how to tell if theyll fit?

[1stGenRocks]

ok i know the will it fit threads are a pain in the neck so whats the best way to know whether wheels will fit other then putting em on and driving around to see if they rub?

the wheels im looking at are icw stillettos. 18x7.5 42 offset, 5.90 backspacing. they have 225/40 tires on them

my car is a 91 awd with like 1 1/2 inch drop ?progress? springs. not sure on the springs since they were on when i bought it.

 

[wret]

The easiest way to estimate the fit of a new wheel/tire combination (and the method I use) is to compare them to a known good, which is typically stock dimensions.

Use a tire size calculator like this to estimate the changes in radius and width. Figure in your offset change. Then look for obstacles in space the new wheel/tire will occupy.

Try the calculator, then post again with your thoughts and questions. Here's a tip: something about the wheel/tire combo you proposed is not quite right. Can you tell what it is?

 

[1stGenRocks]

ok i used the calculator and it says the speedo will be off by 0.8%.

how do i find the actual width of the mounted tire and know where it will end up with a 42mm offset?

heres the results
.............Specification.....Sidewall..Radius .Diameter..Circumference..Revs/Mile..Difference
stock 1g 205/55-16........4.4in......12.4in....24.9in......78.2in...............811..........0.0%
stillettos 225/40-18........3.5in......12.5in....25.1in......78.8in...............804..........0.8%

btw according to the specs i can find these should be lighter then my current 17's

im not sure whats wrong with my specs either so youll have to give me a hint. heres the link i got the info from http://www.icwracing.com/wheel.php?wnum=25 theyre the last one on the list. the guy selling them says they are 5x100 or 5x114.3 lug pattern and they look like dual pattern so im not sure why the site only lists them as 5x100.

 

[wret]

You found it. The tire diameter is less than stock. Some are not happy with the increased wheel gap. The speedo change would be negligible.

Although section width and tread width does vary between tire designs, you can just use the spec width numbers unless you think something will be really close (then you can refer to manufacture dimension data). So, if you are going from a 205 to a 225, the tire will be 10mm wider on either side. Because the new wheel has less offset, +42mm instead of +46mm, you can subtract 4mm width on the inside and add it to the outside. In effect, the new wheel will be 6mm wider on the inside and 14mm wider on the outside. Do you have this space available?

Increase in height complicates things even more, but since your proposed new tires are smaller in diameter, you won't need to worry about it.

 

[1stGenRocks]

why do you say the new ones will be smaller? the stock are 24.9 in diameter the 18's are 25.1 so it looks like theyll be about the same?

i also found specs for the wheels i have now. nippon racing wishgbone 17x7 42 offset. currently i have on 225/45 tires and have no rubbing except for one spot where my fender is dented in from when i bought it. i guess this means i should be okay with the 18's since theyll basicly be the same as what i have on now? im planning to roll the fender and straighten out the dent as soon as the weather is decent again

 

[wret]

Whoops, I was thinking your new wheel was 17". I was trying to figure out how you got those numbers. The 225/40/18 is pretty close to stock diameter. +2mm actually.

 

[jtmcinder]

Wrapping this up, a +42 offset will be fine on either generation of DSM.

- Jtoby