JR Auto Repair Service

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ROAD FORCE BALANCINGYou know tires have changed over the years. So have cars. And one of the more common problems that w...


You know tires have changed over the years. So have cars. And one of the more common problems that we find with automobiles in general has to do with tires. You see, tires change from being a tall tire, that’s the way they used to be. The distance from the rim up to the curve of the tread used to be quite a distance and it was relatively flexible.

Today, tires are much lower profile. The distance from the rim to the top of the tread is less and the sidewall is much stiffer. This means that minor problems can be amplified and transmitted into the car and you feel things a lot more than you used to.

But everybody says alright, we’ll balance the tires. That’s part of the equation but balancing isn’t always the answer. So you have to go a step further. What we have here is a Road Force balancer. This takes it to a new level.

This roller back here comes out against the tread of the spinning tire. It applies 1,200 pounds of pressure to simulate the weight of the vehicle on the tire as it rolls down the road. Now a computer in the machine, and sensors, sense variations in the tread. Stiffness, or the tire isn’t completely round, or anything that would prevent the tire from rolling smoothly when its weighted by the car.

Then it translates that into a road force reading. We have a warning that it is excessive. Next thing we do is take some measurements.

What we did is we took measurements of the rim. Of course the machine had already measured the tire. Now we can do what is called match mounting. We’re going to take the high spot of the tire and match it against the low spot of the wheel. It’s really more complicated than that, but to make it understandable… that’s what we’re doing. And it’s telling us here that we have 15 pounds of road force in the tire and if we swapped the tire around, moved it around on the rim, such as it’s showing us over here, that we can reduce this to 8 pounds total.

That brings us in spec and that means now we’re going to have a smooth riding tire.

Paying a Premium for High Octane Gasoline?Unless it’s recommended by your owner’s manual, don’t spend the money on high ...

Paying a Premium for High Octane Gasoline?

Unless it’s recommended by your owner’s manual, don’t spend the money on high octane gas. In most cases, there’s no benefit. Higher octane helps only if you have problems with your engine “knocking.”

Read Your Owner’s Manual

Unless your engine is knocking, buying higher octane gasoline is a waste of money. Premium gas costs 15 to 20 cents per gallon more than regular. That can add up to $100 or more a year in extra costs. Studies indicate that altogether, drivers may be spending hundreds of millions of dollars each year for higher octane gas than they need.

It may seem like buying higher octane “premium” gas is like giving your car a treat, or boosting its performance. But take note: the recommended gasoline for most cars is regular octane. In fact, in most cases, using a higher octane gasoline than your owner's manual recommends offers absolutely no benefit. It won't make your car perform better, go faster, get better mileage, or run cleaner. Your best bet: listen to your owner's manual.

The only time you might need to switch to a higher octane level is if your car engine knocks when you use the recommended fuel. This happens to a small percentage of cars.

About Octane Ratings
What are octane ratings?
Octane ratings measure a gasoline's ability to resist engine knock — a rattling or pinging sound that results from premature ignition of the compressed fuel-air mixture in one or more cylinders. Most gas stations offer three octane grades: regular (usually 87 octane), mid-grade (usually 89 octane), and premium (usually 92 or 93). The ratings are posted on bright yellow stickers on each gas pump.

What's the right octane level for your car?
Check your owner's manual. Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars and certain luxury cars, need mid-grade or premium gasoline to prevent knocking.

How can you tell if you're using the right octane level? Listen to your car's engine. If it doesn't knock when you use the recommended octane, you're using the right grade of gasoline.

Will higher octane gasoline clean your engine better?
No, as a rule, high octane gasoline doesn’t outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your car's engine. In fact, the U.S. Environmental Protection Agency requires that all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car.

Should you ever switch to a higher octane gasoline?
A few car engines may knock or ping even if you use the recommended octane. If this happens, try switching to the next highest octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking.

Will knocking harm my engine?
Occasional light knocking or pinging won't harm your engine, and doesn't mean you need a higher octane. But a heavy or persistent knock can lead to engine damage.

Is all "premium" or "regular" gasoline the same?
The octane rating of gas labeled "premium" or "regular" isn’t the same across the country. One state may require a minimum octane rating of 92 for all premium gasoline, while another may allow 90 octane to be called premium. To make sure you know what you're buying, check the octane rating on the yellow sticker on the gas pump.

Exhaust System on a Tundra

Exhaust System on a Tundra

headlights restoration...

headlights restoration...

