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Discussion Starter #1 (Edited)
We rode from 6000 to 10,000 feet yesterday--mostly 2L or 4L (AWD). Descending from 10,300' was pretty steep, and my wife and I both noticed that there was a "oscillation" in the EBS. 2H, no rear tire sliding, no throttle. Normally on a lower pitch, it EBS' to about 1350 rpm. In this case, it slowed to 2100 rpm, kicked up to 2500 rpm, back to 2100 rpm, etc. It repeated this about every 2 seconds (0.5 Hz). I weight 165, she's about 140. Two new Sportsman 570 EPS/EBS with about 30 hours on them. Belts are tight.
Obviously, at a stop with no (idle only) throttle, there is no engagement of the drive belt if in 2H or 2L (though I don't leave it there long at an idle). So, if there is some wheel speed, there should be "engine" braking (compression braking) until it stops, right?
What's going on? I don't think our 2015's (same model) did this.

What I learned from my 2014 posting:
"EBS= Engine Braking System
  • It's just a one-way bearing in the primary clutch that holds back the machine through the belt and tranny when you let off the throttle. It ONLY brakes the rear wheels.
  • It makes NO difference whatsoever if the AWD switch (All Wheel Drive) is turned on or not...it still ONLY holds back the rear wheels. "
Thanks for your opinions!
 

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You are correct - the EBS is only active with the rear wheels UNLESS you hold the override button, then the front wheels may activate the EBS also
 

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No, the ONLY way you have engine braking of the front wheels is if the machine has ADC (Active Descent Control) and you have that option selected on the right handlebar switch. Otherwise, its rear wheel EBS only.
 

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That's why I said MAY, because I wasn't sure - I never had a Polaris with EBS or ADC, so I wasn't speaking definitively - I was guessing.

Thanks for clarifying the issue.
 

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Yeah, took me a lot of years of riding them and experimentation to figure out the fine points of how they work latebird. There is a technique where you can "wedge" the front housing into engagement by backing up and keeping pressure on the driveline while shifting into forward gear to make the front stay locked in while going down hill. But that makes them VERY hard to steer and is probably not good for front housing components I'd guess. Not something you'd want to do much.
 

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Discussion Starter #6
Any thoughts about why, on a steep 2H EBS descent with no rear wheel slipping, the engine rpm would oscillate between 2100 RPM and 2500 RPM every 2 seconds?
 

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If it is steep and you need EBing you should be in 4wheel Low. Not high. I live in Colorado and EBing is a must at times. In 2W the front tires will turn free and the rear tires will slide. This is why you use 4W. We found that in 4W low you will not use brakes. You will need to use gas to accelerate because you are going WAY to slow. AS low as 2 or 3 MPH. Also use FULL 4W drive that way all 4 wheels will brake not just 3 wheels. That is with 2018 850 sportsman
 

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Discussion Starter #8
Thanks PoPo3. We're in SE Idaho, and there also are many steep, and slippery descents. I have to admit, that I don't see any difference between AWD and 2WD (rear) only. Of course, the goal is to keep those front wheels turning to help guide the descent. 2L would force the rear wheels to slip unless I goosed it hard, but 2H usually does the trick by just letting off the throttle. It was odd to see it go between 2100 and 2500 RPM (my wife's also). You'd think it'd just stay at one RPM and start either going faster (steeper) or lower (not as steep).
 

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What is happening is in 2W drive only your rear tires are braking and the front tires are free wheeling. Sort of like using the foot brake. When in 4W all tires are braking. The difference between high and low is the bike will go slower in low range. What we find is that in low range you may be going slower than you want so just give it a little gas to speed up the engine. When I'm following some one that is in high range that there brake light are coming on and off. In my case I'm not using the brakes at all but instead I have to feed the gas just ever so little to keep up with them.
 

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I would guess that the primary might me closing just a hair at that rpm, grabbing the belt for a split second and then slipping loose snd opening again.
 

