Tire size guru's opinion needed

[TWOpointFORliter]

Ok I have been reading on tire size and fitment for the better part of 3 days now. I still can't find the answers I am looking for. I recently picked up a set of evo9 enkies and need to put some tires on them. I am pretty set on Dunlop star specs since I love the set I have now. I would also like to stick with a 45 series tire. My car is lowered but I can and will raise it as needed (sits too low right now anyways) and I have front and rear chamber kits. I have no problems rolling my fenders and have access to and Eastwood fender roller to do it right. I know a 235/45-17 will fit also a 245/40-17 but I would like to fit a 245/45-17. I have seen that it is possible depending on the tire so I have some specs on the tires I want to run for you. Measuring was done on a 8" rim. The sectional width is 9.7" and the overall diameter is 25.7 the tread width is n/a. Tire guru's let me know what you think. Also if anyone has experience with this EXACT set up please chime in.

 

[daren_p]

You are aware that sidewall size is a percentage of width, correct? So a "45" sidewall is not the same height for every tire width, the wider the tire, the taller the sidewall.

Its been so long since I've had stock rims/rubber, can't recall the stock size, but think the overall diameter is 24.6. So ideal, would be to get close to this.

235/45/17 would be ~25.4
245/40/17 would be ~24.7
245/45/17 would be ~25.7

If you want 245 wide, the 40 series would probably be ideal.

 

[TWOpointFORliter]

You are aware that sidewall size is a percentage of width, correct? So a "45" sidewall is not the same height for every tire width, the wider the tire, the taller the sidewall.


If you want 245 wide, the 40 series would probably be ideal.

Nope I was unaware if that but thanks for the help. In that case I will just stick with the 245/40 like many others have run with success.

 

[daren_p]

Sounds good. For future reference, like I said, the sidewall number is just a percentage of the width (not a fixed measurment).

So width is typically measure in mm now (some slicks & bias ply tires will still be measured in inches), just take the percentage of the specific sidewall number to get the actual sidewall height. So on your posted choices the sidewalls would be:

105.75mm on the 235/45
98mm on the 245/40
110.25mm on the 245/45

If you take this example further, look at a 50 series sidewall on a 205 tire compared to a 285. The 205 will look fairly low profile @ 102.5mm, while the 285 will have a 142.5mm tall sidewall.

Thats why when the rwd cars have massive rear rubber, like 345, their sidewalls may be a 25 or 30 series, but still have a fairly normal looking sidewall. If you ran a 25 or 30 series 205 wide tires, it would look like a rubber band in comparison.

 

[TWOpointFORliter]

Thanks again for the education. No one has ever explained it to me like that. I love learning new things about my car.