Good Wheel n Tire info!!

Travon

87PSI
Aug 12, 2010
101
7
18
Maryland
ATTENTION: These pages were created & copyrighted by Steve Parker. They reside here on MonteCarloSS.com only until we can contact Steve to get his site back up in operation.
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Tire and wheel sizes
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Here you will find some popular tire and wheel combos that members of the monte-list *are* running on their SS's.

All of the combos listed here can be done with 100% stock suspension and *will not* rub. The only problem you may encounter is that if you go with an "oversize" tire, your speedo and odometer will read improperly by a percentage of the difference between stock and aftermarket tire overall height.



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stock = 215/65 on 15x7 front and 215/65 on 15x7 rear

Front tire/wheel:

225/60 on 15x7 (stock wheel)

235/60 on 15x7 (stock wheel)

235/60 on 15x7 (bolt pattern: 5x4.74 offset: 6mm)

235/55 on 16x8 (4" backspacing)

245/50 on 16x8 (4" backspacing)

Rear tire/wheel:

225/60 on 15x7 (stock wheel)

235/60 on 15x7 (stock wheel)

245/60 on 15x7 (stock wheel)

245/50 on 16x8 (4" backspacing)

255/60 on 15x7 (stock wheel)

255/60 on 15x8 (bolt pattern: 5x4.75 offset: 19mm)

255/50 on 16x8 (4" backspacing)

275/50 on 15x9 (4" backspacing, offset: 16mm)


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Note: 215/60R15 is stock. To keep the stock ride height, you will need to either use a 235/60R15 or a 275/50R15 tire.

Here are some reference calculations:


Tire Size Dia. Variance @65 MPH 65 @ RPM Section Width
----------- -------- ------------------ -------- -------------
285/45-16 26.1" +0.25 mph 2125 11.22"
275/45-16 25.74" -0.66 mph 2150 10.83"
275/50-15 25.83" -0.23 mph 2125 10.83"
265/50-16 26.43" +1.06 mph 2100 10.43"
255/60-15 27.05" +2.52 mph 2050 10.04"
245/60-15 26.57" +1.41 mph 2100 9.65"
235/60-15 26.1" +0.25 mph 2125 9.25"
225/65-15 26.52" +1.28 mph 2100 8.86"

Stock Size For Reference:
215/65-15 26.00" 0.00 mph 2125 8.46"




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Stock MCSS wheels & tires
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Monte Carlo SS's were factory equipped with P215/65R15 Raised White letter Goodyear Eagle GTs. These tires were non-speed-rated and were NOT all-season radials. The tires were mounted on either painted steel wheels ('83-'85 SS) or Alloy aluminum wheels ('86 and up SS). Both styles were 15"x7". '86/'88 SS wheels had a 3mm negative offset and had 3 3/4" of rear backspacing. The circle bolt pattern was 5 X 4 3/4 inches.




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Tire Nomenclature
Currently there are several classifications and designations of tires. To be knowledgeble about tires, you must be familiar and understand what all of the markings mean. This is the only way to achieve the right match of tire and rim.

There are at least four systems used to identify tires:

P-METRIC
Code Schemes: W/ASCD LS & W/ACD LS
Example: 215/65HR 85H 215/65R 85H

W - Tire section width (millimeters) (ex: 215 mm)
A - Aspect ratio (percentage) (ex: 65%)
C - Construction (ex: R - radial)
D - Diameter (inches) (ex: 15 inches)
L - Load index (see chart) (ex: 85)
S - Speed rating (see chart) (ex: H)



NUMERIC SYSTEM


Code Scheme: W-D
Example: 8.25-15

W - Tire section width (inches) (ex: 8.25 inches)
D - Diameter - Rim (inches) (ex: 15 inches)





Tire Definitions and Ranges



W - The tire section width is the total width of the tire including
sidewall bulge. Do not confuse this with tread width. The tread width
(footprint/contact patch) is significantly less.
NOTE: The section width increases .2 inches for every .5 inch increase in rim
width. Please be sure to compensate for this in ALL your computations.

A - The aspect ratio is a percentage of the tire section width (W) that makes up
the tire's heigth. If the width were 215mm and the aspect ratio were 65, the
tire section heigth (sidewall) would be (65% of 215) or 139.75mm.

C - The construction is of type: R: Radial ply B: Bias-belted D: Diagonal or Bias
ply

LS - The service description consists of a load index (L) and a speed rating (S)
which is further explained below.

