7 or 7.5 wide 14" rims - Another tyre size question

[Righty]

Hi, I want to replace the wheels on my 69 Barracuda - original discs front and drums rear.

ATM it has the Pro stock look big old 275s at the back and skinny 185s at the front. I'd like to change to a more OEM look, but get a bit more rubber on the road, I got a full set of original 14" x 5.5J rims and matching covers with the car which have cleaned up lovely just need the centres repainting, so I have a plan.
I can get the rims widened and refurbed so I would like to take them out to about 7 - 7.5J Ideally 7J as that is 1" wider than the Recall Rims which satisfies the regulations in NSW Australia where I'm moving to. I dont intend to go wider than 235 in a 60 section that gives a diameter of 25.1".

So the eternal question: I would like to run the same widths front and back, so with the aprox 4" backspace on the rim would a 235 / 60 r14 be too wide for the front on either a 7 or 7.5J rim?
Obviously anyonw th any similar set ups on their cars I would love to hear what you think.

 

[junkyardhero]

i think you're going to need more than 4" of backspacing

you're adding 2" so there needs to be a compensation for that, especially in the front where the leading edge of the fender is a limiting factor.

out back, not as important.

 

[Righty]

i think you're going to need more than 4" of backspacing

you're adding 2" so there needs to be a compensation for that, especially in the front where the leading edge of the fender is a limiting factor.

out back, not as important.

Yes, at the back, with the measurements I have taken, a 235 will work fine even with 4” backspace.
Reading at other threads on here and elsewhere, there seems to be a lot of people running 205/70 quite a few running 215/70 and a handful with 235/60. The rim selection is usually 6” Rally and 7” Cragar so probably a maximum of 4.25” backspace.

Of course the simplest solution which I think I’ll follow, is get 2 wheels mounted with 235/60 I can test fit them at the front. If I’m good then lovely if not they can pop on the back and I can down size based on what the test fitting showed. I think if I keep to 7J width and 60 sections for the tyres the diameters will be reasonably close to the factory tyres.

 

[72bluNblu]

Since you have the small bolt pattern still you might actually be ok in the front with a 14x7 with a 4" backspace.

With the large bolt pattern disks a 15x7 with 4.25" backspace allows for a 225/60/15. And the track width difference between the SBP and BBP is more than a 1/2" per side. So by the math it's pretty darn close, you lose a 1/4" of backspace and gain 5mm (.2") of tire to the outside, so with the SBP a 235 should end up pretty close to the same position as the 225 on the BBP set up, with a shorter tire.

The other thing to consider is that with a 14" wheel you're going to be more limited for backspace than a 15" wheel is before you start hitting brake and suspension parts. Not exactly sure where that is, on a 15" wheel if you get much past 4.5" of backspace it's brake and wheel design dependent for getting into hard parts.

Having the rears widened and checking the fit on the front would definitely be the way to go to test it.

 

[LJ67barracuda340]

I run a 67 Barracuda with OE Kelsey Hays front disc and 8.75 rear with drums. I use 14x7x4.25 back space SBP rallies with 245/60/14 on the rear. My fronts are 14x5.5 rallies. I'm thinking of switching to 15x7" all round, so I put a rear on the front to check clearance with these dimensions. There was no issues in the front anywhere from lock to lock. I'm also running the front with about a 1" drop. Hope this relates.

 

[Righty]

Since you have the small bolt pattern still you might actually be ok in the front with a 14x7 with a 4" backspace.

With the large bolt pattern disks a 15x7 with 4.25" backspace allows for a 225/60/15. And the track width difference between the SBP and BBP is more than a 1/2" per side. So by the math it's pretty darn close, you lose a 1/4" of backspace and gain 5mm (.2") of tire to the outside, so with the SBP a 235 should end up pretty close to the same position as the 225 on the BBP set up, with a shorter tire.

The other thing to consider is that with a 14" wheel you're going to be more limited for backspace than a 15" wheel is before you start hitting brake and suspension parts. Not exactly sure where that is, on a 15" wheel if you get much past 4.5" of backspace it's brake and wheel design dependent for getting into hard parts.

Having the rears widened and checking the fit on the front would definitely be the way to go to test it.

Thanks, I guess that’s why I had considered wether it is doable, because a 355/60 is 25.2” diameter, its not placing the surface of the tyre further forwards towards the edge of the wheel arch than an OEM tyre, in straight ahead position, the question as Junkyard said, does that extra depth reach further forwards towards the arch when turned.

I think I’m making the mistake of over thinking and over asking. I have a direction I want to go - the old school original look, so I’ll bite the bullet, widen up a pair of rims and test it out. Of course the next problem is do I stump up for some redlines to nail the look.

 

[33IMP]

I would stay away from Coker redlines, bias or radials.
If you have the budget, I'd at least talk to Diamondback for redlines. (I have no idea what shipping would cost!)
There is always the sticker redline method. I haven't tried it, but one of the guys on the B-side added white wall stickers. He was happy with results, as I recall.
I think your idea of widening a pair, fitting the rear tires, and then seeing if they would work on the front is an excellent idea.

 

[72bluNblu]

Thanks, I guess that’s why I had considered wether it is doable, because a 355/60 is 25.2” diameter, its not placing the surface of the tyre further forwards towards the edge of the wheel arch than an OEM tyre, in straight ahead position, the question as Junkyard said, does that extra depth reach further forwards towards the arch when turned.

I think I’m making the mistake of over thinking and over asking. I have a direction I want to go - the old school original look, so I’ll bite the bullet, widen up a pair of rims and test it out. Of course the next problem is do I stump up for some redlines to nail the look.

