Jockey wheels - which is tension, which is guide?

pollys_bott
pollys_bott Posts: 1,012
edited January 2019 in Workshop
As per the title: I stripped the bike down for a good clean and this included pulling the rear mech to bits. I discovered by pure chance yesterday that apparently all jockey wheels are not created equal but one is known as the guide and the other the tension. Clearly I had a 50% chance of putting them back in the mech the right way round but how can I tell if I did and / or does it matter if I didn't?

Thanks...

Comments

  • keezx
    keezx Posts: 1,322
    Top is guide and lower is tension.
  • andy_wrx
    andy_wrx Posts: 3,396
    Think about it - top one guides the chain onto the right cog of the cassette, bottom one is used by the spring in the dérailleur to tension the chain tight - simples !
  • Matthewfalle
    Matthewfalle Posts: 17,380
    I think he means that he thinks that the wheels are different - that when someone was thinking of designing them he thinked that it would be best to think of two different designs for the tension and the other one (I can't think offhand what the guy who thinked up the design thinked the name for the other one would be).

    I think that I understand what the Op thinked when thinking about this and then when thinking about his post and I think that both are the same just in different places.

    It's thinking annoying though if they fall on the floor under the workbench.

    I think that may help.
    Postby team47b » Sun Jun 28, 2015 11:53 am

    De Sisti wrote:
    This is one of the silliest threads I've come across. :lol:

    Recognition at last Matthew, well done!, a justified honour :D
    smithy21 wrote:

    He's right you know.
  • JayKosta
    JayKosta Posts: 635
    If there is adequate clearance between the top pulley and all the gears for the chain to run and shift smoothly then it's fine. If there's trouble, try switching the pulleys.
    My 'guess' is that if one pulley is smaller then it's the top guide pulley.

    Jay Kosta
    Endwell NY USA
  • pollys_bott
    pollys_bott Posts: 1,012
    Keezx / Andy_wrx: thanks, I'd worked that bit out; what I was trying to ask (not clearly enough it would seem) was how do I tell the difference between the wheels? Look at these:

    http://www.wiggle.co.uk/shimano-105-rd- ... ustReviews

    Is it just my eyes or do they look identical to each other?

    One of the reviewers says: "Remember to fit the right pulley in the right location, and the tension pully must be fitted in the right direction"

    Eh?! I can't even tell which wheel is which let alone which way round it goes... :lol:

    Matthewfalle: very good sir, it's even more annoying when they fall through a gap in the decking...

    JayKosta: it all shifts and runs beautifully, but given that I'd put new chain-rings, bottom bracket, cassette and chain on I'd have been rather upset if it hadn't! Maybe I just got lucky and put the right one in the right place...
  • For Shimano jockey wheels, they usually have a small arrow moulded in which gives rotation direction, and the top pulley usually has "G. Pulley" moulded in somewhere.
  • keezx
    keezx Posts: 1,322
    I think he means that he thinks that the wheels are different - that when someone was thinking of designing them he thinked that it would be best to think of two different designs for the tension and the other one (I can't think offhand what the guy who thinked up the design thinked the name for the other one would be).

    I think that I understand what the Op thinked when thinking about this and then when thinking about his post and I think that both are the same just in different places.

    It's thinking annoying though if they fall on the floor under the workbench.

    I think that may help.

    I thougt these things were all marked with upper or lower , but that's because I thought Dutch Tacx wheels are superior so I thought I'd have to throw away the originals.
    @pollys Bott: buy only superior Dutch Tacx wheels and I thought you will be very happy.
  • crikey
    crikey Posts: 362
    The guide pulley in Shimano mechs has a slight side to side wobble to account for all the ham-fisted spanner monkeys who take them to bits and then can't put them back together properly...
  • keezx
    keezx Posts: 1,322
    edited December 2014
    All jockey wheels have either more play in the top one or the top ones are narrower to compensate slight inaccuracy in their postion as the system is not perfect and still will run smooth.
    Not much to do with spanner monkeys......
  • They are also asymmetric.
  • keezx
    keezx Posts: 1,322
    THAT is new for me as I exclusively use the superior Dutch Tacx's, which are symmetric.
  • keezx
    keezx Posts: 1,322
    JayKosta wrote:
    If there is adequate clearance between the top pulley and all the gears for the chain to run and shift smoothly then it's fine. If there's trouble, try switching the pulleys.
    My 'guess' is that if one pulley is smaller then it's the top guide pulley.

