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The endless excuses guy
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Discussion Starter · #1 ·
I've had my BLT for about 5 months and put about 1000 miles on it. Within the last week, a knock has developed. When I lift up on the rear of the seat (un-weight the bike) is when I hear it. I think it may be coming from the lower shock mount, but I'm not 100% certain. There is a little play there at the lower mount.

So my questions are, what is this knock? Is it the "DU" bushing I hear being discussed? If it is, what exactly is a DU bushing (pleading ignorance here). Are the shock bushings something I would talk to SC about or Fox (RP-3)? Are the bushings an item that comes with the bearing replacement kit? So many questions............

Thanks folks.
 

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It sure sounds like you need new DU bushings / reducers. You should always replace both at the same time (bushings and reducers). The bushing is the cylindrical metallic piece that fits inside the eyelets of the shock. The reducers are the aluminum pieces that interface between the bushings and the rocker or swing link.

Go to your LBS. They will most likely have them in stock.
 

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You might check and see if your shock bolts are tightened to the proper torque. I had just replaced the bearings on my Heckler when I developed the same knocking noise you're describing. I traced it back to the rear shock bolt being about 1/2 a turn too loose. I re-torqued it and it's been fine since
 

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I posted this information on a thread last April......

"Josh at SC was nice enough to call me yesterday to discuss the DU bushing issue on the Blur. He says that the DU bushing is often NOT failed when it feels like it is. He explained that the DU has failed when the reducers practically fall out upon shock removal. If the reducers fit snuggly in the DU, then the DU is fine.

He said the problem(most of the time)is that the frame & linkage often compress a fraction of an inch over time, and the shock/pivot axle becomes TOO LONG to pinch it all together. This can be remedied by shaving a mm off the axle. He said if you can turn the axle with a hex wrench on ONE side, then it's not pinching together properly.

Josh also confirmed that the reducers should NOT move with the shock through it's cycle. You can check this by unbolting the front of the shock and moving the shock as if it were cycling.

I'll shave down that axle and see what happens."


Since then I have not had a single bushing slop incident that couldn't be remedied by tightening the axle bolts. Give it a try.
 

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The endless excuses guy
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Discussion Starter · #5 ·
Thanks for the feedback.

Yesterday, I decided to remove the rear shock to inspect the bearings, bushing, axles, etc. The shock axle/pin was really tough to get out; had to drift it out. Then I found out why. The inner race of one of the bearings was SHATTERED! Went to the local bearing distributor and got suitable replacement and replaced as per SC instruction sheet.

Back to the DU bushings. They were snug within the shock eyelet, but the axle was sloppy within the bushing. So I'm fairly certain that's the source of the knock. Who should I talk to about getting replacement bushings? Santa Crauz of Fox? Not sure who provided the part.

Again, thanks for your input. Its been very helpful.
 

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Rooster said:
Thanks for the feedback.

Yesterday, I decided to remove the rear shock to inspect the bearings, bushing, axles, etc. The shock axle/pin was really tough to get out; had to drift it out. Then I found out why. The inner race of one of the bearings was SHATTERED! Went to the local bearing distributor and got suitable replacement and replaced as per SC instruction sheet.

Back to the DU bushings. They were snug within the shock eyelet, but the axle was sloppy within the bushing. So I'm fairly certain that's the source of the knock. Who should I talk to about getting replacement bushings? Santa Crauz of Fox? Not sure who provided the part.

Again, thanks for your input. Its been very helpful.
Call SC and tell them about your problem. They will have the correct size on hand.
 
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