Giant 2020 Explore E+ Lowest Gear/Derailleur failure

ccguy

New Member
I've had a 2020 Giant Explore E+ 4 GTS for a year now. It has a Deore rear derailleur and a 11-36T cassette. Riding on the road, I tend to use the 6 or so highest gears with no shifting problems at all. I also go on mountain trails and have encountered serious shifting problems. Typically, it's been difficult shifting onto the 36T cog, and the chain often erratically skips between the 36T and next lowest cog. Several times, while trying to shift onto the 36T cog, the chain has bounced around and come off either the cassette or chainwheel, jamming itself against the frame. Last week I had a catastrophic failure. I was going uphill in a medium gear and encountered a steep incline on loose gravel. I was under full power and tried shifting into the lowest gear as the rear wheel began to spin. As the derailleur moved inward and the chain attempted to engage the 36T cog, the entire transmission exploded, breaking the chain and seriously bending its plates, bending and destroying the derailleur and bending the derailleur hanger.

I later straightened and realigned the derailleur hanger and bought a new 9 sp chain and Deore derailleur. I was not able to get the derailleur to properly engage the 36T cog, the same problem I had before. Then, I read the Deore spec sheet in detail (Yes, I should have done this first, but I thought I would be safe buying the same derailleur that came on the bike.) and it is certified only for a a 11-34T rear cassette, accounting for the inability of its top jockey wheel to clear and the chain to properly engage the 36T cog. Perhaps, Giant tweaked the installation of the derailleur on new bikes so that it would marginally work but that became compromised when the components showed some wear, or perhaps Giant had Shimano build a proprietary Deore derailleur that would work with a 36T cog. Or, maybe Giant simply blew it and assembled and sold a bike with mismatched components. I see that the 2021 Giant E+ has been reconfigured as a commuter bike and has a Shimano Alivio derailleur and a 11-36T cassette. The new 2021 Giant Roam E+ GTS seems similar to my Explore and is advertised as a gravel bike. It too has an Alivio derailleur and 11-36T cassette. The Alivio is cheaper than the Deore, so perhaps Giant was looking to save some money. Or, perhaps, they realized that the Deore did not work with a 36T cog.
Has anyone else encountered the same issues I faced with the Deore/36T combination? If so, how did you solve this?
Thanks for any feedback.
 

Stefan Mikes

Well-Known Member
Region
Europe
City
Brwinów (PL)
First of all: Is not your cassette already damaged? And the chainring? Have you only replaced the derailleur and the chain?
 

jabberwocky

Well-Known Member
Two things to watch for and adjust:

Upper limit screw: If the upper limit isn't adjusted properly, the chain can be pushed past the largest cog and into the space between the cassette and wheel spokes (I think this is what you are saying happened when it got jammed in the frame).

B-screw: This adjusts how close the derailleur cage sits to the cassette. There is an optimal position where the derailleur isn't too far away (which can cause soggy feeling shifting) or too close (which can cause the derailleur to actually touch the cassette which can be catastrophic while moving).

Park Tool has a nice overview guide here:

In addition, note that trying to dump a lot of gears while heavily loading the drivetrain can blow apart chains even when things are optimally adjusted. Shifting puts sideload on the chain, and they are only designed to take so much. Overload them and you can twist the plates apart, and then chain go kaboom.
 

FlatSix911

Well-Known Member
Region
USA
City
Silicon Valley
I've had a 2020 Giant Explore E+ 4 GTS for a year now. It has a Deore rear derailleur and a 11-36T cassette. Riding on the road, I tend to use the 6 or so highest gears with no shifting problems at all. I also go on mountain trails and have encountered serious shifting problems. Typically, it's been difficult shifting onto the 36T cog, and the chain often erratically skips between the 36T and next lowest cog. Several times, while trying to shift onto the 36T cog, the chain has bounced around and come off either the cassette or chainwheel, jamming itself against the frame. Last week I had a catastrophic failure. I was going uphill in a medium gear and encountered a steep incline on loose gravel. I was under full power and tried shifting into the lowest gear as the rear wheel began to spin. As the derailleur moved inward and the chain attempted to engage the 36T cog, the entire transmission exploded, breaking the chain and seriously bending its plates, bending and destroying the derailleur and bending the derailleur hanger.
I later straightened and realigned the derailleur hanger and bought a new 9 sp chain and Deore derailleur. I was not able to get the derailleur to properly engage the 36T cog, the same problem I had before. Then, I read the Deore spec sheet in detail (Yes, I should have done this first, but I thought I would be safe buying the same derailleur that came on the bike.) and it is certified only for a a 11-34T rear cassette, accounting for the inability of its top jockey wheel to clear and the chain to properly engage the 36T cog. Perhaps, Giant tweaked the installation of the derailleur on new bikes so that it would marginally work but that became compromised when the components showed some wear, or perhaps Giant had Shimano build a proprietary Deore derailleur that would work with a 36T cog. Or, maybe Giant simply blew it and assembled and sold a bike with mismatched components. I see that the 2021 Giant E+ has been reconfigured as a commuter bike and has a Shimano Alivio derailleur and a 11-36T cassette. The new 2021 Giant Roam E+ GTS seems similar to my Explore and is advertised as a gravel bike. It too has an Alivio derailleur and 11-36T cassette. The Alivio is cheaper than the Deore, so perhaps Giant was looking to save some money. Or, perhaps, they realized that the Deore did not work with a 36T cog. Has anyone else encountered the same issues I faced with the Deore/36T combination? If so, how did you solve this? Thanks for any feedback.
Sorry to hear about your shifting woes.
You may want to upgrade to a better spec derailleur that can handle a wide range 36T+ rear cassette.
Try an SLX or XT level MTB derailleur that is rated for a large rear cassette... stay away from anything below Deore.

