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premature main bearing wear on Rocky Mountain Slayer

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Discussion starter · #1 ·
Hey mtbrs,
I am posting this today because I am a bit irritated by the short lifetime of my lower swingarm bearings, the large ones beneath the crank, on my RM Slayer 2020.

I built the Slayer in March 21 and started riding it on 25th March 2021. I disassembled the rear triangle to check the bearings on the 6th August 2021 to find all linkage bearings and the large swingarm bearings to be dead. I did 1000 km on the bike in that time. I went and replaced all the bearings. Today I disassembled everything again. The large lower swingarm bearings are shot again. They are very hard to turn and will only turn 1/5th of a turn using a lot of force. The bearings were used for 828 km on the bike.

Is this normal? I keep using my quality torque wrench on all the bolts, I grease and clean the bike regularly. I am a bit baffled by the very short lifetime of the bearings, as I have never experienced such a short running time on other bikes I have used. I am just worried that the bearing seats might be crooked and cause premature wear. Do you have any pointers or ideas? It´s a bit frustrating.

The OEM bearings were replaced by 6001 2RS MAX / 6001VRS items, that are declared as having a high material resistance and being made for slow rotational use.

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#2 ·
I have a polygon n-9 2019. I have replaced 3 sets of bearings in same spot 3800 miles at this point. I regressed bearings about 500 miles so I get maybe a little more life before they die. I ride mainly trails no jumping. 230 with pack. Just life at this point. There are bearings out there that have life time warranty (very expensive) could be option. Good luck.
 
#5 ·
No pressure washer for me. No rust at all or water evident in any of my bad bearings that I have replaced. All bearings on bike have been replaced at least once. I have put a cover close to bearings on bottom so water is not a problem for me. I Only use original bearings endo I think they are called. May try the lifetime bearings next time. It is hard to spend 140 dollars for 2 bearings. I wish they would go back to brass bushing, I have a 1996 pro flex with 2 times the miles all original. Go figure.
 
#9 ·
Same with my 2018.

By comparison i still have 2 x 2012 santa cruz blurs the my wife and i used and now my kids. Still original bearings!!!!!!

The problem us the bearing are too small. Its s design fault. Keep replacing bearings. Pack em with grease. The the reality is you will burn more bearings. The only real fix is a different design.
 
#10 ·
How do the bearings feel when out of the bike? Maybe the bores in the frame are too tight or left and right is out of axial alignment. I find bearings are not always installed that well from factory so it's worthwhile checking this on all new bikes before riding.

My 2019 Slayer had shot main bearings after 6 months but since I replaced and aligned them correctly, torqued preload correctly etc I get around a year out of them with a 6 monthly rotation .
 
#12 ·
Cleared2land said:
^^^ How do you align a press fit bearing correctly?
Click to expand...
Press both sides in almost all the way (one side at a time is ok), then finally push both sides home at the same time, with a proper sized die that fits tightly in each bearing, and a through bolt that aligns the dies so they are parallel:

Image




Or for swingarms just push one side in at a time, but use the die and throughput through the opposite side for alignment purposes:

Image
 
#13 ·
teK-- said:
Press both sides in almost all the way (one side at a time is ok), then finally push both sides home at the same time, with a proper sized die that fits tightly in each bearing, and a through bolt that aligns the dies so they are parallel:

View attachment 1988566



Or for swingarms just push one side in at a time, but use the die and throughput through the opposite side for alignment purposes:

View attachment 1988567
Click to expand...
That’s how I did it on the floor of my local Specialized dealer after they were unable to press the bearings in correctly… they kept telling me it’s supposed to be rough and hard to turn!


Sent from my iPhone using Tapatalk
 
Discussion starter · #15 ·
phantoj said:
Do you ride a lot of miles, or ride in wet conditions?
Click to expand...
A lot... I don´t know. 3-4 times per week, usually 1,5 hour evening rides during the week. 30-50 km / 1000-1500 m/altitude on the weekends. Wet, yes, I ride in all conditions.

teK-- said:
How do the bearings feel when out of the bike? Maybe the bores in the frame are too tight or left and right is out of axial alignment. I find bearings are not always installed that well from factory so it's worthwhile checking this on all new bikes before riding.

My 2019 Slayer had shot main bearings after 6 months but since I replaced and aligned them correctly, torqued preload correctly etc I get around a year out of them with a 6 monthly rotation .
Click to expand...
I received a reply from Mathieu at Rocky Mountain, who´s a really helpful human. He said:
Hi Benjamin,

Our suggested service interval for bearings is once a season. I don't actually have a suggested mileage for something like this. That said, it will be normal for the main pivot bearings to wear fastest as they see the most forces. Whether or not the wear is normal is harder to judge.(...)
Click to expand...
So yeah, they have almost seen 1 year, so it would be in their suggested service interval.
 
Discussion starter · #16 ·
Here´s a picture of the inside. Looks like an emulsion of oem grease and water.
I cleaned them and regreased them. This is just a temporary fix because I already ordered a new set. Apparently the wear is just what it is and there´s not much I can do.

Image
 
#17 ·
If your bearings are out of alignment your pivot bolt will be hard to push through without anything else hooked up. That’s easy to figure out. At the end of the day someone pointed out earlier the bearings are just to small for the load put on them. The industry can fix, if not so worried about every gram the bigger bearings would add. I just planed in my maintenance 400 to 500 miles to check, lube, or replace as needed. My next Bike will have fewer bearings and a taller bottom bracket if I can find the right one. My 2003 ironhorse only has 2 bearings and I easily put over 1000 miles or more before replacing bearings on that bike. Ride on.
 
Discussion starter · #18 ·
Nah mate, the bolt goes in just fine. It´s a snug fit. I get your Iron Horse reference, but to be honest, there´s not much in this world that would make me want to swap my Slayer for an 03 Iron Horse.
 
#20 ·
Ben39 said:
A lot... I don´t know. 3-4 times per week, usually 1,5 hour evening rides during the week. 30-50 km / 1000-1500 m/altitude on the weekends. Wet, yes, I ride in all conditions.



I received a reply from Mathieu at Rocky Mountain, who´s a really helpful human. He said:


So yeah, they have almost seen 1 year, so it would be in their suggested service interval.
Click to expand...
That is a lot of riding.... wear seems normal for you in that case.

Recommendations of annual service for anything are usually based on around 120 hours moving time, which is 2 rides per week of around hour and half total time each.

I ride once a week but bigger rides of around 2.5 hours moving time, so for me an intermediate service at 6 month and new bearings around a year works well.

If you use Strava a great app to track usage and service intervals of all components, based on moving or actual time, then download Pro Bike Garage.
 
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