Dolan Pre Cursa / PreCursa / Track Champion

Just got a complete Dolan Pre Cursa, and thought it was a bit noisy. Measured my chainline, and it's 41mm at the cog and 46 at the chainring. So I thought maybe it had the wrong bb fitted. Took it out and, it's a Sunrace 68x103mm, which is the right kind for my Sugino RD2 crankset.. Regreased it and put it in properly but I'm still getting 41-46mm. What am I missing?

103mm is a short BB - you certainly couldn't get a 99mm BB to create a 42mm chainline. It's probably to do with the chainring - is it mounted on the outside of the spider when it should be in the inside? Some cranksets work either way so that the outer position is for SS MTB hubs (like the Stronglight Mygal).

Or is the ring on back to front or something?

Bottom bracket screwed all the way in?

Not sure what else it could be.

I concur. Must be something wrong with your crank/ring setup?

I've got RD2 on my precursa with a 103mm BB with no chain line probs.

Cranks tightened down onto the spindle fully?

Has the previous owner added chainring bolt spacers...?

BB is screwed all the way in, at 360 inch pounds, with torque wrench. Cranks are tightened as much as i dared..

No bolt ring spacers, as it's a brand new bike..

I concur. Must be something wrong with your crank/ring setup?

I've got RD2 on my precursa with a 103mm BB with no chain line probs.

How is your chainring mounted onto the spider?
I don't have my bike here right now, as I'm at work, but here are a few pics:

Gah, this is driving me nuts..

Maybe I've measured it wrong?

The way I measured was as follows:

Front: distance from seat tube to teeth on chainring + 1/2 of the widt of the seat tube.
back: 60mm - distance from inside of dropout to teeth of cog.

Seems to me like the correct way?

Is the Sunrace BB ISO taper? Those Suginos will be JIS taper.

If so that'll put it 4.5mm out(ish).

Sugino seem to spec the RD2 chainline as 45mm...

http://www.suginoltd.co.jp/japan/single_piste_parts_list_japan.htm

Seems it might come from originally being a double chainset - from those pics it definitely allows for a ring on the inside of the spider. So I reckon you could just mount it on the inside as long as you have the chainstay clearance (which you should on a track bike like the Precursa). Maybe ideally you would need a 1 or 2 mm longer BB, but if your hub is giving 41mm it might be perfect.

The RD2 is not a track crankset, its a road double remarketed for 'fixies'.
You need to switch to the inside crank spider position for 42mm, outside is 46mm. Same as shimano road double.

also 99mm bb would give you 44mm, not that you can get a 99mm anyway

also 99mm bb would give you 44mm, not that you can get a 99mm anyway

Oh, yes, you're right. Mathsfail.

BB is JIS.
Hm, okay, guess I'll have to mount the ring on the inside for now. Looks ugly as hell, though.. Will the Sugino 75 give me the same problem? Was thinking about getting a black chainset anyway. Was looking at the 75 or possibly Miche Primato, but from what I've read, it's hard to find BBs that work well with it..?

Sugino 75 is a proper track crank, you'll have no problems there, but it's expensive and you need a matching 75 or Zen ring really.

I would go for a Stronglight Track 2000 over the Miche:

http://www.planet-x-bikes.co.uk/i/q/CSSTTR2K/stronglight_track_2000_crankset

With a 107mm Shimano UN54 bottom bracket it comes to about £70, it looks better than the RD2 and it's way stiffer.

Hm, was looking for black cranks actually (I'm vain, sue me), but that's so cheap, I might just go with that for now.
Unless you have some good suggestions for black cranksets as well? :)
Sugino 75 is a lot pricier than I thought, so that's probably out of the question. I was thinking £110ish, tops..

SRAM S300 1.1? £80 including the external GXP BB.

http://www.chainreactioncycles.com/Models.aspx?ModelID=31621

^ Chainring is also black on the CRC stock.

