Upgrading 308 brakes

William
I am in the process of adding 355 rotors and calipers to the front of my carb'd GTB. Commensurate with this change, the master cylinder went south, so the brake "project" expanded in scope. In sum, the change has had three components. First, the rotors/calipers and mounting hardware on the hubs; second, the MC/hydraulic ratio and, third, the mechanical ratio (depending on whether you keep the stock booster/pedal box mechanical ratio). Hopefully, some of this is relevant to your enquiry.

Sounds like you have some of the hardware, but in my case, bells were made up by QV London, I am getting the mounting brackets made up by a local machine shop, and we'll make up the lines etc. For those interested, QV is making a "kit" including bells, rotors, calipers and mounting hardware, but contact QV directly about timing, cost and availability. The change mounts the wheels about 4mm further outboard. My wheel bolts are fine, but as they are non-stock (I run BBS wheels), anyone running OEM wheels should check lengths. Finally, and a bit off topic for you, they do require 16 inch rims.

Second, we've just been through a MC change on my car (and I'll post a report w/pic when done, hopefully in the next 7 days), but in a nutshell, we removed stock booster and MC, and put in two MCs w/balance bar, sizing the MCs to the 355 F caliper pistons (2x 36mm, 2x 40mm). Right now I am using 3/4 (F) MC and 7/8 (R) MC with a 2lb residual valve in the front line (to cut down pedal travel), but our guess is the rear MC is too big given the small rear caliper pistons of the stock 308 (38mm) [and 3/4 inch MC on the rear would have been a better choice]. So we'll either look at upgrading the rears or a smaller MC depending on how it feels at the track. Related to this, I don't know the size of the F40 pistons, but given you'll likely be increasing capacity significantly, (the F 308 pistons being 48mm bore), the stock 308 MC is likely to be too small for the brakes and may require excessive pedal travel to get the stopping potential you desire.

Last, we changed the pedal box as we removed the booster. The stock (boosted) mechanical ratio is around 2.8:1 (comprised of 4:1 through the pedal and about 0.7:1 through the bell crank). We altered the pedal box to make this ratio 6:1, the ratio recommended by Tilton/Wilwood et al as a good starting point for a non-boosted application. To do this, we changed the bell crank to 1:1 and relocated the tie rod connection lower on the "ear" or extension, of the brake pedal. The bell crank change also meant moving the brake pedal closer to the clutch, so we had to reconfigure the spacers on the pivot bar and then build up the throttle pedal to enable correct heal and toe alignment.

As I said, it has been a project. I'll post pics once done.
HTH,
Philip

 

Wiliam H,

I started a Big Brake thread , but have yetto post my early findings, so here goes:

What are the specs for the 512TR brakes?? Rotor diameter, thickness and caliper specs: # of pistons and diameter of pistons. What size of wheel is needed to clear the brakes??

Stock 308 #s are 271 diameter, 22 mm thickness caliper pistons (2) 48 mm.
Stock wheel is 14 inch.

Brembo makes a kit with 313 diam rotor w/ 28mm thick with 4 pistons of (?) diameter and uses a 16 inch wheel. Price $2595

Movit uses a 322 rotor 32 mm thick, 4 pistons with (??) size pistons for 2550 Euros. I believe they recommended a17 inch wheels.

Wildwood will build anything you want.

Stoptek has nothing for the 308.

QV London has developed a kit for the 308 that uses 355 brake calipers with adaptors and I think 355 rotors. I asked them for the rotor diameter, thickness, piston size and for a wheel dia recommendation but have yet to hear from them. They quoted me a price of 795 pounds for the kit.
I believe that PMA is instaling this kit.

hth,
chris

 

HOLY SMOKES! That's proving to be a Doozy of a project!
I'm interested though in that kit QV would be putting together, I was planning to follow this route, too. If they price it right, I'm there! I'll have to contact them!
oh, well while I was typing Chris was posting price info!

 

Phillip,

Could you have the machine shop make two sets of caliper adaptors??

So far, this is the hands down winner in front brake modification.

I am particularly interested in you brake balance results.

With great enthusiasm,
chris

 

Chris
I can, but it'll be cheaper to wait for the complete kit from QV.
LMK, Philip

 

Here's part of the story.

First pic shows 355 rotor with QV London bell. Bells adds 4.5 mm to width and required bolt length.

