Maximum Size Rear Wheel/Tires

6

68/70Vette

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I currently have Tom's Differentials offset trailing arms installed on my frame, which is intended for the 70. Tom's advertises his trailing arms as being able to accommodate 5 inch offset wheels. I'd like to stuff some 18 inch big tires under the car, without having rear wheel flares on the quarter panel

On CF, I found one posting where it was said that 18 inch wheels with 10 inch rims and 5.5 inch backspacing would fit...presumably without flares. The tire size quoted was 275 40 18. For fronts the size quoted was 17 inch wheel, 8 inch rims, and 4 inch backspacing. Front tire size was listed as 255 45 17.

I have a Percy's tire sizing tool. Bought it from Summit for about $80. It's plastic and you set it for wheel radius, offset and rim width, mount on the wheel and swing it around. With 18 inch radius, 5 inch offset, and 10 inch rim width, I get good clearance. Hmm..the VBP composite spring, which I bought shortened 1/2 inch, misses the wheel rim but is about 1/2 or so inches where the rubber will be. Since the tire will balloon during road conditions, I'm considering buying another spring shortened by 1 inch to make sure the sure the spring doesn't spear the tire. I'm considering buying American Racing Torque Thrust 2 wheels, since they look traditional. Any other suggestions? I have Billet Vintique Rally Wheel on the 68. they sort of look like the stock Rallye wheels except they are billet aluminum and 17 inch diameter. I decided to try something different for the 70. Up until recently Billet Vintique was sold with the name Wheel Vintique.
 
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17 x 9.5 rims with 295/30 17 (iirc, will verify tomorrow) on it. it is close to the t-arm; and my arm is notched... I'm not sure I could go 1/2" wider, offset is 4.5
 
The limiting factor on width of a large dia. rim is the frame rail, not the TA. Then, once you start lowering your car (alot), the inner wheel tub comes into play as a limiting factor too.
Ive got 285/40/18 on the rear on a 9.5" wide rim with approx 5.3" backspace. The tire rubs on the frame and the wheel tub with alot of suspension compression. My car is quite low though... 26.9" tire height and about a 27.2" fender height in the rear. Seems like many people run this width tire without issue though. Their ride height is just a bit higher
 
I was surprised to find that in fact, later sharks have more flare than the early sharks, and in my car's past p/owners put on flares, later modded down to later shark specs...so my '72 has 275/50/27 on back....

several things, first off , due to costs I have '89 vette rims 17x9.5 on all 4 corners.....255/50/17 in front....

now I but on VBP 2.5" adaptors on all 4 corners, no rubbing, moved the ebrake to behind the rotor on my t-arms....some guys are doing a top mount, but I didn't seem to make that work in my doing it back in '95.....

IF you keep the same wheel centerline you find you only have 3/4 inch to each side to put tires, and so any wider I find I would be into sway bar and or frame and how in hell any offset t-arm does much good under those circumstances, I dunno.....

I kept same centerline on wheels to keep any extra loading of suspension/bearings to a minimum, being a basic cheep bird....

:cool::D
 
285-40 on 18" still fits, even with a 10" rim. BeeJay is running that combo on his yellow C3 if I remember correctly.
:thumbs:
 
MYBAD79 said:
285-40 on 18" still fits, even with a 10" rim. BeeJay is running that combo on his yellow C3 if I remember correctly.
:thumbs:
Click to expand...

Thanks. I assume that's a 5 inch backspace? ..The Tom's trailing arms are designed to take a 5 inch backspace.

...My attention now has been gotten by Forgeline Wheels. They will manufacture wheels according to your specifications...diameter, wheel rim width, offset, etc. So far, so good. But they are a little pricey. Their wheel prices start around $1000 and go up. Their top of the line wheels are apparently machined out of a solid cylindrical blank of aluminum that starts life as liquid aluminum that is then pressed with a 6000 ton press as it solidifies. 6000 pounds is 12,000,000 lbs of pressure. The resulting solid billet cylinder is then CNC'd down to the wheel shape. Using a solid billet allows them to make a wheel that is THREE pounds lighter than otherwise. This is a lot of technology and expense to save three pounds! Does 69427 know about this?

American Racing Torque Thrust 2 (TT2) wheels (18 inch diameters) are so far kind'a a favorite. The rim width I'd like is 10 inches, but the TT2's closest size is 9.5.

I'll make a little cardboard template for the 285-40 tires and place it on my Percy's tire tool to see what the tolerances issues are....Thanks
 
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68/70Vette said:
MYBAD79 said:
285-40 on 18" still fits, even with a 10" rim. BeeJay is running that combo on his yellow C3 if I remember correctly.
:thumbs:
Click to expand...

Thanks. I assume that's a 5 inch backspace? ..The Tom's trailing arms are designed to take a 5 inch backspace.

...My attention now has been gotten by Forgeline Wheels. They will manufacture wheels according to your specifications...diameter, wheel rim width, offset, etc. So far, so good. But they are a little pricey. Their wheel prices start around $1000 and go up. Their top of the line wheels are apparently machined out of a solid cylindrical blank of aluminum that starts life as liquid aluminum that is then pressed with a 6000 ton press as it solidifies. 6000 pounds is 12,000,000 lbs of pressure. The resulting solid billet cylinder is then CNC'd down to the wheel shape. Using a solid billet allows them to make a wheel that is THREE pounds lighter than otherwise. This is a lot of technology and expense to save three pounds! Does 69427 know about this? He does now. :amused:
American Racing Torque Thrust 2 (TT2) wheels (18 inch diameters) are so far kind'a a favorite. The rim width I'd like is 10 inches, but the TT2's closest size is 9.5.

