Wider in the back?

S

Sky65

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Aug 27, 2008
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Maryland
I want to change the wheels/tires on the 65 and I am looking for some info. I have VBP suspension, Steeroids R&P, Richmond 5 spd, SB. I am going to 17" to get some more modern rubber. I like the look of wider wheels/tires on the rear but how does that affect handling? The car is driver and do like to throw it around a little. Any real benefit to wider rears? Benefits to same size front and rear?

Thanks
Tom
 
I assume you're running 15" tires now. Upgrading to modern 17" will be a huge improvement. They stopped developing/improving this size tire design back in the 80's.
With wider rear tires you'll see a little more understeering in extreme situations because the rears have more grip. Are you going to push the car that far ? Most likely not.... It does look great so i say go for it.
You're saying 17" so I assume 8X17 rim with 255-50-17 front and 9.5X17 rim with 275-50-17 rear ??
You will not be able to rotate the tires, how many miles do you drive per year ??
 
I'm running 255/60 X 15 all around right now. The car has small flares and I put on offset rear t-arms when I rebuilt the bearing assemblies, just in case. I drive the car all year as much as I can but weekends only. I have company car I use during the week but I use the 65 for everything else. I take long weekend trips a couple times a year.

Tire size for the rear is the other problem. I like the 27" diameter of the 255/60 on the car now. 255/50 17 on an 8" wheel is good for the front but I can't find a rear tire 17" diameter for a 9 or 9 1/2 wheel. Tire Rack does not show a 275/50 17?
 
ONE of the very first things I did to my '72, some 15 years ago was of course a complete suspension rebuild, and putting 17x9.5 '92 vette rims all around....

255/50/17 in front....Scorcher t/a....rear is NITTO 275/50/17......

I used VBP wheel 2.5 inch wheel adapters.....

:hi:
 
mrvette said:
ONE of the very first things I did to my '72, some 15 years ago was of course a complete suspension rebuild, and putting 17x9.5 '92 vette rims all around....

255/50/17 in front....Scorcher t/a....rear is NITTO 275/50/17......

I used VBP wheel 2.5 inch wheel adapters.....

:hi:
Click to expand...
What is the backspacing using the 2.5" spacers?
Thanks
 
Sky65 said:
mrvette said:
ONE of the very first things I did to my '72, some 15 years ago was of course a complete suspension rebuild, and putting 17x9.5 '92 vette rims all around....

255/50/17 in front....Scorcher t/a....rear is NITTO 275/50/17......

I used VBP wheel 2.5 inch wheel adapters.....

:hi:
Click to expand...
What is the backspacing using the 2.5" spacers?
Thanks
Click to expand...

Same as a stock shark rim....I kept the same centerline to minimize the bearling loading at speed......move the ebrake to allow wider tires if you have a rear sway bar keeping the same centerline will make the same clearance to the bar and the t-arm once the ebrake is gone....

plenty more to the frame, if you remove sway bar and use offset t-arms, maybe another inch....but then you need bother with flares...

My car has essentially late shark flares....they look wider than a stock '72 when sitting side/side...but look same as a '78 a friend had....

:thumbs:
 
mrvette said:
Sky65 said:
mrvette said:
ONE of the very first things I did to my '72, some 15 years ago was of course a complete suspension rebuild, and putting 17x9.5 '92 vette rims all around....

255/50/17 in front....Scorcher t/a....rear is NITTO 275/50/17......

I used VBP wheel 2.5 inch wheel adapters.....

:hi:
Click to expand...
What is the backspacing using the 2.5" spacers?
Thanks
Click to expand...

Same as a stock shark rim....I kept the same centerline to minimize the bearling loading at speed......move the ebrake to allow wider tires if you have a rear sway bar keeping the same centerline will make the same clearance to the bar and the t-arm once the ebrake is gone....

plenty more to the frame, if you remove sway bar and use offset t-arms, maybe another inch....but then you need bother with flares...

