500E Feeler: Interest in 2-piece Girodisc rotors for SA brakes.

[szvook]

Since no one has 2-piece rotors in the 334mm x 32mm and 300mm x 22mm sizes available off the shelf, would there be an interest in having custom rotors made in those sizes? Girodisc can make them if 10 orders are placed, but the price is a bit high, around $1.2K for front rotors and $1.2K for rear rotors. They would need SA OEM front and rear rotors to work off, which I’m willing to provide. It will take them about 3-4 months to complete the order and they would need a 50% down payment on the 10 orders. The rotors will be slotted.

 

[captruff]

I would be interested in a pair of fronts, but would want to know what weight savings there would be? Additionally, I would need the offset to be -2.8mm relative to the factory rotor.

Slightly less interested in the rears at $1,200.00 unless the weight savings are substantial.


Jeff

 

[szvook]

Weight saving would be around 1.5-2 lbs per rotor, front and rear. The offset can be done, since they will have factory rotors to measure.

 

[gsxr]

I really like the idea, but the cost seems prohibitive given the low weight savings. If the weight reduction were more substantial, OR the price was lower, it would be more attractive. As Jeff said, the rears appear to have particularly low ROI since they aren't that heavy to begin with.

For reference, new OE/Genuine SA rotors weigh:

Front, 334x32 are ~24.5 lbs
Rear, 300x22 are ~16.0 lbs

Of interest is that aftermarket StopTech and Alcon front rotors in larger sizes are under 19 lbs each. If Girodisc can only get them down to ~22.5 up front, they might be erring on the conservative side, OR using off-the-shelf rotor rings that are on the heavy side. Personally, I'd want to see at least a 20% reduction in weight to justify the cost, and even then I'd have a hard time with $1200/pair.

Some folks investigated this about 15 years ago and in the end, the price was too high and the weight savings too little, and a group buy never happened. I think the details were lost during the transition from 500Ecstasy to 500Eboard.

 

[szvook]

Dug up my communication with Girodisc from a few years ago and their pricing was $1K for front and $900 for rear rotors in the same sizes. I thought about pursuing them back them, but had other expenses that got in the way. StopTech’s rotors are made in China nowadays and the width on their rotors (fronts) are 334x30, they did not offer rear rotors. That’s what I was told when I spoke with their representatives two years ago.

I too would want the rotors from Girodisc to be a bit lighter, but I already have quite a bit of weigh savings from running much lighter wheels to begin with.

 

[captruff]

Dug up my communication with Girodisc from a few years ago and their pricing was $1K for front and $900 for rear rotors in the same sizes. I thought about pursuing them back them, but had other expenses that got in the way. StopTech’s rotors are made in China nowadays and the width on their rotors (fronts) are 334x30, they did not offer rear rotors. That’s what I was told when I spoke with their representatives two years ago.

I too would want the rotors from Girodisc to be a bit lighter, but I already have quite a bit of weigh savings from running much lighter wheels to begin with.

Additionally, please look into a 2 piece rotor for the 300mm fronts for use with the Aluminum Brembo or 500SL cast iron ATE calipers. I run the Aluminum Brembo on 2 of my 16Vs with the 300mm S:L600 rear calipers and would not run a 2 piece rear rotor if I could not run a 2 piece rotor up front as well.

Replacement costs on replacement rings would also be of interest.

Jeff

 

[gsxr]

Ooops, I should have clarified. I was referring to StopTech's (NLA) $2500 front big brake kit for 500E, with 355x32 two-piece rotors that weigh ~18 lbs. If they can make a larger rotor weigh 18 lbs, why can't Girodisc at least match that 18-lb weight for a smaller 334x32?

Jeff, the 300x28 fronts are already <17 lbs each. The ROI would be really poor making a 2-piece version of this rotor, IMO. The weight savings would have a negligible effect on performance. If you are warping rotors due to excess heat, a 2-pc design theoretically could help, but that's pretty much a track-only concern.

For reference... Mercedes went to 2-pc on AMG models when the 1-pc rotors became insanely heavy. The early AMG's with 360x36, one-piece front rotors weighed THIRTY FIVE pounds. WHen AMG changed to 2-pc design, the same size dropped to ~29 lbs, and the thinner 360x32 two-piece were down to <24 lbs. Also of note is that AMG never bothered with a 2-pc rear, at least not through the W211 or W209 chassis (not sure about newer models).

 

[captruff]

Ooops, I should have clarified. I was referring to StopTech's (NLA) $2500 front big brake kit for 500E, with 355x32 two-piece rotors that weigh ~18 lbs. If they can make a larger rotor weigh 18 lbs, why can't Girodisc at least match that 18-lb weight for a smaller 334x32?

