85 Fiero Rear Bearings seem stiff (Page 1/1)
NuClearFuRy SEP 04, 07:15 PM
My question is how should the travel on the front wheels compare to the rear when up in the air.

We have an 85 Fiero and while changing both rear calipers we noticed that while up in the air the rear wheels don't travel very much. Removing the old calipers helped but not much. The rear wheels give maybe an inch or 2 of free travel after let go as compared to the front wheels that travel for seconds and take far longer to stop on their own. The front calipers were both on and on the rear only the driver side rear caliper was on with no fluid so not engaged, I checked. We preformed both tests with the tires on and in neutral.

I will begrudgingly note that only one of the 2 brakes pads on the driver rear side caliper are even touching the rotor and touch is an overstatement. I only add this because another party member who is as experianced as I am disagrees with me and feels that the brake pad is the reason it wont spin freely like the fronts. We would both prefer to not take this caliper off becuase it works and sucked both ways to take off and put on.

In addition to a visual inspection when we turn one wheel the other turns in the opposite direction unimpeded. To clarify, it doesnt spin any easier in one direction compared to the other, but I only reference this to show that if the caliper was in engaged slightly then I would think that the wheel with the caliper on it would have trouble turning through the dif compared to hands on.

Don't question the missing passenger side caliper. It's just where we stopped when we decided to test the wheel spin and noticed the discrepancy.

At any rate is that just the way it should be or should the rears travel close to the same as the fronts in a perfect world?

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MJM

Patrick SEP 04, 08:08 PM

Maybe I'm missing something here... but how can you compare the front wheels ability to spin freely with the rears, when the rears of course are attached to the transmission?
fieroguru SEP 04, 08:41 PM
Front should spin much easier than the rear.

For the front wheel to spin, you are spinning 1 wheel rotating 2 bearings.

For the rear wheel to spin, you have to spin 2 wheels, on 4 bearings, rotate 2 CVs (which if the car is jacked up will be at a significant angle), rotate 2 Tripots, and spin the spider gears in the differential. This is a lot more mass and frictional losses.
Doggo SEP 05, 07:57 PM

quote
Originally posted by Patrick:


Maybe I'm missing something here... but how can you compare the front wheels ability to spin freely with the rears, when the rears of course are attached to the transmission?



Oh yeah, hadn't really considered that to be a reason that could be happening...

And the rears should spin in opposite directions right?
Patrick SEP 05, 11:09 PM

quote
Originally posted by Doggo:

And the rears should spin in opposite directions right?



Back in the "old" days, one way of determining whether or not a rear differential was equipped with Posi-track (limited slip) gears was to spin a rear wheel when both rear wheels were off the ground. No posi resulted in the other wheel spinning in the opposite direction, whereas with a posi rear end, both wheels would spin in the same direction.

I therefore would suspect that with a factory transaxle, that the rear wheels of a Fiero would spin in opposite directions.
eimhear OCT 30, 04:19 AM
In general, the rear wheels should have a similar degree of free travel compared to the front wheels when the vehicle is lifted. However, the actual amount of travel might differ due to suspension design, the weight distribution of the vehicle, and the characteristics of the braking system. Since only the driver side rear caliper was engaged and without fluid, it’s important to note that this caliper will not apply any braking force, which means it shouldn’t restrict wheel bearings movement significantly. However, if one brake pad is not properly seated against the rotor, it can lead to uneven braking or restriction in rotation.

[This message has been edited by eimhear (edited 10-30-2024).]

82-T/A [At Work] OCT 30, 08:30 AM

quote
Originally posted by NuClearFuRy:

My question is how should the travel on the front wheels compare to the rear when up in the air.

We have an 85 Fiero and while changing both rear calipers we noticed that while up in the air the rear wheels don't travel very much. Removing the old calipers helped but not much. The rear wheels give maybe an inch or 2 of free travel after let go as compared to the front wheels that travel for seconds and take far longer to stop on their own. The front calipers were both on and on the rear only the driver side rear caliper was on with no fluid so not engaged, I checked. We preformed both tests with the tires on and in neutral.

I will begrudgingly note that only one of the 2 brakes pads on the driver rear side caliper are even touching the rotor and touch is an overstatement. I only add this because another party member who is as experianced as I am disagrees with me and feels that the brake pad is the reason it wont spin freely like the fronts. We would both prefer to not take this caliper off becuase it works and sucked both ways to take off and put on.

In addition to a visual inspection when we turn one wheel the other turns in the opposite direction unimpeded. To clarify, it doesnt spin any easier in one direction compared to the other, but I only reference this to show that if the caliper was in engaged slightly then I would think that the wheel with the caliper on it would have trouble turning through the dif compared to hands on.

Don't question the missing passenger side caliper. It's just where we stopped when we decided to test the wheel spin and noticed the discrepancy.

At any rate is that just the way it should be or should the rears travel close to the same as the fronts in a perfect world?




Front wheels are not affixed to anything, so you're literally riding on two bearing surfaces on the steering knuckle. A good set of bearings, and the wheels should make ideally two full rotations.

The rear wheels are connected to the transmission, and have not only a wheel hub, but seals both at the steering knuckle, at the transmission, and also connects to the differential (at all times) which also sits on bearings. And... the other side of that differential is connected to the other axle... etc... and the other wheel.

I don't think I've taken notice, but in an automatic, when you're in park and you spin one rear wheel, the other wheel spins with it in the opposite direction.

So this is totally normal.