60 replies to this topic

[firstgencrx]

So I'm working on my bigger brakes design, and I research stuff like I normally do. To Death!!! HAHAHAHA!!!

And I stumble across a very interesting bit of info. So will the real performance guys on this forum please explain something to me.... (this especially means kakabox, jsgprod, Greg Gauper, and the rest of you true race/engineer guys!)

Wilwood is a well known and respected aftermarket brake systems maker. I'm sure they have some of the smartest people on their staff. After all, they do business in a market that has a VERY high liability. BRAKES! So they don't want to get it wrong if you know what I mean....

Wilwood sells a really nice big brake kit for the 2G/4G civic part number: 140-8695 http://www.wilwood.com/PDF/ds491.pdf

A really nice kit! Well thought out and with nice large 11" rotors. Just small enough to fit under a 15" wheel! I'm think'n, I'll copy the kit so it fits the 1G, right? Then I discover this:

The effective caliper piston area is actually smaller than the stock 1G CRX caliper!

What? I was under the impression the larger caliper piston diameter, the better braking. The effective caliper piston area for the stock 1G is 2,042.821 square milimeters. The caliper Wilwood uses in their big brake kit is only 1,929.947 square milimeters.

So here are my questions (finally!):

Is the most effect on braking power due to the longer effective arm of the larger diameter rotor? Or, if I'm going to run with a larger diameter rotor, do I really need to use a caliper with a larger effective piston area?

I know people get great results from a Teg caliper and rotor swap. But the Teg rotor is only 9.53" in diameter (I want a bigger rotor, I know, it's a penis thing ). I can imagine more braking power from a larger piston area caliper combined with a smaller diameter rotor. It would be nice to save the weight an run the smaller stock caliper, if I can find a matching rotor thickness. No need then for the bigger master cylinder due to the increased system volume.

My goal is to stop better. I also like the look of the larger rotors. I'm also thinking about buying the Wilwood calipers for their cool looks!

That is all!

David

[flashmatrix]

Im no rocket scientist, but i believe a four piston caliper (wildwood kit) will have more braking force than an oem single piston unit.

[1985 CRX SI]

I would have to say one would need to take into consideration the diameter of the master calender piston in conjunction with the caliper piston diameter ( there is a ratio there ). It is not just about the caliper piston ( diameter/area ), ( rotor diameter/ swept area ).
Just my $.02
Jeff

[firstgencrx]

Im no rocket scientist, but i believe a four piston caliper (wildwood kit) will have more braking force than an oem single piston unit.

You bring up a good point, but the effective clamping force only comes from two pistons on one side.

I would have to say one would need to take into consideration the diameter of the master calender piston in conjunction with the caliper piston diameter ( there is a ratio there ). It is not just about the caliper piston ( diameter/area ), ( rotor diameter/ swept area ).
Just my $.02
Jeff

You are correct in it being a complete system that does the work. I was just more interested in what Wilwood was up to. I'm thinking it's the combination of rotor diameter and caliper piston area. Same clamping force, but longer arm for increased stopping power, or something like that.

David

[firstgencrx]

I see Wilwood makes a 10.5" diameter rotor that is 0.75" thick. That's not as large of a rotor as I wanted, but it would work with the 86-89 Teg caliper:

http://store.summitr...mp;autoview=sku

It would be easy for me to make some hats for the rotor.

David

[GENONE]

just wait till Anjin jumps onto this thread - Accord Calipers with 260mm rotors FTW! all under a 15 inch wheel and with parts from a wrecking yard....

[Airgazm86]

From looking at the .pdf it's hard to tell exactly what that kit is for since it says only HONDA CIVIC (4 LUG).

Could it be that the effective caliper piston area for other Civic's is less than that of a 1G? Maybe the 1,929.947 square milimeter area of the kit is larger than some cars.

[JDT]

I was under the impression that the main benefit of larger rotors was improved cooling. I guess it also allows you too use larger calipers aswell but is it nessecary on such a light street car?

It would be totally awesome to have 11 inch rotors though.

[RETROCRX]

OK here goes.

1. The kit is designed to work with a stock master cylinder...so It can't have a appreciably different piston area or your pedal travel will be different. Either higher or lower depending on the difference in piston area.

2. Smaller piston area than stock will give you a higher pedal and higher piston pressure at the caliper.

3. Larger rotors give you exactly what you are talking about, a longer lever doing the work of stopping the car.

So, you will have a higher pedal with higher clamp pressure with a longer lever working to stop the car coupled with the added bonus of more rotor to bleed the heat off.

It's a win win.

