Wheel Question - Forums - Official C3 Vette Registry - C3 Corvette Registry

Home page

☰

SPONSOR AD

Support our Vendors! | Advertise Here

Topic: Wheel Question

in Forum: C3 General Discussion

Already a Member?
Login
Not yet a Member?
Register for Free!

Hide Signatures

Wheel Question (1/48)
5/29/12 10:20am

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

I�ve been considering changing the wheels on my 82 and need input from this knowledgeable group. I know the backspacing on the stock wheel is 4 inches but I�m having difficulty finding exactly what Im looking for with a 4 inch backspace. I�m considering the wheels in the link below from Summitt but they are 3.75 inch backspace and an offset of -19.00mm. First of all, will these wheels work on our cars? How will that small difference in backspace affect the geometry of the rear suspension and handling? I am not interested in going with a larger tire than the stock 15 inch. I recently bought new tires and don�t plan on buying a new set for quite a while.

http://www.summitracing.com/parts/SUM-141-5861GM19/

|UPDATED|5/29/2012 7:20:10 AM (AZT)|/UPDATED|

Our Sponsors help support C3VR

Re: Wheel Question (2/48)
5/29/12 12:20pm

Lifetime Member

Lifetime Member
Send Private Message

Holland Patent, NY - USA

Vette(s):
#1 *1980 White, Red interior 14,000 mile #2 *1980 Red, Oyster interior 93,000 miles Resto project car, rebuilt to 383 stroker

Joined: 6/3/2008
Posts: 4421

Chip, those look real close to what Dick and Jill Countryman have on their vette...no?

Evil Smile

ebo

______________

Click on image for larger view!
LIFETIME MEMBER 151

ebo

Re: Wheel Question (3/48)
5/29/12 12:58pm

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

Yes, very similar but I think they are running 16 inch on theirs. This whole backspace and offset thing has me a bit puzzled Confused

Confused

.

Re: Wheel Question (4/48)
5/29/12 1:54pm

Lifetime Member

Lifetime Member
Send Private Message

Joined: 7/2/2006
Posts: 8205

This depicts offsets. An 8 inch wheel with a 4 inch backspace would then equal a zero offset due to the fact that it's centered. The wheel 3.75 backspace will actually be a negative 19mm. This would actually move the wheel/tire a 1/4" outward toward the fender lip. You probably have enough clearance for that.

______________

corvette440hp

Re: Wheel Question (5/48)
5/29/12 9:28pm

Lifetime Member

Lifetime Member
Send Private Message

Belvidere, IL - USA

Vette(s):
1977 Black T-Top ZZ4 5Sp 16in Wheels

Joined: 10/24/2004
Posts: 438

Hi Chip, 9 years ago when we redone the car. The 15 inch rims with 3.75 back space would hit the calibers.That was American Racing wheels, that's why I went with 16 inch for the 4 inch back space. Dick

Re: Wheel Question (6/48)
5/30/12 6:15am

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

Thanks for your replies guys. Dick, your information was especially useful. I think Ill just be keeping the stock wheels for now unless I can find some 15s with the proper backspace.

Re: Wheel Question (7/48)
5/30/12 12:03pm

Lifetime Member

Lifetime Member
Send Private Message

Manteca, CA - USA

Vette(s):
1978,two tone,Metalic Rootbeer & gold 1975 L48 4 speed

Joined: 11/20/2005
Posts: 3623

The last set of wheels I bought were from Les Schwab, American racing look alikes, 15x8 with a 3.75 back spacing. My concern was the leaf spring clearance and these wheels left me about 1/2" on each side w/ 255/60x15 tires.

|UPDATED|5/30/2012 9:03:30 AM (AZT)|/UPDATED|

______________

Jimmy B.
Just can't wait to get on the road again.

Click to see larger views!

Re: Wheel Question (8/48)
5/30/12 6:21pm

Lifetime Member

Lifetime Member
Moderator
Send Private Message

Burke, VT - USA

Vette(s):
SOLD - "The Toy" - '70 Convertible
SOLD - "The Beast" - '90 ZR-1 (#682)
SOLD - "Betty" - '28 Ford Model A Tudor
Still have - "BLKBRRD" - '78 Pontiac Trans Am

Joined: 1/23/2002
Posts: 7195

When I moved up to the 16" wheels on "The Toy" I needed to have some custom spacers made to get to the correct offset. Zen-Master Ken (kstyer) told me that as long as the wheel is centered the thickness of the spacer doesn't matter and it won't upset the suspension geometry. So if you really like the wheels a 1/4 inch spacer should be pretty easy to find.

