However, it is important to get it right, because getting the offset wrong risks badly damaging the replacement wheels and tires as well as suspension components, and can put the driver at serious risk of a blowout. Any of these factors, if mishandled, can severely affect your reputation, not to mention cut down on repeat business! Positive offset means that the mounting plate is in the outside half of the wheel, toward the wheel face.
Most OEM wheels, and most wheels in general, will have a positive offset. Negative offset is generally seen in very deep-dish or deep convex aftermarket wheels. While most aftermarket wheels are made in multiple offsets, most OEM wheels only come in the offset that is correct for the specific car for which they are made.
Closely related to offset is the concept of backspacing. Offset and backspacing are often spoken of as if they are the same thing, but they are very different. Backspacing is defined as the distance between the mounting plate and the inner flange of the wheel.
Backspacing is, therefore, the combination of the offset and the wheel width. This comes into play if the new wheels are wider than the old, as the offset may need to change to compensate for the greater width. If you get the offset or backspacing wrong when you are procuring and installing new wheels for a customer, you run the very real risk of having the wheel sit too far inside the wheel well, causing the inner edge of the wheel and tire to rub against the suspension.
Tire rub is even worse, as it will very quickly rip up the inside sidewall of the tire, an area where the damage is very hard to detect until the tire blows out. What you do need to keep in mind is that more negative offset, i. Usually, this will not cause a problem, although it might result in a pretty funky look. In contrast, too much positive offset is a danger, as it will push the wheel farther in toward the suspension.
Spacers do not lower offset, they increase the backspacing of the wheel which pushes it farther out or closer to the fender. Offset is a measurement from the mounting surface to the center of the wheel so with out changing the wheel dimensions, how would you change offset?
The more positive offset you have the further the wheel is going to be in from the fender. The more negative offset you have the further the wheel is going to stick out. Zero offset is your center line. Negative Offset The wheel will also stick out from the truck. Keep in mind that some states require fender flares to cover the width of the wheel and tire. Tires cannot project beyond the vehicle at all without some sort of protection.
Relying on just this rule, you might get the impression that the tire can stick out past the fender as long as there is a mud flap behind it. Negative offset is when the hub mounting surface is toward the back or brake side of the wheels centerline. Having a negative offset on any width wheel is generally considered a very aggressive offset.
This is so because of the more inward location of the contact point causing the wheel as a whole to poke more outward than a zero offset wheel of the same width would. A zero offset wheel has the hub mounting surface at the centerline of the wheel. They are typically wider than stock wheels to accommodate wider and larger diameter tires. Having zero or positive offset will usually cause the wheel to make contact with the brakes, suspension, or steering components.
For example, an 8 inch wide wheel with a 4. This is the offset. Compare this to your wheel well to see if it fits. Offset is simply the distance from the hub mounting surface to the center of the wheel.
Backspacing is the amount usually measured in inches of distance that the mounting surface of the wheel is away from the inner edge of the wheel. Backspacing is defined as the distance from the hub mounting surface to the inside lip of the wheel measured in inches. More backspacing puts the tire in closer to the center of the truck.
A related term is known as offset, which relates the hub mounting surface to the centerline of the rim. Take a straight edge and lay it diagonally across the inboard flange of the wheel.
Take a tape measure and measure the distance from where the straight edge contacts the inboard flange to the hub mounting pad of the wheel. This measurement is backspace.
Measurement of wheel offset can be positive or negative and is described in millimeters. An offset of 0 describes a wheel mounting pad positioned in the center of the wheel. A negative offset indicates the mounting pad is is positioned on the hub side of the centerline, closer to the vehicle.
They are a cheap and easy way to improve wheel fitment and increase the track width of your car. However, they are also a fast and easy way to ruin the geometry of your car and can badly affect your handling. The main issue with a wheel spacer is that it moves the wheel to a wider position whilst the rest of the suspension arms remain in the same place.
In particular, the king pin inclination axis remains in the same place. Therefore, fitting a wheel spacer moves the wheel outboard and alters the scrub radius of the car. It is important to know whether your car currently has negative or positive scrub radius and ideally how much it has.
Fitting a wheel spacer will increase the positive scrub radius at the front wheels which has some unfavourable consequences. If your car already has a bit of positive scrub radius then the wheel spacer will increase it. An increase in positive scrub radius increases the forces on the steering rack under braking conditions. Any bumps in the road will also be amplified through the steering wheel, making the steering jerky and more unpredictable. Twitching wheels when braking can cause the tyre to lose grip and ultimately can cause the wheels to lock up and slide.
An increase in positive scrub radius also causes the wheel to gain positive camber when the wheels are being turned, reducing grip in corners on the front wheels and producing understeer.
If your car has the more favourable set up of negative scrub radius then installing a wheel spacer can cause bigger issues. The outward movement of the wheel can make a negative scrub radius become zero. This is the worst position for it to be in. A zero scrub radius can cause squirm. This is where a scrubbing action occurs on both front tyres in opposite directions which can create unpredictable handling in corners and can lead to understeer too.
