18" wheels on 1973?

what is the most backspaceing wheel you can  put on the back of a 1973 ?  i want to  put 18" TQ wheels on the back of my 73, the tire shop said 17"s all the way around would work, but i would like to put  18"s on the back.

Mark:

I think if you look at some of the archived threads on this subject, the 18's will probably fit, but you'll have to go to a low profile tire in order not to have to make modifications to your tach and speedo, by keeping the overall size (circumference? diameter?) the same or as close as possible to original.

Hey Mark,

I've been through this before. anything bigger than 16" loses performance, and gives a more uncomfortable ride. Plus that stagard 17 front 18 rear looks disgusting on a vette of any year, and also makes turning harder.... I think you should rethink this. I did, and I'm way more than happy with my 16x8.5" all the way around wrapped in 225/60/16 firestone firehawk wide ovals..

 

my .02
-Louis

don't forget those high # 's tyres give some comforteble ride...they are one piece of the entire suspension... ok, use small hight as XXX/40/dia BUT install springs and schock absorbers relevand...

I agree with Louis. Anything bigger than 16" looks "wrong" on a C3, even worse when staggered. In addition to altering the look, I don't believe the low profile tires will greatly enhance the cornering numbers...lateral "G". And unless you are on the track and really need additional grip, why sacrifice looks for a fraction of a "G".
Just my two cents,
Scott

YEAH, a C3 needs some rubber under it ,don't go violating it by a few inches rubber as ferraris....  and don't forget ground clearence!!!!!!!!!!!!!!!!!!!!bumps to be concurred ......... our highways ain'trace tracks... how about yours ?

I can't wait to put some 17s on my '77.  Probably going to put 255/45/17s on there to go with them, would like to go wider but don't really want to put offset trailing arms on at the moment and I don't want to take off my rear sway bar.  I've heard a lot of people say that the C3's handle and ride great with the 17's.  I don't know if you can have more backspacing than 4" with 18's without going with offset trailing arms, I've heard some say that with an 18" wheel it doesn't matter if you have offset trailing arms or not because of where the rim and tire would be, but I don't know the details because I haven't really looked into putting 18's on my vette. 

I have 18 inch billet INTRO PENTIA wheels in my 427 '68 vette. The tires are NITTO NT555. Upfront I run 245/40ZR18 (8 inch rims equivalent to 9 inch rims because they are billet) and in the rear 275/40ZR18 (9 inch rims equivalent to 10 inch rims because thet are billet). The tires and wheels fit perfectly in the car. No spacings required. The wheels are  machined to fit within the fenders.The handling is now superb, cornering and in straightaways. A world of difference. Would not have believed until I did the change in the fall of 2004.The car has been lowered slightlly with new springs upfront and in the rear and corresponding gas shocks. I used to run 255R15 with 8.5 inch rims before. 

JMB:

I think we'd all like to see pics of that setup!

IF you don;t wnat to go witht he heavy duty racing springs with a 1/4" cut off the top, and bottom, and go with blistien shocks... and sepnd the extra dought... stick with the stock sizes.. or go a plus 1 configuration. I still think anything more than 16" looks a bit too much, including staggard of any sizes