______________

Jim Olson

"The Toys"...!!! Save the Wave!

Where I've been in a Corvette...!!!

Re: Wheel Question (9/48)
5/31/12 6:16am

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

Thanks guys, Im still looking at my options here and appreciate your input.

Re: Wheel Question (10/48)
6/4/12 2:09pm

JohnRR
Former Member
Send Private Message

Joined: 2/22/2011
Posts: 110

Hi All,

I'm new to this forum and have taken an interest in this thread. The discussion about backspacing and negative offset doesn't seem correct to me. If an 8" wheel has a 4" BS then it has a Zero offset. So if an 8" wheel has a 3.75 BS then it would have a negative 0.25 offset. That would be -6.35mm offset not -19mm. Am I missing something here?

Also, if the wheel has a 3.75 BS, a 1/4" spacer won't fix this. It would make the BS 3.5".

I'm trying to understand all this wheel terminology because I'm installing a set of C5 wheels on my '73.

Thanks everybody,

John

______________
1973 BB 4-Speed Coupe Project Car

2009 Z06 Mostly Stock

Re: Wheel Question (11/48)
6/4/12 5:31pm

Lifetime Member

Lifetime Member
Send Private Message

Joined: 7/2/2006
Posts: 8205

JohnRR said: Hi All,

I'm new to this forum and have taken an interest in this thread. The discussion about backspacing and negative offset doesn't seem correct to me. If an 8" wheel has a 4" BS then it has a Zero offset. So if an 8" wheel has a 3.75 BS then it would have a negative 0.25 offset. That would be -6.35mm offset not -19mm. Am I missing something here?

Also, if the wheel has a 3.75 BS, a 1/4" spacer won't fix this. It would make the BS 3.5".

I'm trying to understand all this wheel terminology because I'm installing a set of C5 wheels on my '73.

Thanks everybody,

John

John you are 100% correct. The 1/4" spacer would change things to the 3.5 inch mark and bring the wheel outward.

______________

corvette440hp

Re: Wheel Question (12/48)
6/4/12 5:42pm

Lifetime Member

Lifetime Member
Moderator
Send Private Message

Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 20133

JohnRR said:

I'm trying to understand all this wheel terminology because I'm installing a set of C5 wheels on my '73.

Thanks everybody,

John

Norsky has a set of C5 rims on his car...check his sig pic above. Thumbs Up

Thumbs Up

______________

Joel Adams
C3VR Lifetime Member #56
My Link

(click for Texas-sized view!) NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Re: Wheel Question (13/48)
6/4/12 6:31pm

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

Wheel update. With the information from you guys I decided to order one wheel for a test fit. It came in on Saturday evening and I tested it on front and back... IT FITS. I placed an order for the other 3 on Saturday night with Summit. Now Ive just got to wait for them to arrive and get my tires switched to the new wheels. Ill post some pics when they are on.

Re: Wheel Question (14/48)
6/4/12 6:34pm

Lifetime Member

Lifetime Member
Send Private Message

Joined: 7/2/2006
Posts: 8205

Crossfire1982 said: Wheel update. With the information from you guys I decided to order one wheel for a test fit. It came in on Saturday evening and I tested it on front and back... IT FITS. I placed an order for the other 3 on Saturday night with Summit. Now Ive just got to wait for them to arrive and get my tires switched to the new wheels. Ill post some pics when they are on.

Chip................THAT'S GREAT! You found out the REAL way.............or should I say the WHEEL way! Clap

Clap

______________

corvette440hp

Re: Wheel Question (15/48)
6/4/12 8:27pm

Almond81Vette
Former Member
Send Private Message

Stanley, NC - USA

Vette(s):
1981, dark blue w/carmel interior. 350 stock, auto tranny, Q-jet carb, ECM box

Joined: 8/9/2010
Posts: 91

That's great Chip, she will looked different now but good. Call if you need any help.

