Clearance, Brakes, and Practical Setup Considerations
Running 15 inch wheels on the Toyota GR Yaris is a common requirement for gravel rally, winter driving, and ice track use, but there are a number of things to take into account when aiming for this setup. Clearance constraints around the front brake caliper, front suspension arm design, front brake dust guards and wheel offset all play a critical role in whether a given setup will fit reliably.
This article outlines the key considerations and limitations when fitting 15" wheels to the GR Yaris, based on real-world fitment checks and development experience.
These insights apply for both the Gen1 and Gen2 GR Yaris as the issues that arise are the same in this context for both platforms. The front brake caliper, knuckle, front lower control arm and dust guard remain unchanged from the Gen1 to the Gen2.
Why 15" Wheels on the GR Yaris?
The primary reasons for moving to a 15" wheel setup are:
- increased tire sidewall for compliance on gravel, snow, and ice
- improved tire availability in the case of gravel or studded rally tires
- better impact resistance compared to low-profile road tires
For motorsport use cases, the benefits are clear, but the constraints must be understood.
The Facts for GR Yaris Wheel fitment
The numbers and values that set the basis for wheel fitment on the GR Yaris:
- Wheel bolt pattern 5 x 114.3mm (5 x 4.5 in)
- Center Bore 60.1mm
- Wheel stud thread M12 x 1.5
- Wheel nut tightening torque 103Nm
These values define the choice of wheels and fasteners that can be used. As a side note, many owners are using Mitsubishi Lancer Evolution X wheels when switching to a 15 inch setup. The important thing to keep in mind in this case is the difference in wheel center bore. The Evolution X has the same 5 x 114.3mm bolt pattern, but runs a 67.1mm center bore making the use of a centering ring necessary.
Brake Clearance: The Primary Limitation
The factory GR Yaris braking system is the single biggest obstacle for 15" wheel fitment.
Front brakes
The OEM front brake package is large for the vehicle size. 15" wheels will not clear the front caliper and disc without modification. Clearance is affected by:
- disc diameter (356mm in stock form)
- caliper shape
- wheel barrel shape (wheel model specific)
As a result, front brake modifications are required to enable reliable 15" wheel fitment. This can not be easily achieved and requires a bit of engineering and new componentry. We have developed a bespoke solution to these issues and will explain it in the second half of the article.
Rear brakes
In the rear the fitment is easy and requires no modifications. 15 inch wheels can be used with the OEM brake system.
Suspension and Steering Clearance
Beyond brakes, 15" wheel setups must also be checked against:
- front lower control arm clearance
- front dust guard clearance
- front fender edge clearance at full compression
This is especially important for:
- high sidewall gravel tires
- studded winter tires
Known issues and solutions
We will now go into more detail to explain each problem specifically and define the known solutions.
The front lower control arm
On the GR Yaris the front lower control arm can cause fitment issues with wheels under 16 inches in diameter. The arm itself can come into contact with the inside edge of the wheel, in some cases this prevents the wheels from being fitted. Depending on your wheel choice and the severity of the contact there are a number of options to fix this.
Front lower control arm clearance issue observed during 15" wheel test fitting on the GR Yaris
Solution 1: Trimming the lower control arm
The first option is the case of light contact is to trim the outermost edge of the arm slightly with an angle grinder. This is only to be done in cases where the contact is extremely light or there is no contact, but a lack of adequate clearance to the wheel.
Solution 2: Repositioning of the arm
The second option is to reposition the arm and the ball joint. This is done by unbolting the 3 bolts holding the arm to the ball joint and reassembling the parts the opposite way with the arm placed above the ball joint. This is the preferred option to trimming and does yield much more added clearance, but depending on the suspension setup of the car there can be clearance issues between the arm and the knuckle. It is advised to check clearance through the complete suspension travel after performing this modification.
Solution 3: Avoiding the arm issue
The easiest way to avoid the clearance issues related to the front A-arm is to choose wheels with the correct offset. Through our testing we have found that the correct offset to use in order to avoid contact with the arm is ET15 with a 7 x 15 inch wheel. For the rear we can recommend an ET10 wheel in 7 x 15 format for the car to look balanced from a visual standpoint.
Many 7 x 15 inch rally wheels in GR Yaris fitment are offered with an offset of ET28, this is the normal fitment for a Mitsubishi Evolution X and will cause the wheel to come into contact with the front lower control arm on the GR Yaris.
GR Yaris with 7 x 15 inch ET15 (front) ET10 (rear) wheels fitted providing visual balance
The front brake dust guards
The OEM front brake dust guards are too large to be able to fit 15 inch wheels. The options here include:
- trimming the dust guards in place
- removing the dust guards entirely
Solution 1: Trimming the dust guard
For most owners the easiest option is to use a pair of steel shears or an angle grinder to trim the guards in position to allow for clearance. When we do installation of our GR Yaris Small Brake Kit for customers we take the time to actually remove the dust guards in order to achieve a cleaner install and a more controlled process.
