flat tire DAEWOO LACETTI 2004 Service Repair Manual
[x] Cancel search | Manufacturer: DAEWOO, Model Year: 2004, Model line: LACETTI, Model: DAEWOO LACETTI 2004Pages: 2643, PDF Size: 80.54 MB
Page 5 of 2643

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TABLE OF CONTENTS
Section 0B General Information
Section 1 Engine
Section 1A General Engine Information
Section 1C1 1.4L/1.6L DOHC Engine Mechanical
Section 1C2 1.8L DOHC Engine Mechanical
Section 1D Engine Cooling
Section 1E Engine Electrical
Section 1F Engine Controls
Section 1G Engine Exhaust
Section 2 Suspension
Section 2A Suspension Diagnosis
Section 2B Wheel Alignment
Section 2C Front Suspension
Section 2D Rear Suspension
Section 2E Tires and Wheels
Section 3 Driveline/Axle
Section 3A Automatic Transaxle Drive Axle
Section 3B Manual Transaxle Drive Axle
Section 4 Brakes
Section 4A Hydraulic Brakes
Section 4B Master Cylinder
Section 4C Power Booster
Section 4D Front Disc Brakes
Section 4E1 Rear Disc Brakes
Section 4E2 Rear Drum Brakes
Section 4F Antilock Brake System
Section 4G Parking Brake
Section 5 Transmission/Transaxle
Section 5A1 ZF 4HP16 Automatic Transaxle
Section 5A2 AISIN Automatic Transaxle
Section 5B Five-Speed Manual Transaxle
Section 5C Clutch
Section 6 Steering
Section 6A Power Steering System
Section 6B Power Steering PumpSection 6C Power Steering Gear
Section 6E Steering Wheel and Column
Section 7 Heating, Ventilation, and Air
Conditioning (HVAC)
Section 7A Heating and Ventilation System
Section 7B Manual Control Heating, Ventilation,
and Air Conditioning System
Section 7D Automatic Temperature Control HVAC
Section 8 Restraints
Section 8A Seat Belts
Section 8B Supplemental Inflatable Restraints
(SIR)
Section 9 Body and Accessories
Section 9A Body Wiring System
Section 9B Lighting Systems
Section 9C Horns
Section 9D Wipers/Washer Systems
Section 9E Instrumentation/Driver Information
Section 9F Audio Systems
Section 9G Interior Trim
Section 9H Seats
Section 9I Waterleaks
Section 9J Windnoise
Section 9K Squeaks and Rattles
Section 9L Glass and Mirrors
Section 9M Exterior Trim
Section 9N Frame and Underbody
Section 9O Bumpers and Fascias
Section 9P Doors
Section 9Q Roof
Section 9R Body Front End
Section 9S Body Rear End
Section 9T1 Remote Keyless Entry and Anti–Theft
System
Section 9T2 Immobilizer Anti–Theft System
Page 10 of 2643

GENERAL INFORMATION 0B – 3
DAEWOO V–121 BL4
Automatic Transaxle
Application1.4L DOHC1.6L DOHC1.8L DOHC
Maker–AISINZF
Type or Model–81–40LE4HP16
Gear Ratio :
1st
2nd
3rd
4th
Reverse–
–
–
–
–2.875:1
1.568:1
1.000:1
0.697:1
2.300:12.719:1
1.487:1
1.000:1
0.717:1
2.529:1
Final Drive Ratio–3.750:13.945:1
Oil Capacity–5.77±0.2L (6.1±0.2 qts)6.9±0.2L (7.3±0.2 qts)
Brake
Application1.4L DOHC1.6L DOHC1.8L DOHC
Booster Size :
Single
Dual241.3 mm (9.5 in.)
177.8 and 203.2 mm
(7 and 8 in.)
Master Cylinder Diameter22.22 mm (0.875 in.)
Booster Ratio5.5 : 1
Front Brake :
Disc Type
Disc SizeVentilated
256 mm (10 in.)
Rear Brake (Drum) :
Drum Inside Diameter
Wheel Cylinder Diame-
ter200 mm (7.9 in.)
20.64 mm (0.813 in.)