Secondly, installing wheel spacers on a car increases the leverage on the wheel bearing. The larger the spacer, the larger the leverage becomes. This reduces the life of the wheel bearing as they are not made to take leverage forces and can therefore wear faster, increasing rolling resistance and power loss of the car. Finally, the wheel spacer moves the wheel further away from the damper mounting point. This means that the wheel will have a larger effect upon the damper and will act upon it with more leverage.
This effectively makes the spring and damper softer and less effective on the wheel. This means that the car can roll more on corner entry and exit and feel generally softer out on track or on the road. However, there are some positive aspects to fitting wheel spacers to your car that can prove beneficial.
Moving the wheels outboard increases the track width of the car. The increase in track width also lowers the roll centre of the car and therefore increases the amount of cornering force that the car is able to carry through its tyres. Due to being able to manage an increase in cornering G force, it means that it is possible to corner at higher speeds. Installing the spacer on the rear wheels means that the negative aspects take less effect because the scrub radius effects are not present at the rear wheels.
Therefore if your car is suffering from oversteer then installing wheel spacers might be a quick and cheap way of reducing that. If you want to install wheel spacers, then we highly recommend the following wheel spacers that can be viewed by clicking on the image below:.
Interesting read and backs up what I have said about wheel bearing pressure. Two things, one, will altering the offset of wheels do this same thing? And two, how would you suggest effectively increasing track width without compromising the handling? Thanks and look forward to your reply. Hi Stig, thanks for the comment. Yes increasing your wheel offset without increasing the tyre width will act the same as a spacer.
The best way we can suggest to increase track width is by installing adjustable length arms to move the wheel and hub assembly outboard, increasing track width.
However, if you must be willing to check your geometry settings after doing this as further adjustments and modifications may be required when this is done. I have a Ford Focus year , sligthly oversteering. Installing only on the rear wheels the spacers, 5mm or 10mm, can I reduce oversteer? Thanks for your comment.
Installing a wheel spacer could help with the oversteer as it will increase your rear track width helping with LLT. However, you would be better observing your tyre behaviour and trying to solve the oversteer by optimising rear camber, toe or damper settings. Thanks for reply. I see that my car has a rear track large mm, front track mm. Can be this one of the reasons for its oversteering behaviour? If I install spacers only on the front, in order to equalize the rear and the front track, can be a valid solution?
Excuse me for my English. Installing spacers on the front will provide more track width and therefore likely reduce understeer and increases the tendency to oversteer. However, it is worth noting that installing spacers will affect multiple other aspects of your geometry so you should try to solve the problem using roll bars, dampers and geometry before installing spacers. Hallo, nice article there. One question: would a positive scrub radius of mm on the REAR axle be noticeable or too much?
I guess for the rear axle this variance is not so problematic correct? Look forward to your advice. Thanks and Regards. Yes the effects upon the rear axle are not as bad as the front axle. The main negative for installing on the rear axle is the increased loading on the wheel bearing. However, you will benefit from increased rear track width. Wheel spacers will always affect geometry and alter handling and response slightly.
Could these cause some long term damage on my suspension, tires,…? Hi Jan, thanks for the comment. The reduced understeer will be a result of the now wider track width across the front wheel which will reduce understeer slightly.
The installation of the spacers will have altered your scrub radius which will alter how your wheel pivots. It will likely cause slightly more scrub to your tyres and make them wear faster when turning the wheel.
However, it will take a while for a noticeable difference to occur. The increase of 8mm will slightly affect handling in that the feedback through the steering when applying brakes will increase. Furthermore, any bumps in the road pushing back on the tyre will be amplified through the steering wheel. The increase will slightly increase the load upon the wheel bearing too but this should be quite negligible. Being FWD would it be a problem.. Hi Carey, thanks for the comment. Fitting the 15mm spacers will affect your scrub radius and will therefore provide more feedback through the steering wheel when braking and hitting bumps out on track and the road.
The extra load on your bearings will be minimal though. If you are going to go for wheel spacers then make sure to get hub centric spacers as this will remove any unwanted wheel wobble.
Hi, wanted to know what would be scrub radius of stock oem vehicle without alteration. For example toyota kijang or innova MUV scrub radius of this stock vehicle would be? Hello there thanks for the info. Was planning on putting a maybe a three quarters of an inch spacer on the rear. Will that affect anything. Hi, Thanks for the comment. If your car is used mainly for road use then you wont feel much difference and the extra strain on the wheel bearing should be minimal with that size of spacer.
If you use the car for track use then you might feel some difference with regards to steering and feel at the front end. I wanted to bring the rears out about 20mm and leave the front as is.
Would this create much issues? And should I consider the front as well or stick with just the rear? Hi Paul, thanks for your comment. Spacing the rear wheel as less negative impact on geometry than on the front wheels so that would be the best case. You might experience a slight increase in load on your wheel bearing but you will benefit from a wider rear track width having more rear grip in corners.
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