Right offset for 18x8.5's

[Flash]

OFFSET RECOMMENDATION REQUEST FORM

Please answer the following questions when requesting tire size recommendations.

1. My car is a: 2g

2. My wheel size is:
Diameter: 18"
Width: 8.5 (if it's even possible)
Offset: Need Recommendation

3. My tire size is: 225/40/18

3. My current or future suspension height will be lowered
a) One inch or less
b) One to 1.5 inches
c) 1.5 - 2 inches
d) More than 2 inches.

4. If suspension is lowered,
a) Rear camber will be adjusted to less than 1° negative.
b) Rear camber will be adjusted to within 1° to 1.5° negative.
c) Rear camber will be more than 1.5° negative.

5. Rear fender flange rolling:
a) My fenders are rolled or will be if necessary.
b) I will not roll the fenders.
c) Undecided, preferably no.

6. My driving style is:
a) Street only, with no special performance requirements.
b) Street only, but I like to feel secure on twisty roads.
c) Street and Strip.
d) Street and Autocross.
e) Other

7. I have searched for and read the FAQ's, Tech Articles, and threads on wheel and tire fitment:
a) Yes, but I just need someone with experience to validate my choices.
b) No, I just want someone to tell me what to do.
c) Yes, but I can't find the right answer and need someone to tell me what to do.

 

[Flash]

I hope that works and helps Wret and everyone else out. Less confusing I think.
Thanks for the help you all.

 

[vaboys2ndgen]

im not sure, i know wret will know . but im running 18x8s 235/40 tire and i wanna say my offset is +35mm. not 100% though.

 

[wret]

If you plan to go no bigger than 225/40/18's you could go with a higher offset: +45mm. If you think you might want to go bigger in the future, like 235/40/18 or 245/40/18, I would go with +40mm.

With your rather aggressive lowering (and camber correction), I think you will still need to roll the rear fender flanges, even with the 225's.

 

[gsx rated98]

for a while i was running 18x8.5 +43mm offset, with 225 40's. My suspention was koni reds on sportlines. So there was about 1.7inch drop.

I never had any issues with the tires rubbing, and i didnt need to roll my fenders. When i went to a 235 40 tire i did have to roll the rear fenders.

 

[wret]

for a while i was running 18x8.5 +43mm offset, with 225 40's. My suspention was koni reds on sportlines. So there was about 1.7inch drop.

I never had any issues with the tires rubbing, and i didnt need to roll my fenders. When i went to a 235 40 tire i did have to roll the rear fenders.

Any idea what your rear camber angle is?

 

[gsx rated98]

When i first put the suspention setup on i didnt have a camber kit, and the car looked almost like a damn drift car, rear camber was horrible. Still didnt rub. When i put the camber kits ok, i kept it at stock -1 to -2, no rubbing.

With the 235 40s, i could only do -1.5 or the tire would of rubbed the upper control arm.

 

[jtmcinder]

With the 235 40s, i could only do -1.5 or the tire would of rubbed the upper control arm.

That makes no sense. The knuckle and upper control arm both move with the tire as you change the camber, so camber setting has nothing to do with the tire rubbing the suspension. In contrast, camber changes can cause the tire to rub the fender lip.

- Jtoby

 

[jtmcinder]

2. My wheel size is:
Diameter: 18"
Width: 8.5 (if it's even possible)
Offset: Need Recommendation

Why carry the extra weight (and cost) of 8.5"-wide wheels if you're only going to put 225s on them?

If you are committed to these tires, anything from +40 to +45 would be good, regardless of whether it's a 18x8 or 18x8.5.

- Jtoby

 

[gsx rated98]

That makes no sense. The knuckle and upper control arm both move with the tire as you change the camber, so camber setting has nothing to do with the tire rubbing the suspension. In contrast, camber changes can cause the tire to rub the fender lip.

- Jtoby

Sorry, what meant was that the tire would lay againt the arm. It wouldnt touch through suspention travel, but would rest against it.

 

[Flash]

Right now with my suspension raised I have zero camber. And that's how I drive my car 99% of the time. When I go to shows I lower it down about 1.5-2" and I drive like that to the show.

 

[wret]

Right now with my suspension raised I have zero camber. And that's how I drive my car 99% of the time. When I go to shows I lower it down about 1.5-2" and I drive like that to the show.

Ahh, so...
When you lower it you will have a lot of negative camber. This makes it easier to tuck the wheels. Just go with +40mm offset if you have a choice.

