British
Motoring

Winter 2004/2005

Table of Contents

Tire
& Wheel Plus-Sizing

Oversized rims for aesthetics and
performance

Bigger
Brakes

Modern technology increases MG and
Triumph stopping power

British
Value Guide: Sprite & Midget

Affordable Brit fun-fests

Cover
Car: Clamshell TR3A

A professor's daily-driver TR3A

Car
Show Spectacular

British car meets attract enthusiasts
nationwide

Classic
Car Insurance

Choosing the best coverage for your
sportscar

2004
Auction Action

British sportscar values continue to
rise

Heit
Of Healeydom

Jim Heit gives a '63 BJ7 the concours
treatment

Editorial

Reader
Letters

Reader's
Cars

News

Hot
Products

Tech
Q&A

Car
Mart Classifieds

Events
Calendar

On The
Cover:

Dr. Noble Eisenlauer built his "poor man's Jag" to be a
dependable daily driver. Main cover image and Contents photo by Andrew
Schear; cover inset courtesy Noble Eisenlauer.

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Tire & Wheel

Plus Sizing

Upgrading Wheels And Tires For Fashion And Performance

By Kelvin Dodd

Moss Motors offers Panasport wheels for
classic style and performance.

Plus-size fitments are available for many MG and TR applications (TR6 +2
shown).

If concours-quality restoration is your thing, or you believe
that what the factory offered is sacrosanct, then this article is not for
you. If, however, you are open to change and are interested in improving
the looks and handling of your car, then read on.

There are two primary
reasons to upgrade wheels from their original sizes: increased
performance and visual impact. Obviously, the intent of any change is to
get the most out of your car without breaking your budget or creating
more problems than you already have. As in any modification, a balance
between cost, performance, and drivability must be determined, based on
each individual’s needs. This article will broadly cover some of the
positive and negative aspects of wheel and tire changes.

Let’s Put Some Rubber

On The Road!

When most of our
classic cars were new, the factory wheels and tires were sufficient for
the vehicles’ anticipated performance and to define their looks.
Nowadays, that original look may be dated, and the performance
expectations have increased to keep up with current trends of high-speed
stability and cornering. I’m a firm believer in skinny tires sliding
around mountain curves: For me, the “new” sport of
sport-compact “drifting” was pioneered by the MGs, Triumphs,
and Healeys during the street races and rallies of the ’50s. But
this type of excitement at low speeds may not be everybody’s cup of
tea, particularly during rush hour.

Today, the many
available wheel and tire options offer increased stability and safety for
performance-minded drivers, or the choices may be merely adequate for
those keeping up with modern iron on American freeways. Changing to a
wider wheel allows the use of wider, lower-profile tires, which

generally
have far superior handling characteristics compared to the original-sized
tires. Typically, increasing the original rim width by 1” will
allow the use of a slightly wider 70- or 65-series tire, the closest
sizes to the original 82-series (which were the only factory-offered
tires with any kind of performance pretensions). Note that the TR6 and
MGB Limited Edition were both equipped with more modern wider wheels
from the factory.

Some Popular First-Step

Performance Upgrades

CAR

ORIG.
WHEEL

ORIG. TIRE

UPGRADE WHEEL

UPGRADE TIRE

Spitfire/Midget

4"

155-13

5"

175/70/13

MGB

4.5-5"

165-14

5.5"

185/70-14

195/65-14

MGA,
TR4,

A-H

4"

165-15

5.5"

195/65-15

A Quick Note On

Tire Sizing

Modern tires are
listed in Metric sizes. The first group indicates the nominal width of
the tire, called the section width. The second group is the aspect ratio,
which gives the height of the sidewall as a percentage of the width; this
is also referred to as the profile of the tire. So, 70-series tires have
taller sidewalls than 50-series sizes. Modern performance tires are
generally only available in low-profile 70-series and lower aspect
ratios.

Even these minor
upgrades can cause

fit problems with the limited clearance in narrow wheelwells.
Correct-offset wheels must be used to ensure that the tire is centered
in the wheelwell. Generic wheels and older American “Mag”

wheels often have the incorrect offset

and will cause fitment problems, even with stock tire sizes.

How To Measure

Wheel Offset

1. Find the overall width of
the wheel. Divide this width in two to give the centerline depth.

2. Lay a straightedge across the inner rim of the wheel.
Measure from the straightedge to the mounting rim of the wheel.

3. Subtract the centerline depth from the mounting rim depth.
This gives the offset, which is now usually designated in
millimeters.

