adjusting gears

First time here so apologies if this is a regular topic. I just got a kit for my bike which has come with a 6 speed shimano freewheel gear set ready attached to the wheel. Well I think it's a freewheel though I've never taken much notice.

 

The existing bike has an 8 speed gear set. If I can make it work I'd like to stick with the existing shifter mechanism, but I can see that there's a chance I might be running the chain off the end of the cogs.

 

I don't think I can swap the gears over as they are probably just a bit too wide with the hub motor. How do I adjust the shifter mechanism for 6 rather than 8 gears?

On the rear of the rear gear mechanism there's two adjuster screws close to each other. One sets the outer limit of travel, the other the inner limit of travel.

 

By adjusting those with the bike on a stand or upside down and turning the cranks, you'll be able to set the spacing and gear changing consistency while operating.

 

In the photo below, the topmost screw sticking out on it's own sets the swivel of the whole mechanism, it's the pair of screws below that I'm referring to:

 

You'll also find highly detailed info on this in this webpage almost halfway down

 

http://www.twoknobbytires.com/media/rear_derailleur.jpg

Edited February 12, 201610 yr by flecc

8-speed gear set comes either as a cassette type or screw-on freewheel type. If it's a cassette type, you should replace the supplied 6-speed freewheel with a new 8-speed freewheel. If your old bike has a 8-speed screw-on freewheel, you should remove it from the old wheel and fit it to the new motor. It's easy to do if you have the right tool.

Thanks flecc - that's a really helpful description.

 

Trex - thanks for the suggestion. Although this would be the ideal way to go, 8 cogs take up just too much room.

Can we have a photo? 8 hub gears fit most rear dropouts it is 9 and above that get a bit tight. What is your dropout width with your current wheel in?

Can we have a photo? 8 hub gears fit most rear dropouts it is 9 and above that get a bit tight. What is your dropout width with your current wheel in?

 

Thanks for this. My dropout width, that is the spacing between the two sides of the spindles that sit inside the forks is 135 mm. The new motorised wheel and 6 cogs just fits, but interestingly the cogs are spaced a little wider than on the original. The 8 cogs are 5 mm apart, but the 6 cogs are 6 mm. So it looks like it's 5 mm wider than original with 8 cogs. I might just be able to squeeze this in.

If you keep the new 6 speed cassette with the 8 sp shifter then you can try adjusting the 2 small screws at the rear on the photo. In line with Trex's post the bottom screw adjusts the mech for going up through the gears and can be set so the chain doesn't come off into the spokes and the top screw is for going down the gears. The very top larger adjustment is for tension.

With std 135mm drop out there should be little reason 8 or 9 sp cassettes or freewheels can't be used, but you may need to match a correct chain for the correct sp cassette used.

You need to get the 8 speed on there, or your indexing will be all over the place.

 

The rear mech simply moves from one limit to the other, but your shifters control by how much for each change. In other words, your shifters are matched to an 8 speed cassette/freewheel.

 

If there is a bulge in the hub then you have a cassette. If not, then it prob a freewheel. Either way, you need a special tool, a chain whip and an adjustable spanner. (I've done it plenty of times without a chain whip though. An old rag is normally good enough)

Yes at 135 mm there is no problem fitting an 8 speed. If we knew the motor kit type we could tell you if it is a cassette or a freewheel. If you need a freewheel you will be looking for a Sunrace which comes in either 13-32 or 13-34. Shimano only go up to 7 speed in freewheels.

 

There is also a DNP epoch which is a 11-30

Edited February 14, 201610 yr by anotherkiwi

He's got a rear hub motor with freewheel.

I've got an 8-speed sunrace freewheel for my converted Giant D5.

So my old wheel with the 8 cogs - is that a free wheel or a cassette?

 

You can tell I've not done much beyond pumping up the tyres.

you find the model of the freewheel or cassette, something like 'Shimano HG50' then google it up or post it here.

 

Cassettes have a lockring at the top.

 

http://s.wiggle.co.uk/product-media/5300001390/sram-8-speed-cassette.jpg

 

freewheels have the cylindrical shape for the tool:

 

http://g02.a.alicdn.com/kf/HTB1HGN8IXXXXXbeXXXXq6xXFXXXb/-font-b-Sunrace-b-font-mountain-bicycle-bike-8-24-speed-cassette-volantes-font-b.jpg

Edited February 14, 201610 yr by trex

I would guess that your existing 8 speed is cassette, and that your new hub motor is freewheel, so as others have said you will need to purchase an 8 speed freewheel.

I would guess that your existing 8 speed is cassette, and that your new hub motor is freewheel, so as others have said you will need to purchase an 8 speed freewheel.

Yes - following trex above I've cleaned off the grime on the old wheel and found the numbers. It is indeed a cassette.

Andy, there are a few possible stumbling blocks in changing the freewheel on a hub motor, so here's some guidance for you.

 

The first is getting a suitable correct tool, since many have too small a central hole for the often larger spindle of a hub motor. An example of the tool you need is a Cyclepro cpt203, at £9.99 on most sites but one on Amazon currently at £6-19. This is designed to use either a 21mm spanner or a 1/2" drive socket set. The square 1/2" drive socket hole allows an oversized spindle through the hole.

 

The next problem is that the cable that comes from the motor spindle often has a terminal block connector which prevents the tool from being passed onto the freewheel, and is often also too large to allow the freewheels to pass over it. The most common type has pin connectors with locking tongues in the form of blades sticking out of the side of the pins. To disconnect the block, first carefully note the positions of each colour wire and the orientation on the terminal block relative to them. Then use a probe like a very thin screwdriver blade to push aside each locking tongue to allow each wire end pin to slide out of the block. With all the wires and pins out the tool and freewheels will pass over ok. An alternative is to cut the wires and reconnect and insulate them afterwards, but that is a messy solution.

 

Then use the tool and a chainwrench to remove the old freewheel, and you'll find the instructions and photo on my website useful for this, they're on this link. That is for a cassette in fact but the principle is the same. Chainwrenches can be expensive, but branches of Machine Mart have a reasonably priced one if you don't find one at a local shop or ebay.

 

After fitting the new freewheel reassemble the connector using care in getting the wires into the correct positions.

 

An alternative to all this might be suitable if you don't have a wide range of hill gradients and the six gears is sufficient. That is to change the gear shifter to a six speed one.

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Edited February 14, 201610 yr by flecc

Ok an update. I've been working on the kit over the weekend, and have got the bike running. Following help on here, I've learned how to adjust the 6 speed so it changes smoothly, and with battery power it's pretty impressive. I've only ridden it a mile so far and it needs all the wires tidying up but I think it's going to be fun.

 

Thanks everybody.

Well done Andy, six speed setups are usually quite tolerant regarding gear changes and it seems your 8 speed changer is working ok with the six.

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