L - The load index ranges from 0 to 279. Passenger car tires usually range from
75 to 100. Divide the Gross Axle Weight Rating (GAWR) by two. It's usually on a
sticker located on the side of the driver's door (GAWR-FRT front) and (GAWR-RR
rear). For example, a front of 2169 and a rear of 2278 equates to 84 & 86
(minimum) respectively (2169 divided by 2 and 2278 divided by 2).


Load Index - - Load lbs./wheel- - GAWR

75------853 lbs./wheel or 1706 lbs. GAWR76------882 lbs./wheel or 1764 lbs. GAWR77------908 lbs./wheel or 1816 lbs. GAWR78------937 lbs./wheel or 1874 lbs. GAWR79------963 lbs./wheel or 1926 lbs. GAWR80------992 lbs./wheel or 1984 lbs. GAWR81------1019 lbs./wheel or 2038 lbs. GAWR82------1047 lbs./wheel or 2094 lbs. GAWR83------1074 lbs./wheel or 2148 lbs. GAWR84------1102 lbs./wheel or 2204 lbs. GAWR85------1135 lbs./wheel or 2270 lbs. GAWR86------1168 lbs./wheel or 2336 lbs. GAWR87------1201 lbs./wheel or 2402 lbs. GAWR88------1235 lbs./wheel or 2470 lbs. GAWR89------1279 lbs./wheel or 2558 lbs. GAWR90------1323 lbs./wheel or 2646 lbs. GAWR91------1356 lbs./wheel or 2712 lbs. GAWR92------1389 lbs./wheel or 2778 lbs. GAWR93------1433 lbs./wheel or 2866 lbs. GAWR94------1477 lbs./wheel or 2954 lbs. GAWR95------1521 lbs./wheel or 3042 lbs. GAWR96------1565 lbs./wheel or 3130 lbs. GAWR97------1609 lbs./wheel or 3218 lbs. GAWR98------1653 lbs./wheel or 3306 lbs. GAWR99------1709 lbs./wheel or 3418 lbs. GAWR100----1764 lbs./wheel or 3528 lbs. GAWR




S - Speed ratings (S) range fron A1 (3mph) to Z (149+mph). Passenger car
tires maximum speed ratings are as follows:


P - 94 mph U - 124 mph
Q - 100 mph H - 130 mph
R - 106 mph V - 130+ mph (w/o load indexes)
S - 112 mph V - 149 mph (w/load indexes)
T - 118 mph Z - 149+ mph (by manufacturer)


Speed rated tires usually can be repaired and retain their speed rating, although H, V, & Z rated may only have one .25 inch puncture. Any more, and the tire cannot retain the orginal speed rating.

Older tires, without speed ratings such as stock GOODYEAR EAGLE GT 215/65R15 have a rating of less than 113 mph. This is interesting since the stock computer chips allow turbo-Buicks to acheive 124-128 mph. The stock tires are considered "safe" because no-one usually maintains these speeds for any length of time. (The rating is based on a ten minute period.)

Max Load & Max Inflation


P-Metric system tires have a load range:
P - passenger (standard) usually 4-ply (35 psi)
XL - Extra load 6-ply (41-44 psi)

Alpha-Numeric and Numeric system tires use different load ranges.
B - standard 4-ply (32 psi)
C - extra load (36 psi)
D - extra load (41 psi)
LT - light truck


Ply Information

There is ply information on the tire which shows type of construction.
ex:Tread Plies: 2 Polyester + Steel + 2 Nylon
Sidewall Plies: 2 Polyester






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UTQGL - Uniform Tire Quality Grade Labeling
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Treadwear
The higher the rating, the longer the projected tread life under optimal conditions. Driving style, road conditions, alignment, rotation, and other factors can affect a tire's life expectancy. For comparison purposes, the index is a percentage grading based on 100 being average. The treadwear is rated against other tires from THE SAME manufacturer. For example, a treadware rating of 150 from company X means that tire will wear 1 & 1/2 times as well as a tire from that company with a rating of 100 given the driving conditions are constant. As another example, B.F. GOODRICH Radial T/A HR4 has a rating of 310 and B.F. GOODRICH Comp T/A HR4 Has a rating of 340. The Comp T/A HR4 should last 1.096 times as long as the Radial T/A. The actual tread-wear warranty is a more easily digestible figure that indicates the number of miles a consumer could expect from a properly maintained tire. Many tires carry a 40,000 mile warranty, which translates to an index of approximately 360.

Traction
The traction index rates STRAIGHT-LINE stopping ability on wet concrete and asphalt surfaces using the A, B, and C scale, with A being the (best) and C the (worst). Purchase decisions shouldn't be based strictly on this rating, as it doesn't take into account handling on other surfaces such as dry or snow covered pavement, nor does it rate cornering and acceleration abilities.

