kwcahart

I've read so much about this I'm totally confused. I have read it is okay, but only if you do this or this. I've read it will work just fine. I've read that it won't work at all. ???? I have RSX shifters and RD, I have a 7 speed hyperglide-C cassette, and the rear dropouts are 130mm which is fine for 8 speed spacing. I guess the big question is whether the RSX shifters (brifters) will index another speed, 8 verses 7. Thanks for any suggestions.

alcjphil

No,your 7 speed shifters cannot index 8 speeds.You can't put an 8 speed cassette on your wheel without changing the cassette body, assuming that it is even possible to do so. The dividing line between 7 and 8 speeds is an expensive one, you need to change more parts. Anytime you change the number of cassette cogs you need new shifters

dabac

If your shifter only has 7 positions, then it will only be able to put the derailer in 7 different positions.
I've read someone claim that a 7-speed shifter would run clean on an 8-speed cassette, but only on 7 of the sprockets. Not much point in that as long as 7-speed cassettes are available.
And, if you have a freehub rear built for 7-speed exclusively, then the freehub body won't take an 8-speed cassette.

Way back when 8-speed was new, there was some talk about using the "ghost shift" to get 8 speeds out of a 7-speed shifter. But I've never tried that and can't advise.

alcjphil

It isn't possible to get 8 speeds out of a 7 speed brifter. However, it is possible to get an extra speed out of a downtube shifter. I did it with my old Raleigh Professional. I had a Campagnolo rear derailleur, a 7 speed freewheel. and a Shimano 6 speed downtube shifter. The lever would click perfectly through the six smallest cogs and I could shift past the last click to the largest cog using the limit screw to make sure I didn't shift the chain into the spokes. Worked perfectly. I raced successfully for several seasons with that setup

le mans

i do wonder why some people want to upgrade in this way

is there something wrong with the current gear ratios?!

seems expensive and a hassle


i might think about it, if i had all the parts from a scrap donor bike

bradtx

In short the freehub, which holds the cassette, is shorter for a dedicated 7S than one for a dedicated 8S, preventing the 8S cassette from being tightened onto a 7S freehub. The 7s STI shifter does not have the ability to shift through more than 7 cogs. A dedicated 8-10S hub can accommodate a 7S cassette, but requires a 4.5 mm spacer between the cassette and inside position of the freehub. If you have an 8S freehub utilizing a spacer, you can mount an 8S cassette.

An 8S indexed shifter can shift a 7S cassette.

Brad

Wilfred Laurier

The 'ghost shift' was only on non-ratcheting shifters like bar-top-mount thumbshifters and downtube shifters. STI and rapidfire shifters never had the ability to use more gears than intended.

kwcahart

Oh well, it was a thought. Thanks. I was going to configure my '95 Cannondale to about the same as my newer Fuji which is a 3 X 8. I'll just change the gear ratios and be happy with it. I'm pretty sure the freehub will take the 8 cogs, but I've read that you would have to use 8 cogs out of a 9 speed cassette. But as you guys have said, the brifters would keep the thing from working, so I think I'll just oil up what I've got and ride it. Thanks.

alcjphil

Yes, you could put 8 cogs from a 9 speed cassette on your hub, but you would need 9 speed shifters to make it work. There isn't a whole lot of difference in the cog spacing between 7 and 8 speed, but there is a much bigger difference in the spacing between 7 and 9 speed.

RoadGuy

You can a 8-speed freehub body to replace the 7-speed freehub body on your rear wheel if you are using a 7-speed cassette and freehub rear wheel. But the wheel will no-longer be centered in the dropouts without redishing the wheel.

As has been mentioned, you will need new shifters, as you can't shift more speeds than the brifters were designed to shift. If you were using friction downtube shifters you might have been able to get away without replacing the shifters. If you want to change to a 8/9/10 speed cassette without the expense of a new set of brifters, you can go to downtube shifters for much less money. New downtube shifters are available for $20-$50 a set from Shimano, and Sunrace (among others).

If you want to get more rear cogs, probably the best time to change is when you replace the rear wheel, since it probably would not cost you any more to get a 8/9/10 speed rear wheel (would probably be easier) than it would to find another 7-speed rear wheel.

As has been mentioned, if you need to replace the rear wheel, and you are not ready to pop for 8-speed brifters, you can use a 8/9/10 freehub rear wheel with a 4.5mm spacer and continue to use your old 7-speed cassette.

It will cost you $150-$200 to get an inexpensive set of new brifters (primarily made of plastic), and you can partially offset the cost by selling off your old 7-speed RSX brifters (which are still in demand).

I converted a Trek 1100 (3 X 7) to (3 X 8) last year for what I consider to be a minimal amount by selectively buying 8 and 9-speed parts from Craigslist and eBay Sellers. The rear wheel was badly out of true, and the shift group was Suntour Edge (while still working, no replacement parts are available). I bought: a set of new Nashbar wheels with tubes $10, front Shimano 105 derailleur $11, front derailleur clamp adapter $7, rear Shimano 105 derailleur $15, Shimano 8-speed cassette (bought 2 to make up 1 with the cogs I wanted) $23, Shimano 8-speed downtube shifter set $20, and KMC X8.93 chain $12.50.