Anyway, one thing you need to be concerned with when making your brake kit. Either the caliper or the rotor has to float. The Wilwood kit has a floating rotor and a fixed caliper. If you decide to use a production car caliper ei) Integra, the caliper is floating (on the slider pins) so you would then use a fixed rotor. This is to ensure that both pads (either side of the rotor) are doing the same amount of clamping.

Anyway, that's the quick and dirty answer for you.

Make sense?

Cheers

Rob

[anjin]

Anjin jumping in.

When I was doing the comparisons between the various calipers I was quite surprised to find that the piston areas were very similar between the various calipers. They were mostly in the 48 to 49 mm diameter. Retrocrx's comment about the standard master cylinder only being able to deliver so much fluid is highly pertinent. Even the 94 prelude (not accord, but they are probably the same) calipers I am now running have a 48/49 mm diameter piston.

I also found the brake pad areas were similar too. Except that the 94 prelude ones are a bit bigger - as they are intended for a 282 mm diameter rotor I was not surprised - indeed it was a bit of a relief finally seeing a bigger pad.

But on reflection its not surprising. There would be optimum pad/rotor pressures engineered in which would tend to keep things similar. And the basic calipers, rotors and master cylinders are used over wider model ranges and for longer periods that you expect.

So an answer to the question is that the relative sizes don't really matter - the two important things are lever arm, and pressure on the pad. As pressure on the pad is effected by the driver, lever arm is IT!


After that comparison exercise showed that changing calipers would not improve piston areas that I went looking for the increase in lever arm, ie, bigger rotors. The combination of 262 mm rotor and '282 mm' caliper worked as a bolt on solution. I am still considering getting the fast brakes extender and going out to a 282mm rotor with the '282mm' caliper.
(The wilwood kit here would be well into the AUD $1500 range now, and I prefer my cheap oem $80 solution for now.)

With that FAst Brake extender you can put the standard teg caliper with a 262 mm rather than the 241 mm rotor, and still run 14 inch rims.
But not all 14 inch rims. You get clearance issues at both the centre and outside of the rim, but more around the centre.
If you are serious about weight this would be a good option.


One piston as opposed to two/four piston? I don't think its a direct pressure thing - it strikes me as trying to achieve a more even distribution of pressure to resist the deformation of the steel pad backing. I forget who posted it, but there are pictures on this site of seriously bent pads where the parts beyond the piston bowed away from the rotor. Under high loadings, the two/four piston set-up should give you more even pressures due to less pad distortion, so the slight reduction in piston area would be more than compensated for. Overall I see there would be good benefit in the two/four piston set-up.

And the comment about better heat capacity with the larger calipers would be right. Those 94 prelude calipers are massive even compared to the teg etc calipers. The standard calipers are simply tiny.

lastly - on unsprung weight. The tracks I frequent are smooth, so its not an issue for me. If it is an issue for you, stay with the 241 mm rotor and teg calipers with an extender.

[cbstdscott]

I also like the look of the larger rotors. I'm also thinking about buying the Wilwood calipers for their cool looks!

Are we discussing cosmetics or effectiveness? And what type of racing are we talking about?

Putting asthetics off to one side, lets discuss braking NEEDS vs. style. A daily driver, driven by a ration human without a death wish, the OEM brakes are prefectly adequate for DD usage.

Drag racing? As you only use your brakes once with lots of stoping room, you would want the lightest brakes (HF front and back).

Autocross? You would want a specialized pad that grips well when cold or cool.

Time Attack, Open Track or some other form of racing on a track with turns? Let your rule book be your guide.

Let's review how brakes work: they turn kinetic energy (movement) into heat. If they are good brakes, they will dispate that heat quickly so you can repeat the cycle. Pads create the heat, the rotors disapate it. A larger caliper/rotor combination will run the cycle more effectively than smaller pads and rotors... but at a cost in unsprung weight that becomes a factor in rotation as well as bounce/rebound.

The key word is compromise. You will want a large enough combination or pads and rotors to increase effectiveness without severly impacting acceleration or the ability of the tires to stay in contact with the road (one of the negative effects of higher unsprung weight is that the tires have a harder time staying in contact with the road surface).

Size does matter, and as I am happy to hear my wife say all the time, "Bigger is not always better."

I am the lone voice crying out in the wilderness here, but consider using brakes that will fit over a smaller wheel rather than a larger wheel. You will be faster with a smaller diameter wheel. My puny little EW-powered 13" wheels and tires were 10% faster than a B16-powered 2nd gen on 15" wheels this past weekend.

Finally, consider that that clamping down hard on the rotors is not enough to stop your car. Your will want a quality pad compound combined with a quality tire to be most effective in competitive driving.

Please send pictures of your brake bling!

Scott

[DEIVIONCRX]

Im going to agree with Retro on this one.