Temperature Rating
A rating of the tire's ability to dissipate and resist heat, on a scale of (from highest to lowest) A, B, and C. To earn the highest grade of "A", a tire must withstand a half hour run at 115 mph without failing. Like treadwear and traction index ratings, the temperature index can only be used to accurately compare within a manufacture's product line. All passenger tires must achieve a rating of C. A & B represent higher levels of performance than are required by law.

All-Season
M/S, M+S, or M&S states the tire meets the Rubber Manufacture's Association (RMA) definition for mud and snow. Current trends are the use of a "4" in the tire model's name.
NOTE: Stock GOODYEAR Eagle GTs are NOT all-season tires!

Radial Construction
They must state "RADIAL" on the tire. Radial ply construction tires comprise the vast majority of the passenger-car market.

TPC Spec
The TPC spec states the tire has met the General Motors performance specifications.

Tubeless
They must state "TUBELESS" or "TUBETYPE".

Department of Transportation
DOT XXXX XXX - "DOT" means the tire meets the Department of Transportation safety standards. The code identifies the tire manufacturer, plant, type of tire construction, and date the tire was made. The last three numbers indicate the week and the last digit of the year the tire was made.




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Wheel & Tire Formulas
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NOTE: Each tire's section width is based on a particular rim size and construction. Compensate for differences. Increase section width .2 inches for every .5 inch increase in rim width. For example, if the tire's section width is 9.14" on a 6.5" rim and is to be mounted on a 7" rim, the section width would be 9.34". Section width (sidewall flex) will vary by construction. ANY variance will affect calculations!

Radius - Diameter - Circumference

To compute the diameter of a P-Metric tire, multiply the section width by the aspect ratio (as a percentage). If necessary, divide this number by 25.4 to convert millimeters to inches. For example, a 215/65 equates to a tire height of 5.5019685 inches (215 x .65) divided by 25.4. Multiplying this by 2 for the top and bottom sidewall height and adding the rim size will get the overall tire diameter. For example, if the tire is on a 15 inch rim, it is approximately 26 inches ((5.5 x 2) + 15). The radius is half of the diameter. Multiplying the diameter by pi (3.1415927...) will get the circumference.

Tire Revolutions Per Mile



To compute the number of tire revolutions per mile, divide 20,168 by the diameter.

20168
---------------------------- = Tire Revs/Mile
(Tire Heigth X 2) + Rim Size


For a 215/65R15:

20168
---------------- = 775
(5.5" X 2) + 15


For a 255/60R15:

20168
---------------- = 747
(6" X 2) + 15



Speed

By dividing the original tire revolutions by the new tire revolutions and multiplying by the indicated speed on the speedometer, we arrive at the new actual speed.


(Orig. Tire Revs/Mile)
---------------------- X Indicated Speed = Actual Speed
(New Tire Revs/Mile)

Using the above tire sizes:

(775)
----- X 60 mph = 62 mph
(747)


Rear Axle Ratio

Changing tire diameters will also change the effective rear axle gear ratio. Divide the new tire revolutions by the original tire revolutions and multiply by the original axle ratio. For example, a turbo Buick that had 215/65s and a rear axle ratio of 3.42 (what else?) and moved to a 255/60 will net an effective ratio of 3.30.


(New Tire Revs/Mile)
--------------------- X Orig. Axle Ratio = Effect. Axle Ratio
(Orig.Tire Revs/Mile)

(747)
----- X 3.42 ratio = 3.30 ratio
(775)

As you can see, this will theoretically raise the top speed of the vehicle but
hurt its acceleration.

To regain the original effective ratio with the new tires, a 3.55 ratio is
required.

(Orig.Tire Revs/Mile)
--------------------- X Orig. Axle Ratio = Equiv. Axle Ratio
(New Tire Revs/Mile)



(775)
----- X 3.42 ratio = 3.55 ratio
(747)


Maximum Speed

To calculate the maximum speed of a vehicle, take:

Overall Tire Diameter X Achieved Engine RPM (redline)
------------------------------------------------------ = Max Speed
Differential Ratio X Top Gear Ratio X 336

26" X 5250
----------------- = 177 mph
3.42 X 0.67 X 336

This differs from actual speed. A stock turbo-Buick's actual top speed is in the
152 to 162 mph range. The aerodynamics on these cars are nothing to write home
about.


Lateral Acceleration

To measure lateral acceleration (cornering ability), use:

1.227 X R
g = -----------
(T X T)

R is the radius of the turning circle and T is the time (in seconds) required for
one lap. Stock turbo-Buicks usually can achieve .79 to .80g.