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Discussion Starter #11
Thanks Snowchaser--good explanation!
PoPo3--Perhaps peruse the earlier threads here in this posting. Common opinion is that AWD vs 2WD doesn't act any differently on EBS descents. I agree vs my experience--I don't realize any differences between those two modes on steep and slippery (rounded rocks or scree) descents. I play between 2H EBS, goosing the throttle, and brakes. 2L does EBS brake better, but I have to goose it harder to keep the rear wheels moving.
 

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Thanks Snowchaser--good explanation!
PoPo3--Perhaps peruse the earlier threads here in this posting. Common opinion is that AWD vs 2WD doesn't act any differently on EBS descents. I agree vs my experience--I don't realize any differences between those two modes on steep and slippery (rounded rocks or scree) descents. I play between 2H EBS, goosing the throttle, and brakes. 2L does EBS brake better, but I have to goose it harder to keep the rear wheels moving.
I have only owned the bike since Sept 19 but have over 3,300 of experience. 2018 850 Sportsman.
I can tell by looking at the downgrade. If it is long the bike will start to run away and you will need to brake. Using low and all wheel drive the bike will not want to go out of control. The rear tires will not slide. You need to learn how it use the THROTTLE. You do not GOOSE the THROTTLE. You give it a little gas and HOLD it there. If you start running to fast you ease off the THROTTLE just a little. Learn to drive the ATV like you do your AUTO.
Children goose and let go. Drive like and adult not a child.
Last year I lost my rear brakes and had to drive back to camp over 40 miles and had two long steep downhill runs (8 miles for one) and had no problems. I only used the hand brake (front, the rear brake was gone) two times.
 

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Discussion Starter #13
Yep, my error. We don't goose it, we carefully use the throttle. In our group, we loosely use the word "goose" for controlling on descents. Try AWD and 2WD on hard descents and see if you really can tell a difference. My belief is that if you have EBS (do you instead have Active Descent Control?), you won't see a difference between AWD and 2WD, as neither will slow the front wheels on an EBS descent. Only the brake lever will slow/brake those two front wheels with EBS.
 

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Yep, my error. We don't goose it, we carefully use the throttle. In our group, we loosely use the word "goose" for controlling on descents. Try AWD and 2WD on hard descents and see if you really can tell a difference. My belief is that if you have EBS (do you instead have Active Descent Control?), you won't see a difference between AWD and 2WD, as neither will slow the front wheels on an EBS descent. Only the brake lever will slow/brake those two front wheels with EBS.
I have tried all ways. High, Low, 2W, 4W and all Wheel. I have tried taking it in and out of 4W and when you go out of 4W the back tires will start to slide. If it is steep you will need to use the brakes. 4L and all wheel drive is the only safe choice. I do not care how steep the grade I NEVER brake. I take that back. One time the ENGINE started to over rev and I need to brake once to bring the engine RPM back down. But that grade was to steep and way to long.
Just remember it is like driving your camper with a heavy trailer. DOWNSHIFT, DOWNSHIFT. Let the engine do the braking. I went over the newly finished Cotton Wood pass over the 4th to Tayler Reservoir in CO. and left the engine do the braking; and that way you will not have the brakes over heat.

Another thing with the vehicles with engine fan, not electric fan. On the up hill use LOW gear not DRIVE. If you can force the engine RPMs up the engine will not over heat. I laugh when I go by and see those FLAT-LANDER setting on the side of the road with there hoods up.
 

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I think you guys are using different terminology in describing what your talking about. EBS with 2wd or AWD brakes ONLY the rears.
EBS with 4x4/ADC is the ONLY way you get engine braking on all four wheels.
 

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Discussion Starter #16
Thanks--I have EBS with 2wd or AWD only. I was aware that ADC was the only way to get front wheel braking...unavailable on the 570 EPS, but standard on the 570 Touring Premium or 850 Premium. Polman500, thanks for clearing that up for us.
 
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