Nissan QUEST 2008...Timing chain job...complete overhaul

Nissan QUEST 2008...
Timing chain job...
complete overhaul

Untitled Album

Untitled Album



Our new scan tool has been arrived. "MODIS Ultra". Getting ready for the new technology

Our new scan tool has been arrived. "MODIS Ultra". Getting ready for the new technology

A complete overhaul brake lines system on a 1998 caravan .....yeah... mission accomplished !!!!

A complete overhaul brake lines system on a 1998 caravan .....
yeah... mission accomplished !!!!



CVT explained

What is a continuously variable transmission CVT?

A continuously variable transmission, or CVT, is a type of automatic transmission that provides more useable power, better fuel economy and a smoother driving experience than a traditional automatic transmission.

How the CVT works

Traditional automatic transmissions use a set of gears that provides a given number of ratios (or speeds). The transmission shifts gears to provide the most appropriate ratio for a given situation: Lowest gears for starting out, middle gears for acceleration and passing, and higher gears for fuel-efficient cruising.

The CVT replaces the gears with two variable-diameter pulleys, each shaped like a pair of opposing cones, with a metal belt or chain running between them. One pulley is connected to the engine (input shaft), the other to the drive wheels (output shaft). The halves of each pulley are moveable; as the pulley halves come closer together the belt is forced to ride higher on the pulley, effectively making the pulley's diameter larger.

Changing the diameter of the pulleys varies the transmission's ratio (the number of times the output shaft spins for each revolution of the engine), in the same way that a 10-speed bike routes the chain over larger or smaller gears to change the ratio. Making the input pulley smaller and the output pulley larger gives a low ratio (a large number of engine revolutions producing a small number of output revolutions) for better low-speed acceleration. As the car accelerates, the pulleys vary their diameter to lower the engine speed as car speed rises. This is the same thing a conventional transmission does, but instead of changing the ratio in stages by shifting gears, the CVT continuously varies the ratio -- hence its name.

Driving a car with a CVT

The controls for a CVT are the same as an automatic: Two pedals (gas and brake) and a P-R-N-D-L-style shift pattern. When driving a car with a CVT, you won't hear or feel the transmission shift -- it simply raises and lowers the engine speed as needed, calling up higher engine speeds (or RPMs) for better acceleration and lower RPMs for better fuel economy while cruising.

Many people find the CVT disconcerting at first because of the way cars with CVT’s sound. When you step hard on the accelerator, the engine races as it would with a slipping clutch or a failing automatic transmission. This is normal -- the CVT is adjusting the engine speed to provide optimal power for acceleration. Some CVT’s are programmed to change ratios in steps, so that they feel more like a conventional automatic transmission.

Advantages of the CVT

Engines do not develop constant power at all speeds; they have specific speeds where torque (pulling power), horsepower (speed power) or fuel efficiency are at their highest levels. Because there are no gears to tie a given road speed directly to a given engine speed, the CVT can vary the engine speed as needed to access maximum power as well as maximum fuel efficiency. This allows the CVT to provide quicker acceleration than a conventional automatic or manual transmission while delivering superior fuel economy.

Disadvantages of the CVT

The CVT's biggest problem has been user acceptance. Because the CVT allows the engine to rev at any speed, the noises coming from under the hood sound odd to ears accustomed to conventional manual and automatic transmissions. The gradual changes in engine note sound like a sliding transmission or a slipping clutch -- signs of trouble with a conventional transmission, but perfectly normal for a CVT. Flooring an automatic car brings a lurch and a sudden burst of power, whereas CVT’s provide a smooth, rapid increase to maximum power. To some drivers this makes the car feel slower, when in fact a CVT will generally out-accelerate an automatic.

Automakers have gone to great lengths to make the CVT feel more like a conventional transmission. Many CVT’s are programmed to simulate the "kick-down" feel of a regular automatic when the pedal is floored, and some CVT’s offer a "manual" mode with steering-wheel-mounted paddle shifters that simulates a conventional stepped transmission.

Because early automotive CVT’s were limited as to how much horsepower they could handle, there has been some concern about the long-term reliability of the CVT. Advanced technology has made the CVT much more robust. Nissan has more than a million CVT’s in service around the world and says their long-term reliability is comparable to conventional transmissions.


This video describes the basic principle operation of a CVT.

Photos from JR Auto Repair Service's post

Photos from JR Auto Repair Service's post



JR Auto Repair Service's cover photo

JR Auto Repair Service's cover photo


4074 Walney Rd
Chantilly, VA

Opening Hours

Monday 8am - 7pm
Tuesday 8am - 7pm
Wednesday 8am - 7pm
Thursday 8am - 7pm
Friday 8am - 7pm
Saturday 8am - 7pm


(703) 595-0029


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