Solution 2: Removing the dust guards
The main limitation when removing the guards will be the driveshaft. In the case of the GR Yaris the dust guards are fitted between the wheel bearing and the knuckle. In order to remove the guards the wheel bearing bolts must be opened. This can be done with the driveshaft in place, but in this case the dust guard must be cut to allow it to pass over the driveshaft. This is fairly difficult to do due to the lack of space.
The wheel bearing nut
The main issue with removing the wheel bearing entirely is the driveshaft nut which is known to damage the driveshaft threads when opened. It can be done without damage, but care must be taken to open the driveshaft nut locking indents before trying to turn the nut.
Close up of GR Yaris Front driveshaft nut locking indent
Unbolting the wheel bearing
The wheel bearing itself is not difficult to remove. It is held in place by three bolts which can all be easily opened when the driveshaft nut is off. It can be done with the driveshaft in place and untouched but space is extremely tight and special tools are required to avoid damaging the hardware.
Safety and verification notes:
Engineering a Solution for 15" Wheel Use
To address these constraints, we developed a dedicated GR Yaris small brake kit specifically engineered to allow 15" wheel compatibility without compromising functional requirements for gravel and winter use.
Key engineering considerations behind the kit include:
- reduced overall brake package envelope to clear common 15" wheel barrel profiles
- disc sizing chosen to maximize thermal capacity under packaging constraints
- disc blanks chosen based on maximal cooling efficiency
- compatibility with OEM caliper and brake pads
The focus was not simply on reducing size, but on creating a brake system that is easy to fit and keeps as much of the original Toyota components as possible. This way the cost to performance ratio is maximized.
We will now go into more depth regarding the challenges we faced during the development process and which solutions were created to address them.
Challenge 1: Caliper fitment
From the start we knew we wanted to keep the original Toyota calipers. This was both form a cost and a performance standpoint to allow us to keep running OEM Toyota Brake Pads or aftermarket pads made specifically for the GR Yaris.
In order to determine the maximum brake disc diameter we could fit under a 15 inch wheel we had to look at the caliper positioning. With the OEM Toyota calipers we can go as large as 314mm, have full contact between the brake pad and disc, and still fit within the 15 inch wheel. When comparing this to the OEM GR Yaris brake disc with a 356mm diameter we are only reducing the disc diameter by 42mm to go from an 18 inch wheel to a 15 inch.
Challenge 2: Caliper Mounting
To fit the calipers in the desired position we needed to engineer a new caliper adapter. We chose aluminium EN 6082 as the material for this due to the strength, light weight, reasonable price and easy machinability.
The new adapter needed to use the original mounting hardware in order to make fitment as simple as possible. It also needed to clear the knuckle and brake caliper in order to fit on the car. To design this we used CAD software and 3D scanning.
Neomatic GR Yaris Small Brake Kit caliper mounting bracket fitted with OEM hardware
Challenge 3: Brake disc choice
The blanks that we use for our Small Brake Kit are produced by Rotinger, more specifically their Graphite line. We chose this blank based on the large slotted cooling vanes and proven quality of Rotinger products.
The blank matches GR Yaris fitment with the same 28mm thickness as the OEM discs, but at the same time actually provides more internal cooling volume than the OEM units. Maximizing internal cooling volume was one of our main targets with this kit as this is important for reducing brake fade in motorsport applications. The 15 inch wheel limits maximum brake performance and endurance quite heavily, specially on stage rally cars.
Neomatic brake disc with larger cooling volume on the left with OEM Toyota 356mm disc on the right
Challenge 4: Brake Disc Fitment
Our chosen discs are integral-hat type, meaning we must make sure the hat of the disc clears the caliper in the new, modified position. To do this we machine the hat portion of the disc to a slight angle.
Another area where modifications are required is the inside surface of the disc, facing the wheel hub. To make sure the disc fits onto the hub as designed we increase the flat area inside the disc slightly up to a 168mm diameter.
The outside diameter of the disc is reduced down to 314mm as this is the maximum we can fit when using the OEM caliper.
Neomatic GR Yaris Small brake disc production reference drawing showing the areas to be machined
The Solution
Our GR Yaris Small Brake Kit solves the main issue when fitting 15 inch wheels to a GR Yaris - the size of the front brakes. The 314mm disc size and large internal cooling volume paired with the OEM brake caliper and pads maintain strong and lasting braking performance in even the toughest conditions.
Our kit consists of:
- Specially machined brake discs
- Caliper adapters for OEM caliper fitment
More information regarding our solution can be found on the product page:
Neomatic Toyota GR Yaris Small Brake Kit
Neomatic GR Yaris Small Brake Kit complete with caliper adapters and 314mm discs
Key Takeaways
The following points summarize the practical considerations discussed above.
• The OEM GR Yaris front brake package prevents 15" wheel fitment without modification
• Brake system packaging is the primary constraint, followed by FLCA positioning and wheel offset
• Suspension and steering clearance must be verified dynamically, not just statically
• Purpose designed small brake kits enable reliable 15" wheel compatibility
• All fitment assumptions should be validated through physical testing