Shimano 7 speed index lever with 8 speed cassette

[Blindlemon]

Apologies if this is a double post but my original seems to have disappeared.

I have 7 speed Indexing Shimano 600 Ultegra levers and rear derailleur which is SIS compatable to 8 speed. Can I use the levers for an 8 speed cassette using the end stop for the 8th gear or is the difference between the 5 mm spacing of a 7 speed and 4.8 mm of the 8 speed too much for the indexing to work correctly?

Thanks in advance

 

[hamster]

Generally you can get it to work with the extra bit on the shifter. Typically you have to set up the indexing on 3rd or 4th gear to give the mech float best chance to sort out the error.

Downtube shifters are a good way to go as they minimise error from cable outer stickiness.

 

[Blindlemon]

Thanks hamster
Worth trying for the 8 speed then I think. What's the worse that can happen?