Rear Brake (Disc) :
Disc Type
Disc SizeSolid
258 mm (10.2 in.)
Fluid Capacity0.5L (0.5 qts)
Tire and Wheel
Application1.4L DOHC1.6L DOHC1.8L DOHC
Tire Size195/55R15
Standard Wheel Size6Jx15 (Steel)
Optional Wheel Size6Jx15 (Alloy)
Inflation Pressure at Full
Load30 psi (207 kPa)
Page 18 of 2643

GENERAL INFORMATION 0B – 11
DAEWOO V–121 BL4
Chassis and Body
Maintenance ItemMaintenance Interval
Kilometers or time in months, whichever comes first
x 1,000 km1153045607590105120
x 1,000 miles0.6918273645546372
Months–1224364860728496
Interior air filter (A/C)RRRRRRRR
Exhaust pipes & mountingsIIIIIIII
Brake/Clutch fluid (1) (4)IIRIRIRIR
Front brake pads and discs(3)IIIIIIII
Rear brake pads & discs or drums and
linings (3)IIIIIIII
Parking brakeIIIIIIIII
Brake line and connections (Including
booster)IIIIIIII
Manual Transaxle Oil *(1)IIIIIIII
Automatic transaxle fluid *(1) (5)IIIIIIII
Tighten chassis and underbody bolts
and nutsIIIIIIII
Tire condition and inflation pressureIIIIIIIII
Wheel alignment (2)Inspect when abnormal condition is noted
Steering wheel and linkageIIIIIIII
Power steering fluid & lines* (1)IIIIIIIII
Drive shaft bootsIIIIIIII
Seat belts, buckles and anchorsIIIIIIII
Lubricate locks, hinges and hood
latchIIIIIIII
Chart Symbols:
I – Inspect and if necessary correct, clean, replenish, or adjust.
R – Replace or change:
(1) Refer to Recommended Fluids And Lubricants.
(2) And if necessary, rotate and balance wheels.
(3) More frequent if operated under severe conditions: short distance driving, extensive idling, frequent low–speed oper-
aion in stop and go traffic, or driving in dusty conditions.
(4) Change the brake/clutch fluid every 15,000 km (9,000 miles), if the vehicle is mainly driven under the following severe
conditions: driving in hilly or mountainous terrain, or towing a trailer/caravan frequently.
(5) 1.8 DOHC model (ZF 4HP16 Automatic Transaxle): Change automatic transaxle fluid every 60,000 Km (36,000 miles)
if the vehicle is mainly driven under any of the following severe conditions:
S In heavy city traffic where the outside temperature regularly reaches 32°C (90°F) or higher, or
S In hilly or mountainous terrain, or
S When doing frequent trailer towing, or
S Uses such as taxi, police or delivery service.
Page 902 of 2643

SECTION : 2A
SUSPENSION DIAGNOSIS
TABLE OF CONTENTS
DIAGNOSIS2A–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General Diagnosis 2A–1. . . . . . . . . . . . . . . . . . . . . . . . . Torque Steer 2A–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tapered Roller Bearing 2A–6. . . . . . . . . . . . . . . . . . . . .
DIAGNOSIS
GENERAL DIAGNOSIS
Problems in the steering, the suspension, the tires, and
the wheels involve several systems. Consider all systems
when diagnosing a complaint. Some problems, such as
abnormal or excessive tire wear and scuffed tires, may be
the result of hard driving. Always road test the vehicle first.If possible, do this road test with the customer.
Proceed with the following preliminary checks. Correct
any substandard conditions.
Preliminary Checks
ChecksAction
Inspect the tires for improper pressure and uneven wear.Inflate the tires to the proper pressure.
Inspect the joint from the steering column to the steering
gear for loose connections or wear.Tighten the intermediate shaft pinch bolts. Replace the in-
termediate shaft as needed.
Inspect the front and the rear suspension, the steering
gear, and the linkage for loose or damaged parts.Tighten the front and the rear suspension. Tighten the
steering gear mounting bracket bolts. Tighten the coupling
flange pinch bolts. Replace the front and the rear suspen-
sion as needed. Replace the steering gear as needed. Re-
place the intermediate shaft as needed.
