In an SAE discussion group I recently came across a discussion about tyre pressures and fuel economy. Here is a reply to the question: “Has anyone done a comprehensive study on how exactly tyre pressure effects gas mileage?” A colleague in the forum replied as follows:
“Yes, I have.
for the past thirty years I have kept tire pressure set at 42 psi in my cars. There has been no significant change in the tire ‘footprint’, no effect on real world anti-lock braking, and an appreciable increase of 4-5 mpg, and increased tire life.
Back in the ’70’s, I taught an advanced diagnosis R/D course at a NJ college. Students were ready to graduate at the end of the course semester. The training facility had an in ground chassis dynamometer. Students were divided in small groups of three and were instructed to do anything they wanted to reduce road horsepower, ie.increase mpg, required to keep the vehicle rolling at a constant speed/load.
Students reduced vehicle weight, (by removing components such as seat, weighing them, then subtracting the weight via the dyno control panel), changed aerodynamics by figuring wind drag based upon frontal area and known factors, engine modification to include such things as five angle valve refacing, camshaft profile changes, etc., elimination of catalytic converters, and tire pressure. Proper research procedures were followed to ensure as accurate as possible results. Having taught this course several times with different students, vehicles, etc., there was only one vehicle change that effectively changed fuel economy, tire pressure.
Students increased tire pressure from the then specified 28-32 psi specification, a little at a time until a measureable change was found. Research was done regarding the development of the radial tire. Use of the radial tire in performance racing applications. Also research on the bias ply/radial tire, today known as emergency vehicle tires.
Vehicle mpg increased, (road hp required decreased), as the tire pressure was increased up to approximately 45 psi. Beyond that, there was no appreciable mpg increase.
Tire manufacturers informed the students that the sidewalls of a radial, being flexible, straighten out with increased tire pressure, leaving the ‘footprint’, unaffected. Also, that radial tires were originally produced and operated at 60 psi, (back in the early years, ’50’s). This was how students decided to experiment with tire pressure.
So, as a result, the tires of my cars are inflated to 42 psi and my truck tires to 55 psi. I have enjoyed the maximum mpg and tire life. Claims of poor tire life from factory tires have been negated.
[…] Hope you found this helpful. Just don’t plagiarize. Thanks”(Source: Fred Allen, retired automotive professor, 43 years , Rockport ME, USA)
What do you think about this? Fred’s experience is clear but are there any potential problems with increasing tyre pressures in this way? All sensible comments welcome!
The car: the driver’s truly personal assistant Bosch car-of-the-future will experience a new kind of interaction between humans and technology. The car dashboard and central console have been transformed into an electronic display. The information shown on this giant display changes depending on the vehicle’s current surroundings. If a pedestrian approaches from the right, a lighting sequence is triggered to alert the driver. Drivers’ preferences as well as appointments in their diary are also taken into account. For example, if an appointment is cancelled, the car of the future will automatically indicate the route to the next appointment in the diary. Drivers will be able to activate the autopilot to free up even more time and make their journey more relaxed.
But tomorrow’s connected cars will also be capable of much more. With a connection to the smart home, they will enable household functions such as heating or security systems to be operated at any time. For example, should a courier attempt to deliver a package with no one at home, all it will take is the tap of a finger on the vehicle’s display to allow the courier to deposit the package inside the house and confirm receipt. Interaction with technology really will be able to take such varied forms, and offer such safety and convenience. Connected infotainment will let drivers navigate not just through the traffic but through their whole day. They will be able to use it to access online services and smartphone apps – and they will be able to control it using gestures and speech, just as if they were talking with a passenger. This will turn the car into the driver’s truly personal assistant.
A touchscreen that feels like it has real buttons In advance of the trade show, Bosch has received a CES 2016 Innovation Award in the In-Vehicle Audio/Video category for a new touchscreen. This device can generate different surface textures, allowing elements to be felt on the display. This haptic feedback makes it easier to operate infotainment applications such as navigation, radio, and smartphone functions. Often drivers will not even need to look at the information on the screen to control it – instead, they can keep their eyes on the road. The screen generates the feel of rough, smooth, and patterned surfaces to indicate different buttons and functions; to make a selection, a button needs to be pressed more firmly. What makes this special is that the touchscreen looks no different from an ordinary display – and yet it gives users the impression that they are pressing real buttons.