______________
Tommy

Re: Wheel Question (16/48)
6/5/12 10:03pm

Lifetime Member

Lifetime Member
Moderator
Send Private Message

Burke, VT - USA

Vette(s):
SOLD - "The Toy" - '70 Convertible
SOLD - "The Beast" - '90 ZR-1 (#682)
SOLD - "Betty" - '28 Ford Model A Tudor
Still have - "BLKBRRD" - '78 Pontiac Trans Am

Joined: 1/23/2002
Posts: 7195

Adams' Apple said:
Norsky has a set of C5 rims on his car...check his sig pic above. Thumbs Up

Thumbs Up

They actually are C4/Camaro A-Mold look-a-likes. Here's a better peek at them: https://www.c3vr.com/member_pages/401_500/419/TheToyAtBG_lg.JPG

______________

Jim Olson

"The Toys"...!!! Save the Wave!

Where I've been in a Corvette...!!!

Re: Wheel Question (17/48)
6/6/12 6:14am

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

Thanks Tommy, I appreciate the offer. Ill see you at the Tilted Kilt Sunday if not before.

Re: Wheel Question (18/48)
6/6/12 8:44pm

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

OK, I got the tires mounted and the wheels on the vette, Im pleased with the new look.

http://i139.photobucket.com/albums/q307/crossfire1982/DSC08506.jpg

http://i139.photobucket.com/albums/q307/crossfire1982/DSC08509.jpg

Re: Wheel Question (19/48)
6/6/12 8:52pm

Lifetime Member

Lifetime Member
Send Private Message

Holland Patent, NY - USA

Vette(s):
#1 *1980 White, Red interior 14,000 mile #2 *1980 Red, Oyster interior 93,000 miles Resto project car, rebuilt to 383 stroker

Joined: 6/3/2008
Posts: 4421

Chip, I love em!

Narley retro look! I had a set of those on the front of my 69 cuda fastback Formula S They were Keystones.

Evil Smile

ebo

______________

Click on image for larger view!
LIFETIME MEMBER 151

ebo

Re: Wheel Question (20/48)
6/6/12 9:21pm

Lifetime Member

Lifetime Member
Send Private Message

Wichita, KS - USA

Vette(s):
2005 Daytona Sunset Orange Metallic Coupe --------------------- Sold 1974 T-top, 4 spd to BillKS

Joined: 11/10/2003
Posts: 6859

Lookin' good, Chip. Cool

Cool

I like the look of those retro-style wheels on a C3. Too bad you didn't have them on when we were in Charleston. Would have been great to see them in person. Thumbs Up

Thumbs Up

Larry

______________

C3VR Lifetime Member #102
My Link.........

The difference between men and boys is the cost of their toys!!

Re: Wheel Question (21/48)
6/6/12 10:32pm

JohnRR
Former Member
Send Private Message

Joined: 2/22/2011
Posts: 110

The new wheels and tires look great, but the black paint is spectacular!

______________
1973 BB 4-Speed Coupe Project Car

2009 Z06 Mostly Stock

Re: Wheel Question (22/48)
6/6/12 10:38pm

Lifetime Member

Lifetime Member
Send Private Message

Manteca, CA - USA

Vette(s):
1978,two tone,Metalic Rootbeer & gold 1975 L48 4 speed

Joined: 11/20/2005
Posts: 3623

AAAWWWW HECK YEAH ! SWEEEET !

______________

Jimmy B.
Just can't wait to get on the road again.

Click to see larger views!

Re: Wheel Question (23/48)
6/6/12 11:27pm

Lifetime Member

Lifetime Member
Send Private Message

Belvidere, IL - USA

Vette(s):
1977 Black T-Top ZZ4 5Sp 16in Wheels

Joined: 10/24/2004
Posts: 438

I like, your car looks great Chip!

Re: Wheel Question (24/48)
6/7/12 1:56am

daveo76
Former Member
Send Private Message

Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Joined: 8/25/2005
Posts: 857

Those look pretty cool - nice! I've always been a fan of the stockers (rallies, aluminum, even the turbines from '82 CE) but if I was going to switch to an aftermarket wheel I'd be pretty interested in those. Wonder if any of the vendors will ever consider making a rally or aluminum replica in a 16 or 17" version??? That might be kinda cool....

