On a Roll

What You Need to Know When Se­lect­ing Wheels and Tires

Street Rodder - - CONTENTS - By Ron Ceri­dono Pho­tog­ra­phy by Brian Bren­nan

Of all the el­e­ments in­volved with street rod styling, the com­bi­na­tion of wheels, tires, and stance may very well be the most crit­i­cal. Use the wrong com­bi­na­tion of rolling stock and it’s dif­fi­cult, if not im­pos­si­ble, to ig­nore and may cause all the other cool el­e­ments of the car to go un­ap­pre­ci­ated.

Al­though the look of the wheel and tire combo is im­por­tant per­for­mance is part of the pack­age as well. There are grow­ing num­bers of builders who want more rub­ber to meet the road to en­hance their car’s grip, but re­gard­less of what you’re af­ter, tra­di­tional bigs ’n’ lit­tles or the lat­est in fat and sticky low-pro­file rollers, the chal­lenge is fig­ur­ing out what will fit be­fore buy­ing wheels and tires that won’t. One of the best meth­ods to do that is with a tire-mount­ing fix­ture that Dean Liver­more, at Hot Rods by Dean uses called the Tire Mount Mate.

Avail­able from WheelWorks, this clever tool al­lows tires to be

test­fit by sim­u­lat­ing a wheel’s di­am­e­ter, width, and backspac­ing. Kits are avail­able for a va­ri­ety of ve­hi­cles, in­clud­ing eight-lug trucks, how­ever, the most pop­u­lar kit for street rod­ders sim­u­lates wheels from 14- to 20-inch di­am­e­ter up to 16.5 inches wide with up to 12 inches of backspac­ing.

Once you’ve fig­ured out what will fit in the space avail­able there is some ba­sic in­for­ma­tion about wheels you should be fa­mil­iar with be­fore mak­ing what is of­ten a sub­stan­tial in­vest­ment.

• Bolt Pat­terns

This con­sists of two num­bers, such as 5-on-4.5. The first num­ber is the num­ber of mount­ing holes; the sec­ond is the di­am­e­ter of the cir­cle the holes are laid out on. In this ex­am­ple there would be five holes in a 4.5-inch cir­cle. Some wheels will have two sets of bolt­holes, 5-on-4-.5 (of­ten re­ferred to the late Ford/Mopar pat­tern) and 5-on-4.75 (found on many Chevro­lets).

• Wheel Width

This sim­ple mea­sure­ment can be con­fus­ing. It’s the width of the wheel from bead seat to bead seat and does not in­clude the flanges that are out­side the tire.

• Di­am­e­ter

Like the width of a wheel, the di­am­e­ter is from bead seat to bead seat and does not in­clude the outer flanges on each side.

• Wheel Off­set

This is the dis­tance from the mount­ing sur­face of the wheel and the wheel’s cen­ter­line. Zero off­set means that the wheel’s mount­ing sur­face and the cen­ter­line are the same. Pos­i­tive off­set means the mount­ing sur­face is to­ward the outer edge of

the wheel. Neg­a­tive off­set means the mount­ing sur­face is to­ward the back of the wheel. (A clas­sic ex­am­ple is a “re­versed” wheel.)

• Cen­ter Reg­is­ter

Wheels must be cen­tered on the hubs—this is done by two dif­fer­ent meth­ods. With hub-cen­tric de­signs (most of­ten used with OEM steel wheels) the cen­ter hole in the wheel fits tightly on (and is sup­ported by) the hub as well as the studs. Lug-cen­tric wheels have a larger cen­ter hole than the hub (or axle pro­tru­sion) and are lo­cated by the lug nuts.

• The X-Fac­tor

The X-Fac­tor is the amount of clear­ance be­tween the wheel and the disc brake caliper. This has be­come in­creas­ingly im­por­tant with the pop­u­lar­ity of large-di­am­e­ter af­ter­mar­ket brakes.

• Lug Nut Style

There are sev­eral dif­fer­ent types of lug nuts avail­able and it is very im­por­tant to match them to the wheels be­ing used. Con­i­cal seat lug nuts are avail­able with 60- or 45-de­gree ta­per with 60 de­grees be­ing the most com­mon—they are found on most OEM and af­ter­mar­ket wheels. What’s called an ET-style lug nut also has a 60-de­gree con­i­cal seat with a short ex­tended shank to al­low for more thread en­gage­ment. Be­cause 45-de­gree lug nuts have a wider sur­face con­tact­ing the wheel some rac­ing or­ga­ni­za­tions (such as NASCAR) re­quire them.

Shank-style lug nuts, of­ten re­ferred to as mag wheel nuts, have an ex­tended por­tion that fits into straight holes in the wheel and uses flat wash­ers. When us­ing mag wheel lug nuts make sure the shanks are not so long that they bot­tom out against the hub. Also, when us­ing any lug nut with a closed end, make sure the stud does not bot­tom out in the nut, as in both cases the wheel will be loose.

Ball seat lug nuts look sim­i­lar to the con­i­cal style, but their seat­ing sur­face is rounded rather that straight— they are nor­mally found on im­port ve­hi­cles. The im­por­tant thing to re­mem­ber is the lug nuts and wheels must be com­pat­i­ble.