No need to fear wrong-way drivers: a guardian angel in the cloud Connectivity makes driver information more up to date than ever before. This is particularly important when it comes to wrong-way drivers. In general, it takes several minutes for radio stations to issue warnings over the airwaves, but a third of wrong-way driving incidents finish after just 500 meters. Bosch is currently developing a new cloud-based wrong-way driver alert that will let drivers know of any danger just ten seconds after it arises. As a pure software module, it can be integrated at low cost into smartphone apps such as Bosch’s myDriveAssist or existing infotainment systems. In order to detect wrong-way driving, the cloud-based function compares actual, anonymized vehicle movement on freeways with the permitted direction of travel. If there is a discrepancy, wrong-way drivers are warned of their error in a matter of seconds. At the same time, nearby cars traveling in the opposite direction are alerted to the danger. Starting in 2016, the new function will be available as a cloud service.
The highway pilot will increase road safety from 2020 Highly automated driving will further increase the safety of road traffic. This development will come to freeways in 2020. According to forecasts made by Bosch accident researchers, increasing automation can significantly reduce accident numbers – by up to a third in Germany alone. At CES 2016, Bosch will be showcasing the systems and sensors necessary for automated journeys in another demo vehicle at the Sands Expo. Visitors will also learn how the highway pilot works, a highly automated system that assumes all the driver’s tasks and responsibilities on freeways. This technology is already being tested on public roads. Bosch is testing automated driving on freeways not only in Germany and the United States but now also in Japan.
In the future, cars will also be able to see around bends and be aware of possible danger spots, thanks to a stream of real-time information from the internet on the location of traffic jams, construction sites, and accidents. This data will serve as an electronic “connected horizon” and give cars an even better picture of what lies ahead – further increasing safety and efficiency.
It’s up to cars, not drivers, to find a parking space Every journey ends with parking. To make this job easier, Bosch is developing a new function called automated valet parking. This solution does more than relieve drivers of the task of finding a vacant space in a parking garage: it enables cars to park themselves. Drivers can simply leave the car at the entrance to the parking garage. Using a smartphone app, they then instruct their car to find a space for itself. When ready to leave, they call the car back to the drop-off point in the same way. Fully automated parking relies on smart infrastructure in parking garages plus the vehicle’s on-board sensor systems – and connectivity for both. Sensors in the pavement provide up-to-date information on where free parking spaces are located, so cars know where to go. Bosch is developing not only the fully automated parking function but also all the necessary components in-house
(Internal Combustion Engine, Plug-in Hybrid Electric Vehicle (like my GTE!) or a pure Electric only Vehicle)
I have been playing around with a few figures relating to the overall costs of running these three different vehicles and trying to compare them – it is a difficult task! Here is what I have done so far, comments and ideas are welcome:
The cost of charging an EV battery depends on the size of the battery, how depleted the battery is and how quickly you charge it. As a guide, charging a pure-electric car from flat to full will cost from as little as £1.00 to £4.00. This is for a typical pure-EV with a 24kWh battery which will offer around 100 miles range.
This means the average cost of ‘fuel’ will be approximately £0.03 per mile. Similar costs will apply to PHEVs and E-REVs, and because the batteries are smaller, it will cost less to charge them. See also the figures in table 2.
In some cases it may be possible to charge overnight and take advantage of cheaper electricity rates. Other options include charging from domestic solar panels. At this time it is calculated that the total cost of ownership of an electric car is similar to an ICE because of the additional purchase costs. However, this will change and if other advantages are included such as congestion charges (currently £11.50 per day in London for ICE but zero for EVs), the EV will be significantly cheaper in the longer term.
Table 1 Comparison of costs
Term, mileage, fuel cost
Cost of fuel (£/gallon or £kW/h)
£5.70 / £0.05
Electricity (£/kWh) average standard/cheap/solar used for calculation
Official combined cycle mpg
Electricity consumption (Wh/km)
‘Real world‘ mpg
175 Wh/km0.28 kWh/mile
100 mpg *1
Real world consumption
Total fuel costs
(annual miles * fuel cost / mpg)(annual miles * fuel cost * kWh/mile)
Vehicle cost information
Estimates based on current list prices
Plug-in car grant
A grant to reduce cost by 25% (up to £5,000)
Net purchase price
30% used – this will vary however
Service, maintenance and repair
Based on average of published figures.