______________

1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Re: Wheel Question (25/48)
6/7/12 6:09am

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

Thanks for the comments guys I appreciate the compliments on the wheels and the paint. Dave, those same wheels are available in 16s I know and I believe 17 as well if that is what you are looking for. Dick, I can thank you... or blame you for making me spend the $$ for the new wheels. When I saw your wheels I had to have something like them, yours look great

|UPDATED|6/7/2012 3:09:01 AM (AZT)|/UPDATED|

Re: Wheel Question (26/48)
6/7/12 8:44am

Lifetime Member

Lifetime Member
Send Private Message

Joined: 7/2/2006
Posts: 8205

Chip..........................very HOT! Thumbs Up

Thumbs Up

______________

corvette440hp

Re: Wheel Question (27/48)
6/7/12 8:57am

Lifetime Member

Lifetime Member
Send Private Message

Sykesville, MD - USA

Vette(s):
1979 Corvette Coupe Corvette Light Blue Midnight Blue interior Mirrored Glass T-tops

Joined: 4/27/2008
Posts: 4238

the new wheels look GREAT, Chip! I know it's off topic, but how's the wife? I remember you guys left Charleston early because she wasn't feeling well. Hope all is OK.

Barry

Thumbs Up

______________
"Down on the Boardwalk...

(Click image to see a larger version}

Lifetime Member #181

Re: Wheel Question (28/48)
6/7/12 9:02am

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

Barry, it took her a couple days but she is now doing great. We hated to leave early, we wre really looking forward to the Savannah tour. Thanks for asking.

Re: Wheel Question (29/48)
6/7/12 12:15pm

Lifetime Member

Lifetime Member
Moderator
Send Private Message

Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 20133

Yeah, Baby...YEAH!!! Clap

Clap

Cool

Now thass old skool, right thar!! Thumbs Up

Thumbs Up

______________

Joel Adams
C3VR Lifetime Member #56
My Link

(click for Texas-sized view!) NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Re: Wheel Question (30/48)
6/7/12 2:56pm

Lifetime Member

Lifetime Member
Send Private Message

COPPERAS COVE, TX - USA

Vette(s):
1972 corvette stingray convertible 2007 coupe

Joined: 7/6/2002
Posts: 417

Those look nice on that black beauty!! I was looking at the same ones on fleabay.

http://www.ebay.com/itm/Corvette-Wheels-Tires-17x8-255-50VR17-Classic-Rims-C3-1968-82-1972-1973-1794-/300721051897?pt=Motors_Car_Truck_Parts_Accessories&hash=item46045f18f9&vxp=mtr

much bigger than yours but I like those wheels.

______________

Click for larger view

Re: Wheel Question (31/48)
6/7/12 3:19pm

daveo76
Former Member
Send Private Message

Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Joined: 8/25/2005
Posts: 857

Chip, no what I was talking about is a replica of a stock wheel (rally or YJ8 aluminum) but in 16" or 17". So it would look just like stock, but be sized to fit more modern, advanced tires. I don't think I've ever seen or heard of anything like that, but maybe some of the bigger vendors would consider it someday....

______________

1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Re: Wheel Question (32/48)
6/7/12 4:47pm

Lifetime Member

Lifetime Member
Send Private Message

Joined: 7/2/2006
Posts: 8205

fp_vetter72 said: Those look nice on that black beauty!! I was looking at the same ones on fleabay.

http://www.ebay.com/itm/Corvette-Wheels-Tires-17x8-255-50VR17-Classic-Rims-C3-1968-82-1972-1973-1794-/300721051897?pt=Motors_Car_Truck_Parts_Accessories&hash=item46045f18f9&vxp=mtr

much bigger than yours but I like those wheels.

Those really shoud fit. I did the math on the 120.65.............and yep in comes out to 4.75 inches for the bolt pattern. The offset is 0 so that means it's 4 inches which equates to the center for an 8 inch wheel. The outside diameter is 27.1..........perfect. You know they will clear your calipers being 17". The brake line can be moved if neccessary. Go for it! Thumbs Up

Thumbs Up

______________

corvette440hp

Re: Wheel Question (33/48)
6/7/12 7:07pm

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

Dave, sorry I misunderstood. Somewhere a while back I saw some discussion on large diameter rally wheels. Ill see if I an locate it and shoot you a PM if I do.

Re: Wheel Question (34/48)
6/9/12 12:52pm

Lifetime Member

Lifetime Member
Moderator
Send Private Message

CUYAHOGA FALLS, OH - USA

Vette(s):
1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!

