Thinking of 27 in diameter tire/wheel options for 55 C4

[55 Rescue Dog]

Dropping off new quarters for my 55 at the body shop tomorrow, and in the meantime out of boredom trying to come up with a 27 inch diameter tire/wheel set up I like. I already have spent too much on sheet metal ,and I am trying to come up with something that will work without hacking the stock fenders, using the late C4 suspension. I would go with 17 in wheels with a 255/50-17 tire, but tire choices are limited, so the next option is a 255/45-18 with many tire choices, but limited vintage looking wheel choices. American Racing has always been my favorite, and can custom make most offsets for more money of course. I just don't know what will exactly work just yet. I want to run matching front/rear wheels, and tires. I need to determine what is the maximum back space I can run the same front/rear, which will determine how wide of a wheel I can go, and determine the offset from there. Wheel width will have to be 8 in up 9.5 in.

[BamaNomad]

Re Wheel selection, when I posted a similar question re wheels for my Nomad which will go on a Corvette Corrections chassis, Chevynut replied thusly, which helped me... It may also be appropriate in helping you answer your questions as well...

Originally Posted by chevynut
BamaNomad, I just looked at a wheel that popular on these cars that you might like. It's the AR Torq Thrust M.

http://www.americanracing.com/wheelS...-torq-thrust-m



This wheel is available in 17x9" with 45mm offset (6.77" BS). If you put a 275 tire on this wheel it would give you a track width of 59.7" which would give you clearance to the quarter panel lip of about .61" and about 1.18" to the inner wheelwell. IMO that's a pretty good fit.

You can also get the Torq Thrust II in 17x9.5" with 52mm offset which would also fit well.

http://www.americanracing.com/wheelS...torq-thrust-ii


I guess I'm at a loss as to why people think they have to run Corvette wheels on these cars with a C4 suspension. There's lots of choices out there for custom wheels that work, and I just found some options taking a quick look.

[55 Rescue Dog]

Re Wheel selection, when I posted a similar question re wheels for my Nomad which will go on a Corvette Corrections chassis, Chevynut replied thusly, which helped me... It may also be appropriate in helping you answer your questions as well...

Originally Posted by chevynut
BamaNomad, I just looked at a wheel that popular on these cars that you might like. It's the AR Torq Thrust M.

http://www.americanracing.com/wheelS...-torq-thrust-m



This wheel is available in 17x9" with 45mm offset (6.77" BS). If you put a 275 tire on this wheel it would give you a track width of 59.7" which would give you clearance to the quarter panel lip of about .61" and about 1.18" to the inner wheelwell. IMO that's a pretty good fit.

You can also get the Torq Thrust II in 17x9.5" with 52mm offset which would also fit well.

http://www.americanracing.com/wheelS...torq-thrust-ii


I guess I'm at a loss as to why people think they have to run Corvette wheels on these cars with a C4 suspension. There's lots of choices out there for custom wheels that work, and I just found some options taking a quick look.

I would like to run 17's, but the only tire choice I would consider in a 255/50-17 are a couple of Nittos. I want sticky max summer/race tires, but the only ones anyone makes are drag radials in that size. Corvette wheels, or any newer designs out there, just don't look right on a these cars. Has to be modern old school. It's the positive offset that makes it difficult.

[chevynut]

I want to run matching front/rear wheels, and tires. I need to determine what is the maximum back space I can run the same front/rear, which will determine how wide of a wheel I can go, and determine the offset from there. Wheel width will have to be 8 in up 9.5 in.

Are you saying you want the EXACT same front and rear wheel and tire, with the same size and backspacing? If that's the case, you have to go by what fits on front and use that on the rear.

[rockytopper R.I.P 5-13-2017]

The thing is none of the pictures posted here represent this style wheel with that much negative offset. Go look at pictures of new challengers and Camaros etc it looses it sex appeal so to speak. They become very convex looking... Just MHO

[55 Rescue Dog]

Are you saying you want the EXACT same front and rear wheel and tire, with the same size and backspacing? If that's the case, you have to go by what fits on front and use that on the rear.

Yes I want to use the same F/R. What might be the max back spacing for the front with a 27 inch tall tire?

[chevynut]

Yes I want to use the same F/R. What might be the max back spacing for the front with a 27 inch tall tire?

As I've said before, I don't talk backspacing because it's dependent on wheel width and it gets confusing. As far as I know the diameter of the tire really doesn't matter that much but I don't know where the rubbing actually occurs with the C4 suspension. I think it would hit first near the top back of the tire opposite the turn. For example, if turning at full left lock, the rubbing would occur on the right tire behind the tire center at the top of the wheel opening. Custer55 once said it was at the top of the fender opening. One would expect that a taller tire would rub sooner. We know that a 55 has a taller fender opening than a 56 or 57.

Custer55 says he's running a 275/40-17 tire at 25.7" diameter on a 17x9.5 wheel with 56mm offset. He says he's experienced no rubbing issues with his 3" front suspension drop which is kind of a surprise to me, but he also says it's close. His tires would theoretically be 68.39" wide outside which is wider than I typically recommend. However, my recommendation of 67.5" max width is based on years of empirical data from tri5 owners using stock suspensions and steering. The C4 rack steering angle is less than stock, and the wheel rotates differently due to the high SAI, at least on the late C4 suspension.