I honestly think it'll be fine, especially with the input from LJ67barracuda340.

It's always good to do some thinking and asking, really easy to mess up backspace and wheel fit. But you definitely get to a spot where you can only do so much math and you've actually gotta fit something. Having the rears done and checking them on the front is a great plan and a good option to have.

 

[Righty]

I run a 67 Barracuda with OE Kelsey Hays front disc and 8.75 rear with drums. I use 7x14x4.25 back space SBP rallies with 245/60/14 on the rear. My fronts are 14x5.5 rallies. I'm thinking of switching to 7x15" all round, so I put a rear on the front to check clearance with these dimensions. There was no issues in the front anywhere from lock to lock. I'm also running the front with about a 1" drop. Hope this relates.

That’s interesting. The previous owner had fitted 275 on an 8.5j rim with 4.75BS on the back and there is 0.3” clearance to the springs and to the inner lip. So I plotted out my rear arch hub and spring positions and from my calculations with a 235 on 4” BS I will have about 0.75” to the upper part of the arch lip.

When I drew it up, a 245 on a 7 or 7.5 rim with 4.25BS had about 0.5” to the upper arch lip, does that sound similar to what you found?

So when you had the 425 up front there was no interference even on full lock?

 

[Righty]

I would stay away from Coker redlines, bias or radials.
If you have the budget, I'd at least talk to Diamondback for redlines. (I have no idea what shipping would cost!)
There is always the sticker redline method. I haven't tried it, but one of the guys on the B-side added white wall stickers. He was happy with results, as I recall.
I think your idea of widening a pair, fitting the rear tires, and then seeing if they would work on the front is an excellent idea.

Yes I’m a CAD monkey for a living, so I get a bit sucked in to drawing and modelling things up, which is definitely useful, but when it comes to 75 year old cars and bouncy bits of rubber the best way is to get it on there!

I had considered BFG or Diamond Back, but costs incl. shipping will be a killer, so either the stick on option or as I discuss with my wife, I pop up the car on some jack stands, into gear and she gets up close with some nail varnish, that only does the rears though!

Interestingly someone on a TV show here took some tyres to a bloke who ground a little channel onto the side wall for painting, funnily they didn’t explain that it’s completely illegal to do that.

 

[LJ67barracuda340]

That’s interesting. The previous owner had fitted 275 on an 8.5j rim with 4.75BS on the back and there is 0.3” clearance to the springs and to the inner lip. So I plotted out my rear arch hub and spring positions and from my calculations with a 235 on 4” BS I will have about 0.75” to the upper part of the arch lip.

When I drew it up, a 245 on a 7 or 7.5 rim with 4.25BS had about 0.5” to the upper arch lip, does that sound similar to what you found?

So when you had the 425 up front there was no interference even on full lock?

Like I said "Lock to Lock" on the front. Sound right in the rear. I like to run mine with the tires in the wheel well and not sticking out like my old days.

Are your springs relocated? What you say the PO had on there doesn't sound like it would work on mine and be in the wheel well.

 

[Righty]

I honestly think it'll be fine, especially with the input from LJ67barracuda340.

It's always good to do some thinking and asking, really easy to mess up backspace and wheel fit. But you definitely get to a spot where you can only do so much math and you've actually gotta fit something. Having the rears done and checking them on the front is a great plan and a good option to have.

Indeed, as they say in Scotland, “It’s time to piss, or get off the pot”.

 

[72bluNblu]

That’s interesting. The previous owner had fitted 275 on an 8.5j rim with 4.75BS on the back and there is 0.3” clearance to the springs and to the inner lip. So I plotted out my rear arch hub and spring positions and from my calculations with a 235 on 4” BS I will have about 0.75” to the upper part of the arch lip.

When I drew it up, a 245 on a 7 or 7.5 rim with 4.25BS had about 0.5” to the upper arch lip, does that sound similar to what you found?

So when you had the 425 up front there was no interference even on full lock?

Keep in mind you guys may not have the same rear axle and that could mean a different axle width and therefore a different backspace.

In the front the tire height is more of an issue, on a Barracuda when you start getting close to 26" tall the lower front corner of the wheel opening gets to be an issue.

Width isn't usually an issue with the proper backspace until it gets really extreme. I run 275/35/18's up front, they take a lot more backspace and that puts them much closer to the frame rails.

 

[LJ67barracuda340]

Also the tires you choose with make a bit of difference when you start to get close. The measurement is the side wall but different tires of the same size could have different tread widths (shape).

 

[Righty]

Like I said "Lock to Lock" on the front. Sound right in the rear. I like to run mine with the tires in the wheel well and not sticking out like my old days.

Are your springs relocated? What you say the PO had on there doesn't sound like it would work on mine and be in the wheel well.

No the springs are stock, he was an engineer so everything was well centred, he’d trimmed the chrome trim back inside. But it’s super tight I can just squeeze my finger tip between the tyre and the spring and against the recessed lip of the arch on the outer side. He even used to tow a caravan with it! But way to tight for me, plus like you, nowadays I like a less extreme look and setup.

 

[Righty]

That is a good point, without getting right into it I can’t say for sure that the rear set up is 100% stock other than what he has told me, he had it for 36 years, so he has probably forgotten half the stuff he might have done!
I think that because I’m going for the “factory” 14” look, I do at least have the breathing room of not maxing the diameter of the tyre, even if it does significantly limit the ability to backspace the wheels. Anyway, this is half the point of having these cars I guess, thinking, puzzling, trying stuff out.