Rear vibration ...need help,suggestions

[Hart_Rod]

I've been chasing a rear vibration, well really more like a hop. It feels like the truck starts bouncing up and down around 40-45 MPH (at least that's where it seems the worse). I've checked everything from wheel balance, changed out the poly cab mounts to rubber, put on a different set of wheels and tires, new driveshaft, made sure the the rear pinion angle was good, installed the correct length of tuned shocks, made sure the axle bearings were good, and then finally I thought I had it narrowed down to a bent rear axle... So I ordered some new axles and swapped them out thinking I had finally fixed the problem. Took it for a test drive, but the hop didn't go away....

So I started looking at the hub where the wheels go on the axle. With the car on jack stands and running you can see wheel hub is off centered which is causing the up and down bounce. It appears that my Billet Specialty wheels aren't centering up when I bolt them on. I think this is happening because the thickness of the CPP rear rotor. They don't allow the axle hub stick far enough past the rotor to engage the wheel hole, thus preventing them from centering up. I'm not sure what the best option is at this point. New axles with thicker hub? Change rear brakes to Wilwood or something else with a thinner hub? I don't want to keep throwing money at this problem unless I have a good possibility of correcting the problem. Very frustrated. Suggestions and comments appreciated.

[88fordf150]

Its a long shot but measure the axle hub flange that your rotor slides over and the center hole on your wheel to see if they are a fit.

[Hart_Rod]

Originally Posted by 88fordf150

Its a long shot but measure the axle hub flange that your rotor slides over and the center hole on your wheel to see if they are a fit.

It does, but because of the thickness of the rotor it never engages the wheel hub. I'm just not sure of which way to proceed from here...

[88fordf150]

Might try calling Cpp to see if they have any suggestion. Maybe a rotor swap?

[mechanicalman]

Originally Posted by Hart_Rod

I've been chasing a rear vibration/hop for while now. It feels like the truck starts bouncing up and down around 40-45 MPH (at least that's where it seems the worse). I've checked everything from wheel balance, changed out the poly cab mounts to rubber, put on a different set of wheels and tires, made sure the the rear pinion angle was good, installed the correct length of tuned shocks, made sure the axle bearings were good, and then finally I thought I had it narrowed down to a bent rear axle... So I ordered some new axles and swapped them out thinking I had finally fixed the problem. Took it for a test drive, but the vibration didn't go away....

So I started looking at the hub where the wheels go on the axle. With the car on jack stands and running you can see wheel hub is off centered which is causing the up and down bounce. It appears that my Billet Specialty wheels aren't centering up when I bolt them on. I think this is happening because the thickness of the CPP rear rotor. They don't allow the axle hub stick far enough past the rotor to engage the wheel hole, thus preventing them from centering up. I'm not sure what the best option is at this point. New axles with thicker hub? Change rear brakes to Wilwood or something else with a thinner hub? I don't want to keep throwing money at this problem unless I have a good possibility of correcting the problem. Very frustrated. Suggestions and comments appreciated.

Is the center of the wheel the right size compared to the size of the hub? If the wheel center is bigger than the hub, try some "hub centric" adaptors of the appropriate size.

If you cannot establish hub centricity, you are stuck with "lug centricity". So, carefully jack up your wheels one at a time and loosen all the lug nuts. Screw them back down with your fingers all the time wobble and rotate the wheel until all the lug nuts are seated all the way down then take a lug wrench and slowly snug the lugs down in a pattern in several increments then make the final torque with a torque wrench. I have a vehicle that has this problem; nobody makes hub-centric adaptors for my hub/wheel combination.

I was having same problem, service manager at Chevy said to try "road force" application while wheels being spin balanced. Tech took off one wheel and said I needed hub centric adaptors and did not want to waste my money on balancing. When I left the dealer, the problem was actually worse and the steering wheel more off-center that it was before. So that got me thinking, what could he have done to make it worse? It was the air impact wrench that severely over-torqued the wheel. I used the above torque procedure and it's smooth as silk now and steering wheel back on center, as hard as that is to believe. I don't see how that could happen but it did the same thing when I had a flat fixed and tires rotated I had to perform the procedure again. They are alloy wheels.