I'll make a little cardboard template for the 285-40 tires and place it on my Percy's tire tool to see what the tolerances issues are....Thanks
Click to expand...

My track tires are 285-18s on 10 1/2" wheels in the back (and 275-17 on 9 1/2" in the front). I've got enough clearance that I could probably fit 295s on the back. I'd sure like to go wider than that, but I'd be rubbing the frame or the inner fender.
FWIW, I'd sure like to get a set of 18" wheels machined up that would look like the late C3 15" aluminum wheels. The price scares the hell out of me though.
 
Thanks all for the good replies. Gunther - Thanks for the photos and info...especially interesting since I have a 68 also.

................

Someone asked about the difference in 17 and 18 wheels. A few years ago, Corvette Fever magazine (now Vette magazine) had a tire article. They printed tire choices for high speed performance tires. As I remember, they only recommended one tire for 15 inch wheels. There were a few selections for 16 inch wheels. There were a large number of selections for 17 and 18 inch wheels, with more selections for the 18 inch wheels.
 
I’m running 10” wide wheels with 295-50-15 tires on the back of my ’72. I had to notch the trailing arms, narrow the spring and grind a small amount from the calipers. Removing the parking brake cable stop and re-routing the cable was needed too. Since the bushings were new I reworked the arms while they were on the car. The tires are very close to the wheel wells but have never hit in the last six years of driving. The wheels are two piece and I had the offset done to my car’s measurements. I’d probably do another 3/32” of offset if I were getting new wheels and I’d need to grind more off the calipers to do that.

I did 17x9.5 with 285s on my '69. That was pretty easy. ITRC all I had to do was deal with the parking brake cable.
 

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Günther-C3 said:
vette427sbc said:
The limiting factor on width of a large dia. rim is the frame rail, not the TA.
Click to expand...

That is correct and I´m wondering why some people need offset TA. Maybe someone can explain me why.

Regards, Günther
Click to expand...

because the trailing arm is 1/2" to the outside of the frame.... either that or I just had 8 extra hours to use up and I figured WTH, why not notch 1/2" off each TA.... or not.
 
SuperBuickGuy said:
Günther-C3 said:
vette427sbc said:
The limiting factor on width of a large dia. rim is the frame rail, not the TA.
Click to expand...

That is correct and I´m wondering why some people need offset TA. Maybe someone can explain me why.

Regards, Günther
Click to expand...

because the trailing arm is 1/2" to the outside of the frame.... either that or I just had 8 extra hours to use up and I figured WTH, why not notch 1/2" off each TA.... or not.
Click to expand...


Ditto, My wheels hit the trailing arms before hitting the frame rails.
 
kutmup said:
SuperBuickGuy said:
Günther-C3 said:
vette427sbc said:
The limiting factor on width of a large dia. rim is the frame rail, not the TA.
Click to expand...

That is correct and I´m wondering why some people need offset TA. Maybe someone can explain me why.

Regards, Günther
Click to expand...

because the trailing arm is 1/2" to the outside of the frame.... either that or I just had 8 extra hours to use up and I figured WTH, why not notch 1/2" off each TA.... or not.
Click to expand...


Ditto, My wheels hit the trailing arms before hitting the frame rails.
Click to expand...

17x9.5 moved ebrake, and 1/4" to arm and sway bar, 1" or so to frame

kept same wheel centerline as stock....

:nuts:
 
I just don't like the look of rubber band tires on C3's so...

On the front i have 15x10x4 with Nitto 555r 275/50VR15's and rear 15x12x4.5 with Nitto 555r 325/50VR15's

Of course I have FLARES LOL

VS Offset Trailing arms, Dick Guldstrand made me a shortened rear spring for rear and VBP 550 coils on the front (really need to go to 650 Lb/in on the front and DA koni's)

:mobeer::mobeer:
 
No idea who's car this is but these are 11x17 rims with what looks like 315-35-17 tires under the stock rear quarters...... No idea what it took to make this fit..... Looks pretty good though :D



21493c78d4dadb3.jpg
 
84rzv500r said:
I just don't like the look of rubber band tires on C3's so...

On the front i have 15x10x4 with Nitto 555r 275/50VR15's and rear 15x12x4.5 with Nitto 555r 325/50VR15's

Of course I have FLARES LOL

VS Offset Trailing arms, Dick Guldstrand made me a shortened rear spring for rear and VBP 550 coils on the front (really need to go to 650 Lb/in on the front and DA koni's)

:mobeer::mobeer:
Click to expand...


Arent those 555r's soft sidewall drag radials? How do they handle in the corners?
 
vette427sbc said:
Arent those 555r's soft sidewall drag radials? How do they handle in the corners?
Click to expand...

They are V rated with a 15,000 mile treadwear expectation, and actually they are the same construction as the performance radial with an extra belt under the tread to stabilize the shape at low inflation pressures. According to the nitto application engineer that i talked to. They are suited to all types of performance driving when inflated to the proper pressures.

I have used them for the street, auto cross, and a dozen drag strip passes . The only downside is that the tread depth is "shaved" from the factory.

:flash:
 
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