Why do SRAM rear derailleurs not have a parallel movement

[GaryvdM]

My SRAM rear derailleur (Rival 22 circa 2016) has a non parallel movement. When it is in the lowest gear, the cage and pulley sprockets align with the cassette sprockets, but when it's in the highest gear, it is very miss aligned.

 

 

I measured the distance between the pivot points. I got 48mm and 49mm, which would explain the non parallel movement.

 

 

Question 1: What was the design reason for this?

Question 2: Do I need to get the alignment of the derailleur hanger checked? The gears shift easily. I'm just worried about drive chain efficiency.

[madmarc]

That alignment in the 2nd pic doesnt look right - maybe its the angle of the pic, but tha cage looks like its skew. Check your hanger and the cage to make sure its not bent. If you set the upper and lower screws they should align perfectly.

[Headshot]

I doubt that's the way its meant to be. Could be a bent hanger, One way to straighten a hanger is to leave the wheel on and remove the chain and derailleur. Then use a shifting spanner to gently bend and align the hanger using the cassette and front rings as a reference. Works a treat. 

[dirtypot]

I'd suggest using a derailleur hanger alignment guide.  Far more accurate.  Your LBS should have one and can do it for you.

 

 

[Edition 507]

I think that derailleur is bent and beyond repair.

 

You will have to buy yourself a new bike!

[GaryvdM]

Ok. Thanks. I'm going to build myself one of these:

 

[Headshot]

I'd suggest using a derailleur hanger alignment guide.  Far more accurate.  Your LBS should have one and can do it for you.

Believe me, a little bit of patience and a shifting spanner as a lever will work just as well. 

[dirtypot]

Believe me, a little bit of patience and a shifting spanner as a lever will work just as well. 

 

I know, and it's what I've always used before, but after playing with the DAG 2.2 for a while now I can't imagine ever going back.  It's so precise and takes all of the guesswork out completely.  

[Bateleur1]

Ok. Thanks. I'm going to build myself one of these:

 

 

I nominate this as post of the month.

[VolkAdik]

Brilliant vid, project for this weekend

[David Marshall]

From the pic it looks more like limit screw adjustment than derailleur hanger.  If it is the hanger you really need a tool to align it.  In the days of 8 and 9 speeds you could get away with a "by the eye and hand" alignment but the tolerance on 10 speed and up are so fine that a tool is a must.  I have the Shimano one which is a dream to use but the cost is a bit high for home use.  If you are not into DIY the cheap ones work (X tools, Cyclo tools etc)

[Pah Bear]

Ok. Thanks. I'm going to build myself one of these:

 

Do it. Did and works a treat.

[Andreas_187]

It's probably the hanger, don't bother trying to straighten it. Learn from my mistake, my hanger bent and then it snapped which destroyed my derailleur as is went over the cassette and between the wheel and the frame... Oh, and it cracked the frame as well.

[GaryvdM]

Made my hanger alignment tool today.

 

 

Hanger was perfectly straight in the horizontal plain, and a little out in the vertical plain (was out by 4mm), which I have now fixed. Differences between measurements are now all less than 1mm.

 

The problem still exists. The cage is aligned when it's in the lowest gear, but very miss-aligned in the highest gear.

[David Marshall]

H limit screw?

[100Tours]

Made my hanger alignment tool today.

 

IMG_20180519_100922.jpg

 

Hanger was perfectly straight in the horizontal plain, and a little out in the vertical plain (was out by 4mm), which I have now fixed. Differences between measurements are now all less than 1mm.

 

The problem still exists. The cage is aligned when it's in the lowest gear, but very miss-aligned in the highest gear.

 

Great investment to have built this tool - they can be really useful.

 

Having said that I think the SRAM RD just works like this..