Trailing Arm 101: Spindle Endplay
03-14-2015, 03:39 PM
#1
Safety Car
Thread Starter
Trailing Arm 101: Spindle Endplay
Hey guys.
I am rebuilding my trailing arms, and got everything together and took my bearings and spindle housings etc etc over to my buddies place where he showed me how to set up the bearings on the spindle tool.
I am looking in the 1967 Chassis Service manual, and the GM books says that the end play with the set up should be between 0.001 and 0.008.
I had a huge variety of shims, so I had some fun trying various ones out in my set up.
We set up the dial indicator and we got everything from "0" end play, all the way out to 0.013.
To me, the "feel" of difference of .001 and .008 was huge.
Am I correct in thinking that, on the Trailing arm assembly line circa 1966-67, a Trailing arm whose spindle end play proved to be .008, would have made it onto a car?
I have done a LOT of reading on line over the last few weeks and it seems to me that the holy grail of end play is ".001"
So my question is, if .008 was ok for GM... why so much emphasis on .001? What is .001 going to give me that .004 won't, or .006 won't?
I am not trying to wag my finger, I am genuinely curious as to what the difference is, and how that relates to how the car drives.
I already feel that I can't be in the cool club anymore because I have a NOM, is there a lower order in Vette-dom for folks whose spindle endplay is .004?
Thanks, in advance for the education.
I am rebuilding my trailing arms, and got everything together and took my bearings and spindle housings etc etc over to my buddies place where he showed me how to set up the bearings on the spindle tool.
I am looking in the 1967 Chassis Service manual, and the GM books says that the end play with the set up should be between 0.001 and 0.008.
I had a huge variety of shims, so I had some fun trying various ones out in my set up.
We set up the dial indicator and we got everything from "0" end play, all the way out to 0.013.
To me, the "feel" of difference of .001 and .008 was huge.
Am I correct in thinking that, on the Trailing arm assembly line circa 1966-67, a Trailing arm whose spindle end play proved to be .008, would have made it onto a car?
I have done a LOT of reading on line over the last few weeks and it seems to me that the holy grail of end play is ".001"
So my question is, if .008 was ok for GM... why so much emphasis on .001? What is .001 going to give me that .004 won't, or .006 won't?
I am not trying to wag my finger, I am genuinely curious as to what the difference is, and how that relates to how the car drives.
I already feel that I can't be in the cool club anymore because I have a NOM, is there a lower order in Vette-dom for folks whose spindle endplay is .004?
Thanks, in advance for the education.
03-14-2015, 05:44 PM
#3
Race Director
I do not set up rear wheel bearing to the high side of GM specs. I prefer to get them from .001'' to .003" MAX!
Reason being....the brake calipers if your Corvette is a disc brake car. The less run-out I set it at...and then when checking the brake rotor also...I want to try to make the surface of the brake rotor be as TRUE as possible....so when the car is rolling down the road...the rotors are not moving in and out due to excessive wheel bearing run-out and the rotor not be trued to the system. The more run-out your have in your rear wheel bearing...the more the rotor can move...and if you rotor is not RIGHT...that adds to the PROBLEM in the brakes failing....either by sucking in air or leaking fluid due to the four pistons on each caliper are now being actuated by the spindle/rotors turning.
The brake system of your Corvette is basically back @sswards from a majority of other brake systems used. NOT writing that it is bad...but it is different. Due to the caliper being SOLIDLY MOUNTED to the suspension...it can not move or float...like many other brake systems allow....so having your bearings and rotors be CORRECT is a big deal. AND I am not a fan of the 'O' ring style calipers that are 'supposedly more forgiving' and take the problems in your bearings being on the high side of specs and such and make it so the calipers will works if things are off....and will not leak...so they say....and the 'O' ring style is so if your car sits for extended periods of time...the lip seals will not stick and the first time you press your brake pedal after long winter storage...your calipers leak. That is why I tell my customers...ALWAYS crank and run your Corvette as least ONCE a month..
DUB
Reason being....the brake calipers if your Corvette is a disc brake car. The less run-out I set it at...and then when checking the brake rotor also...I want to try to make the surface of the brake rotor be as TRUE as possible....so when the car is rolling down the road...the rotors are not moving in and out due to excessive wheel bearing run-out and the rotor not be trued to the system. The more run-out your have in your rear wheel bearing...the more the rotor can move...and if you rotor is not RIGHT...that adds to the PROBLEM in the brakes failing....either by sucking in air or leaking fluid due to the four pistons on each caliper are now being actuated by the spindle/rotors turning.
