How far can a grape vine be cut back?

Kamo

We have a grape vine and a clematis growing over an arbour/archway which is collapsing and needs replacing. The vines really intertwined with it and needs cutting back but I'm not sure how hard it can be cut back, the more we can cut back the easier it will be to rebuild the arbour.
Anyone have experience with grape vined and have an idea of how much we can prune back without damaging the plant?

Dovefromabove

🤔. Is it possible to leave it until early winter?

This https://www.rhs.org.uk/advice/profile?pid=284

and this http://www.my-grape-vine.com/blog/pruning-an-overgrown-or-never-before-pruned-vine-part-2/

may be helpful 

Good luck 👍 

BobTheGardener

It's too late to cut it back now as the sap is rising and it will probably bleed to death, so they are only pruned after all the leaves have fallen and weather is still cold.  This is usually done between about October to February, when you can cut them back as hard as you like.  However, unless you can wait that long I think you will need to risk it as the structure clearly needs work.  You can always buy a new vine if it dies - they grow very quickly as you know!  It is best to train them to form a framework then, in winter, cut off all growth from the main framework stems to 2 buds.  The new growth from a bud can easily reach 2m in one season.

Kamo

Thanks everyone, unfortunately I can't wait till winter as the arbour is likely to collapse soon and could take the plants with it.

Thanks for the links they are really useful, the grape is only just starting to bud so I might just get away if I cut back as little as possible. They are both inherited plants but I'd like to preserve the grape as it looks like it's been growing a long while, I'm not too worried about losing fruit for this year or even the next as I've never had usable fruit from it before. I think it has gotten quite overgrown so as long as it survives, and this is my main concern, I think it will benefit from the pruning. 

Big Blue Sky

I once cut one of the branches on my grape vine in late March and it was already too late as it was bleeding for a whole day, literally dripping. It was only one branch so the plant has survived, but watching it loosing its sap so fast for so long was heart breaking, since then it’s only January for me to trim the grape vine. 
Sorry, it’s probably not what you wanted to hear.