Best tire size for 9x16s?

[Tachin]

What is the best tire size for the 9x16s? I have 245/45 on my 8x16 which look too small on the 9s, but perfect on the 8s. Is there another size that fits the 9s better?

Someone told me that the extra inch on the 9s doesn't actually get more traction but rather putting the 245/45 on the wider 9 reduces the air mass inside the tire, which increases the temperature resulting in more grip.

Thoughts? Thank you.

[Bill Verburg]

Originally Posted by Tachin

What is the best tire size for the 9x16s? I have 245/45 on my 8x16 which look too small on the 9s, but perfect on the 8s. Is there another size that fits the 9s better?

Someone told me that the extra inch on the 9s doesn't actually get more traction but rather putting the 245/45 on the wider 9 reduces the air mass inside the tire, which increases the temperature resulting in more grip.

Thoughts? Thank you.

2 things
you need better informed sources
your eye needs further education

If grip s the goal then you need to use the widest wheel for which a tire is spec'd, should you not believe in the spec, use the widest wheel that you you can fit, keeping in mind that at some point the tire can be fitted but it will be dangerous
spec wheels for a 245/45 x16 is 7.5 to 9.0, 7.5 gives the softest sidewall and most comfortable ride, 9 gives the stiffest sidewall which then supports the tread best, which then gives the best grip.

yes, grip depends on tires temps but that depends on the tread compound, for most track tires that run far hotter than most street tires relatively low pressures ~34psi +/- hot will usually provide the best grip.

race engineers will generally stretch the tire a bit beyond spec, but the tires are only used on smooth surfaces and w/ a very short life expectancy

Thes are a bit stretched, probably .5" over



This is dangerous


on left is a 275/40 on a 9.5, this tire would work much better on an 11, on the right is a 245/45 x16 on a 9, this is perfect for that tire


These are all maxed to spec

[Tachin]

Thanks for the schooling. I'm just a street guy, never on the track. So you are saying 245/45 is the best tire size for the fuchs 9s on the street and should result in more grip than the same tire on the 8s?

My goal is to have max grip and fill out the wheel well. When I've seen 245/45s on the is they looked a little streched as compared to the same on the 8s.

Trying to decide if I should get rid of my 9s and understand what the situation would offer if I keep them.

Thanks.

[Bill Verburg]

Originally Posted by Tachin

Thanks for the schooling. I'm just a street guy, never on the track. So you are saying 245/45 is the best tire size for the fuchs 9s on the street and should result in more grip than the same tire on the 8s?

My goal is to have max grip and fill out the wheel well. When I've seen 245/45s on the is they looked a little streched as compared to the same on the 8s.

Trying to decide if I should get rid of my 9s and understand what the situation would offer if I keep them.

Thanks.

245/45 is the best tire size for the fuchs 9s on the street and should result in more grip than the same tire on the 8s?

Yes, similarly if you have 8s 225/50 x16 is optimum the tire to use for grip.
245/45 on 9 gives more grip than 225/50 on 8, for 2 reasons
1) tread width/shape, the tread area will be the same all other things being equal but the shape changes. A wider oval shape as provided by the 245/45 runs at a lower slip angle than a longer oval shape. The lower the slp angle, all other things being equal, the higher the grip.
2) the sidewall height/ stiffness. The shorter & stiffer the sidewall the more more grip can be generated, for reasons similar to item 1

Hee's a nicely setup car 225/50 & 245/45 not sure what the front wheels are but the rears are 9.

Fill up the wheels wells will determined by ride height and wheel spec as well as the tire


There are many tradeoffs in these choices

one given for max grip is to use 8 ET25-30 front and 9 ET10 to 15 or 9.5 ET19 rear
another is to lower the car and set the suspension up for grip

all that is predicated on the tires selected

for maximum grip + maximum efficiency(minimal torque loss from the selected tires) use the shortest tires

in 15 use 225/45 & 245/40 tires, usually R rated but there are some notable exceptions. OD is ~22.5"

in 16 use 8 ET25-30 & 9 ET15 w/ 225/50 & 245/40 tires, OD is ~24.7".
7ET23.3 & 8ET10.6 w/ 205/55 & 225/50 gives up a little grip but not much and is far more generally available. RE71 is a standout for gripin these sizes and will likely perform as well as many R rated 245/45 x16

in 17 use 8 ET25-30 & 9.5 ET19 w/ 235/40 & 255/40 tires OD is ~24.9" or 215/50 & 245/40 for @ ~24.7" OD, the later give up a little grip for better efficiency

[darrin]

tachin -- keep in mind that there are VERY few options in the 245/45-16 tire size, and (nearly?) all of them are R-compound track-centric tires. Not sure if your 911 will see the rain or very many miles each year, but R-compound tires aren't ideal for either of these metrics.