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Been noticing a bit of chain suck over the past month on my road bike - i think it's chain suck anyway. Basically when i sprint and then stop the chain almost comes off the big ring - last night it did come of. Front mech is fine (and i wasn't changing gear anyway). The chain kind of sucks down towards the chain stay.
The chain is at the 0.5 stretch mark (so due for replacement) on the park tool measurer. The chain rings are the same as I've had since new, so seen a fair few miles. Probably about 10000km? As I have a spare new cassette (bought ages ago in a sale from ze germans) and a new chain, i figured it was was time to replace the whole lot. I then looked at the price of a new ultegra big ring (120 quid)! Hence I decided I should ask the oracle whether this chain ring is actually worn - the new ones don't have an entirely symmetric appearance.
That's a freehub issue by the sounds of it! The freehub is sticking which means it keeps rotating with the wheel, causing the top run of the chain to go slack and drop towards the chainstay.
Chain suck would pull the chain up from the bottom.
That chainring is far from worn, plus I don't think I've ever heard of or experienced chainsuck in the big ring anyway, seems to be a granny ring thing.
what the monk says, it's a sticky freehub if it's sucking from the top.
check out ebay for new rings ~£70-90 depending on teeth
Freehub or rear derailleur issue I'd say.
Freehub or rear derailleur issue I’d say.
Ok cool. As in freehub is sticky? what kind of rear mech issue could cause it?
Could be freehub bearings not DT Swiss hubs are they?
Got what you described when the bushings had worn in my mavic free hub.
Chain ring looks fine to me.
My experience was that my chain kept slipping under power, and it felt like something was sticking in the freehub, with the chain going all loose momentarily.
My Ultegra big ring was not obviously worn, to look at, but it turned out to need replacing (similar mileage to your, perhaps less).
I bought a new chainset and flogged my crankarms and rings separately on eBay. Someone even paid me £10 for the worn ring (advertised as such).
Could be freehub bearings not DT Swiss hubs are they?
Yep! DT swiss R24 spline ones - it has the pawl system. Is there a known problem? The wheels seem solid.
DT swiss R24 spline ones – it has the pawl system. Is there a known problem?
I had an issue with the freehub on a DT Swiss pawl hub. It had a bit of water inside and had caused the outboard freehub bearing to seize up. At this point I had only done one wet (admittedly long and very wet) ride on the bike. For me it was only noticeable when the bike had been left for a day or two, and would free itself as soon as the wheel was spun. The rest of the bearings in the free hub were all fine. It should be easy to check the outside bearing, and cheap to replace if that is the problem.
This (over 3 forums) is the 6th similar thread I have seen recently.
When the bearings in the freehub itself get knackered they tend to bind up. Off the bike they work fine, on the bike they don't, that little side load kills them.
It is a quick and easy job if you have sockets, hammer, the bearings and some wood blocks.
Pull off freehub body and you can check bearing sizes (can't remember off the top of my head). Then is a case of knocking them out, fit new ones (make sure socket only touches the outer) making sure the spacer between bearings is fitted, and any end spacer you may have (mine doesn't only the end cap).
Whilst off you can also clean out the pawls and regrease. DT specify a particular grease, I did an emergency fit before I went on holiday 18 months ago and used a tiny amount of machine grease with no issues. Just make sure the spring clip goes back on in the right place and doesn't get bent.
Just to add you can knock out the outboard bearing through the middle of the other one using a suitable driver/chisel thingy. For the couple of quid I usually just replace both.
Right i'll check the bearings then! Cheers all