[67 chevelle]

driveshaft ,,, ujoints ,,, tailshaft bearing ,,, lose ubolts on differential ,,, bad shocks ,,,pinion bearing ,, just a few suspects .. I chased this same thing for a couple years on a chevelle ,, turned out to be bad shocks

[72MARIO]

Are you 100% sure that your rear brakes are not dragging ?

I would bring the truck in after driving for a while jack it up and check to make sure they spin freely. That's what my problem was. I had a new caliper sticking. I replaced driveshaft shocks had new wheels rebalanced drums and rotors turned tranny and engine mounts replaced also did front ball joints. just to find out it was a caliper.

[sprint_9]

http://www.hubcentric-rings.com/why_hub_centric_rings/

Would something like this work?

I had a similar problem, tried these and they did help. Turned out my main problem was my tires not being balanced properly. Have you had the balance checked at more than one shop?

[TBONE1964]

"They don't allow the axle hub stick far enough past the rotor to engage the wheel hole, thus preventing them from centering up"

This sounds like your problem to me. You either need a thicker axle hub flange or a thinner rotor hat. Also the diameter of the axle hub and the center hole in the wheel need to be the same.

If there is not enough hub sticking out past the rotor hat, then it does not matter what kind of adapter you use, it will not have anything to center against.

The alternative is to use wheels that are designed to use tapered seat lugs and will have a tapered seat for the lug nut to seat against. This will/should center the wheel on the lug studs and not rely on the hub.

Good luck,
Tom

[lolife99]

Have you talked to Delmo?
He uses CPP for all of his Dropmember builds.
I can't believe this is a wide spread CPP problem, since there are so many kits out there.
It's got to be a QC issue with the part you have.

[stsalvage]

I know a lot of people want the best of every thing But there is nothing wrong with drum brakes.

This old tail of,If Its not broken don't fit it you have spend well over 1200.00 trying to chase this problem down and your not one step closer to enjoying your ride.

What was the whole perpus of having your truck/suburban spend a life time working on it or enjoying it.

Here is a story of a friend of mine that has more money then 3/4 of the people on here.

This guy i know.

He has had this quest to build a car that would have unbelievable power but get grate gas mileage

This guy co sponsored Dick Trickal during the last of his racing currier Then he did some fine tuning to Bonneville salt flats.

He built a 1970 nova with a 502 engine 750 hp with a 400th with a gear vender with a 410 gear He's put over 129,000 in to this car Just so this car can be smooth at 120 mph

Car is wicked stop on a dime.

when i was in AZ at one of his testing shops I saw the car up on a lift rear end was out he has 8 different axles 4 rear end gears on a table and boxes of brakes.

He was talking to his builder saying that the car has a rattle in the rear end Guy tells him he's had that rear end out 6 different times changed it 3 different times.His builder even put in a quick change rear end and the rattle it still there.

I know we all have had bosses some point in are life's that where ass holes.Ben said to the builder its in the rear end find it or your Gone.

Jake his builder came out I've know Jake sense 1987 Baha 1000 worked on Timmy Pruett Ford F150 Baha truck for Ford Racing.

He tells me its not a good time so he starts fitting the rear end I ask him why don't you just put the stock rear end back in and go from there.Any high skill Builder dose not want to be showed up.I tell him its your ID then i went over and looked at one of the stock car's they had in the shop.

you know he found the problem it was not the rear end at all it had something to with the shocks and the sway bar.

The hole meaning if you want to rebuild the whole truck and spend over 200K fine if you want a truck to enjoy leave it simple.

We all take it to far to improve the driving and handling of these trucks when GM did a perfect job all along

[Fitz]

Originally Posted by Hart_Rod

I've been chasing a rear vibration/hop for while now. It feels like the truck starts bouncing up and down around 40-45 MPH (at least that's where it seems the worse).

