73mm BB shell on the bike. The old Shimano BB had 1 plastic spacer behind the non drive side cup. Can't remember why, but I built it like that. Everything was lined up nicely.
The Hope manual and everything online says 1 plastic spacer behind the drive side cup.
This has pushed the cranks and sprocket outboard. I can't use my chainguide because it doesn't reach and the chain line looks shocking.
Is there a good reason I can't just move the spacer to the other side? If it looks wrong, it's wrong innit?
Also just realised I forgot to put one of these in. They're labelled as road and MTB in the manual but it doesn't say which is which.
If I put it on the drive side like the diagram the cranks will be even further out.
That looks like mine did, I just stuck the spacer on the other side. Chain line was always crap with them though even with that. Also recommend getting a stock of the pre load collar bolts in, a 2.5mm hex head is a rubbish idea
is the chain ring flush to the crank? does it have an offset? just done a single ring on my front and had 3mm spacers in between the ring and spider. Would 3mm help in this situation? maybe easier to do than removing the BB?
After I posted last night I removed the BB and switched a spacer over to the non drive side. It's slightly better but obviously only by 2.5mm. I still have good clearance on both sides between the cranks and chainstays.
The sprocket is flush to the crank. Maybe one of those steel shims is supposed to go between them.
I'm stuck at work all day, I'll have another look tonight.
I’ve realised it’s you on the childrens crank thread, are there any special instructions with the rimpact? All the tech in that chainring must affect the chainline?
Yes, I started the tiny crank thread. That was before I caved in to curiosity.
Nothing in the box with the Rimpact. The online instructions are all about servicing.
I might have to email Hope and or Rimpact before I ride it and break something.
I assume you can measure chainline?
If not then try this - your chain should be straight when in the middle cog, if 11 speed or very slightly left or right when in the middle two on a 12. An imaginary straight line (or string) from the centre of the chainring teeth to the centre of the cassette.
Hope this helps, hope you’re not insulted!
I assume you can measure chainline?
If not then try this - your chain should be straight when in the middle cog, if 11 speed or very slightly left or right when in the middle two on a 12. An imaginary straight line (or string) from the centre of the chainring teeth to the centre of the cassette.
Hope this helps, hope you’re not insulted!
Not insulted at all. The problem is that the chain is straight when it's on the smallest sprockets.
So 3mm spacers on each of the chain ring bolts, moving the ring inwards a tad, should set the chainline a little closer to the centre of the cassette. How close is the ring now to the chainstay?
I think you really need to know what your chainline currently is and work from that. Putting a felt-tip mark on the centre of your seat-tube and measuring from tip of chainring tooth to line would give you a close enough idea. I recall that it should be about 52-55mm for a 148mm rear end (check with the manufacturer). Hard to tell from your photograph, but it looks like your chainline is quite a bit greater than spec. Probably best to fix with chainring offset rather than moving the cranks about.
You could also measure from the centre-line to the inside of each crank arm to get an idea how central they sit.
IME, the spacer goes on the drive side. I think it's to leave the option of fitting a bb mount chainguide.
Is the chainring you bought for a boosted axel? IIRC AbsoluteBlack boost rings are designed with 3mm offset so I'd imagine other manufacturers also do this. Just depends what you bought!
From AB site:
- Chainline: Perfect 52mm BOOST148 specific. 3mm offset
Are you using Hope cranks and chainring? If so, check you have the correct chainring. The boost (148mm) chainring is set up for a 55mm chainline, the non-boost (142mm) chainring has a 3mm offset to the inside, to provide a 52mm chainline.
As above - it’s a Rimpact “chainring”…
Chainring looks like this.
I'd also like to reattach my top chainguide. I can't do that right now because it doesn't reach the ring.
Just a thought... You haven't got a Hope 73mm Superboost crank have you? I think they do the standard 68/73 and a 73 superboost. The latter would give you this problem.
Just a thought... You haven't got a Hope 73mm Superboost crank have you? I think they do the standard 68/73 and a 73 superboost. The latter would give you this problem.
You made me panic there!
Just checked my email. I did order a 68/73. I'll check the box when I get home and make sure it's the right crank.
Hope boost/non-boost is in the chainring or 4x104BCD spider offset, with minor adjustment in the BB spacers. is the frame boost or non-boost? Is the Rimpact ring boost or non-boost offset?
Non-boost ring on a boost frame puts the ring too close to the chainstays. I'd imagine boost ring on a non-boost frame would be too far out the other way