E-Body Tire Sizes (what fits, what's too big, what looks good)

[HP2]

Ahhh, okay. I vaguely remember that.  It is a collection of member's combos. Not sure how long its been since it was updated.

So, Rikkitik is a member on here. He is actually using the stock E body axle housing on his combo, not a B body unit.  He has 15x10 with 6.5" of backspace and a .25" spacer to pull it that quarter inch off the springs side, so essentially a 6.25 back space net. Here is a reply with his combo: https://forum.e-bodies.org/wheels-tires-brakes-suspension-and-steering/12/mini-tub-and-spring-relocation-kit/28170/msg314026#msg314026

By way of contrast, I have springs moved in 1 inch, a 67 B body housing, 15x10 with 5" backspace and a 305 tire. I have approximately 1" from tire to the spring and 1" from the tire to the fender lip, and no spacers used anywhere.

Up front, there is  absolutely no way any 15" rim with more than 4.75" of back space will fit. This is because the lip of the wheel hits the upper ball joint once you get to the 5" backspace.  You have to move into 16, 17, or 18 inch wheels to get around that interference issue.

I am running 15x8 with 4.5" backspace and a 255 tire. At normal ride height, I had no interference issues. Since dropping it down 2.5-3", I have rolled the opening lip to avoid any issues at extreme lock and roll, although I doubt I'll have any roll issue causing interference with my bar combo.

Regarding the shocks, moving the springs in 3" to put them in the frame rails does not require any changes to shocks. It does make them more vertical, which slightly reduces their stroke and slightly improves their efficiency, but it also moves them further away from the tire which decreases their effectiveness.

Also, if you move the springs in 3" the next interference point will be the wheel wheel. So depending on how large you want to go, mini tubs may be required. This will gain an extra 1.5" or so before the frame rail becomes the  next interference point.   A low profile tire around 335 wide can fit in the stock, unmodified well, XV proved this. A taller, drag style tire will rub higher up in the well because of the its slight  taper against the body.

[PsyOps]

Thanks for link and the additional info HP2. 

[PsyOps]

OK, I'm back with another question.  HP2, in the link you referred me to, you posted: I've seen several people fit 335 tires in the stock wells, so they can swallow a fairly wide tire. However, the backspace on the rims has to be spot on and the overall diameter could be a factor as well. If you wanted to go with a wide and tall sidewall tire like a drag tire, then you may have issues at the top of the well.  I've read somewhere, and can't find it now, that someone is running a Nitto 325-50/15 (27.83" dia, 13.23" sect) tire on 15x10s with a B-body (year not specified) rear end, Dr Diff 1" spring kit and ESPO+1 springs.  I would like to duplicate that set up without moving the springs into the frame rails or backhalfing the car.  Mini-tubs are fine.  What do you think?

[Swamp Donkey]

OK, I'm back with another question.  HP2, in the link you referred me to, you posted: I've seen several people fit 335 tires in the stock wells, so they can swallow a fairly wide tire. However, the backspace on the rims has to be spot on and the overall diameter could be a factor as well. If you wanted to go with a wide and tall sidewall tire like a drag tire, then you may have issues at the top of the well.  I've read somewhere, and can't find it now, that someone is running a Nitto 325-50/15 (27.83" dia, 13.23" sect) tire on 15x10s with a B-body (year not specified) rear end, Dr Diff 1" spring kit and ESPO+1 springs.  I would like to duplicate that set up without moving the springs into the frame rails or backhalfing the car.  Mini-tubs are fine.  What do you think?

I should be able to answer some of your questions too.  I'm putting a 305/35r20 tire on an 11" rim in my stock wheel wells. It will be tight from my preliminary measurements.  Mods are  a 1" Dr diff relocation kit, a Dana 60 built to early B-body width, trimmed inner fender lip when doing the bodywork.  With the way I have everything set up, I ordered rims with a 5.75 inch backspace.  It will be close to the leaf springs, but I do not foresee any tire deflection at all.

[PsyOps]

I should be able to answer some of your questions too.  I'm putting a 305/35r20 tire on an 11" rim in my stock wheel wells. It will be tight from my preliminary measurements.  Mods are  a 1" Dr diff relocation kit, a Dana 60 built to early B-body width, trimmed inner fender lip when doing the bodywork.  With the way I have everything set up, I ordered rims with a 5.75 inch backspace.  It will be close to the leaf springs, but I do not foresee any tire deflection at all.
[/quote]

Thanks for the response 'Donkey.  What is the cross section width of your 305 tire (I could look it up but I'm too lazy tonight)?

