[Ironring Racing]

Got a set of Brembo's for the front, and just now had the thought wondering if I could take the front brakes and put them on the rear? I'm seriously doubting, but since the stocks are just sitting there I started to wonder.

Part numbers are all obviously going to be different front vs rear, so I can't really look it up that way. Anyone know or heard of someone trying?

[enrita]

i seriously doubt it.

[nick 55]

What would you use as a parking brake?

Nick

[Ironring Racing]

I doubt it too, but hey, the only stupid questions are the ones unasked.

I thought I'd read the parking brake was a seperate small drum on the rear, but is it part of the rear disc brake caliper?

Don't know guy's, just wondering out loud?

[SoCalTech]

Parking brake is a drum in the rear, but the drum is built into the rotor hat. There is nothing in the front rotor to accommodate this.

[AP Racing - Chris_B]

Originally Posted by Ironring Racing

Got a set of Brembo's for the front, and just now had the thought wondering if I could take the front brakes and put them on the rear? I'm seriously doubting, but since the stocks are just sitting there I started to wonder.

Part numbers are all obviously going to be different front vs rear, so I can't really look it up that way. Anyone know or heard of someone trying?

In a word -- no.

Reasons:
1. Parking brake (already mentioned).
2. Way, way too much rearward shift in brake balance.
3. Master cylinder could not handle the increase in caliper piston size.
4. Mounting issues are likely very difficult and expensive to overcome.

Other than those reasons, it would probably work great!

[Ironring Racing]

Lol, thanks Chris, looks like it fell squarely in the "stupid question" category! ;-)

Thanks for all the help guys.

[AP Racing - Chris_B]

Originally Posted by Ironring Racing

Lol, thanks Chris, looks like it fell squarely in the "stupid question" category! ;-)

Not really a stupid question. What is stupid is bashing together a poor installation without research and crashing the car.

[I335]

Originally Posted by AP Racing - Chris_B

In a word -- no.

Reasons:
1. Parking brake (already mentioned).
2. Way, way too much rearward shift in brake balance.
3. Master cylinder could not handle the increase in caliper piston size.
4. Mounting issues are likely very difficult and expensive to overcome.

Other than those reasons, it would probably work great!

Chris - is #3 true? What happens when folks upgrade to a BBK, for example, and go from single piston calipers to multi-piston calipers? I don't think the master cylinder is changed for this type of application, is it? I would think that if #3 was the only problem, a little additional brake fluid may be needed.

Not challenging you - just hoping to learn a bit more from you. Thanks!

[Lowcruzr]

Originally Posted by I335

Chris - is #3 true? What happens when folks upgrade to a BBK, for example, and go from single piston calipers to multi-piston calipers? I don't think the master cylinder is changed for this type of application, is it? I would think that if #3 was the only problem, a little additional brake fluid may be needed.

Not challenging you - just hoping to learn a bit more from you. Thanks!

It completely depends on the displacement of the new caliper. If you maintain the same volume by using three smaller pistons equal to the size of on larger piston, it is possible that you haven't changed the demands on the master brake cylinder. Therefore it is safe to swap calipers. If you didn't do this math up front, you could have a caliper that has higher fluid demands on the master cylinder and could cause the brake pedal to hit the floor. Yikes!! Adding more fluid would NOT overcome this problem.

Many years back Stoptech brake was doing some development work at Watkins Glen on a Mustang Cobra. They were swappinng out calipers with different sized pistons, trying to find the combination that got the brake pedal feel just right.

[AP Racing - Chris_B]

Originally Posted by I335

Chris - is #3 true? What happens when folks upgrade to a BBK, for example, and go from single piston calipers to multi-piston calipers? I don't think the master cylinder is changed for this type of application, is it? I would think that if #3 was the only problem, a little additional brake fluid may be needed.

Not challenging you - just hoping to learn a bit more from you. Thanks!

Sure, no worries.

The front caliper already has much, much larger pistons than the rear -- sometimes twice the overall piston area. By replacing the front with a big brake upgrade, the front piston area may (or may not) go up a bit. However, if taking off the small piston rear caliper and replacing it with a larger piston area caliper from the front, now the master cylinder need to move much more fluid. It would now have the large front piston area plus much larger rear piston area. That is way too much change without changing master cylinder diameters -- the pedal would be very long and soft and the rear would have way too much bias.

When upgrading to a properly engineered big brake system, all these factors have been taken into account. Since replacing master cylinders is not something customers should be asked to do (nor is it particularly easy to find slightly larger master cylinders for most cars -- race cars are very easy!), the better kits are designed to not require a change. Remember, it is NOT the number of pistons that determine the correct master cylinder size, it is the total piston area (plus a few other factors such as flex, etc.).

[ah gon]

what about from 325i front brake to 335i front brake? i did the swap from 325i to 335i brake.should i adjust or add brake fluid to master brake cylinder?

[AP Racing - Chris_B]

Originally Posted by ah gon

what about from 325i front brake to 335i front brake? i did the swap from 325i to 335i brake.should i adjust or add brake fluid to master brake cylinder?

Both the 325i and 335i front calipers have the same piston area, so no master cylinder change is needed. In fact, the OE master cylinders are the same (22mm F / 25mm R) for both models. You now have a car with slightly more front bias than is ideal. It would be best to do the rears as well, so you will have to research whether the parts will swap or not.

[ah gon]

Originally Posted by AP Racing - Chris_B

Both the 325i and 335i front calipers have the same piston area, so no master cylinder change is needed. In fact, the OE master cylinders are the same (22mm F / 25mm R) for both models. You now have a car with slightly more front bias than is ideal. It would be best to do the rears as well, so you will have to research whether the parts will swap or not.

thanks for fast reply! yeah i did have little front bias,but still fine for me.also,i need to replace the 335i's parking brake system to fit the 335i rear rotor or i can fit without e-brake. i bought these used set(front and rear) for cheap.but one side of parking brake need $400+ at tisher.so $800+ for both side,much more than i bought these whole set.i think i'll waiting for local auto wrecker to buy used set.

[BKTL]

WOW! You know that phrase, "There's no question that is a stupid question?" Well, my answer to that is you just proved it wrong.