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-   -   Rear cog (http://www.bikeforums.net/bicycle-mechanics/960285-rear-cog.html)

Kruzen 07-19-14 04:44 PM

Rear cog
 
Hey folks, I'm new to the forum. I hope I can get an answer to a question. I have a Diamondback response that is a project bike. It is a 7-speed. Can I install a 9 speed rear chain rings and change the shifter as well? It seems difficult to find up-grade parts for a 7 speed.

Thanks

Willbird 07-19-14 04:56 PM

Quote:

Originally Posted by Kruzen (Post 16954806)
Hey folks, I'm new to the forum. I hope I can get an answer to a question. I have a Diamondback response that is a project bike. It is a 7-speed. Can I install a 9 speed rear chain rings and change the shifter as well? It seems difficult to find up-grade parts for a 7 speed.

Thanks

from my limited understanding a 7 speed cassette cannot go 8-9-10, but an 8 can go 9-10 (not sure about 11)

if I understand correctly the wheel needs re dished to go from 7 up.

Bill Kapaun 07-19-14 08:32 PM

It depends on the Free Hub body that's on it.
8-10 speed bodies are longer than 7 speed bodies to fit the extra cog(s).
However, some recent 7 speeds use an 8-10 speed body with a 4.5mm spacer added before the cassette is installed.
IF you have one of these, just remove the 4.5mm spacer and you are good to go.

The bad news is that most recent 7 speeds seem to use free Wheels instead of Free Hubs.

Freewheel or Cassette?

Homebrew01 07-19-14 09:13 PM

Quote:

Originally Posted by Bill Kapaun (Post 16955337)

That is the first order of business.

Then specific information about the actual parts you have.

P.s. Terminology: "Chainrings" are attached to the crankarm, as are the pedals. "Cogs" are on the back wheel, either as a cassette, or part of a freewheel.

Miele Man 07-20-14 09:43 AM

If it's a Hyperglide cassette (lockring) and not a Uniglide cassette (smallest cog screws on) then you can use a 9 speed cassette IF you remove a cog and spacer. Some people remove the smallest cog as they don't need to high a gear - 11,12 or even 13 teeth cog but they keep the largest cog. Others remoce the largest cog.

If it's a Uniglide cassette and you have a Dremel type tool you can still use a number of Hyperglids cogs IF you grind the edges off of the large tabs so that it'll fit in the narrower Uniglide slot. You'll still need the smallest Uniglide sprocket to hold all the other cogs in place.

Sometimes you can use a bottom bracket lock ring instead of the smallest cog on a Uniglide cassette body to hold the other cogs in place. Just be sure to really, really tighten the lockring as the pedalling motion does not tighten it as the pedalling motion tightens the screwed on small Uniglide cog.

Cheers from Miele Man

LesterOfPuppets 07-20-14 10:51 AM

You can still get ef65 shifters at universal, niagara, etc. 7-sp cassettes and freewheels are still available many places. You can use any shimano 6,7,8,9 speed mtb rear derailleur, might wanna avoid rapid rise ones, though.

Kruzen 07-26-14 03:28 PM

Hm, thanks, would purchasing a 10 speed rear wheel and new Derailuers and shifters?

RoadGuy 07-26-14 03:47 PM

To see if you can upgrade to a 10 speed cassette in the rear, you need to check the rear dropout spacing first.

7-speeds were originally 126mm between the rear dropouts. Some manufacturers spaced the rear dropouts at 130mm (compatible with 8, 9, 10 speed cassettes), even on bikes that they supplied with 7-speed cassettes. My 97 Trek 1400 has a 7-speed cassette, and it has dropouts spaced at 130mm.

If you have a bike with a steel frame, although many do not recommend it, if your frame has 126mm rear dropout spacing, you could try having a shop reset the rear dropouts to 130mm, but there is some risk that the joints will pop, and the frame will be ruined (the shop will not be responsible if the frame is ruined). If you have an aluminum or carbon fiber bike, resetting the rear dropout spacing is not possible.

