Rear Deraillier Replacement

Discuss light weight issues concerning road bikes & parts.
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Jacksoneaker
Posts: 11
Joined: Mon Jul 02, 2018 4:09 am

by Jacksoneaker

My 105 5800 RD got totaled tonight. Going to end up with a new hangar and need a new mech. The question is: replace with another 5800 unit, or upgrade RD to r7000 series?

The only difference I know of is the “Shadow” placement, and I can find the 7000 for $56 and the 5800 for $40. Curious if it is worth looking into the new one :)

Thanks

by Weenie


ooo
Posts: 629
Joined: Sat May 21, 2016 12:59 pm

by ooo

r7000 should have the same price as 5800:

https://www.starbike.com/en/shimano-105 ... erailleur/
https://www.starbike.com/en/shimano-105 ... 11-speeds/

r7000 for $56 is too much, if you want to upgade get Ultegra:

https://www.starbike.com/en/shimano-ult ... erailleur/

r7000 miss cable sealing nose cover (tongue), comparing to 5800:

viewtopic.php?f=3&t=150980&p=1436022#p1420724
'

2lo8
Posts: 470
Joined: Thu Mar 31, 2016 10:32 am

by 2lo8

My impression is that RD-R7000 is worse quality than RD-5800. It's worse quality than even a 10 year old "shadow" SLX (105 equivalent). Compared to RD-5800/SLX, the inner parallelogram link and A-knuckle are plastic, and the pivot bolt on the R7000 is sloppier than the SLX. The quality of 105 is definately going down.

Edit: Even the new Ultegra is a cost cutting exercise. Both 9000/6800 used a carbon A-knuckle and aluminum inner link. R9100 still uses a carbon A-knuckle and aluminum inner link, but those are also plastic now on R8000 according to the tech docs.
[6.6kg of no carbon fiber]
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Bigger Gear
Posts: 361
Joined: Fri Mar 27, 2009 6:58 pm
Location: Wet coast, Canada

by Bigger Gear

2lo8 wrote:
Fri Oct 19, 2018 2:55 am
My impression is that RD-R7000 is worse quality than RD-5800. It's worse quality than even a 10 year old "shadow" SLX (105 equivalent). Compared to RD-5800/SLX, the inner parallelogram link and A-knuckle are plastic, and the pivot bolt on the R7000 is sloppier than the SLX. The quality of 105 is definately going down.

Edit: Even the new Ultegra is a cost cutting exercise. Both 9000/6800 used a carbon A-knuckle and aluminum inner link. R9100 still uses a carbon A-knuckle and aluminum inner link, but those are also plastic now on R8000 according to the tech docs.
I agree, I found the R8000 rear derailleur to be very sloppy even from new. Once the chain tension is on it the slop goes away but still I was disappointed. I actually hoarded a couple of DA9000 rear derailleurs as spares and replaced the 8000 with one of them. My experiece with the DA9100 rear derailleur has been OK but one thing I don't like is the excessive chain slap when hitting larger bumps. I guess the Ultegra with clutch would solve that.

Anyway, to the OP I say just get a 5800 or 6800 rear and be done with it.

Jacksoneaker
Posts: 11
Joined: Mon Jul 02, 2018 4:09 am

by Jacksoneaker

That’s what I was leaning towards, just wanted to make sure I wasn’t missing some big advantage that wouldn’t show on a spec sheet. Thank you for the help.

Jacksoneaker
Posts: 11
Joined: Mon Jul 02, 2018 4:09 am

by Jacksoneaker

2lo8 wrote:
Fri Oct 19, 2018 2:55 am
My impression is that RD-R7000 is worse quality than RD-5800. It's worse quality than even a 10 year old "shadow" SLX (105 equivalent). Compared to RD-5800/SLX, the inner parallelogram link and A-knuckle are plastic, and the pivot bolt on the R7000 is sloppier than the SLX. The quality of 105 is definately going down.

Edit: Even the new Ultegra is a cost cutting exercise. Both 9000/6800 used a carbon A-knuckle and aluminum inner link. R9100 still uses a carbon A-knuckle and aluminum inner link, but those are also plastic now on R8000 according to the tech docs.
I just found the other thread where you were talking about the construction. It’s a shame that they seem to have taken durability down a step, especially in the “tank group” that 105 was always heralded to be.

2lo8
Posts: 470
Joined: Thu Mar 31, 2016 10:32 am

by 2lo8

Bigger Gear wrote:
Fri Oct 19, 2018 6:07 pm
2lo8 wrote:
Fri Oct 19, 2018 2:55 am
My impression is that RD-R7000 is worse quality than RD-5800. It's worse quality than even a 10 year old "shadow" SLX (105 equivalent). Compared to RD-5800/SLX, the inner parallelogram link and A-knuckle are plastic, and the pivot bolt on the R7000 is sloppier than the SLX. The quality of 105 is definately going down.

Edit: Even the new Ultegra is a cost cutting exercise. Both 9000/6800 used a carbon A-knuckle and aluminum inner link. R9100 still uses a carbon A-knuckle and aluminum inner link, but those are also plastic now on R8000 according to the tech docs.
I agree, I found the R8000 rear derailleur to be very sloppy even from new. Once the chain tension is on it the slop goes away but still I was disappointed. I actually hoarded a couple of DA9000 rear derailleurs as spares and replaced the 8000 with one of them. My experiece with the DA9100 rear derailleur has been OK but one thing I don't like is the excessive chain slap when hitting larger bumps. I guess the Ultegra with clutch would solve that.

