PSS is 255 on backorder - what is next size?
#51
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#53
The stock for our cars are 235/40/18 & 255/35/18 I believe.
To ask the really dumb question, why are the profile's 40&35 (F&R) respectively?
Does a 235(or 245)/35/18's not work with our car for some reason?
Thanks to anyone willing to explain this, I'm not amazingly versed in tire knowledge.
To ask the really dumb question, why are the profile's 40&35 (F&R) respectively?
Does a 235(or 245)/35/18's not work with our car for some reason?
Thanks to anyone willing to explain this, I'm not amazingly versed in tire knowledge.
#54
MBWorld Fanatic!
The stock for our cars are 235/40/18 & 255/35/18 I believe.
To ask the really dumb question, why are the profile's 40&35 (F&R) respectively?
Does a 235(or 245)/35/18's not work with our car for some reason?
Thanks to anyone willing to explain this, I'm not amazingly versed in tire knowledge.
To ask the really dumb question, why are the profile's 40&35 (F&R) respectively?
Does a 235(or 245)/35/18's not work with our car for some reason?
Thanks to anyone willing to explain this, I'm not amazingly versed in tire knowledge.
When you want to widen a tire, in general you lower the profile and go wider, which has the effect of limiting the change on the tire's circumference, which I don't think anyone would argue against being a good thing. (The debate is how bad changing it is.) The profile is a measure of "ovalness" of the tire's cross section. The lower the number, the "thinner" the donut is for the same width.
The downside is that lower profiles also are more responsive, which is why a larger wheel with a lower profile tire (a +1 that maintains overall circumference) will improve steering because it replaces mushy tire with stiff wheel. That's why you might go from 18" to 19" wheels and lower the profile of the tires.
So the higher profile up front is just a way of keeping the fronts and rears roughly the same diameter while making the rear wider.
Last edited by whoover; 04-30-2014 at 06:17 PM.
#55
The stock for our cars are 235/40/18 & 255/35/18 I believe.
To ask the really dumb question, why are the profile's 40&35 (F&R) respectively?
Does a 235(or 245)/35/18's not work with our car for some reason?
Thanks to anyone willing to explain this, I'm not amazingly versed in tire knowledge.
To ask the really dumb question, why are the profile's 40&35 (F&R) respectively?
Does a 235(or 245)/35/18's not work with our car for some reason?
Thanks to anyone willing to explain this, I'm not amazingly versed in tire knowledge.
As you said it's called the sidewall profile
Or aspect ratio
It = 2 x sidewall height / width x 100
Or tire diameter = rim + aspect ratio / 100 x 2 x tire width
Since the rears are wider they must have a lower aspect ratio to have the same diameter
255/35/18
Diameter = 18 + ( 2 * 35 /100 * 255 ) / 25.4
= 25 "
It's basically the ratio of the sidewall height to the tread width
Since the rears are wider to get the same diameter as the front the side wall must be shorter, ie, 35 vs 40
Last edited by Ingenieur; 04-30-2014 at 07:39 PM.
#57
MBWorld Fanatic!
This thread might inadvertently help to create cold fusion.
#58
Thanks guys. I appreciate the responses.
I asked because DiscountTire put on a set of 245/35/18's on my car, but one has developed a blister on the sidewall, and the other has picked up a nail, so now as I'm trying to get them repaired/replaced, their system is saying the load rating of these is too low, so they're forcing a 245/40/18.
Sounds like DT has gotten a system update, lawyer edition this year.
I just thought it strange as they put me in the 35's in the beginning...but uninformed types like me are probably benefiting.
Thanks again.
I asked because DiscountTire put on a set of 245/35/18's on my car, but one has developed a blister on the sidewall, and the other has picked up a nail, so now as I'm trying to get them repaired/replaced, their system is saying the load rating of these is too low, so they're forcing a 245/40/18.
Sounds like DT has gotten a system update, lawyer edition this year.
I just thought it strange as they put me in the 35's in the beginning...but uninformed types like me are probably benefiting.
Thanks again.