Going 19's...Tire Calculator

[stef2.7t]

1010tires says to stay within 3%

What about 3.03% ??

225/45/17 to 245/35/19

[Deep6ed]

Just go 240/35/19. most people run 235/35/19 though.

[lodit]

It's fine. Your speedo will be off a little, but so long as you keep that in mind when driving near posted limits you shouldn't have any real issues.

I ran 245/35/19 all around on my 4.2Q without issues for over a year.

[ccomengee86]

Just go 240/35/19. most people run 235/35/19 though.

I don't think anyone makes 240's.

[A4edwin]

you'll be fine! you might rub though.

[monkeytronic]

It's probably worth noting that not all tires in a given size can safely carry the same load, especially so with relatively narrow, low-profile tires in the 19" size where tires with a standard load index won't even come close to meeting the manufacturer's recommended minimum load index, which AFAIK is like 94 (for a C5 4.2 at least) and that includes dynamic loading as the car is driven enthusiastically esp. during evasive maneuvers--not just the very rare times when the car's loaded up chock full o' sh!t right up to its GVWR.

Definitely consider eXtra Load (XL) rated tires with reinforced sidewalls which may be available in whatever tire size one is considering. Also note that besides speedometer error, the larger the new tire size's overall diameter is, the more sluggish the car will seem when accelerating as larger tires will effectively change the car's gear ratio, making it taller (numerically lower) than it is with the correct overall tire diameter.

[deucescorner]

I would run 235/35 tires. 3.03% is fine.

Oh god I can wait until we finished developing our new Offset/Tire size calculator for iPhone/iTouch

[vinrock]

Anyone running a 30mm profile? I was sizing up a set of 19's to put on my 4.2 and it looks like 255/30 keeps the OD pretty much the exact same as stock. I'm just worried about load rating and how harsh they're gona feel with the rubberbands.

[Alipor]

Anyone running a 30mm profile? I was sizing up a set of 19's to put on my 4.2 and it looks like 255/30 keeps the OD pretty much the exact same as stock. I'm just worried about load rating and how harsh they're gona feel with the rubberbands.

The difference between 35 and 30 isn't a huge difference in ride quality. After a day or two you won't remember the difference.

[redneck truck]

Profile is not measured in mm, but in % of width.

As for the max load rating, I never considered it. My car is 3940 57/43 full of fuel with no driver, and the tires I'm running are 245 35 zr19s with a 1433 lb max load rating per tire. How close am I to the limit? I'm running 36psi in each tire, though I'm now thinking of upping the front tire pressure.

[julex]

Anyone running a 30mm profile? I was sizing up a set of 19's to put on my 4.2 and it looks like 255/30 keeps the OD pretty much the exact same as stock. I'm just worried about load rating and how harsh they're gona feel with the rubberbands.

I am not sure what you mean by "30mm profile". the "30" number in 255/30 doesn't mean there is 30mm of meat on sidewalls, it means that the sidewall is 30% of tire width, so 255*0.30 = 76.5mm.

On my allroad I run 255/40/19 (because allroad has larger wheels than s4/a6) which gives me 102mm of meat... and I think that is the sane minimum to have if you intend to keep your rims for longer than first encounter with pot hole... but I see that you have no practical choice there seeing that you'd have to downsize the rim.

There are also choices to be made when it comes to tire. No tire is equal and the ones for higher load rating are usually stiffer which is perfect for low sidewalls.

[vinrock]

Oh come on you knew exactly what I meant.

[monkeytronic]

As for the max load rating, I never considered it. My car is 3940 57/43 full of fuel with no driver, and the tires I'm running are 245 35 zr19s with a 1433 lb max load rating per tire. How close am I to the limit? I'm running 36psi in each tire, though I'm now thinking of upping the front tire pressure.

1433 lbs/tire = load index of 93 which most likely means you're running XL rated tires. This is more or less adequate considering the rather limited selection of tires in this 245/35-19 size compared to the 4.2's OE 255/40-17 tire size with its minimum load index of 94 (1477 lbs/tire).

Compare with standard load rated 245/35-19 tires which sport a rather inadequate load index of just 89 (1279 lbs/tire) that aren't recommended, at least in a OE sense, for the C5's heavy ass-edness.

Also, air pressure directly affects the tire's max load capacity and the stuff of legend, e.g. the Firestone Ford Explorer fiasco, is made possible by overloading tires operating below their optimal pressure.

[redneck truck]

Good deal. Is there a formula for calculating max load based on load index? Also, what pressure should I be running given this is the case? I've been running 36psi. Is that too low?

[vinrock]

Good deal. Is there a formula for calculating max load based on load index? Also, what pressure should I be running given this is the case? I've been running 36psi. Is that too low?

Load index chart right here holmes

I've been running 36psi cold as well expecting it to be around 38-40 when they heat up, however I have not verified the exact pressure.

[scot_w]

And a handy dandy Java based tire sized calculator HERE, just in case you really want to know.

[julex]

This is helpful too, coupel of tools. Namely offset and tire size stuff:

http://www.1010tires.com/tech.asp

I do like the visualization feature of your calculator :)