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Discussion Starter · #1 ·
I have 36k miles on my manual transmission 2012 Elantra. I replaced the rear shocks with KYB’s which provided some improvement to the handling. I have been following the thread on 4 wheel alignment http://www.hyundai-forums.com/231-md-2011-elantra/205850-4-wheel-alignment.html. At my last tire rotation, I was shocked when I measured the tire tread depth. The rear tires were wearing twice as fast as the front tires. My past experience with front wheel drive cars is that the front tires wear 2 to 3 times as fast as the rear tires due to steering and drive wear. I took the Elantra to the Hyundai dealer and complained about the rear tire wear. The dealer checked the alignment and stated that the alignment was “in spec”. See attached “Alignment Before”. Note: many alignment shops will provide a free alignment check.


The front toe measured close to zero. The rear toe measured 0.55 degrees. There may be a formula for determining the amount of tire wear related to toe in, but I believe that 0.55 degrees is excessive. I suspect this is the reason many Elantra owners report poor tire mileage. Tire rotation only spreads the wear to all tires. Due to the lack of adjustments for the rear axle, alignment would need to be made by the use of shims between the rear hub and the axle. I checked with some specialty alignment shops in the Phoenix area, but the prices quoted were in the $250 to $500 range, due to the selection of a shim thickness, install, check toe in and repeat until correct.


I decided to see what I could do on my own. Removing the hub is relatively simple, see Hub with Shim photo:
1. Park the car on a level surface.
2. Block the front wheels. Do not set the parking brake.
3. Loosen the lug nuts on the selected rear tire.
4. I used a floor jack placed under the rear spring next to the tire to raise the rear tire.
5. Remove the lug nuts and tire.
6. Remove the two bolts securing the disc brake caliper to the axle.
7. Remove the brake caliper and support the caliper on a block of wood.
8. Remove the two screws holding the brake rotor using a large Phillips screwdriver. I needed to press hard on the screwdriver while unscrewing the screws.
9. Remove the brake rotor.
10. Remove the four bolts securing the hub and remove the hub.

What I wanted to determine is what thickness of shims on the two sides would be needed to reduce the toe in to near zero. I made a tracing of the flange and measured the bolt spacings, see Hub Dimentions photo:
1. 3.5” between upper bolts
2. 3.3” between lower bolts
3. 2” between upper and bolts
4. There is also a 0.25” guide pin on each side.
5. The center opening for the bearing is 2.9”

I decided to use a 3” long by 1” wide shim. In order to calculate the required shim thickness, I reviewed some high school geometry:
TAN angle = opposite side / adjacent side
TAN angle = thickness / bolt spacing
Thickness = TAN angle * bolt spacing
I used 3” for bolt spacing since I was not sure where the pivot point would be for the hub with the shim. I wanted to reduce the total toe in from 0.55 degree to 0.05 degree so I used 0.25 degree for each side.
Thickness = TAN 0.25 * 3”
Thickness = 0.013”

Whoa! I could not believe that only 13 thousandths of an inch would be needed to correct the alignment on each side. I had new respect for Hyundai for the tolerance they would keep for the rear axle manufacturing. However, I did not approve of their economic choice to not make the rear axle alignment adjustable.

Next, I needed to find a shim of this thickness. 30 gauge steel is 0.012”, 30 gauge stainless is 0.0125”, 28 gauge aluminum is 0.0126”. The company I work for has a small machine shop, so I checked with the machinist. He did not have any material this thin, but had a scrap piece of 3/16” thick laminated aluminum made of 0.003” layers. I pealed 4 layers together, which measured 0.012” with a dial caliper. I cut the aluminum into two 3” by 1” strips with tin snips. Then I drilled two 0.4” holes for the two bolts and one 0.3” hole for the guide pin. I also trimmed the inside edge to clear the bearing . Two identical shims were constructed.

I mounted the shim to the front side of the hub and reassembled. I repeated this adding the other shim to the other side. Taking the vehicle to an alignment shop for a free alignment check resulted in the attached “Alignment After”.

A couple of observations about the second alignment report:
1. These results were slightly different that those measured at the Hyundai dealer as are the specs.
2. The left rear toe in was where I wanted.
3. The right rear toe in could perhaps use another 0.003” layer of aluminum.
4. The front toe in was adjusted in by the shop even though not requested, but maybe made worse. My steering wheel is now slightly turned right. I may try to adjust this back out a little.

Final observations and questions:
1. The Elantra now handles and corners well. I am not sure how much improvement there is.
2. I expect the tire wear rate for the rear tires will decrease. Time will tell.
3. What is the optimum toe in for minimal tire wear and reasonable handling? Is it the same for the front and rear?
4. I did not attempt to adjust for rear camber. Camber could be reduced by adding shims to the top two bolts. What is the optimum camber for minimal tire wear and reasonable handling? Is it the same for the front and rear?
 

