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Discussion Starter #1
I am installing a bunch of Alfaholics goodies including an alloy T-bar on a 67 GTV and once everything was done and the car was down on it's wheels I came to realize that I have much more tire space on the left side than on the right. It seems almost as if I have different offsets on my rear wheels! After doing some measuring and double checking everything I definitely have rear end that is shifted to the right by about 1/2 inch (a lot).

I checked to make sure trailing arm bushings are all centered.
I double checked wheel offsets to be equal.
I double checked t-bar shims to be equal left to right.
I even re-configured the shims to try and move rear end to the left with no success.

The car seems very straight and original with no major damage ever, has anyone ever seen this problem? What did you do to correct? I've done many rear end installs and there is always some variance with how the rear end centers between the fenders but this is by far the worst.

Thanks
 

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Before installation did you put alloy T bar on top of original? Surely has to be where the difference is.
Pete
 

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Before installation did you put alloy T bar on top of original? Surely has to be where the difference is.
Agreed. But I'd revise PSk's statement above to read: "did you put the alloy T bar with its bushings on top of original T bar with its bushings?" In other words, maybe the metal part of the two T bars have the same dimensions, but the bushings or the way they were installed on the alloy T bar differs.

Alfa must have had some manufacturing tolerances in the width between the frame rails where the outer ends of the T bar attaches, since they used shims in that area. But it sounds as if vespam5's situation requires more adjustment than the shims can accommodate.
 

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Similar Situation

Hello,
I installed the Alfaholics Aluminum T-Bar in my US Spec 73 GTV and have a similar condition. I believe the chassis is straight and undamaged.

In my case, the rear is biased to the right by about 1/4 inch. I shimmed the left wheel out by the same to correct. There seems to be enough shimming in the T-Bar to Chassis pivot provided by the supplied parts to correct but I've yet to do this (On the to-do list but I'm trying to not take the car apart again…Its a driver!) When I take it apart, I'll try overlaying the new and old T-Bar… Someday.

I wonder about the Poly bush between the T-Bar and Diff… Could that be a contributor?
 

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Discussion Starter #6
Hello,
I installed the Alfaholics Aluminum T-Bar in my US Spec 73 GTV and have a similar condition. I believe the chassis is straight and undamaged.

In my case, the rear is biased to the right by about 1/4 inch. I shimmed the left wheel out by the same to correct. There seems to be enough shimming in the T-Bar to Chassis pivot provided by the supplied parts to correct but I've yet to do this (On the to-do list but I'm trying to not take the car apart again…Its a driver!) When I take it apart, I'll try overlaying the new and old T-Bar… Someday.

I wonder about the Poly bush between the T-Bar and Diff… Could that be a contributor?
I spent a few hours playing with the rear end alignment last night and the problem definitely seems to be at the poly bushing between the t-bar and diff. I was advised by Alfaholics to shave the poly bushing itself to suit. I decided to go one step further and remove the pivot axle off of the differential housing itself (grind welds and tap out) and put it on my lathe to take some thickness out of it. I will then shave the poly bushing and try to get this rear end to sit even. I did not have this problem on a previous build in which I used a spherical bearing version.

All the above modifications do create some new minor issues with washers and spacers now being required. I will post some pictures of my progress soon.

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What is the weight saving with the alloy T-bar?
 

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What is the weight saving with the alloy T-bar?
Alfaholics Aluminium T-Bar - Classic Alfa Romeo spare parts

Alfaholics says that the weight savings is 4 Kilograms over stock.

Whether that weight savings is worth $72.50 per pound on a road car is a different question, and one for which I have no answer. I'm sure that someone can explain the value though.

I'm not even sure whether the T-Bar is considered sprung, or unsprung, weight.
 

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I am installing a bunch of Alfaholics goodies including an alloy T-bar on a 67 GTV and once everything was done and the car was down on it's wheels I came to realize that I have much more tire space on the left side than on the right. It seems almost as if I have different offsets on my rear wheels! After doing some measuring and double checking everything I definitely have rear end that is shifted to the right by about 1/2 inch (a lot).

I checked to make sure trailing arm bushings are all centered.
I double checked wheel offsets to be equal.
I double checked t-bar shims to be equal left to right.
I even re-configured the shims to try and move rear end to the left with no success.

The car seems very straight and original with no major damage ever, has anyone ever seen this problem? What did you do to correct? I've done many rear end installs and there is always some variance with how the rear end centers between the fenders but this is by far the worst.

Thanks

Quote:
I double checked t-bar shims to be equal left to right.


I just noticed this detail of your comment. There's your problem and your answer. The shims are not expected to be *equal* on both sides. Every car varied even at factory assembly and that is why the shims come in different thicknesses. I learned this when I disassembled my suspension during my complete suspension rebuild.

You should shim on the left and/or right as necessary to center your axle.
Re-read the information from Alfaholics.

"The kit is supplied with a range of spacers to help shim the axle centrally..."

If 'extreme' shimming isn't working, send an email to Alfaholics; I'm sure they've run into this before.

A random thought - did you loosen or remove your rear sway bar when you changed the shimming? If you left it attached to the car it might be enough to pull the axle to one side.
 

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Discussion Starter #10
Quote:
I double checked t-bar shims to be equal left to right.


