Calipers expanding when hot? How much?

[crobaa]

Hi guys, I've just installed spoon monoblock calipers on my car with sw388 wheels, the clearance between caliper & spoke is max 1mm. The wheel currently spins freely and doesn't hit the caliper at all, I'm concerned at a track day/aggressive driving the caliper will expand and touch the wheel. Anybody have any experience with this? I was thinking the wheel would also expand considering its bolted to this disc which is the hottest part

[bennjamin]

I dont think this is ever an issue in the real world mate. Ive only ever heard of brake discs or pads being effected by excessive heat - and this is to material build up. If you are worried - i would definitely run a thin spacer say 2-3mm

Try these

Linear expansion

To a first approximation, the change in length measurements of an object ("linear dimension" as opposed to, e.g., volumetric dimension) due to thermal expansion is related to temperature change by a "linear expansion coefficient". It is the fractional change in length per degree of temperature change. Assuming negligible effect of pressure, we may write:
where is a particular length measurement and is the rate of change of that linear dimension per unit change in temperature.
The change in the linear dimension can be estimated to be:
This equation works well as long as the linear-expansion coefficient does not change much over the change in temperature . If it does, the equation must be integrated.

[crobaa]

^ good work on reminding me that I'm not a scientist lol. I know alloy does expand at high temps, but in theory the wheels should also expand, normally I wouldn't be concerned but the wheels and calipers are expensive the clearance is very tight. Ideally I'd like to run no spacer if I could get away with it.

[curtis265]

the wheels will expand as well dude, although at a slower rate

still though, a 1mm differential is a lot

[crobaa]

Would you be concerned based on the above photo?

[crobaa]

Actually on second thought, wouldn't the wheels just expand in every direction? There's nothing to say they'd expand away from the calipers is there? So in theory if they both expanded .5mm I'd be in trouble? The question now is .5mm a realistic possibility of expanding?

[mocchi]

i rkn will be far less than 1mm.

engine piston is an example maybe.
cast aluminium with clearance less than 0.05mm in cyl bore.

[crobaa]

So I'm safe? I'll send you the bill if they get messed up Oscar

[grifty]

Don't think they will expand by 1mm, like Oscar said, think about the bearings in a motor and piston/cyl bore clearance.

You might be be able to get 1mm expansion by using a oxy torch lol

[trism]

From about 5 minutes of googling, seems like most brake places recomend a minimum of 2mm

[mocchi]

So I'm safe? I'll send you the bill if they get messed up Oscar

inb4lawsuit

byp told me, not my fault

[crobaa]

Lol Oscar!

Is there such a thing as 1mm spacer? I really dislike running spacers so would prefer the smallest one possible. I actually test fitted with one washer on each stud yesterday and the center of the rim was still able to seat on the hub. Opinions on 1 washer spacer?