[Swamp Donkey]

@PsyOps its 12.32 inches. Looking at the tires, they are definitely big. 

[PsyOps]

Appreciate the info @Swamp Donkey.  I really want to run some 325/50R-15 Nittos using a similar set up as yours but I'm afraid my tire choice will call for a US Car Tool spring relocation kit & mini tubs as the Nittos reportedly have a 13" tire cross section.

[HP2]

OK, I'm back with another question.  HP2, in the link you referred me to, you posted: I've seen several people fit 335 tires in the stock wells, so they can swallow a fairly wide tire. However, the backspace on the rims has to be spot on and the overall diameter could be a factor as well. If you wanted to go with a wide and tall sidewall tire like a drag tire, then you may have issues at the top of the well.  I've read somewhere, and can't find it now, that someone is running a Nitto 325-50/15 (27.83" dia, 13.23" sect) tire on 15x10s with a B-body (year not specified) rear end, Dr Diff 1" spring kit and ESPO+1 springs.  I would like to duplicate that set up without moving the springs into the frame rails or backhalfing the car.  Mini-tubs are fine.  What do you think?

Sorry about the delay in replying. Yes, IMO, you should be able duplicate that set up with a 1" relocation with 1"+ Espos without moving into the frame rails or backhalfing the car. You won't need mini tubs or even a 2" widening strip. You might have to roll the fender opening lip to avoid any potential sidewall contact.

My set up is similar, but not exactly like the above. I have a 1" relocation, '67 B housing, 15x10  w/5" backspace, zero arch leaf springs with a 26x12 MT SR tire.  So my car sites probably a good 3" lower than you example. My Tires are exactly 26x12 with the 12 being section width, not tread width. With this arrangement, I have exactly 1" of clearance to both the fender lip (mine are not rolled so they are still like the factory razors) and to the leaf spring. The Nitto 325-50/15 (27.83" dia, 13.23" sect) is a 1.83 larger diameter, so roughly an inch taller into the wheel well (remember it will only take half of the extra diameter in any direction).  These are also .615 wider on each side (13.23-12/2).  On my car, I would have approximately 3/8" of clearance to the wheel well lip and the leaf spring. So pretty cozy, but workable. Rolling the lip will gain you an extra 1/2" on the razor side.

Its also worth mentioning that not all cars are identical and it may take some manipulation to ensure your rear housing is exactly centered to the body to get even measurements in each way. Mine was actually closer to the passenger side. A little time with a die grinder on the axle mounting pads allowed me to slide it over to the drivers side and end up with an even 1" on both side against both the body and the spring.

Just for grins, here is a 295/65R15 drag radial on an 8" rim under my Challenger. This was a test fit. I never drove it this way. That tire 30" tall, 12" section width. Springs were still in the stock location and arch and this was a stock E body housing. Sadly, I didn't take any exact notes on its fitment. Notice it has a pretty significant rake to it with a 235/60 front tire. Even with a 28" tire, you are going to need to turn up the torsion bars some or run a taller front tire

[PsyOps]

@HP2, thank you so much for your detailed reply with pics.  This info is exactly what I need to move forward.  The 295/65R-15 drag radials in the picture are just a tic shy of 2 inches taller than the Nittos (your 30" vs Nitto's advertised 28.3") and I am considering tall(er) front tires - something along the lines of xxx/75R-15 to get the front end up a little.  Looking at old E-body pics at the drag strip, the taller front tires seemed to be the norm rather than the exception.  And yes, I'll definitively have to crank up the T-bars.  Now that all that is resolved, it's off to buy some tires, roll the knife edges & drop plumb lines onto some butcher paper so everything is perfectly positioned side to side.  I appreciate the help from you and @Swamp Donkey. 

[xx88man]

The A/R torque thrusts wheels are 3.75" backspace I believe. I know 4.5" is best but does anyone run these wheels on their challenger?

[whitsend]

Will these fit a stock ebody? i don't understand the 30mm offset. Thanks everyone   

[HP2]

Offset is the outer hoop's centerline relative to the mounting pad's position on the hub. Backspace is the distance from the back of the rim to the mounting pad.

