Vibration Isolator Replacement Solution for DKF Exhaust Hangers

[tiltmode43]

Hi All,

I recently picked up a second hand pair of DKF Exhaust hangers with broken vibration isolators. These seem to have failed on many occasions with the usual blame being placed on over-torquing. Many have posted the isolators could be purchased for $20 from DKF but with multiple failures and some curiosity of another solution, I decided to try researching the part to see what I could find. I'm not intending to criticize DKF in any way but if I've found a widely available solution that allows me to upgrade the durability and longevity of my exhaust hangers at a low price, you bet I'm going to make sure the Z4M community knows about it I'm yet to install this so I can't say it's 100% verified yet but I'll update when I give it a try.

To start, a search brought me to believe this is the part DKF used with his exhaust hangers:

Vibration Isolator, 50 Lb Max, 5/16-18
Price: $2.78 / each
Item: Cylindrical Vibration Isolator
Type: Male Threads Both Ends
Max. Load Downward Compression (Lb.): 50Max.
Load Sideways Shear (Lb.): 9
Cylinder Dia.: 1"
Height: 3/4"
Thread Length: 5/8"
Material: Rubber
Thread Size: 5/16-18

http://www.grainger.com/product/GRAI...Isolator-2NPA3

I stopped by my local Grainger store who had this part number in stock. They pulled them and I compared - same coloring, same R stamp on the side, same dimensions. Now notice in the description it states 50Lb max compression and 9Lb max sideways load. I believe this means these isolators are only intended to support up to 9Lbs perpendicular to the threads. This may help explain why so many have failed. Although you have 2 exhaust hangers + the S2 bolts holding up mufflers, 9lb load may be inadequate given the weight of the muffler + the heat & flex going on.

Upon discovering this, I looked into other options with a higher sideways shear load rating. This search led me to this part:

Vibration Isolator, 125 Lb Max, 5/16-18
Price: $4.69 / each
Item: Cylindrical Vibration Isolator
Type: Male
Threads: Both Ends
Max. Load Downward Compression (Lb.): 125
Max. Load Sideways Shear (Lb.): 20
Cylinder Dia.: 1-9/16
Height: 1"
Thread Length: 5/8"
Material: Rubber
Thread Size: 5/16-18

http://www.grainger.com/product/GRAI...Isolator-2NPA9

The diameter of the sphere on the replacement is .56" larger in total, so effectively .28" larger all around and is 1" compared to the original .74", so .25" taller (longer). I haven't installed the DKF hangers yet but after looking at installed pics, I don't think this will cause any real lose in adjustment. I'm hoping that these will last given their 20lb sideways load, compared to the original 9lb sideways load rating. They also had vibration isolators with 45Lb & 55Lb sideways load rating but both of these were 2" in diameter & 1-3/8" tall, so not certain they would fit. If the 20Lb rating isn't enough, I may try going with one of the higher ratings to see what happens.

I am not 100% certain on my findings as there are no part numbers listed but I'd say it's probable. Assuming this is the case, this is what I've learned:

-DKF vibration isolators have a sideways load rating of 9lbs
-DKF replacement vibration isolators can be purchased for $2.78 each via link above
-An upgraded isolator with over double the sideways load can be purchased for $4.69 each

Update 10.14:
The new vibration isolators came in. Damn these things are beefy, but I think they will work and will help hold the load better than the smaller ones. Comparo pics below with the isolators my pre-owned DKF hangers came with. Also test fit on the hanger, doesn't seem to limit much adjustability, if any at all. Total cost on these after tax was $10.13.









Update 11.17:
Got these installed (along with a set of Rogue cans) and no adjustability issues at all & no undue tension on the isolators; these new vibration isolators worked like a charm for me. This part really doesn't (shouldn't) hold tons of weight up if properly installed (I tightened rear outermost hangers, then S2-muffler flanges for main fit, then DKF). So far so good with the beefier vibration isolators. We'll see how they do over time but for now I'm very happy with these. I'm pretty anal about exhaust tip fitment and was able to fine tune things enough to meet my standards.







Cheers!

[Vanne]

Mate, I've said it before,

Matt, you ARE the man!!!

[Pheonix]

Awesome find indeed! I also purchased a set of hanger from another member and was hesitated to install them due the the issues with tearing. Granger is only 10 minutes so definitely going to pick some up next week and test them out. Thank you for sharing.

[tiltmode43]

Originally Posted by Vanne

Mate, I've said it before,

Matt, you ARE the man!!!