Positive offset
indicates that the hub center (mounting surface) is toward the outside of
the car; negative offset indicates that the hub center is closer to the
brake drum.

By
keeping the wheel centered in the wheelwell, there is less chance of
the wider tires fouling the inner fender, suspension components, or
outer fender—this is most important with the narrow rear
fenderwells of most British cars. For street driving where there is
likely to be a lot of suspension and body

Here are some typical
offsets necessary to keep the wheel centered for popular British
sportscars:

Typical Wheel Offsets

Sprite/Midget: +20mm

MGA/MGB: +22mm

TR2-TR6: +6mm

TR7-TR8: +15mm

Spitfire: +20mm

movement,
it is a good idea to stay conservative on width. Otherwise, the smell of
burning rubber and the sounds of tire-rub are going to accompany any spirited
driving. Make it a point to do your test-driving with your spouse or
significant other in the car. This way, you won’t experience the
unpleasant surprise of their added weight causing the tires to rub.

If you want that
maximum-rubber, road-racer look, be aware that most racecars have had
some radical surgery and are often fitted with stiffer springs and
panhard rods or other axle locators to ensure that suspension movement is
limited. You can’t have the same look and performance without making
the same sacrifices.

What Are Some Of

The Pitfalls?

Sprite/Midget: The square-arch rear-fender cars have very
restricted wheelwells. Even a 165-section tire is probably going to rub
on the back under hard cornering. The round wheel-arch cars have much
less of a problem, and 5.5” wheels can be fitted with wide tires
as long as the springs do not allow the tire to contact the fender lip.
This led to many a Bugeye that looked like it got mated to a
steamroller. Perhaps Austin moved to the square wheel arches
specifically to prevent Americans from fitting Chevy Vega wheels with
fat, wide-oval tires to their cars.

Austin-Healey: Big Healeys’ wheelwells on the BN2 onward are
wide open. Their rear suspension has limited movement, which allows
fitting wider wheels and tires without major rubbing problems. However,
overly wide tires can spoil the clean lines of the car when
negative-offset wheels are installed, which push the tire edge past the
fender lip. BN1 fenders are very tight, so wider tires are not advised.
On all models, check fender clearance.

MGB: The
rear fender lip on early cars and lowered late cars is at the widest
point of the tire, so tire bulge can be an issue. Raising or lowering
the suspension may allow extra clearance, but suspension travel can
cause clearance issues, particularly on the left-hand side of the car.
The inner bumpstop structure and front swaybar can cause clearance
issues for wheels that have too much positive offset. Under hard cornering,
the rear axle will move sideways, aggravating clearance problems. On
this car it is very important to have the wheel centered in the well,
as suspension travel and axle movement can be major problems. Minor
fender clearance issues can be addressed by rolling or grinding the
rear fender lip.

MGA: Like
the Healey, the rear wheel arches are open and can accommodate tires up
to 195 cross-section without problems.

TR2-TR4A: Fender clearance is an
issue, and a wheel with less positive offset is required to clear the
front brake calipers. This restricts the maximum wheel width.

TR250-TR6: Again, a less
positive-offset wheel is required to clear the front brake caliper;
fender clearance is improved and tires up to 205 cross-section can be
installed as long as the car is not significantly lowered. Rear-fender
clearance can be a problem on lowered cars.

TR7/TR8: A positive-offset wheel is required, but the
wheelwells are quite spacious. 205/60-13 tires will fit on the original
factory alloy wheels without any clearance problems.

Spitfire: Open wheelwells allow the use of 5.5” wheels.
These can be mounted with 185/70 series tires, but they may stick out
beyond the fenders.

Plus-Size Wheel Options

One way to increase
the availability of high-performance tires is to increase the diameter
of the wheel, which allows the use of lower-profile tires while still
maintaining the correct overall tire diameter. Only baseline modern
vehicles are equipped with 13" and 14" wheels, so high-performance
tire availability in these sizes is very limited. By increasing rim
diameter one inch (+1) or even two inches (+2), the availability of
lower-profile high-performance tires becomes much greater. In some
cases, larger-diameter wheels allow the use of wider tires because the
tires’ sidewalls don’t flex as much, so clearance under load
may be greater.

MGB:

An inch-larger wheel allows the use of high-performance low-profile
tires without compromising looks and performance. A popular performance
option for the 14” wheel is the 195/60-14 tire, which has a much
smaller diameter than stock. This reduces the overall gear ratio and
does not fill the wheelwell from front to rear.