So I started looking at the hub where the wheels go on the axle. With the car on jack stands and running you can see wheel hub is off centered which is causing the up and down bounce. It appears that my Billet Specialty wheels aren't centering up when I bolt them on. I think this is happening because the thickness of the CPP rear rotor. They don't allow the axle hub stick far enough past the rotor to engage the wheel hole, thus preventing them from centering up. I'm not sure what the best option is at this point. New axles with thicker hub? Change rear brakes to Wilwood or something else with a thinner hub? I don't want to keep throwing money at this problem unless I have a good possibility of correcting the problem. Very frustrated. Suggestions and comments appreciated.

Call the CPP tech line. 378 E Orangethorpe Ave., Placentia CA 92870 Tech Line 714-522-2000

[faribran]

Rob, did you determine what was causing this?

[Hart_Rod]

Thanks for all the post guys. Sorry for the slow response but I've been down hard with the flu for the last 4 days. My fever finally broke last night, so I'm feeling a little better today.

Originally Posted by 88fordf150

Its a long shot but measure the axle hub flange that your rotor slides over and the center hole on your wheel to see if they are a fit.

They fit but rotor thickness prevents engagement.

Originally Posted by 88fordf150

Might try calling Cpp to see if they have any suggestion. Maybe a rotor swap?

I'll give that a try. I know Wilwoods rotor hats are about half the thickness.

Originally Posted by mechanicalman

Is the center of the wheel the right size compared to the size of the hub? If the wheel center is bigger than the hub, try some "hub centric" adaptors of the appropriate size.

If you cannot establish hub centricity, you are stuck with "lug centricity". So, carefully jack up your wheels one at a time and loosen all the lug nuts. Screw them back down with your fingers all the time wobble and rotate the wheel until all the lug nuts are seated all the way down then take a lug wrench and slowly snug the lugs down in a pattern in several increments then make the final torque with a torque wrench. I have a vehicle that has this problem; nobody makes hub-centric adaptors for my hub/wheel combination.

I was having same problem, service manager at Chevy said to try "road force" application while wheels being spin balanced. Tech took off one wheel and said I needed hub centric adaptors and did not want to waste my money on balancing. When I left the dealer, the problem was actually worse and the steering wheel more off-center that it was before. So that got me thinking, what could he have done to make it worse? It was the air impact wrench that severely over-torqued the wheel. I used the above torque procedure and it's smooth as silk now and steering wheel back on center, as hard as that is to believe. I don't see how that could happen but it did the same thing when I had a flat fixed and tires rotated I had to perform the procedure again. They are alloy wheels.

Thanks for the info. I always that procedure when I bolt my wheels on.

Originally Posted by 67 chevelle

driveshaft ,,, ujoints ,,, tailshaft bearing ,,, lose ubolts on differential ,,, bad shocks ,,,pinion bearing ,, just a few suspects .. I chased this same thing for a couple years on a chevelle ,, turned out to be bad shocks

I just spent almost $700 on Ridetech adjustable shocks and still have the same problem...

Originally Posted by 72MARIO

Are you 100% sure that your rear brakes are not dragging ?

I would bring the truck in after driving for a while jack it up and check to make sure they spin freely. That's what my problem was. I had a new caliper sticking. I replaced driveshaft shocks had new wheels rebalanced drums and rotors turned tranny and engine mounts replaced also did front ball joints. just to find out it was a caliper.

Checked that.

Originally Posted by sprint_9

http://www.hubcentric-rings.com/why_hub_centric_rings/

Would something like this work?

I had a similar problem, tried these and they did help. Turned out my main problem was my tires not being balanced properly. Have you had the balance checked at more than one shop?

Originally Posted by TBONE1964

"They don't allow the axle hub stick far enough past the rotor to engage the wheel hole, thus preventing them from centering up"

This sounds like your problem to me. You either need a thicker axle hub flange or a thinner rotor hat. Also the diameter of the axle hub and the center hole in the wheel need to be the same.

If there is not enough hub sticking out past the rotor hat, then it does not matter what kind of adapter you use, it will not have anything to center against.

