'm headed to the narrower V rated tire because the V rated sidewalls could have a larger impact on handling than narrower tires.
With that said, I'm a bit worried about the difference in load factor - the 102 on the V rated tire versus 106 on the original equipment tire. Given your comments that I shouldn't worry too much about the load factor, does this sound like the right decision to you?
Thanks for your help...Rich
AnswerRich,
Just so this is clear, my comment about not worrying about the load index was in reference to the 255/65R15 and the difference between a 106 and a 105 Load Index. Again it is a long story, but here it is:
http://www.geocities.com/barrystiretech/loadtables.html
But it is a concern when you change tire size.
According to Tire Guides, a 1990 Bentley Turbo R originally came with 255/65R15 106V inflated to 30 psi front and 37 psi rear. Check your placard to make sure this is correct as what I am about to write depends on this information.
If you were to use a 235/70R15 102V, then if you inflated the fronts to 33 psi, you'd get the same load carrying capacity. But the rears is a different story - and of course, it is complicated.
37 psi is a bit more than the pressure where the maximum load carrying capacity occurs - and that leads me to believe that this pressure is more about handling than load. With that in mind, I can see where using this size at 40 psi (to maintain the handling split) might be OK.
But it would be good to check with folks who have access to the Gross Axle Weight Ratings (GAWR) of the vehicle to confirm my speculation.
