35 replies to this topic

[cbstdscott]

I recently discovered that Honda made a twin piston front caliper set that bolts right up to our cars, uses Integra and Accord pads and fits under 13" wheels. Twin piston calipers have a slight advantage over single piston calipers with more clamping power. 

 

In the 1985 model year, Honda introduced the B series engine in Japan in a special edition of the Accord. The "Accord 2.0 Si" was limited production model that was only sold in Japan from 1985-1987. Included on this model was a set of twin piston front calipers that fit under a 13" wheel. The NSX and Legend also came equipped with twin piston calipers but they are probably not the same size as the Accord calipers.

 

Maybe the only source for these calipers are the junkyards (they call them "breakers") of Australia and New Zealand. I contacted RPR member 3GCVC who has a business selling old Honda parts and he told me he had a "couple of sets" on hand. He is a great and reliable seller. I would highly recommend him for all your weird old Honda parts needs. He accepts Paypal and ships internationally.

 

The calipers arrived quickly. But I need to rebuild the calipers which requires a set of boots and seals. Through my research I discovered that the parts are sold by Centric Parts with a part number of 143.62005 for the Caliper Kit. These parts are also used on the 2000 Ford Mustang Cobra if you need a cross reference.

 

Scott

 

 

 

 

[Omega Mugen]

Nice discovery!  I am going to have to look out for those the next time I am overseas.

 

As an alternative, Fastbrakes sells a four-piston Wilwood kit.  They aren't going to fit under a 13 inch wheel though.  I think the only thing you need to make the six piston Wilwood caliper fit is a custom billet bracket.

 

The good thing about two pistons is the pad backing does not bow out as much when  the pads get excessively hot.  That means more contact of the pad with the disc and better braking.

[jsgprod]

Scott, there's more to getting more clamping power than what you are suggesting. While I'm sure those calipers were designed very well and probably will work, eventually. I'd suggest, if you haven't done it yet, to look into what size (bore) the master cylinder is that Honda used on that particular Accord first. Not only that but the motion ratio on the brake pedal will also have a lot to do with the amount of pressure that the master cyl. applies to those brake calipers.

 

All those things HAVE to work together to get the proper brake pressure and/or feel.

 

$0.02

Jay

[3rd gen sinner]

Its suggested to run a 1" bore MC from a 90 Prelude. It will require a 90 Civic booster and 87 Civic Sedan booster spacer to make everything fit. Check out my build thread for more info.

[cbstdscott]

I will start with the stock CRX MC and go from there. 

[Site]

i dont know how true this is but thres a guy here in the UK who used to build motorbikes then got into his hondas, now he loves his evos...but he said the thing to look out for is the actual area of the piston...he said theres no point having 8 piston callipers if they dont cumulitively cover a larger area than a large single piston....im not sure how true this is but kinda makes sense...but i would still prefer to see 2 pistons giving a more even spread over the pad

[cbstdscott]

I guarantee that the two pistons cover more area than one piston. 

[jsgprod]

I guarantee that the two pistons cover more area than one piston. 

 

That would depend on the size of the pistons now wouldn't it?

 

Check it out:

1ea, 2.1" bore piston (about what a stock Si caliper bore is) equals 3.463 in/sq.

2ea. 1.25" bore pistons equals 2.454 in/sq.

 

2ea. 1.5" bore pistons equals 3.534 in/sq.

 

 

Here's another interesting aspect of the braking system a lot of people don't get. Of the above three bore examples, with the same pressure applied at the brake pedal, which would give the most, and least, clamping pressure.

[Site]

 

That would depend on the size of the pistons now wouldn't it?

 

Check it out:

1ea, 2.1" bore piston (about what a stock Si caliper bore is) equals 3.463 in/sq.

2ea. 1.25" bore pistons equals 2.454 in/sq.

 

2ea. 1.5" bore pistons equals 3.534 in/sq.

 

 

Here's another interesting aspect of the braking system a lot of people don't get. Of the above three bore examples, with the same pressure applied at the brake pedal, which would give the most, and least, clamping pressure.

 

The greater force would be the 2 No. 1.25" bore pistons... Pressure = N/m² 

[Screech]

I would just prefer fixed calipers over floating. So a 4 piston fixed is Ideal to me. 

 

I was thinking the 2ea 1.5" bore would apply the most force for the given input pressure on same sized master cylinders, but I've never really studied that area of mechanics. My thought was when you push a fluid a create 5psi of pressure in it that the slave cylinder(s) with the larger surface area would have more of that 5psi reaches the moving part. Granted, it would also require more input to reach the 5psi. On the flip side I would think the 2ea 1.25" would have the least clamping force, but would require less movement of the input to reach 5psi in the fluid. Maybe my thoughts of translating of a classic fulcrum and level to fluids is where I get messed up.

 

On a side note, Honda likely used 1.5" pots on it do keep the "fluid dynamics" almost the same as the single piston units. The main advance of the duel (aside from the very slight increase in slave piston area, if I'm right) is that the area is not round [2.1"] but elongated [1.5x3.25" assuming only .25" sleeve between pots], much like the brake pads. So the heat/flexing of the pad is less likely. But, not sure those of us outside of road racers have to worry to that degree about the brakes to consider any warping and impact it has (or maybe doesn't).

[icebox187]

I like to get the three medium pizza deal over the 2 large pizza deal. The large deal is a dollar more and is less pizza. ☺

[cbstdscott]

The radius of the small pistons is 19 mm which works out to an area of 1,134 sq mm x 2 pistons = 2268 sq mm

The radius of one large piston is 24 mm which works out to an area of 1809 sq mm

 

Two small pistons > one large piston

[jsgprod]

Umm Scott...   

 

You're right, the two smaller pistons do have a larger area than the other single piston caliper. However, it's not necessarily about how much 'more' area you can apply to the back of the brake pad. While that does help in better distribution of that same pressure to the brake pad, it will do nothing to contribute to better stopping power without the proper pressure applied.

 

With the same pressure applied to the brake calipers, whether they be single piston, dual, quad, or whatever, the one with the smallest 'area' will apply the highest pressure, or clamping force, to the brake disc. The only way more brake caliper piston area will give you more, or equivalent to what you had prior, stopping power, is if you use a larger bore master cylinder.

 

Then you need to consider the brake pedal ratio.

And then there's the rear brake pressure that just changed due to the larger master cylinder. Etc, Etc...

 

All this info is easily available out there on the interwebs.

[cbstdscott]

 

 

You're right, the two smaller pistons do have a larger area than the other single piston caliper

 

 

That's all I was going for. So I think I was on point.

 

Thank you

[niccer]

Scott, you said in your first post "Twin piston calipers have a slight advantage over single piston calipers with more clamping power."

 

You said in your last post that you were only trying to achieve a larger piston area which obviously doesn't equal 'more clamping power'.  I don't know if you and jsgprod have an on-going feud, but he's clearly right.  Seems like this thread could (and probably still can) benefit future users with useful information on upgrading their brakes.  Let us know your impressions on the calipers with the stock MC and Booster.  I'll be looking to upgrade my calipers in the near future and would be interested on some feedback.