After determining if the rear droputs are wide enough, you need to check your rear wheel axle length to see if you can change the 7-speed freehub body to a 8,9, 10 freehub body and redish the rear wheel, or if the rear axle is 130, and has 8, 9, 10 freehub body and spacer for use with the 7-speed cassette.

I would think that if you need to buy a freehub body, and pay a shop to redish the rewheel, it may be less expensive to buy a replacement rear wheel.

If you have a newer rear wheel, and has a 10speed freehub, you're all set.

Remember that you will need to buy a new rear derailleur, new chain, and a new right side (rear) shifter (I don't know if your 7-speed front derailleur and left side shifter will work, or if they need to be replaced).

There are still plenty of 7-speed replacement and upgrade parts available. While your LBS may not actively be restocking 7-speed parts as they are sold, you may be able to swing a sweet deal with a bike shop that has the parts sitting in inventory gathering dust. You can also find 7-speed parts all day on eBay.

hueyhoolihan 07-26-14 03:51 PM

lots to do. i'd just get some nice 7 speed stuff.

RoadGuy 07-26-14 03:59 PM

Quote:

Originally Posted by hueyhoolihan (Post 16976942)
lots to do. i'd just get some nice 7 speed stuff.


Out here in SoCal, you can find Major Brand Name 14, 16, 18, & 20 speed road bikes priced anywhere from $175-$400 on CraigsList. There's a Trek 2100 (16-speed STI) Composite Carbon Fiber bike selling for $180, with an extra set of wheels and tires. I think it would be less expensive to buy a newer bike for the parts, than try to buy all the parts separately. The bonus is that you could ride the newer bike and see how you like it, before you strip it. You might find that you actually like it better than the old bike you're planning on upgrading.

Do you actually have a use for the extra gears, or are you planning an ungrade for the"cool" factor? I hate to break it to you, but nobody is counting the cogs on your rear wheel.

Darth Lefty 07-26-14 04:15 PM

Quote:

Originally Posted by Kruzen (Post 16954806)
Hey folks, I'm new to the forum. I hope I can get an answer to a question. I have a Diamondback response that is a project bike. It is a 7-speed. Can I install a 9 speed rear chain rings and change the shifter as well? It seems difficult to find up-grade parts for a 7 speed.

Thanks

I guess my question is, what is it you are trying to accomplish, what needs upgrading about it? Is something broken or does it not shift properly?

LesterOfPuppets 07-26-14 04:24 PM

The Response has 135 mm rear spacing. It's a mountainbike.

SkyDog75 07-26-14 04:28 PM

Quote:

Originally Posted by Kruzen (Post 16954806)
It seems difficult to find up-grade parts for a 7 speed.

Repair parts for 7-speed bikes are easy to find. Shifters, derailleurs, and freewheels are readily available and cheap from places like Niagara Cycle. You could probably get this thing riding like a new bike without spending a fortune. Upgrade parts, on the other hand... Well, what exactly are you trying to upgrade?

RoadGuy 07-26-14 08:22 PM

Kruzen,

I would have sent you a PM, except, I'm a new forum member, and can't PM until I get to 50 messages.

If you're interested in a whole set of parts from a highend aluminum mountain bike, I recently stripped down a Trek 8000 mountain bike for the parts after the SL (SuperLight) aluminum frame cracked up around the bottom bracket.


It has Alexrims DM18 Upgrade Wheels with a 9-speed cassette and good used tires, RockShok Judy front suspension fork, Bontrager seatpost, Deore LX 9-speed brake levers with integrated shifter, Deore Triple FD, Deore XT RD, KM 9-speed chain, Avid Series-3 V-brakes (needs new brake pads), Bontrager Comp triple crankset, and a sealed bottom bracket. The parts are dirty (have not been cleaned), but they are serviceable. The price would be $125, plus shipping for everything.

Would you be interested in buying the parts in a lot, or buying individual parts?


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