Anyway, to the OP I say just get a 5800 or 6800 rear and be done with it.
One of the advantages of the "shadow" design (really any single sprung pivot with concentric jockey, like Suntour GTs and SRAM) is that slop in the pivots matters less because the derailer movement is so rigidly defined. I think it's slightly less affected by a bent hanger because the upper pivot doesn't actually pivot in use and there's no pulley offset to give you different jockey positions in the big ring and small ring, so less of that being able to shift in one ring but not the other. It's a shame that Shimano took the opprotunity to cut costs at the same time they updated the design though. It works well enough, but it would have been even better if they actually kept construction quality up though.
[6.6kg of no carbon fiber]
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ooo
Posts: 629
Joined: Sat May 21, 2016 12:59 pm

by ooo

Shimano offers 2 durable road shadow RD: 1) Dura-Ace for short cage SS; 2) Ultegra RX for long cage GS:
RD-RX800 weight 248g like 105 (RD-5800 250g), priced like Ultegra (RD-6800/RD-R8000 + 12€)
May be clutch can be removed to save weight?

old vs new 105/ultegra components comparison (mixed info from different catalogs, shimano do not list them in one catalog)

Image
Last edited by ooo on Sat Oct 20, 2018 11:38 am, edited 1 time in total.
'

2lo8
Posts: 470
Joined: Thu Mar 31, 2016 10:32 am

by 2lo8

I do not think the RX800 tech docs are accurate. The materials are different in different versions of the tech docs. I think I see the inner link is also plastic on the RX800. I don't not have a R8000 to check that the inner link is plastic, but some pictures of RX800 show that the spring pin is held in by melting part of the inner link to trap the pin, same as the plastic link on R7000. On the MTB derailers, the A-knuckle is GFRP or CFRP for clutch models as far as I can tell. I don't think the Ultegra clutch derailer uses aluminum is those do not. This is speculation though.
[6.6kg of no carbon fiber]
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ooo
Posts: 629
Joined: Sat May 21, 2016 12:59 pm

by ooo

2lo8 wrote:
Fri Oct 19, 2018 8:47 pm
One of the advantages of the "shadow" design (really any single sprung pivot with concentric jockey, like Suntour GTs and SRAM) is that slop in the pivots matters less because the derailer movement is so rigidly defined.
May be this rigid construction requires more durable cage connection, there is video about RD-R7000 cage play after 2 months:
https://www.youtube.com/watch?v=NFnxRfPKmPM
https://www.youtube.com/watch?v=Ov0t_hgQkD0
2lo8 wrote:
Sat Oct 20, 2018 9:30 am
I do not think the RX800 tech docs are accurate. The materials are different in different versions of the tech docs. I
It may be a mistake, I don't have it in hands to check it. Materials info was updated 47 days ago:

RD-RX800:
3.0 catalog 2018-09-03 Inner link Material=Aluminum Finish=Plated ; P-Axle Material=Steel Finish=no
2.8 catalog 2018-07-04 Inner link Material=GFRP Finish=no ; P-Axle Material=Aluminum Finish=Plated
2.6 catalog 2018-07-01 Inner link Material=GFRP Finish=no ; P-Axle Material=Aluminum Finish=Plated
2.5 catalog 2018-05-26 Inner link Material=GFRP Finish=no ; P-Axle Material=Aluminum Finish=Plated
2.5 catalog 2018-05-15 Inner link Material=GFRP Finish=no ; P-Axle Material=Aluminum Finish=Plated
2.3 catalog 2018-05-02 Inner link Material=GFRP Finish=no ; P-Axle Material=Aluminum Finish=Plated

RD-RX805:
3.0 catalog 2018-09-03 Inner link Material=GFRP Finish=no
2.8 catalog 2018-07-04 Inner link Material=Steel Finish=GFRP
2.6 catalog 2018-07-01 Inner link Material=Steel Finish=GFRP
2.5 catalog 2018-05-26 Inner link Material=Steel Finish=GFRP
2.5 catalog 2018-05-15 Inner link Material=Steel Finish=GFRP
2.3 catalog 2018-05-02 Inner link Material=Steel Finish=GFRP
2lo8 wrote:
Sat Oct 20, 2018 9:30 am
some pictures of RX800 show that the spring pin is held in by melting part of the inner link to trap the pin, same as the plastic link on R7000
Did you mean this part?

R7000 vs RX800:
Image
Image

RX800 vs R8000 vs R9100
Image
Image
Image
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by Weenie


2lo8
Posts: 470
Joined: Thu Mar 31, 2016 10:32 am

by 2lo8

I think the new construction is just cheap. When I say rigidly defined, I mean that the upper jockey will only ever move across a single line. It does not deviate because there are no springs balanced against each other and with no offset it doesn't matter how much chain wrap is used by the chainring. One spring only works against cable tension, the other spring only works against chain tension. On the old design, the upper jockey pulley could move around due to chain slap from going over bumps and which chainring you were using because the A-spring was working balancing the B-spring, and the offset would move the pulley in a different position when the chain wrap was different.

All the tech docs before 2.8 show GFRP for the inner link. 3.0 it was changed for some reason. The picture of the spring pin makes it look like GFRP. Yes, that is the spring pin I was talking about. The plastic is melted back over the pin to trap it there. For aluminum is it press fit with a cross stamping, but any deformation should be barely noticable.
[6.6kg of no carbon fiber]
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Your one-stop source for information and reviews on cheap eBay bike junk.

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