Wheel Temperature

[Palustris]

Just had a brake service as we had a squeaky brake. Out of interest, how hot do front wheels get? Just drove home (3 miles or so) and the front wheels seemed extremely hot to me.

[gingejbee]

Depends on how much braking you did...if not a lot of braking and wheels are very hot, could mean the pads are pressing too firmly on the discs.

[bhg481]

It's mainly braking which heats up the front wheels, although there will be some heat bleeding from the engine. When you brake to a halt the whole of the kinetic energy of the car is converted to heat at the brakes, mainly the front brakes. Since the wheels are connected to the brakes the wheel gets hot as well.

[gingejbee]

^^^by that, I mean "binding" even when not braking.

[bhg481]

gingejbee has a valid point - I think he means the pads could be in constant contact with the disc because of a sticking caliper. It might be interesting to stop the car just using the handbrake and feel how hot the front wheels are then. If you do that, be careful. Handbrakes are nowhere near as effective as footbrakes and you will have no servo-assistance; try it somewhere very quiet.

[bhg481]

A further thought - are they both roughly the same temperature? It's most unlikely that both wheels will have a sticking caliper; at the same time there will probably be a difference between them due to the way the air flows under the bonnet. If one is a lot hotter than the other first prize goes to ginge.

[Hopkirk]

I would jack up the front wheels one by one and see if they spin freely.

[douglas9401]

Rather than all of the above, take it back to the garage and get them to check it over.

[Palustris]

Thanks. Both wheels were equally hot, as far as it is possible to tell. Very narrow country lane with more traffic than usual so could have been a lot of braking. No difference in acceleration or speed, again as far as I could tell.
No jack so cannot try the wheel spinning. Will try the hand brake thing tomorrow. This road is normally very quiet.

[Arrods]

Don't forget that some cars' hand brakes work off the front brakes. My Mazda does and possibly some Citroens too.

[bhg481]

Arrods - I've never come across that; If it's true of Palustris's car the test won't work.

[Arrods]

Hi bhg41. Just thinking again about my post, my Citroen BX certainly had front disc parking brake operation and I based my comment about my Mazda 6 when someone mentioned the similar (unusual) system on my Mazda. I haven't been able to confirm that either way so I'm not sure now.

I guess when you think about it the handbrake system on cars with discs all round will operate differently from the conventional rear drum system, so not sure why the handbrake always needs to operate the rear ones. But it does appear that most cars operate the rear discs as with cars with rear drum brakes.

A bit off thread, but it will be interesting to find out how the OP fares.

PS. Remember the BX advertising slogan something like 'Loves driving, hates garages'? Mine loved garages!

[bhg481]

I remember when all-round disc brakes first started to appear there were instances of cars rolling away downhill after they had been left because the discs shrank (got thinner) as they cooled making the brakes loosen. The Vauxhall Carlton and Omega that I had in that era had a special drum for the handbrake as well as the disc for the footbrake to avoid the problem (drums shrink so pull the brake on harder as they cool).

[Gizmonster]

By the very nature of their design and how they work, brakes do naturally get quite hot.

Have a read of this:

http://www.thedrive.com/tech/8482/your-cars-brakes-get-really-really-hot