Converting a double ring crankset to a single?

[Steelhead]

I'm working on a fixed gear project -- last night I took the crankset off this old Bridgestone I am converting and took it apart. I then mounted the small ring, a 42 onto the outer side of the spider using the same chainring bolts. It fits nice and tight and is flush with the spider on the outside. Will this work ?? What about the chainline? I'm going small budget on this project, and I like the looks of the old Sakae crank arms and spider/chainring.

Thanks ! :)

[dirtdigger88]

it will work but you probably wont have a perfect chain line-

move the ring to the inside - like it would be if you were still running a double-
I bet the chain line is better with it there

but your results may vary

here is my fixed- notice the chain ring

http://forums.thepaceline.net/attachment.php?attachmentid=9926&stc=1

but look at the chain line- its slightly to the right

http://forums.thepaceline.net/attachment.php?attachmentid=9929&stc=1

I moved the ring inside shortly after these were taken

jason

[DfCas]

Usually you will need shorter chainring bolts/nuts,called single bolts. Also,most times its better to mount it on the inner side of the crank.

[Steelhead]

Usually you will need shorter chainring bolts/nuts,called single bolts. Also,most times its better to mount it on the inner side of the crank.

Maybe I could do that and then mount the original big ring on the outside, grind off the teeth and it would be instant ring guard to the small ring??

[dirtdigger88]

Maybe I could do that and then mount the original big ring on the outside, grind off the teeth and it would be instant ring guard to the small ring??

or go the the LBS and tell them you want BMX bolts- - - they will run you about $5

Jason

[Sasha18]

Maybe I could do that and then mount the original big ring on the outside, grind off the teeth and it would be instant ring guard to the small ring??

You shouldn't need a ring guard if the chainline is close and the chain is tight, but not too tight.

If you move the ring to the inside and the line is perfect, then use the BMX bolts. If it needs to go even further to the inside, then you can use regular bolts with a spacer.

Playing with the chainline seems kind of crazy and can get out of hand when you start playing with different BB widths to really get it right. However, it makes for a more efficient, quieter machine with less wear to the chain and gears.

Ring guards in 'cross are important because of the all the bumps, the use of gears in the back makes for a hardly perfect chainline, and the RD doesn't keep thee chain taut enough.

[gomez308]

It looks better if you mount the ring on the outside, where the big ring normally goes. Depending on your BB you should be able to get one that will put your chainline where it needs to be.

I've got an old Shimano 600 crank with a square BB. I think a 107mm is what I ended up with. It gives me a perfect straight chainline.

HTH

[Grant McLean]

The chainline is made up of TWO parts: 1) the crank and 2) the rear hub

You mentioned the crank, what's the rear hub?

If you're converting to fixed, you can change the spacing of the rear hub
to improve the chainline with the crank. I assume the frame has 130-135
rear drop out spacing? Re-arrange the spacers on the rear axle to get
the cog in the straighest line with the chainring. The rear wheel can be
dished to the necessary amount to compensate for whatever spacers you
need to use.

-g

[Steelhead]

The chainline is made up of TWO parts: 1) the crank and 2) the rear hub

You mentioned the crank, what's the rear hub?

If you're converting to fixed, you can change the spacing of the rear hub
to improve the chainline with the crank. I assume the frame has 130-135
rear drop out spacing? Re-arrange the spacers on the rear axle to get
the cog in the straighest line with the chainring. The rear wheel can be
dished to the necessary amount to compensate for whatever spacers you
need to use.

-gz

I'm going to be using an IRO flip flop rear hub, can't recall the spacing on the frame or the hub off hand. The frame is an old Bridgestonoe 400 road bike, circa 1984 and I am hoping a pretty standard width in the rear drops for a flip flop hub.

[Grant McLean]

I am hoping a pretty standard width in the rear drops for a flip flop hub.

There is no 'standard' for hubs.

Measure your frame between the dropouts. If it's 80's-early90's vintage
it's likely 124-126mm

Track size hubs are 120mm The aftermarket hubs usually offer a choice
of 120, 130, 135. You can easily re-arrange the spacers on most hubs.

-g

[Fixed]

make friends with some messengers
cheers
it is worth it bro

[Steelhead]

make friends with some messengers
cheers
it is worth it bro

I can't - I'm not cool enough.


:D kidding - I know a couple that may help out.