Any Tire Experts?

[r0nd3L]

I'm trying to figure some things out. Now I have 225/45R17 RT-615s on the front of my car. While it does corner pretty good, I really want to put some wider tires. The options are 235/40R17 and 245/45R17. The first one is quite a bit shorter than stock, but that doesn't really bother me. The latter one is exact size as stock (245/45).

Now, here is where I'm confused. On Falken's website both of those sizes show same section width of 9.6". How is that possible? And does that mean both sizes are same width?

[Slider]

The section width will change depending on the rim width the tire is mounted on. Tire Tech - Tire Specs Explained So if you look at the specs they had each tire mounted on a rim and measured the section width the 2 rim widths were different so you end up with those values. The section width measure includes the sidewall. The number you should be paying attention to is the thread width.

[black_box]

if 225/45 is stock, then the appropriate tire in a 245 is 245/40. Thats assuming the 245 will even fit on the wheel and clear the suspension. how wide is the wheel?

[cweber]

The width often has more to do with the brand of tire and the width of the rim.

For example, the Avon Tech RA r compounds I used were 205 50 15 but in reality they were as wide at 225s (don't ask me how they get away with this but it's true)

[r0nd3L]

Originally Posted by Slider

The section width will change depending on the rim width the tire is mounted on. Tire Tech - Tire Specs Explained So if you look at the specs they had each tire mounted on a rim and measured the section width the 2 rim widths were different so you end up with those values. The section width measure includes the sidewall. The number you should be paying attention to is the thread width.

Ahhh, I see why Falken lists same section width. The 245 was measured on 8" wheel while 235 was measured on 8.5" wheel. Thanks for explanation!

Originally Posted by black_box

if 225/45 is stock, then the appropriate tire in a 245 is 245/40. Thats assuming the 245 will even fit on the wheel and clear the suspension. how wide is the wheel?

The wheels is 8" wide. The stock size is 245/45 ALL AROUND. Currently I have 225/45 in the front and 245/45 in the rear.

Originally Posted by ceboyd

The width often has more to do with the brand of tire and the width of the rim.

For example, the Avon Tech RA r compounds I used were 205 50 15 but in reality they were as wide at 225s (don't ask me how they get away with this but it's true)

Yea, that makes sense as 245 RT-615s are much wider than stock 245 BFGs, for example.

So, if I upgrade I will definitely go to 245/45 and not waste time with 235/40 which I don't think would be marginal enough difference over 225/45.

I'm just wondering if it's worth it for me to upgrade at all or it 20mm wouldn't make much difference? It could also look funny as front tires would look little beefier since wheels is little narrower than rear (8" vs 8.5"). Not really big problem, though.

Here are two pics of 225 vs 245 (front vs rear):





Thanks for the help everybody!

[cweber]

keep in mind the steering in front might feel heavier with wider tires... and you might rub at full lock on steering...

[r0nd3L]

Originally Posted by ceboyd

keep in mind the steering in front might feel heavier with wider tires... and you might rub at full lock on steering...

Well, stock size is 245s, so I want to at least run that. Ideally, it would be awesome to run 265s all around, just need to find wheel with good offset.

[cweber]

ok. the other thing (which you might not care or mind) is that the fatter the tire, the more rolling resistance, the worse the gas MPG.

In summer, I run 225 40 18 on my R32 VW but in Winter I run 205 50 17s (snow tires)... and even though normally mpg is worse in winter and snow tires have more resistance due to tread design, I get 2mpg better overall in winter vs. summer (vs. 5mpg worse in winter on 225 40 18 snow tires)

[r0nd3L]

Originally Posted by ceboyd

ok. the other thing (which you might not care or mind) is that the fatter the tire, the more rolling resistance, the worse the gas MPG.

In summer, I run 225 40 18 on my R32 VW but in Winter I run 205 50 17s (snow tires)... and even though normally mpg is worse in winter and snow tires have more resistance due to tread design, I get 2mpg better overall in winter vs. summer (vs. 5mpg worse in winter on 225 40 18 snow tires)

Yea, I'm willing to sacrifice MPG for more grip. I decided to keep 225s for this year, though. I'll probably end up selling the wheels in winter and getting 17x8.5" or 17x9" for next year and run 255/40 all around. Should be good improvement from 225