Car caliper on bike. Is it possible?

[Sidecar Bob]

I'm in the shop right now cleaning up the caliper on Eccles (CX650E based winter machine). I have to do this at least once every year because the pistons get gunked up and it starts to drag. This is a Honda 2x 30mm piston caliper similar to the ones on the GL1100 and GL1200 (I believe this one came from a GL500).

Every time I have to do this I think there must be a better caliper for winter use but I usually leave working on the brake until I'm about to start driving it again and I'm in too much of a hurry to do anything about it.
This year I'm going to at least start asking questions before it's the last minute.

The big questions are: 1) what is the smallest car caliper?, 2) how small is it? and 3) how hard would it be to adapt it to fit the bike?

[Rat]

Maybe something off of a modern bike, say the 1800, might be an easier adaptation ?

Gord

[joecoolsuncle]

since its for winter use, and heat is not an issue, i would overhaul the one you have and build an aluminum shield for it. whole lot easier than modding a caliper that may kill you.

[Rednaxs60]

Interesting question. Anything is possible. A drawing with dimensions of the caliber to be replaced and a trip to an auto wreckers for a walk about maybe. I would think the issue will be with the mounting arrangement. Car calibers have a lot more room to play with. Good luck

[Sidecar Bob]

Yeah, that's why I'm looking for the smallest car caliper I can get. Maybe from a Smart or something like that?

One of the things that got me thinking about car calipers is that the standard ones usually aren't aluminum. I understand about lower unsprung weight and handling but I also understand about aluminum, stainless steel and salty water leading to galvanic corrosion. I started along this path by thinking that I probably should replace the pistons in the existing caliper because they have a few pits but the replacements sold these days are usually stainless and I have already had to replace calipers because of the aluminum corroding away enough that the first rubber ring started to squeeze out. (NOTE that this is not an issue on the GoldWing that I don't use in winter)
That said, I'm not ruling out using an aluminum bodied single piston caliper with a boot. They can have similar issues but when I last had one on a winter bike I learned that injecting half a cc of brake fluid behind the boot helped keep the corrosion down so coating the area with silicone (like I now do with the 2 piston caliper) would probably protect it just as well.

I've also thought about car discs being wider and I have a couple of ideas:
I have the wheels & discs from the GL1100A that I got Mr.H's engine from. I haven't investigated whether one of those discs would fit Eccles' wheel yet or whether it might be better to use the Aspencade wheel or even whether there is enough room.
When I built the trike I bolted an automotive disc to the chain drive ATV differential and used a caliper from a different car. The caliper was too wide for the disc but I used an old brake pad as a shim and it worked fine (I didn't take notes or pics 25 years ago like I do today so I don't have any more details than that).

[Earl43P]

Maybe something off of a modern bike, say the 1800, might be an easier adaptation ?
Gord

Nope, GL1800 has front and rear linked brakes, so its calipers have two banjo fittings. No bueno.
Finding boots to cover the exposed pistons would likely help keep down the crud accumulation.

[5speed]

what about stripping the bike caliper and getting it powder coated including the inside where the piston goes.

[Sidecar Bob]

I'd have to either get slightly smaller pistons or increase the bore slightly and I'm not even sure powder coat would hold up inside the bore.
And that wouldn't help with the crust of salt & dirt on the outside of the pistons anyway.

The more I think about it the more I want something with boot(s) on the piston(s).

At the moment I'm considering one of these (cast iron body, pads not included)
https://www.amazon.ca/Premium-Caliper-C ... K918M?th=1
If I go with something like this it will stick out quite a bit more and clearance to the wheel might be an issue. At least I can send it back if I can't use it.

Or a pair of these (probably aluminum body but new and has piston boots, pads included)
https://www.ebay.ca/itm/252884415487
Looks like fabricating brackets shouldn't be too hard.
I've been contemplating how much braking force these can provide:
- Two 2 piston calipers are to much (especially with the CX650E's 280mm discs) for a sidecar outfit on snow & ice but one is just about right.
- The TRX has 2 discs & 2 drums to stop a machine + rider about 2/3 of the weight of Eccles.
BUT the (190mm?) TRX discs are about 2/3 the diameter of the E disc so (fade aside) one TRX caliper should have considerably more power on the 650E disc than on a TRX disc but almost certainly less than a 2 piston caliper.
- Would a pair of TRX calipers on slightly smaller discs provide about the same braking as one 2 piston caliper on the 650E disc?
- ALSO, how wide the swept area of the disc does the TRX caliper need and is the swept width of the E disc wide enough? Di I have a pair of discs that would be suitable that I could adapt to my wheel (or another wheel I have on hand)?
- Am I overthinking this?

[Sidecar Bob]

I've been in touch with one of the local hotrod guys and he's going to ask around and see if anyone has a suggestion for a car caliper.
And I joined a couple of Honda ATV forums to ask for info about the TRX brakes but no replies so far. I also found the calipers at the Labwork website and asked there about the maximum disc thickness.
I do have a GL500I front wheel with two 240mm discs.

[Sidecar Bob]

No reply from the ATV forums and no word from the hotrod guy.
I did speak to a friendly auto parts guy yesterday when I bought the new inline fuse holder for Mr.H. He said to look for a rear caliper from a small Honda or something else that is very common but he also agreed that the ATV calipers sounded like the best option.

I found a pair of the TRX500 calipers on Amazon for about the same price as the ones on eBay (with 30 day return policy) so I ordered them and we'll see if they can be made to work.

This morning I wondered if I could find the FSM for the TRX500 online and if the information I've been looking for might be in it. Turns out the 2012 TRX500 FSM has very complete specs
Disc thickness: 3.8-4.2mm (limit 3.0mm). The GL500 discs I have are approx. 4.5mm thick so there is a very good chance the TRX calipers will fit over them (& last a good while before reaching the 3mm wear limit).
Piston diameter 32mm. The current caliper has two 30mm pistons so two 32mm pistons should be in the same ballpark for braking force.

[Shadowjack]

Rear brakes from a front-drive car will have the e-brake mechanism in them.

[Sidecar Bob]

From what I've been able to find out the emergency brakes on cars with rear discs are usually small drums that have no connection to the calipers.

[robin1731]

From what I've been able to find out the emergency brakes on cars with rear discs are usually small drums that have no connection to the calipers.

Usually a small drum inside/part of the rotor.

[Sidecar Bob]

Yep. And since I'm planning to use a bike disc or discs that wouldn't matter.

[Shadowjack]

On the Honda cars I've had the e-brake is a lever mechanism that rotates the piston in a thread to jack it out as you pull the e-brake. No idea how much of that would be discardable.