The alternative is to use wheels that are designed to use tapered seat lugs and will have a tapered seat for the lug nut to seat against. This will/should center the wheel on the lug studs and not rely on the hub.

Good luck,
Tom

Thanks Tom. I think that is going to be my 2 best choices. Funny thing is, my wheels are designed for tapered lugs and that's what I'm using. But still no go.....

Originally Posted by Fitz

Call the CPP tech line. 378 E Orangethorpe Ave., Placentia CA 92870 Tech Line 714-522-2000

I'll give that a try.

Originally Posted by lolife99

Have you talked to Delmo?
He uses CPP for all of his Dropmember builds.
I can't believe this is a wide spread CPP problem, since there are so many kits out there.
It's got to be a QC issue with the part you have.

Not yet. On my to do list.

Originally Posted by faribran

Rob, did you determine what was causing this?

I think I know what's causing it, but due to illness, I haven't been able to try a few things to verify my it.

[lolife99]

It would be nice to chuck up an axle in a lathe and get some run out readings on the rear rotors.
Something isn't concentric here.

[Hart_Rod]

Originally Posted by lolife99

It would be nice to chuck up an axle in a lathe and get some run out readings on the rear rotors.
Something isn't concentric here.

Agreed. That's the only thing I haven't swapped out. I have another pair of rotors that I can put on there when I start feeling better.

[TBONE1964]

Originally Posted by Hart_Rod

Agreed. That's the only thing I haven't swapped out. I have another pair of rotors that I can put on there when I start feeling better.

If you have or can borrow a dial indicator with a stand, you can do this yourself. You will want to do a run out on the axle flange pilot itself without the rotor. You may have to drive the lug studs out to get a good position with the dial indicator.

Have you rotated front to rear and has it made any difference? Going back to your original problem that there is not enough axle flange pilot sticking out beyond the rotor hat to center the wheel, I think you need to correct this problem or you are just chasing ideas that may or may not work.

You can also check the wheels for run out by using the front rotors as a fixed position and see if your rims have excessive run out.

You would not believe what .020 does to a steer tire/wheel on a semi.

I am now curious to what fixes this problem you have.

By the way, I hope you get well soon.

Keep us posted,
Tom

[88Ironduke]

If its a rim fitment issue could you get a set of stockers/suitable substitute or something else to test drive on? I have zero experience in the bolt on goodies you have, but if possible try to remove the problem rims from the equation and test drive before throwing more money at a problem. That isolates out one element and then you know for sure the problem/issue before buying more parts.

88Ironduke

[mechanicalman]

Originally Posted by 88Ironduke

If its a rim fitment issue could you get a set of stockers/suitable substitute or something else to test drive on? I have zero experience in the bolt on goodies you have, but if possible try to remove the problem rims from the equation and test drive before throwing more money at a problem. That isolates out one element and then you know for sure the problem/issue before buying more parts.

88Ironduke

What he said....VERY good idea to find rims with a more abrupt hub center to be sure of the problem without excessive wrenching.

I suggested a careful mounting of the lugs with a gradual torqueing of the lugs (he says he has tapered lugs) with the final torque being with a torque wrench but not sure if he has tried it.

Lug-centricity is a very delicate thing and you have to put the wheels on really carefully. Ask me how I know LOL

[Andy4639]

I sorry to ask this but the disc should let the wheel come into contact of the hub should it not. If the wheel isn't on the hub then the only thing holding the wheel right is the 5 lugs which are not made for this kind of stress.
I would look at the bracketery for the disc brakes and see if there is something binding it up to keep it off of the hub.
This is a good read for you.

The studs are not to carry the weight of the vehicle. The hub does this.This is why you want a tight fitting wheel.


http://bernardembden.com/xjs/hubcentric/

[Hart_Rod]

Originally Posted by lolife99

It would be nice to chuck up an axle in a lathe and get some run out readings on the rear rotors.
Something isn't concentric here.

Keith - I had the new axles checked before I put them in and all was good. I then had the other axles checked after I swapped in the new ones, they checked good also.

