Hey guys. I have a 93 FD with a blown engine. I need to replace a rear rotor and I thought I could just buy any rotor but now people are telling me to make sure I get the right weight. I did some research and I know that there are letters on the gear side of the rotor that tells you what weight it is but Mazda offers one part number for all 13b rotors. So is this something I need to worry about or should I just buy a rotor? If I need to worry about it do I have to get the same letter as the front rotor or a combination of letters? I'm lost please help. Thanks.

 

The rotor weights and compression vary from year to year, and turbo vs. N/A.



Here is a comparison chart:



For your application it would be ideal to get another 13B-REW rotor, but you could also use on from a S5 ['89-'91] TII.








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But as long as it is for a 13b rew I should be fine? Because I heard there are different weights even with rotors from the same engine type.

 

All stock rotors for the 13B-REW motor are 9.54lbs. Some motor builders will remove weight when they "race clearance" a rotor. Of course the weight will vary slightly when you start looking at things like wear and carbon build-up.



But you are correct in saying there are different weights between rotors even from the same type of engine:

 

I'm not sure what the codes for the FD are, but the FC rotors had a letter stamped on them. The codes were A through E, I believe. You want to have both rotors with either the same letter code or 1 letter away - you can run a C and a D rotor, but not a B and a D, for example.

Mazda did that to account for small production variances.

I'd do some searching and hit up the rotary tech forum and find info on the FD rotor weight codes. Most times, though, it isn't that hard to find another rotor with the proper weight - I think the majority were in the center of the range.

Dale

 

You can also send your rotating assembly to Racing Beat and have them balance it if you want to keep the imbalance to a minimum. It isn't very expensive to do that.

-Max