The brake system of your Corvette is basically back @sswards from a majority of other brake systems used. NOT writing that it is bad...but it is different. Due to the caliper being SOLIDLY MOUNTED to the suspension...it can not move or float...like many other brake systems allow....so having your bearings and rotors be CORRECT is a big deal. AND I am not a fan of the 'O' ring style calipers that are 'supposedly more forgiving' and take the problems in your bearings being on the high side of specs and such and make it so the calipers will works if things are off....and will not leak...so they say....and the 'O' ring style is so if your car sits for extended periods of time...the lip seals will not stick and the first time you press your brake pedal after long winter storage...your calipers leak. That is why I tell my customers...ALWAYS crank and run your Corvette as least ONCE a month..
DUB
03-14-2015, 08:32 PM
#4
Le Mans Master
Agree partially/mostly with DUB. Set your endlay between .001 and .003. I do not subscribe to the rotor runout theory causing "sucking air" into the system. My personal opinion is that if rotor runout is "extreme" the pulsation of the pistons in the calipers causes the brake fluid to boil, thereby intoducing air into the system. Not air bypassing the seals on the pistons.
I have owned disc brake equipped Corvettes in the C2, C3, C4 and C5 series cars. I have never had the "sucking air" into the system syndrome on any of the cars and I have never shimmed a rotor to "correct" rotor runout on any of the vehicles. All of the cars have been subjected to low speed auto cross (considered as less than 70 mph although that threshold has been exceeded) and no braking system issues. Some of these vehicles have been converted from drum brake to disc brake systems and not had the rotors riveted to the hubs and machined as an assembly yet no issues. I can't just be lucky.
I have owned disc brake equipped Corvettes in the C2, C3, C4 and C5 series cars. I have never had the "sucking air" into the system syndrome on any of the cars and I have never shimmed a rotor to "correct" rotor runout on any of the vehicles. All of the cars have been subjected to low speed auto cross (considered as less than 70 mph although that threshold has been exceeded) and no braking system issues. Some of these vehicles have been converted from drum brake to disc brake systems and not had the rotors riveted to the hubs and machined as an assembly yet no issues. I can't just be lucky.
03-14-2015, 08:35 PM
#5
Race Director
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I set mine as close to "0" as possible...no more than .001".
What you felt at .008" was a true thing...multiply that movement by about 13-14" from the centerline and see how much your wheels/tires are going to move around...up, down, forward and backward as it goes down the road.
Will the bearings live out there at .010+? Sure....but bearing folks are concerned for their bearings...not everything else that depends on them.
As mentioned by DUB...on a "normal" brake system with floating calipers...you actually need a little more clearance to allow for what is called "knockback" which will move the brake pads away from the rotor instead of sitting right on them.
JIM
What you felt at .008" was a true thing...multiply that movement by about 13-14" from the centerline and see how much your wheels/tires are going to move around...up, down, forward and backward as it goes down the road.
Will the bearings live out there at .010+? Sure....but bearing folks are concerned for their bearings...not everything else that depends on them.
As mentioned by DUB...on a "normal" brake system with floating calipers...you actually need a little more clearance to allow for what is called "knockback" which will move the brake pads away from the rotor instead of sitting right on them.
JIM
03-14-2015, 09:07 PM
#6
Drifting
End play
As mentioned above, .008 is way too much. I used to set them up from .001-.003, but about 2 years ago I had a problem with one spindle I set up at .001. It made noise. I had to warranty it and had to put a new spindle in it. I could not find any issues with any of the parts. I have since modified my target play to .002-.003 and no issues. Its just my personal opinion.
Boyan
Boyan
03-14-2015, 10:18 PM
#7
Burning Brakes
I agree that .007 is a pretty big spread, but I think either too tight or too loose is bad in my opinion. I was shooting for .002 and wound up with .003 and I was comfortable with that. I had researched it a bit before I started and I'd heard from a few sources that once they are assembled they generally end up about .001 tighter than with the setup tool, but I did not experience this - I had .003 with the tool, and came up with .003 when I rechecked after they were assembled and pressed together.
03-15-2015, 04:01 AM
#8
Safety Car
Thread Starter
Thanks for the responses guys...
