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 Deciding on 15" tire options

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GasTT



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PostSubject: Deciding on 15" tire options   Wed Feb 01, 2012 9:34 pm

235/70 or 255/60?

I am really leaning toward the 255/60. I like the width and shorter sidewall.

I am going with the Firestone Firehawk Indy 500 (What else?) These tires will be going on 15x7 wheels and getting mounted on my Caprice.

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mega



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PostSubject: Re: Deciding on 15" tire options   Wed Feb 01, 2012 9:48 pm

255.
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MASShole9C1



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PostSubject: Re: Deciding on 15" tire options   Wed Feb 01, 2012 9:55 pm

255. Ive got 235 on my gold L99, doesnt look right IMO with the white walls. Idk. whatever you think is best. Using the same black 15's or something else?
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GasTT



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PostSubject: Re: Deciding on 15" tire options   Wed Feb 01, 2012 9:56 pm

I have also been looking into 275/60. Some people say it's no good on a 15x7. Some people have had luck. I read a good point online. The 1990 454SS came from the factory with 275/60's on a 15x7 wheel. 235/70 up front and 275/60 out back?

Using my american racing wheels.
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Matt Trakker



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PostSubject: Re: Deciding on 15" tire options   Wed Feb 01, 2012 10:21 pm

Let me know how your fitment goes. I want to get 2 more 255s in this tire for the set of chrome Rallys I have that were from Crovo's SS. Right now the back are 295s, lol. I wonder if 275 fits all the way around? If it does, I may get 275s for the back for now...
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Machine-De-Zine



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PostSubject: Re: Deciding on 15" tire options   Thu Feb 02, 2012 3:27 am

Matt Trakker wrote:
Let me know how your fitment goes. I want to get 2 more 255s in this tire for the set of chrome Rallys I have that were from Crovo's SS. Right now the back are 295s, lol. I wonder if 275 fits all the way around? If it does, I may get 275s for the back for now...

275/60 15s are the old "L-60" series. Usually you've got to have at least 8", & perhaps better to have 8.5" to 9.5" rims for that tire size.
I usually find that a good rule of thumb for most tire designs within this range of discussion, , ,
-> match the wheel measuring width to the tread width <-

275s will definitely fit at all four corners if everything is right, especially up front.
Some things to watch out for;
The most (or deepest) back space for a stock B-body spindle on 15" steel rims is close to 5.250". Its the steering arm that hits first.
A fat aftermarket front sway bar will limit turning circle radius, as it WILL rub the larger tire before reaching steering system's mechanical limits.
Cut down front springs, or very low sprung suspensions will aggravate tire rubbing when hitting bumps and/or on tight turns.
Not enough back space (less than 4") on 8.5" x 15" wheels with 275/60 15 tires will very likely hit the front outer wheel house near the wheel lip moulding.
Everybody here must know by now that the SS & 9C1 rear ends are NOT the same,
SS = 1598mm (62.91") and 9C1 = 1566mm (61.65") - OR -> 16mm (5/8") per side!
N97s are 15 x 7 and have 4.5" back space.
Best fitting tire for this HD police wheel on these cars is 235/70 15, Note: 255s will fit, but are "squeezed-in" at the beads, causing uneven tire wear patterns at proper inflation pressures.
70s & 80s 15 x 8.5" truck wheels that have the 5 on 5 B/C almost always have only a 3.500" to 3.875" backspace range, so it is tempting, but depending on tire size and ride height, outside tire rubbing likely on our cars.

I am researching this same subject for my cars and this is where I am at now.
Good tires are gone unless you are drag racing, road racing or looking for specifically "rain-mud-snow-happy" tires.
BFG, Firestone 500s, & Coopers are big sellers, none are stellar performers, however they are cheap to buy new, just over $100 per pc.
Then there are some very good specialty tires for autocross and drag racing, typically designated as "R" compound versions, like the Nitto 555R in 275/60 15.
An 8.5" x 15 rim with 0 offset will have 4.750 backspace, but I think that same wheel made to have 5" B/S would tuck-in even better with 275/60 15s on them.


