Seven / eight speed - ?

[simongt]

Eldest son bought a cheap MTB a few months ago. He took it to a LBS to get the gears checked over and all is generally okay apart from the gears slipping occasionally. Now the shifter and cassette are both eight speed, but the LBS says that the changer is a seven speed, so the occasional slipping is to be expected.
Now, I'm no expert on derailleurs, so can anyone enlighten us as to what the LBS manny means please - ?

 

[raleighnut]

You need to fit a new 8 speed shifter.

 

[DCLane]

What type of shifter and derailleur is it? If it's 8 speed or under the derailleur shouldn't make any difference.

 

[Black Sheep]

I don't think that's how that works.

The derailleur works on having a limit of movement which you can set with the + and - screws to stop it going too far towards the spokes and taking the chain off the top or taking it too far the other way, off the bottom of the smallest cog.

the amount of movement is controlled by the shifter pulling the cable, if the cable tension is not correct it won't shift properly, easiest re-set by putting the bike in the smallest gear (cable at it's slackest) and then tightening the cable at the cable clamp, then tweaking using the barrel adjuster.

7&8 speed derailleurs are, as far as I am aware, pretty much the same, I've paid little attention to the spec when buying and fitting over the years, the spacing on the 'block' of gears is pretty much the same also.

9 speed (and that new fangled 10 speed, which is just wrong I tell thee!) however, the gears sit slightly closer together and as such the chain is also narrower - so you'd need a 9 speed (or 10 speed) matched set up.

 

[User6179]

1. Shimano
6, 7, 8 and 9 speeds
Rear shift ratio is 1.7, that is for 1 mm of cable pull/release, RD is moved left/right by 1.7 mm. Shimano calls this 2:1 ratio for marketing reasons.

All these RDs are compatible and any 6 to 9 speed RD will work perfectly with either 6, 7, 8 or 9 speed shifter. Regardless whether it’s a MTB, or road shifter, or RD. They are also compatible with Shimano 10 speed road shifters, except the Tiagra 4700 series.

Shimano Dura Ace from 1984 to 1996 period (6 to 8 speeds)

Rear shift ratio is 1.9. They are compatible only with Shimano Dura Ace shifters from the same period (that is for 6, 7 and 8 speeds).

 

[Black Sheep]

unless someone's tried to match Shimano shifters with a Sram rear mech, two different manufacturers so not going to work together properly.

 

[Andy in Germany]

Slightly off topic, but do 7 & 8 Speeds share the same hub?

 

[fossyant]

Slightly off topic, but do 7 & 8 Speeds share the same hub?

Yes -6-10 speed can sit on the same hub, just more spacers.

 

[gbb]

Slipping shouldn' be expected, the shifters almost certainly won' make that happen.
7 and 8 speed have the same spacing so assuming it' set up correctly the only issue you should see is you can only use 7 of the 8 years on the cassette .

IMO there's a problem with the setup not the shifters.

 

[mickle]

The bike shop is chatting bollix. A seven speed shifter will operate an eight speed cassette. Just decide whether you want to lose the bottom or top gear.

If the bike has thumbshifters you can use the space beyond the last click for the eighth sprocket. Presuming that your limit adjust screws are set correctly at each end of the derailleur's range of travel.

 

[Ajax Bay]

Now the shifter and cassette are both eight speed, but the LBS says that the changer is a seven speed

You can discover whether the 'shifter' (on the bar) is an 8 or 7 speed by counting the clicks: 8 speed has 7 and 7 speed has 6. Others up thread have said that the 'changer' - assume means derailleur (near the sprockets) will be compatible with a range of speed shifters, so see @mickle 's assessment of the LBS advice.

What type of shifter and derailleur is it?

OP = please answer David's question.

6-10 speed can sit on the same hub, just more spacers.

Please could you provide a link to a 6 speed cassette that can slide on to the 'standard' (let's say Shimano) freehub? Or would that be 6 sprockets cobbled together. Can you get Uniglide splined hubs nowadays?

 

[Andy in Germany]

Eldest son bought a cheap MTB a few months ago. He took it to a LBS to get the gears checked over and all is generally okay apart from the gears slipping occasionally. Now the shifter and cassette are both eight speed, but the LBS says that the changer is a seven speed, so the occasional slipping is to be expected.
Now, I'm no expert on derailleurs, so can anyone enlighten us as to what the LBS manny means please - ?

I've been running exactly the same setup for years on two different bikes for years , never had the slightest problem.

I'm currently changing gradually from seven to eight speeds, on my second bike firstly using an eight speed shifter with the eighth speed locked out using the limiter screws, and soon to change to an eight speed cassette as I try and get the last bit of use out of the seven speeds, and spread the cost as much as possible.

I've never had any trouble on either bike and I don't intend to change my mech until it wears out completely.

 

[fossyant]

You can discover whether the 'shifter' (on the bar) is an 8 or 7 speed by counting the clicks: 8 speed has 7 and 7 speed has 6. Others up thread have said that the 'changer' - assume means derailleur (near the sprockets) will be compatible with a range of speed shifters, so see @mickle 's assessment of the LBS advice.

OP = please answer David's question.

Please could you provide a link to a 6 speed cassette that can slide on to the 'standard' (let's say Shimano) freehub? Or would that be 6 sprockets cobbled together. Can you get Uniglide splined hubs nowadays?

Uniglide fits hyperglide. I have plenty of uniglide sprockets on new hubs. Uniglide and hyperglide upto 8 were mainly single sprockets.

 

[Ajax Bay]

I have plenty of uniglide sprockets on new hubs.

So 6 speed cassettes are only made in unobtanium alloy, then?

 

[fossyant]

So 6 speed cassettes are only made in unobtanium alloy, then?

They came as 6 or 7 speed but were individual sprockets. I have a 7 speed MTB but build the cassette with an 8 speed these days and ditch 1.

Its the freehubs that will accept any number of sprockets upto 10 with the right spacers. Some will take 11 as well