R1 Concepts brake rotors

[Rionart]

Does anyone have any experience with the slotted/cross drilled rotors being offered on evilbay?

eBay Motors: OPEL MANTA 70-8/74 SLRD Brake Rotors PREMIUM D/S Frnt (item 370102522034 end time Nov-23-08 13:52:38 PST)

eBay Motors: OPEL MANTA 8/74-75 SLRD Brake Rotors PREMIUM D/S Frnt (item 260305499598 end time Nov-23-08 13:52:44 PST)

[blancojp]

I have used these previously on a customer's '71 Opel GT.

They are nothing more than drill/slotted version of the Delco 18A1406 rotors. Though rare and hard to get, they are quite over priced for the application. You can get them from Delco about $35 less for the pair and no freight.

[LeftLaneGuy]

Well, considering that having new rotors cut and drilled will cost you at least $50 each to have done by a shop that knows what they're doing, that's not a bad price.
The jury's still out on if these really make a difference.. I have drilled rotors on my GT and wagon. The wagon *seems* to benefit from it a little, but only in the fading dept.. (hard mountain roads) BUT they do make a little bit of noise... The slots may make a difference, I don't know, as the shop I've had mine done at doesn't cut slots..

Be the Guinea Pig! Do it! Then tell us what you've found.

[stosh562]

i was wondering about these for my Opel too. I have had experience with this company before. i bought their rotors for a Dodge Shadow i had and i absolutely loved them. i thought the quality was top notch. I just can't figure out why they have so many different listings for the Opels.

[kwilford]

One thing I have learned the hard way about cross-drilled and radiused brake rotors is that they are NOT machinable, at least according to about ten brake shops that I have contacted. I bought a set of cross-drilled and radiused rotors with matching ceramic pads for my Lexus IS300 a couple of years ago, and the front rotors developed a bit of a warp. They are pretty easy to pull off, so off they came, and then I spent the next week going from shop to shop to try to get them turned. None of them would even touch them, as apparently the cross-drilled holes and also the radius slots disrupt the machining tool as they pass the tool face.

I still had the OEM rotors, so I had them machined and put them on. The brakes aren't quite as responsive, but they are quieter (the cross-drilled and radiused rotors DEFINITELY make a growling noise as the pads engage).

I have a set of cross-drilled and radiused Opel Big Brake rotors that I bought from a fellow (they also fit the Lotus Esprit) that I will install on the SportWagon someday. While they look nice, it does concern me that they are basically a "one-use" rotor.

JM2CW

[officertyo]

Originally Posted by kwilford basically a "one-use" rotor. JM2CW

Not true at all. They can be turned. I have turned many sets. It takes a little more skill then normal rotors to cut but it can be done. The people you took yours to either didn't know what they where doing or just down right scared to touch them. You can send them to me if you like and i will turn them for you.

[stosh562]

I agree. i work in a machine shop and if one of our CNC lathes crash all you do is turn the jaws back down smooth and round again. makes a hell of noise but you just feed very slow and no problems. And that's with a tool holder and insert about the same size you would use for a rotor. the shops you went to probably don't know how to slow the feed rate down or don't want to.

[Gumby]

Originally Posted by kwilford One thing I have learned the hard way about cross-drilled and radiused brake rotors is that they are NOT machinable, at least according to about ten brake shops that I have contacted. I bought a set of cross-drilled and radiused rotors with matching ceramic pads for my Lexus IS300 a couple of years ago, and the front rotors developed a bit of a warp. They are pretty easy to pull off, so off they came, and then I spent the next week going from shop to shop to try to get them turned. None of them would even touch them, as apparently the cross-drilled holes and also the radius slots disrupt the machining tool as they pass the tool face. JM2CW

Those shops didn't know what they were doing or simply didn't want the work. There is no reason why you couldn't machine them it is just a little harder on the tools because of the interrupted cuts.

Originally Posted by stosh562 I agree. i work in a machine shop and if one of our CNC lathes crash all you do is turn the jaws back down smooth and round again. makes a hell of noise but you just feed very slow and no problems. And that's with a tool holder and insert about the same size you would use for a rotor. the shops you went to probably don't know how to slow the feed rate down or don't want to.

The noise depends largely on the machine I would think. I wouldn't think the feed would be the issue so much as the DOC. Milling by its very definition is an interrupted cut and the tools seem to do just fine. The proper grade of carbide with a .031" radius and some where around 600sfm? Cast iron isn't terribly difficult to machine, just messy.

[blancojp]

For the same money (price & freight) you might be able to upgrade to a vented rotor using the existing mechanicals. I say maybe because auto parts vary in price throughout the nation. There are also two different rotors for the same car, with different size hat in the same year, one works and the other one does not.

If you use a a 1986 Nissan Sentra wagon rotor and a BMW caliper widening kit, you will have the advantage of a vented rotor while retaining the Opel caliper, hoses and so on. This rotor is 20mm thick which is twice the thickness of the stock rotor therefore the caliper needs to be widened at the pad opening from 15mm to 25mm.

This upgrade is as follows:

1) The Nissan rotor Dim B is 49mm, versus 55.5mm for the stock rotor. Diameter is the same so caliper location is the same. To mount onto the hub, reduce the back hub diameter to 65mm, add 5mm spacer to place the rotor at 54mm and assemble. The 1.5mm difference in Dim B is resolved by the caliper wide kit and the pad location compliance during the initial brake bleed.
The cost of this is approx. $90 including the rotors.

2) The BMW 740i caliper widening spacer kit is $35 and includes the caliper spacer, o-rings, longer bolts and longer pad mounting hardware. They are hard to find but still availabe. The kit has all needed for two calipers.

3) Assemble the hub, mount on the spindle, bleed and you are ready to go.

I should come up with a kit and put on Ebay to see what happens.

I hope this helps but remember, brakes are your life when driving so please make sure they are properly done by a qualified technician.