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PostSubject: Re: Deciding on 15" tire options   Thu Feb 02, 2012 5:15 am

I have had 275/60/15s on a stock fleetwood 7" rim. Either the 255 or the 275 will fit.
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Fishah



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PostSubject: Re: Deciding on 15" tire options   Thu Feb 02, 2012 11:27 am

295/50/15 rear
255/60/15 front

or

275/60/15 rear
255/60/15 front

255/60/15 is too narrow for the rear IMO.
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V8Killer



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PostSubject: Re: Deciding on 15" tire options   Thu Feb 02, 2012 11:43 am



255/60's cheers
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96slowss



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PostSubject: Re: Deciding on 15" tire options   Thu Feb 02, 2012 1:10 pm

255/60
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Matt Trakker



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PostSubject: Re: Deciding on 15" tire options   Thu Feb 02, 2012 3:38 pm

On my Impala, I have 255/60, but they are BFGs on I think 7" wide wheels. I'm pretty sure the same chrome Rallys that have the Firestones are 15x8s.

The Firestones seem a lot smoother and ride a little nicer. The 255 BFGs don't seem too tucked in at the rim on the 7" ones, in contrast the Firestone 255s on the 8" wheels seem to be wider at the rim and tucked in at the tread area.

I was gonna get 255s for the rears because I wanted to be able to rotate them...but if 275 on a 8" wheel would fit all the way around I'd be tempted to get those...

The 255 always looks good, I will say. Very Happy



For comparison:

235/60


255/60
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GasTT



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PostSubject: Re: Deciding on 15" tire options   Fri Feb 03, 2012 8:09 pm

Thinking of 235/70 up front and 275/60 out back. I don't really want a tire in front shorter than the rear... discuss...
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Matt Trakker



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PostSubject: Re: Deciding on 15" tire options   Fri Feb 03, 2012 10:10 pm

Is the 275/60 going to be the height of 235/70?
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mega



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PostSubject: Re: Deciding on 15" tire options   Sat Feb 04, 2012 6:09 am

tire sizes confuse the hell outta me. I always thought the 60 or 70 wa the hight but never changed. and the 235 etc was tread size.
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GasTT



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PostSubject: Re: Deciding on 15" tire options   Sat Feb 04, 2012 7:59 am

Matt Trakker wrote:
Is the 275/60 going to be the height of 235/70?

Yes.

The 275 is the width in millimeters. The 60 is 60% of the width creating the sidewall. Both 235/70 and 275/60 are 28” diameter.
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sdstick



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PostSubject: Re: Deciding on 15" tire options   Sat Feb 04, 2012 8:03 am

mega wrote:
tire sizes confuse the hell outta me. I always thought the 60 or 70 wa the hight but never changed. and the 235 etc was tread size.

This one is pretty comprehensive

Pick your car & use the comparer option (no caddy's tho?)

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mega



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PostSubject: Re: Deciding on 15" tire options   Sat Feb 04, 2012 8:05 am

ok now i get it lol.
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Machine-De-Zine



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PostSubject: Re: Deciding on 15" tire options   Sat Feb 04, 2012 10:08 am

*
295/50 15 rears are stupid looking with 28" tall fronts, because they are only like 26.7" tall.

You said you were staying with the 7"x15" wheel, so get a good 235/70 15 tire and it WILL be the best choice, , ,

255/60 15s look bad (and are compromised) on a 7.0" wide wheel, even though it WILL mount up.
275/60 15, even worse.
I've seen 295/50 15s on 7" rims! Ridiculous in the extreme! The owner chose that combo for that "bitchin look"!

Perhaps you are willing and able to go for a wider wheel, or some other staggered wheel combo.

