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I have just finished to assemble a track bike (Cinelli Mash Parallax with Sugino DD75 crankset).

Here is a picture of the distance between the right chainstay and the crank spider. I am anxious by how close it is (less than 1mm, probably).

Is it something I should worry about? If yes, what solutions do I have except for picking another crankset?

enter image description here

  • If it's a non-critical part of the spider then just grind off the offending corner. – Daniel R Hicks Jan 21 at 3:11
  • @DanielRHicks the one you see it's the bolt that holds the chainring, so I would say very critical – Alessandro Cosentino Jan 21 at 10:40
  • Can you add a photo of the crank uninstalled from the bike showing the inside face of the ring/spider? The pics of the Sugino DD75 I'm googling don't have that big square chainring bolt boss. – Argenti Apparatus Jan 21 at 13:05
  • Keep in mind that you'd only need to grind off about 2mm to gain sufficient clearance. – Daniel R Hicks Jan 21 at 13:14
  • @ArgentiApparatus This is how it looks also in real life: dolan-bikes.com/media/catalog/product/cache/1/image/1200x/… – Alessandro Cosentino Jan 21 at 13:18
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Answering my own question with some observations I gathered from other forums:

  1. The bolt boss (the knurled metal ring) in the picture is visible only because the chainring was installed incorrectly. When I tightened the bolts properly, the metal boss settled inside the crank spider and I gained at least 1mm clearance. New clearance in the following picture:

new clearance

  1. Both chainstay and crank arms are objects that don't flex much, unless they are of poor quality, but this is not the case for my build.

  2. The biggest risk is the chain dropping and getting trapped in that small gap. In my case the gap is small enough that it shouldn't happen. Moreover, given that it's a fixed gear setup without front mech, the chance of chain dropping are very low.

Source: https://www.reddit.com/r/FixedGearBicycle/comments/4ck3h9/crank_arm_spider_and_chainstay_clearance_should_i/

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If Google is correct the Sugino DD75 is a two piece crank with an external threaded BB. That means you are pretty much out of luck with this crank as there is no way to move to it outboard and away from the chainstay - except if you have some spacers installed and you can move one from the non-drive to the drive side.

Edit:

Another possibility is to add a spacer on the crank spindle on the drive side.

The chainring bolt boss on the spider in you picture looks very square and thick (interestingly, it looks thicker than in pics I googled), so you might have better luck with a different crank.

  • You're correct, it is a two piece crank with an external threaded BB. From Googling around, I see spacers are highly not recommended. I wonder if I will have the same issue with another two piece crank with an external threaded BB, like the Sram Omnium. – Alessandro Cosentino Jan 21 at 11:13
  • The bolt boss is quite a standard one, round and quite thin. It looks bigger in the picture, just because of a magnifying effect, since the picture is taken very close. I will take it off and take more picture. – Alessandro Cosentino Jan 21 at 13:21
  • The cranks come with a spacer, but also with a big WARNING of not using the spacers if not strictly needed, which is frightening. – Alessandro Cosentino Jan 21 at 13:22
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I would not be comfortable with such tight clearance either.

  1. A straightforward solution would be to use a smaller chainring.
  2. The orthodox solution would be to change not the crankset but the bottom-bracket spindle. Depending on your bottom bracket, you may be able to simply adjust your existing bottom bracket so that more spindle shows on the left.
  3. You could insert shims between the chainring and spider. Some stainless washers that add 2 mm clearance would do the trick.

If your chainline is already perfect, then it's going to be compromised, but perhaps you need to move the chainring over a little to improve the chainline anyhow.

  • From the OPs question it's the spider that is close to the frame, not the chainring, so just moving the chainring is not going to help. – Argenti Apparatus Jan 21 at 0:33
  • In a few cases, a conventional threaded setup will have two threaded (and adjustable) cups vs one fixed and one threaded, allowing a minor degree of left-right adjustment of the BB shaft. This is not the norm, however. – Daniel R Hicks Jan 21 at 3:09
  • I think you can safely streak through 2. as well, since the Sugino DD75 is a two piece crank with an external threaded BB, so there is no BB spindle. – Alessandro Cosentino Jan 21 at 10:42

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