They are enginnering their kit to work with the stock system, while still giving you increased performance and feel. The longer lever arm of the rotors decreases the torque the rotor puts on the friction material.

Your calculations are just the overall piston footprint correct? What about the pads footprint, even thoe they scaled back the piston area, they are applying it more evenly with multipul pistons, and if the pad surface is larger its probably still has a larger friction surface even tho its not being applied the same on the backing plate.

[firstgencrx]

Thanks for all the replies so far!! Here is a long and complex reply to some of the responses so far. I put my replies in color to help make it clearer...

From looking at the .pdf it's hard to tell exactly what that kit is for since it says only HONDA CIVIC (4 LUG).

If you look up the part number in the Wilwood catalog, you will see it's for the 88-91 CIVIC with the 240mm rotor knuckle.

Could it be that the effective caliper piston area for other Civic's is less than that of a 1G? Maybe the 1,929.947 square millimeter area of the kit is larger than some cars.

I could be wrong, but from what I can find for Honda/Acura calipers, 1984 and newer, the 1G CRX has the smallest caliper piston area at 2,042.821 square millimeters. So no smaller ones I can find, so far.

I was under the impression that the main benefit of larger rotors was improved cooling. I guess it also allows you too use larger calipers as well but is it necessary on such a light street car?

I know the car is light and small, but I'm concerned about stopping. I live in a part of the country where, well..... there are roads around here where things are really flat and quite. The couple of times I opened up the little car close to 100 mph, I was scared to death when I put on the brakes! The brakes on these cars SUCK!!!!!!!!!!! Well, the ones on mine anyway.

People put a lot of energy into horsepower and handling improvements like cornering. But I rarely hear about brakes. A car that stops fast is super impressive. A fast stopping car can be almost as impressive as a car that accelerates fast. Example:

I helped a guy out a few years ago on his AC Cobra kit. He did most of the work on his own, and I helped him with some parts he wasn't comfortable making himself. The car was powered by an all aluminum 540 cu big block chevy, and had some huge ass brakes on it. He was of the same mind set as me that a lot of people don't really budget for brakes. We took the car out to the Pawnee grass lands for some testing one afternoon, and one of the things we wanted to see was how fast it would stop. Armed with an expensive GPS system and a stop watch, AND both of us in the car, we where able to accelerate from 0 to 100 mph and back to 0 in less than 11 seconds. That car could stop!

It would be totally awesome to have 11 inch rotors though.

I agree.

OK here goes.

1. The kit is designed to work with a stock master cylinder...so It can't have a appreciably different piston area or your pedal travel will be different. Either higher or lower depending on the difference in piston area.

2. Smaller piston area than stock will give you a higher pedal and higher piston pressure at the caliper.

This part I was confused with, so here is how I understand it: You get a higher pedal, but not higher piston pressure with a smaller piston. The ratio of the brake pedal arm and the diameter of the master cylinder will determine pressure behind the caliper piston. That same pressure can translate into higher clamping force with a larger caliper piston with greater working area. So if all things remain the same, just increasing the caliper piston area will increase the clamping force on the rotor at the expense of pedal hight.

3. Larger rotors give you exactly what you are talking about, a longer lever doing the work of stopping the car.

So, you will have a higher pedal with higher clamp pressure with a longer lever working to stop the car coupled with the added bonus of more rotor to bleed the heat off.

It's a win win.

Anyway, one thing you need to be concerned with when making your brake kit. Either the caliper or the rotor has to float. The Wilwood kit has a floating rotor and a fixed caliper. If you decide to use a production car caliper ei) Integra, the caliper is floating (on the slider pins) so you would then use a fixed rotor. This is to ensure that both pads (either side of the rotor) are doing the same amount of clamping.

I was under the impression the calipers that have pistons on both sides of the rotor could use a solidly mounted rotor. The idea is the pistons could find it's "center" of things and float as needed. Interesting. I'll need to look more into that.

Anyway, that's the quick and dirty answer for you.

Make sense?

Cheers

Rob

Anjin jumping in.

When I was doing the comparisons between the various calipers I was quite surprised to find that the piston areas were very similar between the various calipers. They were mostly in the 48 to 49 mm diameter. Retrocrx's comment about the standard master cylinder only being able to deliver so much fluid is highly pertinent. Even the 94 prelude (not accord, but they are probably the same) calipers I am now running have a 48/49 mm diameter piston.

