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Renthal front and rear sprockets are used by many of the World's top Road Racers, but why are riders using Renthal products so successful?

Renthal road racing products are designed and engineered specifically for road racing and normal road use too and are then exhaustively tested by the world's best riders as part of Renthal's ongoing development process. So they know they have the world's best sprockets fitted to their bike, sprockets they can rely upon 100%.

And, any rider using Renthal products purchased from HPS, has exactly the same parts on his or her bike as those used by the best riders in the world!
RENTHAL - WE BUILD CHAMPIONSHIPS...
 
2001 WORLD SUPERBIKE  
Team Riders
Castrol Honda Colin Edwards, Tadayuki Okada
Kawasaki Racing Team Eckl Akira Yanagawa, Gregorio Lavilla, Hitoyasu Izutsu
GSE Racing Neil Hodgson and James Toseland






Castrol Honda
Colin Edwards, Tadayuki Okada		 Kawasaki Racing Team Eckl
Akira Yanagawa, Gregorio Lavilla, Hitoyasu Izutsu
___________________________________________________________________________________________

2001 WORLD 600 SUPERSPORT
Team Riders
Team Dienza Ducati Vitto Guareschi and Dean Thomas
Castrol Honda Chris Vermeulen
Kawasaki Racing Iain MacPherson and Andrew Pitt
Team Ten Kate Pere Riba, Fabien Foret
___________________________________________________________________________________________
     
2001 UK SUPERBIKE  
Team Riders
GSXR Factory squad John Crawford
Red Bull Ducati John Reynolds and Sean Emmett
Virgin Yamaha James Haydon and Jamie Robinson
Monster Mod Ducati Steve Hislop
Kawasaki Steve Plater
Dienza Ducati Paul Brown
___________________________________________________________________________________________
      
Aluminium alloy rear sprockets Racing and Road use

Precision CNC manufactured to extremely tight tolerances from a high strength, specially enhanced 7075 T6 aluminium alloy, Renthal sprockets have unequalled accuracy of fit, tooth profile and concentricity for longevity and maximum power transfer.

Maximum reduction of unsprung revolving weight at the rear wheel, through a combination of the choice of material and design ensures maximum power transfer. Renthal rear wheel sprockets are 33% of the weight of steel yet incredibly durable.


Available in silver etched finish, titanium/bronze coloured hard anodised and from HPS in Gold too.

 
 
Case hardened front Sprockets for Racing and Road use
Precision CNC manufactured to extremely tight tolerances from a case hardened and core refined 655M13Nickel-Chrome-Molybdenum alloy steel used to give the ultimate combination of strength and hardness.
Advanced design ensures minimum weight while retaining maximum strength.

Renhtal Chain and Sprocket Fitting Notes
When fitting new sprockets it is very important that a new chain is fitted at the same time, and vice versa. Using an old chain with new sprockets, or a new chain with old sprockets will cause rapid wear.

During use a chain will stretch (i.e. the pins will wear causing extension of the chain). To measure how much a chain has stretched, put the motorcycle in gear and rotate the rear wheel to tension the top strand of the chain. Measure accurately (ideally with a vernier) 16 links, counting both roller and pin links. If the length of the measured 16 links is greater than the maximum acceptable length given in the table below then the chain should no longer be used. These figures assume a 2% maximum allowable extension for non 'O'-ring chain and a 1% maximum extension for 'O'-ring chain.


Using a chain which has been stretched more than the above maximum allowance causes the chain to ride up the teeth of the sprocket. This causes damage to the tips of the chainwheels teeth, as the force transmitted by the chain is transmitted entirely through the top of the tooth, rather than the whole tooth. This results in severe wearing of the chainwheel.

Misalignment of front and rear sprocket is a major cause of rapid wear. Chains and sprockets should be checked for worn spots which could indicate misalignment. Misalignment is usually due to not adjusting the chain tensioners an equal amount on both sides, worn wheel bearings or worn swinging arm bushings. To check the alignment put the bike on a stand, spin the rear wheel and watch how the chain travels along the sprockets. The chain should run on the centre of the teeth, it should not run to one side or snake from one side to the other.


CORRECT


INCORRECT



INCORRECT

These diagrams show two examples of misalignment which must be avoided. A long rule should be used to avoid these whist setting up. The front sprocket must be aligned within 1 mm (0.04") of the straight edge.


Lack of lubrication is a common cause of chain and sprocket wear. Check your chain is well lubricated. Neglecting a chain will cause it to rust.


Your chain snapping can cause expensive damage to your bike. If your chain is damaged, worn or overstretched, replace it now.


Renthal chain and sprockets are a perfectly matched, hard wearing, high quality replacement for you existing final drive.


Checklist - when fitting new chain and sprockets ensure that:


- You do not mix old and new chain and sprockets.
- The sprockets are correctly aligned.
- The chain and sprockets are well lubricated.


