Has anyone ever weighed the difference between drum brakes and disk brakes from so a 91 crx si or a 90-93 acura integra. Compared to their stock brakes and trailing arms. This is for a 88std civic. I"m wondering if the weight penalty is worth it for a better brake feel and more balanced feeling as well.

Cory: Who is trying to get my hatch down to 1800lbs for SM hell. Any input would be appreciated, thanks.

 

The trailing arms are identical.

 

So if the trailing arms are identical then the only difference would be the caliber+rotor vs the entire drum.

 

caliper/rotor/pads/mounting brackets/shielding

backing plate/springs/clips/shoes/drum/wheel cylinder

The hubs look the same.

I just swapped a 91 crx si to civic dx

 

I'm aware of the other parts I"m just not sure if its totally worth it yet. Considering I"m kind of fishy on the amount of weight its going to add.

 

For autox, I wouldnt bother with the disc rear.

 

I've held both in my hands, and there was a noticable difference. I never thought to weigh them though. . .

If you're concerned about weight, and you don't mind servicing the drums, I would keep them.

 

The weight penalty of discs is substantial. I'm sure some of these CRX guys can help you out when they see the post.

 

Hopefully someone weighed them, but as it looks right now I think the drums will be staying on the car.

 

The weight penatly for the drum to disc swap that I heard quoted and repeated was 8 lbs heaviers on the discs. I can't recall if it was 8 lbs per corner or 8 lbs per pair.

I have done the swap and did not feel that it was worth the effort and expense. You can swap it in two ways: trailing arms and all or you can reuse your trailing arms and swap out the spindle and brake parts. I did the latter and it was a lot of extra work, heat, etc. getting the spindle bolts cleanly out of the back of the trailing arm. Swapping with the trailing arms and all will require less overall labor.

Once it was done and on the car, you will also need to change out the proportioning valve to the disc/disc valve as your braking will not be right with the old valve (I destroyed 2 brand new Hoosiers learning this lesson). Also the disc/disc car uses a larger bore Master Cylinder although this is not as critical as the prop valve. You can use your smaller MC but the pedal will be a touch longer. If you use the car on the street or use the E-brake to hold the car on a trailer, you will need to swap out the E-brake cables which I did not do but would suggest even though it is more labor yet.

When the car was finished, I can positively say that there was no additional stopping power after all of the work. The pads are so tiny compared to the larger swept area of the drum shoes that they just don't do much. On the otherhand, the discs require no maintenance like adjusting the brake shoes up which is a pretty I do for every race weekend or about once per year on the street as the self-adjusters don't really work very well or at least to the point that I like them.

My current street CRX (front Integra brake upgrade) and racecar (rules require normal CRX Si fronts) both have drums on the rear even though for many years I have had all the spare parts to do a rear disc brake conversion. That is not to say that I won't do the conversion at a later date if I decide that I want to push them to try for more braking capability but for now street and race I'm happy with the drums and will save myself the effort and cost of the conversion.

 

Lee I forget which master cylinder and which prportioning valve did you use? I thought I remembered it being a prelude on the MC but which year I don't know. Right. TIA.
Barry H.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by apexinghonda &raquo;</TD></TR><TR><TD CLASS="quote">Lee I forget which master cylinder and wh-ich prportioning valve did you use? I thought I remembered it being a prelude on the MC but which year I don't know. Right. TIA.
Barry H. </TD></TR></TABLE>

For the street car with the Integra front brake upgrade, I used the MC from the late '80s Prelude becasue it was the biggest bore in the exact same body that I had heard of. The bore and the cup volume are two sizes bigger than the normal CRX bore. If you are limited to keping a CRX sized MC by class rules, use the '90-91 disc/disc CRX Si MC size as it is one size larger than disc/drum '88-89 CRX Si MC. I am on vacation 700 miles from my cars so I can't look at the actual sizes.

As for prop valves, use the valve that goes with the disc/disc or disc/drum set-up you have. I didn't change the prop valve on my Integra disc front/Si drum rear car and it is fine for street and all the lapping and autocross I have done in four or five years. Just that disc rears required more fluid flow or pressure than the drums did so I had too much front, not enough rear when I did the swap without swapping the prop valve too. Too much front, not enough rear meant abnormal slowing and locking with huge flat spots in new Hoosiers.

 

Thanks for information, I"m probably going to keep my stock drums. Its probably 8lbs each side. I highly doubt its only 8lbs extra all together. But yeah thanks for the info fellows.