My car has essentially late shark flares....they look wider than a stock '72 when sitting side/side...but look same as a '78 a friend had....

:thumbs:
Click to expand...
Sorry I'm a confused. Sometimes I'm not the sharpest tool in the shed. What do you mean "Same as a stock shark rim....I kept the same centerline". Stock C3 wheels are 15X8 with 4" backspacing I believe. Do you have 4" backspacing or the same centerline on a 9.5" rim which would give you maybe 5.5" backspacing? I have offset t-arms and small flares already with stock C3 aluminum wheels on the car now.
Thanks.
 
I went with 255's in the rear and 225's in front to avoid rubbing the frame. I get a lot of understeer on any real hard corner. If you're not going to drive it that hard (eg autocross, track day) and don't mind not being able to rotate them, then go for it.
 
lsejlowe said:
I went with 255's in the rear and 225's in front to avoid rubbing the frame. I get a lot of understeer on any real hard corner. If you're not going to drive it that hard (eg autocross, track day) and don't mind not being able to rotate them, then go for it.
Click to expand...
Thanks
What rim width and backspacing? Got any pictures?
 
:thumbs:[/QUOTE]
Sorry I'm a confused. Sometimes I'm not the sharpest tool in the shed. What do you mean "Same as a stock shark rim....I kept the same centerline". Stock C3 wheels are 15X8 with 4" backspacing I believe. Do you have 4" backspacing or the same centerline on a 9.5" rim which would give you maybe 5.5" backspacing? I have offset t-arms and small flares already with stock C3 aluminum wheels on the car now.
Thanks.[/QUOTE]

I simply measured from the flat area on the outside of the rim, that the tire bead would rest against...NOT that little turn out that gets scraped up easy in curb rash....so taking a board cut to length and across the rim I measured to the mounting face inside....on my stock '72 steel wheel I measured 3.5 inches that is what I referred to as the offset...of the RIM...

so on the same spots on my '92 wheels, same technique, I measured 7" .. so with 2.5 inch adapter it nets out at 4.5 inches offset.....
now to keep in mind the rim is 1.5 inches WIDER, so wanting 3/4 inch to each side of that centerline...I subtract 3/4 inch off 4.5 inches and come up with 3.75 inches....close enough.....

I really didn't want the bearing loading to be a problem...You can go much wider to the inside with offset arms, but IF anyone made them 15 years ago, I wasn't aware of them....anyway I feel 275/50 is wide enough with ~10" rubber on the ground...but if you go wider, obviously the sway bar has to be removed, or so highly modded up somehow....to the outside is obviously only the fender to be concerned with....another story...

FYI, just as an aside, when they measure tires for rims in say the Tire Rack site, the engineering drawing shows the wheel offset measures taken to the INSIDE of the rim where the tire bead sits on.....I figger to subtract maybe 1/4 inch for that difference, but long as I was consistent within what I was doing, it made no difference.....:bump::quote:
 
mrvette said:
:thumbs:
Click to expand...
Sorry I'm a confused. Sometimes I'm not the sharpest tool in the shed. What do you mean "Same as a stock shark rim....I kept the same centerline". Stock C3 wheels are 15X8 with 4" backspacing I believe. Do you have 4" backspacing or the same centerline on a 9.5" rim which would give you maybe 5.5" backspacing? I have offset t-arms and small flares already with stock C3 aluminum wheels on the car now.
Thanks.[/QUOTE]

I simply measured from the flat area on the outside of the rim, that the tire bead would rest against...NOT that little turn out that gets scraped up easy in curb rash....so taking a board cut to length and across the rim I measured to the mounting face inside....on my stock '72 steel wheel I measured 3.5 inches that is what I referred to as the offset...of the RIM...

so on the same spots on my '92 wheels, same technique, I measured 7" .. so with 2.5 inch adapter it nets out at 4.5 inches offset.....
now to keep in mind the rim is 1.5 inches WIDER, so wanting 3/4 inch to each side of that centerline...I subtract 3/4 inch off 4.5 inches and come up with 3.75 inches....close enough.....

