Yep. Mazda nor any race shop that knows what they are doing replace in-spec bearings. New bearings also have a higher failure rate than using older in spec bearings. Racing Beat also made note of this years ago.

That is correct. Straight from Racing Beat's tech section:

"Rotor bearings do cause occasional problems during high RPM operation. It is important to use properly clearanced rotor bearings. In general, do not replace rotor bearings when you are re-using rotors unless they are over the recommended clearance or show some damage from dirt, heat, or lack of oil. Our experience has shown that used bearings in good condition are safer than new, untried bearings."

At the bottom, from the rotor bearing section http://www.racingbeat.com/Tech/Tech.Engine.2.htm

Rich, you are not doing your customers any favors by replacing in spec bearing during an engine rebuild. Also, it is not free, you are including it in the cost of the build somewhere. You are not getting the bearings for free and you are not installing them for free.

the rotor bearing is broken into the eshaft...
you replace the rotor bearing with the new one, but you reuse that old eshaft that had been worn to the old bearing...

i believe it is best only to replace it on an as-needed basis under that circumstance.

unless you have a new e-shaft with a rotor bearings... i fail to see any gain from using a new rotor bearing - esspecially when it will wear at an accelerated rate against your 20 years old worn out e-shaft....

Chris, keep your unsolicited advice to yourself. I don't remember asking you for it. In the future feel free to PM me with whatever may be on your mind. Thanks.

I've never seen an engine with fresh bearings spin one for no reason. However, over the years I've seen three (three!) FD engines spin bearings under normal driving conditions, all of them with 90k+ miles. As mentioned, one had already been rebuilt 25k miles ago with 'in-spec' bearings.

We've built over 100 engines, most of them with new bearings, and have had zero (zero) problems. These engines all were original and had the original bearings, and all of them had ~50k+ miles. All showed excessive wear and many had a high percentage of copper showing. Were they in spec? Nope, not the majority of them.

They are installed for free, and the markup on the cost of the bearings is negligible. Frankly I'd rather leave them in there, but in many cases I feel the right thing to do with a new engine build..... is to start with new parts, including new bearings (which are a wear item).

As I've already stated, different strokes for different folks. Let people make up their own minds..... cost/benefit analysis is pretty easy to figure out in this case. I for one don't enjoy arguing for the sake of arguing.

Taking more time to break in for a healthier engine im sure someone serious in the subject is willing to do it.

I personally install(or request to be installed) new bearings in all my rebuilds over the years. never run into the issues Banzai is saying but im sure you guys have seen way more than i have

I think what you are doing is the correct course of action.

Rich, there is no reason to get angry. I am just putting the info out there so that the "masses" can decided for themselves

Wow, really? People must be doing something to their oil out there. We tear down between 75-100 engines a year, all varying mileage and age, a small percentage of them have bearings that are out of spec. It is amazing that every engine you have built the bearings have all been out of spec. I can not even calculate the odds.

The fact is that is does not matter if the bearings are 17, 20 or 50 years old. We have customers with cars that have less than 10K original miles on their FDs & FCs, the bearings are not worn out just because they have been sitting in the engine. Most higher mileage FDs are not on their original engines anymore, so even that arguement is moot.

Heat, oil grade, pressure, etc have more to do with bearing wear then mileage or age.

Rotor housings are a "wear item". If you really want to do it "right" with a new engine build every engine would get brand new housings and irons along with bearings and e-shaft. The point is Mazda has specs for all of these parts for a purpose.....that is so that they can be reused while rebuilding an engine.

Rotor and main bearings are $150-$200 depending on where they are purchased, this is not a "negligible" price increase to throw at every engine.

Of course you do. :)

Appreciate that, it's always good to hear from other respected engine builders.

Speaking of which, I just got off the phone with Chris Ott from Rotary Performance. When I was active duty Army and stationed out at Fort Hood I spent many weekends there with them. They've been in this game since 1988 and I typically look to Chris and Ari for any advice because I respect their opinion immensely.

In a nutshell, this is what Chris Ott shared with me regarding their practices:

*On FD engines they almost always replace main bearings. Rotor bearings it depends on the condition but more often than not they replace them. Due to their greater surface area they tend to not wear at as high a rate.

*He said that if any copper was showing on the bearing they would absolutely replace them without question.

*They've found that due to early recommended lightweight oil use on original engines as well as typical infrequent oil changes early in the car's life the main bearings in particular bear the brunt of this less than ideal service.

*He said that replacing the main bearings is in his opinion vital to optimal engine health. It takes slop out of the rotating assembly and keeps the rotor more square on the bearing, avoiding any contact of the tips of the rotors with the irons.

*They rarely ship motors out to customers so they're able to run the engines in-shop and with the new main bearings he's found the engines run better.

*He also agreed with me that replacing bearings just makes sense when building a street engine where a customer expects a certain degree of longevity.

Four new bearings were < 10% (probably closer to 5%) of the total parts cost of my rebuild, including having them pressed in by a local shop.

Thanks Rich. Next question: it is necessary to yank the motor to replace main bearings?

Also, does anyone believe heavier weight motor oils (e.g. 20w-50) can accelerate bearing wear (particulalry cold start wear)?

True but I meant the engine and not the chassis. ;) There is a very small group (myself included) that have had the original engine last that long. My bearings are perfectly with-in spec.

Rich I perfectly understand where your comming from by replacing the bearings. When dealing with X amount of customers, it's just added piece of mind. However, we all know those customers will blow the engine by some other means besides bearings now don't we. ;)

For anyone running used main bearings, I would get a used oil analysis done ASAP, it will give you useful information on how the bearings are wearing (plus other wear metals, % fuel dilution, etc).

I think ill listen to what Mazdaspeed and Racing Beat prefer over what any shop says. Yes, replace if necessary but not because im already in there and its new parts.

Can I jump in here with a related question;

I have a new set of bearing with my lightened & balanced set. I will be getting the rear main race bearings but it just doesn't seem worth replacing the rotor bearings to the race spec when it is something like .0005 more clearance. Expert opinion please?

IIRC, the race bearings also have a little deeper oil channel.

I recommend it.