Jeff, the 300x28 fronts are already <17 lbs each. The ROI would be really poor making a 2-piece version of this rotor, IMO. The weight savings would have a negligible effect on performance. If you are warping rotors due to excess heat, a 2-pc design theoretically could help, but that's pretty much a track-only concern.

For reference... Mercedes went to 2-pc on AMG models when the 1-pc rotors became insanely heavy. The early AMG's with 360x36, one-piece front rotors weighed THIRTY FIVE pounds. WHen AMG changed to 2-pc design, the same size dropped to ~29 lbs, and the thinner 360x32 two-piece were down to <24 lbs. Also of note is that AMG never bothered with a 2-pc rear, at least not through the W211 or W209 chassis (not sure about newer models).

Dave:

I have not warped any of the front 300mm rotors used with the Brembo aluminum calipers, however, I have warped 2 sets of the 334mm SA front rotors on my S124.

The application for the 300mm front 2 piece would be for my 16V and I would not expect a lot of weight reduction. That said, since I have gone to much effort to reduce extra weight (e.g., lithium battery, manual regulators, no radio, no AC, manual seats, etc) I probably would pull the trigger on 2 piece front and rear rotors if there was 1lb to be saved at each corner, 4 lbs total.

Jeff

 

[szvook]

Additionally, please look into a 2 piece rotor for the 300mm fronts for use with the Aluminum Brembo or 500SL cast iron ATE calipers.

I did ask them about other sizes, but was told that for custom rotors, the order would have to be for the same sizes.

 

[captruff]

I did ask them about other sizes, but was told that for custom rotors, the order would have to be for the same sizes.

The 500E front rotors for the Brembo are 300MM in diameter as are the SL600 rear rotors, but the design of the hat would differ due to the P-brake in the rear.

Jeff

 

[szvook]

Ok, just got off the phone with their senior tech and it seems (based on the casting for the outer rings) the front rotors could be 3-6 lbs lighter and the rear rotors could be 2-4 lbs lighter. But to be sure, they would need to start with having OEM SA rotors and go from there.

 

[gsxr]

I have not warped any of the front 300mm rotors used with the Brembo aluminum calipers, however, I have warped 2 sets of the 334mm SA front rotors on my S124.

That is very unusual. Was the warping confirmed with a dial gauge, and also confirmed to not be material transfer from pad to disc causing a pulsating feel? I assume OE/OEM discs, but what pads were used? I'd try cryo treatment and possibly change pad compound. If the S124 is only seeing street use, there's no way the 334's should be warping. Vookster tracked his 500E with those brakes (and ~50% more power) and AFAIK never warped a set.

The application for the 300mm front 2 piece would be for my 16V and I would not expect a lot of weight reduction. That said, since I have gone to much effort to reduce extra weight (e.g., lithium battery, manual regulators, no radio, no AC, manual seats, etc) I probably would pull the trigger on 2 piece front and rear rotors if there was 1lb to be saved at each corner, 4 lbs total.

You should be able to achieve at least that much improvement, but the cost may be substantial. If Girodisc won't do it, there are some other mfr's who may be willing to make 1-off sets for you.

The 500E front rotors for the Brembo are 300MM in diameter as are the SL600 rear rotors, but the design of the hat would differ due to the P-brake in the rear.

The early 500E fronts are 300mm but 28mm thick, while the SL600 rears are 300mm but only 22mm thick. Two different 300mm discs would be needed, besides the hat difference.

Ok, just got off the phone with their senior tech and it seems (based on the casting for the outer rings) the front rotors could be 3-6 lbs lighter and the rear rotors could be 2-4 lbs lighter. But to be sure, they would need to start with having OEM SA rotors and go from there.

6lb reduction up front, now we're talkin'!

 

[szvook]

The 500E front rotors for the Brembo are 300MM in diameter as are the SL600 rear rotors, but the design of the hat would differ due to the P-brake in the rear.

Jeff

I’ll ask them.

 

[szvook]

Vookster tracked his 500E with those brakes (and ~50% more power) and AFAIK never warped a set.

Yep, still straight.

 

[szvook]

@captruff For the design of the hat due to the P-brake in the rear would be a separate order and they can’t do just one order.

 

[captruff]

@captruff For the design of the hat due to the P-brake in the rear would be a separate order and they can’t do just one order.

So are you only planning to do the 334mmn SA front rotors?

Jeff

 

[szvook]

So are you only planning to do the 334mmn SA front rotors?

Jeff

Yes and I would need SA front and rear rotors. Any other custom sizes would require a separate order of 10, otherwise Girodisc will not do a smaller order.

 

[szvook]

Ok, this is not getting any traction and I figured that it would not. Looks like I’ll be getting a set of Zimmerman rotors, as my current rotors are getting close to being done.