1G/3G CIVIC/CRX caliper pistons: Front 51mm (2,042.8 square millimeters of area for the front)
1G Teg caliper pistons: Front 54mm Rear 30mm (2,290.2 suare millimeters of area for the front)
92-96 Prelude caliper pistons: Front 57mm Rear 33mm (2,551.7 square millimeters of area for the front)

One piston as opposed to two/four piston? I don't think its a direct pressure thing - it strikes me as trying to achieve a more even distribution of pressure to resist the deformation of the steel pad backing. I forget who posted it, but there are pictures on this site of seriously bent pads where the parts beyond the piston bowed away from the rotor. Under high loadings, the two/four piston set-up should give you more even pressures due to less pad distortion, so the slight reduction in piston area would be more than compensated for. Overall I see there would be good benefit in the two/four piston set-up.

You make an excellent point here for sure!

And the comment about better heat capacity with the larger calipers would be right. Those 94 prelude calipers are massive even compared to the teg etc calipers. The standard calipers are simply tiny.

lastly - on unsprung weight. The tracks I frequent are smooth, so its not an issue for me. If it is an issue for you, stay with the 241 mm rotor and teg calipers with an extender.

Just for info, I weighed the Prelude front caliper. It weighs 15 pounds! It's truly one giant piece of cast iron! Compare that to the 2.5 pounds the Wilwood caliper weighs. Just thinking out loud.

Im going to agree with Retro on this one.

They are enginnering their kit to work with the stock system, while still giving you increased performance and feel. The longer lever arm of the rotors decreases the torque the rotor puts on the friction material.

Your calculations are just the overall piston footprint correct? What about the pads footprint, even thoe they scaled back the piston area, they are applying it more evenly with multipul pistons, and if the pad surface is larger its probably still has a larger friction surface even tho its not being applied the same on the backing plate.

The Wilwood pad is actually smaller in area as well. But I think there is definitely something to the four piston arrangement giving the pad more even pressure to the rotor. I'm starting to think the Wilwood kit is working better from the longer arm of the larger diameter rotor.

[firstgencrx]

Are we discussing cosmetics or effectiveness? And what type of racing are we talking about?

Putting asthetics off to one side, lets discuss braking NEEDS vs. style. A daily driver, driven by a ration human without a death wish, the OEM brakes are prefectly adequate for DD usage.

Drag racing? As you only use your brakes once with lots of stoping room, you would want the lightest brakes (HF front and back).

Autocross? You would want a specialized pad that grips well when cold or cool.

Time Attack, Open Track or some other form of racing on a track with turns? Let your rule book be your guide.

Let's review how brakes work: they turn kinetic energy (movement) into heat. If they are good brakes, they will dispate that heat quickly so you can repeat the cycle. Pads create the heat, the rotors disapate it. A larger caliper/rotor combination will run the cycle more effectively than smaller pads and rotors... but at a cost in unsprung weight that becomes a factor in rotation as well as bounce/rebound.

The key word is compromise. You will want a large enough combination or pads and rotors to increase effectiveness without severly impacting acceleration or the ability of the tires to stay in contact with the road (one of the negative effects of higher unsprung weight is that the tires have a harder time staying in contact with the road surface).

Size does matter, and as I am happy to hear my wife say all the time, "Bigger is not always better."

I am the lone voice crying out in the wilderness here, but consider using brakes that will fit over a smaller wheel rather than a larger wheel. You will be faster with a smaller diameter wheel. My puny little EW-powered 13" wheels and tires were 10% faster than a B16-powered 2nd gen on 15" wheels this past weekend.

Finally, consider that that clamping down hard on the rotors is not enough to stop your car. Your will want a quality pad compound combined with a quality tire to be most effective in competitive driving.

Please send pictures of your brake bling!

Scott

Hi Scott!

Your replies are always so well thought out!

No racing. Just concerned about stopping from elevated speeds. Speeds you would consider irresponsible! I have my heart set on 15" wheels. Tire choice is the main reason. I have the option to make wider tires fit the car. The tire I'm shooting for is a 225/50-R15. I totally agree with you on tire quality playing just as important a roll in stopping performance.

I know what it's like to drive a car that will stop. Really stop. It's important to me. I am going to try and greatly increase the braking power of this car with as little unsprung weight gain as possible. I just need to think about it some more.

Your voice is not lone, you are an expert at taking what you have and making it as good as it can be. That's a dying art form for sure!. But I've already raped and molested this car enough to think outside the box.

Take care,

David

[alexm86]

David,

Wilwood makes a kit specifically for the 3G/1G. There is a guy who works at Willwood that has a 3G/1G. It may not be in the catalog anymore, but they will make it.

Marck from JEM Motorsports told me this in an email earlier this year:

"Willwood does offer a big brake kit upgrade!!!
I spoke with them at SEMA last year.
In fact, one of their techs has it on their 1st gen integra and had stated it fits 3rd gen civics & 1st gen crx too.
He also stated that he's big on SCCA and NASA."

Hope this helps.