930 Caliper Question

[dickster]

i got my oe rotors for £70 a pop in the uk. gotta be worth shipping a few at that price.

[jpachard]

Bill, While I agree that the Brembo's have some improvements in design, I also need concrete evidence that they are worth the money. I go through 8 sets of brake pads a year plus a set of rotors during a normal season. This adds up. As an engineer I completely understand the argument for the Brembo's but experimental evidence is key( what temps are your brembo's running vs. Coleman's, how many track days do you get out of your rotors etc.) When you make a statement like" What would you trust your life to" I belive you need to back it up with hard evidence and numbers.

Cheers, James

[89911]

I just got back from a weekends worth of track driving on my new Brembo front rotors. Bill posted a pick of the set that I had used prior, which were Colemans. They lasted exactly one day of track driving prior to warping. I was using new pagid orange also. Since these cost me $650 with the hats, needless to say I was p*ssed. I had them cut to get the annoying shudder out of them for the street use, but was forced to use them at the Glen for a 3 day event. After the 2nd day, they rewarped and are now off the car. I used the Brembos last weekend with no sign of any warpage on a track that was much harder on brakes then the other 2 prior.
I retrospect, the 930 on earlier cars has its advantages and pitfalls. Advantages are: Porsche Original equipment, Fits 15" and 16" wheels for retaining your Fuchs, More then adequate braking for any early car other then a Turbo, Pads are readily available and prices ok, Pads are very easy to change, Front to rear pads can be swapped to even pad rear. Rear rotors are inexpensive turbo's Disadvantages are: FRONT ROTORS! Factory are hideously expensive, at least in US, Other alternatives are just as expensive or inferior, Rear calipers require major machining to fit, you require a master cylinder change.

Now that I have all the bugs out (biasing valve removed, brake cooling added and the proper rotors), I am finally done with the brakes and have enjoyed them. Lets hope they hold up.

[jpachard]

89, Did you check the runout on the rotors? Pagids leave some nasty high spots and deposits on rotors when not bedded in well. It's been my observation that pagids don't play well on rotors that don't have good gas evacuation( ie holes or lots of slots). I doubled the bed in procedure when I mounted the Coleman's and had no problems at Road America( 4 Club Racing plus two days at Limerock).

Cheers, James

[Kahuna]

Another negative vote from me on the ability of Colemans to last as well/long as the ridiculouly expensive factory rotors.

For factory Brembos theres Mastercard, getting through a race weekend pricelesss!

[KTL]

Sorry to interrupt/get a little off topic. Since Mike (89911) brought up the issue of warping, maybe the guys in the know (Bill, James) could clarify the "myth" on warped brake rotors so others on the board could benefit from their knowledge on this issue.

Warped brake rotors are apparently not a function of the iron of the rotor itself changing shape. Assuming the hub and hat surfaces are not showing excessive runout, the warpage is the uneven deposition of pad material onto the rotor. Seems like there's more to the issue than just pad material deposition though?

http://www.stoptech.com/whitepapers/warped_rotors_myth.htm

So my question is, what makes the Colemans more prone to this condition than the Brembos? Is it the cross-drilling and/or slotting issue that James mentioned? Or is it some sort of metallurgical deal?

Thanks for the good info. so far!

[BURN-BROS]

Bill's pic shows the difference in mass between the two. The more massive your rotors are the more effective they are in temperature control. the colemans look less robust.
I have turned a few rotors that had runnout and its hard not to believe that they do not warp.

[jpachard]

Yes, Rotors warp. I believe the article that Kevin posted states this situation very well. What I have found is that there are many facets to this problem and one needs to tailor each application to the car/driver. For example, you would not mount these rotors on a shifter cart and vice versa you would not put shifter cart brakes on a Porsche. Things that have to be considered are the following;

1. Car Weight
2. Driving Style( late braker, correct braking procedure etc.)
3. Pad compound
4. Rotor heat( too little is almost as bad as too much)

Through my observations, I found that the Coleman rotors mass suited my driving style since I was able to get the rotors in the temp range to where the pads were working well. Will they work the same way for someone else, of course. My mechanics' GT class car has had them on for a whole season without a glitch, yet as others have stated they didn't work so well for them. For me it's worth the money savings and service I get from them. I guess if someone else can benefit from this, take away some knowledge regarding this topic and possibly save some money, thats what's important.

