Orbea Gain F40 chain jumping off front chainset

LukeJolyon

Finding my (electric) wheels
Sep 7, 2019
11
2
London
Hi folks - just wondered if anyone has had this problem, or can tell me what it might be, as my LBS - and Velorution - have so far not been very helpful.

My bike is an Orbea Gain F40. It's been fantastic since I bought it in July - so good that I have used it for my 9-mile workday commute ever since. Just over 1,000 miles according to my bike app.

In the last 2-3 weeks though it has developed an infuriating tendency to cause the chain to come off the front chainset. What seems to happen is that when I have it on the smallest gear (9th) at the back and have been powering hard, with maximum boost, then slow down relatively quickly, the chain is kind of thrown forward, as though the rear cassette is failing to slow down at the same speed as the front chainset. I went out tonight to study this, so can confirm this is more or less what is happening.

My LBS glanced at it and said it might be the rather inadequate looking chain guard - a piece of plastic that is fixed to the seat tube and sits just above/inside the chain near the chainset. It did look to be out of line. He tightened this and moved it closer to the chain. However, on my usual commute today the same problem occurred. I have tried to check the chain for wear and tension, and the derailleur for alignment issues, but can't see anything obvious. Then again, I am not a bike mechanic. My fear is it is something to do with the way the hub, with the motor, is freewheeling. If it is still rotating with some speed and force and not slowing down with the rest of the chainline, this might explain it?

Anyway, views from more expert pedelecs would be much appreciated. The bike is still under warranty but when I pointed out to Velorution I had bought it on their recommendation, after trying one out in their shop, they said because I had bought it via mail order from a shop in the Lake District (because Velorution had sold out), I would have to take it back there!
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
12,918
5,046
57
West Sx RH
Robgul has posted here before and is a frequent poster on Cycle UK forum, he rides a gain and is a bike shop owner so might be able to help.
 

DanD

Finding my (electric) wheels
Oct 28, 2019
10
7
It could be the freewheel jamming slightly due a fault with the pawls. When the bike is stationary, try turning the cranks backwards at various speeds and see if it locks up at all. If it does I think you'rd best contacting the retailer for support as you shouldn't have to replace the freewheel after only 6 months.
 

LukeJolyon

Finding my (electric) wheels
Sep 7, 2019
11
2
London
Thanks DanD - tried that - runs OK, but the LBS do think it's a freehub issue and are looking at it now.
 

LukeJolyon

Finding my (electric) wheels
Sep 7, 2019
11
2
London
Update (for anyone interested) - LBS says freehub issue so has now gone back to original retailer for a warranty repair....
 

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