1608255244826.png
 
Last edited:

ccguy

New Member
No, neither the cassette nor chainring was damaged. I'm very familiar with proper derailleur adjustment. I have three road bikes, all of which I've built up from the frame and routinely change components, including derailleurs, in addition to a Giant Road E+ and a Kona mountain bike. My road bikes all have Campy Record/Chorus or Shimano DuraAce components, and I have been generally disappointed with the low quality components Giant has put on the Explore E+. I would have preferred paying more for higher quality, more reliable components. I was initially going to get a better spec derailleur, but all of those that are currently sold are for 10 or 11 speed drivetrains and would only work if I also replaced the shifter/brake lever to an 10 or 11 speed model. I am aware of the incredible tension placed on the components when my chain and derailleur failed, and this may have happened in the best of circumstances on any bike. Still, I am unclear why Giant put a Deore derailleur, rated for a maximum rear cog of 34T, on their bike with a 36T cog.
 

jabberwocky

Well-Known Member
I do think the ratings are very conservative, and people routinely run derailleurs with much larger cassettes than they are rated for without issues. I've run Sram derailleurs rated for 34t max with 40-44t cassettes without problems on my MTBs. Hard to imagine that going from 34t to 36t goes from "works fine" to "explodes", but maybe that particular derailleur is particularly close?

Is there not enough b-screw adjustment to get proper clearance between the top pulley and the 36t cog? What does it look like with the b-screw backed all the way out?
 

ccguy

New Member
Good question. There is some clearance when the b-screw is fully out, but less than I am comfortable with, given the b screw setting on my other bikes. I'm guessing that this close clearance may be what accounts for the difficulty shifting onto the 36T cog.
 

jabberwocky

Well-Known Member
Could try a longer b-screw. Might check the derailleur you replaced and see if it came with a longer b-screw as well. Back in the old hack-together-a-1x10 days, people often put longer b-screws on to move the derailleur a bit further out (or bought aftermarket links like the wolf tooth goatlink).

Actually, Wolf tooth does make the roadlink now, which is designed to let you run wide range MTB cassettes on road drivetrains. Maybe worth a look?
 

fooferdoggie

Well-Known Member
it sounds like you needed to adjust the derailed since it was having trouble shifting so that was a problem then shifting under load too
 

john peck

Well-Known Member
First of all: Is not your cassette already damaged? And the chainring? Have you only replaced the derailleur and the chain?
Cassette being the operative word, The pins that hold a cassette together are prone to stretch especially on ebikes.
This can distort one, & eventually loosen the whole cassette. Get a freewheel they last so much longer.
 

fooferdoggie

Well-Known Member
Cassette being the operative word, The pins that hold a cassette together are prone to stretch especially on ebikes.
This can distort one, & eventually loosen the whole cassette. Get a freewheel they last so much longer.
my Shimano cassette is one piece you cant remove the pins so its s one unit now.
 

jabberwocky

Well-Known Member
Cassette being the operative word, The pins that hold a cassette together are prone to stretch especially on ebikes.
This can distort one, & eventually loosen the whole cassette. Get a freewheel they last so much longer.
I've never heard of this happening. I've gone through dozens of cassettes over the years and never had one with a machined carrier develop even a hint of play. Cheaper ones that are just a pinned together stack of cogs can't move even if the pins loosen because they are still mated to the freehub splines.

Does anyone even make freewheels for modern drivetrains? In my 2 decades of cycling, the only time I've even seen a freewheel was on very old or very cheap bikes.

Switching to a freewheel would require a new rear wheel (or at least rebuilding the existing one with a new hub). If hes gonna spend that kind of time and money he may as well just upgrade the drivetrain to a higher end 10 speed group that works with wider range cassettes.
 
B

BarryS

Guest
I have worked on Bikes since I was 15. Both Professionally and out of My garage . You need to eliminate things . 1: Get a New Hanger 2: Check the torque on the chain Ring and the cassette. It;s essential you have that as close to exact spec as possible. 3: Links in the chain 4: H and L Screws 5: The B screw never needs messing with unless someone messed with it . The H and L have nothing to do with how a Bike shifts . They are limit screws that align the chain at both ends so it doesn't fall off . 6: Last is a simple loosen teh cable and snug it up.

Work on bikes is pretty simple . But not following a pattern can mess everything up. You're likely talking about a Small adjustment .

As for Giants replacing components . It was either the older ones went up in price or they couldn't get any when they needed them :
 

Stefan Mikes

Well-Known Member
Region
Europe
City
Brwinów (PL)
my Shimano cassette is one piece you cant remove the pins so its s one unit now.
Foofer yes you can dismantle the cassette but of course there are no pins there :) My brother has dismantled cassettes on my both e-bikes using a Shimano cassette tool and replaced just the worn cogs. For instance:

1608307446834.png

It's far cheaper to replace two cogs than the entire cassette.
 

reed scott

Well-Known Member
Cassette being the operative word, The pins that hold a cassette together are prone to stretch especially on ebikes.
This can distort one, & eventually loosen the whole cassette. Get a freewheel they last so much longer.
John, Can you please point me to some info on freewheel vc cassette or maybe you can explain it for me. This is one of those 'dark' areas of bikeology that I don't understand. Thanks.
 

jabberwocky

Well-Known Member
John, Can you please point me to some info on freewheel vc cassette or maybe you can explain it for me. This is one of those 'dark' areas of bikeology that I don't understand. Thanks.
Freewheels combine the ratchet mechanism with the gear cluster, and the whole thing threads onto the hub. Freehubs have the ratchet mechanism in the hub, with some sort of splined body that the cassette slides onto.