Slipping chain

[wellington 1]

Done 5,000 miles on a Boardman bike with shimano 105 group set. Chain started to slip, so changed the chain, then the cassette but still its slipping only on the big ring. Cannot locate a replacement shimano 105 50t ring, is there an alternative which would fit?

 

[Sharky]

Do you mean that the chain is slipping on the big chainring itself, or slipping on the cassette when in the big ring?

And by slipping, do you mean that the chain rides over the teeth?
It is rare for a chainring to be so worn that it doesn't hold the chain in place. Pictures of the chainring would be useful.

TA make shimano compatible chain rings.

 

[brucers]

As per above depends on what you mean you mean by slipping. It could be the gear hanger needs adjusting. It could be it needs a new cable. If it is jumping from one cog to another, then either of my 2 suggestions could apply.

 

[andrew_s]

A chainring that's worn enough to slip is very obviously knackered, so check gear adjustment etc first.

(the teeth to the right were further damaged as a result of slippage)

Compatible chainrings:
https://www.spacycles.co.uk/m8b0s210p3387/SPA-CYCLES-130-BCD-Zicral-Outer
or
https://www.spacycles.co.uk/m8b0s210p3054/SPA-CYCLES-110-BCD-Zicral-Outer
The latter would be for compact double - i.e. inner ring smaller than 38T

 

[Ajax Bay]

It's not clear from the symptoms what's going on here. New chain and cassette should not slip. Does the OP get the same 'slipping' effect when in the smaller chainring, if they give it a good welly? A worn chainring is an unlikely cause, unless a cheap one (and I'll assume the OP has a Shimano one). Maybe the OP will return and help us help them.
Andrew - I don't think you can tell what rings might be compatible for "a Boardman bike with shimano 105 group set".
Which is why the OP won't get a useful answer to that part of his Q.
4 bolt, 5 bolt?