Inpd

So I've been looking a lot at bikes and I've noticed that quite a few road bikes (particularly flat bars) are now sporting MTB components particularly derailleurs.

I'm not sure why this is? Cost?

But this raises the question of how to compare groups sets from different platforms. Everyone knows a 105 RD is better than a Tiagara which is better than a Claris etc.. But how does one compare a 105 RD and a Alivio RD?

veloboy971

Well the reason flat bar road bikes would be utilizing mtb components would be due to the shifters needing to be flat bar shifters vs STI shifters. Cable length pull differs among different group sets and since the cable pull must be consistent between derailleur and shifter for indexed shifting that would explain why you couldn't run flat bar shifters with a derailleur designed for a certain STI shifter.

Inpd

But quite a few flat bar road bikes still have road bike FD/RD etc so I'm not sure that's it.

MileHighMark

Many flat-bar bikes are equipped with larger cogs, and MTB derailleurs are compatible with larger cogs. MTB derailleurs--especially the clutch type--are also better at reducing chain-slap.

Inpd

That's what I thought originally. But this Fuji (Fuji Bikes | ROAD | ENDURANCE SERIES | SPORTIF 2.3) for example has a 11-32 cassette which is about as big as I've seen and supports a Claris RD.

MileHighMark

Shimano's long-cage road mechs are usually good up to 32t. I was referring to 34t and even 36t cogs. There are, of course, exceptions such as this:



Cassette is a 10-42 (11-speed MTB), rear derailleur is a SRAM 1x road model, and the shifters are SRAM's hydraulic drop-bar levers (aka, brifters).

Jeremy_S

Shimano MTB gear goes like this.
1. XTR
2. XT
3. SLX/Deore (depends on who you ask)
4. Never used anything less than Deore so don't know, probably Altus or something but prices aren't so unreasonable you can't run Deore or XT. I've always been a big fan of XT, similar to Ultegra in quality and refinement I believe.

pacificaslim

10-42?! Nice Mark.

I run a fairly ridiculous combination of Campy shifters and front derailleur with Shimano mtb rapid rise rear derailleur. I do so for the aforementioned reason of needing a larger cassette capacity than campy rear derailleurs can handle. And for what it's worth, the back-asswards shifting of the rapid-rise low-normal rear derailleur is brilliant for cyclocross type riding in the trails because if I come around a corner to find a sudden uphill, I can hit the lever on the shifter down and jump up like four cogs in one motion and jam up the hill! Much faster than having to hit the lever inwards multiple times to do the same shift if I had a normal derailleur.