box opener

Dear all,

Here is a bike with sachs huret 6 speed freewheel , sachs huret 6 speed derailleur and original sachs huret 6 speed indexed shifter lever, I am not satisfied with the rear shifting, it is not smooth enough.I have tried out the adjustion on cable and derailleur, the rear derailleur shifts fine and normally on flat road but when going on upward road more likely the chain fails to shift to bigger cog, the shifting becomes less reliable, followed by a string of messy clicks caused by unsettled chain clashing with adjacent cogs.

I want the to improve the rear shifting to work more smoothly,basically two options.

option 1 ,Must I switch to shimano sprockets completely ? from this pictures can you tell if the teeth is well designed as shimano for chain shifting please?

option 2, If I can stick with the old freewhel sprockets and cogs, I plan to use sunrace Friction thumb shifter, do you think this friction shifter can make the shifting more smoothly? will the right hand friction thumb shifter hold the shiftcable firmly and accurately in postion, or will it gets loose over time and therefore realse the shiftcable accidently on bumpy road?

Could you give me some advises please?

By the way, the small chainring is in ellilptical shape, when drives it feels impulsive, will this disturb rear derailleur?

Thanks in advance.

nfmisso

Please review https://www.sheldonbrown.com/freewheels.html and re-phrase your question. The non-standard terminology you have used makes it extremely difficult to answer your questions.

box opener

edited and thanks for your advice

cny-bikeman

A Shimano 6 speed freewheel probably will shift better, even if you don't change the derailleur.

Almost all thumb shifters stay properly adjusted so as to not slip. Your current thumb shifter may cause problems by not staying on a cog if it slips, but it is not the cause of poor shifting from cog to cog.

If you do change freewheels and you have a lot of miles on your chain it's possible that the chain may slip (on the same cog) under high pedal pressure. https://www.sheldonbrown.com/chain-wear.html. If so you would then need a new chain as well. It's similar if you replace the chain but not the freewheel, especially if you tend to ride in the small freewheel cogs a lot.

The rear derailleur may be worn and have too much play, causing poor shifting, or there may be a problem with the cables. In-person help would be a good idea for you to decide the best plan, considering your budget and the overall state of your drivetrain.

Retro Grouch 

That's a pretty old bike. Who knows how much play exists in your derailleur and how much wear is in the chain and cogs. I'm thinking the cheap way out is with a friction shifter. That will let the rider adjust for all of those issues.

JohnDThompson 

All derailleur systems shift best when lightly loaded. Plan your shifts so you change to a lower gear before you hit a steep incline.

Friction shifting eliminates almost all compatibility issues, but it does have a learning curve. My music teacher daughter likens it to learning how to play the trombone: practice enough and eventually your hand learns when to stop moving. Properly adjusted, friction levers will hold your cables securely regardless of road conditions.

No, the rear derailleur doesn't care about the chainring shape.