hevysrf

I'm trying to help a friend with a newly acquired 2016 Scott bike, 2 x 11, equipped with Shimano 105 and a FD 5800 front derailleur. Drop bar, integrated brake and shifter.

Can someone explain why there are 4 shifter positions when there are only 2 chainwheels?

nathand

The additional two positions are "trim" positions, sometimes useful when the chain is in the extreme opposite positions (larger front and largest rear, or smaller front and smallest rear). This is known as cross-chaining and in general you shouldn't do it, but Shimano provides the trim positions in case you want to use those positions without the front derailleur rubbing the chain.

hevysrf

Would the first position be for small front and large rear?
Second for small front and small rear?
Third for large front and Large rear?


Would changing the brake/shifter allow for just two positions?

Maelochs

If set up properly ... two positions per ring, which allows the derailleur to be set up tightly while not hitting the chain .... I usually find that I use low trim for the lowest three cogs (biggest three cogs) on each ring, though the positions work for the first 8 cogs or so.

prj71

Front derailleur how-to: shifting and trim

cxwrench

Why would you want to get rid of a shifter that reduces chain rub on the derailleur and allows more gear combinations to be used? Makes no sense.
Going from big chainring down...when you shift up to the big ring the derailleur is in high position. This is used then in the smaller rear cogs. If you slow down and shift to larger cogs you might get chain rub, so use the trim click. Next click moves the chain to the small ring. This position is used w/ middle and smaller cogs. One more click moves the derailleur all the over to the left and is used w/ the large cogs.

hevysrf

Thanks

Iride01 

You are welcome. However no one has any idea if any of the replies here led you to any conclusion for your original question or what provoked the "thanks".

hevysrf

Well between the video and text descriptions, I better prepared to help someone who is even less familiar will derailleurs than I am. Kind of disappointed that "Indexed" shifting needs trim.

I have a new cable, a.5mm shim for low end stop, a 2mm shim to set height and a barrel adjuster to fine tune, will try to install new cable and adjust as soon as schedule permits.

My last new derailleur bike had 10 speeds and down tube friction shifters." Halco" was the brand, no where near as nice as my friends Raleigh "Grand Prix", but a decent ride for department store steel.

prj71

Why are you disappointed? Do you like hearing the chain rub on the front derailleur?

https://www.bikeradar.com/advice/ski...ear-on-a-bike/

Maelochs

It doesn't. You can ride with the chain hitting the derailleur cage if you like.

The deal is this---in the old days, you needed to manually trim the front derailleur, and even then, often couldn't use the lowest (biggest) cog with the big ring, or the smallest cog with the smallest ring. This meant that you "12-speed" (or 14- or 16- or 24-speed) was in fact a few gears less. Add in overlap (gears on the big ring with almost the same ration with gears on the small) and it took two rings and six cogs to get seven usable ratios.

Nowadays, you can use 22 ratios with an 11-speed cassette and a double ring. There will be a couple which are close, but you have at least a few more usable ratios, and greater flexibility. There are some hills I ride where I might drop to the small ring at the bottom or I might not .... and some days i am more ambitious than I am fit, and I need to go all the way down to the biggest cog/big ring combination. And I can, without hurting anything.

(The idea is that a front shift (even with today's marvelous derailleurs) takes more time, and thus costs more momentum/energy, than a rear shift, and on a hill, the speed you lose is lost in a hurry .... so it s better not to have to shift up front when the hill is really hard.)

The fact that I have four derailleur positions is a Feature, not a drawback. it allows me both very precise shifting and allows me to shift under load, while also allowing me to make use of the full range of my transmission.

Gonzo Bob

Not all front indexing needs trim. I have a triple on my old MTB and use SRAM MRX Comp shifters (with Shimano Deore derailers) and the front shifter has exactly 3 positions - no trim possible. But once adjusted, it works great with no front derailer rub in any gear combination.

But I'm a lot less familiar with road systems. I had integrated brake/shifter levers on one of my road bikes for a while a long time ago (Ultegra 8) but converted it to triathon/TT and swapped it to bar-end where the front is friction. My other three road bikes have always been downtube or bar-end with friction front.

Maelochs

Triples tended to have wider cages, and MTB even more so. I had MTB FD on a touring triple---cage must have been half an inch wide. I was running 3x6 but I probably could have covered 3x11 with that thing.

I also had a 3x8 Shimano Deore set-up on an MTB and while it had index, it also offered index at the flip of a switch. The Index setting might have been fine, but on a dirt bike, who wants even potentially finicky? Sadly, I will never know if I could have had the front on "index" .....


Life is fill of tragedy.

Gonzo Bob

Where are you measuring that? My 6,7-speed road double front derailers measure ~13mm between cage plates, the 9-speed road double measures ~12mm, and the MTB triple measures ~14mm.

genejockey 

14 mm is 0.55".

Gonzo Bob

D'oh! You're right! Not sure how I so misunderstood the dimension Maelochs used. Guess I didn't think about it critically enough. My 9sp road double is 12mm wide which is 0.47" which also rounds to 1/2 inch, so I guess a lot of front derailers (both double and triple) are 1/2" wide.

Maelochs

Yeah, I never actually measured, and trying to picture it it seems like it might have been wider than half an inch .... it was noticeably wider than all the other double- and triple derailleurs I had seen until that time. My whole point was that that particular MTB derailleur was exceptionally wide, and it seems most MTB derailleurs were rider than road derailleurs because they were designed for occasional cross-chaining, and also for getting bashed around, clogged with mud, etc, which made extreme precision a drawback, where on the road in a relatively clean environment, a narrower cage led to quicker shifts.

Gonzo Bob

[QUOTE=Maelochs;22269100]Yeah, I never actually measured/QUOTE]
And how big was that fish you didn't quite land?
Just givin' ya' ****, dude. Have seen your responses on other threads and love your contributions to the forums.

Random11

Thanks very much for posting this video. I'd heard of derailleur trim, but didn't know how it worked. I asked another rider who tried to explain it to me, but I'm not sure he understood it. He never mentioned anything about cross-chaining, and as far as I could tell, it applied to both front and rear derailleurs. So I asked my LBS about it and the guy I asked didn't know anything about it. He'd never heard of trim. So I set the idea aside. But after watching the video last night I tried it out on my bike this morning. Now I see how it works! Thanks for the instruction. Very informative!

cxwrench

Unbelievable. No wonder bike shops have such ****** reputations.

prj71

I'm guessing that was a 7 or 9 speed cassette.