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Advice on bike gearing

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  • Advice on bike gearing

    Picked up a bike for tipping around the city a month or two ago. Gearing is fine for negotiating traffic where I'm usually in some of the middle gears. It's literally just for hacking around and running errands. Scenery and fresh air rather than training/speed, if you get me...
    But the odd time at weekends I venture out of the city, mostly on cycle ways, and I'm finding top gear too short for my own comfort.

    At the moment the front ring is 42T on the large ring/24 on the smallest, and the rear cassette is a 7-speed 14-28T.
    (Didn't count the centre ring on the crank, should I? My one observation is I tend not to notice much between 6/7 on the centre ring and the top ring).

    I'm hoping the knowledgeable folk on here can suggest possible alternatives for gearing. I'd like a taller top gear, without losing too much from the lower gears.
    All input appreciated!
    Last edited by deltona; 04-11-2021, 01:35 PM. Reason: ETA: Corrected 40T to 42T

  • #2
    40 14 is small enough for a top gear alright. At 90rpm you're doing 32kph according to gear calculators. A decent enough speed and great cadence if you can mantain it.

    No idea if your groupset allows a change of cassette or chainrings. But in normal road or mtb'ing it is of course a very common thing to change. A cassette is usually easy to swop out but I don't know what the story is with more basic commuter style 7 speed cassette set ups.


    • #3
      The rear cassette is a Shimano MF-TZ500-7.

      I'm not sure on the chainring, but I've placed pics of front and rear below, if it helps identify what is indeed possible.
      You do not have permission to view this gallery.
      This gallery has 3 photos.
      Last edited by deltona; 03-11-2021, 11:35 PM.


      • #4
        Correct me if I'm wrong, but is it a 42T chainring rather than a 40? I'd suggest swapping out the whole crankset for the other Tourney option which had a 48t as the largest front ring?

        Shimano Tourney TY501 6-8s Crankset - Black.Shimano Tourney Ty - Mtb Crankset - 185.5 Mm Q-Factor - 3x8/7/6-Speed Compatible With A 3x8, 3x7, bike


        • #5
          Originally posted by Murakami View Post
          Correct me if I'm wrong, but is it a 42T chainring rather than a 40? I'd suggest swapping out the whole crankset for the other Tourney option which had a 48t as the largest front ring?
          Sorry, I'd miscounted. You're correct - it is 42T.

          Are cranksets / chainrings mostly interchangeable, or is there anything I need to watch for?

          The spindles are marked Prowheel, although I can't see anything on the chainring itself. Should I be looking at sticking to Prowheel, or will a Tourney option fit straight on too?

          ​​​​​​​Thanks for the advice so far fellas - much appreciated.


          • #6
            You should be able to put it straight on and then adjust the front derailleur. But some better mechanically than I can confirm.


            • #7
              Hard to advise with any real certainty without having a bike like that in front of you to check it out. Your max gear for high speed is 42x14 - that's very small. A lot of racers would have a 53x11 or 12. You could increase the size of the biggest ring on the front or you could fit a different cassette on the back. Impossible to know without taking the cassette off whether the rear wheel has a freehub or freewheel fit so couldn't recommend something to purchase online. https://www.bike-discount.de/en/bike...cket/7-speed/? Something with an 11t would make a good difference.


              • #8
                Thanks Desmo.

                The MF-TZ500-7 is listed as a freewheel fit;

                What do you guys think would be the best place to start - a 48T front ring, or changing the rear cassette?
                I'm not ruling out doing both, but if one option gets me close enough I'll be happy. But which would have the biggest change from the current setup? I reckon I'm about 20% down on a previous comfortable cruising speed at the same cadence.


                • #9
                  I'd probably start with a different cassette, something with an 11t. A 42*11 is a lot bigger a gear than a 44*14. At 80rpm one is 38.5kph the other 31.5kph.

                  I think there's an old rule of thumb that for every 1t you change on the back you'd need to change by 3t on the front, so 42*13 would be a similar gear inch to 45*14.
                  Last edited by Desmo; 05-11-2021, 09:23 AM.


                  • #10
                    Cheers Desmo. I'll have a play with some of those online gear calculators and see what components I can source locally/online.

                    Thanks to all for the advice and education!


                    • #11
                      Come back to us on the result. If you're still spinning out the 11 sprocket in your slacks and shoes, it might be time to approach a local racing club...


                      • #12
                        😆 There ain't no fear whatsoever of that!


                        • #13
                          Looks like you could (if available) go 11- 28 on a new cassette. Rule of thumb you'll need a long cage derailleur for 11-32+. Medium or long cage derailleur as is should be OK. *

                          *take all this as potential nonsense amd is not applicable at all..


                          • #14
                            Quick update to close this out, and say thank you to all for the help.

                            I popped to a local bike store who supply Shimano components (amongst others) and they informed me that with this Tourney freewheel setup it wasn't possible to get anything below 14T due to the size of the internal bearing. Which tied in with what I saw on Shimano's own website. They don't do a Tourney freewheel gearset with less than 14T.

                            So instead I changed the front chainring. Removed the Prowheel 42-34-24 and replaced it with a Shimano 48-38-28.
                            The 38T centre ring is where I spend all my time hacking around the city and in traffic, never needing to move to the 48T in variable speed stop/start city traffic.
                            The 48T has given me what I wanted on a more open straight spin away from traffic - a much more comfortable cadence at a nice cruising speed. (Blew out my knee when a teen, and whilst it gave me jip on and off through the years it's been a persistent and painful weak link over the last 3 years, hence the need for a comfy cadence).

                            ​​​​​​​On a related note - have many on here knowledge of Prowheel components? I wasn't impressed by the quality of the chainrings when I went to count them, and now that it's off the bike it's even more apparent how suspect the quality is. What's the perceived reputation like on their components?


                            • #15
                              Not to say that they mightn't make ok parts, but I've never heard of them before this thread.


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