What's the sidewall difference?
Originally Posted by wasiu0607
Also, is there any way to fix this, but still keep the 35 ratio? Odometer is what concerns me more (don't want to add anymore mileage to my car than it already has).
Originally Posted by wasiu0607
Very helpful site, thanks Dave. So by switching from 225/45 to 245/35, odometer and speedometer will be 4.93% higher. And for the rear, switching from 245/45 to 275/35 will increase reading by 4.31%. Does the car take the average of these two when displaying the odometer and speedometer? Also, is there any way to fix this, but still keep the 35 ratio? Odometer is what concerns me more (don't want to add anymore mileage to my car than it already has).
Whatever size you wind up going with just make sure the rear tires are 0.7-1" taller then the fronts. This is to aviod unusual VDC/TCS behavior.
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One problem i encountered while trying to calculate the sidewall height.
When I do the calculation for ex 245/40/18, I do 245 x 0.4 which results in 98 mm. But this can also apply for 245/40/19 as well... How do I calculate one just for 18", or am i doing this calculation wrong?
When I do the calculation for ex 245/40/18, I do 245 x 0.4 which results in 98 mm. But this can also apply for 245/40/19 as well... How do I calculate one just for 18", or am i doing this calculation wrong?
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Obviously you want the look that you get with 35 a profile. So, do what terrasmak suggests:
Get something like this:
Front: 19x8.5” wheels with an 18 offset and 245/35-19” tires
Rear: 19x9.5” wheels with 22 offset and 275/35-19” tires
Make a decision and end this… Please.
(friendly kidding here)
--Spike
Originally Posted by terrasmak
Yes , its simple. Buy 19's.
Front: 19x8.5” wheels with an 18 offset and 245/35-19” tires
Rear: 19x9.5” wheels with 22 offset and 275/35-19” tires
Make a decision and end this… Please.
(friendly kidding here)--Spike
Originally Posted by wasiu0607
One problem i encountered while trying to calculate the sidewall height.
When I do the calculation for ex 245/40/18, I do 245 x 0.4 which results in 98 mm. But this can also apply for 245/40/19 as well... How do I calculate one just for 18", or am i doing this calculation wrong?
When I do the calculation for ex 245/40/18, I do 245 x 0.4 which results in 98 mm. But this can also apply for 245/40/19 as well... How do I calculate one just for 18", or am i doing this calculation wrong?
My statement was for overall tire height, not sidewall height. If a tire is 26" tall in the front, the rear must be between 26.7-27" tall.
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Thx Eddie and everyone.
One more off topic question. Is it the same width if I get 10mm spacers and 265/40R as opposed to just 275/40R? Does the difference in tire width cancel out the need for spacer, or are spacers a totally diff. ball game?
One more off topic question. Is it the same width if I get 10mm spacers and 265/40R as opposed to just 275/40R? Does the difference in tire width cancel out the need for spacer, or are spacers a totally diff. ball game?
Originally Posted by wasiu0607
One problem i encountered while trying to calculate the sidewall height.
When I do the calculation for ex 245/40/18, I do 245 x 0.4 which results in 98 mm. But this can also apply for 245/40/19 as well... How do I calculate one just for 18", or am i doing this calculation wrong?
When I do the calculation for ex 245/40/18, I do 245 x 0.4 which results in 98 mm. But this can also apply for 245/40/19 as well... How do I calculate one just for 18", or am i doing this calculation wrong?
Originally Posted by wasiu0607
Thx Eddie and everyone.
One more off topic question. Is it the same width if I get 10mm spacers and 265/40R as opposed to just 275/40R? Does the difference in tire width cancel out the need for spacer, or are spacers a totally diff. ball game?
One more off topic question. Is it the same width if I get 10mm spacers and 265/40R as opposed to just 275/40R? Does the difference in tire width cancel out the need for spacer, or are spacers a totally diff. ball game?
A spacer will move the position of the wheel.
Originally Posted by wasiu0607
Thx Eddie and everyone.
One more off topic question. Is it the same width if I get 10mm spacers and 265/40R as opposed to just 275/40R? Does the difference in tire width cancel out the need for spacer, or are spacers a totally diff. ball game?
