AIWheelTech / Fitment calculators / Big brake kit clearance
Free tool

Big brake kit clearance.

Measure your calipers, print a cut-out template to hold inside a wheel, or send us your readings and name a wheel for us to check. Free, no signup.

Prints at true sizeA4 or US LetterWe check a wheel for you
1

Measure

Print the sheet and take five measurements, A to E, front and rear.

 2

Make templates

Turn A to E into true-scale wheel-fit cards to cut out and turn inside a wheel.

 3

Ask us to check

Send your measurements and photos, name a wheel, and we check it against your kit.
Step 1

Measure the caliper.

Five measurements, A to E, front and rear, with the wheel off. A rule and a straightedge are all it takes. A is what the back of the spokes has to clear, and B plus C is what the inside of the barrel has to clear.

How to measure a big brake caliper: A from the hub mounting face to the caliper face, B from the hub centre line to the caliper lower edge, C on to its outermost point, D and E the chamfer on its top outboard cornerBRAKE CALIPERROTORHUBSTUDHUB CENTRE LINEHUBMOUNTINGFACEABCDE
AHub face to caliper face
From the hub mounting face, the flat face the wheel bolts against, out to the outer face of the caliper. Lay a straightedge across the caliper face and measure back to the hub face. If the caliper face sits behind the hub face, tick "behind".
BHub centre to the caliper's lower edge
Measure from the edge of the hub spigot (the raised ring in the middle) to the caliper's lower edge, then add half the spigot diameter.
COn to the caliper's outermost point
From the lower edge to the top of the caliper. B and C together are hub centre to the top of the caliper.
DEThe chamfer on the top outboard corner
Its height (D) and width (E). Leave them blank if the corner is square.

Count everything on the caliper: bleed nipples, brake line fittings, bridge bolts and badges. A caliper with more steps than the drawing can take extra readings in step 2. Car on axle stands or a lift, never on a jack alone.

Paper
Big brake kit clearance: measuring sheetWheelTechFill this in with the wheel off, front and rear. Then make a cut-out wheel-fit template, or send it to uswith photos and name a wheel for us to check, at aiwheeltech.com/tools/big-brake-kit-clearance.html050100Check your print first. This bar must measure exactly 100mm. If it does not, print again at 100% (actual size) withno page scaling.BRAKE CALIPERROTORHUBSTUDHUB CENTRE LINEHUBMOUNTINGFACEABCDEDrawing not to scale. Street side on the right.What to measure, in mmAHub mounting face to the outer face of the caliper. Lay a straightedgeacross the caliper face and measure back to the flat face the wheelbolts against. Tick "behind" if the caliper face sits behind it.BHub centre line up to the lower edge of the caliper. Measure from theedge of the hub spigot (the raised ring in the middle) and add halfthe spigot diameter.CFrom the lower edge of the caliper to its outermost point. B and Ctogether are hub centre to the top of the caliper.DHeight of the chamfer or step on the caliper’s top outboard corner.EWidth of that chamfer. Leave D and E blank if the corner is square.Wheel off, car on axle stands or a lift, never on a jack alone. Counteverything on the caliper: bleed nipples, brake line fittings, bridge boltsand badges.The carRegistrationMake and modelYearEngineMeasurements and kit, front and rearFRONTREARAhub face to caliper face, mmbehindbehindBhub centre line to caliper lower edge, mmCcaliper lower edge to outermost point, mmDchamfer height, mmEchamfer width, mmKit brand and caliper modelKit or part numberPistons per caliperDisc diameter x thickness, mmStepped caliper? Add a reading for each extra step on the website: R from the hub centre line, and its depth from the hub face.The wheel you want us to checkWheel brandModelSize: diameter x width, ETe.g. 19 x 8.5 ET45PCDe.g. 5x112Photos to take:caliper straight onfrom the side, tape in shotthe hub with the wheel offkit box or part number labelFree from AIWheelTech. A template made from your own measurements is a guide, not a guarantee: trial fit every wheel, turning it a full revolution by hand,before the car is driven. aiwheeltech.com/tools/big-brake-kit-clearance.html

Print at 100% or "actual size", with page scaling off. The bar at the top must measure 100 mm before you trust anything else on the page.

Step 2

Make your wheel-fit templates.

Type in A to E from your sheet, front and rear. Each axle becomes a true-scale card to print, glue to card and cut out, with the caliper, rotor and hub drawn, a spacer foot and a 100 mm bar. The same numbers go with your check in step 3.

The cut line keeps this much room all round the caliper. Between two readings it keeps the deeper one, so it errs on "does not fit".
  1. Print at 100% and check the bar measures 100 mm.
  2. Glue the print to thin card and cut along the dashed line. Fitting a spacer? Leave the spacer foot on and cut it at the line for the spacer's thickness.
  3. Lay the wheel face down on something soft. Stand the card on the wheel's mounting face, the flat face that bolts to the hub, with its corner in the middle of the centre bore.
  4. Turn the card slowly through a full circle. Anything touching it means no fit. Touching the back of a spoke? A spacer may give the room. Touching the inside of the barrel? A spacer will not.
  5. Stick-on balance weights sit right where the caliper passes, so allow room for them. Then trial fit the wheel and turn it by hand before the car is driven.
Paper

Want a PDF? Print, then choose "Save as PDF" as the printer. It keeps the true size.

Step 3

Ask us to check a wheel.

Send your readings and a few photos, name the wheel you want, and we check it against your kit by hand. Free, with a reply by email, usually within one working day.

Email us your readings. Send your A to E measurements, front and rear (or a photo of the filled-in sheet), a few photos (the caliper straight on, from the side with a tape measure in shot, the hub with the wheel off, and the kit box or label), the brake kit, and the wheel you want with its size and offset, to [email protected]. We check it against your kit by hand and reply by email.

Email us your readings

Straight answers

Questions about the tool.

Will the template print at the right size?
Yes, if the print is set to 100% or "actual size" with page scaling off. Every printed page carries a 100 mm bar: measure it with a ruler before you cut anything. If it is not 100 mm, the print was scaled.
What if the caliper face sits behind the hub face?
Tick "behind" next to A. A caliper that sits behind the hub face cannot reach the back of the spokes, so only its radius matters, against the inside of the barrel.
How much clearance should I keep?
The tool starts at 3 mm round the caliper. Stick-on balance weights sit on the inside of the barrel where the caliper passes, so allow for them, and always trial fit the wheel and turn it by hand before the car is driven.
Can a spacer fix a big brake kit that touches the wheel?
Only where the caliper touches the back of the spokes. A spacer moves the wheel outwards, which adds room at the spokes, but the barrel stays the same size. The big brake kit clearance guide explains both gaps.
Is the wheel check really free?
Yes. Send your readings, photos and the wheel you want, and we check it by hand and reply by email. There is no charge and no obligation to buy anything.
Why do you keep the measurements?
Brake kit makers measure their calipers in different ways and wheel makers do not publish clearance for every size. Each check adds a measured kit to our records, so the next person with the same kit gets an answer faster. Your name, email and phone are used only to reply to you.

Big brake kit clearance guide

The two gaps a caliper has to clear, and what a spacer can and cannot fix.

Camber & spacer calculator

Where the wheel sits with a spacer fitted.

Concave alloy wheels

Why a concave face leaves less room for a big caliper.
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