New chain set and derailiuer

[Stul]

Hi anybody...I think I may have made a mistake. I have an "old" Claud B mountain bike, and I have decided to replace some bits to give it a new lease of life. I have a new chain and 7 speed cassette, bit am having trouble sourcing a new chain set.
The larger ring (of 3) is a 38 tooth cog...and I can't find one anywhere?
I thought I would like to fit a larger 42 tooth cog, but the front gear change is fixed to the crank? ..ie so I can't adjust it / raised it any higher.

Other option is to fit the larger ring and a new front gear change unit..(top pull), but the down tube is 35mm?

Can anybody suggest a solution / best option. I do not want to spend too much, as I would rather buy a new bike.

Any help welcome,

Stu


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[Cycleops]

I am trying to get my head around this. You say crank but do you mean the the front changer is fixed to the seat tube? If it is it will be impossible to to fit a larger big chain ring. What are you trying to achieve?

 

[Stul]

Hi,

..sorry for the confusion...I am learning about bike bits as I go along...I will try and clarify....

I want to replace the original "worn", 3 ring chain set, but this has a main ring with 38 teeth, and I cannot find one anywhere. This leaves the option to fit a chain ring with a 42 tooth main ring, but I cannot fit this with the existing "E" type changer as this is attached to the bottom bracket...ie I cannot adjust the "height" of the front changer to compensate for the larger diameter ring.

Therefore I assume I would need to fit a new changer that is clamped around the down tube from the saddle (35mm diameter)..? I was just wondering if this would work OK, or does anybody know where I can get a 38 tooth chain ring set from?

...again thanks for any replies...

Stu

 

[RecordAceFromNew]

I thought I would like to fit a larger 42 tooth cog, but the front gear change is fixed to the crank? ..ie so I can't adjust it / raised it any higher.

Other option is to fit the larger ring and a new front gear change unit..(top pull), but the down tube is 35mm?

I think we are all a bit lost as to what exactly is fixed to the crank? If you are saying the chainrings are integral to the drive side crank arm (i.e. not bolted on to the spider so replaceable), then to have a 42T large ring you do have to change the chainset (and potentially the bottom bracket, if it is not compatible with the new chainset).

On the other hand if you are saying the front mech is fixed to the frame, then there are 3 types, conventional clamp on, braze on and E-type. See this for explanation and let us know if this is causing you any problem.

Down tube being 35mm is not an issue. I suspect what you have is 34.9mm a very common standard especially for mtbs. Further you can get front mechs that can handle any pull, e.g. this. Don't let the speed spec worry you. It will work with 7 speed chain fine.

 

[RecordAceFromNew]

Hi,

..sorry for the confusion...I am learning about bike bits as I go along...I will try and clarify....

I want to replace the original "worn", 3 ring chain set, but this has a main ring with 38 teeth, and I cannot find one anywhere. This leaves the option to fit a chain ring with a 42 tooth main ring, but I cannot fit this with the existing "E" type changer as this is attached to the bottom bracket...ie I cannot adjust the "height" of the front changer to compensate for the larger diameter ring.

Therefore I assume I would need to fit a new changer that is clamped around the down tube from the saddle (35mm diameter)..? I was just wondering if this would work OK, or does anybody know where I can get a 38 tooth chain ring set from?

...again thanks for any replies...

Stu

To replace the chainring you need to know the type and bcd. There are all sorts of chainrings on the market, e.g. these for 104bcd common for mtb chainsets.

E-type mechs are generally not adjustable. You will have to replace it (and likely the bb unless you replace it with another e-type such as this) if you want a larger large ring.

 

[Stul]

...brill......many thanks for taking the trouble to reply..I think I will give chain reaction a call and see of I can get a new 42 chain set and appropriate changer...