Joined: 12/2/2003
Posts: 6424

Everyone except Corvette 440, Larry, is missing a measurement factor.

Offset is measured from the center of the rim. The surface of the back of the rim where it meets the hub is the measuring point. If an 8 in rim has this surface at mid point of 4 inches across, there is NO offset.

Offset is then measured in how many inches is from this center point. There is another HUGE factor. There is both Positive and Negative offset. Remember year ago we had Chrome Reverse wheels that stuck way out? Those has a severe negative offset, sometimes refered to as reverse. If more of the rim tucks under the wheel well, it is a positive offset.

Many often refer to the distance from the back of the rim to the center or the mounting point as the offset. Not true, but a common mistake even in some advertising. Most rims are actually a positive offset, bringing the wheel inward (and hitting the calipers)

If the rims were measured from the back that would change the offset simply by putting on wider rims. But measured from center, the backset is always the same measurement dispite rim width. This makes a consist industery measurement, where the other method is not only wrong, but inconsistant.

A spacer corrects a negative offset, but makes a positive offset much worse.

The 8 inch example has 4 inch measurement from the back, it is a 0 offset. a 10 inch rim would need 5 inches from the rear to have a 0 offset. Either way the tire tread center point would be the same, which affects scrub radius, another very important measurement that affect handling. Total outer dia. of the tire also affects scrub radius. Larger rims with narrower sidewalls can maintain proper tire dia.

If meassured the way most have indicated, say 4 inches from the rear of the rim, that is a 0 on a 8 inch, but 1/2 neg offset on a 9 inch rim ( center point 4.5 in.), and 1 inch negative offset on a 10 inch rim (center point at 5 in. )

Hope this clears this up.

|UPDATED|6/9/2012 9:52:37 AM (AZT)|/UPDATED|

Re: Wheel Question (35/48)
6/9/12 6:13pm

Lifetime Member

Lifetime Member
Send Private Message

Joined: 7/2/2006
Posts: 8205

kstyer said:

Everyone except Corvette 440, Larry, is missing a measurement factor.

Offset is measured from the center of the rim. The surface of the back of the rim where it meets the hub is the measuring point. If an 8 in rim has this surface at mid point of 4 inches across, there is NO offset.

Offset is then measured in how many inches is from this center point. There is another HUGE factor. There is both Positive and Negative offset. Remember year ago we had Chrome Reverse wheels that stuck way out? Those has a severe negative offset, sometimes refered to as reverse. If more of the rim tucks under the wheel well, it is a positive offset.

Many often refer to the distance from the back of the rim to the center or the mounting point as the offset. Not true, but a common mistake even in some advertising. Most rims are actually a positive offset, bringing the wheel inward (and hitting the calipers)

If the rims were measured from the back that would change the offset simply by putting on wider rims. But measured from center, the backset is always the same measurement dispite rim width. This makes a consist industery measurement, where the other method is not only wrong, but inconsistant.

A spacer corrects a negative offset, but makes a positive offset much worse.

The 8 inch example has 4 inch measurement from the back, it is a 0 offset. a 10 inch rim would need 5 inches from the rear to have a 0 offset. Either way the tire tread center point would be the same, which affects scrub radius, another very important measurement that affect handling. Total outer dia. of the tire also affects scrub radius. Larger rims with narrower sidewalls can maintain proper tire dia.

If meassured the way most have indicated, say 4 inches from the rear of the rim, that is a 0 on a 8 inch, but 1/2 neg offset on a 9 inch rim ( center point 4.5 in.), and 1 inch negative offset on a 10 inch rim (center point at 5 in. )

Hope this clears this up.

Thanks Ken, at least someone understands me Thumbs Up

Thumbs Up

Much more importantly......GLAD TO SEE YOU BACK (Hope you and family are well) I know OFF TOPIC!

______________

corvette440hp

Re: Wheel Question (36/48)
6/11/12 12:35pm

Lifetime Member

Lifetime Member
C3VR Founder
Online Now! - Send Private Message

Eagleville, PA - USA

Vette(s):
Used to own a 1979 Corvette now owned by JB79

Joined: 11/1/2001
Posts: 17658

kstyer said:

Everyone except Corvette 440, Larry, is missing a measurement factor.

