8 Spd to 9 Spd change - what's essential?

[Colin]

Hi,
during the total rebuild of my XP-X, I'm considering changing to 9spd from the existing 8spd.
The 8spd components are original from 1997, XT Rear, LX front.

I have a new set of 9sp combined changers and disk levers, so am planning on using them for the Avid BB7 cable disk brakes I will be fitting.

I also have new 9spd rear cassettes ready to go (11-32 or 11-34).

New Front and Rear derailleurs are listed as 8sp or 9sp compatible. ( I'm aware of checking their capacities)

So my question is, how essential is it to have specific 8sp and 9sp front and Rear Derailleurs or is it OK to stick with the 8spd ones with 9spd shifters up front?

I know I'll need to change the chain (probably to a SRAM 971 or similar)
Will the OEM Sugino 8spd crank set work Ok with a 9spd chain?

What's your experience of doing a 8 to 9 spd change?

Thanks
Col.

[w2zero]

I recently put a 9sp cluster on the rear of my 855.  It has original XT front and rear derailleurs, original 42t and 32t outer and a newer inner 22 steel cogs on the original Impel crankset up front.  It is shifted with SRAM 9sp gripshifters and has a new 9sp Shimano chain.  I had some concern that the front might be sketchy on the shifting but it isn't.  The rear shifts are very fast and smooth.  I expect that all my tools will one day have 9sp when the rest of the world is using the next best thing or the ones after.  

(forgot to mention the derailleurs are circa 1995)

[the converted]

You'll be just fine with the 8 speed derailleurs.  I'm running a similar set up at the moment, and am not having any issues at all.

[fyrstormer]

The spacing between the 9-speed sprockets is narrower than between 8-speed sprockets, so the lateral play in the upper derailleur pulley could be too much and cause the chain to skip. However, that's something you'll discover pretty quickly if it turns out to be a problem in your setup. What you won't notice as easily is that the teeth on the 8-speed derailleur pulleys are slightly thicker and could rub against the sides of the inner links in the narrower 9-speed chain. Being plastic, they'll wear down pretty quickly, but that's not an ideal setup. The same applies to the front chainrings; if they pre-date 9-speed bikes, they'll probably be slightly too wide for a 9-speed chain and the teeth could jam in the inner links when you put a lot of tension on the chain when pedaling hard.

Ideally, you'd want to replace the chain, the cassette (obviously), the chainrings, the shifters, and the derailleurs. Realistically speaking, though, you can probably leave the derailleurs alone, and the chainrings too as long as they're new enough that they're 8/9-speed compatible.

I've upgraded virtually everything on my bike, but I opted to use 8-speed parts just to avoid having to deal with replacing them all at once. I've never wanted for lack of a 9th sprocket anyway; some would say the lower gear ratio helps when climbing, but even with the 8 speeds I have now, in granny-gear I can put enough torque on the rear wheel that I can't maintain traction on steep climbs, so having an even lower granny-gear is more a theoretical benefit than a real one.

[w2zero]

My 11/34 went on the seven speed cassette body sans the 34 to make an 11/28 with 8 cogs.  The nine speed cluster from my infamous box lot stash is an 11/27 that is drilled and has alloy spiders on the inner cogs.  A 27x22 is plenty low for me in granny short of walking and whining.

[jeffhop]

the rear deraillieur will be fine you will have no issues with it at all, you have  got to use a 9 speed chain though otherwise everything else will work fine.