FD Wheel and Tire Sizing
 

To help answer the repeated questions about wheel and tire fitment on the FD, I threw together the attached Excel spreadsheet (zipped). Directions and detailed explanations of terms are included.

If you have any suggestions for additions or changes, please post them here or send me an e-mail.

Note: you may have to enable Data Analysis to display all of the formulas correctly.

1. Click on the Tools menu and select Add-Ins.
2. Check the box next to Analysis ToolPak and click OK.
3. The original installation disk will be required if this feature has not already been installed.

AWESOME post! :big thumb:

Nice, Jim, however, you know the lazy fucks are still going to ask fitment questions anyway. :)

And BTW, under, "Front Wheel Offset", last two sentences of the first paragraph, "A larger offset will move the outer face or edge of the wheel towards the outside of the car. A smaller offset will move it inward."

Isn't that backward?

A larger offset (+50) moves the wheel inward, a smaller offset (+30) moves it outward, hence rubbing issues w/ low offset wheels.

Good catch. :bigthumb:

I also clarified that it's only the rear tire that affects actual vehicle speed. :)

If there are more changes/revisions required, I'll re-post the sheet.

Nice spreadsheet, Jim.

Curious why you're using truncate instead of round?

Gene

:bigthumb: Very useful, yet as we all know, in about 9 minutes, 22 more seconds, there will be a new "does X width with X offset fit on an FD?" post. Thanks for the useful cheatsheet tho!

edit:
The spreadsheet doesn't have sizes for my 26's, what da dealie yo? :D

ROUND(15.5, 0) = 16
TRUNC(15.5, 0) = 15

I just wanted to convert to an integer, not potentially change the integer. :)

I figured 20s were pushing it, but someone would eventually ask. "Ticonderoga-class" wheels will have to wait for version 2.0. :p:

Yo, I stole some off a train this morning. Got them at the platers right now :D

Understood. However, for tire diameters I believe that most, if not all manufacturers exceed the calcuated tire diameters. That's why I typically use round- at 2 + significant figures.

Gene

I could have simply formatted those cells to show 2 significant digits also and rounding would have been accomplished, but I was having fun playing with the TRUNC function. :D

Note that if you change the formula to use the ROUND function instead, many results are the same, and if not, vary by only 0.01", as you'd expect. Is one one-hundredth of an inch really that important? :p:

I expect the subject to be more like "rimz" or "rimm joB hook Up fitty ?????".

-Max

Not when you're going to change the diameters by that much with one drop of the clutch :)

hey i'm a noob (don't mind the join date) that is still confused, i was trying to figure out the correct offset for 17x9.5 for front and rear on 255/40 tires. the twist is i am using the feed fenders up front that adds .8". i want to be able to rotate wheels/tires, so if i am using this correctly the correct offset is 38 for front and rear. is this right?

If you're using wider front fenders with factory rears, then it's likely that the the rear is now the limiting factor. You want to get as far outward as possible in the rear, so that it doesn't look too tucked in up front. 17x9.5 +38 should probably be about as good as you're going to do with the same thing all around... although you could probably run it with a larger tire front and rear... more like a 275/40.

I've seen some japanes wheel sites list offsets as low as +36 for a 9.5" wheel for the rear, so it MIGHT work, but I wouldn't be sure, and wouldn't wantto say it would work with any size and brand of tire.


L??\0\0\0\0L?\0hey i'm a noob (don't mind the join date) that is still confused, i was trying to figure out the correct offset for 17x9.5 for front and rear on 255/40 tires. the twist is i am using the feed fenders up front that adds .8". i want to be able to rotate wheels/tires, so if i am using this correctly the correct offset is 38 for front and rear. is this right?[/QUOTE]

You're getting good at this Max. I still laugh my ass off at that other post you wrote a while back :D

Sticky!!!

This should be a sticky...great info.

added to our Suspension and Handling Links sticky.

so i'm playing with this some more to get the hang of it. here are some different wheels, let me know your opinion.

18x9.5 45 offset for front and rear on 265/30/18 tires. on stock front fenders the wheel would be to close for comfort, but adding the feed front fender gives plenty clearance. for cosmetic purposes i would have to add spacers to the front, right? this will also give me more clearance for the spring/shocks?

just bumping this back up


THIS SHOULD BE ADDED TO THE ARCHIVE!

Excelent information, should be more readily available, I have been searching the wheel and tire forum for over an hour now, found this and doubt I will ever have to search this section again.

Excellent info Jim. Thanks for taking the time.

Using the information on your chart, I see that 18x8.5 with a front offset of 38 and a rear offset offset of 25 would give me plenty of room to the inside of my wheel wells with a 245 35 tire while maintaining an accurate speedo reading.

My question is this. Would the same size tire front and back look bad? I'm trying to ensure that I have no rubbing issues, but I want the tire to fill up the wheel well nicely as well. I know that most guys run different sizes front to rear. Just looking for opinions before I order, and thanks again for the sizing info!

Hey, one problem, i've got Microsoft Works, and excel for some reason won't transfer....what the dilly yo...gangsta?

It's in our link list but I forgot to put it in the archive. Done.