Cheers, James

[BURN-BROS]

Well said James, I agree

[89911]

To answer a few questions: Yes there was runout, enough so as to be visible to the naked eye. There is a big difference between something that "fits" and something that is "correct". I unfortunatly paid the price (to the tune of $1400 for TWO sets of rotors). The very least I can do is save someone else the cost by giving my opinon. The is absoulety no comparison to the quality and mass of the two rotors, and the heavier one are only $100 more if you compare the prices with hats, head to head. Perhaps my experience is unusual. This is what the original vendor has stated. They also did not offer any recourse to correct the situation. RennSport did stand behind their product and offered to have me return them if they do warp. Judging from the quality it won't happen. They also stated that some of their biggest business if replacing the rotors of drivers like I, who purchased the Colemans in the first place. If you just spent $600 on a set of rotors and they warped, would you just turn around and buy the same ones again?

[jpachard]

89, You paid 700.00 per set for those rotors, ouch! I would be upset too. I paid 352.00 with shipping for my set custom made to my specifications. I got mine direct from Coleman.

Cheers, James

[hobieboy]

For the confused folks like me out there - is there a quality difference between the Brembo ones & the factory ones (which is made by Brembo AFAIK)?

Thanks.

[89911]

Originally posted by jpachard
89, You paid 700.00 per set for those rotors, ouch! I would be upset too. I paid 352.00 with shipping for my set custom made to my specifications. I got mine direct from Coleman.

Cheers, James

VCI's price was $650 including the hats for the fronts. Replacement were $450 rotors alone. Rennsports were $750 for their own different hats and the Brembos. These came directly from Brembo. From what I've dug up, the OE rotors for the 79-80 run close to $500 for a set, but you still need either the OE hats which are even harder to find and most don't even carry these, or VCI's and then you need the full floating hardware, another $160. Apparently you can find Colemens cheaper the VCI's. I won't consider using anymore, so they don't fit into the equation. I didn't go into the 930 upgrade as a means to boost the economy, I't just turned out this way. If I was to do it over, I would of got Big Reds and lost the Fuchs. Much less headaches and cheaper.

[don911]

As recommended by Dean (aka Blown) on the board, I put on the 78-80 OEM rotors and floating hardware. The initial cost is high but I'd do it again....especially after reading this post. I've done two full day track days with 45min to and hour sessions. I've put 500-600 track miles on these brakes and not so much as a wiggle in the rotors. The 930 brake change is very expensive overall and I think it's worth the extra $$ to put on the OEM rotors. Just my opinion.

[widebody911]

I got lucky when I installed my 930 brakes , in that my car has turbo fenders, so everything bolted right up, no muss, no fuss, and I can use stock bits.

It could get interesting with an aftermarket custom setup - what happens when you need parts 2 years from now? 5? 10?

[89911]

Originally posted by widebody911

It could get interesting with an aftermarket custom setup - what happens when you need parts 2 years from now? 5? 10?

Easy, you'll pay through the nose for them!

[Bill Verburg]

BURN-BROS,
The post '80 930 front rotors are a 1 piece design, the '78-80 are a multipiece design. One of the pieces used on a '78-80 930 front is a 28mm spacer, for use on a 911 the spacer in discarded. Unfortunately the 1 piece rotors have the spacer integral to their casting, it cannot be discarded and so they can only be used on widebody cars like Thoms(widebody911)

don911,
I have used Colemans and factory 930 304s(Brembo), the factory 930 Brembos are superior in every way but the price. I can get 993tt 322s at half the price of the 304s. Unfortunately those that use the 930 calipers do not have this option and should use the factory Brembo rotors. The Brembo 322 is really more brake than I need but it's a much better deal financially.

KTL,
Rotors do warp, one piece and thinner will warp more/quicker than floaters or thicker ones. The reason why was discussed in this thread

There is a continuum of track applicability in rotors, at one end is the stock ATE 282.5x20, followed by ATE 282.5x24, Coleman 304x32, Brembo 304x32, Brembo 322x32, Brembo 355x32 Brembo evo 380x32 somewhere in there is a rotor for every one. The problem is finding the one that is best for your situation. If the ATE 282.5x24s are just barely overheating then sure the Coleman 304x32 may be fine. For me and a lot of other ex Coleman users it wasn't good enough.

[Bill Verburg]

By the way James whatever happened to the Alcons you had?

[jpachard]

Bill, I sold them along with my Carrera setup and got some 930 calipers. By the way, what pads were you running on the Coleman's? Pagid Orange, Black or something else? Which track did you have the warpage at or what made you realize the Coleman's weren't enough?

Cheers, James