Vehicle Excise Duty and Registration Fee
Important note: the figures used in this table are ‘best guesses’ but none-the-less give a reasonable comparison. The bottom line is that the three cars have broadly the same overall total cost even though the Pure-EV and the PHEV have much lower fuel costs. The key factor will be how the depreciation cost of the EVs pan out. However, over subsequent years the fuel savings associated with the EVs will become more significant.
Being able to programme EVs to charge during the night will allow drivers to take advantage of cheaper electricity prices, whilst using any surplus electricity. In addition, the development of smart metering systems which can automatically select charging times and tariffs can also help to manage demand on the grid. The National Grid manages the grid on a second by second basis to ensure that supply and demand are met and to indicate to the market if there is a shortfall or surplus of power.
*1 Very much depends on the length of journey – an average value was used
…we’ll almost, at least very cheap motoring is the plan!
On the 7th August 2015 I took delivery of the (almost) final part of the puzzle that when put together will result in big savings – I hope. I still need to get the proper charging point together with gadgets to monitor energy use etc., but I am nearly there. Here is my new Golf GTE (from Inchcape in Chelmsford) taking its first charge on my drive:
The Golf GTE 1.4 TSI produces 204PS (Pferdestärke, abbreviation of the German term for metric horsepower). It is a PHEV (plug-in hybrid electric vehicle) 5dr DSG boasting 0–62mph in 7.6 seconds. and up to 166.0 mpg. The electric range is 31 miles and when electric and petrol combine, the total range is 580 miles. The previous data are laboratory figures of course, I will report back on what happens in the real world in due course. However, its performance is very impressive so far. Because the car is a plug-in hybrid it attracted the £5000 government grant. More on overall prices later though because cheap mileage is all very well but initial and running costs still have to be considered.
The other part of my cunning plan involves solar panels (actually photo-voltaic or PV panels) and these will be used to charge the 8.8 kWh lithium-ion battery in 3.75 hours from a domestic mains outlet, or 2.25 hours from a domestic wallbox.
My PV array has saved me buying a lot of electricity and has further resulted in an income. So far this year I have received about £400, by selling the excess energy back to the grid (using what is known as a feed-in tariff). In addition, my electricity bill has reduced as shown in the following chart:
As you would expect, we pay much more for the electricity we use than the price we get when selling it (something like 14p per unit when buying and 3p per unit when selling). The way the feed-in tariff works is that the electricity generation company pays us for 50% of the amount generated by the PV panels. So the more we generate the more we get but of course the other advantage is gained because the more of the PV energy we use, the less electricity we purchase. This is where the new car comes in. The plan is that whenever we return home, we will make sure all the available charge in the car’s lithium-iron (Li-on) traction batteries has been used up. This will simply be done by switching the car to full e-mode when 35 miles from home. The car will now only be charged when enough solar energy is available (emergencies excepted of course). I am doing this manually at the moment but it will be automated in due course.
I have just completed a journey, by pure coincidence, to the UK VW headquarters where they have a charge point (well they should have shouldn’t they)! This was about a 170 mile round trip for me. I set off with a fully charged battery and managed to add 20 miles worth of charge while I was there. The car trip computer showed an overall average mpg of 68 – so just under 2.5 gallons. for the journey. My previous car (a modern Golf GTD 2.0ltr) would have done the same at an average of about 48 mpg (about 3.5 gallons). This journey was a good combination of country roads and motorway so probably indicates a good average. I did not try to save fuel or equally I didn’t accelerate/brake rapidly so the figures are probably quite a good start for real-world use. When used in hybrid mode only, the average was about 50 mpg .
I am expecting to win much more on the shorter journeys we do, which will use no petrol or very little. My journey to the office at the IMI for example, is about 42 miles each way. We have a free charging point! My hope therefore is to only use about half a gallon of fuel for the return trip (60 miles on full electric and 25 miles at 50 mpg).
Test cars fitted with Bosch technology can already drive themselves
Bosch is developing automated driving in California and Germany
Bosch sensors are the eyes and ears of modern vehicles
Bosch iBooster paves the way for automated driving
Bosch to present its technology portfolio at the Vehicle Intelligence Marketplace
Figure 1 At the CES in Las Vegas, Bosch will not only be presenting its extensive product portfolio for driver assistance functions and braking systems at the Vehicle Intelligence Marketplace. The company will also be exhibiting a true Hollywood legend: K.I.T.T. from the action series “Knight Rider”.
