Tire Safety
Tire Safety
(OP)
After reading the contents of thread68-161928: Correct Tire Pressure, I checked out the specs of a wheel/tire swap and am slightly concerned about the safety of the tire choice of a fellow forum member for street and occasional track day use.
The spec OEM front tire:
275/40ZR 17 - 98Y - Max Load 1653@44psi
_________________________________________
The tire that is on it now:
275/35ZR 18 - 95Y - Max Load 1521@51psi
_________________________________________
I called BFGoodrich and of course they will definitely
not sanction this particular swap, but OTOH as previously stated,the max load safety margin is for worst case scenarios/legal protection.
Is this a legitimate concern on my part or should I just mind my own business?
Thanks!
The spec OEM front tire:
275/40ZR 17 - 98Y - Max Load 1653@44psi
_________________________________________
The tire that is on it now:
275/35ZR 18 - 95Y - Max Load 1521@51psi
_________________________________________
I called BFGoodrich and of course they will definitely
not sanction this particular swap, but OTOH as previously stated,the max load safety margin is for worst case scenarios/legal protection.
Is this a legitimate concern on my part or should I just mind my own business?
Thanks!





RE: Tire Safety
Perhaps this individual is partially compensating with a little higher inflation pressure.
Norm
RE: Tire Safety
The OEM spec that I quoted is for a 2004 Mustang SVT Cobra.
Thanks!
RE: Tire Safety
RE: Tire Safety
I would imagine that the increased front end weight of a SVT Cobra, as opposed to a GT.....DOHC heads, supercharger, intercoolers, pumps, hose assemblies etc. warrants the increased load capacity of the 275/40ZR 18.
So bottom line, I assume that you agree with his choice of front tires?
Thanks!
RE: Tire Safety
Z rating means it has a speed rating of 149 mph plus.
here's a link that shows (1) the pressure increase above OEM spec necessary for speeds over 118 mph for Z-rated tires, and (2) the effect on load capacity if the pressure increase for speed would exceed the max pressure on the sidewall.
I don't see how a Mustang with driver could weigh much over 4200 lbs.
http://www
Or have much less than 55% or so on the front wheels. http:/
>>Maybe<< it can go faster than 149 mph. I'd want to see it on a GPS rather than any factory speedo.
So, driving straight ahead the weight the pair of front tires will carry continuously is 2300 lbs or so, and each tire will carry less than 1200 lbs.
Just looking at the max load you provided it looks like either tire could easily handle the Mustang's weight at whatever the max speed rating is, but might need max pressure to go that fast for a long time.
I'm guessing it would take a banked superspeedway to allow 149 mph driving AND enough weight tranfer to require considering non-equal front tire loads of any duration.
RE: Tire Safety
Thanks!
John
RE: Tire Safety
I've heard that using tires that are larger capacity than needed helps handling. Specifically, that the carpet plots are much more linear in the lower load areas - and that translates into more predictable handling.
RE: Tire Safety
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Tire Safety
Hmmm.......OTOH, if there is room/no rules for the largest load capacity tire possible......could there be a case of diminishing returns if too large a tire were fitted as it relates to turning corners?
Thanks!
John
RE: Tire Safety
In the dry I don't think you'd really see an upper limit, other than by practical considerations..
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Tire Safety
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Tire Safety
Decisions, decisions......thank you all very much!
John