The fog of endplay is starting to lift... I am curious though, why did GM think it was ok to send TAs out the door with .008 endplay?
The fog of endplay is starting to lift... I am curious though, why did GM think it was ok to send TAs out the door with .008 endplay?
03-15-2015, 09:31 AM
#9
Burning Brakes
I look at it this way - on the front wheel bearings on these (and millions of other cars) we just tighten them by feel and never even check the end play so who knows how much it varies from car to car, yet they're pretty reliable and trouble free. We all want our stuff as close to perfect as possible on our beloved cars but in reality it's probably not that critical.
03-15-2015, 09:40 AM
#10
Le Mans Master
I look at it this way - on the front wheel bearings on these (and millions of other cars) we just tighten them by feel and never even check the end play so who knows how much it varies from car to car, yet they're pretty reliable and trouble free. We all want our stuff as close to perfect as possible on our beloved cars but in reality it's probably not that critical.
03-15-2015, 09:55 AM
#11
Burning Brakes
Oh I know it exists! I just meant that these cars have the same front bearing setup as almost every other car made in those decades and probably 99% were tightened by feel and various methods and still remained pretty reliable. I'm not saying sloppy tolerances are good or it doesn't matter, just that it's probably a little more forgiving than we think.
03-15-2015, 11:45 AM
#12
Le Mans Master
I
Oh I know it exists! I just meant that these cars have the same front bearing setup as almost every other car made in those decades and probably 99% were tightened by feel and various methods and still remained pretty reliable. I'm not saying sloppy tolerances are good or it doesn't matter, just that it's probably a little more forgiving than we think.
Oh I know it exists! I just meant that these cars have the same front bearing setup as almost every other car made in those decades and probably 99% were tightened by feel and various methods and still remained pretty reliable. I'm not saying sloppy tolerances are good or it doesn't matter, just that it's probably a little more forgiving than we think.
03-15-2015, 01:04 PM
#13
Team Owner
Whoa!
First i have never used one of those tools, but I would hope the runout is being checked on a real world spindle being actually installed and not just based on a tool that isn't the actual spindle that I would think gets you just in tolerance based on potential spindle variations. No tool like that would be so percise for all the worlds spindles. PS I set mine also at .002-.003. I always consider the disc brakes as a separate techical puzzle and have trued (machined) the spindle surface, the rotor and if you go to non-stock components like Coleman Racing, you can make the rotors floating units!!!!!!!
Also on this forum, I probably should stop giving away performance secrets!
Also on this forum, I probably should stop giving away performance secrets!
Last edited by TCracingCA; 03-15-2015 at 08:45 PM.
03-15-2015, 04:27 PM
#14
Race Director
03-15-2015, 07:13 PM
#15
Race Director
I will write this for those who feel that the text in the manual dealing with rotor run-out is a bunch of nonsense. You can 'take it...or leave it'.
I recently had Corvette (77 I believe)...that when he had the brakes bled at other shops on several occasions and had a very good pedal...he could do inner city driving and right at 200 miles his BRAKE light would light up and the pedal was loosing its 'good feel'.
Getting frustrated and sick and tired of the same problem occurring like 'clock work'. He brought it to me and I used my measuring equipment and serviced one rear wheel bearing and got the rotor corrected because it was at .020". Since this service....he has gotten more well than 2000 miles on it and NO loss of pedal pressure and brake feel.
SO...I am sorry...for me it makes a difference. Everyone else can do as they wish.
And I am having a hard time wrapping my head around the brake fluid boiling theory. I have had only one Corvette that has come to my shop and the front brake hoses literally popped off due to the fluid was boiling and it was an 86. I have ridden with an owner or two who drove their Corvettes hard and when we get back to the shop the brakes are hot and never had a problem.
For what it is worth... comparing a factory brake system that was made AFTER a 1982 is pointless....they are designed completely different. Hub/bearing assemblies and calipers that ride on dowel pins are not the same.
DUB
I recently had Corvette (77 I believe)...that when he had the brakes bled at other shops on several occasions and had a very good pedal...he could do inner city driving and right at 200 miles his BRAKE light would light up and the pedal was loosing its 'good feel'.
Getting frustrated and sick and tired of the same problem occurring like 'clock work'. He brought it to me and I used my measuring equipment and serviced one rear wheel bearing and got the rotor corrected because it was at .020". Since this service....he has gotten more well than 2000 miles on it and NO loss of pedal pressure and brake feel.
