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Chainring/Chainstay Clearance

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Chainring/Chainstay Clearance

Old 03-31-22, 12:41 PM
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MacMwnci
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Chainring/Chainstay Clearance

Hi Fellow Cyclists,

I have a question regarding chainring to chainstay clearance. Firstly I'll list my set-up (i.e. frameset and components)
  • Soma Grand Randonneur V2
  • SunXCD chainset with SunXCD 46/30 chainrings
  • Velo Orange 113mm JIS Bottom Bracket
  • Pacenti Brevet 650B wheelset, rear hub 130mm O.L.D
Now, here are the SunXCD drawings for the crankset




SunXCD Crankset Specs

and here are their recommended torque values



Sun XCD Crankset Recommended Torque Specs


Now... on fitting the crankset to my frame I'm left with less than 4mm clearance between the big chainring and the chainstay. I have quite a few bikes (I'm losing count lol) but none of them have clearances that are this tight.

Bottom bracket was fitted (with a Park Tool torque wrench, less than a couple of years old) to 55 Nm (I'm European so Nm it is) and the crank bolts to 40 Nm.

Here's a pic...(post test ride)



Chainring Clearance

Chainring Clearance

Mighty tight, right? ...just about get a 4mm allen key in there.

For good measure I've just refitted the driveside arm and rings tonight. Now, at exactly the same torque settings, I have <4mm clearance.

Here's a pic of the clearance with an un-torques crank bolt



Chainring clearance. Not torqued, 4mm allen key.

My Question: Should I be concerned about this? The bike rode fine on a 10 minute test ride. A bit of chattering in the middle of my Campagnolo 10 speed cassette. Chainline you say? Well...that's not so easy to measure but I'd say, just eyeballing it with a calliper, that it is less than 43.5mm (i.e optimal for a road double crankset according to SunXCD's spec sheet.)

Two more pics



Close of play today: <4mm clearance

Close of play today: <4mm clearance


Look forward to hearing your views!
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Old 03-31-22, 12:54 PM
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If my chain line is correct to the rear cogs, I wouldn't be concerned at all unless the two are actually rubbing. It might be a pain if the chain drops and somehow gets down in there, but I'd rather have the correct chain line as that affects all my rides. A chain drop is rare and a drop that will actually get caught in there even rarer.
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Old 03-31-22, 12:56 PM
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That's plenty of clearance. I've got a few frames with less than that and never had a problem.
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Old 03-31-22, 02:40 PM
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Originally Posted by dsaul View Post
That's plenty of clearance. I've got a few frames with less than that and never had a problem.
+1. My fixed-gear has hardly any clearance, maybe a millimeter. No problems.
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Old 03-31-22, 06:06 PM
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How does the chainline look? If I found the correct specs for your Soma it comes with 132.5 mm rear spacing so either 130 or 135 rear wheels can be used. What are you using?
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Old 03-31-22, 06:25 PM
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Looks fine, send it.

The only other option (if it is available) is to step down the 46T & re-cog the cassette to obtain as close as a gear ratio as you had before.
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Old 04-01-22, 01:55 AM
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Many thanks everyone for your reassuring replies. I'm much relieved! Time to get riding now that spring is here then. Bye bye Finnish winter! Guess it's time to send it packing, eh.



mitchmellow62 - yes, that's right, 132.5 O.L.D. is a clever design. I've a 130mm hub fitted so standard modern road chainline.

Happy cycling to you all!
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Old 04-01-22, 05:06 AM
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Originally Posted by MacMwnci View Post
Many thanks everyone for your reassuring replies. I'm much relieved! Time to get riding now that spring is here then. Bye bye Finnish winter! Guess it's time to send it packing, eh.

mitchmellow62 - yes, that's right, 132.5 O.L.D. is a clever design. I've a 130mm hub fitted so standard modern road chainline.

Happy cycling to you all!
If it really matters, and you want a bit more space thereÖIím reading that there are spacers you can get to put on the drive side to move the crank/rings out 2-2.5mm. But the NDS cup canít have a lip on it. And then if you do this, you may also want to add a spacer on the inside of the rear gear cassette. See these these links https://groups.google.com/g/sfrandon...8ek0HA68?pli=1

https://www.amazon.com/Bottom-Bracke...Bracket+Spacer


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Old 04-01-22, 06:28 AM
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Cheers Dan. Good info there. It had also crossed my mind that this could be an option
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