Hollywood did it first: in the 1980s, the dream factory created the action series “Knight Rider”, featuring a speaking and – more importantly – self-driving Pontiac Firebird Trans Am named K.I.T.T. Nearly 30 years later, automated driving is no longer just another TV fantasy. “Bosch is making science fiction reality, one step at a time,” says Dr. Dirk Hoheisel, who sits on the Bosch board of management. Cars equipped with Bosch technology can already drive themselves in certain situations, such as in traffic jams or when parking. Bosch will be presenting its solutions at the Vehicle Intelligence Marketplace during the CES in Las Vegas (January 6-9, 2015).
Figure 2 On the Las Vegas Strip, a Bosch vehicle demonstrates how the traffic jam assist function works. In congested traffic up to a speed of 60 kph, the function brakes, accelerates, and keeps the vehicle in its lane – without any intervention by the driver.
As one of the world’s largest providers of mobility solutions, Bosch has been working on automated driving since 2011 at two locations – Palo Alto, California, and Abstatt, Germany. The teams at the two locations can draw on a worldwide network of more than 5,000 Bosch engineers in the field of driver assistance systems. The motivation behind the development at Bosch is safety. Worldwide, an estimated 1.3 million traffic fatalities occur each year, and the numbers are rising. In 90 percent of cases, human error is the cause.
Figure 3 Thanks to the traffic jam assist, drivers can now reach their destination more safely and with less stress. Driving along the Las Vegas Strip in a demonstration vehicle, drivers can see for themselves what the function is capable of.
From predictive emergency braking to traffic jam assistance
Assisting drivers in critical traffic situations can save lives. Studies suggest that, in Germany alone, up to 72 percent of all rear-end collisions resulting in casualties could be avoided if all cars were fitted with the Bosch predictive emergency braking system. Drivers can also reach their destinations safely and with minimum stress using the Bosch traffic jam assistant. At speeds of up to 60 kilometers per hour, the assistant brakes automatically in heavy traffic, accelerates, and keeps the car in its lane.
Figure 4 As one of the world’s largest providers of mobility solutions, Bosch has been working on automated driving since 2011. Cars equipped with Bosch technology can already drive themselves in certain situations, such as traffic jams or when parking.
“With driver assistance systems, Bosch expects to generate sales of one billion euros in 2016,” Hoheisel says. Assistance systems are the cornerstone for automated driving, which will become established in a gradual process. Bosch already has its sights on highly automated driving, in which drivers no longer have to constantly monitor the vehicle. “With Bosch highway pilots, cars will be driving automatically on freeways by 2020, from entrance ramp to exit ramp,” Hoheisel predicts. In the decade that follows, vehicles driving fully automated will be available, capable of handling any situations that arise.
Figure 5 Bosch is developing and testing automated driving at two locations – in Palo Alto, California, and Abstatt, Germany. The teams at the two locations can draw on a worldwide network of more than 5,000 Bosch engineers working in the field of driver assistance systems.
Bosch sensors are the car’s eyes and ears
Automated driving affects every aspect of the car – powertrain, brakes, steering – and requires comprehensive systems expertise. It is based on sensors featuring radar, video, and ultrasound technology, sensors Bosch has been manufacturing by the millions for many years. “Sensors are the eyes and ears that let vehicles perceive their environment,” Hoheisel says. Powerful software and computers process the collected information and ensure that the automated vehicle can move through traffic in a way that is both safe and fuel efficient.
As vehicles gradually take over more and more driving tasks, safety-critical systems such as brakes and steering must satisfy special requirements. Should one of these components fail, a fall-back is needed to ensure maximum availability. Bosch already has such a fall-back for brakes: the iBooster, an electromechanical brake booster. Both iBooster and the ESP braking control system are designed to brake the car – independently of each other – without the driver having to intervene.
Figure 6 Bosch has been testing automated driving with special demonstration vehicles on public roads in the U.S. and Germany since the beginning of 2013. Several thousand test kilometers have already been driven.
iBooster: essential for automated driving
In this way, the Bosch iBooster meets an essential requirement for automated driving. The brake booster can build up brake pressure independently, three times faster than an ESP system. If the predictive brake system recognizes a dangerous situation, the vehicle stops much faster. At the same time, the iBooster can also provide the gentle braking required by the ACC adaptive cruise control, all the way down to a complete stop. Moreover, it is practically silent.
