47-55.1 Explorer rear and wheel backspace question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**caseyjones** · 11-23-2018, 03:05 PM

Question for the crew since I can't get to my truck and I need to order some parts. On my 55.1, I am using the Explorer disc brake rear end and I have 16x8 wheels with 4.75" backspace. If I'm doing my math and my research right, a 1" spacer or adapter will put the wheels right where they need to be. Can anyone confirm? Thanks in advance.

**jweb** · 11-23-2018, 04:10 PM

It would really be best to measure. Your tire size could be different than someone else's.
I have an explorer axle, 20x8.5" wheels and use 1" adapters. It leaves a 1/2" of clearance on either side of the tire.

I would also highly recommend using hub centric adapters. You can get them custom made to fit the axle and the bore of your wheels.
https://www.uswheeladapters.com/

**caseyjones** · 11-23-2018, 09:07 PM

Quote:

Originally Posted by jweb

It would really be best to measure. Your tire size could be different than someone else's.
I have an explorer axle, 20x8.5" wheels and use 1" adapters. It leaves a 1/2" of clearance on either side of the tire.

I would also highly recommend using hub centric adapters. You can get them custom made to fit the axle and the bore of your wheels.
https://www.uswheeladapters.com/

What is the backspace on your wheels?
Posted via Mobile Device

**jweb** · 11-23-2018, 09:28 PM

Quote:

Originally Posted by caseyjones

What is the backspace on your wheels?
Posted via Mobile Device

I'm not 100% sure, I bought them over 10 years ago. I think they're 4.75"

65blackfleetside · 11-24-2018, 09:32 AM

I am not sure what my back spacing is I bought my set of boss rims used but they are 18" in front and 20"s in rear backs look to be at least 8" wide. I am running an S10 frame and 97 Explorer 8.8 Rear with disks + explorer emergency brake etc. Fit like a glove. No spacers needed. Unless your backspacing is custom- You should be fine.(I did have to run billet aluminum spacers up front)

65blackfleetside · 11-24-2018, 10:01 AM

Sorry that was 8 chapters ago on my build- I did actuall have a rear tire rub problem with the 8.8. As a result I installed mini tubs. Purchased smallest Northern tool $40 trailer fender. rip in half with cut off wheel. min tubs 3" wide. Looks factory. ( Notch bed sheet metal behind mini tub.)

I did not want to run the spacers in rear due to added bearing stress. I know others do but thats just me)

**caseyjones** · 11-24-2018, 09:43 PM

Thanks guys. I'm still looking for folks that know their wheel width and backspace, and can confirm spacer width...and used the explorer disc brake rear. I'd love to go out and measure my truck, but it's stashed in the back of my dad's shop in S.D. and i'm in OR...

whitedog76 · 11-25-2018, 12:34 AM

Currently, I have 6.5” wide rims with 4.25 backspace on my 54. I still have the stock axle, which is around 62”. Anyhow, the wheels are about as centered as it gets in the wheelwell.

With that said, I’m thinking you would want a 4” but no more than 4.5” backspace wheel. Of course it all depends on the tire and over all width of rim you’re using.

**mr48chev** · 11-25-2018, 01:47 PM

Some times you have to sneak over to the other side of the road to find info. Checking over on the Ranger Station shows that the Explorer 8.8 is 59.5 inches wheel mount to wheel mount. It gives other info on the rear that one may or may not need too. https://www.therangerstation.com/tec...lorer8_8.shtml

The stock bed is 50 inches inside or about 50-1/8 on the outside Personal experience says 1/2 inch clearance isn't near enough.

59.5 minus 9 for a 4.5 back space leaves your rims less than 1/2 inch from the bed sides with no tires.

You can play with this chart and figure out what the width of a tire should be on a certain width rim https://tiresize.com/tiresizes/265-45R20.htm You have to plug in your correct size but it is a handy tool for what you are trying to do.

I'm not a fan of spacers but the ones that Jweb suggested are the way I would go. They seem to do a lot with the pro touring brigade and a few searches lead me to them almost every time.

**caseyjones** · 11-25-2018, 02:25 PM

One piece missing...what’s the width from bedside to inside fender lip? I want to make sure I’m not pushing the wheel too far out. Based on another’s experience, using an Explorer rear, 8” rear wheel with 235 wide tire, 4” backspace and 5/16” spacer got him where he wanted it...so accounting for the extra backspace on my wheels, a 1” spacer will pull the wheel in only 1/8” per side...good enough for me. Now I’m looking for some real world confirmation...maybe even photo evidence...
Posted via Mobile Device

**caseyjones** · 01-02-2019, 01:43 AM

I've been able to confirm that my 1955.1 truck will require 1.5" spacers to put the 8" wide, 4.75" backspace wheels centered in the rear fender wells. should be roughly 1.5" of clearance from outside of rim on each side.