Follow this procedure:

1. Pick a crank that you like the look/price of.
   
2. Look up the bb that the manufacturer makes to go with this crank and the chainline for this pairing. The manufacturer's website is a good start followed by google. For example: On this page you'll see that the chainline for a Sugino 75 crank and a BB-SG75 bb is 42mm.
   
3. Google tell us that the length of the BB-SG75 is 109mm symmetrical . And it's an ISO taper.
   
4. Therefore if you wanted to get a chainline of 41mm for a Sugino 75 crank you would need a 107mm symmetrical ISO bb.
   
   

My basic point is that chainline is dependent on the pairing of crank and bb not just the crank. In general if you use a matching track crank and bb (Sugino 75 crank and 75 bb or Mich Pista crank and Miche Pista bb) you'll get a 42 or 42.5mm chainline. Knowing this you can select and alternative bb (of the same taper) to move that crank to a new chainline. To move a crank 1mm out you need a bb that is 2mm longer.

This assumes that the original manufacturer bb is symetrical....if it isn't you need to google the offset and work it out from there....

In your case the chainring either needs to be mounted on the inside or you ditch the crank and bb and buy any new track bb and crank pair as they will instantly give you a 42mm chainline which will be absolutely fine with a 41mm chainline at your cog.

Sorry this is a bit rambling. Hope you get the idea.

Hm, was looking for black cranks actually (I'm vain, sue me), but that's so cheap, I might just go with that for now.
Unless you have some good suggestions for black cranksets as well? :)
Sugino 75 is a lot pricier than I thought, so that's probably out of the question. I was thinking £110ish, tops..

Go for the Miche Primato Pista Advanced and matching Miche bb. 42mm chainline.

Was recommended to buy Andel cranks by joseph at alienbikes. Found them cheap here. So I'll probably go with those. Currently trying to figure out what size BB to get for them, some sites say 110, and some 107.

The Andel cranks are a good swap out for the RD2 cranks.

Have a look at your BB and check the measurements.

I have a few Precursa bikes with the stock set up of RD2 cranks and 103mm BB and the chain line is 42mm +/- a mm which is OK with the flexible chain that comes with them.

The Andel set I have runs with the Tange 107mm bracket and is OK for chain line.

Good luck !

Allister

I dont understand this. My chainline is fine and my ring is mounted as shown in the photos. Straight as an arrow.

Joseph said that 110mm would be appropriate for the andel cranks, so I went with a Tange 110mm.

Well, apparently the 45mm chainline is a problem with newer RD2s

the answer to this question is going to depend on the fork - rather than the pre-cursa frame. I think dolan supplies at least two types of fork so it's impossible to give a general answer. What fork have you got/getting?

If you bought it with the Dolan track fork then you cannot fit a brake. You also cannot drill the fork because there is a reinforcing screw inside the carbon in exactly the wrong place.

If its the road fork, then I use a short drop 105 caliper on mine.

Hi Baz,

as you have the drilled Dolan carbon road forks , a short drop caliper is the thing you need.

I have used Shimano ultegra, 105 and D.A. as they are all the same dimensions, campag brakes don't have the adjustor on the stirrups now but it's on the lever so that's a bit trickier.

Any lever for drop bars will do as will a small BMX one on the top of drop bars or a TT aero one in the bar end.

If you are stuck PM me as there are a load of bits that would suit in the parts bin.

Allister

If you bought it with the Dolan track fork then you cannot fit a brake. You also cannot drill the fork because there is a reinforcing screw inside the carbon in exactly the wrong place.

If its the road fork, then I use a short drop 105 caliper on mine.

I drilled one of these out a few years ago, seem to remember that I called Dolan first and that, at that time, on those forks, they said fine, drill it out. The hole was filled with resin, no steel screw, tho'.

I've got a brand new Dolan track fork right here and can see the screw from underneath. Its just in the wrong place. Maybe you can drill through it but I'd be worried about the screw deflecting the drill bit.

Good point though, Dolan are excellent with customer services. Just give them a call if you want to drill.

Cheers folks, I went for the black cross lever on the top of the drop bars and Miche performance short drop callipers.

Stops well and looks like it belongs there.

Big love