Originally Posted by TBONE1964

If you have or can borrow a dial indicator with a stand, you can do this yourself. You will want to do a run out on the axle flange pilot itself without the rotor. You may have to drive the lug studs out to get a good position with the dial indicator.

Have you rotated front to rear and has it made any difference? Going back to your original problem that there is not enough axle flange pilot sticking out beyond the rotor hat to center the wheel, I think you need to correct this problem or you are just chasing ideas that may or may not work.

You can also check the wheels for run out by using the front rotors as a fixed position and see if your rims have excessive run out.

You would not believe what .020 does to a steer tire/wheel on a semi.

I am now curious to what fixes this problem you have.

By the way, I hope you get well soon.

Keep us posted,
Tom

Thanks, feeling better today. I have had both old and new axles checked, and they checked good. I will try to check the axle flange pilot with the truck in gear to see how it looks.

Originally Posted by 88Ironduke

If its a rim fitment issue could you get a set of stockers/suitable substitute or something else to test drive on? I have zero experience in the bolt on goodies you have, but if possible try to remove the problem rims from the equation and test drive before throwing more money at a problem. That isolates out one element and then you know for sure the problem/issue before buying more parts.

88Ironduke

I tried 2 different sets of billet wheels with the same results, but I need to find a set of steel wheels and see if there is a difference.

Originally Posted by mechanicalman

What he said....VERY good idea to find rims with a more abrupt hub center to be sure of the problem without excessive wrenching.

I suggested a careful mounting of the lugs with a gradual torqueing of the lugs (he says he has tapered lugs) with the final torque being with a torque wrench but not sure if he has tried it.

Lug-centricity is a very delicate thing and you have to put the wheels on really carefully. Ask me how I know LOL

I spoke to Billet Specialties and they confirmed that all of their wheels are "lug-centric", which means that it shouldn't matter if the axle hub makes contact with the wheel center.

Originally Posted by Andy4639

I sorry to ask this but the disc should let the wheel come into contact of the hub should it not. If the wheel isn't on the hub then the only thing holding the wheel right is the 5 lugs which are not made for this kind of stress.
I would look at the bracketery for the disc brakes and see if there is something binding it up to keep it off of the hub.
This is a good read for you.

The studs are not to carry the weight of the vehicle. The hub does this.This is why you want a tight fitting wheel.


http://bernardembden.com/xjs/hubcentric/

Andy, it depends on the type of wheel. Billet Specialties told me nearly all billet wheels are "lug-centric", unlike most OEM wheels which are "hub-centric"

[mechanicalman]

Originally Posted by Andy4639

I sorry to ask this but the disc should let the wheel come into contact of the hub should it not. If the wheel isn't on the hub then the only thing holding the wheel right is the 5 lugs which are not made for this kind of stress.
I would look at the bracketery for the disc brakes and see if there is something binding it up to keep it off of the hub.
This is a good read for you.

The studs are not to carry the weight of the vehicle. The hub does this.This is why you want a tight fitting wheel.


http://bernardembden.com/xjs/hubcentric/

I would not read anything into this link to this website. This is not a manufacturer, just an end user voicing his opinion on his page of the Jaguar Lover's website. He takes good pictures, and he qualifies his statements in a manner of little refute. For instance "do maintain load bearing at the hub" but does not say how much of that load. And, the lug bolts actually maintain load bearing at the hub also as does the entire wheel that is bolted to the hub. He does not say what part of the hub specifically (i.e. "hub shoulder"). I realize some will say that the shoulder is the hub, and technically they are not wrong as the definition is ambiguous. I'm operating on the premise that the hub is the entire area the wheel bolts onto so I cannot say the writer is assuming one or the other so what he is saying is without precise meaning.
http://dictionary.reference.com/browse/hub

For instance, in some cases in order to get wheel bearings you have to replace the entire hub assembly.

One has to be careful when printing things like this as there is always someone who will go over it with a microscope and try to find a flaw, and this man is good at saying things that are, again, without precise meaning. And, he said "My conclusion". Simply his conclusion.