Offset is measured from the center of the rim. The surface of the back of the rim where it meets the hub is the measuring point. If an 8 in rim has this surface at mid point of 4 inches across, there is NO offset.

Offset is then measured in how many inches is from this center point. There is another HUGE factor. There is both Positive and Negative offset. Remember year ago we had Chrome Reverse wheels that stuck way out? Those has a severe negative offset, sometimes refered to as reverse. If more of the rim tucks under the wheel well, it is a positive offset.

Many often refer to the distance from the back of the rim to the center or the mounting point as the offset. Not true, but a common mistake even in some advertising. Most rims are actually a positive offset, bringing the wheel inward (and hitting the calipers)

If the rims were measured from the back that would change the offset simply by putting on wider rims. But measured from center, the backset is always the same measurement dispite rim width. This makes a consist industery measurement, where the other method is not only wrong, but inconsistant.

A spacer corrects a negative offset, but makes a positive offset much worse.

The 8 inch example has 4 inch measurement from the back, it is a 0 offset. a 10 inch rim would need 5 inches from the rear to have a 0 offset. Either way the tire tread center point would be the same, which affects scrub radius, another very important measurement that affect handling. Total outer dia. of the tire also affects scrub radius. Larger rims with narrower sidewalls can maintain proper tire dia.

If meassured the way most have indicated, say 4 inches from the rear of the rim, that is a 0 on a 8 inch, but 1/2 neg offset on a 9 inch rim ( center point 4.5 in.), and 1 inch negative offset on a 10 inch rim (center point at 5 in. )

Hope this clears this up.

I don't want to get off topic, just need to say...
This is why we miss having you, Ken, around "full time!"

______________

-Adam Wartell
NCM Lifetime Member #1222
Founder: C3 Vette Registry
C4 Vette Registry, C6 Vette Registry

My first Vette, now owned by JB79:

Re: Wheel Question (37/48)
6/13/12 9:41am

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

A follow up on Daveo76's question about large size rally wheels I found these at Summit. There are also others available by a company called Wheel Vintiques but they AINT CHEAP.

http://www.summitracing.com/search/Product-Line/Wheel-Vintiques-66-Series-Chevy-Style-Rallye-Silver-Wheels/

Re: Wheel Question (38/48)
6/13/12 8:00pm

kwoody
Former Member
Send Private Message

Tucson, AZ - USA

Vette(s):
1982 Black/Tan Leather Build Code C09E Bronze TTop CrossFire Fuel Injection L83 85 Fuel Pump Auto Axle 2.72 Firestone Firehawk Indy500

Joined: 7/11/2010
Posts: 415

Hi Chip,

I like what you've done with the wheels. It did take me a while to get my head
around the new look though. I also like the highlight on the gills and the side trim.

Lookin' Good!

Keith

______________

Nobody ever waves when I'm driving the Explorer.
K Woody

Re: Wheel Question (39/48)
6/14/12 7:37am

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

Thanks Keith

Re: Wheel Question (40/48)
6/28/12 12:57pm

73shark
Limited Member
Send Private Message

Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 867

JohnRR said: Hi All,

I'm new to this forum and have taken an interest in this thread. The discussion about backspacing and negative offset doesn't seem correct to me. If an 8" wheel has a 4" BS then it has a Zero offset. So if an 8" wheel has a 3.75 BS then it would have a negative 0.25 offset. That would be -6.35mm offset not -19mm. Am I missing something here?

Also, if the wheel has a 3.75 BS, a 1/4" spacer won't fix this. It would make the BS 3.5".

I'm trying to understand all this wheel terminology because I'm installing a set of C5 wheels on my '73.

Thanks everybody,

John

Came up w/ the same conclusion when I did the math. Suspect the -19 mm is an error since the rest is in inches. Handshake

Handshake

Beware of spacers as they increase the load on wheel bearings and the studs. Shocked

Shocked

Nice looking wheels. I believe they're what we called Cragar mags back in the 60s. Thumbs Up

Thumbs Up

|UPDATED|6/28/2012 9:57:19 AM (AZT)|/UPDATED|

______________

1973 L-82 4 spd

Re: Wheel Question (41/48)
6/29/12 12:05pm

JohnRR
Former Member
Send Private Message

Joined: 2/22/2011
Posts: 110

Beware of spacers as they increase the load on wheel bearings and the studs

I don't believe this is true. I'm keeping the centerline of the wheel the same as stock or about 1/8" inboard. So I'm not poking the wheels out any further than stock.

