Road Cycling - Shimano 7-speed vs. 8-speed

Just picked up a great little Trek 2300 for my daughter in a 50cm size. It is all Shimano 600, which is a 7-speed system. I want to up-grade to STI shifters and am wonder what all I need? Based on my very limited Shimano knowledge, I am guessing that, like Campy, a Shimano 8-speed fits in the same width as a 7-speed. Is that correct? That I will need the STI shifters (duh!), an 8-speed cassette and the matching 8-speed rear derailleur and chain. Is my guessing correct? Thanks for your help and have a Merry Xmas!!

Just picked up a great little Trek 2300 for my daughter in a 50cm size. It is all Shimano 600, which is a 7-speed system. I want to up-grade to STI shifters and am wonder what all I need? Based on my very limited Shimano knowledge, I am guessing that, like Campy, a Shimano 8-speed fits in the same width as a 7-speed. Is that correct? That I will need the STI shifters (duh!), an 8-speed cassette and the matching 8-speed rear derailleur and chain. Is my guessing correct? Thanks for your help and have a Merry Xmas!!7 speed sora shifters are avaialble. You can't stick a shimano 8 speed cassette on a 7 speed freehub Hub body is too narrow... You can get a loose cog 9 speed shimano cassette,remove a cog and spacer and it will fit. Get a 9 speed chain and shift it with 9 speed STI.No need for a new RD unless the old one is wore out and sloppy. You may need a new FD.

Are you saying that the dropout width on a 7-speed is narrower than an 8-speed (I thought both are 126mm) or that only the freehub body is narrower on a 7-speed hub than on an 8-speed hub?

If I go the 9-speed route with one less cog, how do I keep a 9-speed shifter from shifting the chain off? Will the RD limit stops stop shifting at the 8th cog?

Also, I read nothing good about Sora, so probably do not want to go that route.

Here's a pic. Ain't she sweet. Just the ticket for my 5'1" tall daughter.

Thanks.

Really look at what you have and what you can do with your money.

I gave my brother my old 7 speed. He had limited time to ride and needed a wide range of gearing choice.

I went with downtube dura ace shifters 9 speed index
ATB cassette 11-32
Chain
ATB/MT rear drl.

It sounds crazy but it works and he can join our rides and survive the hill and make up time on the downhill.

Anyway…look at downtube shifter as a cheap way to go and spend the money saved into whatever….wheels maybe…

Are you saying that the dropout width on a 7-speed is narrower than an 8-speed (I thought both are 126mm) or that only the freehub body is narrower on a 7-speed hub than on an 8-speed hub?

If I go the 9-speed route with one less cog, how do I keep a 9-speed shifter from shifting the chain off? Will the RD limit stops stop shifting at the 8th cog?

Also, I read nothing good about Sora, so probably do not want to go that route.

Here's a pic. Ain't she sweet. Just the ticket for my 5'1" tall daughter.

Thanks. Sora shifters work and don't cost a bundle. Don't be blinded by BS.The freehub body for 7 speed HG cassette is about 4.5mm narrower than an 8 speed hub body.. 8 speed uses 130 dropout spacing. 7 speed dropout spacing was typically 126,but many later ones were made with the compromise 128 spacing....Ya block the shift with the low limit screw....Don't be surprised if the TT is too long. A 50 just doesn't fly well with 700c wheels.

ParamountScapin,

Unless I'm mistaken, the bike you've shown has bar end shifters that are considered by many to be just as good as STIs. I'm not doubting that your bike would benefit from a move to STI but it will be marginally better, not substantially. If I had a few hundred to spend on upgrades for this bike, I'd put it into lighter wheels. That would make the bike substantially better on the road.

Cale

I have several Shimano 600 bikes with six or seven speeds and downtube shifters. They work great just as they are. Reliable, quick shifting. If you ever need to replace the brake levers, you spend $30. If you ever need to replace the shifters, $20. Why spend hundreds converting to STI where a broken five cent spring in the brake levers may lead to a $300 tab for a pair of new levers?

Likewise, if you wear out a cog, your LBS can replace just that cog, rather than the whole cassette. A Shimano 600 system from the 1984 to 1989 era represents the all-time peak in the quality/cost/weight equation for a bike drivetrain.

ParamountScapin,

Unless I'm mistaken, the bike you've shown has bar end shifters that are considered by many to be just as good as STIs. I'm not doubting that your bike would benefit from a move to STI but it will be marginally better, not substantially. If I had a few hundred to spend on upgrades for this bike, I'd put it into lighter wheels. That would make the bike substantially better on the road.

CaleGood catch on the barends. Got several set up that way myself. Work well and alot cheaper than STI. The people that 'just gotta have' STI don't buy it tho.

Sounds like I'll an easy sale of my bar-ends when I shift over to STI.

The only difference between Sora and STI shifters for that 7 speed would be that you can't "trim" the front derailleur on the Sora. The Sora "brifters" will also only jump two gears in the rear instead of three. I keep my bike nice and clean, and the Sora shifters work as well as the Ultegra shifters on my other bike. I put new wheels on my older Trek 420, and they had to put a spacer on the hub for the 7 speed cassette. Maybe you should go to a good LBS and ask them these questions. They can measure the dropouts and tell you for sure. When I put a new cassette on the back, the shop used an 8 speed chain for the 7 speed cassette. They said a 9 speed chain was too thin for the gear teeth. I found the 7 speed Sora shifters on Sheldon Brown's Harris Cyclery web site.

The only difference between Sora and STI shifters for that 7 speed would be that you can't "trim" the front derailleur on the Sora. Maybe you should go to a good LBS and ask them these questions. They can measure the dropouts and tell you for sure. When I put a new cassette on the back, the shop used an 8 speed chain for the 7 speed cassette. They said a 9 speed chain was too thin for the gear teeth. I bet Sora double shifters have trim.Tiples don't. The 9 speed chain stuff is BS.All derailer chains have the same 3/32" inside width.

The only difference between Sora and STI shifters for that 7 speed would be that you can't "trim" the front derailleur on the Sora. The Sora "brifters" will also only jump two gears in the rear instead of three. I keep my bike nice and clean, and the Sora shifters work as well as the Ultegra shifters on my other bike. I put new wheels on my older Trek 420, and they had to put a spacer on the hub for the 7 speed cassette. Maybe you should go to a good LBS and ask them these questions. They can measure the dropouts and tell you for sure. When I put a new cassette on the back, the shop used an 8 speed chain for the 7 speed cassette. They said a 9 speed chain was too thin for the gear teeth. I found the 7 speed Sora shifters on Sheldon Brown's Harris Cyclery web site.
The front shifter does trim on Sora, both ways (up from small, down from big). Double version, I dunno about triple.