Inspect for out–of–round tires.Perform a free runout test. Match–mount the tires.
Inspect for out–of–balance tires, bent wheels, and worn or
loose wheel bearings.Balance the wheels. Replace the wheels. Replace the
wheel bearings.
Check the power steering pump serpentine belt tension.Tighten the power steering pump serpentine belt.
Inspect the power steering system for leaks. Check the
power steering fluid level.Repair any leaks. Perform a power steering gear test. Add
power steering fluid.
Car Lead/Pull
ChecksAction
Inspect for mismatched or uneven tires.Replace the tires.
Inspect for a broken or a sagging spring.Replace the spring.
Inspect for a radial tire lateral force.Check the wheel alignment. Switch the wheels. Replace
the tires as needed.
Check the front–wheel alignment.Align the front wheels.
Inspect for an off–center steering gear.Reseat the pinion valve assembly. Replace the pinion
valve assembly as needed.
Inspect for front–brake dragging.Adjust the front brakes.
Page 903 of 2643

2A – 2ISUSPENSION DIAGNOSIS
DAEWOO V–121 BL4
Abnormal or Excessive Tire Wear
ChecksAction
Check the front–wheel and the rear–wheel alignment.Align the front and the rear wheels.
Inspect for excessive toe on the front and the rear wheels.Adjust the toe on the front and the rear wheels.
Inspect for a broken or a sagging spring.Replace the spring.
Inspect for out–of–balance tires.Balance the tires.
Inspect for worn strut dampeners.Replace the strut dampeners.
Check for a failure to rotate tires.Rotate the tires. Replace the tires as needed.
Check for an overloaded vehicle.Maintain the proper load weight.
Inspect for low tire inflation.Inflate the tires to the proper pressure.
Scuffed Tires
ChecksAction
Inspect for incorrect toe on the front and the rear wheels.Adjust the toe on the front and the rear wheels.
Inspect for a twisted or a bent suspension arm.Replace the suspension arm.
Wheel Tramp
ChecksAction
Inspect for an out–of–balance tire or wheel.Balance the tire or the wheel.
Inspect for improper strut dampener action.Replace the strut dampeners.
Shimmy, Shake, or Vibration
ChecksAction
Inspect for an out–of–balance tire or wheel.Balance the tire or the wheel.
Inspect for excessive wheel hub runout.Measure the hub flange runout. Replace the hub as need-
ed.
Inspect for excessive brake drum or brake rotor imbal-
ance.Adjust the brakes. Replace the brake rotor or the brake
drum as needed.
Inspect for worn tie rod ends.Replace the outer tie rods.
Inspect for wheel trim imbalance.Balance the wheel.
Inspect for a worn lower ball joint.Replace the lower ball joint.
Inspect for excessive wheel runout.Measure the wheel runout. Replace the wheel as needed.
Inspect for excessive loaded radial runout on the tire and
wheel assembly.Match–mount the tire and wheel assembly.
Hard Steering
ChecksAction
Check the steering gear preload adjustment.Perform a rack bearing preload adjustment.
Check the hydraulic system. Test the power steering sys-
tem pressure with a gauge.Replace the seals and the hoses as needed.
Inspect for binding or catching in the steering gear.Lubricate the steering gear. Repair or replace the steering
gear as needed.
Inspect for a loose steering gear mounting.Tighten the steering gear mounting bracket nuts.
Page 909 of 2643

2B – 2IWHEEL ALIGNMENT
DAEWOO V–121 BL4
DIAGNOSIS
TIRE DIAGNOSIS
Irregular and Premature Wear
Irregular and premature tire wear has many causes. Some
of them are incorrect inflation pressures, lack of regular
rotation, poor driving habits, or improper wheel alignment.
If the wheel alignment is reset because of tire wear, always
reset the toe as close to zero degrees as the specification
allows. Refer to ”Rear Toe Adjustment” in this section.
Rotate the tires if:
S The front tire wear is different from the rear.
S The left and right front tire wear is unequal.
S The left and right rear tire wear is unequal.
Check wheel alignment if:
S The left and right front tire wear is unequal.
S The wear is uneven across the tread of either front
tire.
S The front tire treads are scuffed with ”feather”
edges on the side of the tread ribs or blocks.
