914 brake upgrade

donporfi · 10-03-2006, 01:22 PM

Can you tell me what upgrades can be done to the 914 regarding brakes?

I read some classifieds where they say they are using ATE calipers almost the same as the 911S calipers., which are bolt ons to the 914. Do you know what calipers are they talking about?
Also read that it is posible to use rear Carrera rotors and calipers. Is it possible to do this?
What have you used in the rears?

Thanks

Dave at Pelican Parts · Dave at Pelican Parts's Garage

The first upgrade is to get your stock brake system in perfect working order. Which isn't as easy as you might think--all of the parts of the system can contribute to poor pedal feel and some kind of braking problem. And bleeding every last bit of air out of the proportioning valve (or the master cylinder if you get air in there!) can be really tedious.

The next upgrade is tires. Brakes will only stop the wheel; the tires stop the car. Going with some nice wide modern rubber will give you shorter stopping distances than monster mondo rotors and calipers (and the huge wheels required to fit them).

There are BMW 320 brakes that bolt up to the front struts with little or no modification; see the Tech Article elsewhere on this site for details. The biggest benefit, IMHO, of going with these calipers is that you wind up with freshly-rebuilt calipers.

Other alternatives include bolting on a 911 front suspension and brakes, which gives you nice vented rotors for superior heat shedding ability. There are special hubs you can buy that let you use vented rotors (and I think 911 "M" calipers) under four-lug wheels, but these are not common at the moment.

In the rear, you can adapt 911 brakes to work. Adaptation is required, though. Some require brackets, others require careful shaving down of parts... Some require more than that.

Keeping the handbrake is, IMHO, a Very Good Idea, and is in fact required in many areas by law. Rigging up a handbrake when you change rear calipers can get very interesting (or difficult). There are threads on the subject here; search on user "wilco" for one approach.

Good luck!

--DD

djpateman · 10-04-2006, 05:27 AM

Most of what can be done depends on the intended use. If the car is strictly street use, then stock brakes are more than adequate if everything is new and fresh. On the other hand, if the car is for track use, then you need brake capable of slowing you from higher speeds more often. Race brakes generate more heat. As Dave says, vented rotors are great for shedding heat and that will be of great benefit to a track car. The added weight and inertia of vented brakes would make a street car slower. So it is a matter of balancing many factors.

The handbrake is considered an emergency brake for use when the hydraulic system fails, in addition to being a parking brake. Because of this the handbrake is considered mandatory almost everywhere.

donporfi · 10-04-2006, 10:23 AM

Thanks for your answers. I think my question was not complete or I did not mention what my intentions were.
I am gathering information on how to make a a conversion from 914-4 to a 914-6. One of my main concerns is brakes, for me the first upgrade before doing engine mods is brakes!
after that, suspension and last engine. If I put a large 6 cylinder engine I will need very good brakes. The car will be used mostly for DE, I do not want to have problems with brakes. My intention is to change all the brake system, master cylinder at least a 19mm, rigid and flexible lines, calipers and rotors. I would use 5 lug Fuchs wheels, larger tyres are in order also, what I am still not sure is if converting the body to GT fenders. I am still on the budgeting phase, therefore I want to get most of the info I can get.

trekkor · 10-04-2006, 07:55 PM

I have a stock 914-4 brake system in place on my 914-6 DE and a/x car. I use braided SS flex lines and Porterfield R-4 race brake pads all around. Motul fluid.

I even use the stock prop valve. The key is as Dave said, having it in perfect working order.

I bleed the brakes ( Speed bleeders ) regularly and I will tell you, I have no shortage of brakes. I can lock them at will. I run on 205/50/15's.

KT

jhadler · 10-05-2006, 11:23 AM

Agreeing with DD, the stock brakes are good for most applications. IF they're in good shape.

For DE use, the most important thing you need to do is get air to the brakes. If you can duct fresh cool air to the brakes, you'll find they can stand up to all sorts of punnishment.

If you go to really big wheels and tires, with a big six, then yes, I'd consider upgrading the brakes and proportioning valve... Go to vented rotors if you can. Bigger is not always better for brakes. Especially if the car is relatively light, monster 6-pot brembos are considered overkill.

Some early 911 brakes or even SC brakes would be a big improvement. Keep in mind though, that bigger brakes weight more, and depending on setup, can take more effort to work (foot pressure on the pedal).

-Josh2

trekkor · 10-05-2006, 02:23 PM

I just finished installing all new pads after removing the dust shields.
New front rotors are on, too.

Nice test drive...

KT

John Rogers · 10-05-2006, 04:44 PM

As already noted, the stock brakes are fine for street and auto-x use and maybe even a DE event or two a year. If you can not get a firm pedal then a tee in place of the prop valve, ss flex lines and a new master cylinder might help, although Dave is against the tee, most who have tried it, love it. If you do many DEs or Time Trials then you can consider the BMW calipers as the larger pad and fluid volume size will help slightly with heat dissapation but you are still stuck with the solid rotors. The next upgrade would be the alloy 4 bolt hubs (from here) and vented rotors with M calipers and they can really dissapate the heat as that is what I use on my vintage 2L car. My top speed is only 135 MPH and the hardest slow down I have is at the CA Speedway for turn 3 at about 40 MPH and they work great. Also on a short tight circuit such as in Mexico road races they dissapate heat good on short straights. If you go hog wild and run a monster 3.6L in a tube frame car with a top speed of 150 or so then Turbo or Big Reds are the answer but by then you will already know that.

donporfi · 10-06-2006, 01:23 PM

Thanks for all the answers. I am planning on using a 3.0 or 3.2 in this conversion.
I was thinking on using vented rotors in the front, but need rotors and calipers to match in the rear. Some people told me it is very difficult to modify the 914 rear brakes as there is no caliper/rotor combination that can be fitted there. I know the rear brakes do not work as hard as the front ones, but, at least I think these must match.
Please some recomendations for the rear.

jhadler · 10-06-2006, 01:51 PM

It's not that there is nothing else that works, it's just there is nothing else that's _easy_.

There are some killer setups for rear brakes out there, but they take time and money to make happen. Go to the 914Club site and search for rear brakes, I think you'll find some of the really snazy creations people have come up with...

-Josh2

djpateman · 10-10-2006, 01:05 PM

If you have 5 bolt suspension like the 914/6 has, then you have two options for the front. The M caliper struts (3" bolt spacing), and the S caliper struts 3.5" bolt spacing). The S struts can use A calipers, 930 calipers and a range of other calipers but you have to be sure to match the system up and expect some modifications. Rotors should be vented, and 20mm & 24mm thicknesses are common. You can get really fancy with floating rotors also.

For the rear, you can try to find 914/6 calipers or stick with 914/4 calipers and keep the stock emergency brake arrangement. The 914/6 gives you larger pads (and pistons) for better performance. Either can be widened for use with vented rotors to get rid of the heat much better. If you want to make different plans for the emergency brake, then any 3" bolt spacing caliper can be fitted, or with adapters almost any caliper.

Most important is to keep the majority of the braking in the front, and achieving a balance of performance from front to rear. I think the big thing is cooling. The 914/6 GT used (essentially) 911 S calipers in the front and widened (for vented rotors) 914/6 in the rear with up to 250 HP for endurance racing. More than that heads into the overkill category. My one friend with a GT tried bigger calipers on the front (not sure what exactly, but he had an IROC, 934, 935 and others to choose from), but found he did not like them and went back to the standard 908 calipers. He did use a 23mm master that was braced to the front cross-member.