Shimano 9-10sp interchangeability

[NickR]

https://farm1.staticflickr.com/888/40737031504_274183cb6c.jpg (https://flic.kr/p/254MWd9)DSC00618-970x647 (https://flic.kr/p/254MWd9) by ntrodriguez (https://www.flickr.com/photos/18148125@N07/), on Flickr

Pulled the trigger and will mostly be used for commuting. Question I have is can i use my 5700 group, swap out the RD for a 9 speed era (medium or long cage) and slap in a 11-34 10sp cassette? Will shifting suffer?

Eventually will get the r7000 when its' released since i can still extend the life of my 10sp wheels and have climbing gears.

Thanks,

Nick

[jtbadge]

That should work! I have a similar setup planned for the RB-1 I just bought. 8 speed XT derailleurs, 10 speed shifters, cassette, and chain.

[dddd]

I did just that recently on a Bianchi Cyclocross bike.

As long as the 9s derailer and cassette are matched in terms of max. cog size, it does maintain a familiar very high level of shifting precision.

Jacking any derailer's B-tension screw to clear larger than recommended cogs is another story. This increases the distance between the top pulley and the smaller cogs as well, which is where shifting might suffer if the particular bike's cable routing features less than the straightest-possible path, and/or if the chain is worn, cabling aged, etc.

But on the Bianchi, the 11-34t 10s cassette was within the max. cog size limit of the Maga-9 XT derailer, and the shifting was excellent from the get-go.

Derailers intended for fewer # of speeds and narrower cog spacing typically have less float in their top pulley, which might be worth addressing if the shifting performance feels sub-optimal.
I have on occasion switched out the top and bottom pulley in cases where some combination of parameters was causing sluggish, unresponsive shifting.
I have also modified (shortened) the ceramic bushing in a floating top pulley to achieve a similar result, by sliding the bushing over a nutted bolt and spinning the end of the bushing against the bench grinder's wheel. The cage plate spacng is also slightly tightened by doing this, which better controls the narrower chain.

Here's a 5s Simplex derailer with narrower, non-floating pulleys, feeding 9s chain onto the freewheel, which offers up some of the most responsive friction shifting I've ever experienced.
This after I also adjusted the derailer's A-B (cage pivot and mounting pivot) spring-tension balance for a tighter chain "gap" between pulley and (13-24t) cogs.
The smaller freewheel plays well with the bike's old 52-36t chainrings for a decently-broad range, it all works better than I expected in the foothills.
https://c1.staticflickr.com/9/8097/8386103582_4997241622_z.jpg

[GOTHBROOKS]

we would put long cage 9spd xtr rear ders on old dudes roubaixs with 7800 shifters so they could run larger gears all the time. worked great for them.

[Gummee]

The answer from 7-9sp was 'everything works with everything*'

The exceptions are mtn front derailleurs with road shifters and 7400 series D/A which only worked with 7400 series D/A

Once they went 10sp mtn and 11sp road, things stopped being cross compatible.

M

[zzy]

I'm currently running a long cage 9sp XT mech with a 10sp road set up - works flawlessly.

[NickR]

Thanks guys for the info, looks like I’ll be going this route long term.

[GregL]

Piling on: our tandem uses Ultegra 6603 brake/shift levers with an XT 761 rear derailleur. Even with the long cable runs, the shifting is perfect.

Greg

[dddd]

The answer from 7-9sp was 'everything works with everything*'

The exceptions are mtn front derailleurs with road shifters and 7400 series D/A which only worked with 7400 series D/A

Once they went 10sp mtn and 11sp road, things stopped being cross compatible.

M

Another exception would be running sub-8s derailers with 8s shifters/cassettes.
Many times the indexing up to the largest cog would not remain accurate, would not move quite far enough inward, despite backing off the lo-limit screw and adjusting the cable. And it wasn't a matter of the derailer reaching the end of it's inward travel.
I've had to deal with several rider's bikes where this substitution for the correct part didn't work flawlessly, giving cred to the "integrated 8 SIS" designation on the officially-designated parts.
This was subtle enough that some might assume that the setup and cabling was perhaps substandard, yet an 8s derailer always fixed it.
The same would of course apply when using those same derailers with 9 or 10s cassettes, except worse.

[Gummee]

Another exception would be running sub-8s derailers with 8s shifters/cassettes.
Many times the indexing up to the largest cog would not remain accurate, would not move quite far enough inward, despite backing off the lo-limit screw and adjusting the cable. And it wasn't a matter of the derailer reaching the end of it's inward travel.
I've had to deal with several rider's bikes where this substitution for the correct part didn't work flawlessly, giving cred to the "integrated 8 SIS" designation on the officially-designated parts.
This was subtle enough that some might assume that the setup and cabling was perhaps substandard, yet an 8s derailer always fixed it.
The same would of course apply when using those same derailers with 9 or 10s cassettes, except worse.

I didn't have that problem when I went from 7sp to 8sp, but that doesn't mean no one did.

M

[Bradford]

Get an M750 long cage rear derailleur, there are always some on ebay. I run 4 of them with 10 speed triples, three going up to 32 and one going up to 34.