Chainrings And Cranks ?

[legrandefromage]

It would be cheaper just to buy a new rear wheel with a 7spd cassette option. You can then spread the rear stays the 2.5mm each side for the new wheel to fit. this gives you access for better cassettes and ratios and access to better shifters etc etc.

 

[legrandefromage]

even easier is to buy a donor bike and swap the parts. You will need a rear mech plate to run other mechs as they bolt to the frame on most bikes. Everything else should swap straight over.

 

[Agenthoover]

Ok... thanks for advice.. i might just re dish the wheel for now.... btw.. are these cranks worth getting hold of .. http://www.retrobike.co.uk/forum/viewtopic.php?t=215637 ... scroll down... its the STX FC-MC31-CH Limited Edition Chainset, 170mm arms

 

[legrandefromage]

Ok... thanks for advice.. i might just re dish the wheel for now.... btw.. are these cranks worth getting hold of .. http://www.retrobike.co.uk/forum/viewtopic.php?t=215637 ... scroll down... its the STX FC-MC31-CH Limited Edition Chainset, 170mm arms

You would need a new bottom bracket for those. Measure the shell width then you will need to work out the axle length, this will be considerably shorter than the one you have fitted.

 

[Agenthoover]

Well the distance from the center chain ring to the center of the down tube is around 47.5 mil if that helps any.. can check other measurments tomorow.

 

[legrandefromage]

you need to measure the shell of the bb, the part of the frame that the bb sits in. it will measure 68 or 73mm wide.

 

[Agenthoover]

Ok.. just popped out and checked it... its 68mm

 

[Agenthoover]

Would it be 110.5mm....... lol... ive been doing some research all on my own ...haha.. and that's what ive come up with... i think.

 

[FluffyChicken]

What is the need to change the chainset or go 7 speed ?

The STX-SE is many leagues above what you have on there, and yes you'll need a 68-110mm bottom bracket for it.
The one fitted will be ~68-122 from the look of it's profile.

If you want to go 7 speed then Just get a cheap 7 speed 130mm wheel. Old Deore DX crop up often for not a lot and can be found in that measurement as well as others, but you'll be looking for turn of the 90's era really. but get them to measure. Though you'll have little problem fitting a 135mm setup in there and often easier to find now.
Get a full wheel it's cheaper.
You'll then need the shifters as well.

 

[Agenthoover]

The cranks that are on it are bashed to hell teeth wise on the middle ring.. tbh its just an on going project im doing with my son.. the bike although a bottom of the range type thing has a lot of sentimental value

I was going with 7 speed because i didnt want to start cold setting the frame for 135mm... i could probably wedge a 135mm in there lol.. but would rather not do that.... with regards the wheels... i like things to match, replacing the back one would mean looking for a front one and tbh the wheels that are on it are pretty much perfect, condition wise.. the bike has actually stood doing nothing more than it has ever been ridden.