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Serpentine Belt VS Timing Belt – Difference in alternator & drive belt

Confused with difference in serpentine belt and timing belt?

The same in both

Both are same If you observe material because of these belts are made of rubberized material with high tensile thread. Normally using Kevler or Teflon.

The difference in both

This image is best easiest examples to understand the difference. Front side is Serpentine Belt where you can see length side lines or design to fit in pulley. The other one is width side tooth that fixes in each pulley on drive.

Comparison between Timing & Serpentine Belt

Serpentine Belt

Timing Belt

1
Cost
Reasonable
High
2
Range
Limited
Vast
3
Application
Limited
Vast
4
Sizes
Few
Too much
5
Life
Average
Average
6
Manufacturers
Few Brands
Countless
7
Competition
Less
High
8
Sub-Products
Not available
PU, D-Type, & more

1. Cost

It comes in experience that (for sake or argument) Two same sized or same weighted or same thread manufactured timing & serpentine belts are different in costing. You timing belt cost is high than serpentine or alternator belt.

Why?

Different reasons are behind this Why (my personal experience)

  1. Old Fashioned: There is no advancement in serpentine from years and timing are being shifted to new timing pulley design and used for light to hard requirements
  2. Demand: Why does gates need to design gt3 when it already has gt2? Moving to new product variation from market perspective is necessity to stay in market. Machinery makers trust on timing belts.
  3. Age: Both lives are different. (details below)

2. Range

You can not even imagine the Types of Timing Belts and sizes available from manufacturers to industries. Each machine can use different and even a single machine uses different types and designs. Serpentine belt range is limited compared to timing.

Click the image to Enlarge

Belting Manufacturers are making advancements in cogged belts as you may see Polyurethane Timing Belt, but from my knowledge and experience i haven’t seen any Polyurethane Serpentine Belt.

Click the image to Enlarge

Traders & Distributors also focuses on timing stock because of the sales generation and better profit margin.

3. Application

Timing is used to transmit power and maintain rpm on the other hand serpentine belt has same required but at low level. Let me clear that, Serpentine belt is used on less rpm & power.

If you google, you shall find hundred of timing pulley manufacturers but very few for serpentine. It is only because timing are used widely at every industry including automotive, textile, food, confectionery, baking, cement, marble. floor, flour, rice, sugar, printing, packaging, and many others. Where as Serpentine are used on few.

4. Sizes

You shall find more and more different sizes in timing belts, sizes in terms of lengths only, AT10 has variation of lengths from 10mm on AT5 has 5mm length difference. Serpentine belt sizes are small in range.

5. Life & Durability

Serpentine belts works for small life. In car, you need to replace timing belt after 60K miles and serpentine after 120K only because Serpentine doesn’t bear load & timing works under pressure and high load. If both work on same rpm and power. Timing will work more and better. (Pulley difference is compulsory)

6. Manufactures

USA, UK, Germany, China, Thailand, India and many other countries are manufacturing timing belts on daily basis and new manufacturers are born daily. If you go to largest B2B store Alibaba.com. You shall be amazed to find great difference in number of both products manufacturers.

7. Competition

Of course, both are competitive products in industrial markets but timing are more competitive.

Click the image to Enlarge
Click the image to Enlarge

8. Sub-Production

Check this basis types of Serpentine Belt

Serpentine Belt Specification & Design Chart

Type
Pitch
Height
PH
1.6
3
PJ
2.34
4
PK
3.56
6
PL
4.7
10
PM
9.4
17

Timing Belt Specification Chart

Type
Pitch
Tooth Height
Belt Thickness
MXL
2.03
0.51
1.14
XXL
3.18
0.76
1.52
XL
5.08
1.27
2.30
L
9.53
1.91
3.60
H
12.70
2.29
4.30
XH
22.23
6.35
11.20
XXH
31.75
9.35
15.70
T2.5
2.50
0.70
1.30
T5
5.00
1.20
2.20
T10
10.00
2.50
4.50
T20
20.00
5.00
8.00
AT5
5.00
1.20
2.70
AT10
10.00
2.50
5.00
AT20
20.00
5.00
8.00
3M
3.00
2.40
1.17
5M
5.00
3.80
2.06
8M
8.00
6.00
3.40
14M
12.00
10.00
6.00
S2M
2.00
1.36
0.76
S3M
3.00
1.93
1.14
S4.5M
4.50
2.70
1.71
S5M
5.00
3.41
0.19
S8M
8.00
5.30
3.05
S14M
14.00
10.20
5.30
ZA
9.53
4.10
1.91
ZAS
9.53
4.62
2.32
ZB
9.53
4.50
2.29
ZBS
9.53
5.08
2.76
MY
8.00
5.21
3.06
MR
9.53
5.55
3.40
S8M
8.00
5.30
2.95
Y(MY)
9.53
1.91
5.21
R(MR)
8.00
3.11
5.69
YU
9.53
3.54
5.20
ZBS
9.53
2.80
5.10
FS8M
8.00
3.05
5.30
RU
9.53
3.56
5.70
RPP
9.53
2.25
4.50
ZAS
9.53
2.32
4.63
ZR
9.53
3.20
5.40
RHD
9.53
3.50
5.70
ZB
9.53
2.29
4.50
SL
9.53
3.40
5.50
RHX
9.53
2.62
4.80

Timing belts are huge in terms of sub productions, length, tooth design, tooth height variations and Serpentine belting range is limited

9. Design

The main difference in both. Timing Belt description is totally difference from serpentine belt. It is rubberized material tooth belt. Serpentine belt is multi-vee belt that drives both single and more than one pulley at the same time.

Polyurethane belts contains Stainless steel wiring instead of Kevler or Teflon thread.

From your Car Application

Most of the industrial machines i have seen are made with design that do not hurt other parts; still a few does but in automobile you can face upto 2000$ engine rebuilt cost if you neglect symptoms of bad belt  and do not visit mechanic to get it changed on advised replacement intervals.

Also check  Car Belt Specification chart to check your belt and save cost by changing your drive belt at home.

From Machinery Application

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