Figure 7 The motivation behind the development of automated driving at Bosch is safety. Worldwide, an estimated 1.3 million traffic fatalities occur each year. Drivers can reach their destinations safely and with minimum stress using systems such as the Bosch traffic jam assistant. At speeds up to 60 kilometres per hour, the assistant brakes automatically in heavy traffic, accelerates, and keeps the car in its lane.
The iBooster is also a key component for hybrid and electric cars. One reason is that it does not require a vacuum, which otherwise has to be generated in a complex process by the combustion engine or a vacuum pump. Second, because in conjunction with ESP hev (designed especially for hybrid and electric vehicles), the brake booster can recover nearly all braking energy and convert it into electricity, which extends the e-vehicle’s range. Thanks to the iBooster, nearly all typical traffic delays can be used to recover maximum braking energy for the hybrid or electric vehicle’s electric motor. If the car has to brake sharply, or if the generator is unable to provide the necessary brake torque, the brake booster generates any additional brake pressure required in the conventional way, using the brake master cylinder.
Figure 8 Driver assistance systems are the cornerstone of automated driving, which will become established in a gradual process. Bosch has already set its sights on highly automated driving, in which drivers no longer have to constantly monitor their vehicle. With the Bosch highway pilot, cars will be driving themselves on freeways by 2020, from entrance ramp to exit ramp. In the decade that follows, vehicles will become fully automated, capable of handling any situations that arise.
Bosch technology at the Vehicle Intelligence Marketplace
At 2015 International CES in Las Vegas, Bosch will not only be presenting its extensive product portfolio for driver assistance functions and braking systems at the Vehicle Intelligence Marketplace. The company will also be exhibiting a true Hollywood legend: K.I.T.T. replica from the action series “Knight Rider”.
Toyota City, Japan – Toyota Motor Corporation (TMC) announced that it will conduct public road tests of a Toyota-developed driving support system using ITS (1) technology to transmit information from traffic light signals information to vehicles, starting in May, 2013 in Toyota City, Japan. The system is part of a number of Driving Safety Support Systems (DSSS) being promoted by the Japanese National Police Agency and sponsored by the Universal Traffic Management Society of Japan (UTMS Japan) (2).
One road in Toyota City will be used for the tests which will be equipped with a system to transmit traffic light signal information to vehicles through its on-board testing equipment using the 700 MHz bandwidth (3). The system receives the information, providing alerts when necessary to vehicle occupants via the audio system and on-screen on the navigation system. Added to TMC’s separate system to help drivers notice red lights, it is hoped that by early encouragement to decelerate when approaching red lights, the system can help in reducing CO2 emissions.
Provision of traffic light signal information was made possible with the cooperation of the National Police Agency and the Aichi Prefectural Police.
Through these tests, TMC will analyse driver behaviour under various driving conditions to understand the extent to which cooperative vehicle-infrastructure systems can contribute to reducing traffic accidents and CO2 emissions, and incorporate the data into future ITS development.
Based on its Integrated Safety Management Concept, TMC is making proactive efforts to develop its driving vehicle infrastructure cooperative (4) safety support systems utilising ITS technologies that make it possible to connect people, vehicles, and traffic environments. TMC has been using the 700 MHz band (allocated by the Japanese government for ITS) starting with road tests in March last year on a support system aimed at preventing collisions caused by driver error during right-hand turns at intersections.
(1) Intelligent Transport Systems: systems that seek to prevent traffic accidents by alerting the driver to dangerous situations through provision of visual and aural information on nearby traffic conditions, reduce environmental impact and emissions, and create a more comfortable driving environment.
(2) Carries out surveys, research, and development on Universal Traffic Management Systems (UTMS). UTMS Japan aims to contribute to social welfare by promoting more intelligent road transportation; ensuring safe, smooth road transportation; and ensuring harmony with the environment.
(3) 700 MHz band ITS standard (ARIB STD-T109). Because this communication method features electromagnetic waves with excellent propagation characteristics, it is expected to be effective for supporting the prevention of vehicle-to-vehicle collisions at intersections and collisions with vehicles coming from the opposite direction when making right-hand turns.
(4) A type of ITS that receives information – including traffic regulation information (such as information on the cycle of traffic lights) and information about things that cannot be directly seen by the driver – via wireless communication from communications infrastructure installed in roads and other vehicles. By notifying the driver of this information, this system supports safe driving and helps prevent accidents.
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