"Urambo Tauro" (urambotauro)
09/29/2018 at 15:00 • Filed to: wrenching, brakes
0
10|
"Urambo Tauro" (urambotauro)
09/29/2018 at 15:00 • Filed to: wrenching, brakes | 0
| 10 |
Because... weight savings?
Helped my brother out on a brake bleed gone wrong. Apparently when he went to turn the bleeder screw on this HHR, he suddenly discovered that it wouldn’t tighten anymore, and brake fluid was still dripping. Lo and behold, the threads had stripped.
He pulled the drum off and I saw a glint of blue underneath the brake dust. I wasn’t sure if I should be impressed to see anodized aluminum, or ask
what kind of boy racer bling is this
? I gotta admit, it does look pretty cool... for a drum brake part that isn’t even visible once it’s all together.
All the wheel cylinders I had seen up to this point had cast iron housings, and were hardly worth rebuilding, since you can get new ones for like $10 all day long at the local parts store. That wasn’t the case here. $30 for a freakin’ wheel cylinder. And even if this one was rebuildable, no rebuild kits were available. AutoZone’s was anodized blue too, so I guess this was a stock part after all.
We got back to the HHR and that’s when I noticed that the bleeder screw in the new one was crooked. Ruh roh Raggy
False alarm! It’s not cross-threaded after all. It’s actually supposed to have a slight angle. I put it back in with a dab of anti-seize and removed the old wheel cylinder to swap the new one in.
From then on, everything went smoothly. Even the old fare nut behaved, coming out of the old cylinder without a fuss and screwing right into the new one. I had to be careful about torque, though. The only spec I could find was 144 in-lb for the mounting bolts. I sure as hell didn’t want to strip the line or bleeder again.
In fact, the aluminum made me so nervous that I didn’t even bother touching the one on the other side of the car. I only ran enough fluid through this one to push the air out. Some old fluid was going to have to stay in the lines, at least for now.
So what do you make of these wheel cylinders, Oppo? Why would GM even bother with this sort of thing on this sort of car? Have aluminum prices come down that much? Is it about weight savings? Fuel economy? What’s this all about?
MM54
> Urambo Tauro
09/29/2018 at 15:50 |
|
I’m still unsure how it is that in this day and age
drum brakes are cheaper than discs, so having an aluminum wheel cylinder on top of that just baffles me.
brianbrannon
> MM54
09/29/2018 at 16:23 |
|
Way less metal in a drum system.
gogmorgo - rowing gears in a Grand Cherokee
> Urambo Tauro
09/29/2018 at 16:25 |
|
Aluminum cools more quickly than steel or cast iron. It’s also cheaper to cast as you can do the casting at a lower temperature, plus recycled aluminum simply is cheaper from a materials standpoint. You’re dealing with an economy car, which isn’t the same thing as an “economical car ”, it just means it’s cheap.
|
Urambo Tauro
> gogmorgo - rowing gears in a Grand Cherokee
09/29/2018 at 16:44 |
|
Oh I’m sure it’s cheap (it is GM after all). So bulk recycled aluminum is cheaper than cast iron? Wasn’t expecting that. The rest makes sense, though- lower temp casting, easier to machine, etc.
|
MM54
> brianbrannon
09/29/2018 at 18:20 |
|
But a lot more parts and labor to assemble
BaconSandwich is tasty.
> MM54
09/29/2018 at 18:49 |
|
The only thing I can think is that factories are already set up for tooling to make drum brakes. No factory changes needed.
That said, they are still terrible, and if I’m ever elected President/Prime Minister, I’ll ban them on all new passeng
er
vehicles.
|
gogmorgo - rowing gears in a Grand Cherokee
> Urambo Tauro
09/29/2018 at 19:41 |
|
L ooking at scrap prices (what the recyclers buy it for) semi- locally, scrap aluminum is $0.39/lb, mixed steel is $35/tonne, or roughly $ 0.0 16/lb. That’s a pretty significant difference, yes. But the added cost of recycling it is probably a ton higher than steel, given not only does it need heated about twice as high, it also needs a ton more refining to separate alloying elements. I can’t think of a means to compare new materials prices... onlinemetals.com doesn’t sell billet grey cast, haha. But a good quality cast iron frying pan goes for about the same price as a comparable size (and volume) forged aluminum pan at a local mass-market retailer, and the alumium pan requires significantly more processes (assembling handle, coating, etc) than simply casting it in one piece.
My Niva goes a step above and while it has cast iron wheel cylinders, the drums themselves are aluminum. Better cooling and corrosion resistance I guess...
merged-5876237249235911857-hrw8uc
> gogmorgo - rowing gears in a Grand Cherokee
09/29/2018 at 20:49 |
|
I believe old Lincoln Continentals had aluminum drums on all four corners too. Back in the mid ‘60s. Must have been some advantage to them.
|
gogmorgo - rowing gears in a Grand Cherokee
> merged-5876237249235911857-hrw8uc
09/29/2018 at 23:25 |
|
I was looking up friction coefficients, but there’s not much out there comparing the two as braking materials. Looks like it’s a toss-up, though, looking at Engineering Toolbox. Although the materials that have both Al and grey cast listed aren’t necessarily reflective of anything, what with them being Leather Fibre (advantage, CI), Straw fiber (advantage, Al), and “tarred fibre” (advantage Al).
I suspect it was mostly a cost factor. Steel was a more valuable commodity in the Soviet Union.
|
brianbrannon
> MM54
10/04/2018 at 01:34 |
|
People that assemble drum brakes in factories are way better at it than you