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That's interesting, I throw my hat at you for doing this. I suspect that my rear axle needs the same alignment method. I should ask an alignment shop I know in town. Hyundai will tell me that my car is within specs.
 

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Discussion Starter · #3 ·
I decreased the front toe in by adjusting the right front tie rod length, rotating the adjustment 60 degrees. The steering wheel now appears about centered and should be about where it was before the previous shop adjustment. I also added a 0.003” shim to the right rear hub. I then took the Elantra to a third alignment shop for an alignment check. See Alignment 2-4.

Looking at the results, I see that I have a problem. Comparing these results with the previous results:
1. The left and right toe in for the front are identical, even though I decreased the toe in and the steering wheel position confirms it.
2. The right rear toe in shows a decrease from 0.15 degree to 0.10 degree as expected, but the left rear shows an increase from 0.05 to 0.20 which is puzzling. The total toe for the rear increased from 0.20 degree to 0.30 degree with the addition of the 0.003” shim.

At this point I need to step back and think about what is going on. As an Engineer, I am used to dealing with calibrated measurements with calculated uncertainty factors. I blindly assumed that I could get an alignment check at one shop, trust those readings, make my adjustments and go to a different shop and trust those readings.

Here are some issues as I see it:
1. All these shops used computerized alignment. Is there any variation with the skill of the operator?
2. When was the last calibration performed on the alignment equipment?
3. Is there a quick check performed to verify that the alignment is still good?
4. The resolution of the Caster on the print out is 0.1 degrees, what is the accuracy?
5. The resolution of the Toe on the print out is 0.05 degrees, what is the accuracy?
6. How repeatable are the results?
7. What is the variation from shop to shop?

I now suspect that my initial calculations may have under estimated the required shim thickness for the rear hub. This first calculation provides an initial shim thickness which when installed, provides a first guess. Alignment measurements are repeated and the shim thickness is adjusted. This process is repeated until the alignment is acceptable.
 

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sbr711 is our local tech guru. Especially when it comes to alignments. If he gets a chance to see your figures and read this post, he'll surely have some remarks that might help you with this.

Regarding operator skill variables: I would say, yes. I did a test once in a calibration lab. Provided a micrometer standard (calibrated to NIST) to two different machine operators and asked both to give me a measurement reading on a gauge block (also certified). Although they both came close, neither were spot-on exact nor any of their two measurements identical.

But we're not talking about building the next lunar module rocket engine. It's just an alignment, yes? No, it's not JUST an alignment. For OCD people like me, it matters. :laughing:

Besides, tires cost money. While I am not that concerned with my daily/weekly MPG's, I am not thrilled with the prospect of going to the tire store every so many thousands of miles because my car's rear alignment can't be adjusted and prematurely wears out the tread. So, my only line of defense (at this time) is tire pressure vigilance, routine rotations, & wheel balance.
 

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Too bad you have to do this yourself - Hyundai should have come op with a solution by now. This version of the Elantra is now 3 years old. My current set of tires will be down to the tread wear indicators at 18K miles.
 

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Discussion Starter · #6 ·
Have you had your alignment checked? I would really be interested to know what the numbers are, considering your poor mileage. The Hyundai dealer will check the alignment for free if you complain about poor tire mileage. Many other tire shops will also do a free alignment check. Post your results.
 

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I have had several alignments - the last one shown below. On a previous alignment they shifted the axle from about equally bad on both sides in the back to good on the left and rediculous on the right.
 

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Discussion Starter · #8 ·
Your total Toe in the rear is similiar to mine before I added the shims. Adding a shim to the right rear hub would reduce the rear Toe in. However, my tires without the shims definately lasted longer than yours.
 

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Man, wish there was a way to just turn in a set of specs and say align it to this.
Another complication is if the tires are rotated every 5K miles, won't it be somewhat difficult to narrow down tread wear pattern locations without having to get alignment specs to compare with? Even then it's still somewhat a guess especially with non-directional tires.
I have free oil changes and rotations every 5K miles as long as I have the car, so I'm not going to pass on that.
 

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Discussion Starter · #10 ·
The front end numbers on my vehicle look good for camber, castor and toe in. With the shims, I can also adjust the rear toe in and also if needed, rear camber. My question is what are the best rear toe in and rear camber settings for the Elantra?
 

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My guess is that you are in good shape in the rear. I doubt anyone will suggest an optimum alignment. If you want to tweek some more you might consider getting the left toe down to 0.1 also.
 

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Discussion Starter · #12 ·
Conclusions

After doing additional research, which confirmed my desire reduce to the rear toe to near zero, I placed six 0.003” shim layers for a total of 0.018” on both rear hubs. At this time, I decided to not adjust the rear camber, although this could result in increased inside tire wear. A good source of info on tires and alignment is CapriRacer’s web site: Barry’s Tire Tech http://www.barrystiretech.com/alignmentrecommendation.html . Due to the inconsistency in results between alignment shops, I had my alignment checked at two additional shops. Maybe I should have gone for the best two out of three. See attached results.