Tread Wear Indicators
The original equipment tires have built–in tread wear indi-
cators to show when the tires need replacement. These in-
dicators appear as bands when the tire tread depth be-
comes shallow. Tire replacement is recommended when
the indicators appear in three or more grooves at six loca-
tions.
Radial Tire Waddle
Waddle is side–to–side movement at the front or rear of
the vehicle. It is caused by the steel belt not being straight
within the tire, or by excessive lateral runout of the tire or
wheel. It is most noticeable at low speeds, 8 to 48 km/h (5
to 30 mph), but may appear as ride roughness at 80 to 113
km/h (50 to 70 mph).
The vehicle must be road tested to determine which end
of the vehicle has the faulty tire. The rear end of the vehicle
will shake from side to side or ”waddle” if the waddle tire
is on the rear of the vehicle. From the driver’s seat, it feels
as though someone is pushing on the side of the vehicle.
If the faulty tire is on the front of the vehicle, the waddle is
more visual. The front sheet metal appears to be moving
back and forth, and the driver’s seat feels like the pivot
point in the vehicle.
Waddle can be diagnosed using the method of substi–tut-
ing known good tire and wheel assemblies on the problem
vehicle.
1. Road test the vehicle to determine if the waddle is
coming from the front or the rear of the vehicle.
2. Install good tires and wheels from a similar vehicle
in place of those on the offending end of the prob-
lem vehicle. If the source of the waddle is not ob-
vious, change the rear tires.
3. Road test the vehicle. If there is improvement,
install the original tires to find the offending tire. If
there is no improvement, install good tires in place
of all four offending tires.
Page 912 of 2643

WHEEL ALIGNMENT 2B – 5
DAEWOO V–121 BL4
VIBRATION DIAGNOSIS
Wheel imbalance causes most highway speed vibration
problems. A vibration can remain after dynamic balancing
because:
S A tire is out of round.
S A rim is out of round.
S A tire stiffness variation exists.
Measuring tire and wheel free runout will uncover only part
of the problem. All three causes, known as loaded radial
runout, must be checked using method of substituting
known good tire and wheel assemblies on the problem ve-
hicle.
Low–speed vibrations, which occur below 64 km/h (40
mph), are usually caused by runout. High–speed vibra-
tions, which occur above 64 km/h (40 mph), can be caused
by either imbalance or runout.
Preliminary Checks
Prior to performing any work, always road test the car and
perform a careful visual inspection for:
S Obvious tire and wheel runout.
S Obvious drive axle runout.
S Improper tire inflation.
S Incorrect trim height.
S Bent or damaged wheels.
S Debris build–up on the tire or the wheel.
S Irregular or excessive tire wear.
S Improper tire bead seating on the rim.
S Imperfections in the tires, including: tread deforma-
tions, separations, or bulges from impact damage.
Slight sidewall indentations are normal and will not
affect ride quality.
Tire Balancing
Balance is the easiest procedure to perform and should be
done first if the vibration occurs at high speeds. Do an off–
vehicle, two–plane dynamic balance first to correct any im-
balance in the tire and wheel assembly.
An on–vehicle finish balance will correct any brake drum,
rotor, or wheel cover imbalance. If balancing does not cor-
rect the high–speed vibration, or if the vibration occurs at
low speeds, runout is the probable cause.
Runout
Runout can be caused by the tire, the wheel, or the way
the wheel is attached to the vehicle. To investigate the pos-
sibility of wheel runout, refer to the following procedures
as well as the wheel runout diagnosis chart in this section:
1. If runout is suspected, measure the on–vehicle free
lateral and free radial runout of the tire and wheel
assembly. Refer to Section 2E, Tires and Wheels.
Both the free lateral and the free radial runout
should be less than 1.5 mm (0.06 inch). If either
measurement exceeds this number, proceed to
Step 2.
2. Mount the tire and the wheel on a dynamic balanc-
ing machine and remeasure the free lateral and the
free radial runout. Record the amount of the free
lateral and the free radial runout and the location of
the highest measurement. Refer to Section 2E,
Tires and Wheels. If the free radial or the free later-
al runout exceeds 1.3 mm (0.05 inch) at the tire
tread, proceed to Step 4.
