Wheel Specs?

DGatzby,

We may in fact be saying the same thing.

To make sure I'm going to reiterate here as to what I want.

Our stock wheels are 9.5 inches wide with an offset of 18 mm

In order to get a 10.5 inch wheel that doesn't stick OUT away from the car any further than the stock wheel
you need to get it with an offset of roughly 30 mm (31mm to be exact)
However, because the wheel is 1 inch wider, that 1 inch has to go somewhere, and in this case with a 30-31mm offset it, that one inch of wheel will be 1 inch closer to the suspension.

Unless you are saying we do not have 1 inch of space in there, which it looks like we do, except the plastic wheel well cover, which we can mold or cut away, I don't see how a 315/35 tire on a 10.5 inch wheel in the rear would rub.

Now I'd be worried about going with anything wider than a 10 inch wheel in the front as there doesn't seem to be a lot of room there near the top of the wheel, where there is a black angled suspension bar about a fingers width away from the stock tire already.

Driver72 you do get it and I will respond to you. I understand the offset/backset. I did not work in a tire shop and instead received an engineering degree, with a math minor. The poster above is correct the math is right. He is wrong when he says no need to check however. I was also a carpenter and now direct large construction. Check and re-check your measurements!

Now one more time. This concerns the backs only. I would not mess with the front, go for some 9.5's and leave the spacing alone. Don't get me wrong, if we could stuff the wheels and tires back in there 40 mm I would be happy, but there is a hard problem we can't move. It is located on the front inside. It looks like a rib in the liner. Coldheartid reports his large 315's on the 11" with ONLY a 21mm offset is close. He posted he can run his finger btw the tire and the hard surface.

1. I have 305/35 mounted on the OEM 9.5's. I can move a 1/2" rod between the hard surface and the TIRE.
2. I posted pictures for everyone showing 1- edge of a 305 on the outside is dead even with the sheet metal on the top. And 2- the 9.5" wheel edge is 5/8" inside of the outside edges of the 305, it will be a bit worse or greater with a 315. Now I don't care if you want to be anal with the outside edge of the wider wheels but the tire really conceals it. Besides the problem is that when you talk about offset you are moving the centerline of the TIRE/wheel. In this case we can only move that tire/wheel assembly so far before it will rub the inside.
3. Considering ColdheartId comments and his wonderful job of pioneering and finding nearly the only off the shelf wheels that work along with my measurements AND I don't give a damn about where the wheel edge sits. I think we can order a 25mm offset with some 305's and they won't rub. I am not ready to say another 5mm or 1/4" (30mm) works. I really have my doubts you can fit a 315 with a 30 mm offset. You may get a 305 at 30 mm, but I will let someone else try it for me.

I want to be wrong on the prediction. I am not wrong on the relationships and offset/backset. Anyone who is selecting their own equipment better be able to read those fundamental dimension charts like I posted yesterday and not just pick offset numbers because they are even numbers unless your retailer has a generous return policy.

DGatzby,

You may be right about the 30 mm offset on a 10.5 inch wide rear wheel not working with 315 tires, that may in fact be cutting it too tight.
The only reason I said I think it would was because of Coldheartid's post.
He made a 11 inch wheel with a 21 mm offset work with the 315 tires and said there is plenty of room?
That's a wheel that's 1/2 inch (13 mm) wider but the offset is only 9 mm difference.

But it wouldn't matter anyway, as I haven't found one single 20 x 10.5 wheel with a 30 mm offset. Most are 20-24 mm.
So if I had too, I'd go with a 24 mm offset. That would push the wheel about 6-7 mm further out away from the car.

But again, the issue is, the wheels I've found that I like the best are 20 x 10's and have a 25 mm offset.
Which is actually perfect, but pushing the limit for a 315 tire, where a 10.5 inch wheel would be best for a 315 tire.
But I haven't found a 20 x 10.5 inch wheel that I like with an offset even at 24 mm.

So it's a conundrum right now.

Thanks.
I have never used a spacer before on any of the numerous aftermarket wheels I have boughten.
However, I've never owned a car with so few wheel choices that fit/work.

Unless the wheel he is using a 10.5" rear wheel that has an offset of like 15, he shouldn't need a 25 mm spacer.
I'm apt to think a 10.5" rear wheel with a 20 mm or high offset will work based on the clearance I see in the rear.

It's the fronts that are tight. The wheels I like that come in 20 x10 or 20 x 10.5 size all seem to have a front wheel that is
20 x 9 or 20 x 10
So I feel if I could put a 20 x 10 up there, it would be great.
But it would be REALLY close to hitting the suspension part.
But I wouldn't want to use a spacer up front unless it was a small one like 7 mm (about 1/4").
Anything more and it will force the front wheels out too far for my liking.

Driver72 said:

OK, I've researched a bit more.
this backspacing and offset thing seem to be two ways of finding out the EXACT same information. So why did they start to talk "backspacing" in the past couple years.

Backspacing is the distance from the back of the wheel to the back of the mounting hub
Offset, as has been the standard forever, is the distance in millimeters OUTWARD or INWARD from centerline of the wheel to the mounting hub.
So to me, what's the point of measuring backspacing, it just causes confusion, and here's a perfect example.

I'm looking at wheels for the Hellcat that will look aggressive and not "cheesy aftermarket looking" so I can take off and store the forged OEM wheels, so if/when it comes time to sell the Hellcat, the OEM wheels will be immaculate, adding to the value of the car.
I'm also wanting to find 20x10 wheels so if I decide to put 305's on the car, it's within the recommended rim size and I don't have to worry about ballooning or anything putting 305's on a 9.5 inch wide wheel.

