i have this posted in drag racing but i got no responce. Its a 2000 civ si and im seaching for a big brake upgrade now the problem is example:hp racing makes a 6 piston 11.5"rotor but stop-tech has a 4 piston 328mm rotor. what is better?

 

I'd go for the bigger rotor, more heat dissipation.

 

A larger rotor will increase brake torque (leverage), as well as have more thermal storage and surface area for heat dissipation.

The number of pistons doesn't necissarily mean you get more clamping force. It just means it spreads out the clamping force more.

Clamping force in terms of the caliper pistons, is the total piston area. It is possible to have 4 larger pistons with the same or more total area than 6 small pistons.

 

What is the application for these brakes?

If you can lock up your tires, then you have all the clamping force you need. More is not beneficial. If you don't experience brake fade, more heat dissipation won't help you either.

Cheers,
Roy

 

also make sure that if you get largers rotors that they atleast weigh the same as your stock ones if not less

 

thanks for the info, is for a 2000 civic si turbo-343hp street/strip car

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 7thGear &raquo;</TD></TR><TR><TD CLASS="quote">also make sure that if you get largers rotors that they atleast weigh the same as your stock ones if not less </TD></TR></TABLE>

ugh.. why?

Unless he is getting a two peice rotor (which I doubt he is). He would gain no mass or lose mass by following your advice.

 

if your putting a bigger rotor on that weighs more than the original, you now have that much more rotating mass to stop, and if its significant enough you might actualy get worse performance than before!!

every pound counts when you have a little torqueless 1.6 liter powering your car.

 

A larger rotor is going to increase brake torque much more than the 1lb or 2 that a larger rotor would decrease from braking ability.

Its not like you are adding 20lbs to your rotor

Simple brakes, more mass means more thermal storage. Brakes turn kenetic energy into heat. What happens when you can no longer store heat that is being created?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 7thGear &raquo;</TD></TR><TR><TD CLASS="quote">if your putting a bigger rotor on that weighs more than the original, you now have that much more rotating mass to stop, and if its significant enough you might actualy get worse performance than before!!
</TD></TR></TABLE>

Fellas, it's not just the weight of the rotors.

I read everyone on this board saying the same thing, and the term is "moment of inertia" - not rotating mass. You can have a higher rotating mass but at the same time a lower moment of inertia.

Cheers,
Roy

 

i'm not following

teach

 

How much did you pay for a lighter flywheel? Larger diameter and heavier brake rotors are just heavier flywheels to accelerate. A two piece rotor with an aluminum center section and iron rotor section will be lighter than all iron in the same diameter, but it still has the heavy section furthest out from the center for more flywheel effect.

As far as heat versus mass, yes the greater mass makes a better heat sink, but more surface area allows faster heat dissipation.

For drag race you want the smallest diameter that gives enough braking power to prevent fade for one stop from speed with significant time before the next stop. A pad upgrade may be enough. Maybe a Fastbrakes ITR upgrade with the 2-piece 11" rotors.

 

Yes surface area radiates heat, but mass is equally important. Radiating heat is going to help you if your rotors are heatsoaked and you can no longer stop.

Yes you can refer to the weight distribution of rotors and brakes in terms of moment of inertia, but its still rotational mass. The difference is referencing where the weight is distributed or not

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by StyleTEG &raquo;</TD></TR><TR><TD CLASS="quote">
Yes you can refer to the weight distribution of rotors and brakes in terms of moment of inertia, but its still rotational mass. The difference is referencing where the weight is distributed or not </TD></TR></TABLE>

Rotating mass describes a property (mass, obviously) and moment of inertia describes a force. From a cars engine standpoint spinning a weight the 2 are identical. I was being picky, but yeah, where the weight is matters the most.

I wanted to prevent people from thinking that because a rotor/wheel/flywheel is lighter is must automatically have less rotating mass (it may) or moment of inertia (it may not).

Example:
Rotor 'A' weighs 5 pounds and has it's mass around the outer edge.

Rotor 'B' weighs 7 pounds with it's mass around the center.

Rotor 'A' has less rotating mass, but a higher moment of inertia. The problem is as consumers we never have the data needed to discern between the 2 so it's really a moot point.

Cheers,
Roy

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mohudsolo &raquo;</TD></TR><TR><TD CLASS="quote">How much did you pay for a lighter flywheel? Larger diameter and heavier brake rotors are just heavier flywheels to accelerate.</TD></TR></TABLE>

Incorrect, the flywheel follows the rotation of the motor, the brake rotors follow the rotation of the wheels. The mass of the flywheels will be more critical to the performance of the vehicle due to the fact that the rotors come after the transmission and their inertial load is reduced by gearing. So therefore, four pounds off of the flywheel will more than make up for four pounds added to the brakes.

 

I didn't mean to imply that there was a 1 to 1 relationship between the flywheel weight and brake rotor weight, just that the rotors can act as a heavier flywheel. I've seen some very heavy rotors in big brake setups. On mk iv vw's, the Audi TT front brakes are a popular upgrade. The Audi rotor is 17 1/2 lbs each and yet most don't even give that weight any thought.

I forgot to mention before that the bigger brakes require bigger wheels that can add weight and effect gearing. The bigger wheels can limit tire choice. Most fwd drag cars I see run fairly small diameter wheels so make sure about what tires you want to run before commiting to a brake setup.

 

you will also feel a decreas in power from a larger heavier rotor.....again as stated where the weight is placed is more critical than any thing .....

good point was made about using smaller diameter wheels ...if you drag a lot and are looking for the best time dont go to large...an ITR setup would work great with some good pads...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mohudsolo &raquo;</TD></TR><TR><TD CLASS="quote">I forgot to mention before that the bigger brakes require bigger wheels that can add weight and effect gearing. The bigger wheels can limit tire choice. Most fwd drag cars I see run fairly small diameter wheels so make sure about what tires you want to run before commiting to a brake setup.</TD></TR></TABLE>

This is very true.

 

I guess we need to ask what speed does the car need to brake from? My GSR at 2600lbs plus me and the occasional passenger can brake from 120+ on the straight at Watkins Glen down to 80something with the stock brakes with the backing plates removed and poor ducts with Carbotec pads and no fade problems. Except for dust the pads are OK on the street too. The pads are expensive and the rotors will only last a few track days before they warp, but they are only $50 for a pair.

The Integra/Civic EX brakes will, barely, fit inside some 13" wheels. The ITR brakes need a 15" wheel minimum. I absolutely agree that the best brakes you can get are your friend when stopping time comes around, but you need to look at the full picture and decide from there.

 

But when it comes to which brand of brakes, Stoptech seems to be at the head of the pack.

If you want to go to something effective and inexpensive, then get the ITR 5 lug conversion with the associated brakes, bling AND stop in one convenient package.

 

thanks for all the imput guys, i just ordered a set of stoptech 4 pistons... Merry Chistmas everyone

 

Remember about unsprung mass being effected too.