For example:

Front - 255/60 15 on an 8.0" x 15" wheel with 4.75 backspace @ 27.1" tall
Rear - 275/60 15 on an 8.5" x 15 wheel with 5.0" backspace @ 28" tall

Front - 235/70 15 on a 7" wheel with 4.5" backspace @ 28" tall
Rear - 275/60 15 on an 8.5" wheel with 5.0" backspace @ 28" tall

Front - 245/60 15 on a 7.5" x 15" wheel with 4.5" backspace @ 26.6" tall
Rear - 295/50 15 on a 9.5" x 15 wheel with 5.5" backspace @ 26.7" tall

Front AND rear - 235/70 15 on a 7.0" x 15 wheel with a 4.5" backspace @ 28" tall
This was the optional tire upgrade from GM on police HD 97 equipped vehicles.
_





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GasTT



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PostSubject: Re: Deciding on 15" tire options   Sat Feb 04, 2012 7:31 pm

I was hoping to use the wheels I have. But then I am limited to my options of tires. I guess I could grab a set of wheels. I can get nice wheels in 15" for short money. Tires too.

Those tires with the backspacing you suggested will fit on my Caprice with non-9c1 rear?

Also, for the 295's, why 9.5" and not 10"?
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PostSubject: Re: Deciding on 15" tire options   Sat Feb 04, 2012 7:41 pm

275/60/15 on stock wheels.


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Machine-De-Zine



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PostSubject: Re: Deciding on 15" tire options   Sun Feb 05, 2012 5:14 am

IMPALADAKID wrote:
275/60/15 on stock wheels.



WOW! I love that Caddy! Those beauties had all the good stuff, and are better looking than even the SS, just not as sporty.
They had four channel ABS, dual exhaust, lots of extra bracing for quieting rattles and shake, the list goes on and on.

I have to concede that there are some advantages to fitting "too narrow" a wheel for a given tire size. Passenger comfort; a softer (Caddy-like) ride!
So it comes down to how you drive, what type of car you drive and what you are willing to give up in performance and/or longevity.

The general tendency is for narrow wheels to move the "engineered-in" pivot point of the side wall outward toward the tread.
The side wall is thinner where engineers intended it to flex. This narrow fitment can cause localized heating in the thicker tapered sidewall area and precipitate premature tire failure.

Generally speaking, a tire on a wheel narrower than what engineers intended requires lower tire inflation pressures to avoid uneven tread-wear patterns.
You also acquire some protection from curb-rash to the wheel, having all that tire to shroud it.
Additionally you gain a lot of snow and ice traction from a fat soft tire mounted on a narrow rim width, provided there is plenty of void area between tread-blocks.

In drag racing you seek a lower tire pressure for the longer & wider foot print, softer sidewall flex, with little concern for optimizing for the best steering response.
So for the Caddy, IF you can accept a considerable reduction of tire life, steering accuracy, lateral stability and gas milage in exchange for a super smooth ride, then its the right choice.

When smoothness and comfort means much less than achieving the best possible vehicle performance from a tire, then vertical sidewalls win the day.
Passenger car tire's wheel widths are designed to be very near 90% of the actual tread width for a balanced compromise between ride comfort, vehicle performance and tire life.
Steering response is WAY better with stiffer (vertical) sidewalls and higher inflation pressures.
These are in a large way achieved by the selection of a wider wheel (within reason and that tire's design limits of course).

I believe in the philosophy of aesthetics that states [ Form Follows Function ].
The short list of primary functions that any of my cars have to fulfill would definitely be the following;
-> high performance, reliability, safety, longevity, and the economy of properly chosen equipment to serve well and live long under variously hard conditions.
My own personal expectations are so ingrained in me, that anything that has been proven to hurt the attributes that I seek in my cars, eventually has come to look "Wrong" to my eyes.
We are all different, and the choices in tires should be based on good science and sound reasoning in order to provide each of us with the best solution to our specific needs.



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GasTT



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PostSubject: Re: Deciding on 15" tire options   Sun Feb 05, 2012 11:08 am

Glen

Those tires with the backspacing you suggested will fit on my Caprice with non-9c1 rear?

Also, for the 295's, why 9.5" and not 10”?
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Machine-De-Zine



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PostSubject: Re: Deciding on 15" tire options   Sun Feb 05, 2012 9:09 pm

GasTT wrote:
Glen

Those tires with the backspacing you suggested will fit on my Caprice with non-9c1 rear?