Black93GT · 01-02-2019, 04:33 PM

I used an explorer rear with 20x8's and zero offset. The overall wheel width is about 9" so I have approximately 4.5" backspace. I have around 1" gap between the tightest part of the fender and my 245/40-20's.

dsraven · 01-03-2019, 11:48 AM

the best thing you could do is actually do a hands on measurement on the truck and a quick sketch as you go. ensure to leave room for some tire flex and suspension movement-side to side- as you go around corners, do burnouts etc

-box width, as if no fenders were bolted on, outside to outside at the wheels, include any bumps or contours at it's widest point where the tires will be
-dimension from lip inside rear fender to the box wall-both sides at the narrowest point
-dimension from wheel mounting surface to box wall-both sides
-check to ensure the truck is the same from one side to the other
-dimension of total tire width at the widest spot
-dimension from wheel mounting surface of rim to the outside of the tire on the back side. lay the tire/wheel down on it's back side, on a flat hard surface, and then measure from the wheel mounting surface to the floor
-dimension from wheel mounting surface of rim to the outside of the tire on the front side. same as above but with the wheel now sitting on it's front side

insert all the dimensions into your sketch and do the math. easy and accurate for YOUR truck with YOUR wheels and YOUR fenders. not everything is the same from truck to truck on these things. don't forget you may need some longer wheel studs if using spacers.now would be a great time to change the wheel stud pattern too, if you haven't done that yet.

11-23-2018, 03:05 PM	#1
caseyjones Senior Member Join Date: Nov 2013 Location: Portland, OR Posts: 555	Explorer rear and wheel backspace question Question for the crew since I can't get to my truck and I need to order some parts. On my 55.1, I am using the Explorer disc brake rear end and I have 16x8 wheels with 4.75" backspace. If I'm doing my math and my research right, a 1" spacer or adapter will put the wheels right where they need to be. Can anyone confirm? Thanks in advance. __________________ 1955 Long Distance Build 1964 GMC Palomino Tan Survivor 1964 C10 Survivor - Sold

11-23-2018, 04:10 PM	#2
jweb Senior Member Join Date: Apr 2010 Location: Oregon Posts: 1,208	Re: Explorer rear and wheel backspace question It would really be best to measure. Your tire size could be different than someone else's. I have an explorer axle, 20x8.5" wheels and use 1" adapters. It leaves a 1/2" of clearance on either side of the tire. I would also highly recommend using hub centric adapters. You can get them custom made to fit the axle and the bore of your wheels. https://www.uswheeladapters.com/ __________________ 1951 Truck, LS1/4L60 1964 Suburban, current project 2014 Silverado daily driver 1953 Westerner "canned ham" trailer, rebuilt 1974 Prowler trailer, rebuilt

11-24-2018, 09:32 AM	#5
65blackfleetside Registered User Join Date: Nov 2015 Location: Central Florida Posts: 215	Re: Explorer rear and wheel backspace question I am not sure what my back spacing is I bought my set of boss rims used but they are 18" in front and 20"s in rear backs look to be at least 8" wide. I am running an S10 frame and 97 Explorer 8.8 Rear with disks + explorer emergency brake etc. Fit like a glove. No spacers needed. Unless your backspacing is custom- You should be fine.(I did have to run billet aluminum spacers up front) __________________ current ride 1951 AD Chevy 5 window 2004 LS Gen 3 [/B] 1965 fleetside Sold

11-24-2018, 10:01 AM	#6
65blackfleetside Registered User Join Date: Nov 2015 Location: Central Florida Posts: 215	Re: Explorer rear and wheel backspace question Sorry that was 8 chapters ago on my build- I did actuall have a rear tire rub problem with the 8.8. As a result I installed mini tubs. Purchased smallest Northern tool $40 trailer fender. rip in half with cut off wheel. min tubs 3" wide. Looks factory. ( Notch bed sheet metal behind mini tub.) I did not want to run the spacers in rear due to added bearing stress. I know others do but thats just me) __________________ current ride 1951 AD Chevy 5 window 2004 LS Gen 3 [/B] 1965 fleetside Sold

11-24-2018, 09:43 PM	#7
caseyjones Senior Member Join Date: Nov 2013 Location: Portland, OR Posts: 555	Re: Explorer rear and wheel backspace question Thanks guys. I'm still looking for folks that know their wheel width and backspace, and can confirm spacer width...and used the explorer disc brake rear. I'd love to go out and measure my truck, but it's stashed in the back of my dad's shop in S.D. and i'm in OR... __________________ 1955 Long Distance Build 1964 GMC Palomino Tan Survivor 1964 C10 Survivor - Sold