I just noticed this detail of your comment. There's your problem and your answer. The shims are not expected to be *equal* on both sides. Every car varied even at factory assembly and that is why the shims come in different thicknesses. I learned this when I disassembled my suspension during my complete suspension rebuild.

You should shim on the left and/or right as necessary to center your axle.
Re-read the information from Alfaholics.

"The kit is supplied with a range of spacers to help shim the axle centrally..."

If 'extreme' shimming isn't working, send an email to Alfaholics; I'm sure they've run into this before.

A random thought - did you loosen or remove your rear sway bar when you changed the shimming? If you left it attached to the car it might be enough to pull the axle to one side.
I spoke with A/H about this, they actually recommended I run shims equal left to right and modify one of the conicals! My car appears to be very straight and un-wrecked in the past which is why this is a bit of a head scratcher....then again 1/2" (13mm) is probably acceptable with stock wheels tires, it however is not acceptable when running 15x7 wheels on race tires which need every bit of space available.
 

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The shims should have been installed exactly as they were with the old T-bar, not necessarily even both sides.

Just because your car has not had an accident does not mean that the shims would be even each side. There are something like 100 different panels welded together to get from one end to the other and of course manufacturing tolerances so you chassis may have required different spacers each side from new.

I'm sorry, I do not understand why people install new components without first installing them exactly as the old one was. That should always be the starting point ...
Pete
 

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Tolerance

It's a valid point…

There are something like 100 different panels welded together
On the other hand, to venture a guess, perhaps the T-Bar and Trailing Arm mount points were fixtured to "take them out of the tolerance chain" so to speak. I supposed the outer fender stamping, being of complex curvature and limited positioning criticality would be the likely major source of geometric error.

I found it of note that both mine and the above build yielded error "to the right". Then again two samples hardly represent statistical significance.

I wonder if I move a few shims from left to right… will the little monster will be more capable? :whistling:
 

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Discussion Starter #13
This car only had one factory shim on each side when I got it. With the A/H t-bar installed I am using the two original shims plus one of the provided A/H shims, that is all that fits. With the three shims installed there is NO play side to side yet the t-bar pivots smoothly. This is what I believe to be proper fitment.

I promised pictures, will put them up soon.
 

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On the other hand, to venture a guess, perhaps the T-Bar and Trailing Arm mount points were fixtured to "take them out of the tolerance chain" so to speak. I supposed the outer fender stamping, being of complex curvature and limited positioning criticality would be the likely major source of geometric error.
I checked the chassis drawing and the tolerance for the width of the T bar mounting point is +1mm -0, so pretty tight.
Pete
 

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Discussion Starter #15 (Edited)

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What is a good procedure to verify that the rear axle is centered. My 71 GTV has always had a problem with the right rear outside sidewall rubbing on the lip of the wheel opening. I suspect that some of it is body panel related as many post seem to mention that the clearance between the sidewall and fender lip is less on the right side. Looking into this is on my to do list for this spring is it ever stops snowing in central NY.

Dick Stachowiak
71 GTV
71 Spider
 

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I have realized something that may be at play here - the definition of shims: In the picture of the T-bar below you will see there are two different 'shims'. Poly shims and Body shims. The shims which determine the left/right positioning of the axle are NOT the poly shims shown as #2 in the diagram below, but the unnumbered 'Wankel'/triangle-shaped Body Shims next to the bolts on the right side of the picture. These come in different widths from the factory and you may find one, none, or even two on either side of the T-Bar. These are the shims which adjust for the construction variations in each chassis.

Are these the shims you received from Alfaholics, or did you receive poly shims? Poly shims should be even on both sides of the T-Bar but Body Shims are unique to each car. Left out or reinstalled improperly these will shift your rear axle to the left or right.

I believe that some of us in this thread are talking about Body Shims while others are talking about Poly Shims.



 

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Vehicle Centerline & Alfaholic's T-Bar Shims

After more consideration than really reasonable I decided there are two aspects to centering the rear end (and front) into the chassis; "functional" and "esthetic". For the functional half of my schizophrenic being, I dropped a theoretical point from the actual midpoint between the T-bar to chassis mounting. Did the same in the front using the dog bone mounting. At the horizontal plane of wheel half height, a line through these points is of near god like meaning.
:angel: Vehicle centerline!
I propose that ones tires ought be systemic about this near god like virtual line in free space.

As indicated, realities of build tolerance then came to be understood and an embarrassing thing happened. The superficialities of esthetic looks crept into my conciseness. Sure, I was aligned with the purest of pure "god line" but the edge of the tire was a quarter of an inch DIFFERENT to the beauty of the little monsters fender lip. And a more sinister motivation took over.
:devil2:
So I shimmed my left wheel out a smidge in vanity!

Anyway, the Alfaholics alloy T-Bar setup doesn't use the same poly shim arrangement as original and the shim of much debate above is the wankle like adjustor.
:smartass:
 

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I'd go and simply get a 4 wheel wheel alignment. That will tell you the truth and sort it.
Pete
 

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Thanks for the post. I discovered the same issue on my 67 GTV with 15x7's and lowered. It has about 10mm more fender clearance on the left than right. Which resulted in slight tire rub. I do have poly bushings onthe T bar.
 
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