ughh why do people care about just max numbers when it means absolutely nothing.... just ask your tuner to bump the numbers for you if you care that much at reaching some "special number." and then enjoy knowing that reading is worthless

 

I would have it tuned on what ever size tire you use daily which are probably the 19"s. Isn't tuning about setting up the profile so your torque comes in at the lowest rpm where it's more useful? Tune with what you drive on....
Gary

 

I use both equally. The 17s for summer, I do a lot of track and drive aggressively so thos r compounds only last me about roughly 7k miles.

I like to run the 19's for winter since I drive very cautious is the colder weather and the 19s are damn sexy.

It is a lot cheaper to pay 145 each for those r compounds on 17 inch than it is on 19, I was looking at almost twice the price, I can last atleast two winter/falls on the 19s, where as thee 17's dont even make it past 3 months.

So I wouldn't say I use either more than each other.

Yeah sure people say numbers are just numbers, but when you are boosted or have a built engine you do care, especially since a lot of money was put in to it.

 

I am inclined to agree with that sentiment

While i can understand where your coming from, however in my experience you could probably run your car on five different dynos and get five different readings, the only real way to know if you money was well spent is an engine dyno they don't differ or lie, and if you have spent a lot of money on an engine build, then i am surprised that the tuner didn't set it up this way.

Also if you do lots of track work, then you should know that torque is king, and where its produced in the RPM/load range is all important,and not total BHP
which is just known as "pub BHP" here in the UK, or bragging rights

 

Speaking strictly from a weight perspective...

245/45/17 Star Spec's weigh in at 28lbs.
245/40/19 452's weigh in at 25lbs.

17s, 24+28 = 52lbs.
19s, 21+25 = 46lbs.

 

All the theories are good and sound but the reality is the dyno has a margin of error and .5-2 BHP is well within that margin of error if that's all the extra you need. Get the best gas you can find in there and that will make more difference I think.

 

Yeah you guys are ALL right to some point,

I pretty much am worrying about the driablity the most,
I am going to see if If I cans squeeze any extra power out of 100 octane vs the 91 we get here, since there are a few gas stations that sell it. I also just dropped down to a cooler set of plugs, so I should at least be able to get one more degree of timing out of that.

I want the good Hp numbers for bragging rights like you said,
A lot of dynos vary, like churchs so If I used his im sure id make over 350 on it but then again everyone would know that its inflated so I wouldnt have any bragging rights, LOL

I should be going back in to the dyno in the next two weeks so well see how I do.

I kinda figured my 17' set up weighed more than the 19s but the butt dyno feels a lot better. LOL so just trying to see.

 

Going back to tyre sizes, your bound to notice a difference with the
245x45x17 as opposed to the 245x40x19 as the rolling radius of the
17" wheels/tyres is 204.93 cm, as opposed to 213.19 cm for the 19"
so 2.53cm difference in diameter.
so the overall gearing is lower for the 17", so you will have slightly better acceleration.