SUMMIT CRUISERS Jr
SILVER Star
Backstory
I installed new 35x12.5r17 Kenda Klever MTs back at the beginning of 2015 at around 360k miles and they were balanced with airsoft BBs. Just before this, I installed Nitro 4.88 gears along with full axle rebuilds front and rear. The new Kendas rode pretty well and were smoother than the BFG KM2s that came off of it. Previously, I had a set of BFG KM1s that I had purchased used. They had some slightly abnormal wear and thus always had a slight vibration. So really for as long as I can remember, my Cruiser has had a slight vibration. What's weird is that the vibrations seem to almost disappear when I have a large tailwind.
Fast forward to Spring of 2016...I found some dangerous cracks forming between the tread lugs on my tires. This was less than a week away from leaving for a 3000 mile trip to Moab and Colorado. When they replaced my tires under warranty, I had the shop leave the bead unset so I could add BBs to balance the tires. The new set really shook the cruiser around, and both body shake and steering wheel shake were slightly present around 55mph and brutal around 75mph. Due to the Kendas still being a fairly new tire, I chalked it up to being a more out of round batch tire. My dad and I decided to add more BBs. Going from the previously successful 8oz to 16oz, we did not notice a gain.
Over the past year I have chased down this mysterious vibration. Currently I have 396k miles.
My rear output bearing on the transfer case had slight play in it. It was also slightly leaky. We replaced this and did not notice a reduction in vibration.
After returning from my 2017 Spring Break, my dad helped me watch the cruiser from another vehicle on the highway and looked for a potentially bad tire/wheel combo.
Noticeably worse than the rest, the passenger rear tire was really vibrating. The passenger front tire was smooth so we started by swapping the tires. No luck
Next we checked all the pressures. All good there. I also experimented with different pressures with no success.
We swapped the rear shocks side to side hoping that maybe one of them was not providing enough damping. Not much luck there.
Deflated the residual air pressure in my rear air bags. Helped just slightly.
Checked the wheel bearings. All good there.
Then we drooped the rear axle with the tires off the ground and put a prybar between the lower RCA mount on the frame and the arm. Sure enough it had some play that would wiggle the rear axle. A lot of the bushings had deep cracking evident, and while some looked better than others, I'm glad we changed them all out. The panhard bar seemed to have the best surviving bushings. After this, we replaced the upper and lower control arm bushings along with the panhard bushings. Here is where the photos of the bushings can be seen if anyone is curious what 400k miles does to them.
The shaking still existed.
Next up was a set of OME sport series L shocks and a matching set up front. The ride tightened up, but the shake still existed. I had also put on a new OME steering stabilizer to no avail.
I have also torn into the front hubs several times after checking bearing preload and retorqued them. New slotted FZJ80 sized front brake rotors and calipers also went on which would eliminate a heavily warped rotor. None of this ever seemed to fix the bigger issue.
My steering box is also questionable. I have a rebuild kit for it as it used to leak at what seemed like higher altitudes, but stop leak has stopped that and it hasn't dripped a drop in months (except where it was dripping some drops on Poison Spider on Moab, but it hasn't leaked since coming down in elevation...weird I know)
That pretty much contains about everything I had done up until May 2017. Since a bad mtb wreck, I haven't been able to do much work, but I have been learning about various vibration causes and symptoms. Deep down I thought the shake could be a driveline vibration, but at the same time, this is a very harsh body shake as well as steering wheel shake.
I found this great 1990's Toyota video on Youtube addressing NVH (Noise, Vibration, and harshness) that explains how to calculate the different kind of frequencies found among different vibrations ie driveline, vs tire and axle shaft vibrations. This convinced me I did not have an issue with either driveshaft as my vibration is closer to 15Hz.
I also learned about the run out of the wheel and tire, and how you can phase the two to help with vibrations. The person who bought my 17" FJ Cruiser steelies said "I am buying these to replace the 8 spoke wheels as they never seem to balance out". So ever so slightly I thought it may be the phasing of the tire and wheel as my previous set had been fine.
After a lot more thinking, I decided to set up an appointment to have a new set of 315/70/17 BFG KO2s installed so I could rule out or confirm that the shake was coming from the tires. The local 4wheelparts was advertising a set of 4 for $689 installed. Unfortunately, after speaking on the phone, the employee said this deal only applied to C rated tires which their ad said nothing about.
Then I decided to mount my GoPro in various places underneath to watch the axles, tires, driveshafts, etc while running some highway sections. This ended up being a huge waste of time.
Yesterday, I went home for some medical appointments, and my dad and I checked the tie rods and all front end components only to learn that nothing had changed. The only remaining thought is a possibly worn steering box as it does have 400k miles on it, but my steering still feels pretty tight and responsive.
At this point I figured I would go to the local tire shop and see if they would run a wheel/tire combo and see if it balances out with the BBs. They were not going to do that, since the owner didn't believe in balancing BBs. I also mentioned checking the run out of the wheel and tire, and putting them in phase, but they had never heard of anyone doing that. He suggested just ditching the BBs and balancing them.
Anyways, after all of the thinking and work that went into trying to find this shake, removal of the BBs and a $90 balance job did the trick. It is almost funny how simple of a fix this was and the amount of miles I have endured this annoying and at times scary vibration. After this ordeal I think BBs can work, but it really depends on the tire. My brother has 35" Mastercraft MTs and it stays pretty smooth. Now mine is smooth until 85mph which is as fast as I could get it up to.