    Jay Kosta
    Endwell NY USA

    This must come 100% from your phantasy as I have never seen a modern derailer with 2 different sizes.
  • http://www.wiggle.co.uk/shimano-105-rd- ... ustReviews

    Is it just my eyes or do they look identical to each other?

    Your eyes :wink: The upper left one in that pic has a clear chamfer on one edge of each tooth
    ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH
  • veronese68
    veronese68 Posts: 27,308
    Keezx wrote:
    JayKosta wrote:
    If there is adequate clearance between the top pulley and all the gears for the chain to run and shift smoothly then it's fine. If there's trouble, try switching the pulleys.
    My 'guess' is that if one pulley is smaller then it's the top guide pulley.

    Jay Kosta
    Endwell NY USA

    This must come 100% from your phantasy as I have never seen a modern derailer with 2 different sizes.
    Shimano mega range use a larger bottom pulley.
    4018-121_BK000_view1_1000x1000.jpg
  • keezx
    keezx Posts: 1,322
    Aah, missed that one.
    I don't spend much time looking at Shimano parts......
  • veronese68
    veronese68 Posts: 27,308
    Keezx wrote:
    Aah, missed that one.
    I don't spend much time looking at Shimano parts......
    Not something you'd want to look for. I noticed one on a bike I was repairing for a friend because it had a huge red jockey wheel. Usually only fitted to low grade hybrids and the like. Supposedly the bigger pulley allows a cassette with an even wider range. I thought longer cages did that.
  • pollys_bott
    pollys_bott Posts: 1,012
    http://www.wiggle.co.uk/shimano-105-rd- ... ustReviews

    Is it just my eyes or do they look identical to each other?

    Your eyes :wink: The upper left one in that pic has a clear chamfer on one edge of each tooth

    That's a relief: for a moment I thought you were going to tell me that the lower right one clearly says "G.Pulley" on it...

    As it turns out I had put them in the wrong way round but seeing as it is all running beautifully smoothly and quietly I don't think any major damage is being caused...
  • Ouija
    Ouija Posts: 1,386
    Veronese68 wrote:
    Keezx wrote:
    Aah, missed that one.
    I don't spend much time looking at Shimano parts......
    Not something you'd want to look for. I noticed one on a bike I was repairing for a friend because it had a huge red jockey wheel. Usually only fitted to low grade hybrids and the like. Supposedly the bigger pulley allows a cassette with an even wider range. I thought longer cages did that.

    It's usually the distance from the hinge point on the frame to the top jockey wheel that decides how big a cassette the mech can take, the distance from top jockey wheel to bottom (the length of the cage) really only determines how much chain slack the derailleur can take up. On some mechs (usually mountain) the distance from hinge point to upper jocky wheel is the same on small, medium and long cage versions so has no effect on the size of the cassette it can take. On others (more often road), the small, medium and long cage versions also have different length upper arms that effect cassette capacity.

    The size of the jockey wheels themselves also play a part. Big upper jockey wheels sit closer to the cassette when your on the larger rings and reduce the total number of teeth that can be on the cassette (whereas a same caged sized derailleur with smaller jockey wheels may be able to deal with bigger rings).
  • Praise the lord for this forum. Did exactly the same thing as the OP, removed the jockey wheels to clean them as I've been doing various repairs including changing the chain, and when I came to reassemble did wonder if they were different. By a fluke I've put the "G pulley" in the top!