 

[prostreetdsmx1]

I would go with a 235/40 or a 245/40 with a +40 - +43. I like lots of rubber.

 

[jtmcinder]

Nah. Too big in diameter. 245/35/18. Our cars like tires under 25" because 1st is pretty high, although maybe this isn't the issue with FWD.

The correct offset for 245/35/18 is around +38. It would want a rolled rear fender lip if the rear arms are spaced out.

- J "I can't believe we're talking about 18s seriously" toby

 

[Flash]

Nah. Too big in diameter. 245/35/18. Our cars like tires under 25" because 1st is pretty high, although maybe this isn't the issue with FWD.

The correct offset for 245/35/18 is around +38. It would want a rolled rear fender lip if the rear arms are spaced out.

- J "I can't believe we're talking about 18s seriously" toby

What? You say a 225/40/18 won't work? You suggest a 35?
I found the wheels, they are 18x8.5 +40. I will run my 225/40/18 for a while before I wear them out and get 235/40/18's.
I just want to double check the 18x8.5 +40 will fit with a 225/40/18 tire without rolling fenders or adjusting camber "that" much (even though I have access to an alignment rack at work.)
Maybe someone had some experience with that size wheel since we last talked. I don't want to spend $$$$ on a set of Volks and have then rub and not fit.

 

[92awddsm]

im not sure, i know wret will know . but im running 18x8s 235/40 tire and i wanna say my offset is +35mm. not 100% though.

Actually, its +39 and it is only an 8" wheel. 35 would push the wheel outward and cause rubbing problem on the rear and same in the front while in compression with the wheel turned.

Off topic but on a 1g, I would prefer a +38-40 on the rear and a +40-42 on the front with 235-40-18's and 8" wide wheel.

 

[Flash]

Bring this back, I'm still trying to figure out the correct width to get. I will roll the fenders soon. But JToby, you suggest a 245/35/18? Why not a 245/40/18?
Wheel size: 18x8.5 +40.

 

[T Money]

I have some 18x8.5s with a +40. My tires are 235/40 BFGs. I had to roll the back fender lips to stop the rubbing. I don't think i could have went with a wider tire. As it sits (pretty low) there is barley any clearance for the back inside of the tires.

 

[Flash]

I currently have an 18x8.5 +40 wheel with a 225/40/18 stretched on it. I'm trying to kill my current tires so I can get new ones, but I want 245/40/18, just don't know if they fit or not.

 

[chris712vt]

Bring this back, I'm still trying to figure out the correct width to get. I will roll the fenders soon. But JToby, you suggest a 245/35/18? Why not a 245/40/18?
Wheel size: 18x8.5 +40.

245/40s on 18s will result in a 25.64 inch tall tire.
245/35s on 18s will result in a 24.69 inch tall tire.
See above where "jtmcinder" recommended keeping your tire height below 25 inches.

Just for reference, I run 245/40s, but on 17s, resulting in 24.64 total height.

I can't tell you why it is recommended to stay below 25 inches, maybe for clearance issues, maybe because it will mess with your gearing too much, I don't really know. But I can tell you how tall your tires will be haha.

 

[Kakoriat]

I have 18x8.5 wheels, 41 offset with 235/40 Azenis. I've heard the Azenis tend to be a little bit wide for their size and these barely fit. I have about 2-3mm's of clearance by the control arm and had to roll the fenders as well.I would imagine a 245/40 would end up being too tall with a 40ish offset and would rub the control arm. You'll probably need a 35-38 to make those fit. Then you run into the possible problem of the tire rubbing the outside fender even if it is rolled. (not 100% on that)

Here's a picture of my control arm with the 235/40's in the rear. Hope this helps.

 

[Flash]

How tall would a 235/40/18 be?

 

[Kakoriat]

My Azenis have a 25.5 OD according to Falken.

 

[chris712vt]

How tall would a 235/40/18 be?

235 mm (width) x .40 (aspect ratio) x 2 (both sidewalls) x .039 (convert to inches) + 18 (rim diameter)

the 235/40/18s would be 25.332 inches tall.

Just curious, but why do you seem to really want a 40 series tire instead of 35? In reality, the sidewalls of the 235/40s are only 8.25 mm thicker than the 245/35s.

 

[Flash]

I work at a Porsche dealer. And a lot of the newer Porsche's use a 225/40/18 or 235/40/18 on the front. So I could get a really good deal on them.