2nd shows custom mounting bracket. We shaved the "ears" of the caliper beyond the bolt circle for clearance. [QV is developing a kit which locates caliper on a different part of the rotor arc, avoids need to shave caliper and hub mounting ears]. In the background you can see the comparative rotor dimensions.

Will post details of pedal box and MC mods and (hopefully) field test report from Road America this weekend.
Philip

 

I look after a 308 that was previously modified. It uses F40 discs on one off hats and F40 Pads in an old AP racing caliper. It also has an AP 3 position bias valve which seems to work nicely. It uses stock std m/cyl and stock std rear brakes. It has compomotive 16" rims.

It runs on sticky tyres at numerous track days and is awesome on the brakes. It stops no better than any 308 on sticky tyres will for one lap, but it does it for lap after lap after lap after lap........

 

Hi guys,
I’ll throw in my 2 cents. I designed the 308 front kit at Brembo a couple years back. So I have been round and round with this system before.

William, the F40 calipers have 38-42mm pistons, and have a great deal more piston volume than the OE 308 units. This will make for a long travel and soft pedal unless you upsize the OE MC.
The same goes for the 355 caliper kit, which uses 36-40mm pistons all around. This makes for a large increase in total car piston volume, and again will leave a long pedal.

The front Brembo kit was a bit more of a compromise than I would have liked, and uses a caliper with 36-40mm pistons. The pedal feel on this kit is a bit softer than OE, as the MC and booster are left stock. My hands were tied in regards to developing a rear kit or a new caliper for the front. The vehicle balance is also less than perfect this way. It is not dangerous, but could be better.

But now I am designing a kit for Girodisc, and it should be in prototype this month. This time I can develop the system to be balanced and also give customers some bonus features.
I will be using 4 piston calipers all around, I don’t want to say the manufacturer just yet, but they are from a well established racing caliper manufacturer.
• The system will be released initially in “race” form, which means that there will be a 4 piston caliper on the rear, and no parking brake.
• If demand warrants, we will develop a parking brake assembly for a second rear option.
• There will be a front only version available which uses a small rotor, and will fit the 15” wheel.
• The real bonus is that I am developing the rotor bells to be used with the standard Ferrari 5 on 108mm bolt pattern, as well as having an adapter available to provide wheel studs in a 5 on 114mm bolt pattern. This adapter will not change the brake hat dimensionally from stock at all.
• This 114 bolt pattern will allow 308 owners to take advantage of the larger (and less expensive!) numbers of forged and lightweight alloy wheels available in the market. Traditional Ferrari upgrade wheels are very expensive and limited in sizing. Anybody who wants track wheels for their Ferrari would do well with this option.
• The bells will be floating race type. Bells are anodized, brake lines are stainless braided, rotors are zinc plated, brackets will be anodized or cad plated, all hardware will be included and the system will be a bolt on and use the OE MC and booster.
• The price? We intend to release the 4 wheel system for $5000 or less, and hopefully less. We want to build a viable solution at the right price.

I am including pictures of a front and rear system we did recently, and the 308 will look similar. Though final coloring and aesthetics are TBD.

Stay tuned! And don’t hesitate to put in your thoughts on any aspects of the system.
-Eric

 

The pedal on my F40 braked 308 (std M/cyl) is as good or better than a std car. the extra caliper volume seems to have made no difference to the travel at all. It has stainless braided hoses which reduce travel a little though.

In your recent photo's...it looks to me like the calipers/pads don't reach very far into the disc towards the centre. I know the outer edge does the most work, but it just "looks" like wasted stopping power/cooling. It's as if the caliper is meant for a smaller diameter disc.

Just a comment. Still got to be better than a std set up.

 

I have a couple questions for anyone who might know.

First, is about larger pistons. Clearly the disadvantage is they really require a mastercylinder change, but is there an advantage to using the larger pistons that might make it worth the bother?

Is there a significant weight savings or pedal control improvement to pulling out the power brakes?

Last, I’m still a little confused about why a brembo or stoptech four piston at $800 or $500 is better than a wilwood 6 piston at $300 or wilwood or outlaw 4 piston at $250? Stiffness? Pad choices? Pad size? Is it a difference that would only be seen on a track? It is way temping to spend ½ or 1/3 on calipers but I don’t want to be disappointed.

 

I hope that was a typo and you meant 16" wheel. We don't want bigger rotors, not smaller rotors. Of course older 308's used 14" wheels, but the newer ones, and anyone serious enough to upgrade their brakes, use 16" wheels.

I'd still like to be high on your list to help prototype and test these!

