[oldtricks]

OK. So it seems complicated to change the back driver on my Zietgeist 22. So, was advised to go 23t with the 9 on the back. Good excuse to buy something shiney.
Was wondering if there are any issues with running such a gearing though? On a 20 inch it would be 23 x 8
Is it going to put extra strain on the chain, or put the chain too close to the frame?
Also, do I have to take the cranks off to fit it? or can I just unscrew the allen bolt and bolt the new one on?
Was thinking of going for a profile imperial , cheers

 

[Stoked]

chain should be ok. it may constantly hit the chainstay after landing something unless you run it super tight. 23x9 will be good, 56 gear inches. i like a lil harder gearing around 60. its all preference. what cranks do you have? if you have 19mm 48 spline look into the spline drive sprockets like tree or profile.

http://www.empirebmx.com/store/comersus_viewItem.asp?idProduct=9460
http://www.empirebmx.com/store/comersus_viewItem.asp?idProduct=6454

 

[oldtricks]

Thanks. How do I check if it's 19mm and 48 spline. Is 19mm the bore hole? They are just stock, no name cranks that came with the bike. 3 piece cro-mo.

 

[nyhc00]

19mm is width of your bottom bracket shell. It's either 19 or 22mm and 48 spline would be the type of BB your crank arms mount to.

 

[cmc]

19mm is width of your bottom bracket shell. It's either 19 or 22mm . . . .

19mm / 22mm = spindle diameters
68mm, 73mm etc. = bb widths.

25.4mm is one inch.

the stock Zeitgeist cranks are not 48 spline (Profile style). they are 6- or 8-spline style that come on a lot of stock bmx bikes. but, yes, it is very simple to switch sprockets and no it won't cause any problems. you may have to take a link out of your chain though.

 

[Stoked]

forget the spline drive sprocket. yes you'll need to remove the drive side crank arm to replace the sprocket.

 

[nyhc00]

19mm / 22mm = spindle diameters
68mm, 73mm etc. = bb widths.

25.4mm is one inch.

the stock Zeitgeist cranks are not 48 spline (Profile style). they are 6- or 8-spline style that come on a lot of stock bmx bikes. but, yes, it is very simple to switch sprockets and no it won't cause any problems. you may have to take a link out of your chain though.

thanks for correcting my mistake.

 

[iksmudge]

Oldtricks, did you measure the spindle diameter?
I had a go and think it's 22mm - am getting a micrometer from work today to make sure.

 

[oldtricks]

No I didn't. Let me know how you get on with the micrometer.

 

[oldtricks]

Been away and never did get round to buying that chainwheel. Sorry for being a dumb ass, but which one of these will fit. Profile looks the nicest, but I gather that won't fit. Right?

 

[oldtricks]

Mmmm! Don't think that worked. Here http://www.sourcebmx.com/products/drivetrain/bmx-sprockets/1253.shtml

 

[cmc]

Been away and never did get round to buying that chainwheel. Sorry for being a dumb ass, but which one of these will fit. Profile looks the nicest, but I gather that won't fit. Right?

A lot of bmx sprockets, the hole is for 22mm but there's a shim/insert/washer thing that brings it down to 19mm. So they work for both.
I'm kinda wondering tho why you want to change it. The current 25/9 with 22" wheels, results in a nice stout 61 gear inches. You can haul azz on street rides, but it's not too stout as to be unmanageable.

 

[oldtricks]

It's true it's good for going fast on the street. But I ride a lot in some small, tight parks and I find it a bit tough to get a run in sometimes. I also like to cruise about town with the seat up... which is a bit of a work out for my 45 year old legs... but yeah, I might just get used to it.