3. Measure the wheel runout. Refer to Section 2E,
Tires and Wheels. If the wheel exceeds specifica-
tions, replace it.
4. Deflate the tire and match–mount the high radial
runout point of the tire to the low radial runout point
of the wheel. Reinflate the tire and mount it on the
dynamic balancing machine. Measure and record
the free radial and the free lateral runout and their
locations. In many cases, match mounting the tire
on the wheel will bring the tire and wheel assem-
bly’s free runout into an acceptable range of 1.3
mm (0.05 inch) or less.
5. If the free runout of the tire and wheel assembly is
1.3 mm (0.05 inch) or less when it was measured
off the vehicle, yet exceeds 1.3 mm (0.05 inch)
when measured on the vehicle, the attachment of
the tire and wheel assembly to the hub is the prob-
able cause of the vibration. Rotate the assembly’s
two wheel studs and recheck the runout. Refer
toSection 2E, Tires and Wheels. Several positions
may have to be tried to find the best location for the
studs.
6. If the tire and wheel assembly free runout cannot
be reduced to 1.3 mm (0.05 inch) or less, remove
the assembly.
1) Measure the wheel stud runout using a dial
indicator set with a magnetic base.
2) Zero the dial indicator set button on one stud.
3) Gently lift the set button off the stud. Rotate
the flange to position the next stud against the
dial indicator set.
4) Record the runout of all the studs. The dial in-
dicator should read zero when it is repositioned
on the first stud that was checked.
5) If the runout exceeds 0.76 mm (0.03 inch), the
hub or the hub and bearing assembly should
be replaced.
Page 915 of 2643

2B – 8IWHEEL ALIGNMENT
DAEWOO V–121 BL4
PRELIMINARY INSPECTION
ChecksAction
Check the tires for proper inflation pressures and normal
tread wear.Inflate the tires to the proper tire pressure. Replace the
tires as needed.
Check the wheel bearings for looseness.Tighten the axle nut to the proper specification. Replace
the strut wheel bearing as needed.
Check for loose ball joints and tie rod ends.Tighten the ball joints and the tie rods.
Check the runout of the wheels and the tires.Measure and correct the tire runout.
Check the vehicle trim heights.Correct the trim heights. Make the correction before ad-
justing the toe.
Check for loose rack and pinion mounting.Tighten the mounting brackets for the rack and pinion as-
sembly.
Check for improperly operating struts.Replace the strut assembly.
Check for loose control arms.Tighten the control arm attachment bolts. Replace the con-
trol arm bushings as needed.
FRONT TOE ADJUSTMENT
1. Disconnect the outer tie rods from the knuckle as-
semblies. Refer to Section 6C, Power Steering
Gear.
2. Turn the right and the left outer tie rods and the ad-
juster nuts to align the toe to 0.0 ± 0.10 degree.
3. Reconnect the outer tie rods to the knuckle assem-
blies. Refer to Section 6C, Power Steering Gear.
Notice : In this adjustment, the right and the left tie rods
must be equal in length, or the tires will wear unevenly.FRONT CAMBER AND CASTER
CHECK
The front camber and caster are not adjustable. Refer to
”Wheel Alignment Specifications” in this section. Jounce
the bumper three times before measuring the camber or
the caster in order to prevent an incorrect reading. If the
front camber or caster measurements deviate from the
specifications, locate and replace or repair any damaged,
loose, bent, dented, or worn suspension part. If the prob-
lem is body related, repair the body.
REAR CAMBER CHECK
The rear camber is not adjustable. Refer to ”Wheel Align-
ment Specifications” in this section. If the rear camber
deviates from the specification, locate the cause and cor-
rect it. If damaged, loose, bent, dented, or worn suspen-
sion parts are found, they should be repaired or replaced.
If the problem is body related, repair the body.
Page 963 of 2643

SECTION : 2E
TIRES AND WHEELS
TABLE OF CONTENTS
SPECIFICATIONS2E–1 . . . . . . . . . . . . . . . . . . . . . . . . . .
Tire Size and Pressure Specifications 2E–1. . . . . . . .
