Pull Scales and Cotter Pins

One of the things I have to address on my RX-7 are the front wheel bearings. Since Mazda made them as hard as possible to extract from the hubs, I wound up buying some decent used hubs off of eBay for $59 (beats the hell out of $933 for all-new hubs). The FSM and Hayne's manual both say I need to use a pull scale and new cotter pins to adjust and install the hubs. Where do I buy a pull scale and new cotter pins? For the pull scale, what should be the upper measurement range (ft-lb)? Do I have to get the cotter pins from Mazda?

hello? machine shop?

I know, I know. I've called three local ones and so far they've all told me they don't do that kind of work. No idea why, even when I mentioned I'd pay them for it. Maybe I'm not calling the right ones?

Mazdax605 has a shop about an hour and a half's drive from where I live, but I don't know when I can make it down there. So, I saw these on eBay, and I bought them. Worse comes to worse, I'll have an extra set of hubs I'll need to fix.

Pull scale??? for bearing drag? Those things are pressed on so where is the adjustment? I'm not being a smartass I really don't know.

Cotter pins are in the HELP! section assorted sizes $3.XX

This reminds me, I once had a job of building gear reduction boxes for the Navy. Basicly it opened and closed a steam valve with an electic motor. We had to preload the bearings to a set tolerance of spinning resistance measured in inch ounces. We ended up winding a string around the shaft and using a fish scale to measure the resistance. Using a three dollar fish scale to calibrate a hundred thousand dollar gear box just seemed wrong.

nickel_dime wrote: Using a three dollar fish scale to calibrate a hundred thousand dollar gear box just seemed wrong.

Grassroots is grassroots no matter who writes the check. That is the process I was going to suggest. And if you're off by 10% is that a big deal?

Dan

Pull scale = fish scale if you feel you need one.

I am guessing this is either an FB or FC based on the trends of this board, those both used tapered wheel bearings. Whats so hard about changing those? Anyway you want to tighten the nut pretty snug and then back it off some to get the preload right and install the new cotter pin. I have always just done it by feel and never had any bearing problems, but I had a good teacher the first time.

jrtech wrote: Pull scale??? for bearing drag? Those things are pressed on so where is the adjustment? I'm not being a smartass I really don't know.

http://foxed.ca/rx7manual/manuals/1988FSM/09_FRONT_AND_REAR_AXLES.pdf

Pages 5 and 10 of this FSM .pdf.

SupraWes wrote: I am guessing this is either an FB or FC based on the trends of this board, those both used tapered wheel bearings. Whats so hard about changing those?

FC3S. I was under the impression the inner bearings and seal and both races had to be pressed in/out. Had a local machine shop agreed to do the pressing for me, I may not have bought these hubs. It's too late now and they're on the way here. I'm not going to complain unless the new hubs are toast.

SupraWes wrote: I had a good teacher the first time.

I don't. I've never replaced hubs or packed bearings before, so I'm doing this by the book.

Setting tapered wheel bearings is pretty easy. Disclaimer: I did a stupid on a Spitfire one time, tried to remove all the play yet still have the rotor spin freely. The next day the outer wheel bearing seized. Moral of the story, tapered bearings need a small amount of free play to allow lubrication.

Here's how I have done tapered bearings many times over the years: pack the bearings with fresh grease, assemble the hubs, tighten the nut until it got 'snug' (not tight). I then turn the hubs by hand to settle the bearings, then tighten it to 'snug' again and turn the hubs once more to settle the bearings. I then back off the nut about an eighth of a turn at a time, until I get to the point where the hub spins freely but has barely perceptible end play (pulling in and out on the hub). Now check to see if the cotter pin can be put through the hole. If it can't, loosen (do NOT tighten!) the nut ONLY enough to be able to put the cotter pin through. I did my first gen RX7's and all the other Spitfires etc this way and also my MGs, they are supposed to use shims to set the bearing end play. Never had a problem with any of those. The J-H has ~ 8000 miles on the front hubs done the same way, no problems. I also have done trailer wheel bearings the same way with good results.

Now, if it were a double row ball bearing like a FWD setup, those have to be clamped tightly together. Preload is essential to bearing life on those.

OK I get it now. Thanks for the PDF. They are the tapered style. Pack the bearings with grease, tighten the castle nut up and spin it to seat the bearings like it says, then back it off a few degrees until it is easy to turn by hand, check the play in the bearing, there will be no noticeable play in the bearing when set up correctly, there should be a little drag when turned. Cotter pin, dust cap. There you is. Pull scale is unnecessary. Not too tight not too loose.

EDIT: He just beat me to the punch. Well said Jensenman.

You can change out the bearing races with a hammer and punch, you don't need to have them pressed. That crazy canadian with the redneck rollercoaster car on youtube recently did a video on bearing changes lemme see if I can find if for you.

This is it.

http://www.youtube.com/watch?v=ptrhjnTD3jY

Thanks, everyone. I'll let you all know how it goes once I get the parts.

Fish scale from wally-world is what I've used in the past.

Replacing the races is not as simple as it should be (no thanks to Mazda), but it's not really hard if you have a rotozip with the flexible attachment. Just grind notches on either side behind the races and then punch them out.