Which Shimano derailleur??
la pédale
Posts: 4
Can anyone help? I want to replace my smashed Shimano rear derailleur with any identical unit. The part number is rd-m786-VIA but I can only find rd-m786 SGS or SG (for long or short cage) online. Does anybody know what the VIA designates?
Cheers
Cheers
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I have never heard of the 'VIA' designation and can't find anything on the web.
What bike is it fitted on? (Make, model & year.)“Life has been unfaithful
And it all promised so so much”
Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Giant Revolt Advanced 2 2019 ¦ Giant Toughtroad SLR 1 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 20090 -
The body doesn’t have the cage length on it, not sure what VIA means but that could still be either cage length.Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.0
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Curious! It’s fitted to a La Pierre.0
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I can't tell for certain, but the assignation "VIA" may mean that it is a derailleur made for LapIerre. With the rest of the designatory letters so similar, the vast majority of the derailleur will be the same. All you have to decide is whether to get a long or short cage. The best thing would be to look at the derailleur manufacturer's recommendation.
However, there is a formula for working out what cage you need and it depends upon the number of teeth in the range of gears. The mech arm has to be able to cope with a wide range or a small range to manage the slack in the chain when you are on small gears compared to when you are on big gears.
I am not 100% certain of the exact formula, someone else please chip in if you know for sure.
The formula is (big front + big rear) - (small front + small rear) = the tooth range
The formula was contrived when many bikes had a triple set up, but it works for 2x and 1x.
On a 2x with a 24/36 driving an 11-36 you'd get (36+36) - (24+11) = 72-35 = 37
On any 1x it is just the difference between the rear gears, so 11-42 would be 31.
What to do with this info?
Just going from memory here (so could be a bit off and it varies between makes/models) a long cage will cover about 45 teeth, a medium 39 and a short around 33.
On the examples above, you'd need a medium cage for the 2x and a short cage for the 1x.
But you only have a choice of long or short. If you are on a 1x, go safe because you can't avoid using all the rear gears. On a 2x and a 3x, you could go tight a bit because you can avoid the extremes. You can also adjust your chain length too to do some fine tuning.0 -
la pédale wrote:Curious! It’s fitted to a La Pierre.
Which model and which year?“Life has been unfaithful
And it all promised so so much”
Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Giant Revolt Advanced 2 2019 ¦ Giant Toughtroad SLR 1 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 20090 -
Thanks Steve, it could be La Pierre specific.
Sounds uncommon. I’ll seek advice from shimano.0 -
A few bike manufacturers have certain components de-badged and put on bikes as "blahblah" specific.la pédale wrote:Thanks Steve, it could be La Pierre specific.
Sounds uncommon. I’ll seek advice from shimano.
Specialized had DTSwiss hubs and Avid brakes "Customised for Specialized" for years.Basically stock components without the decals.
If you could post a photo I'm sure someone will identify it for you.Chances are it with be an SLX/XT/XTR etc depending on the model of your bike.0 -
RD-M786 is Deore XT.
Post a couple of pictures, including one showing the writing on the rear of the derailleur. That will be best way to help someone identify it.
Once again, what model and year bike is it?“Life has been unfaithful
And it all promised so so much”
Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Giant Revolt Advanced 2 2019 ¦ Giant Toughtroad SLR 1 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 20090 -
Just found this:
“"VIA" ("Vehicle Inspection Authority") is stamped on all Shimano parts. It is an official approval stamp used to certify parts of Japanese vehicles – including bicycles. This mark signifies compliance with certain quality standards and is similar to the "UL" (Underwriters Laboratories) mark.”
It’s nothing to do with the actual derailleur designation.
Just measure the distance between the jockey wheel bolts to determine if your mech is short or long cage.“Life has been unfaithful
And it all promised so so much”
Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Giant Revolt Advanced 2 2019 ¦ Giant Toughtroad SLR 1 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 20090 -
Usually written as required capacity = (Big front - small front) + (Big rear - small rear) but the result is the same.steve_sordy wrote:The formula is (big front + big rear) - (small front + small rear) = the tooth rangeCurrently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.0 -
JBA wrote:Just found this:
“"VIA" ("Vehicle Inspection Authority") is stamped on all Shimano parts. It is an official approval stamp used to certify parts of Japanese vehicles – including bicycles. This mark signifies compliance with certain quality standards and is similar to the "UL" (Underwriters Laboratories) mark.”
It’s nothing to do with the actual derailleur designation.
Just measure the distance between the jockey wheel bolts to determine if your mech is short or long cage.
Was just about to post that every Shimano component I've ever handled has a VIA stamp or sticker somewhere on it.0