Thanks Vanne! Congrats on getting the APR splitter from Lev BTW!

Originally Posted by Pheonix

Awesome find indeed! I also purchased a set of hanger from another member and was hesitated to install them due the the issues with tearing. Granger is only 10 minutes so definitely going to pick some up next week and test them out. Thank you for sharing.

Not sure if you've already picked them up but updated OP with pics of the part number I referenced & comparo with the old

[Nate4641]

This looks promising! However I am a little worried on how high I could mount the exhaust with the new isolator vs the old. With my RPI cans I have the isolator all the way to the top, but it does droop a bit. I used the technique of tightening the xpipe-to-muffler flange in a way that pushes the muffler higher up, but it still puts a lot of tension on the isolator. I have ripped one, and DKF gave me a good deal on buying a few more instead of just one.

For sure please let us know how it goes with many, many detailed pics of the install!

[Beedub]

if anyone can grab some of these and send me 2 via usps i would appreciate it.... ordering through these guys will cost me a fortune.

[tiltmode43]

Originally Posted by Beedub

if anyone can grab some of these and send me 2 via usps i would appreciate it.... ordering through these guys will cost me a fortune.

Once I try them out this coming week and verify they work I can pick up a couple more and send them to you, just cover the cost/gas to pick them up/shipping

[Beedub]

tilt mode thank you buddy!!!! appreciate that alot!

[Jumbosock]

The problem is the expanding metal when it gets hot. Everything shifts to the rear about 1.5 inches. I don't even think 20lbs will be enough. I ended up buying an exhaust hanger rubber thingy at Autozone and cutting it so it was just a donut. I then got a bolt and bolted it together. It holds well and I still have the adjustability of the DKF but there is more noticeable vibration.

[pokeybritches]

Good find! It's worth mentioning that:

1. Over tightening produces torsional stress, which is a twisting stress. It is different than (but related to) the "sideways" shear described above. If torsional stress is applied, its sideways shear rating reduces dramatically.

2. If the larger vibration isolators utilize the same rubber compound, NVH reduction should be similar to the ones DKF supplies. A harder rubber compound will cause more NVH to be translated to the cabin.

3. The vibration isolator does not support the entire weight of the muffler.

It looks like you've got a great solution on your hands. One of my OEM exhaust hangers has failed, and if I can get my hands on a set of DKF hangers, I may give these isolators a shot.

[tiltmode43]

Originally Posted by Nate4641

This looks promising! However I am a little worried on how high I could mount the exhaust with the new isolator vs the old. With my RPI cans I have the isolator all the way to the top, but it does droop a bit. I used the technique of tightening the xpipe-to-muffler flange in a way that pushes the muffler higher up, but it still puts a lot of tension on the isolator. I have ripped one, and DKF gave me a good deal on buying a few more instead of just one.

For sure please let us know how it goes with many, many detailed pics of the install!

Originally Posted by Beedub

tilt mode thank you buddy!!!! appreciate that alot!

Originally Posted by pokeybritches

Good find! It's worth mentioning that:

1. Over tightening produces torsional stress, which is a twisting stress. It is different than (but related to) the "sideways" shear described above. If torsional stress is applied, its sideways shear rating reduces dramatically.

2. If the larger vibration isolators utilize the same rubber compound, NVH reduction should be similar to the ones DKF supplies. A harder rubber compound will cause more NVH to be translated to the cabin.

3. The vibration isolator does not support the entire weight of the muffler.

It looks like you've got a great solution on your hands. One of my OEM exhaust hangers has failed, and if I can get my hands on a set of DKF hangers, I may give these isolators a shot.

Got these installed this last weekend, no adjustability issues, no undue tension on the bushings, etc. Will upload pics tonight! Pokey, I see what you mean about not carrying the weight of the muffler, this part really doesn't (shouldn't) hold tons of weight up if properly installed (I tightened rear outermost hangers, then S2-muffler flanges for main fit, then DKF).

So far so good with the beefier vibration isolators We'll see how they do over time but for now I'm very happy with these. I'm pretty anal about exhaust tip fitment and was able to fine tune things enough to meet my standards. Again, this is mainly due to how things are tightened down at the S2-muffler flange though the DKF hangers really let you fine tune it.

[tiltmode43]

Updated OP with installed pics.

Originally Posted by Beedub

tilt mode thank you buddy!!!! appreciate that alot!

PM me your addy and I'll send you the total & my PayPal