jimlab

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.

7racer

AWESOME post! :big thumb:

SpeedKing

iTrader: (4)

Nice, Jim, however, you know the lazy ***** 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.

jimlab

Good catch.

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.

gfelber

Nice spreadsheet, Jim.

Curious why you're using truncate instead of round?

Gene

RedR1

iTrader: (5)

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?

jimlab

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

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

jimlab

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

DamonB

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

gfelber

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

jimlab

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.

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?

maxcooper

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

-Max

gfelber

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

wptrx7

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?

ptrhahn

iTrader: (9)

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]