SleepyHead, Bobzilla, and John Welsh do OneLap2018

Tire engineers build in a factor of safety, I'm sure of it. These are cars not airplanes, it's probably something like 2. You'll be fine. 

In reply to mazdeuce - Seth :

says the guy running 275's

I have never looked at the max load of a tire before so that was a bit of interesting schooling for me.

So if I'm reading your math correctly you take weight with driver (3300 in our case) multiply by the percent on the front axle (53%) and then where does the 70% come into play? I assumed a typo on yours as you had .6x.6 but where does that 70% number come from?

lets say in our case we saw spikes of 2G with sustained cornering around 1.3g does that mean I would take that 3300x.53 and then times 1.3 to get sustained load on the tire or times 2 to get max cornering on the tire?

Also interesting to note that the 275 continentals only have 1541lbs per tire so not a massive increase in load handling but then I'm not still fully up to speed on the math here so maybe that 15% additional load capacity is bigger than I realize

Recall that not all the load is going to be carried on the outside tire... by using 0.7... I guess I'm using a 1g load and a 70/30  split across the outside vs inside tires.  i don't know if that guesstimate is correct.. but it seems reasonable.

So, in your case...

3300*.53*1.3*.7 = 1591

It's possible/probable that wheel camber has an impact on this too.

In some ways... this is just using the tire load rating as a tool to compare tire stiffness.

Iirc, this came up recently in a "make fwd handle thread"... which is where I recall the use "lat g as a normal load component"... but there is a very real chance I'm going about this wrong

mazdeuce - Seth said:

Tire engineers build in a factor of safety, I'm sure of it. These are cars not airplanes, it's probably something like 2. You'll be fine. 

As a former tire engineer, I know for a fact that a factor of safety of 3 was used at my company.

If you move forward with an "under-rated" tire my biggest suggestion is keep an eye on tire temperature. The thing that ultimately causes tires to fail is HEAT. Unfortunately, I don't have a concrete number for what is too hot, but keep an eye on it. Especially on long distance, high speed cruising and after hot lapping.

ShawneeCreek said:

mazdeuce - Seth said:

Tire engineers build in a factor of safety, I'm sure of it. These are cars not airplanes, it's probably something like 2. You'll be fine. 

As a former tire engineer, I know for a fact that a factor of safety of 3 was used at my company.

If you move forward with an "under-rated" tire my biggest suggestion is keep an eye on tire temperature. The thing that ultimately causes tires to fail is HEAT. Unfortunately, I don't have a concrete number for what is too hot, but keep an eye on it. Especially on long distance, high speed cruising and after hot lapping.

good to know... should I go back and delete my maths?

re:heat on cruise after lapping...
do you have an "asphalt number"... pretty sure we'll be on that more than concrete 
j/k.  I'll try to keep an eye on it, although the tires will get about 30mins of cooling after lapping between packing/gassing up.  Probably not enough to fully cool... but perhaps enough to put them closer to the "happy zone"?

do you have any tire temperature gauge recommendations?

I can bring my tire pyrometer if you really want to be "that guy" and collect tire temperature data along the way. 

can't be any worse than some of the other pictures of me that Steve's gotten over the years 

is tinfoil or widebrimmed the proper hat to effect the right "pose" while taking temps?  I should probably dig up my kneeboard from my lackluster pilot days to really pull it off, right?

I'd be more concerned about static or steady state loading. That's where capacities are typically defined. The transients and short excursions from cornering load transfer would fall into the margin.

alright, fine...

since I can't use maths, I'll go with emotion:
I want an excuse to run staggered 245's and 225's.. and 18x8's fill up the front fenders nicely

plus this way I have an extra optima wheel to slap a matching spare

of course, the real trick is going to be: how do I pull this off visually

edit: if I seem 'tweaked a bit'... sorry, sleepykid#2 is going into hour 2 of a nap on my shoulder... which is beginning to get uncomfortable

ooo, I like the staggered tire idea, should make for far more entertaining handling on track! And i'm always all for wider tires too :)

My favorite thing about staggered tire sizes is that it's pretty easy to progress from 225&245 to 245&265 etc.

If you're going to run non-matching wheels, then I rescind my previous recommendation about colored wheels. Paint them black. 

mazdeuce - Seth said:

I can bring my tire pyrometer if you really want to be "that guy" and collect tire temperature data along the way. 

I'm collecting oil data.... why not? 

mazdeuce - Seth said:

If you're going to run non-matching wheels, then I rescind my previous recommendation about colored wheels. Paint them black. 

I'm going to agree with this. Is there a possibility of rotating the larger tires to the rear to preserve them on the longer driving distances? I know that they won't generate nearly as much heat and where on the rear even loaded. Just a mental thought. 

Bob the REAL oil guy. said:

I'm going to agree with this. Is there a possibility of rotating the larger tires to the rear to preserve them on the longer driving distances? I know that they won't generate nearly as much heat and where on the rear even loaded. Just a mental thought. 

we can do that... although, we'll have to think through how we do that, so we don't lose too much time while packing.  and, obviously, you'll be handling hot wheels/tires/lugs, etc.

I got an impact..... ;)

Mechanic brand gloves offer plenty of heat protection for lugnuts in my experience.

There will be 3 folks on the team right?

Person 1: begins trunk packing

Person 2: begins jacking car up and positioning jack stands

Person 3: gets out of race suit, into street clothes and prepares to help with wheels.

if you have 2 impacts I would think people 2-3 would be able to swap wheels nearly as quickly as person 1 could pack the trunk.

In reply to klodkrawler05 :

You can position the jack about 8-10" behind the actual jacking point for teh front and have the entire side of the car lifted. 5 minutes to push front to back, and another couple to run the torque wrench over them the double check. 15 minutes including moving the jack.... as long as there aren't spacers invovled.

sleepyhead said:

... and for whatever reason that had me remember car-part.  Hop on there, and find that a recycler an hour away has several 18x8's in-hand... $88/wheel.  So, I loaded up the sleepykids... one of which needed a nap anyways, and now we have 18x8's!

initial pickup pic:

I forgot to tell the funny part of this story.  I had sleepykid#1 sit in the back of the van while I loaded the wheels in... to keep an eye on the wheel, and to keep them occupied.  Well, just inside the window for the sales area of the recyclers were two LS motors sitting on stands.  I finish putting the wheels in, and sleepykid#1 says:
"Daddy, you need a super race engine in your new race car"
"Huh, what?"
He pointed to the engines, and repeated that I needed one of them in my race car to go faster.

My kid inadvertently wants me to LS-swap the Sonata.

So, I laughed and told him that might have to wait for the next race-car.

Not the morning I was expecting...

The sonata took some minor battle scrapes... but will just add to its "character"

Wow, that d-pillar hit on the Mini is a pretty big hit.  I see tailgate damage.  Is there any rear qtr panel damage?  Other than glass, is there metal damage to the roof?  

there's a little divot in the roof

c-pillar and the tailgate are the main damage... but it's possible that that c-pillar damage is terminal?  It's pushed over enough that I'm not risking trying to open the tailgate.  Insurance should hopefully pick it up this morning?  although, they might be busy with other pick-ups... there's at least four trees down on our street... pretty sure the whole area's been hit pretty good.

now to wait for the opportunist tree doctors to roll through the neighborhood offering their services

here's a better view of the offending tree...

edit:I'm sorry, I forgot to include a banana for scale... hopefully the mailbox will suffice?