My 56 Nomad has 245/45-17 front tires (25.7" theoretical diameter) mounted on 17x8.5 wheels with 50mm offset and the tires don't rub anywhere at full lock at full suspension compression with a 3" suspension drop. I don't know for sure how much margin I have at the fender but it's not much. I have around 3/4" clearance to the frame at full lock as well. The outside of the tires are at about 67.75" (theoretically at 67.66"). So if I was to go with a wider tire on my car, I'd go with more offset to keep the tires under 68" which seems like about the limit with the late C4 suspension based on my car and Custer55's car. I would put the additional width to the inboard side. With a taller tire, I think I'd keep that width on the low end.

So the anectodotal evidence says to stay under 68" wide but I still think that's pushing it. I also think the tire could be wider than my 245s but I don't know if 275s would fit on my car. I have a set of stock C4 wheels and tires in the shop now so maybe I should try it.

Let's assume the 275 fits as it did on Custer55s. I believe he's pushing the limits on both sides with the 56mm offset so that's what I'd use. On a 9.5" wheel that would be 7.45" backspacing. I think it might require a thin spacer in the rear to clear the dogbones, and Custer 55 said he used a 3/16" spacer.

I thought you had a late C4 Corvette. Why don't you put the wheels and tires on your 55 and see where they are as far as fitment, and go from there?

[Custer55]

As I've said before, I don't talk backspacing because it's dependent on wheel width and it gets confusing. As far as I know the diameter of the tire really doesn't matter that much but I don't know where the rubbing actually occurs with the C4 suspension. I think it would hit first near the top back of the tire opposite the turn. For example, if turning at full left lock, the rubbing would occur on the right tire behind the tire center at the top of the wheel opening. Custer55 once said it was at the top of the fender opening. One would expect that a taller tire would rub sooner. We know that a 55 has a taller fender opening than a 56 or 57.

Custer55 says he's running a 275/40-17 tire at 25.7" diameter on a 17x9.5 wheel with 56mm offset. He says he's experienced no rubbing issues with his 3" front suspension drop which is kind of a surprise to me, but he also says it's close. His tires would theoretically be 68.39" wide outside which is wider than I typically recommend. However, my recommendation of 67.5" max width is based on years of empirical data from tri5 owners using stock suspensions and steering. The C4 rack steering angle is less than stock, and the wheel rotates differently due to the high SAI, at least on the late C4 suspension.

My 56 Nomad has 245/45-17 front tires (25.7" theoretical diameter) mounted on 17x8.5 wheels with 50mm offset and the tires don't rub anywhere at full lock at full suspension compression with a 3" suspension drop. I don't know for sure how much margin I have at the fender but it's not much. I have around 3/4" clearance to the frame at full lock as well. The outside of the tires are at about 67.75" (theoretically at 67.66"). So if I was to go with a wider tire on my car, I'd go with more offset to keep the tires under 68" which seems like about the limit with the late C4 suspension based on my car and Custer55's car. I would put the additional width to the inboard side. With a taller tire, I think I'd keep that width on the low end.

So the anectodotal evidence says to stay under 68" wide but I still think that's pushing it. I also think the tire could be wider than my 245s but I don't know if 275s would fit on my car. I have a set of stock C4 wheels and tires in the shop now so maybe I should try it.

Let's assume the 275 fits as it did on Custer55s. I believe he's pushing the limits on both sides with the 56mm offset so that's what I'd use. On a 9.5" wheel that would be 7.45" backspacing. I think it might require a thin spacer in the rear to clear the dogbones, and Custer 55 said he used a 3/16" spacer.

I thought you had a late C4 Corvette. Why don't you put the wheels and tires on your 55 and see where they are as far as fitment, and go from there?

I don't know about a 27" dia. tire on the front as the clearance on the front at full lock is pretty tight. I think it would be tighter with a larger dia. tire but the only way to know for sure is to try it since the 255 tire RD is thinking of are narrower. I didn't think the 275 tire would work on mine either. I just tried it to see how tight it would be to figure out what would work. I will have to put the Corvette wheels back on the Corvette this spring and when I buy new tires for the front of my 55 I will most likely go with a 255/40/17 to gain a bit of clearance and lower the front of the car a bit. On the back I used the 3/16" spacer to center the tire in the wheel well better. Clearance to the dog bones is not an issues as it is the same as a stock Corvette with the Corvette wheels. The spacer gives better clearance to the stock inner wheel well which is tight without the spacer.
Hope this helps.
Brian

[chevynut]

Thanks for the additional feedback Custer55. You're right about the stock rear wheels and tires fitting...it would only make sense that a late C4 wheel would fit a late C4 rearend . I calculated the distance between the inside of the 275 tires to be 48" and the inner tubs are 46.5". The dogbones are about 45.25" in the middle, wider at the front end where a larger diameter tire might interfere. I still think the tub is the limiter as you said, but 3/4" should be enough clearance.

I usually tell my customers that a 245 tire will fit in front, but it's up to them to try anything larger.

[55 Rescue Dog]

I will have to wait until the car has the body back on to know for sure, but I will try and make the 255/45-18 tire work, since I like the bigger diameter, and they worked so well on my 96 Impala SS with the Goodyear F1's I ran, with lots of tire choices. Just on Tirerack they have 64 tires to choose from in that size, versus 2 tires in a 255/50-17. American racing makes the torque thrust wheel I like in a 17x9 with 45mm offset/6.77 backspace that is the C4 fitment. To go with 18's the custom shop can make an 18x8 with up to 41mm offset, or a 18x9 with up to 54mm offset. The inboard clearance is my biggest concern at this point, but I also want less positive offset so the wheel has a little deeper dish to it. thanks for the input.