I really didn't want the bearing loading to be a problem...You can go much wider to the inside with offset arms, but IF anyone made them 15 years ago, I wasn't aware of them....anyway I feel 275/50 is wide enough with ~10" rubber on the ground...but if you go wider, obviously the sway bar has to be removed, or so highly modded up somehow....to the outside is obviously only the fender to be concerned with....another story...

FYI, just as an aside, when they measure tires for rims in say the Tire Rack site, the engineering drawing shows the wheel offset measures taken to the INSIDE of the rim where the tire bead sits on.....I figger to subtract maybe 1/4 inch for that difference, but long as I was consistent within what I was doing, it made no difference.....:bump::quote:[/QUOTE]
Gotcha.
Thanks. I guess I need to hang a bare wheel and do some measuring.
 
Pretty much agree with everything Gene said. One thing to add: most modern wheels are only offered in 7" or more backspacing, like 11x17 ZR1 wheels - they have like 8" or so backspacing. If you wanted to make these work on a C3 you will need a 3.5" or 4" spacer ... that's a bit much IMO.... 2" or 2.5" spacer is the limit for me to feel comfortable.

You say you have small flares. You should have no problem finding a 9.5X17" rim with the stock backspacing (TT2, Boyd, BilletSpec...) depending on your budget.... a 9.5" wide rim with 4" BS will sit 1.5" further out than a stock 8" rim, filling your flares nicely. 275-50 is the perfect size for our cars, not a very common size but Nitto and a few others make that size.

The difference to your old 15" tires is going to be more than noticeable.

keep us updated :bump:
 
MYBAD79 said:
Pretty much agree with everything Gene said. One thing to add: most modern wheels are only offered in 7" or more backspacing, like 11x17 ZR1 wheels - they have like 8" or so backspacing. If you wanted to make these work on a C3 you will need a 3.5" or 4" spacer ... that's a bit much IMO.... 2" or 2.5" spacer is the limit for me to feel comfortable.

You say you have small flares. You should have no problem finding a 9.5X17" rim with the stock backspacing (TT2, Boyd, BilletSpec...) depending on your budget.... a 9.5" wide rim with 4" BS will sit 1.5" further out than a stock 8" rim, filling your flares nicely. 275-50 is the perfect size for our cars, not a very common size but Nitto and a few others make that size.

The difference to your old 15" tires is going to be more than noticeable.

keep us updated :bump:
Click to expand...

Karsten, guys, there is a hell of a difference between a 'spacer' and an ADAPTER.....the adapter will use TEN bolts/lugs per wheel to get to the rotor....5 hold the adapter to the hub assy, and the INTERLEAVED 5 more lugs hold the adapter to the wheel.....it's strong as elephant shit, on a hot summer day too boot....:quote:

a freeking spacer sets between the wheel and the rotor, utilizing just the studs to hold it....and the ones they sell in typical stores are just cast potmetal, totally unsafe CRAP in other words.....

SOME guys make spacers up to 3/8? inch out of good aluminum stock and machine them to fit very snug over the hub, and also snug around the lugs....claiming that reinforces the studs....I dunno, never done it....frankly scared to try, and not any reason to....

:eek:
 
Gene, that's exactly what I'm using:

IMG_5552Large.jpg

I've been using these for 7yrs and almost 100K miles on my Z28 and these spacers (adapters) have taken some serious beating without failing.
 
MYBAD79 said:
Gene, that's exactly what I'm using:

IMG_5552Large.jpg

I've been using these for 7yrs and almost 100K miles on my Z28 and these spacers (adapters) have taken some serious beating without failing.
Click to expand...

:harhar::thumbs::thumbs:

I kinda thought so, but had to say something just in case.....the old axe, safer than sorry.....

:lol:
 
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