Do I need wheel spacers for my brake upgrade, or will my wheels fit with a BBK? What size spacers do I need?

Big Brake Kits (BBKs) include larger rotors and larger calipers to help improve braking performance.

There are two factors to consider: Diameter and Backspacing

Diameter

Because the rotors are larger, the calipers will mount farther away from the center of the wheel hub, and you need to consider the barrel size of the wheel when up-sizing brake kit. In general, a really loose rule of thumb we use, is to look at the rotor size of the BBK, maybe 13" for example, and add 3" to that size to account for the caliper to fit over it. Your wheel barrel should probably be 15" or more. Most of the time this is really easy to estimate but if the measurements seem close/tight don't try to to guess the barrel size based on the wheel diameter. Don't try to estimate the barrel size with the wheel on the car. 

Take the wheel off and measure the inside diameter near the spokes.

If the wheel barrel is too small for the brakes, you need new wheels that are designed to accommodate larger brakes.

Backspacing

The larger calipers you are using are probably wider than the stock one and sometimes it comes proud of the rotor face and inch or more. You can ask for all kinds of dimensions, measurements, and templates from the brake manufacturer and sometimes this information can be helpful in estimating the caliper-to-spoke clearance you will be faced with. But sometimes they won't be helpful and you will not really know if there is a enough room.

The issue of caliper spacing is a little more of a difficult issue to address without having parts in hand. There are a few concerns with the wheel's backspacing to consider: Spoke design, offset, and width.

Spoke design:

Most of the concern comes down to the spoke design. The shape of the spokes. If the spokes go straight out toward the barrel, such as a higher offset wheel that has a larger lip on it, then there is going to be less room for brakes. It the spokes arc away from the hub and are tinner, there is ofter more room for the wheel in these cases. Take the wheel off and see how much the spoke arcs away from the hub to get an idea if the wheel has a design generous for larger brakes.

Offset:

Sometimes you will have a wheel that doesn't have a generous spoke-design, but also has a low offset that pushes the wheel out more (offsets with lower numbers stick out more). Lower offset wheels inherently have more room for brakes than ones with higher numbers. So a +35mm offset wheel has more room for brakes than a +45mm wheel). If you are buying wheels and want to fit larger brakes and want plenty of room for the brakes, get a lower offset if you can fit them.

Width:

Sometimes people want to think that a wider wheel has more room for brakes. In some cases this is true, but because spoke design and offset are much larger factors, please don't be fooled into thinking the width will be enough to save you. Unless you are going 1.5" wider or more, the width being any help at all is not a reliable assumption.

So for the reasons of spoke design, offset, width, and unreliable/hard to interpret brake kit dimensions,;it is best to have parts on and to test fit.

Spacers

If your wheels are not accommodating your brake kit, but the barrel is large enough, then getting spacers to move the wheel outward (effectively lowers the offset of the wheel) will often be your savior!

Choosing a spacer is to be covered in another article, but the short notes are:

• If you have the brakes on the car and try to put the wheel on over them, and there is contact, you will probably scratch the calipers and get pissed. Do this with a lot of caution.
• If you have 1mm or less of clearance, that is maybe not enough to really feel confident, in our opinion. Shoot for a 2mm or more space between the caliper and wheel.
• Larger spacers will reduce the thread engagement that the wheel nuts hold the wheel on with. We sell spacers in 3mm and 5mm sizes which can work with stock Honda studs ok (depending on how thick the hub of the wheel is). Anything more than that is unsafe and you should use extended studs or wheel hub spacers or adapters instead.

What size spacers do I need?

This is really tempting to ask. The answer is we don't know. You are going to need to do some trial and error. This is how it should play out:

1. Inspect your wheels and decide if they have enough room for larger brakes.
2. Decide on a brake kit and buy it.
3. Test fit the brakes on the car and the wheel over the brakes. If you have room, run it!
4. If you don't have room, estimate the spacer size you need, and buy some spacers. If you want to save time you can get a couple different size spacers to use on install-day to have your bases covered.
5. We can tell you from experience that some extra random spacers in the tool box might not save the day today, but they will someday! Consider holding on to any spacers you didn't use and we can promise you one day you will be glad you had them.