Also, for the 295's, why 9.5" and not 10”?
*
The bubble cars have "Beaucoup" rear wheel house volume!
If you can restrain the rear axle from bushing-slop induced wayward movements, 31" tall & 12" wide tires are possible.
Our cars also suffer from inaccuracies in their chassis to body X & Y plane location, thats lateral and longitudinal.
I've been able to get them dialed-in when the chassis and/or body were not already mangled or bent.

When you say non-9C1 rear, do you mean civilian or WX3?
Wagons notwithstanding, SS rears are the only wide sedan rears. (5/8" per side)
I recommend getting the front fitment just right, then fit the rear wheel to fall in with the same fender-lip offset, remember - there is more leeway back there.
Other backspace wheels fit, but extra width wheels narrow down that range, and the ones I mentioned bring in a balanced front to rear fender proximity.

On my 9C1, I measured from the disc mounting surface: 6.625" inboard and 5.5" outside in the rear w/w, {4.875" in & 7.250" out on my WX3} Total of 12.125".
And thats minimum clearance before the first contact is made, with no frame narrowing or fender lip modifications done.
Rear tires taller than 28.5" would require extended lower rear control arms, because the forward bottom wheel lip molding is closer to the axle centerline than the rear lip.
BTW, all of this information is from personal experience. I take notes & photos, but only recently digitally, so earlier reference photos haven't been digitized for posting here.

My SS has 295/45ZR18s on 10.5 rears and 275/40ZR18s on 9.5 front wheels, 5 on 4.75" to 5 on 5" premium billet adaptors.
The tires are Nitto NT555s and there are no issues of insufficient clearance or rubbing, front or rear.
Also be aware that a 15" diameter wheel will hit the steering arm/outer tie rod over 5.250" B/S, but a 17+" dia. wheel clears. N97s are 15" x 7.0" & 4.5" B/S for your reference.
Most aftermarket "thick" front sway-bars are usually the next item rubbed by tires mounted to very deep B/S 17+" wheels.

Let me know which tire size combo you like best, tell me exactly which width rear you have and I can suggest some wheel choices for you. (No, I'm not a salesman)
N-50s (295/50 15s) are traditionally a "street drag" type tire size, what ever THAT may mean, so low inflation, fat foot prints (narrower wheels) are favored.
Most non-racing, DOT street 295/50 15s specify an 8.0"-10.0" range, so 10"x15" wheels are good. I'd do it.
-


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GasTT



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PostSubject: Re: Deciding on 15" tire options   Sun Feb 05, 2012 9:43 pm

My rear is just a civilian drum rear. I was under the impression that the 9c1 rear was more narrow than all the other sedan rears.

I like the 245/60 and 295/50 combination. I would be using an american racing wheel that is available with custom offset.

I'd like to use Firestone Firehawk Indy 500 tires. The 245/60 is not available in this tire. Although, 235/60 is. Only slightly shorter than the 295/50. 15x7 up front and 15x10 out back? Could I go 15x8 on the front with the 235/60?
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Machine-De-Zine



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PostSubject: Re: Deciding on 15" tire options   Mon Feb 06, 2012 12:34 am

GasTT wrote:
My rear is just a civilian drum rear. I was under the impression that the 9c1 rear was more narrow than all the other sedan rears.

I like the 245/60 and 295/50 combination. I would be using an american racing wheel that is available with custom offset.

I'd like to use Firestone Firehawk Indy 500 tires. The 245/60 is not available in this tire. Although, 235/60 is. Only slightly shorter than the 295/50. 15x7 up front and 15x10 out back? Could I go 15x8 on the front with the 235/60?
*
The future for continued availability on good tire choices for 15" wheels on our type cars is becoming increasingly dismal.
If you are buying tires and wheels, I would absolutely seriously consider 17 & 18" offerings.

