Replacing sprockets when changing the timing chain

[Ollienorth 0]

I may be being really stupid but I haven't seen a mention of anyone replacing the sprockets when changing the timing chain. Everyone seems to do the tensioners and the chain but not the sprockets. Surely these ware as well?

[joebloggsVR69 0]

You mean the pins? I changed them as well as everything else

[Geo 0]

I don't think the chain or sprockets wear that much on the vr, it is mainly the upper tensioner pad that causes problems. Most people do the chains at the same time as they aren't that expensive but IMO it's not really necessary to do the sprockets on the VR6 engine.

[Kevin Bacon 5]

Only cyclists and motorcyclists replace chains and sprockets as a unit, otherwise the new chain jumps teeth on the old sprocket.

 

The cam sprockets are hardened enough to not need replacement.

 

And considering the duplex VR cam sprockets are £75 + VAT each, you might want to reconsider the notion of replacing them! And you need to also add the intermediate and crank sprockets aswell, plus the chains, guide rails, tensioners etc...you're looking at about £500!!

[dr_mat 0]

The timing chains don't exactly carry a lot of load here, they're not subject to the same forces as the drive chains on bikes and heavy machinery. They're only turning a couple of camshafts against a few valve springs..

[Geo 0]

Yeah but if they let go you are left with a big mess!

 

On some engines such as BMW's S14 engine it is recommended to change the sprockets at the same time as the chain but it's not generally necessary.

[Kevin Bacon 5]

The timing chains don't exactly carry a lot of load here, they're not subject to the same forces as the drive chains on bikes and heavy machinery. They're only turning a couple of camshafts against a few valve springs..

 

Have you tried turning a pair of cams by hand then Mat?

[andy 0]

I have....the word evil springs to mind.

[dr_mat 0]

No kev. But I'll bet it's not as stiff as turning a 20vt cam, with nearly twice the valve count. Your point being?

And the 1.8t uses rubber belts..!

And it certainly doesn't have to transmit 100lb/ft like a bike chain.

I'm no expert, but I've never ever heard of anyone recommending replacing the sprockets.

[Kevin Bacon 5]

I don't endorse replacing the sprockets either, I was merely taking issue with your comment about cams not presenting hardly any load to the timing gear without first having spun them over by hand to find out for definite, but then I should have read your signature really, shouldn't I.....which is a cop out if ever I saw one!

 

Anyway, what makes you think the 20VT cam lobes are anywhere near as agressive as the VR6 ones (and they won't be being forced induction), or the springs as strong? Some motorbikes use gates belts to drive the rear wheel (some use shafts too), so your point about those, is?