MGB Plus Sizing

STOCK WHEEL DIAMETER: 14”

Typical Tires: 165/80-14

(diameter 619.6 mm)

185/70-14 (diameter 614.6 mm)

+1 WHEEL DIAMETER: 15”

Tire Choices: 185/65-15

(diameter 621.5 mm)

195/60-15 (diameter 615.0 mm)

There may be clearance problems with this

width of tire on some wheels.

+2 WHEEL DIAMETER: 16”

Tire Choices: 195/55-16

(diameter 620.9 mm)

205/50-16 (diameter 611.4 mm)

This width of tire could only be fitted to a car

with modified rear fenders and some type of axle

location device such as a panhard rod.

TR6:

Moving up an inch in diameter allows the use of a wider wheel due to
increased suspension clearance. Note that the only available 15”
performance tire has a much smaller diameter than stock.

TR6 Plus Sizing

STOCK WHEEL DIAMETER: 15”

Typical Tires: 185/80-15

(diameter 677 mm)

Performance Alternative: 195/65-15

(diameter 634.5 mm)

+1 WHEEL DIAMETER: 16”

Tire Choice: 205/60-16

(diameter 652 mm)

TR7/TR8:

The look of the “wedge” is really improved with more modern
tire and wheel combinations. This “shape of things to come”
really was ahead of its time and looks dated mainly due to the small 13”-diameter
wheels. A number of sticky 205/60-13 tires are on the market, but
increasing wheel diameter gives the car a whole new image.

TR7/TR8 Plus Sizing

STOCK WHEEL DIAMETER: 13”

Typical Tires: 185/70-13

(diameter 589.2 mm)

Performance Alternative: 205/60-13

(diameter 576.2 mm)

+1 WHEEL DIAMETER: 14”

Tire Choices: 185/60-14

(diameter 577.6 mm)

195/60-14 (diameter 589.6 mm)

RECOMMENDED +1

205/55-14 (diameter 586 mm)

Not many
tire options available

+2 WHEEL DIAMETER: 15"

Tire Choices: 185/55-15

(diameter 584.5 mm)

195/50-15 (diameter 576.0 mm)

205/50-15 (diameter 586 mm)

Recommended
+2 size

What If I Have Wire Wheels?

Although the classic
wire-wheel crowd doesn’t have as many performance options, they
shouldn’t feel left out. Here are some suggestions that will get you
going with even more style.

Spline-Drive Alloy
Wheels: An
expensive option, but the best alter-native to converting to bolt-on
wheels for maximum strength and a look that shouts CLASSIC PERFORMANCE!

Clearance is a major
issue as the 13”, 14”, and 15” spline-drive wheels are
5.5” wide and there must be enough clearance to the outer fender for
the wheel to be removed. Just because a tire fits the rim doesn’t
mean you won’t need a body hammer and cutting torch to remove the
wheel. A very tasty combination for the MGB is a +1 package of a 15”
spline-drive wheel and a 185/65-15 tire. This will clear on most cars;
the larger 195/60-15 will likely rub under hard cornering.

Wire Wheel
Options: The
first option is to look at the factory racing history and see if a wider
wheel was available as an option. In the case of the MGB, the factory
offered a 5.5” 72-spoke wire wheel, which has the correct offset to
handle larger rubber without clearance problems.

Most early cars
originally equipped with 48-spoke 15x4 wheels can be easily upgraded to
60-spoke 15x4.5 wheels or even the 15x5 72-spoke wheel originally
specified for the MGC. The exception is the Austin-Healey, with front
2” drum brakes: Where 60-spoke wheels foul the brake drum, the wider
MGC wheels will fit without a problem.

The 72-spoke 15x5.5
wire wheel was originally fitted to the TR6 and the necessary reduced
offset may cause tire-rubbing on the outer fender of cars originally
fitted with 48- and 60-spoke wheels.

Center-lace wheels
are available in 15x5.5 for the small sportscar hub and also for the
larger Jaguar hub. These wheels look stunning, but also have a
much-reduced offset. So, outer fender clearance must be carefully
checked. The unobstructed rim was a highlight of the AC Cobra, so these
wheels are often called “Cobra” wheels and look stunning on a
TR250 or TR6.

Tires and wheels are
one of the most popular topics for discussion, and I hope that this
article may clear up some of the questions about possible fitments. Each
car is different, so always check clearance before allowing a tire to
become damaged and unsafe. If you are looking for the ultimate in wide
rubber, be ready to do some body modifications; if in doubt, stay
conservative and minimize headaches. The difference in handling between
one tire size to the next may be insignificant compared to the problems
caused by tire-rub when cornering.