SO...I am sorry...for me it makes a difference. Everyone else can do as they wish.
And I am having a hard time wrapping my head around the brake fluid boiling theory. I have had only one Corvette that has come to my shop and the front brake hoses literally popped off due to the fluid was boiling and it was an 86. I have ridden with an owner or two who drove their Corvettes hard and when we get back to the shop the brakes are hot and never had a problem.
For what it is worth... comparing a factory brake system that was made AFTER a 1982 is pointless....they are designed completely different. Hub/bearing assemblies and calipers that ride on dowel pins are not the same.
DUB
03-15-2015, 08:06 PM
#16
Le Mans Master
DUB:
I respect your knowledge and I don't attempt to change your position. Just think of it this way. The four pistons are sitting in the caliper bores with springs pushing them toward the pad. The rotor, if not running true, is pushing the pad and the four pistons back toward the caliper as it rotates. The pulsation of the pistons moves the brake fluid rapidly within the caliper. Not a lot of fluid reservoir there and, in my theory, creates heat. The fluid boils and bubbles of air are created and trapped.
Other theory (more commonly presented) is that as the pistons travel in their caliper bores threy suck air into the system. If air can pass in brake fluid can pass out. The people reporting air being sucked in are not experiencing brake fluid leaking out.
The rotor runout doesn't change in either scenario. The cause of the air in the system is considered differently.
Rich
I respect your knowledge and I don't attempt to change your position. Just think of it this way. The four pistons are sitting in the caliper bores with springs pushing them toward the pad. The rotor, if not running true, is pushing the pad and the four pistons back toward the caliper as it rotates. The pulsation of the pistons moves the brake fluid rapidly within the caliper. Not a lot of fluid reservoir there and, in my theory, creates heat. The fluid boils and bubbles of air are created and trapped.
Other theory (more commonly presented) is that as the pistons travel in their caliper bores threy suck air into the system. If air can pass in brake fluid can pass out. The people reporting air being sucked in are not experiencing brake fluid leaking out.
The rotor runout doesn't change in either scenario. The cause of the air in the system is considered differently.
Rich
03-15-2015, 08:36 PM
#17
Team Owner
03-16-2015, 02:36 AM
#18
Safety Car
Thread Starter
To turn the battle ship back nearer its original destination...
Spindle Endplay and rotor run out are two different issues... no?
They work in conjunction to make your day a lot worse... but we have a spec for the spindle end play .0001 -.008. If there is a "spec" for Rotor run out... I haven't seen it.
My original post was aimed at that .001-.008 spec. "I" feel, that most of what you find on the net/forums makes me think that IF my spindle end play was at .008, it would be time for a trailing arm rebuild.... yet the GM info of the time, says that .008 is in spec.
Spindle Endplay and rotor run out are two different issues... no?
They work in conjunction to make your day a lot worse... but we have a spec for the spindle end play .0001 -.008. If there is a "spec" for Rotor run out... I haven't seen it.
My original post was aimed at that .001-.008 spec. "I" feel, that most of what you find on the net/forums makes me think that IF my spindle end play was at .008, it would be time for a trailing arm rebuild.... yet the GM info of the time, says that .008 is in spec.
Last edited by Revfan; 03-16-2015 at 03:00 AM.
03-16-2015, 09:11 AM
#19
Le Mans Master
To turn the battle ship back nearer its original destination...
Spindle Endplay and rotor run out are two different issues... no?
They work in conjunction to make your day a lot worse... but we have a spec for the spindle end play .0001 -.008. If there is a "spec" for Rotor run out... I haven't seen it.
My original post was aimed at that .001-.008 spec. "I" feel, that most of what you find on the net/forums makes me think that IF my spindle end play was at .008, it would be time for a trailing arm rebuild.... yet the GM info of the time, says that .008 is in spec.
Spindle Endplay and rotor run out are two different issues... no?
They work in conjunction to make your day a lot worse... but we have a spec for the spindle end play .0001 -.008. If there is a "spec" for Rotor run out... I haven't seen it.
My original post was aimed at that .001-.008 spec. "I" feel, that most of what you find on the net/forums makes me think that IF my spindle end play was at .008, it would be time for a trailing arm rebuild.... yet the GM info of the time, says that .008 is in spec.