Renthal Chain - good for your teeth.

More Technical Information Regarding, Sprockets, Gearing and Chain
Reproduced by kind permission of Renthal
 
Introduction to TORQUE, WORK and POWER

Torque is the twisting force about a point, sometimes called a 'moment'. The torque is defined as the force multiplied by the distance from the pivot perpendicular to the force.

For example: One foot pound of torque is the twisting force necessary to support a one pound weight on a weightless horizontal bar, one foot from the pivot. You might directly measure torque when tightening a nut to a specified torque using a torque wrench. Here, a twisting force is applied to the nut, until the resistance to rotation of the nut is equal to the torque required.


Work is the the transfer of energy. The work done is equal to the force applied multiplied by the distance travelled in the direction of that force.
TravelledPower is the rate of doing work, the amount of work done in a unit of time. The power produced is the work done divided by the time taken.

For example: If a weight is fixed solidly to the floor and you try to lift it, you are applying force. However the weight cannot move, so no work is done on the weight. Although force is exerted by your arms, no energy is transferred to the weight. If you lift a one pound weight one foot, then by definition one foot pound of work has been done. If you take one minute to do this then you will be producing power at one foot pound per minute.


One horsepower is 33,000 foot pounds per minute. To find the horsepower of an engine, the torque produced by the engine is measured and the horsepower calculated. This is done using a dynamometer which is essentially a brake with a measuring device - hence the term brake horse power (bhp) which is often used. A torque curve is produced by plotting the torque measured against the engine speed.
With torque in foot pounds:
Using this equation a power curve can be produced from the torque curve.
 
How does this apply to a motorcycle?

For the rider, torque is the all-important factor. A bike will accelerate at a rate that matches its torque curve (ignoring rolling / air resistance). The torque peak is the point at which the bike has maximum acceleration, either side of this peak it is less. For a given torque at the rear wheel, the acceleration of the bike is the same, irrespective of the engine speed. Horsepower increases with the engine speed until well after the torque peak, and only peaks when the decreasing torque compensates for the increasing rpm. (look at the equation.) The acceleration at the torque peak is greater than that at the power peak.
So why do we talk about horsepower so much? Consider a large waterwheel. While it's obvious that the water wheel generate a large torque, its rotational speed is very slow and hence its power (the ability to do work over time) is low. A waterwheel is therefore not generally very powerful. A powerful engine with lots of horsepower is one which produces high torque at high rpm.

Theoretically, producing torque at high rpm is better than producing torque low rpm, as at high rpm you can use gearing. A powerful engine is useful because it can then be geared down - you don't want the rear wheel of your bike doing 8000rpm anyway! Gearing down reduces the speed at the rear wheel with a corresponding increase in torque. This does not affect the power of the engine apart from frictional losses. Incidentally a properly lubricated chain drive is 98.5% efficient, significantly better than a geared drive. For road racing, this theory closely matches reality, but for offroad the above is not the only consideration. (still awake?!...)

