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What offset do I need?

39K views 54 replies 9 participants last post by  Ivan1993 
#1 ·
I'm looking to buy 315/35/20 nittos to fit 20x10.5 wheels. I am unfamiliar with offsets so I was wanting to ask you which one I'd need to prevent any significant sticking out of the wheel/tire. Any other insight on offsets would be greatly appreciated too! Thanks!
 
#2 · (Edited)
Let's assume your'e talking about rear only, as there's no way you could put that on the front!

Though I know some people go as wide as 275 in the front, and like to do that on all 4 corners so they can still rotate tires. My opinion is that over 255 wide on the front starts making the steering a little too heavy.

315 is a little wide! It fits, but IMO 305's I think would look better and be plenty enough meat for a stock car. Now if you had a supercharger and were putting down 500++ rwhp then you might want (still probably not need) all that extra meat. FYI, even the 662hp GT500's only come with 285 wide rear stockers.

Anyway, if you're looking to put a 12"+ wide tire, I'd say 55-60mm would probably be good. Less if you want them to stick out the wheel wells more & have a wider overall stance. But they'll throw rocks up at the back of your car.
 
#5 ·
No you're right. I meant pulling the fenders which you can with these fenders just a fraction maybe 3mm which I would just recommend getting the right offset so you don't need to pull it.


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What about being lowered 1.5" gents? I'll definitely be in the market after winter for some new shoes and rubber. Doesn't seem like I have much room to play with back there, although I'm still running the 235/50/18 garbage huge sidewall p zero nero....


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#6 · (Edited)
I'm running a 2" drop. With a 1.5" you may still have issues on big bumps because the live axle suspension doesn't camber the rear wheels in.

But stock wheels will have no problems at all with offsets and rubbing.

So keep in mind that 315 on a 10.5" wheel may rub on a +50mm offset wheel but may not run if it was on a 11 or 11.5" wheel because the corners of the 315 tire won't be out as far from being pinched by too narrow wheels. I hope that make sense. Lol

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#9 · (Edited)
Honestly as long as you keep the proper width tire with the proper width rim the correct offset for the rear is +45-50.

285 - 10"
295 - 10/10.5"
305 - 10.5-11"
315 - 11-11.5"
325 - 11.5-12"

If you undersized the rim with too fat a tire you will bulge a portion of the corner of the tire past the edge of the rim therefor effectively lowering the offset as a side effect which may cause rubbing.

But as long as the proper tires are installed on proper sized wheels then a +45-50mm should clear everything you put on upto and including 325.

Go with as close to +50mm if you can without going over.

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#55 ·
Honestly as long as you keep the proper width tire with the proper width rim the correct offset for the rear is +45-50.

285 - 10"
295 - 10/10.5"
305 - 10.5-11"
315 - 11-11.5"
325 - 11.5-12"

If you undersized the rim with too fat a tire you will bulge a portion of the corner of the tire past the edge of the rim therefor effectively lowering the offset as a side effect which may cause rubbing.

But as long as the proper tires are installed on proper sized wheels then a +45-50mm should clear everything you put on upto and including 325.

Go with as close to +50mm if you can without going over.

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I know this is old, but I’m looking to put 315/35/20 on a 20x11 +55 offset wheel. (2014 Shelby gt500)
 
#10 ·
Well, I'd like to get as much rubber in the rear as possible and safely, but I am pretty low like I said. If I had to choose I guess a 295 or 305 if possible? Offset is key here though I see....I say that because I'm a fan of concave wheels. I'm currently looking at STR 607 wheels. I have to recheck the offset but I'm sure it's probably around 40+


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#11 ·
I have +45mm and the 285 Nittos I had was clearing the fender by a few mm at most. I have 305/35/20 on right now on 10" wheels. It bulges past the rim a few extra mm and rubbed on both fenders. I pulled the fenders out like 3-4mm and there's no more rubbing. So if you want to use me as an example here's how it goes:

305/35/20 on 10" +45mm rubs until I pulled the fender 3-4mm so... That means to solve the clearance issue without pulling the fender:

1.) Have 11" rims with +45mm so that the tires seat correctly and not bulge out as much which would give me that 4mm clearance needed.

2.) Stay with 10" rims but have the offset at +49mm or 50mm even so I get that 3-4mm clearance


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#15 ·
Yeah 19" would be slightly easier to option out simply because you'll have typically a shorter tire comparatively to 20s so you have more travel room before rubbing especially if you're running 1.5" drop.

But tire prices are supposedly higher because 19" is like a bastard stepchild or something when it comes to companies making tires in those sizes.

That being said you should still heed the general guidelines close to the same as 20s.


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#14 ·
Dallas I just checked real quick. The wheel I really want is STR-Racing's 607. It's a thin spoke concave wheel. In 19" diameter they have front wheels in our pattern 8.5" with a 35+ or a 10" with a 40+. And the rear is an 19x10 40+ as well. Is that offset too low? Sorry for being a noob lol


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#16 · (Edited)
Yeah I wouldn't do +40mm on the rears and certainly not 10" on the fronts. You'll for sure have rubbing issues with 10" fronts.

If I remember correctly +40 was good for new edge but not for ours. I would go no lower than +45 although stock brembo wheels are +42...

One option is you can run narrow tires to stretch the tires just a bit.

Meaning that if you run 20x19x10 rims with +40mm offset which is optimal with 285-295 tires you can run 275 for an extra few mm of clearance on the rubber.

Also depends on tire manufacturers too. Nittos run narrow whereas Mickey Thompsons run a bit wide. So a 285/30/19 Nitto may work with that offset.

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#17 ·
Yeah I was definitely assuming the front would have to be 19x8.5 and I'm fine with that. I was just hoping to get some sizable rubber out back. I wish they made the 19x10 in at least a 45+...I'm not fond of stretching tires, but I've kind of stuck myself in between a rock and a hard place....


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#19 ·
275 is in no way really stretching the tires on a 10" rim. However, 285 MT street comps run a bit wide so that might be pushing it on +40mm.

Safest bet are Nitto Invos at 285/35/19. I hear they're pretty decent track tires but are crap drag tires (straightline). 555 are crap beyond all recognition and I'd rather ride my bicycle or push my car than use them again.

Some of the higher hp guys here love the Nitto 555R which are drag radials but they will last you a whopping 5-7000miles of tread life lol.

So yeah I think the Nitto Invo 285/35/19 will work without issues on your +40 rims.


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#25 · (Edited)
I'm running 315/35-20 Nitto Invo's on Forgestar 20x11 rears, +55 offset. I'm lowered 1.5" and have no problems. 275/35-20 fronts on 9" wheels, +35 offset. AM has good prices on Forgestar.
 
#29 · (Edited)
Here you go, played with photo editor:







 
#30 ·
That looks REALLY good. Everything ties into each other very well.


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---------- Post added at 06:32 PM ---------- Previous post was at 06:31 PM ----------

And the rear wheels look pretty flush with the fender.


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#31 ·
Thanks.
 
#32 · (Edited)
Looks awesome! I drove alongside this mustang and his tire was fat. Really meaty. Never got a chance to get him to pull over. By comparison to my 305 Mickey T Street Comps he must of had 335 then cuz my 305 are about your size.

I guess I just gotta widen my 10" CS40s to 12" to fit those 335s lol

Fat tires and mustangs just looks good together.

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#36 ·
Lol ok. Any other suggestions for a summer/track grippy tire? I only included invo's because it seems a lot of people have them. But that's why I'm hear, to learn what's good and what isn't. Especially with something as significant as tires.


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