brianleach wrote:I thought this would be easy.
brianleach wrote:My son wants to fit a chain guard to his Ridgeback Flight to prevent shoe and trouser oiling.
Hmm. He doesn't understand bicycle fashion much then.
I looked at these Thorn chainguards a few months ago.
brianleach wrote:The largest chain ring is apparently 52. Would either of these fit
Probably not. That would be for an MTB-like chainset with four bolts. And it might be a bit small.
Probably too small. Might be OK. It's listed as for a 50 tooth chainring. Phone SJS to find out the exact diameter. There'll be some more questions to ask about fitting...
You need to know the bolt pattern of the chainset. Which you can work out from knowing the model of the chainset, or this:http://www.sjscycles.co.uk/article-Bolt ... DChart.htm
When I asked SJS, they said that you just got the disk, and no bolts or spacers.
You'd need to replace the bolts holding the middle & outer rings on with longer bolts, and with some kind of spacers between the outer chainring and the chainguard. Washers would probably work - someone else might have a better idea.
The spacers are necessary, so that the front deraileur can still work, and so the chainguard isn't just resting on the side of the big chainring, stopping the chain from going on.
There could be another problem - usually, the big ring has a stud set into it, to prevent the chain getting stuck between the crank and the chainring. If you want to use one of these Thorn disks, you might need to cut/grind away part of the disk behind the crank to make room for this stud. I think you'd have to try it on your son's chainset to see if this was a problem.
A more extreme, but easier, answer would be to replace the big chainring with one of these Thorn disks, like a bash guard for a downhill MTB. For a lot of people 52 tooth chainrings might as well be bash guards.
I'd like a chainguard with a much bigger radius at the edge - it sems that these disks are only 2mm thick.
So no good answer, unless you like tinkering.
I was stubornly determined to get chainguards of some sort on all our bikes, as we don't wear lycra. About the only chainsets designed with/for ring-mounted chainguards are low end MTB/hybrid chainsets. And they are hard to get with chainguards fitted, especially in the UK - one LBS looked up a Shimano chainguard part for me, and Shimano UK didn't even list it. Ordered some bits from the US, some from Germany. Kids have Shimano Alivio MTB chainsets, with ring-mounted chainguards from a different chainset, that I ordered from Germany, and Dremeled to fit.
Once Upon a Time, I thought it was quite common to have quite solid aluminium ring-mounted chainguards.
Don't drive on the railroad track.