I just tried to put together a staggered combo for you using a 295/50 15 in one brand & style, and its pretty bleak, and getting worse.
M/T, BFG, Indy 500, Cooper, Dunlop, Delta, ElDorado, and NONE of these are great tires by today's standards.
Then in a few years you need to replace one or more tires, and your size went "Disco"! (Discontinued)
In just a few short years, there will be only just a few of these sizes left, and stagger fitments will only compound your tire searching woes.

The 235 in front with a 295 out back I think looks "cheezy" on our big beautiful cars, looking like pro-street or drag-only cars.
I personally don't like that look on the street. Thats was once a popular trend, but has been thankfully dead for twenty years now.
Front skinnies are dangerous and ugly, but necessary for being competitive at professionally sanctioned drag racing events.

I never liked the N-50s anyway, it may also be too soft to be tucked that snugly in the back. It will wallow around a LOT more than my 295/45ZR18 Nittos mounted on 10.5" wheels.
So lets back up and consider your intended ride height (springs), your driving style (performance envelope expectations) and future plans for the car.
You are talking about paying for custom wheel offsets now, but an off the shelf full set of 2) 18"x 9.5"s and 2) 18"x10.5"s for roughly $125 each is not too bad.
Now you will have all four new wheels, staggered fitment, and tire availability far into the future that are WAY better, and getting improved all the time.

On the other hand, its still affordable to buy road worthy 235/70 15s that are nice looking on the car, filling up the wheel well at stock ride height.
Or, you can buy very affordable 15 x 8, 15 x 8.5 or 15 x 9.5 steel rims (or used ralleys) and put on four 255/60 15s or even L-60s (275/50 15s).
My 84 Olds 88 Bro-Ham has 15 x 8 (4.5" B/S) Centerline Telestars with Michelin 235/70 15s, and it rides and looks very nice!
-
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GasTT



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PostSubject: Re: Deciding on 15" tire options   Mon Feb 06, 2012 7:23 am

I'm not worried about future availability. I work for an independent tire dealer. All I have to do is order a few sets of these tires and let them sit around the warehouse for a while should I need them in the future. This car isn't a daily driver. It's seen about 10k miles in the past 3 years. Performance and handling is not of major concern. I'm more of a straight line acceleration/ highway type driver. I want 15" because I like the look. I like raised white letter tires. This is basically a cosmetic deal for me.
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Machine-De-Zine



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PostSubject: Re: Deciding on 15" tire options   Mon Feb 06, 2012 8:07 pm

GasTT wrote:
I'm not worried about future availability. I work for an independent tire dealer. All I have to do is order a few sets of these tires and let them sit around the warehouse for a while should I need them in the future. This car isn't a daily driver. It's seen about 10k miles in the past 3 years. Performance and handling is not of major concern. I'm more of a straight line acceleration/ highway type driver. I want 15" because I like the look. I like raised white letter tires. This is basically a cosmetic deal for me.
*
After thinking this question over some more, here's my recommendation.
Bail on the 295/50 15 rears.
For them to be stable enough laterally, they will need to be mounted on some very wide wheels, and then there would not be enough room in the wheel well.

Go with 275/60 15 Firestone Firehawk Indy 500s in back on 15" x 9" wheels with 5" backspace. 28" tall.
They are only one small step narrower than the N-50s, but will look & actually be wider due to the wider wheel you'll be using.
For the front, 255/60 15s (same tire model) on 15" x 8.5", with 4.75" or 5" backspace. 27.1" tall. This shouldn't trigger your ABS light either (769 vs 744 revs per mile)
In each case here, you will still be 0.5" less than the manufacturer's max wheel width range.

If you DO get an ABS code, you may be able to fit those 275s up front (4 tires the same) as another option.
My front 275/40ZR18s on 9.5" x 18" wheels are only 0.5" shorter @ 26.57" vs your 27.1", with no rubbing anywhere on my stock height 96 SS.