I do, however, believe it's his intention for the reader to make his own conclusions. He's a fairly good writer.

"My conclusion: Hubcentric adapters, when designed and manufactured properly to fit a specific wheel, do maintain load bearing at the hub. As illustrated in another link in my website I currently have these wheels and hubcentric adapters on my automobile".

"Re-installing the hubcentric adapter on the wheel revealed that there was no lateral movement between the adapter and the wheel. This is important, because Ronal claims that these adapters are hubcentric to the wheel, i.e. an integral part of the wheel".
http://bernardembden.com/xjs/hubcentric/index.htm

So really, Ronal (assumed adaptor manufacturer) claims these adaptors are "hubcentric". "i.e." or "id est" means the writer is responding to a question that has not been asked yet and he is presuming to tell us that the adaptor is an integral part of the wheel in lieu of Ronal not saying that. He did not say that Ronal claims that the adaptor is an integral part of the wheel, only that it's "hubcentric" (i.e. hub centric).

As a matter of fact, most hub centric rings are made of plastic. I assume it's good plastic.

https://www.google.com/search?q=plas...+centric+rings

My conclusion: On wheels with tapered lug nuts, 99% of the load is on the lug bolts/nuts with that load divided between rotational force imparted on the lug bolts/nuts vs the clamping force of the lug bolts/nuts holding the wheel to the hub resulting in the friction between the wheel and the hub that takes part of the load including the weight of the vehicle; hub centricity is just hub centricity. Before you torque your lug nuts the wheel is always sitting on one side of the hub or the other with a gap of a couple thousandths or so run-out no matter how you slice it then it's close enough for the lug nuts to finish centering it. If you don't have reasonable hub centricity built in it will distort the wheels if you don't use extreme care getting it centered before you torque the lugs.

Measure the clearance between the wheel center and the hub before you torque the bolts, see the clearance on the bottom of .002" to .003". Then, after torque sequence, see about .001" to .0015" all the way around.

I'm not a manufacturer either, just an end user voicing his opinion.

[brad_man_72]

Sounds like you've checked everything but the driveshaft.... when's the last time it was checked for straightness and ballance? Is it in time?

[TBONE1964]

From the keyboard of the Original Poster

"I think this is happening because the thickness of the CPP rear rotor. They don't allow the axle hub stick far enough past the rotor to engage the wheel hole, thus preventing them from centering up."

Maybe I am not thinking about this the right way but wouldn't you need to have some axle hub pilot sticking out past the rotor hat for the hubsentric to center on? The hubcentrics are if I am thinking correctly designed to make up the difference between the axle hub pilot diameter and the hole in the center of the wheel.

If the wheel of choice is designed as a hub piloted wheel, then it needs to have enough pilot thickness on the axle to engage into the wheel.

[Hart_Rod]

Originally Posted by brad_man_72

Sounds like you've checked everything but the driveshaft.... when's the last time it was checked for straightness and ballance? Is it in time?

It's a brand new 3.5" aluminum DSS driveshaft that's rated for a 1000+ HP. It's not a vibration in the drivetrain, it feels more like a "hop" in the rear end.

Originally Posted by TBONE1964

From the keyboard of the Original Poster

"I think this is happening because the thickness of the CPP rear rotor. They don't allow the axle hub stick far enough past the rotor to engage the wheel hole, thus preventing them from centering up."

Maybe I am not thinking about this the right way but wouldn't you need to have some axle hub pilot sticking out past the rotor hat for the hubsentric to center on? The hubcentrics are if I am thinking correctly designed to make up the difference between the axle hub pilot diameter and the hole in the center of the wheel.

If the wheel of choice is designed as a hub piloted wheel, then it needs to have enough pilot thickness on the axle to engage into the wheel.

I spoke to Billet Specialties and they said all of their wheels as well as most aftermarket wheels are "lug-centric", so the axle flange engagement shouldn't be an issue. Last night, I replaced the rear rotors with some new ones. I then spent about 10 minutes on each wheel bolting them on. When I get home from work today I'll take it for a test drive and see if anything changes.