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Noticed a slight knock coming from the rear on my old Cannondale. Really only use it for riding with the kids but if I could think of a way to prolong this i would be very happy.
Stripped it down and found that there is wear on the rear triangle where the shock bolts to it . Looks like the holes have become slightly ovalised. Anyone think of a way to breathe new life into this frame?
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If you know of someone locally who has a small machine shop, you could get the problem holes drilled out and some bushes made up.
Drill them out so they're round again and drill the shock bushings the same.
Any way you can get the actual size of the bolts and get some bushes to fit?
You may have to enlarge the holes or something but I'm not an engineer....there's probably better people qualified to tell you how to do it
Righto. Seems you lot came to the same conclusion as I did. So where am i going to get a new bolt from.
Current one is 6mm diameter. I assume taking it out to 7mm or possibly 8mm depending on what i can get. The part that needs to be blind, ie not threaded is 20 mm.
Anyone got any ideas?
two methods
turn a spigot/pin 6.5 - 7mm 9you really dont want to be taking loads of metal out the swingarmin diameter and tap both ends drill out shock bush to suit
or turn up two tophats, bush the swingarm and put a standard bolt in it
Is the shock shaft out of shape too?
If it's just the arm you could fit some Igus bushes from RS Components, will be a pack of ten so you should get another five years out of it.
Or these, 6mm ID, 8mm OD, 6mm OA Length.
http://uk.rs-online.com/web/p/bearing-units-accessories/7506808/
That would be the thing Mickd. Sadly i do not have acces to a lathe. ****less brother in UK does but what chance of him making something for me?
Cheers for the prompt Neil. I had completely forgot about the shock bushings. Checked and they seem OK,clearly made of a firmer cheese then the frame.
So plan#01: drill out the swingarm to 8mm. get ****less brother to make 2 bushes. what to make the bushes from? For some reason Brass sounds like it might be better than Steel but I am not that kind of Engineer. 😉
What think we? Brass or Steel? Or is there a better option?
8mm is a standard shock bush bolt size. You just need new bushings.
And tighten it up properly this time.
Brant, are you suggesting i run a 8mm threaded bolt straight through after drilling the swingarm to suit and replacing the shock bushings?
No, drill out to 8mm, fit 8mm bush.
Part threaded bolts are readily available. Have a look on ebay. It doesn't matter if they're too long as you can cut them down, it's the unthreaded part that matters.
I would just go with the Igus, I use them often and they are a lot tougher than they look.
They also make bike specific parts, known as Iglide I think.
If you are worried about it happening again I would drill out to 8mm and then fit an 8mm OD, 6mm ID top hat bush from either side and bond them in with some loctite (so that can be removed later if needed). Then fit a new bolt through the existing (but fit a new one) shock bush.
Not familiar with full suspension set-ups, does the shock bush rotate in the end of the shock?
get some protective tape on the frame under that cable too before you have a more serious problem.
Jekyll? I'd suggest buying the swinging arm I have in the garage but think postage maybe an issue.
I think I now know what people are saying. Drill frame to 8mm, fit bushes with 6mm internal to frame replace bolt with slightly longer one to accommodate extra width of top hat bushes.
Am I correct? If so could someone point me to a supplier of suitable bushes? I am pretty sure I can find a longer bolt.
Z1ppy, yes I think postage would make buying yours a bit beyond economical repair.
Drill frame to 8mm, fit bushes with 6mm internal to frame replace bolt with slightly longer one to accommodate extra width of top hat bushes.
Am I correct? If so could someone point me to a supplier of suitable bushes? I am pretty sure I can find a longer bolt.
Z1ppy, yes I think postage would make buying yours a bit beyond economical repair.
In my mind, I was suggesting drilling the frame out to 8mm (it's nearly there I guess already), then fitting new shock bushes with an 8mm bore (a common size, because 6mm bolts aren't very strong, and, I guess, might have an issue with fretting holes bigger), and then running a nice 8mm bolt of some description through to clamp it all up nice and tight so it doesn't jigger around as much as it did before.
Alternatively, just put it all back together and tighten it up properly. Perhaps the bolt is bottoming out on itself/thread/something before it's done up right? If it's fastened correctly the shock is mostly held in place with the friction from the faces of the bushing rather than being held like a peg in a hole.
Tbh it sounds more like the shock bushings have gone anyway
Buggeration..... What Brant was saying made perfect sense in my my wine addled state.( not casting aspersions on the advise, it will still make sense in the morning. I do believe that the damage may be beyond friction though ) Now have stripped threads on old bolt due to over exuberance and optimism.
Too late to cut it off with a grinder tonight as I will either loose a finger in WCA style or be divorced due to noise issues.
As a backup plan can anyone link me some bushings that might be suitable? 6mm or 8mm internal diameter.
http://www.mountainbikecomponents.co.uk/items.asp?CategoryID=92&Name=Strong+Bushes
they'll do custom sizes...
Well, I finally got round to having a look at the bike again. Was distracted with a misbehaving Magura HS33.
I removed the crappy old bolt with a Dremel and procured a nice Stainless one. Resembled and lo Brant was correct. Even thought the holes in the frame are worn decent bolt done up correctly eliminates any movement at that point. This is when I realized that TMB467 was also correct in that the DU bush in the shock is most likely the cause. Seems the top hat bushes are a bit loose in the DU one. I am guessing they should not just fall out. Ordered a bush removal tool and some half inch DU bushes from ebay. Hopefully this will sort it for a while at least.
Well bugger me. Bush tool arrived and with 2 new bushes provided it took less that 5 mins to sort the thing out.
Still an annoying thing with loads of propriety bits that when they fails spells the end. For the time being it lives again.