Tire Mixing

It is always best to have all four tires the same size and construction. If mixing is necessary, install radials on the rear and non-radial on the front and/or wider tires on the rear than front. Never mix constructions and/or sizes on the same axle.

"Plus One / Plus Two Sizing Concept"

This allows vehicles to use lower aspect ratio (lower profile) tires by increasing wheel rim diameter (+1/+2 inches), rim width, and tread width to gain handling and traction. Choose larger diameter tire which retains revs/mile and load capacity.

Rim Width Recommendations

Where ranges are specified, V & H speed rated tires require and can accomodate a wider rim. Check with specific manufacturer!

50-Series

(P)195/50xR15 5.5 - 7.5"
(P)205/50xR15 5.5/6.0 - 8.0"
225/50xR15 6.5 - 9.0"
P245/50xR15 6.5 - 9.5"
P265/50xR15 7.0/7.5 - 10.0-10.5"
P275/50xR15 7.0 - 11.0"
* P285/50xR15 7.5 - 11.0"
P295/50xR15 7.5 - 11.0-11.5"
* P295/50xR15 8.0 - 11.5"

60-Series

195/60xR15 5.0 - 7.5"
205/60xR15 5.5 - 8.0"
215/60xR15 5.5 - 8.5"
225/60xR15 6.0 - 9.0"
* 225/60xR15 6.0 - 8.0"
(P)235/60xR15 6.0 - 9.0"
*(P)235/60xR15 6.0 - 8.0"
P245/60xR15 6.5 - 9.5"
(P)255/60xR15 6.5 - 10.0"
*(P)255/60xR15 6.5 - 9.0"
*(P)265/60xR15 7.0 - 10.0"
P275/60xR15 7.0 - 11.0"

65-Series

215/65xR15 5.5 - 8.0"

(P)- same for passenger and non-passenger tires
/ - denotes manufacturer model construction variance
* - denotes tire designation conversion estimates computed
from the Tire and Rim Association Inc.

NOTE:Within a rim range, a middle width should be used for normal driving
and a wider rim width should be used if improved handling is preferred.



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Additional information can be found using the following links:

Tire Size Change Calculator (Todd Day)




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UNDERSTANDING WHEEL TERMINOLOGY

The following is a list of defined terms which need to be understood before aftermarket wheels can be intelligently purchased.

RIM WIDTH - The distance between bead mounts (where the tire attaches to the rim)

CENTERLINE - Half of the rim width (center)

OFFSET - The distance from the centerline to the hub mount pad (where the wheel attaches to the hub)

POSITIVE OFFSET - Centerline is outside of hub mounting pad (increases vehicle track)

NEGATIVE OFFSET - Centerline is inside of hub mounting pad (decreases vehicle track)

Note: Using wheels with greater negative offset than stock can increase strain on wheel bearings and spindles. Inspect more frequently. Be sure to check clearance with frame and inner fender UNDER CORNERING SITUATIONS!

REAR SPACING / REAR BACKSPACING / BACKSPACING
The distance from the inner edge of the wheel to the hub mount pad

Note: Sometimes the distance from the outer edge of the wheel to the hub mount pad is referred erroneously to as offset. BE CAREFUL!

BOLT PATTERN:
- Number of lugs
- Bolt Circle - The diameter of the imaginary circle which intersects the centers of the lug holes.


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GENERAL WHEEL FACTS

Look for the lighest weight wheel (least unsprung weight requiring least energy to get them moving) yet having the strength required by your type of driving. Brake cooling fins are a plus.

Steel:(sheet metal rolled rim welded to a stamped center)
Pluses: inexpensive, very strong, many sizes & offsets
Minuses: heavy, not much lateral (cornering) support

Aluminum:(usually light alloy)
Pluses: fairly light, fairly strong, improves handling, fairly inexpensive
Minuses: can crack or break them more easily than steel, fewer sizes and offsets than steel

Cast:
Low-pressure: inexpensive, more prone to damage
High-pressure: more strength
High-counter-pressure: more expensive, more strength
Rolled,Stamped: common
Forged: ultimate strength

Magnesium: (aluminum with some magnesium)
Pluses: very light
Minuses: Corrodes easily and requires constant care, expensive, not recommended for everyday driving

Usually the more pieces (1,2,3-piece) there are to a wheel, the greater its strength and price. One piece wheels accept wider tires for improved traction and handling.

