7-8spd compatibility / conversion
 

I got my roadie the year before road STI came out and have coveted integrated levers ever since. I have a triple crank Shimano 3X7spd gruppo (500EX? long cage rear der, pretty much a soft MTB drivetrain). The problem is, no STI lever/shifters were made advertised for 7sd.

Is the cog pitch the same between 7 and 8spd, so I could use an 8 spd shifter? Or did the spacing change like it did from 8 to 9 spd?

If it's compatible, does anybody a set of 3x8 shifter/levers for sale? 105 or Ultegra preferred.

If I wanted to upgrade the cogset to 8spd, would it fit on my 7sp freehub?

Thanks.

Within a given brand, 7-speed, 8-speed, and even "ultra-6"-speed cog-to-cog spacing should be close enough to permit indexing to work properly, provided that you have enough range in your derailleur and shift levers.

Converting from 7 speeds to 8 requires a 4mm longer axle and a wider plateau on the freehub body. Sheldon has a useful article on Shimano's various systems and how to interchange among them.

have a look at Highpath engineering for cog spacing:
http://www.argonet.co.uk/highpath/cycle_/faqs.htm#index

the bad news is that Shimano 7 speed is not compatable with Shimano 8 speed (4.8mm to 5mm cog spacing).
The good news is that it is compatable with Campagnolo 8speed.
Get yourself an old Campy ergolever and derailler, and you can use your current 7speed cogsets.
Alternativeley, use Marchisio cogs and spacers to select the cog spacing you want (eg 4.8 or narrower)

A less expensive approach to the cassette issue would be to buy an 8-speed cassette and just take one cog and spacer out. Then you would have 8sp spacing. You might need a little shim between the largest cog and hub in order to get the lockring snug enough to lock the cogs down. If you get the cassette from Harris Cyclery and tell them what you are doing they can tell you what you need. As someone mentioned the 7-speed freehub body is shorter than the 8-9 sp body (same body for 8 or 9). Are you sure you have a freehub/cassette arrangement vs a 7-sp freewheel? If you are not sure of the difference, refer to Sheldon Brown's articles. If you have a freewheel, you can just thread on an 8-sp instead but you would probably need the longer axle. If you have serviced you own hub bearings, changing the axle is no big deal.

There are often (NOS) new old stock 8-sp STI levers for sale on eBay.
Regards,
Raymond

Thanks for all the great tips folks. Since I can't directly use an 8 spd shifter on the 7 spd cassette, I'll probably just convert it to 9 spd (If the frame has enough clearance). That'll make it easier to get service parts for the next few years.

Cheers.

Another question - several folks referred to "Sheldon" - I didn't know who this is, but Yahoo came up with bike stuff at www.sheldonbrown.com - looked like a good match. The problem is, I get no repsonse from that server. Does anybody know if 1) that is the right reference, 2) has the website moved, or 3) is it down?

Thanks.

This might help. Its a more direct link to the tech. info

http://www.sheldonbrown.com/harris/index.html

Thanks for printing the full link. sheldonbrown.com should work fine (and give you a window into Sheldon's family's myriad activities and interests), but servers are known to go down at times.

I can't get there from my office - DNS errors. I'll try from home.

Try http://192.41.51.124 and look for Harris Cyclery.

7-8 speed conversion
 

If you have not converted already , you can use 8 speed sti shifters on a 7 speed rear,they work beautifully ,you just have to limit the rear derailluer so that it doesnt go into the spokes ,your just going to use the firt seven positions of the shifter. You can find some good deals on new old stock 8 speed shimano shifters on ebay. I use rx100s on mine with a new 105 rear derailluer and seven
speed cassette. If you want brand new you can use Sora but I hear they are cheap.

How picky are you?
 

I'm using 7-speed Shimano bar ends with an 8-speed cassette on one of my bikes. It's OK for casual use, but it doesn't shift as nicely as matched components. Sometimes I have to finesse it up an extra gear then back down one. You can minimize the problem by adjusting the cable tension so that it's spot-on in a middle cog. That way the mismatch is divided into two directions.

I had asked the same question about a year ago, and the advice given worked perfectly. I used the Sora STI shifters with the 7 speed cassette by setting the limiting adjustment. The Sora provided the STI for the triple in front also. I have been using it since then without a problem.

www.loosescrews.com has 7-speed Sora shifters for sale. Shimano did make upgraded versions, as I am still using a 7-speed RSX STI group, save for a 105 rear der.