clay to pvc flexible adaptor sizes

[elmsoft]

I'm fitting an inspection chamber into an existing "old" clay drain. I bought two flexible adaptors ( screwfix) which are marked as adapting 110mm to 122-136.
Being a timid soul, I measured the circumference of the existing glazed clay pipe , before cutting it. The circumference is 440mm which I calculate makes the outer diameter 140mm. ie 4mm outside the stated range of my adaptors.
A quick search online doesn't show any 140-110 adaptors.
Common sense suggests that 4" clay is 4" clay and that Screwfix adaptors will fit. But I am nervous about that 4mm difference and reluctant to fire up the Stihl saw till I'm sure. Any one got any insights?

Thanks

 

[Nige F]

Did you measure the circumference with a piece of string and measure that ?

 

[Ian H]

You want an AC4000 for 4” clay, that says the same sized as the Screwfix one but it definitely fits.

 

[elmsoft]

Did you measure the circumference with a piece of string and measure that ?

Yes, I used several methods and came up with the 140mm diameter figure.

 

[elmsoft]

You want an AC4000 for 4” clay, that says the same sized as the Screwfix one but it definitely fits.

I kinda think that 5mm is not a lot of stretch for a rubber adaptor. But I have the nagging doubt that it is not "really 4inch pipe" . Just wanted to check if there is weird stuff out there! Guess I am just being paranoid!
Thanks

 

[nickjb]

They do stretch quite well but not when they are cold. A little soak in warm water softens them up nicely.

 

[elmsoft]

Ok. I think I need to man-up, fire up the saw- and have a heat gun handy!
Thanks to all of you for the input.

 

[MeldrewsMate]

And get some silicone grease/lube to ease it on.....oh, er!

 

[Ian H]

Put it on dry, it will be reet