BALANCING

There are three ways to balance a wheel: static (bubble), dynamic (spin) and on the car spin. Bubble balancing is an older method. Spin balancing is done with a machine which electronically marks the wheel for balancing. On-the-car spinning is the most precise because the car spins the wheel while mounted and a strobe light marks the wheel for balancing. The weight of the brake drum and rotor is included.
 
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Reactions: JToups386

longball

I fought the lawn...
Apr 10, 2009
1,466
104
63
Delmar, NY
just tried a pair of 275 60R 15's today. Passenger side rubbing bad on frame, driver side has inch to spare! Common problem on GN's
Next ten posters will tell you they fit perfect on their cars. And they do! Go figure. Try them and see how they work on your car.
 

ThebigbadWolF

Member
Jun 26, 2013
72
2
8
33
La Puente
good ol gm and body fitment on the frame, you should be able to shift your frame, its what I had to do on my bbody .... thanks for the info
 

Carl Ramsey

Member
Dec 3, 2013
58
6
8
75
What kind of street tire pressures are ya'll running with 235/60-15 tires on stock 15x7 Regal Turbo wheels?
 

Buick_GN_Man

New Member
Jul 8, 2014
6
0
1
50
I just bought the aluminum replica wheels and the front are 15x8 and the rear are 15x10.....what size tire should I use on rear? I want to go with Mickey's

Thank you
 

XracerX

First Methanol Kits
On stock 15x7 rims, I run 26psi on 235-60-15 bf goodrich compTA's in the rear, on the street, and I have done the same at the track in the past with good results. I found that 32psi was wearing the center of the tire quicker.
 

e-brake

The Dirty One
Apr 18, 2007
23
1
3
I just bought the aluminum replica wheels and the front are 15x8 and the rear are 15x10.....what size tire should I use on rear? I want to go with Mickey's

Thank you
What backspacing is your 10" wheel and what the cars gonna be doing street driving and how much track time is it gonna see and is your car lowered any ?
 

joed

Member
Mar 6, 2002
152
7
18
Buffalo, NY
ttt
This is getting old but I want to chime in here. I'd really like to pick up a set of 15 x 10 convo pros with 5 inch BS. Is it possible to run these with a small spacer (7/32-1/4" is the max I'm comfortable with), no frame notch and no lip roll? Was going to use 275 60 15 Mickey ET Streets. ANYONE running 15 x 10 5" BS in this set up no mods to the car? These tires work great on my old stock T wheels, but really love the Convo's!
I have air bags if needed, otherwise bilsteins, stock suspension.
Thanks,
Joe
 

pacecarta

MAGNA
Staff member
Aug 1, 2003
9,039
736
113
RIP racewaypark, NJ
you will need longer lug studs because you will need more spacer to fit that tire on a 10w x 5BS rim , about 1/2"
theres no issue running a thin vs thick spacer just dont run more than one and make sure the threads have enough engagement in the lug nut
, also be aware the convos are shank style mounting and require the short shank lug nuts

with that spacer you will have the tire off the frame but rolling the lips will depend on your ride height and issue will be specifically at the rear around 2 oclock position where the qurter panel curves back in
 

joed

Member
Mar 6, 2002
152
7
18
Buffalo, NY
you will need longer lug studs because you will need more spacer to fit that tire on a 10w x 5BS rim , about 1/2"
theres no issue running a thin vs thick spacer just dont run more than one and make sure the threads have enough engagement in the lug nut
, also be aware the convos are shank style mounting and require the short shank lug nuts

with that spacer you will have the tire off the frame but rolling the lips will depend on your ride height and issue will be specifically at the rear around 2 oclock position where the qurter panel curves back in
Great info, thank you!
 

jiho2

Sporadic Poster
Apr 4, 2004
391
15
18
Redding, CA greater metro
The tires were mounted on either painted steel wheels ('83-'85 SS) or Alloy aluminum wheels ('86 and up SS). Both styles were 15"x7". '86/'88 SS wheels had a 3mm negative offset and had 3 3/4" of rear backspacing.
Where does this stuff come from?

The gnttype.org site says Buick 15x7 wheels had 3 mm negative offset, and steel wheels had 4" backspace while aluminum had 3.75".

None of this adds up. On a 7" rim, 4" backspace equates with ZERO offset, and 3.75" backspace equates with -6.35 mm offset.
 

hotairgnx548

hotairgnx548
Apr 7, 2010
436
28
28
bowling green ky
just tried a pair of 275 60R 15's today. Passenger side rubbing bad on frame, driver side has inch to spare! Common problem on GN's
Next ten posters will tell you they fit perfect on their cars. And they do! Go figure. Try them and see how they work on your car.
what back space 275x60 mt street radial?
 
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