 
Front and rear sprocket size gearing calculation chart
But what does that mean about gearing...
  æ10 11 12 13 14 15 16 17 18 19 20
65
6.5
5.91
5.42
5
4.64
4.33
4.06
3.82
3.61
3.42
3.25
64
6.4
5.82
5.33
4.92
4.57
4.27
4
3.76
3.56
3.37
3.2
63
6.3
5.73
5.25
4.85
4.5
4.2
3.94
3.71
3.5
3.32
3.15
62
6.2
5.64
5.17
4.77
4.43
4.13
3.88
3.65
3.44
3.26
3.1
61
6.1
5.55
5.08
4.69
4.36
4.07
3.81
3.59
3.39
3.21
3.05
60
6
5.45
5
4.62
4.29
4
3.75
3.53
3.33
3.16
3
59
5.9
5.36
4.92
4.54
4.21
3.93
3.69
3.47
3.28
3.11
2.95
58
5.8
5.27
4.83
4.46
4.14
3.87
3.63
3.41
3.22
3.05
2.9
57
5.7
5.18
4.75
4.38
4.07
3.8
3.56
3.35
3.17
3
2.85
56
5.6
5.09
4.67
4.31
4
3.73
3.5
3.29
3.11
2.95
2.8
55
5.5
5
4.58
4.23
3.93
3.67
3.44
3.24
3.06
2.89
2.75
54
5.4
4.91
4.5
4.15
3.86
3.6
3.38
3.18
3
2.84
2.7
53
5.3
4.82
4.42
4.08
3.79
3.53
3.31
3.12
2.94
2.79
2.65
52
5.2
4.73
4.33
4
3.71
3.47
3.25
3.06
2.89
2.74
2.6
51
5.1
4.64
4.25
3.92
3.64
3.4
3.19
3
2.83
2.68
2.55
50
5
4.55
4.17
3.85
3.57
3.33
3.13
2.94
2.78
2.63
2.5
49
4.9
4.45
4.08
3.77
3.5
3.27
3.06
2.88
2.72
2.58
2.45
48
4.8
4.36
4
3.69
3.43
3.2
3
2.82
2.67
2.53
2.4
47
4.7
4.27
3.92
3.62
3.36
3.13
2.94
2.76
2.61
2.47
2.35
46
4.6
4.18
3.83
3.54
3.29
3.07
2.88
2.71
2.56
2.42
2.3
45
4.5
4.09
3.75
3.46
3.21
3
2.81
2.65
2.5
2.37
2.25
44
4.4
4
3.67
3.38
3.14
2.93
2.75
2.59
2.44
2.32
2.2
43
4.3
3.91
3.58
3.31
3.07
2.87
2.69
2.53
2.39
2.26
2.15
42
4.2
3.82
3.5
3.23
3
2.8
2.63
2.47
2.33
2.21
2.1
41
4.1
3.73
3.42
3.15
2.93
2.73
2.56
2.41
2.28
2.16
2.05
40
4
3.64
3.33
3.08
2.86
2.67
2.5
2.35
2.22
2.11
2
39
3.9
3.55
3.25
3
2.79
2.6
2.44
2.29
2.17
2.05
1.95
38
3.8
3.45
3.17
2.92
2.71
2.53
2.38
2.24
2.11
2
1.9
37
3.7
3.36
3.08
2.85
2.64
2.47
2.31
2.18
2.06
1.95
1.85
36
3.6
3.27
3
2.77
2.57
2.4
2.25
2.12
2
1.89
1.8
35
3.5
3.18
2.92
2.69
2.5
2.33
2.19
2.06
1.94
1.84
1.75
34
3.4
3.09
2.83
2.62
2.43
2.27
2.13
2
1.89
1.79
1.7
33
3.3
3
2.75
2.54
2.36
2.2
2.06
1.94
1.83
1.74
1.65
32
3.2
2.91
2.67
2.46
2.29
2.13
2
1.88
1.78
1.68
1.6
31
3.1
2.82
2.58
2.38
2.21
2.07
1.94
1.82
1.72
1.63
1.55
30
3
2.73
2.5
2.31
2.14
2
1.88
1.76
1.67
1.58
1.5
29
2.9
2.64
2.42
2.23
2.07
1.93
1.81
1.71
1.61
1.53
1.45
28
2.8
2.55
2.33
2.15
2
1.87
1.75
1.65
1.56
1.47
1.4
27
2.7
2.45
2.25
2.08
1.93
1.8
1.69
1.59
1.5
1.42
1.35
26
2.6
2.36
2.17
2
1.86
1.73
1.63
1.53
1.44
1.37
1.3
25
2.5
2.27
2.08
1.92
1.79
1.67
1.56
1.47
1.39
1.32
1.25
24
2.4
2.18
2
1.85
1.71
1.6
1.5
1.41
1.33
1.26
1.2
23
2.3
2.09
1.92
1.77
1.64
1.53
1.44
1.35
1.28
1.21
1.15
22
2.2
2
1.83
1.69
1.57
1.47
1.38
1.29
1.22
1.16
1.1
21
2.1
1.91
1.75
1.62
1.5
1.4
1.31
1.24
1.17
1.11
1.05
20
2
1.82
1.67
1.54
1.43
1.33
1.25
1.18
1.11
1.05
1

The stock gearing of your bike is likely to have been determined by choosing a compromise ratio based on what worked best for test riders in "average" conditions.

As soon as the bike is taken out of average conditions - by engine tune, terrain, track design or rider style the stock gearing might no longer be the optimum solution - a different setup might get you round the track faster.

Maximum speed occurs when the driving force is exactly counterbalanced by the air and rolling resistances. At this point the acceleration has fallen to zero.

Setting up the gearing of any vehicle is a trade-off between acceleration and top speed.

Gearing a bike up to produce higher top speed with less acceleration is done using a larger countershaft (gearbox) sprocket or a smaller rear sprocket.

Gearing a bike down giving it more acceleration with lower top speed is done using a smaller countershaft (gearbox) sprocket or a larger rear sprocket.

The ratio chart shows the gearing ratios for different numbers of teeth on the gearbox and rear sprockets.

The numbers given are the number of revolutions of the gearbox sprocket required to cause one complete revolution of the back wheel.

These figures are calculated by dividing the number of teeth on the rear sprocket by the number of teeth on the gearbox sprocket.

From the table it is clear that changing one tooth on the gearbox sprocket has a significantly larger effect on the gearing than changing one tooth on the rear sprocket.

To make a small change in gearing it is therefore necessary to change the rear sprocket size by one tooth, as changing the gearbox sprocket makes a far larger difference in gearing.



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