Re: fixed gear chainline question

[Dan]

Derekcommonground wrote:
> i'm building up my first bike... i'ts got a flip flop hub and i just
> spent the evening putting in the bottom bracket, crank arms, pedals and
> put the rear wheel on... but the chainline looks pretty off to me. the
> chainring seems kind of far out, and the cog seems more towards the
> middle. i know i can't adjust the spacing on the hub otherwise i won't
> be able to use the flip flop... and there is a washer/spacer in the
> drive side of the bottom bracket i can take out, but i'm not confident
> it will be enough to make the chainline perfect. is there anything else
> i can do? i think i can get it close enough to be safe, but i'd like to
> get it as best i can.
>
> thanks,
> Derek
>
>
>
>

We really need to know what cranks you are using. If you are using a
road crank, put the ring on the inside and add spacers as required.
Measure the offset from center line to the chainwheel and to the cog to
determine the spacer size you want.

http://www.sheldonbrown.com/harris/fixed.html#bolts

Scroll down to "chainwheel Spacers" Make sure your bolts are long
enough. The spacers come in different sizes and the bolts can be bought
in different lengths.

Call up loose screws and tell them what you want:
http://www.loosescrews.com/index.cgi?c=Crank/Chainring&sc=Chainring Spacers&id=225300131095
http://www.loosescrews.com/index.cg...c=Chainring Fixing Bolts/Nuts&id=225300131095

 

[[email protected]]

Derekcommonground wrote:
> i'm using a 118mm hollow spindle in my isis bottom bracket, the
> chainring is already on the inside, so those chainring spacers look
> like they'd be really helpful. does it matter if the chainring doesn't
> sit in the indented part of the spider?

No.

> here's the bb/crank i'm using:
> http://tinyurl.com/ukr3o

I assume you've take off the existing chain rings and are using just
one.

> and here's the hub/wheel i'm using:
> http://tinyurl.com/y4n84w
>
> i don't think using a shorter spindle is an option,

It might be. The only danger I can think of is that the 5 bosses for
the inner chain ring bolts might hit the frame. Otherwise you should be
able to use any shorter ISIS bb.

> but if i take out
> the spacer and add some chainring spacers, that will definetly help.
>
> also, i think i'm going to have to get a new chainring/chain as the
> chain i had seemed to fit fine on the chainring, but the tooth size
> seems larger on the cog...

Probably so. Your cog sounds like it may be 1/2 x 1/8", rather than
1/2/ x 3/32". I like the Wippermann Wesstern (White Star) chain for
track and single speed. It's not even that expensive.
http://www.businesscycles.com/tchain-wip.htm

> thanks a lot!
> Derek
>
>
>
>
> --
> Derekcommonground

 

[SYJ]

Derekcommonground wrote:
---snip---
> i'm using a 118mm hollow spindle in my isis bottom bracket, the
> chainring is already on the inside, so those chainring spacers look
> like they'd be really helpful. does it matter if the chainring doesn't
> sit in the indented part of the spider?
---/snip---
> Derekcommonground

118 sounds pretty long. How much clearance do you have between the
crank arms and the chainstays? If more than 6 or 7mm, you might want
to try a road ISIS BB (108.5 IIRC).

The spacer between the DS cup and BB shell are likely to allow a single
BB to be used with 68 or 73mm shells. Try to remove it, but you may be
SOL.

If all else fails, you may be able to track down a square taper crank
(try takeoffs at your LBS), which will open the door to numerous
spindle lengths - ISIS is a standard, with fixed lengths for road and
MTB. square taper cranks will be available in flavors of 102 to 122+
to meet your specific needs.

HTH,
SYJ