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Yet another wheel/tire size question

steveh326

Active Member
Getting VERY close to pulling the trigger for some new 17" wheels tires for my 66. I have read charts and searched for info till I have a headache. Like everyone else, I want to stuff as much tire under the car as will fit without clearance issues. no intention to race the car, just going for looks here, although I will enjoy driving the car to it's limit in the twisties.

Suspension: front has the shelby drop and 1" shorter springs. rear is using mid eye 4.5 leafs. I would like to avoid having to use spacers.

Here are the wheel specs I'm looking at. I am not locked into these exact wheels, but I AM pretty much locked into the black TT type wheels in 17", so if anyone knows of another source for same looking wheels with different backspacing, I am all ears.

Front: 17x7, 4.00 backspace
Rear: 17x8, 4.50 backspace

I know 225's will fit on the front but could I go 235?
I know 235's will fit on the rear but could I go 245?

car isn't painted yet, I am not opposed to rolling/trimming fender lips if I have to, but would like to avoid major surgery beyond that. I don't have a gazillion dollars to buy tires to experiment with clearance, so I'm trying to get it right in one shot.

Many many thanks for any replies... I know this subject has been beat to death but I haven't been able to find exactly the answers I need and it's a fair amout of $ on the line.
 
"steveh326" said:
Front: 17x7, 4.00 backspace
Rear: 17x8, 4.50 backspace

I know 225's will fit on the front but could I go 235?
I know 235's will fit on the rear but could I go 245?
Every car is a little different. Every tire is a little different too. For instance Nitto's run undersize - their 235 is closer to others' 225's...
Brakes CAN make a difference too - especially Wilwoods...

With 4.0 B/S on a 7" wheel, 225 is about it in front.
Go to 4.25 or 4.5 B/S, and 235's are do-able, or go to an 8" 4.75 BS wheel, and you're "probably" good with 235's...

Really prefer 4.75 B/S in the rear, especially if you want 245's. A 235 is probably all you'll comfortably get with 4.5 BS.

Yes, DEFINITELY roll the fender lips before paint.
 
"BobV" said:
Every car is a little different. Every tire is a little different too. For instance Nitto's run undersize - their 235 is closer to others' 225's...
Brakes CAN make a difference too - especially Wilwoods...

With 4.0 B/S on a 7" wheel, 225 is about it in front.
Go to 4.25 or 4.5 B/S, and 235's are do-able, or go to an 8" 4.75 BS wheel, and you're "probably" good with 235's...

Really prefer 4.75 B/S in the rear, especially if you want 245's. A 235 is probably all you'll comfortably get with 4.5 BS.

Yes, DEFINITELY roll the fender lips before paint.
FYI -- Wilwood and others now offer different brackets that eliminate the old issue of pushing the wheels out when using Wilwood hubs.

If you are going to push the issue and try to stuff as wide a tire in there as you can, follow Mark's advice and rent Shaun's tool (or make your own) and get some real application information. Like Bob said, there tend to be little differences from car to car and certainly tire manufacturer to manufacturer.

If you do do big out back you may need to section in a piece of metal in the front corner of the inner wheel well to eliminate that inward sheet metal curve. Sometimes a big hammer can get you enough but other times not so much.
 
thanks for the replies and advice, I appreciate it.

it's sounding like 225/235 is my best bet with those wheels without doing unnatural acts. I know backspacing can allow for more tire but kinda limited to whats available in the wheel style I picked so I have to work within those limits.

Renting Shaun's wheel/tire gauge is a great idea, thanks. Good point on the brakes, I forgot to mention that... car has stock discs up front, but I am swapping out the caliper for one from SSBC that replaces the stock caliper but has bigger pad area. stock drums out back for now, someday in the future would like to update to matching SSBC discs out back but thats at least a year away.

Before the car was blown apart for structural and rust repairs it was running E70's on the front and F60's on the back on 14" Keystones that I put on back in the 70's. the 14" wheels won't clear the new SSBC calipers on the front, and once all the rust and sheetmetal repairs are done and it's ready to put back on the ground to take to paint I need to have the rolling stock on hand so I can wheel it around.
 
OK wheels got here yesterday, they look nice to me. now I need to decide on some 225/235 tires to put on them. crsuising tirerack.com for the sizes I need, thinking about Hankook Ventus RS-3 cause I like the tread, but have never had any of these summer performance tires before. I know tread life will be short on them.
 
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