 

One more question/thought on the parking brake. It would be pretty easy to put a second “mastercylinder” to put in-line with the rear brakes and attach it to the parking brake handle to operate the rear brakes using the parking brake handle. It would not be an emergency brake because it shares the hydraulic system, but would function well as a parking brake and get the car through inspection. Any thoughts?

 

"This 114 bolt pattern will allow 308 owners to take advantage of the larger (and less expensive!) numbers of forged and lightweight alloy wheels available in the market. Traditional Ferrari upgrade wheels are very expensive and limited in sizing"


I think it should also be noted that these wheels you speak of do not come in a +11.5mm offset which the 308 uses.
And that will put you right back in the custom pricing boat, or force one to use spacers to make-up the difference.

 

I am NO expert on this. Here's what I learned and have done. All input welcome.

First, for me, the brake upgrade has been a long time in the coming. I bent the backing plates to the front pads at Road America in the Spring. Braking from the 3 1/4 point typically into 1, a bit earlier into 5, 12 for those of you who know the circuit. Despite the 5 point harness, I was trying to "straight leg" the brakes to get enough torque on the pedal to get the **** car slowed down enough. Ate Super Blue fluid, Carbotech 1109XP pads F, 1108 rears, big ducts etc. Also, the inside rear would tend to lock into 12 unless you were careful, indicating a bias issue.

Second, QV London (who prep some of the Ferrari Classic series cars and have won the PFMC 4 or 5 times) indicated they had a bolt on kit for the 308 using used 355 parts for 795 pounds or about $1400 and that once on, "you could forget about the brakes". This system uses 4 piston calipers 36mm/40mm pistons versus the 2, 48mm pistons of the stock. Initially discussed back in May, I received most of the parts two weeks ago. The delay being caused by an understandable desire on their part to have a bolt on kit, with no machining to the existing hardware.

Third, in parallel with the above, my MC went. I could not find an OEM master/booster (they are NLA) and would not buy used. In addition, never happy with the booster -- my car makes 2 to 3 inches of vacuum at idle and I believe it gave me an inconsistent pedal -- I elected to put a dual MC solution on the car. There's another write up to which I need to add some pics on this topic elsewhere, but the "cliff notes" version is the change is not trivial, given the required changes in mechanical leverage to get this close to 6:1 (stock is 2.8:1) and requires a lot of cutting, welding and custom fab. I bought a CNC dual master with balance bar assembly that fits in place of the stock MC/booster. It has cockpit adjustable brake bias etc. The stock proportioning valve has been removed. I elected to use 3/4 inch F MC with a 2lb residual valve and 7/8 inch rear. The rear MC is too big for the stock 308 calipers (3/4-inch would have been a better choice) and I have an upgrade planned (to 4-pot) for the rears over the winter so will leave "as is" for the moment.

As a reference, today I have about an inch to an inch and a quarter of pedal movement until I am "full on". As you know, the MC choice is a compromise between travel/feel vs a short binary "on-off", most people wanting a short, high pedal with enough movement to modulate the brakes. From memory, the stock 308 MC is 0.9 inches bore (the spec is in the WSM). A slightly larger bore (an inch?) may solve the issue of larger fluid volumes with more/bigger pistons (Brembo or 348/355 calipers), but of course there is the bolt pattern on the booster and the push rods lengths and clearance to deal with if you need an adaptor plate...

Mark:
- a hydraulic "emergency" brake (known in England as a hand brake) would work, but I suspect are not legal for road use...
- On the pedal travel issue, you've got my thoughts and experience above. I know you recognize that stock cams (more vacuum) may change the equation
- the stock 308 rotors are unbelievably heavy. The stock 355 rotors are too. Arguably they'd work quite well on a truck. There is a significant weight saving to going to custom hats with (floating) discs. I think Eric has posted weight data in the past confirming this. Supporting this, the 348/355 calipers are a lot lighter than the 308 calipers. Moving from OEM to custom/aftermarket rotors, hats and calipers, a friend saved 25lbs per corner. All this is unsprung weight.
- pads. Optimal choice TBD. The boys in the UK sent me some Raicam (sp?) race pads which they say their guys are getting 4 or 5 races on. I assume it is a very hard compound as a result. I also have a set of Hawk Blues which from have a broader temp range. I've had the caliper paint out and will see what the temps are this weekend at Road America.
- on the choice of manufacturer for the caliper, here's what I have learned. Each clearly makes their product for market demand (price level). I talked to the race tech @ my local dealer. This guy is part of a Le Mans team and I trust his judgement. He strongly recommended Brembo and AP. He does not recommend Wilwood. When pressed, he commented about heat shielding/thermal insulation and seal quality. Is this worth the premium? I don't know.