• In­ter­pret­ing Tire Speak

At one time about all there was on the side­wall of a tire was the brand name and size. When nu­meric tire siz­ing was used a 6.50-15 tire was 6.5 inches wide and fit a 15-inch wheel. To­day there is much more in­for­ma­tion in the tire code found on the side­walls: The first let­ter in the size code in­di­cates the in­tended use of the tire. P stands for pas­sen­ger ve­hi­cles; LT means light truck tire, ve­hi­cles tow­ing trail­ers or have 3/4- and 1-ton

load ca­pac­ity; ST stands for Spe­cial Trailer, as the name im­plies they are for trail­ers. If there’s no let­ter be­fore the first num­ber the tire is a met­ric or Euro­pean load–rated tire.

• Tire Size

Us­ing a P225/50R17 as an ex­am­ple, the P stands for pas­sen­ger car; 225 is the tire’s sec­tion width from side­wall to side­wall in mil­lime­ters. The next num­ber, 50 in this case, is as­pect ra­tio or the per­cent­age of the tire’s side­wall height com­pared to its width—50 means that the tire’s sec­tion height is 50 per­cent of the tire’s sec­tion width. The larger the as­pect num­ber, the taller the tire’s side­wall.

• Con­struc­tion

A sin­gle let­ter in­di­cates the in­ter­nal con­struc­tion of the tire: R is for ra­dial tires, D is for tires built with di­ag­o­nal plies (bias-ply con­struc­tion).

• Wheel Di­am­e­ter

This two-digit num­ber spec­i­fies what size wheel the tire fits. Load In­dex and Speed Rat­ing Ex­am­ple: P225/50R17 98H

The load in­dex and speed rat­ing come af­ter the tire size. Load in­di­cates the weight the tire can carry and is rep­re­sented by a num­ber that refers to a load in­dex chart. In this case 98 in­di­cates 1,653 pounds.

Speed rat­ings are rep­re­sented by let­ters, with the high­est rat­ing be­ing Z. At the time this rat­ing was de­vised 149 mph seemed ad­e­quate. But thanks to some su­per­cars higher rat­ings of W and Y are now avail­able (those let­ters had not been used be­fore).

• Tire ID

The U.S. De­part­ment of Trans­porta­tion (DOT) Na­tional High­way Traf­fic Safety Ad­min­is­tra­tion (NHTSA) re­quires that tires be iden­ti­fied by the let­ters DOT, fol­lowed by let­ters and/or num­bers that iden­tify the man­u­fac­tur­ing lo­ca­tion, tire size, and man­u­fac­turer’s code, along with the week and year the tire was man­u­fac­tured. Since 2000, the last four dig­its of the code in­di­cate the week and year the tire was pro­duced—the first pair rep­re­sents the week, the sec­ond pair in­di­cates the year. Tires man­u­fac­tured be­fore 2000 used a three-let­ter code at the end of the id num­bers; two num­bers to in­di­cate the week fol­lowed by a sin­gle num­ber for the year.

• Tire Grad­ing

NHTSA de­vel­oped tests to grade tires in three ar­eas:

Tread­wear: This is the wear rate of the tire com­pared to other tires of­fered by the same man­u­fac­turer, with 100 be­ing the base­line num­ber. A tire with a wear rate of 200 should last twice as long.

Trac­tion: Trac­tion grades are AA, A, B, and C (with AA be­ing the high­est grade)—they rep­re­sent stop­ping dis­tance on wet pave­ment.

Tem­per­a­ture: The tem­per­a­ture grades are A, B, and C from the low­est to the high­est and in­di­cate the tire’s abil­ity to dis­si­pate heat.

• Re­place­ment Due to Age

Over the past few years many tire shops have be­gun re­fus­ing to mount, bal­ance, or re­pair any tire that is over 6 years old. Al­though there is no law or reg­u­la­tion we have found that ad­dresses this, the rea­son given for the pol­icy is li­a­bil­ity since a num­ber of auto com­pa­nies have sug­gested that tires be re­placed af­ter six years. Iron­i­cally sev­eral ma­jor tire man­u­fac­tur­ers tell us that tires should be good for up to 10 years if they are not dam­aged.

Be­fore re­mov­ing the fix­ture and tire, the X-fac­tor was dou­blechecked. Tire clear­ance is checked at full steer­ing lock full left. 8

With the assem­bly in place and fender clear­ance ver­i­fied the wheel off­set is mea­sured. 6

Backspac­ing can be checked on the floor with the fix­ture re­moved. 7

With sup­port un­der the lower A-arms the car can be “jounced” to check fender clear­ance. 5

This is one of the four clamps that hold the tire in place. The fix­ture is ad­justed to the sug­gested width for the tire, then the beads are clamped in place. 4

With the sus­pen­sion at ride height the fix­ture is bolted to the hub and ad­justed for the di­am­e­ter of the wheel. 3

The pop­u­lar­ity of large disc brake ro­tors and calipers re­quires care­ful mea­sure­ment of the “X-fac­tor” to en­sure the wheels will clear.

The per­fect street rod stance is dif­fi­cult to de­scribe, but you’ll know it when you see it. This Ford Fair­lane was built for the Road Tour by Hot Rods by Dean. We wanted as much rub­ber un­der the Fair­lane’s fend­ers that would fit so HRBD used a Wheel...

11 Us­ing the cor­rect lug nuts is vi­tal. This vin­tage alu­minum wheel uses straight holes with flat sur­faces for wash­ers. Typ­i­cal “mag wheel” lug nuts have straight shanks. It’s crit­i­cal that the shank does not bot­tom out on the hub be­fore the wheel is...

When de­ter­min­ing the width of a wheel the mea­sure­ment is made in­side the flanges. Di­am­e­ter is also mea­sured from the tire bead sur­face not the od flange. 10

Here tire clear­ance is checked with the steer­ing at full right. 9

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