11-25-2018, 12:34 AM	#8
whitedog76 Registered User Join Date: Jan 2014 Location: Peoria, IL Posts: 1,450	Re: Explorer rear and wheel backspace question Currently, I have 6.5” wide rims with 4.25 backspace on my 54. I still have the stock axle, which is around 62”. Anyhow, the wheels are about as centered as it gets in the wheelwell. With that said, I’m thinking you would want a 4” but no more than 4.5” backspace wheel. Of course it all depends on the tire and over all width of rim you’re using.

11-25-2018, 01:47 PM	#9
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,711	Re: Explorer rear and wheel backspace question Some times you have to sneak over to the other side of the road to find info. Checking over on the Ranger Station shows that the Explorer 8.8 is 59.5 inches wheel mount to wheel mount. It gives other info on the rear that one may or may not need too. https://www.therangerstation.com/tec...lorer8_8.shtml The stock bed is 50 inches inside or about 50-1/8 on the outside Personal experience says 1/2 inch clearance isn't near enough. 59.5 minus 9 for a 4.5 back space leaves your rims less than 1/2 inch from the bed sides with no tires. You can play with this chart and figure out what the width of a tire should be on a certain width rim https://tiresize.com/tiresizes/265-45R20.htm You have to plug in your correct size but it is a handy tool for what you are trying to do. I'm not a fan of spacers but the ones that Jweb suggested are the way I would go. They seem to do a lot with the pro touring brigade and a few searches lead me to them almost every time. __________________ Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.

11-25-2018, 02:25 PM	#10
caseyjones Senior Member Join Date: Nov 2013 Location: Portland, OR Posts: 555	Re: Explorer rear and wheel backspace question One piece missing...what’s the width from bedside to inside fender lip? I want to make sure I’m not pushing the wheel too far out. Based on another’s experience, using an Explorer rear, 8” rear wheel with 235 wide tire, 4” backspace and 5/16” spacer got him where he wanted it...so accounting for the extra backspace on my wheels, a 1” spacer will pull the wheel in only 1/8” per side...good enough for me. Now I’m looking for some real world confirmation...maybe even photo evidence... Posted via Mobile Device

01-02-2019, 01:43 AM	#11
caseyjones Senior Member Join Date: Nov 2013 Location: Portland, OR Posts: 555	Re: Explorer rear and wheel backspace question I've been able to confirm that my 1955.1 truck will require 1.5" spacers to put the 8" wide, 4.75" backspace wheels centered in the rear fender wells. should be roughly 1.5" of clearance from outside of rim on each side. __________________ 1955 Long Distance Build 1964 GMC Palomino Tan Survivor 1964 C10 Survivor - Sold

01-02-2019, 04:33 PM	#12
Black93GT Registered User Join Date: Aug 2014 Location: Vacaville, CA Posts: 133	Re: Explorer rear and wheel backspace question I used an explorer rear with 20x8's and zero offset. The overall wheel width is about 9" so I have approximately 4.5" backspace. I have around 1" gap between the tightest part of the fender and my 245/40-20's. __________________ '49 3600 build SBC 350, a T-5 and some patina

01-03-2019, 11:48 AM	#13
dsraven Registered User Join Date: Nov 2010 Location: calgary alberta Posts: 8,334	Re: Explorer rear and wheel backspace question the best thing you could do is actually do a hands on measurement on the truck and a quick sketch as you go. ensure to leave room for some tire flex and suspension movement-side to side- as you go around corners, do burnouts etc -box width, as if no fenders were bolted on, outside to outside at the wheels, include any bumps or contours at it's widest point where the tires will be -dimension from lip inside rear fender to the box wall-both sides at the narrowest point -dimension from wheel mounting surface to box wall-both sides -check to ensure the truck is the same from one side to the other -dimension of total tire width at the widest spot -dimension from wheel mounting surface of rim to the outside of the tire on the back side. lay the tire/wheel down on it's back side, on a flat hard surface, and then measure from the wheel mounting surface to the floor -dimension from wheel mounting surface of rim to the outside of the tire on the front side. same as above but with the wheel now sitting on it's front side insert all the dimensions into your sketch and do the math. easy and accurate for YOUR truck with YOUR wheels and YOUR fenders. not everything is the same from truck to truck on these things. don't forget you may need some longer wheel studs if using spacers.now would be a great time to change the wheel stud pattern too, if you haven't done that yet.



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