I installed new 35x12.5r17 Kenda Klever MTs back at the beginning of 2015 at around 360k miles and they were balanced with airsoft BBs. Just before this, I installed Nitro 4.88 gears along with full axle rebuilds front and rear. The new Kendas rode pretty well and were smoother than the BFG KM2s that came off of it. Previously, I had a set of BFG KM1s that I had purchased used. They had some slightly abnormal wear and thus always had a slight vibration. So really for as long as I can remember, my Cruiser has had a slight vibration. What's weird is that the vibrations seem to almost disappear when I have a large tailwind.
Fast forward to Spring of 2016...I found some dangerous cracks forming between the tread lugs on my tires. This was less than a week away from leaving for a 3000 mile trip to Moab and Colorado. When they replaced my tires under warranty, I had the shop leave the bead unset so I could add BBs to balance the tires. The new set really shook the cruiser around, and both body shake and steering wheel shake were slightly present around 55mph and brutal around 75mph. Due to the Kendas still being a fairly new tire, I chalked it up to being a more out of round batch tire. My dad and I decided to add more BBs. Going from the previously successful 8oz to 16oz, we did not notice a gain.
Over the past year I have chased down this mysterious vibration. Currently I have 396k miles.
My rear output bearing on the transfer case had slight play in it. It was also slightly leaky. We replaced this and did not notice a reduction in vibration.
After returning from my 2017 Spring Break, my dad helped me watch the cruiser from another vehicle on the highway and looked for a potentially bad tire/wheel combo.
Noticeably worse than the rest, the passenger rear tire was really vibrating. The passenger front tire was smooth so we started by swapping the tires. No luck
Next we checked all the pressures. All good there. I also experimented with different pressures with no success.
We swapped the rear shocks side to side hoping that maybe one of them was not providing enough damping. Not much luck there.
Deflated the residual air pressure in my rear air bags. Helped just slightly.
Checked the wheel bearings. All good there.
Then we drooped the rear axle with the tires off the ground and put a prybar between the lower RCA mount on the frame and the arm. Sure enough it had some play that would wiggle the rear axle. A lot of the bushings had deep cracking evident, and while some looked better than others, I'm glad we changed them all out. The panhard bar seemed to have the best surviving bushings. After this, we replaced the upper and lower control arm bushings along with the panhard bushings. Here is where the photos of the bushings can be seen if anyone is curious what 400k miles does to them.
The shaking still existed.
Next up was a set of OME sport series L shocks and a matching set up front. The ride tightened up, but the shake still existed. I had also put on a new OME steering stabilizer to no avail.
I have also torn into the front hubs several times after checking bearing preload and retorqued them. New slotted FZJ80 sized front brake rotors and calipers also went on which would eliminate a heavily warped rotor. None of this ever seemed to fix the bigger issue.
My steering box is also questionable. I have a rebuild kit for it as it used to leak at what seemed like higher altitudes, but stop leak has stopped that and it hasn't dripped a drop in months (except where it was dripping some drops on Poison Spider on Moab, but it hasn't leaked since coming down in elevation...weird I know)
That pretty much contains about everything I had done up until May 2017. Since a bad mtb wreck, I haven't been able to do much work, but I have been learning about various vibration causes and symptoms. Deep down I thought the shake could be a driveline vibration, but at the same time, this is a very harsh body shake as well as steering wheel shake.
I found this great 1990's Toyota video on Youtube addressing NVH (Noise, Vibration, and harshness) that explains how to calculate the different kind of frequencies found among different vibrations ie driveline, vs tire and axle shaft vibrations. This convinced me I did not have an issue with either driveshaft as my vibration is closer to 15Hz.
I also learned about the run out of the wheel and tire, and how you can phase the two to help with vibrations. The person who bought my 17" FJ Cruiser steelies said "I am buying these to replace the 8 spoke wheels as they never seem to balance out". So ever so slightly I thought it may be the phasing of the tire and wheel as my previous set had been fine.
After a lot more thinking, I decided to set up an appointment to have a new set of 315/70/17 BFG KO2s installed so I could rule out or confirm that the shake was coming from the tires. The local 4wheelparts was advertising a set of 4 for $689 installed. Unfortunately, after speaking on the phone, the employee said this deal only applied to C rated tires which their ad said nothing about.
Then I decided to mount my GoPro in various places underneath to watch the axles, tires, driveshafts, etc while running some highway sections. This ended up being a huge waste of time.
Yesterday, I went home for some medical appointments, and my dad and I checked the tie rods and all front end components only to learn that nothing had changed. The only remaining thought is a possibly worn steering box as it does have 400k miles on it, but my steering still feels pretty tight and responsive.
At this point I figured I would go to the local tire shop and see if they would run a wheel/tire combo and see if it balances out with the BBs. They were not going to do that, since the owner didn't believe in balancing BBs. I also mentioned checking the run out of the wheel and tire, and putting them in phase, but they had never heard of anyone doing that. He suggested just ditching the BBs and balancing them.
Anyways, after all of the thinking and work that went into trying to find this shake, removal of the BBs and a $90 balance job did the trick. It is almost funny how simple of a fix this was and the amount of miles I have endured this annoying and at times scary vibration. After this ordeal I think BBs can work, but it really depends on the tire. My brother has 35" Mastercraft MTs and it stays pretty smooth. Now mine is smooth until 85mph which is as fast as I could get it up to.
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