As some of you may know I'm getting the RB BBK with a set of XT910s. I'm thinking of doing the install with a set of r4s instead of the XTs as winter is coming.

My question is does it matter which set of pads I use to bed the new rotors?
Because to my understanding bedding is to get a layer of pad material on the rotors and I'm worried that if i bed them with r4s it will decrease the performance when I put the XTs back on. Or does it not matter and i just need to re-bed them after the switch?

 

It does matter.

Brake rotors and pads both develop grooves over time. Brand new surfaces will mate perfectly. However, if you have previously worn rotors, which you will when you install the XT's, the rotors will have already developed "hills and valleys", per se, from the R4s pads. Therefore, you'll have to mate the flat XT pads to the grooved rotors. It's fine I guess, but it'll just take you a while to do so as the pad will not be making 100% contact with the rotor until the hills and valleys have been worn into the XT pads.

Kind of a ramble, I know.

Make sense?

 

https://zeckhausen.com/catalog/index...Path=6446_6443

 

Not really.

Totally. Pretty good explanation I think. You generally do a pretty good job of explaining things.

 

Agreed. You basically told me what i should do. Albeit a bit more of work.

 

Thanks man

It is. But I've been there done that with pads and rotor mating and it can get pretty anointing pretty quickly. If the two pad materials don't play well on the rotor, for example, you can get some shuttering and/or vibration too.

In theory, what you mentioned in your OP is totally doable. You'll just have to take a while to bed in the XT pads (30+ high speed brake slams until 10 mph) and you'll reduce their life.

When my buddy swapped new Endless MX72's on his S4, he said they needed about half a track days worth of abuse/heat to feel completely settled into the previously used rotors.

 

That's not what the bed-in process is for. It's to gradually bring both friction surfaces (pad & rotor) up to temperature to transfer material.

I didn't look through that other link roadkillrob posted but Stoptech has a decent white paper on it.

http://www.stoptech.com/technical-su...ake-pad-bed-in

You can also repeat this process later on if you end up with glazing. It can happen on a street driven car.

 

Yeah totally, but I didn't really mention the pad layer transfer much since I don't think it'll be useful to OP's question.

 

He's swapping pads though. He'ill have to repeat the bed-in process with each pad swap.

 

I can choose to only do bed in once if I decide to leave the XT pads on the rear. I have a set of OE front rotors to go on for the winters and that will be with the r4s. (BBK fronts are too big for my 18' winter rims.)

 

Just do the bed-in process every time you change pads and or rotors.

 

Plus it's fun! Hard acceleration, hard braking...repeat...repeat...repeat...

 

Well yes, but transferring pad material will be the least of his issues here. The real problematic area is bedding the surface "hills and valleys" which'll take more effort than the standard bedding process.

Like I said, not necessarily a big deal, but something to be cognizant about when thinking about doing this.

 

Wearing a pre existing rotor groove profile into a pad is not the bed-in process. That's all I was stating and it's what the OP asked about.

 

FWIW... in the past I used to swap pads on my cars probably a dozen times per year for track events. When race pads are cold, they are very abrasive (essentially like sand paper). I'd put them on on Thursday afternoons, bleed the brakes and drive around town on Friday and to the track on Satruday morning. By the time I'd get there the rotors would be scrubbed clean. Slowly get them nice and hot (bedded in) during the first session - they will stop squealing, you could see the material transfer film on the rotors and you'll feel that they are starting to bite a lot better - and then pound on them all weekend. Drive back home on the race pads on Sunday afternoon and around town on Monday, and by Monday evening they'll again squeal like stuck pigs and rotors would again be scrubbed clean. Put street pads back on and enjoy squeal-free driving for the next two weeks. Repeat for the next track event.

When track pads are cold they will scrub the rotors and get rid of any material transfer, even if it's from the same pads. In other words, even if you put on new rotors and a set of track pads and bed them in properly until you have a nice material transfer film on the rotors, you will completely scrub them off in a couple of days of street driving. And, I've never seen a heavily worn "grooved" rotor that wasn't cross-drilled, so the RBs will in all likelyhood be just fine and wear much more evenly than OEM rotors. Yes, you will have some fine grooving, but it will take all of one or two days for the new pads to wear down the high spots until the entire pad surface touches the rotor. I haven't used the XT pads, but if they are like most other track pads, keep in mind that even after they're bedded in, they will continue to scrub off their own pad material from the rotors during street use and you'll need to heat them up again to get pad material transfer back on the rotor before every track day.

So - feel free ot use the R4s in the winter, then put the XTs on in the spring, DRIVE CAREFULLY AND SLOWLY for the first few days (you won't have a lot of stopping power and also you don't want material transfter from the XTs - you only want to scrub the rotors from the R4s), and when they start to squeal you can bed them in by bringing them up to temperature. Repeat as necessary.

 

Here's a better explanation of what I was tryign to say above: http://www.stoptech.com/technical-su...res/bed-in-faq

 

that's what I've always done when I change pad and rotors. so far I haven't died so i say its working.

 

Just stop bedding pads in by the beach...

 

LOL! True dat.

 

The XT pads I have are 910s (spirited/trackable) not the 970/960 full on track pads. So would everything you said still apply?

 

Yes. It might take a little longer but the process is exactly the same. You can put the "milder" XT pads on and drive the car in the city for 2 weeks instead of 2 days without fully heating them up (by this I mean without pad material transfer to the rotor - it will be grayish-blue), and they will scrub the rotors clean. A clean rotor looks like bare metal, without any grayish-blue spots.

The only scenario where there is a potential for problems is if you use a mild "street" pad at the track and overheat it. You'll get a lot of material transfer on the rotors, and that's when you really need to get it all scrubbed off before bedding in the new pads because the new (even hotter) pads will smear and bake this material on even more, resulting in build up on the rotors and nasty vibration.

Another DIY on scrubbing off baked-on pad deposits from StopTech: http://stoptech.com/technical-suppor...eposit-removal. It essentially says how to scrub the rotors using the more aggressive pads, in your case the XTs. And, just to be sure, I'd contact Johann at RB and ask if the 910s are abrasive when cold. We were chatting for quite a while when I bought mine and he certianly seems to know his stuff. Bottom line is - pretty much any set of pads (no matter how mild) will scrub the rotors clean over time if you don't periodically get them nice and hot.