Like that you will have a mean, aggressive look, and a stable tire (won't wallow around like wide street tires tend to do on narrower wheels).
This is also a much better way to fill up the wheel well. Remember, this is a LARGE vehicle, & N-50s already look small (short) on old pony cars.
These tires I'm suggesting here are much better balanced together for a car of this size and weight.
Both of these sizes are still very likely to continue on in production (in several brands, styles & types) for the foreseeable future.

What do you have for tires and rims on the car now?, and have you had any other different sizes in the past?, then please post pics here if possible.
Also post photos of (or a link to) the wheels you intend to have made up.
-
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GasTT



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PostSubject: Re: Deciding on 15" tire options   Mon Feb 06, 2012 8:29 pm

Right now I have 235/70 Firehawk Indy 500's on what I think is a 15x7 wheel. Tires are ready for replacement.









These pics are old but they are what's on the car.

I've only had 15" wheels and tires on this car. Nothing bigger than a 235.

Not sure about what wheels I want to use yet..

If I were to go 275/60 all around, what width wheel should I run in front? Should I just stick with 15x9 all the way around? What backspacing for the front?
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Matt Trakker



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PostSubject: Re: Deciding on 15" tire options   Mon Feb 06, 2012 9:38 pm

I've been thinking about getting black Cragar Soft 8s and using my Chevy centers with the threaded lugs. I remember Anthony had them on his car and it looked awesome, they were bigger than 15s I think though.
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PostSubject: Re: Deciding on 15" tire options   Mon Feb 06, 2012 10:49 pm

GasTT wrote:
Right now I have 235/70 Firehawk Indy 500's on what I think is a 15x7 wheel. Tires are ready for replacement.









These pics are old but they are what's on the car.

I've only had 15" wheels and tires on this car. Nothing bigger than a 235.

Not sure about what wheels I want to use yet..

If I were to go 275/60 all around, what width wheel should I run in front? Should I just stick with 15x9 all the way around? What backspacing for the front?
*
Nice photography, and really beautiful car! Well worth these efforts.

Since you work in the business, you should just get 2 to begin with, two rears: 15" x 9" with 5" back space.
Your car may be able take 5.250" B/S, but not 5.5" because it will hit the steering arm/outer tie rod.
Iv'e got N97s and with 4.5" back space have nearly, but not quite an inch before contact.
Tried these these on several of my B-bodies with the same clearance results.

The strategy here is to get your rears first, and mount them up front. Keep your 28" tall 235/70 15s in the rear while testing.
And then drive around very slowly, over a wide, full range of wheel movements, stopping often to measure how close you are to rubbing.
If everything is good, your'e done, then get your rears.
If they rub the fender, then go with [235/70 15s on 8.0" x 15" w/" 5.0" B/S (@ 28" tall) <-(good)], - - or - - [255/60 15s on 8.5" x 15" and 5.0" B/S (@ 27.1" tall) <-(better)].
The manufacturer says a 9.0" wheel is the max for 255/60 15s, but it will look quite different from the rear, unless you then use 9.5" rear wheel width, also the max. recommended.
In reality, I think a 9.0" x 15" front wheel is not good, as it will aggravate the car's straight line stability due to the excessive outboard scrub radius caused by steering arm location.

Your new wheel position is going to be measurably predictable: you have 15 x 7 wheels? If they are made like the OEMs, they will have 4.5" B/S.
The new 9" wheel is 2" wider, having 0.5" more inboard and 1.5" more outboard.
If you get too close to the front outer wheel lip moulding, you will have to go with a smaller combo, because you can not move inboard any more than that.
Measure your clearance now, and add those measured increases to your current width and height.

Note: my rear tires now are 28.31" tall (11.8" wide) and my fronts are 26.57" tall (10.9" wide), yet so far I have had no ABS issues arising from that roll-out difference.
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GasTT



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PostSubject: Re: Deciding on 15" tire options   Fri Feb 17, 2012 10:55 pm

Been thinking a lot and I think I will go with 255/60 in front on a 15x8 and 275/60 out back with a 15x9 or 15x10. Rims still undecided. All this will come after I deal with it's issues. Saving my pennies.
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PostSubject: Re: Deciding on 15" tire options   Today at 5:12 am

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