Decathlon Cobra 520. 6 x 3 shifters. Help please!

[Jezd123]

New STi shifters will cost more than what the bike is worth, you could cheaply convert to band on downtube shifters.

Used Suntour power shifters are about £10 - £20 on ebay.

View attachment 426343

This is a good alternative, thank you! I’ve never used friction shifters before. Are they really difficult to get used to? Would I have to replace the shifters with a brake lever only or just leave the broken shifter on but disconnected?

 

[Jezd123]

The sprockets look like a 7 speed cassette on a freehub (30 OLN). Disappointed the Decathlon guy inferentially couldn't count (though their fault diagnosis is probably close). The 'teeth' on the inside may be just a bit 'bunged up' not worn down. First of all I'd give the innards of both STIs a good squirting with GT85/WD40, wipe off outside, leave to soak and see if the shifting improves.
If the OP sticks with 3x7 speed, then these STIs would do:
Shimano Tourney Road Bike STi Gear Shifter Brake Lever Triple 3 x 7 21 Speed Set
Could go 8 speed but new cassette and chain would be required, as well as 3x8 STIs which would cost more. Would have some concern that this expense would be disproportionate on a bike of this standard, though it looks in good nick.

Thanks, I’m definitely going to give the WD40 a go as a first go! Someone has posted a YouTube video and the problem with the shifter looks identical

 

[Ajax Bay]

Would I have to replace the shifters with a brake lever only or just leave the broken shifter on but disconnected?

If the general cleaning dousing does not solve it and you decide the way ahead is downtube levers, you can continue to use the STIs for brake levers. As far as the down tube option is concerned, I think you have brazed on bosses which will take gear levers so you don't need to use band ons.

 

[cyberknight]

sjs has tourney for £60
https://www.sjscycles.co.uk/gear-shifters/shimano-tourney-sta073-7-speed-triple-road-sti-levers/