 

Also, will a larger master cylinder+proportioning valve from say a 90-93 integra improve my current brake pedal feel? I would think the master cylinder would have a greater effect, but i"m not sure.

 

Different platform but.... I did a rear disc conversion on my civic using the entire gsr rear trailing arm assemblies(with abs components removed) and the conversion was a snap... bolted up in just an hour or two. I used the MC and BB plus the prop valve(40/40) from an integra and noticed a big difference in braking.

The "pedal feel" or "travel" is greatly improved by the MC while the prop improves the balance as Lee stated giving more pressure to the rears then would the prop for a disc/drum setup. I did it all at once though so I can't say what the results would be with one and not the other.

I believe it would be maybe 8 lbs per corner... I honestly did not notice a difference with the bicep scale If you think about it, a drum and rotor are probably about the same weight so the only real weight difference imo would be the addition of calipers.... I'm curious to see if anyone has weighed the difference though.

 

doin the disk swap tommorrow or the next day, if i can find a scale ill weigh them...

 

Please do

 

The arguement of rear disks vs. rear drums comes up every so often on the CRX boards like the CRX Resource and Red Pepper Racing.

Long Story Short- You pay a weight penalty of 8 pounds each side for rear disks. Rear disks do not buy you any extra stopping power, with nearly 60% of the car's weight over the front wheels, the rear brakes can not contribute much stopping power.

The really trick set up for rear brakes on a Civic or CRX is to use the aluminum drums from a 84-87 CRX HF. These drums weigh 2 pounds less per wheel than the stock iron drums, they disapate heat nearly as well as disks, and they polish up real purdy.

The aluminum drums require no physical changes to your 1988 and newer Civic or CRX, they just slip right on (85-87 Civics and CRX need to change to the HF backing plate to make them work). The only down side is that aluminum drums cost about $80 each if you buy them new from Honda or Raybestos. But you can find them in the junkyard for about $5 each.

On my '87 CRX Si, I have 86-89 Integra front disks and calipers combined with the aluminum drums. I have no brake fade issues, even on track days at Willow Springs (in the Mohave Desert) in the summer.

Scott

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by cbstd &raquo;</TD></TR><TR><TD CLASS="quote">
The really trick set up for rear brakes on a Civic or CRX is to use the aluminum drums from a 84-87 CRX HF. </TD></TR></TABLE>

You know, I'd completely forgotten about the aluminum HF drums years ago. Can you confirm that they are a direct fit on an '88-89 CRX? I'll have to check the GCR to see if they would be allowed on the F Prod car as there may be a "ferrous material" clasue.

 

Will a larger master cylinder improve brake pedal feel on the stock brakes?

 

The aluminum drums do use an iron liner. It was a couple of years ago but I remember the stock drums weighing in at around 7.0 lbs each and the HF aluminum drums less than 4.0 lbs each. Drum brakes typically give more stopping power due to a servo effect from the shoes. (Thats why drum brake equiped cars will do e-brake turns so much better) The problem is that when lots of heat is generated, drums expand and move away from the shoes vs. disk brakes that expand and push into the pads.
If you're not road racing, get the HF drums and save a few pounds.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by goforbroke &raquo;</TD></TR><TR><TD CLASS="quote">Will a larger master cylinder improve brake pedal feel on the stock brakes?</TD></TR></TABLE>

The pedal should come a bit higher as it takes less cylinder stroke to move the same fluid but going too big might make it too quick and be grabby or harder to modulate when you need it. I wouldn't want to do that as a band-aid fix for another real problem.

Others with better understanding of fluid dynamics might be better chime in here as I think there is a risk of line pressure loss in doing this as well. My use of the larger MC bore was to fix a problem of a low pedal caused by swapping out from cylinders to calipers on the rear and bigger calipers on the front.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CRX Lee &raquo;</TD></TR><TR><TD CLASS="quote">Can you confirm that they are a direct fit on an '88-89 CRX?</TD></TR></TABLE>
Yup...they mount up and work just fine. With all the braking problems I encountered last year they were the only set of new, unused drums I had laying around and I had to give them a try.

 

Anyone else, even though you guys have covered pretty well already. I might try to find some Hf drums, it just might be worth it in the long run.

 

CRX Lee,

Your assumption is correct on the line pressure. The fluid mechanics of the larger piston in the MC are...A larger piston will require higher pedal effort to generate the same line pressure. The larger bore MC reduces the stroke because it moves a higher volume of fluid.

I did the 90-91 MC swap on my '88 and have a pedal that is a lot further from the floor now.