Inflation Pressure Conversion Specifications 2E–2. .
Fastener Tightening Specifications 2E–2. . . . . . . . . . .
DIAGNOSIS2E–2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wheel Runout 2E–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MAINTENANCE AND REPAIR2E–3 . . . . . . . . . . . . . . .
ON–VEHICLE SERVICE 2E–3. . . . . . . . . . . . . . . . . . . . .
Wheel 2E–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
On–Vehicle Balancing 2E–4. . . . . . . . . . . . . . . . . . . . . .
UNIT REPAIR 2E–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Alloy Wheel Porosity 2E–5. . . . . . . . . . . . . . . . . . . . . . .
Alloy Wheel Refinishing 2E–5. . . . . . . . . . . . . . . . . . . . .
Off–Vehicle Balancing 2E–7. . . . . . . . . . . . . . . . . . . . . . Correcting Non–Uniform Tires 2E–7. . . . . . . . . . . . . . .
Tire and Wheel Match–Mounting 2E–8. . . . . . . . . . . . .
Tire Mounting and Dismounting 2E–8. . . . . . . . . . . . . .
GENERAL DESCRIPTION AND SYSTEM
OPERATION 2E–9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tire and Wheel Balancing 2E–9. . . . . . . . . . . . . . . . . . .
Tire Chain Usage 2E–9. . . . . . . . . . . . . . . . . . . . . . . . . .
Replacement Tires 2E–10. . . . . . . . . . . . . . . . . . . . . . . .
All Season Tires 2E–10. . . . . . . . . . . . . . . . . . . . . . . . . .
Passenger Metric Sized Tires 2E–10. . . . . . . . . . . . . .
Tire Label 2E–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Spare Tire 2E–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wheels 2E–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inflation o Tires 2E–11. . . . . . . . . . . . . . . . . . . . . . . . . . .
SPECIFICATIONS
TIRE SIZE AND PRESSURE SPECIFICATIONS
Inflation Pressure at Full Load
TiresWheelFrontRear
kPapsikPapsi
175 / 70R145.5J x 14(Steel)2053020530
175 / 70R145.5J x 14(Alloy)2053020530
T125 / 70D154T x 154156041560
185 / 65R145.5J x 14(Steel)2053020530
185 / 65R145.5J x 14(Alloy)2053020530
T125 / 70D154T x 154156041560
195 / 55R156J x 15(Steel)2053020530
195 / 55R156J x 15(Alloy)2053020530
195 / 55R156J x 15
(Alloy, Sporty)2053020530
T125 / 70D154T x 154156041560
Page 964 of 2643

2E – 2ITIRES AND WHEELS
DAEWOO V–121 BL4
INFLATION PRESSURE CONVERSION SPECIFICATIONS
kPaPsikPaPsikPaPsi
140201852723534
145211902824035
155222002925036
160232053027540
165242153131045
170252203234550
FASTENER TIGHTENING SPECIFICATIONS
ApplicationNSmLb–FtLb–In
Wheel Bolt (Alloy Wheel)10074–
Wheel Bolt (Steel Wheel)10074–
DIAGNOSIS
WHEEL RUNOUT
Measure wheel runout with an accurate dial indicator.
Measurements may be taken with the wheels either on or
off the vehicle, using an accurate mounting surface such
as a wheel balancer. Measurements may be taken with or
without the tire mounted on the wheel.
Measure radial runout and lateral runout on both the in-
board and the outboard rim flanges. With the dial indicator
firmly seated next to the wheel and tire assembly, slowly
rotate the wheel one revolution and record the indicator
reading. If any measurement exceeds the following speci-
fications and there is a vibration that wheel balancing will
not correct, replace the wheel. Disregard any indicator
readings due to welds, paint runs, or scratches.
Steel Wheels
S Radial runout: 0.8 mm (0.03 inch)
S Lateral runout: 1.0 mm (0.04 inch)
Alloy Wheels
S Radial runout: 0.25 mm (0.01 inch)
S Lateral runout: 0.25 mm (0.01 inch)
Measure free radial runout on the center of the tire tread.
The tread can be taped to present a smooth surface. Mea-
sure free lateral runout on the outboard side of the tire
nearest to the tread.