Dolan Pre cursa chainline?

TONY.M

OK, this week I became a proud owner of a new Dolan Pre Cursa. Unfortunately I was having a problem you can read about in the thread here. http://www.bikeradar.com/forums/viewtopic.php?f=40004&t=12891747

It has now become clear that I can not get a 42mm chainline with Stronglight 2000 cranks as the spider touches the chainstay. Obvoiusly this is very frustrating and there is stacks of clearance with the cranks on my Planet X frame. The chainstays flare out a fair bit on the Pre Cursa and it can take up to 32c tyres so. I am beginning to think that the new frames are slightly different to the older ones but really I don't know.



I am wanting to know if anyone here who has a Pre Cursa have any problems with chainline? Also do you find that a 49mm chainring is very close to the chainstays?

Many thanks

CYCLESPORT1

Longer bottom bracket axel :?:

TONY.M

CYCLESPORT1 wrote:

Longer bottom bracket axel :?:

Thanks, but then the chainline would not be 42mm. The photo was taken with a 107mm Stronglight BB.

CYCLESPORT1

If it was 44mm would it not still run smooth/stright enough :!:

TONY.M wrote:

CYCLESPORT1 wrote:

Longer bottom bracket axel :?:

Thanks, but then the chainline would not be 42mm. The photo was taken with a 107mm Stronglight BB.

TONY.M

CYCLESPORT1 wrote:

If it was 44mm would it not still run smooth/stright enough :!:

TONY.M wrote:

CYCLESPORT1 wrote:

Longer bottom bracket axel :?:

Thanks, but then the chainline would not be 42mm. The photo was taken with a 107mm Stronglight BB.

It may be OK but I would like to keep as close to 42mm as possible if I can.

I'm still interested to hear from folk who ride Pre Cursas how (or if) they manage to get a 42mm chainline and what set-up allows this.

Cheers

giropaul

My thoughts on this would be:

- Why 42mm? Standard track chainline for 120 back ends is 42.5mm, so going to say 43 wouldn't be an issue.

- The cranks look very like the current Campag Pista design (I know they aren't) - the axle for these is 111mm!

http://businesscycles.com/tr-refspec.htm#chainline may give some help, but it doesn't mention stronglight cranks. I'm taking it that your cranks are pista cranks - not singlespeed for e.g. time trialling ?

- Is your rear hub a "proper" - i.e. competition pista type, track hub that's set up for 42.5mm chainline. I've seen issues with "road-track" hubs that are set for a narrower chainline.

- if all else fails, use a Campag, Shimano or Miche pista set of cranks.

TONY.M

giropaul wrote:

My thoughts on this would be:

- Why 42mm? Standard track chainline for 120 back ends is 42.5mm, so going to say 43 wouldn't be an issue.

- The cranks look very like the current Campag Pista design (I know they aren't) - the axle for these is 111mm!

http://businesscycles.com/tr-refspec.htm#chainline may give some help, but it doesn't mention stronglight cranks. I'm taking it that your cranks are pista cranks - not singlespeed for e.g. time trialling ?

- Is your rear hub a "proper" - i.e. competition pista type, track hub that's set up for 42.5mm chainline. I've seen issues with "road-track" hubs that are set for a narrower chainline.

- if all else fails, use a Campag, Shimano or Miche pista set of cranks.

Hi,

I want to keep it as close as I can to 42mm so I can use my wheels from my other track bike without adjustment and to keep the Q-factor the same on both bikes as the cranks are identical.

Stronglight recommends their 107mm BB for this crank to give a 42mm chainline. The cranks are a popular track specific model http://www.planet-x-bikes.co.uk/i/q/CSS ... 0_crankset I have a 48t chainring on and plan to use a 49t which would bring it even closer to the chainstay.

Basically the problem is that the chainstays just flare out too much. I should have taken a photo of my Planet X track with the same crank and BB which would show lots of chainstay to crank clearance. I might do this later if I get a chance.

Cheeers

TONY.M

Spoke with a mechanic at Dolan. Nice chap and he suggested a 110mm BB as that is what they used with the Miche cranks they use, He acknowledged that the Pre Cursa could have issues with some cranks due to the wide chainstays but they were usually able to make them work without resorting to spacers at the rear hub.

I have ordered a 113mm BB from CRC and hope that this solves some of the issues but I feel that I may need spacers at the rear hub at least with this crankset which I don't really want to change if possible.

Tony

BigSpecs

Did you get any conclusion with this?

I was thinking of the same combination of pre-cursa with stronglight cranks.

Did you get it to work? I would be using the bike exlusively (so no inter-compatibility issues) but may use two sets of wheels (training and racing).

Thanks for any info.

Colin

kilo

BigSpecs wrote:

Did you get any conclusion with this?

I was thinking of the same combination of pre-cursa with stronglight cranks.

Did you get it to work? I would be using the bike exlusively (so no inter-compatibility issues) but may use two sets of wheels (training and racing).

Thanks for any info.

Colin

theres a bit in here about pre cursa chain lines, which may be of help;

http://www.glasgowwheelers.com/tommysTr ... ations.php

BigSpecs

Thanks Kilo,
It does look as though a longer BB axle is needed if using the pre cursa with the stronglight.
I was at the Chris Hoy the other day and they have the pre cursa as the hire bikes. Wish I'd looked what chainset they have on them. They seem to work fine, whatever they are.

kilo

should have added I've got an old pre cursa in the loft with the s'light cranks with a 48t on them and it is very tight tween stay and chainring with the recommended bb - perfectly rideable but you couldn't get a 49t on

pinarellokid

I have a strong light 2000 49t chainset on my pre curse and a 113mm. BB. And have no problems with chain line, running navigator wheels.

TONY.M

Hi Colin,

Sorry about only seeing this post now. In short no it it still not perfect.

I have come to the conclusion that my particular Pre Cursa (6 months old in size 52 first of the blue painted batch) is not suited to a 42mm chainline. Some others have not had the same issues with their Pre Cursas in different sizes or with older frames thus leading me to believe that there was a design change at some point.

Dolan were not really able to offer many suggestions (though they were nice enough). They used 110mm BBs (Acor brand) with the Miche Primato crankset but this fouls the chainline somewhat. I bought a Miche Primato crankset to try this out as the Stronglight reportedly has a very fat crank spider but the same issue occurs of the spider hitting the wide chainstays before the chainline is matched.

Two weeks ago I used spacers to push out the rear cog on the hub about 2mm which brought the chainline noticeably closer but unfortunately it was spaced slightly too far out and I stripped the hub threads during the first standing start... Doh! :x

Anyway could any of those with more experience than me tell me what is truly an acceptable chainline for track sprinters? Is 4mm too far out or is this safe and acceptable? I can get the chainline to match easily with my Planet X carbon frame as the chainstays are a lot narrower so it was not a problem for me until I bought this frame last year. I have not been using this frame more than twice since bought as I am apprehensive of a failure by throwing a chain at speed but perhaps I am fussing over not much - please tell me this is so.

Cheers

Tony

BigSpecs wrote:

Did you get any conclusion with this?

I was thinking of the same combination of pre-cursa with stronglight cranks.

Did you get it to work? I would be using the bike exlusively (so no inter-compatibility issues) but may use two sets of wheels (training and racing).

Thanks for any info.

Colin