At a 30mm offset, those won't fit in the rear without moving the springs and/or using a spacer. Up front, that is going to put them really far inboard and the tire might rub the inner frame rail on extreme turn angles.  FWIW, 30mm offset on a 9" rim is a 6.18" backspace.  A -30mm offset on a 9" rim is 3.75" backspace. Like the Torque Thrust question above yours, that is also a questionable fit as well as it will put the tires further outboard. That's great for spring clearance, not so great for fender lip clearance.

If you want to dig into this further, they have a good explanation article on it here: https://www.discounttire.com/learn/offset-backspace?cjevent=ffe09803ed4611ef80e7025d0a1cb829&CJAID=13390473&CJPID=100357191&utm_source=customdigital&utm_medium=affiliate&utm_content=277774&utm_glid=DT_AFFILIATE_ALL_CDIG_ALL_LOGO

Here is an offset/backspace calculator:
https://tireswheelsdirect.com/wheel-offset-and-backspace-calculator/

[HP2]

Posted this in another topic but am reposting it here since this is a tire fitting resource.

Test fit of a 10" wide rim with a 12" wide tire on the front of a Challenger. This approximately 305/45R15. Rim is 15x10 with 5" backspace, or -12.7 offset. The problem with putting this rim on the front of a Mopar is the spindle height. At 5" backspace, the rim hits the upper ball joint. Max you can go with a 15" rim is 4.75 backspace. Obviously 16" and larger diameter rims do not have this problem as they can clear the control arm and utilize greater backspace to better pull the tire into the fender.

So, with 4.75 backspace, I still have some room to the frame rails; 1.375" on the rear, 2.25" to the front. Since a longer-term goal is 19" rims with 315/30 tires, this means I will need 5.75" backspace or -6.35 offset on an 11" wheel. This should just clear the rear frame section with maybe a .030-.050 margin.  I think I can live with that.

Fender clearance with the big 15" combo is not happening. My engine is out so this whole set-up will sit one inch lower once the driveline is back in place and this is already with -1* camber. That puts this into interference territory. I have already rolled the fender lip so the only solution I would have with this tire is to flare the fender. You can see where the two potential interference points are. I could put a small pie wedge in each of these places to gain an extra .5-.75" of clearance and that might work. However, there is no one offering this size tire in 15" anymore, so not sure if I will bother.

The 315x19 I'm after is a skosh wider (by about .3" per side - 15" combo is 26" height by 12" wide, 19" combo will be 26" height by 12.6" wide) but further offset into the fender by an inch compared to this combo, so it might work without flaring. However, I have not cycled the tire up and down at extreme turning lock to verify if this will work. I do have the metal to perform the flare if needed in the future.

Also not readily apparent is that the front edge of the tire just clips the very front of the wheel opening. A slight cut back of this area will also be needed. Also note that while jackstands are visible under the car, it is actually sitting on the tire.

Out back, I have already relocated the spring in 1" and am using a '67 B body rear housing. This 15" tire and rim fit fine back there. With the 19" rim I may stick with the 5" backspace, maybe 5.5". I haven't rolled the lip back there yet so I have room to play around with.

[whitsend]

Offset is the outer hoop's centerline relative to the mounting pad's position on the hub. Backspace is the distance from the back of the rim to the mounting pad.

At a 30mm offset, those won't fit in the rear without moving the springs and/or using a spacer. Up front, that is going to put them really far inboard and the tire might rub the inner frame rail on extreme turn angles.  FWIW, 30mm offset on a 9" rim is a 6.18" backspace.  A -30mm offset on a 9" rim is 3.75" backspace. Like the Torque Thrust question above yours, that is also a questionable fit as well as it will put the tires further outboard. That's great for spring clearance, not so great for fender lip clearance.

If you want to dig into this further, they have a good explanation article on it here: https://www.discounttire.com/learn/offset-backspace?cjevent=ffe09803ed4611ef80e7025d0a1cb829&CJAID=13390473&CJPID=100357191&utm_source=customdigital&utm_medium=affiliate&utm_content=277774&utm_glid=DT_AFFILIATE_ALL_CDIG_ALL_LOGO

Here is an offset/backspace calculator:
https://tireswheelsdirect.com/wheel-offset-and-backspace-calculator/

Thanks very much for the information and links HP2. I appreciate you taking the time with the reply