8 speed cassette + 7 speed thumbshifters?

[Porschenut]

I don't know where I got the idea, but I thought I could run an 8 speed cassette with my Deore XT 7 speed thumbshifters. Something about the thumbies having an extra index in them.

When I went to have the cables run yesterday at my LBS, they said that I had to use a 7 speed cassette (a little TOO retro for my tastes) and that an 8 speed cassette wouldn't work.

Can someone straighten this out for me? I've ordered a 7 speed XT cassette for my Rocky Mountain Altitude build but I'd rather avoid the extra expense and loss of a gear for a part I hadn't planned to buy.

http://www.retrobike.co.uk/forum/viewtopic.php?t=10514

If someone could solve this problem for me in the next 24 hours I'd sure appreciate it as I could call the shop and have them cancel the order.

Cheers!

 

[rc300]

Do your shifters index ie click 7 times or 6 when in indext mode?
If they do LBS needs some education!

 

[Stick Legs]

Yes.

Shimano ran a 'hidden' 8th click on the XT and DX thumbshifters (post XTII). This was not massive fore sight but a glitch, the range of cable pull is larger than it needs to be for a 7 speed cassette, the click mechanism is just a ball bearing between 2 riged plates, so there is a 8th click but that was just an accident.

Anyway... the spacing of 8 speed blocks is the same as 7 speed, witness the need for a wider freehub body, and lo the 8 speed thumbshifer works!

P.S. beacuse the 8th click is a accident it is slightly 'short', this is not a problem as it affectes the largest sproket, just set up your gears properly as Shimano instruct (by using the second smallest sproket as the refference) and you will have no problems.

 

[leonatico]

Yes, for sure. I´ve used it for years, even with 9 speed chains. If you hear 7 clicks you can use an 8 speed cassette. You can use a 11-28 or a 11-30 without any problem, make sure you keep your cables clean. It usually works better with a rear derailleur thats got a strong spring, like road shimano 105. I use an 8speed SRAM Plasma shimano compatible.

 

[Porschenut]

thanks!

K great! I'm happy to hear that I wasn't crazy. I left a messgae with my LBS to change my order tommorow.

btw, my thumbies are the same model as seen in this picture (stolen from a current ebay auction of the same type)

 

[Stick Legs]

Those are the puppies. They will work 8 speed no problems.

 

[Augustus]

yup, rode to the station this morning using XTII 7spd shifters on a 98 LX 8 spd cassette.

 

[Mad Cow]

The thing about a stronger spring is true, I used a "Raw Power Spring" in mine that was made especially for running 7 speed Shimano mechs with thumbies and an eight speed block.

It's still in the XT mech on the 'dale even though I am only running 7 speeds again (cos the freehub is a 7 speed) and a wheel with an eight speed hub was always a tight fit between the dropouts. Also because it was an absolute bitch to fit so I have no intention of changing it again. Does make seven speed shifting very crisp though

 

[ededwards]

Definitely works, even XC Pro thumbies with an XT rear mech!

That said, worst comes to worst, why not go really old school and just friction it, micro adjusting with your fingers (I could put something in questonable taste here but am far too classy/sober to do so).