John

______________
1973 BB 4-Speed Coupe Project Car

2009 Z06 Mostly Stock

Re: Wheel Question (42/48)
6/29/12 11:15pm

Lifetime Member

Lifetime Member
Send Private Message

Red Lion, PA - USA

Vette(s):
1974 White 350 Corvette, TH400 Automatic 1972 Tangerine /Go Mango Convertible 383 Stroker, 2004r Automatic

Joined: 10/27/2006
Posts: 1182

Ive been running 1/2" spacers on the cragers I have on the 74 for about 2 years now. I have had no issues to this point. In theory I would understand the reasoning of more load on the bearing because you have moved the bolting point out away from the bearing itself. However I dont think that will make a lot of increase load that it would cause short term issues. Maybe over a 20 year period but I'll find that out down the road. The trade off to have cragers is worth it! lol.

Chip the wheels look fantastic! The paint looks great! Hope to meet you at some point.
Best of luck,
Rodney Hake

______________

Re: Wheel Question (43/48)
6/30/12 10:41am

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

Thanks Rodney, I appreciate the comment. This thread sure generated more interest and replies than I expected.

Re: Wheel Question (44/48)
7/1/12 10:49pm

73shark
Limited Member
Send Private Message

Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 867

JohnRR said: Beware of spacers as they increase the load on wheel bearings and the studs

I don't believe this is true. I'm keeping the centerline of the wheel the same as stock or about 1/8" inboard. So I'm not poking the wheels out any further than stock.

John

Here's a good discussion.

http://forums.corvetteforum.com/c4-tech-performance/2676505-wheel-spacers-good-or-bad-idea.html

Here's some hubcentric adapters even tho they call them spacers.

http://www.tunersdepot.com/Jsp/content/H-R--DRM-Series-Trak--Wheel-Spacer-45mm--Pair----90-96-Chevy-Corvette-37917.html

______________

1973 L-82 4 spd

Re: Wheel Question (45/48)
7/2/12 4:52am

Lifetime Member

Lifetime Member
Send Private Message

Indianapolis, IN - USA

Vette(s):
Silver 1974 Convertible - L82 4 speed Low miles (was only 8,900 when I bought it in March 2006) - Now 54K miles. Original owner bought it as an investment for son's college expenses. 2008 Jetstream Blue Convertible

Joined: 9/3/2006
Posts: 2423

Really like the look Chip. Well done

______________

I wanted a Corvette my whole life, but I never dreamed of all the wonderful people I would meet because of it!

��

States Visited Map

target=_blank>Click for another pic!�� And yet another!

Re: Wheel Question (46/48)
7/3/12 8:09pm

JohnRR
Former Member
Send Private Message

Joined: 2/22/2011
Posts: 110

Hey Shark,

Thanks for the link. I read the thread and it mostly discusses the differences between spacers and adapters.

When I was at Corvettes at Carlisle last year, one of the vendors gave me a hard time about using wheel adapters to mate C5 wheels to my '73 spindles. I believe that when the wheel mounting face is kept at the centerline of the wheel, the load on the spindle bearings is the same. The stock wheel is 8" wide with a 4" backspace. The 8.5" wide C5 wheels, with a 2.75" adapter has a backspace of 4.25". I think they are both the same as far as the load on the wheel bearing is concerned.

John

______________
1973 BB 4-Speed Coupe Project Car

2009 Z06 Mostly Stock

Re: Wheel Question (47/48)
7/3/12 8:53pm

crossfire1982
Former Member
Send Private Message

Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094

Thanks Marshall. I had looked at these wheels before but after seeing Dick's vette at the Charleston gathering I decided to bite the bullet and try them.

Re: Wheel Question (48/48)
7/4/12 7:46pm

Lifetime Member

Lifetime Member
Send Private Message

Sykesville, MD - USA

Vette(s):
1979 Corvette Coupe Corvette Light Blue Midnight Blue interior Mirrored Glass T-tops

Joined: 4/27/2008
Posts: 4238

Hey, Chip! You gotta change your signature pic now with the new wheels!

Barry

Wink

______________
"Down on the Boardwalk...

(Click image to see a larger version}

Lifetime Member #181

Our Sponsors help support C3VR