Well - they will throw out the speedo , have more sidewall flex (compromise handling a little ) , and look crap because they are taller on the rim .

Sounds 'wrong' to me

 

I also call BS on the speedo theory, I have had various rim and tire sizes and my speedo has always been off 2-3MPH regardless of what sizes I have run when compared to my GPS, even now on staggered tire sizes and 19's.

 

A 245/45 should actually have a more accurate speedo, incidentally, considering that the stock tire size leads to an inaccurate one.

My 235/55/17 winter tires put my speedo exactly accurate with my gps.

But, still subjective, based on what you are doing with the car

45s would drop the revs and slow down the odometer, both slightly, would ride better on rough roads, and could be more comfortable for highway driving.

I tested 245/35s at one point on my 8, though I found it wasn't worth it. I'd rather 45s than 35s.

 

The specs for a size of tire, vary from one manufacturer to another. Then there are variations in the manufacturing process.

All you can do is make an educated guess.

 

I'll see if i cant do a test fit, my friend owns a wheel shop. will post pics for other silly people to judge from for future reference if i do

 

There are pics here of 245/45-18's, they looked like *** IMO. I don't see the point in running that size at all.

 

If he's going for a $35/tire price difference, looks aren't likely his biggest concern.

 

More like $150 with tax for all 4. But I decided to do the other rout anyway

 

I just bought my 245/45/r18 Falkens. Ill post pics before and after my 25mm wheel spacers. I also ordered my Tein S Specs.. it's looking like Ill only be lowering the front.

 

Lowered + taller tires = don't cry when you have problems.

Scott your speedo has never been wrong because you have had nearly stock outer diameter every time. 245/40/18 and 255/35/19? That's pretty damn close to 225/45/18 (I haven't run the numbers but I would be very surprised). Only the rear tire diameter matters for the speedometer

 

Im not lowering the rear. Still have an inch or so clearance back there, but snug enough.
The front I can still fit my hand in so I dont think a 1/2 lowering spring will make much of a difference up front.
Thanks for the input tho. Im just posting so others can see what/how 45 vs. 40 series tires will fit. Like the thread title asks.

 

I'm telling you to be prepared. The front is where it matters the most.

Wtf is a 1/2 lowering spring? I'm really interested to see how this looks. I expect it to be bad

 

The Tein spring (says it lowers .5"). Also, after adding the 1" spacers the front wheel sticks out further than the back about .25"
... Ill be swapping the 1" spacers up front for .5" spacers. Im having slight rub at full lock rolling in and out of the driveway.

 

s-techs do not lower the car a half inch. It's 1.4" front and 0.8" in the rear if my memory is correct.

 

I have no real life experience with them. Not many Rx8 owners here. Im just using the info I read on eBay. I'd actually prefer the 1.25" drop more.

 

don't buy those off ebay. fakes everywhere. TEIN S.Tech Spring Kit: RX8 for RX8

Sounds like you should read about them a little bit more

 

I matched the part numbers.. how do you kno if theyre fakes? Either way, I'll be swapping the spacers due to the larger tire size causing them to stick out a touch further than the rears.