The wheel I am looking at is a
20 x 10
says it has a offset of 25 mm
Which is perfect compared to stock. Wheel won't stick out any further than current OEM wheel, but actually the face of the wheel will sit inward a measly 1 millimeter, but because the wheel is 1/2 wider the additional 1/2 inch is all on the inside, meaning it's wider inward toward the suspension and tucking under the wheel wells.
However, this same wheel says it has a backspacing of 6.50"
Well, how in the heck can it have a 6.50" backspacing but have an offset of 25mm from the centerline of the wheel. There is a 1/2 inch discrepancy there.
So either the wheel has a 25 mm offset and a 6.00 inch backspacing or
the wheel has a 6.50" backspacing or a roughly 38 mm offset

So unless I'm missing something with this backspacing stuff, I don't know which to believe on this wheel.???

Click to expand...

Driver, someone may have answered this but if not, a 20x10 wheel is 10 wide at the tire mounting lip, but backspacing is measured from the outer lip and the accepted thickness of the outer lip is 1/2 inch on each side of the rim, therefore the backspace of a 20x10 rim would be 5+1/2+offset (if positive) measured from the outer rim lip.












5

hellcatfast said:

Driver, someone may have answered this but if not, a 20x10 wheel is 10 wide at the tire mounting lip, but backspacing is measured from the outer lip and the accepted thickness of the outer lip is 1/2 inch on each side of the rim, therefore the backspace of a 20x10 rim would be 5+1/2+offset (if positive) measured from the outer rim lip.

Click to expand...

Yeah, but isnt backspacing is a more recent term when talking wheels, but it's kind of a duplicating information?
If you have the offset of the wheels, that's really all you need. You can do the math to find the backspacing from that, because the offset is the same thing, tells you how far from the centerline of the wheel the mounting surface is.

So a 20 x 10 wheel with a 25 mm offset is going to have a wheel that sticks in toward the suspension 13mm (1/2") more than the stock 9.5" wheels with 18 mm offset.
The 20 x 10 wheel with a 25 mm offset will also stick out toward the road 1 mm more than the stock wheel too.

That's my dilemma. Look at the space between the top of the stock wheel/tire and the suspension assembly on the FRONT WHEEL. Turn your wheel all the way and then try to get a finger between them. It has at most just over 1/2" clearance.
So a 20 x 10 wheel with 25 mm offset will have a wheel that's almost touching that suspension assembly. There may be 1/8" inch clearance. Not enough for comfort in my book. But it the 20 x 10 wheel had an offset of 20-22 mm that would bring it away from the suspension assembly another few mils which would give the piece of mind I'd be looking for.
The only reason I'm considering 20 x 10 up front is because the wheels I like don't come in a 20 x 9.5 like stock. It's 20x10 or 20x9.
The 20 x 9 may look a bit small and the "deep dish" look to it is a bit lost on the 9 inch wheel compared to even the 9.5 and especially the 10 wide wheel.

Driver72 said:

Yeah, but isnt backspacing is a more recent term when talking wheels, but it's kind of a duplicating information?
If you have the offset of the wheels, that's really all you need. You can do the math to find the backspacing from that, because the offset is the same thing, tells you how far from the centerline of the wheel the mounting surface is.

So a 20 x 10 wheel with a 25 mm offset is going to have a wheel that sticks in toward the suspension 13mm (1/2") more than the stock 9.5" wheels with 18 mm offset.
The 20 x 10 wheel with a 25 mm offset will also stick out toward the road 1 mm more than the stock wheel too.

That's my dilemma. Look at the space between the top of the stock wheel/tire and the suspension assembly on the FRONT WHEEL. Turn your wheel all the way and then try to get a finger between them. It has at most just over 1/2" clearance.
So a 20 x 10 wheel with 25 mm offset will have a wheel that's almost touching that suspension assembly. There may be 1/8" inch clearance. Not enough for comfort in my book. But it the 20 x 10 wheel had an offset of 20-22 mm that would bring it away from the suspension assembly another few mils which would give the piece of mind I'd be looking for.
The only reason I'm considering 20 x 10 up front is because the wheels I like don't come in a 20 x 9.5 like stock. It's 20x10 or 20x9.
The 20 x 9 may look a bit small and the "deep dish" look to it is a bit lost on the 9 inch wheel compared to even the 9.5 and especially the 10 wide wheel.

Click to expand...

i agree when you are comparing wheels, backspacing (from outer wheel lip to hub mount) is very useful when can only measure for a wheel with no wheel to compare. My stock wheel and tire measured approx. .4 from the top ball joint nut bolt and approx. .5 tire side wall clearance out from the little casting boss at the top of the spindle arm. I used 22x10.5 20 offset, this gave me 6.53 backspacing, with 295x30 tires, I had just a very slight tire rub on the casting boss. I just ground down the casting boss because I believe there is no effect on the spindle arm strength. With the 295 tires I also had a very slight rub on the pass side against the sway bar when max turn so I used a 1/8 spacer on the wheel. Stock tire and wheel has approx. 57% of the wheel load on the inside, the combo I used has approx. 58%, so no bearing load difference (the 20x10 , 25 offset will be approx. 58%). If you use the 275x40 tires, the clearance between the spindle casting boss will be close, if need be grind a little or a 1/8 spacer and only move the outer side of the rim approx. 1/8 farther out than your stock rim is now.