One more off topic question. Is it the same width if I get 10mm spacers and 265/40R as opposed to just 275/40R? Does the difference in tire width cancel out the need for spacer, or are spacers a totally diff. ball game?
Since the spacer has no effect on sidewall height or overall tire height it doesnt change a thing other then wheel offset.
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One last question lol.
If I get 235/40 in front, which is 1% increase odometer & speedometer reading, and rear 265/40, which is 1.27% increase, does the car take the average of these two?
If I get 235/40 in front, which is 1% increase odometer & speedometer reading, and rear 265/40, which is 1.27% increase, does the car take the average of these two?
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^^ Not sure what you mean when you say "average of these two."
But, the sizes you mention on 18" wheels are within the Z's OEM tire-size specifications, so you won't have any problem.
It's interesting that you selected the OEM tires size (Michelin PS2) that Porsche uses on some of their cars.
--Spike
But, the sizes you mention on 18" wheels are within the Z's OEM tire-size specifications, so you won't have any problem.
It's interesting that you selected the OEM tires size (Michelin PS2) that Porsche uses on some of their cars.
--Spike
Originally Posted by wasiu0607
One last question lol.
If I get 235/40 in front, which is 1% increase odometer & speedometer reading, and rear 265/40, which is 1.27% increase, does the car take the average of these two?
If I get 235/40 in front, which is 1% increase odometer & speedometer reading, and rear 265/40, which is 1.27% increase, does the car take the average of these two?
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Originally Posted by Spike100
^^ Not sure what you mean when you say "average of these two."
But, the sizes you mention on 18" wheels are within the Z's OEM tire-size specifications, so you won't have any problem.
It's interesting that you selected the OEM tires size (Michelin PS2) that Porsche uses on some of their cars.
--Spike
But, the sizes you mention on 18" wheels are within the Z's OEM tire-size specifications, so you won't have any problem.
It's interesting that you selected the OEM tires size (Michelin PS2) that Porsche uses on some of their cars.
--Spike
They are? I thought the Z's OEM specs for 18" are 225/45F and 245/45R.
Anyways, what I meant was from the calculator Dave gave me, it said I will have 1% increase in speedometer and odometer if I switch fronts from the OEM 225/45/18 to 235/40/18, which means at 70 mph, the actual speedometer will display 70.7 mph. I just wanted to know since my front is 1% increase and rear is 1.27% increase, will the car take the average of the two to display on the speedometer?
Originally Posted by davidv
Cant tell jack. What is the wheel diameter?
18" Dave
Last edited by CKY881; Jul 14, 2008 at 08:09 PM.
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^^ No it doesn't average the two, but instead depends upon the overall diameter of the currently mounted tire.
My Porsche comment was only to point out that the tire size you ask about fit Z's perfectly, but are also a size that Porsche uses on some of their cars. It was simply an observation and nothing to do with the premises of this discussion.
--Spike
My Porsche comment was only to point out that the tire size you ask about fit Z's perfectly, but are also a size that Porsche uses on some of their cars. It was simply an observation and nothing to do with the premises of this discussion.
--Spike
Originally Posted by wasiu0607
They are? I thought the Z's OEM specs for 18" are 225/45F and 245/45R.
Anyways, what I meant was from the calculator Dave gave me, it said I will have 1% increase in speedometer and odometer if I switch fronts from the OEM 225/45/18 to 235/40/18, which means at 70 mph, the actual speedometer will display 70.7 mph. I just wanted to know since my front is 1% increase and rear is 1.27% increase, will the car take the average of the two to display on the speedometer?
18" Dave
Anyways, what I meant was from the calculator Dave gave me, it said I will have 1% increase in speedometer and odometer if I switch fronts from the OEM 225/45/18 to 235/40/18, which means at 70 mph, the actual speedometer will display 70.7 mph. I just wanted to know since my front is 1% increase and rear is 1.27% increase, will the car take the average of the two to display on the speedometer?
18" Dave
Originally Posted by davidv
Speedometer will read 101.27 MPH at 100.0 MPH.
So speed on speedometer will be based on rear tires then? Does that mean I can go as small as possible with the front tires and speedometer & odometer will still only be off by 1.27%?
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