Chainring Spider Touches Frame

Chainring on inside of spider = pig ugly

yeah its not the best but it works

I was shocked to see the Boardman SS thing at halfords was *designe*d to be on the inside! looks gash

Longer BB + Chainring on inside of spider

Yes, this would work. Not really that bothered about the look.

Need to work out exactly how long the BB should be.

Actually, just saw a video on chainline http://www.fixedgeargallery.com/columns/bobgarage/indexb.htm

OK, looks like the solution to my problem is that I need to redish the rear wheel(plastic pedals).

However, the problem I have is that I have a set of Ambrosio Track Hubs hubs with sealed bearings & double sided fixed threads. I think this means I can't respace the rear hub in the same way it's done in that video.

However, can't I just put a spacer on the non-drive side of the hub to move the wheel over a few mm? (The problem then is that I would lose the double sided feature of the hub.)

Getting there...

The thing missing from your drivetrain specification so far is the sprocket. What is it, and have you mounted it the right way round? You hub doesn't need to be touched, it should give a chainline of between about 41mm and 43 mm depending on the sprocket. Have you checked the frame alignment? That could f-up your chainline too. Really, something is wrong somewhere if you're trying to get the chainring so close to the stays on a steel bike. My fat stayed aluminium track frame (no dimples or bends in the chainstay) will take a >57T ring without any trouble.

Hi, this is the sprocket I've got from SJS Cycles. 16T Fixed Sprocket 3/32 Inch Plated Steel

It's screwed on thread first to the rear hub i.e. the flat side of the sprocket faces out from the wheel. If it was on the other way, it would move the chainline into the bike by 2mm or so - understand?

Maybe it's time for a different frame?

If it was on the other way, it would move the chainline into the bike by 2mm or so - understand?

Yeah, I was just checking for any easily resolved dumb errors.

How are you measuring chainline? Vernier calliper method (which gets you absolute chainline, but only if the frame is perfectly straight and symmetrical), straight edge clamped to the chainring method (which works regardless of frame problems to give precise relative chainline) or the gold standard surface plate and dial guage method?

Chainline measuring thread:
https://www.lfgss.com/thread34501.html

Actually I was just looking at it and the chainline isn't too far off if I file down the problematic part of the spider. If I were to mount the chainring on the inside of the spider, whilst it would probably sort out the chainline by being a couple of mm closer to the bike, I would have to get a longer BB (I'm trying to avoid that).

I could probably get away with putting a 1mm spacer on the rear cog (the thread won't allow for much else I don't think). I think that'd sort it out actually. Ta for the advice.

Actually I was just looking at it

Don't just look at it, measure it.

I have this problem too. Perfect 42mm chainline leaves the spider of my 75s about 1mm away from the chainstays. When I stand up and pedal to the max it goes scrapy scrape.

only way to avoid it is not have perfect chainline. Or, new rear wheel with Paul hub to use a 44mm chainline and then re-adjust the Phil BB for perfect chainline. yay more money to spend.

As already said a few times in this thread, you need to put the chainring on the inside of the spider and get a longer bottom bracket. No other options unless your going to file the spider down.

I did this recently. Needed a 110mm ish BB but inside of spider hit stays. So put chainring on inside of spider instead and worked out I then needed a 119mm bottom bracket instead. Works fine now.

Lots of good advice here. That photo looks very wrong. The BB is obviously for a double and the frame was prob not designer to fit a big track ring. Even with a longer BB the chainring will still be snug up against the chainstay. If the chainline is not right with your current setup then putting the chainring on the inside of the spider and fitting a longer BB will not improve the situation, it will actually make the chainline a couple of mms worse. I think the frame is out of whack. From the info you've given on the hub I'm guessing it's probably not the dish.

How did the bike ride before you began work on it? Did it run straight? If your speaking about adding spacers to the hub setup then it means you have plenty of room to move the rear dropout closer together.