Spare Tire Strategy

[EngineerDoug]

Hello all,

I am confronting a question that surely many of you have faced. My 68 Coronet is about to get new tires & wheels, and the front will be a different size than the rear. I have a TrueTrac differential, so whatever I use as a spare must be very close to the rear tire diameter.

Here is what I am considering:

Front: 235-60/15
Rear: 255-60/15 or 255-70/15

I would really like to run the 70 series on the rear to keep cruise RPM down, but these will be a 29 inch tire. I can use a narrower spare that is still 29 inches tall, but I doubt this would fit on the front in case of a flat.

What do most folks do? I do have AAA, but would still like to carry a spare.

Thanks.

 

[65 3 times]

Tire tech has come light years since '68. Your '68 is probably a limited use vehicle. For a short distance home or to a shop will not damage a differential. I like late model high pressure spares. Plenty of tire to get you a hundred miles. Remember to pack an extra set of lug nuts and wrench to fit if you use a tin wheel for spare. If your a car show guy sew up an attractive cover. Happy motoring and be safe. Dave

 

[65 3 times]

P.S. I love the 255/70R15 on rear. How about 215/70R15 front. (24" and 29") JMHO Dave

 

[khryslerkid]

I can use a narrower spare that is still 29 inches tall, but I doubt this would fit on the front in case of a flat.

Find one that will fit. I'm in the same boat and haven't followed through yet. I might even use a 14" factory wheel with the correct height tire as my rear ones.

I had a vehicle with a limited slip, had a flat on the interstate, changed it with the dognut spare. Never gave it a thought until it was too late, burnt those clutches.

 

[EngineerDoug]

The word I got from Dr Diff (I have his Dana 60 out back) is to NOT mismatch the rear tire sizes by more than 1/2".

 

[GetX'd]

Hmmm I don’t carry a spare either. Don’t even have a rim to put one on. Does it do any good to carry that flat tire fixer stuff you buy at Pep Boys or elsewhere. I don’t drive my car very much but feel insecure not having a spare like the OP stated

 

[moparedtn]

Personal preference of course, but for me the '68-'70 b-body rear wheelwells hold a 275/60/15 about perfectly with the proper offset.
Not even close to rubbing even. That gives you a 28" tall assembly. With about a 225/70/15 on front, it even gives a slight natural "rake".
A 28" diameter spare of whatever width takes care of all at that point.

 

[moparedtn]

Hmmm I don’t carry a spare either. Don’t even have a rim to put one on. Does it do any good to carry that flat tire fixer stuff you buy at Pep Boys or elsewhere. I don’t drive my car very much but feel insecure not having a spare like the OP stated

Same here. I don't even have any of the jack parts, which will cost me a small fortune I'm sure.
Further, these BFG's have less than 1000 miles on them and they look new, but they're 8 years old.
Yikes.

 

[69L48Z27]

Carry a can of fix a flat and/or plug kit and small compressor. If you shred a tire your out of luck but this will get you where you need to go. The tire changer will be cuss'n you for the fix a flat. Makes a mess.

 

[PurpleBeeper]

I plan to have the same diameter front/rear tires & I've already bought my spare tire. I also have limited-slip, don't want to burn out the rear end & want to have one spare tire that will fit anywhere on the car. I "think" it's 255/60R15 rear and 235/70R15 in front ?????? Just check the tire diameter information on various online tire. The spare is a tight fit, but get in there. I don't want to be 3 states away from home without a spare/jack

 

[chtampa]

AAA, I won't put a jack against the bumper or change a tire.

 

[oldbee]

Use a spare with the same size as rear tires. Diff is the only thing that matters really. Tried looking for a steel wheel at junkyards? No luck, then the youngest son said get a car trailer wheel, almost all are Mopar stud spacing. Imagine that, 1/2 or less the price. May not be correct but it’s only a spare.

 

[Dennis H]

I carry a Steel wheel spare with an older Cooper on it. 225/70 14. It will fit all corners. I checked. AAA is the best, but not when no cell signal in the boonies where I often go. Scissors jack. Depends on what you plan to use the car for. It is heavy and takes up space. Necessary evil.

 

[Larrry B.]

It was my intention to get a spare but I never have in all the years driving my car. AAA helped a couple of times but I was always in town. Going to 17" wheels soon (18" eventually), I'll probably never carry a spare as I'll have staggered sizes. Will just have to be careful or look into run flats for longer distances.

 

[moparedtn]

I plan to have the same diameter front/rear tires & I've already bought my spare tire. I also have limited-slip, don't want to burn out the rear end & want to have one spare tire that will fit anywhere on the car. I "think" it's 255/60R15 rear and 235/70R15 in front ?????? Just check the tire diameter information on various online tire. The spare is a tight fit, but get in there. I don't want to be 3 states away from home without a spare/jack

Those sizes will give you a 27" tall tire in the rear and a 28" in front.

Pretty easy to figure if you have a calculator nearby:
Sidewall height = width x percentage (aspect ratio) = 255 x 0.60 = 153 (mm)
You have that height on bottom and top, of course, so: 2 x 153 = 306 mm
Converting to inches: 306 divided by 25.4 = 12.04"
Add in the 15" rim and you get a total of 27" height.

 

[moparedtn]

AAA, I won't put a jack against the bumper or change a tire.

I can see that. When I get a factory jack setup, it'll just be for show, really.
I'd like to find a really compact floor jack to carry and actually use if needed.

 

[PurpleBeeper]

Those sizes will give you a 27" tall tire in the rear and a 28" in front.

Pretty easy to figure if you have a calculator nearby:
Sidewall height = width x percentage (aspect ratio) = 255 x 0.60 = 153 (mm)
You have that height on bottom and top, of course, so: 2 x 153 = 306 mm
Converting to inches: 306 divided by 25.4 = 12.04"
Add in the 15" rim and you get a total of 27" height.

You're right....I couldn't remember the exact tire size number, but 28" sounds about right. Should I maybe have said 275/60R15 for the rear?

 

[moparedtn]

You're right....I couldn't remember the exact tire size number, but 28" sounds about right. Should I maybe have said 275/60R15 for the rear?

Yep, that'll give you exactly a 28" O.D. Fits real nice in the wheelwell too.
It's what I have on mine. I run a 225/70/15 on the front for a slight rake.

 

[chtampa]

I can see that. When I get a factory jack setup, it'll just be for show, really.
I'd like to find a really compact floor jack to carry and actually use if needed.

My jack is purely for show, so is the spare. I have 45K in the car and it is for all intention brand new so I dress up when I go to a show or drive it. When you have nice you treat yourself to nice and I am now an owner not a mechanic. I am its mechanic when it is home.

 

[GetX'd]

I can see that. When I get a factory jack setup, it'll just be for show, really.
I'd like to find a really compact floor jack to carry and actually use if needed.

You can get a compact scissor jack at Pep Boys for $30. I have ne of those just don’t have the tire.