Fourth, next time through (well, the 355 rotors will last a season or so, right), I'll go with custom hats ($500 - $600 for 4), a decent floating rotor ($65 - 100 each) plus mounting hardware $50/rotor. The big issue for the rears is going to be temperature control (ducting).

As I said, one person's experience. If you go custom, it is expensive, but you can kind of clean sheet the design. I have a lot of respect for guys like Eric that are trying to make it all work within the constraints of the OEM parts.

HTH,
Philip

 

Right, unless they're also putting in the equivalent of spacers to make up the difference to more standard offsets for their alternative bolt pattern.

 

Thanks Philip,

You have a great handle on the situation. I want to develop a bolt-on system and create the least amount of hassle for the customer.
The consideration is how to please everybody. To make a really great system with park brake , new MC and related items, begins to get very expensive quickly. It probably sits in boxes on my shelf.
So I am looking for the best comprimise.

I want to begin by developing a brake set for those who want to put some track time and hard driving on the cars. As well, these customers have probably already changed wheels or are willing to do so to get more tire under the car at the same time.
I can develop a brake set to fit under the 16" rims, but the benefits would be marginal. I am looking to provide real performance solutions and improvements.

As far as using a hydraulic cylinder for the e brake, it has been done, and can be done, but as with everything, it is not as easy as it sounds.
Rally racing cars use a seperate hydraulic circuit connected to the rear only and actuated by a long lever in the cockpit. This is not really a system I am interested in adding to the 308 currently. I am still researching mechanical spot calipers with OE cable actuation.

Ferrarifixer, I am surprised to hear that the F40 brakes didnt give a soft pedal feel, perhaps I am a bit over-worried about this. I have been sweating these details for cars for too many years I think! As far as the parts in the photo, I agree that there is some extra swept area to these discs, but they were done for a special project and the calipers and rotor sizes were such that it had to work that way.The Ferrari components will be a perfect fit.

As far as the bolt pattern vs. wheel offset, the brake hat and wheel mount will be in the OE location from me, as well as be able to accept the 5 x 108 pattern. The advantage here is that a customer can, but does not need to stay with the stock 11.5mm offset and bolt pattern. There are benefits to changing the offset a small amount in either turn-in and high speed stability in turning. It allows individuals to tailor the car to driving tastes as well as having a greater range of wheel widths and types. The reason behind this is to widen the available wheel options.

Philip summed up calipers very well. The long established race caliper manufacturers have a vast base of R&D and history involved with the current designs. Also they have in-house testing for every aspect imagineable, and some that are not. Younger caliper manufacturers such as wilwood build a very good part, and they work well in races every weekend. If your butt is in the car and approaching a turn at the end of the straight, you might rest easier knowing that you invested a bit extra in the brand that has been there for dozens of years.

-Eric

 

Phillip,
What diameter are the 355 rotors? Just looking at the numbers, it looks like the kit add quite a bit more front bias to the system. Does it feel about right now?...or is the bias bar way out of center?

 

I spent some time snoopping about the web this weekend looking at brake stuff. What I found is that it looks like the porsche boxster uses very nice brembo made monoblock calipers that might work quite well on a 308...once the porsche is sand off ofcourse. They are radial mount which makes adapting pretty easy. The fronts are 40/36 pistons, the same as the brembo kit uses. The rears are 30/28, so they have a bit more area than stock caliper which will set the system bias closer to stock than you get with just the front upgrade alone. They are designed to work with a 318x24mm front rotor and a 300x20 rear. The boxster S uses a 318x28 and 300x24 and are the same calipers as the 996. I almost bought a set on ebay today for $514, but decided to wait and try to get a set of 996 turbo calipers. They work with 330x34mm and 330x28 and I think with a little work I can use them with the big rotors I already have sitting on my shelf.

 

Mark
I'll come back with some details on the final bias position. FYI, QV London tell me that the 355 kit works well with the stock bias/booster.

I played with bias a lot this weekend at Road America and tried two different pads. Bias would finally just lock the fronts. Hawk Blue pads worked well. I couldn't seem to get the Raicam's hot enough to get everything out of them. Strong, consistent brake pedal and feel.
Philip