Observations:
1. The results at Greulichs look reasonable. The Firestone toe results look strange. Total toe measurements were similar for both shops.
2. I observed that during the Firestone alignment, the Elantra was angled a little to the left on the rack. Don’t know if this would affect the results.
3. Both shops used the same Hunter computerized alignment equipment.
4. I asked both shops when the last calibration was performed on the equipment. They both thought in the last 6 months, but were not sure. They commented that there was an annual update.
5. I asked if any verification checks of the alignment system were performed. They both looked confused and stated that the system was accurate.

Final Conclusions:
1. Be careful which alignment shop you use. Check around to see which one has a good reputation. Of the five shops I used, only the Hyundai dealer and Greulichs provided results that I am comfortable with.
2. Camber and Castor measurements were reasonably consistent at all shops. Toe measurements varied from shop to shop.
3. The only easy adjustment on the Elantra is front Toe. Going to a random alignment shop will result in hit or miss front Toe adjustment.
4. Total rear toe was reduced from 0.55 degrees to 0.06 degrees with the use of two 0.018” shims.
5. My adjusted formula for estimating shim thickness is: Thickness = TAN degree * 4.2
6. My Elantra handles well and I should get excellent tire wear.

So how does this apply to other Elantra owners?
1. This was my first attempt at adjusting alignment. The process was enjoyable for me, but did take some time for the research and initial work. The last change took me about 15 minutes to make the two additional shims and 30 minutes to install the shims on both sides. Getting the free alignment checks took about 1 hour each.
2. One would need to get an alignment check at a Hyundai dealer or other reputable alignment shop. Using the rear toe measurement, the thickness of the shim for each side would be calculated. Make the 3” by 1” shims and install on each side. Repeat the alignment check to verify the new rear toe.
3. At this point the results may be close enough. This should definitely reduce the rear tire wear.
 

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Nice write up and great effort. Thanks

Though the proof is what happens with tire wear and if you have any negative side effect on brake wear. Please update when appropriate.
 

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You might want to check the disk brake clearences pad to rotor after your alignment tweek. If they are off too much you might want to shim the caliper assembly as well.
 

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You might want to check the disk brake clearences pad to rotor after your alignment tweek. If they are off too much you might want to shim the caliper assembly as well.
My disclaimer - I am not a mechanic so do the above at your own risk.
 

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Discussion Starter · #16 ·
The toe was adjusted out by 0.25 degree on each side. This results in less than 1/100 of an inch difference over the width of the brake pad. My brake pads tend to last a long time, but I will monitor the wear.
 

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Just to let you know. your local car part does have a part number for the shim on the elantra, it cost around 20$, and come with a chart that tell you ln what direction to put it and what it will affect.
Also it should have been but behind that backplate, so the caliper and disc would still be lign up perfectly

I charge around 200$ for all wheel, with 2 shim install, for an alignment at my job
 

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Just to let you know. your local car part does have a part number for the shim on the elantra, it cost around 20$, and come with a chart that tell you ln what direction to put it and what it will affect.
Also it should have been but behind that backplate, so the caliper and disc would still be lign up perfectly

I charge around 200$ for all wheel, with 2 shim install, for an alignment at my job
Specialty Products 75800?
 

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Discussion Starter · #19 ·
The plastic composite shims are another way to adjust the rear Toe and Camber. I preferred to use a metal shim. Mounting the shim behind the back plate would have the same effect on the caliper to disc alignment, since the caliper is mounted to the axle.
 

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Discussion Starter · #20 ·
Reasons for adjusting the rear alignment

Reasons for adjusting the rear alignment.
1. There is a difference between the left rear and right rear alignment readings that is causing a handling issue.
2. Rear tire wear caused by rear toe in.
3. Desire to change rear camber settings.

What are the effects of reducing the rear toe setting?
1. Reduced rear tire wear.
2. Increased oversteer.

From a post by only1db in the veloster alignment forum:

what happens is when you point the wheels in the rear toward the inner portion of the car / \ the rear tires will want to go IN. When you toe the rear out | | the rear tires will follow the path of the front tires. This will end up with the rear of the car rotating around and when pushed will induce oversteer. Hyundai intentionally puts toe in...in the rear to help with the oversteer. People are more apt for dealing with understeer then oversteer. Especially in a FWD car.

We can NOT fix the alignment without some modifications to the suspension as noted before by placing shims behind the bearing assembly or some other mod.

the argument here is that one person thinks it is excessive amount while me and others thinks that while not ideal...it is acceptable and other manufactures do the same thing...not just Hyundai.
 
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