Switching to 9-speeds rear would not cost much more than a switch to 8-speeds, but the maintenance on 9s are higher, since the chains will not last as long.

fietsbob

Invert it .. 8 speed shifters and a 7 speed cassette .. I liked the gear tooth combo of the K cassette nothing much to gain but a 12t 8th IMO.

blamester

Did 7 speed come in 130mm spacing? There would have to be extra spacers added to the axle to make it 130mm or you have a seven speed casette on a 8 speed wheel.
By the way it is possible to get eight cogs on a seven speed hub using a dished inner
cog and seven speed spacers.

bradtx

Yes, also in 135 mm OLD for the Cannondale touring bikes.

Brad

alcjphil

My Gt mountain bike had a 7 speed cassette with 135mm spacing. I later upgraded it to 9 speed.

kwcahart

Yes, the spacing is 130 mm, I measured it with an electronic caliper so the wheel would take an eight or nine speed cassette with no problem. Also there is a spacer on the inside of the cassette so I suspect it has an eight speed cassette on it anyway. This R300 was upgraded from the factory to the same specs as an R500, and I believe the R500 was an eight speed so it probably has an eight speed cassette on it. I think I will see if the right shifter is for seven or eight speeds, it may have the eight speed shifters already on it with the limit screws set to the seven speed cassette. Since this bike was upgraded at the factory to the R500 there are all kinds of possibility's. The R300 was supposed to have downtube shifters and a double crank, but mine has the RSX brifters and a triple, just like the R500. I know the original owner and he said the bike came from the bike shop just like it is now. I need to do some more measuring (cassette length), and to check to see how many indexes the brifters have. Thanks to you guys for the really great information, it has me thinking. ha ha.

alcjphil

If there is a spacer behind your current cassette, it is very possible that your wheel has an 8 speed cassette body. If that is the case, you could upgrade to 8, 9, or even 10 speed quite easily. However it is very unlikely that your current shifters are 8 speed. Although you can make 8 speed shifters work on a 7 speed cassette, they won't work perfectly. There is a .2mm difference in cog spacing between 7 speed and 8 speed. You could adjust cable tension so that the mid range is perfect, but as you shift to either lower or higher cogs the mismatch increases. As well since 8 speed shifters were more expensive than 7 speed shifters, there would be no point using more expensive shifters that wouldn't work as well as cheaper ones

fietsbob

A 7 speed In a 135 wide hub would be dished less than an 8 speed , given the 126 of 6/7 of 136 gives you 9mm of spacer on the left end of the hub .
and hub recenters to the right.
spacer behind the 7 speed cassette on a 8~9 speed driver , you wont get all of that., only 5mm

kwcahart

alcjphil, I was wrong, the R500 also had a seven speed group, with a triple which is what this R300 has. The spacing is 130 mm so it may well have an eight speed cassette. I will try to measure it tonight to see how wide it is. I can't find any charts that show the length of a seven speed vs an eight speed cassette. I have decided to leave it alone anyway, but I would like to know which it is.

dabac

Why not count the sprockets? 7 sprockets and no spacers = dedicated 7-speed set-up and short freehub body. 8 sprockets = 8/9/10-speed compatible and long FH body.
Off the top of my head I think the FH body length for 8/9/10 is about 35 mm while a 7-speed is about 32 mm.

alcjphil

If you have a 7 speed cassette with a spacer behind it, you may have an 8 speed cassette body. According to this:
Sheldon Brown's Bicycle Frame and Cassette Spacing Crib Sheet
an 8,9,10 speed cassette body has to be 3.5mm longer than a 7 speed cassette body. Remove the cassette and measure the thickness of the spacer, if it is between 3 and 4 mm thick your wheel will accept an 8 speed cassette

RoadGuy

What kind of bike are we talking here? And what model year is it?

My 97 Trek 1400 came with a 7-speed rear cassette and RSX 7-speed group. A 130mm rear wheel drops right in. RSX also came in a 8-speed version later down the road. Not being an expert on brifters, I can see any difference in the appearance between the 7-speed and 8-speed versions. Maybe if I had both versions in front of me I could.

If you are comfortable with adjusting the shift cable, you could try detaching the rear derailleur shift cable clamp, and see how many click positions you can shift on the right side brifter. It's possible that the rear brifter is a 8-speed, and the owner locked-out/limited the travel of the rear derailleur by setting the limit screws on the rear derailleur so the 8th position can not be shifted by the brifter. If that is true, disconnecting the cable from the derailleur should allow you to shift to the unaccessable 8th position.

I can't believe that a bike manufacturer would use a 8-speed wheel and spacer on a 7-speed production bike. More than likely, the rear wheel on the bike is a replacement.

I don't see a bike manufacturer using a 8-speed brifters, a 8/9 wheel with a spacer and a 7-speed cassette on a production bike. More likely to do a mid-year upgrade to a full 8-speed drivetrain by simply using a 8-speed cassette

It's more likely that your bike was made as a 7-speed cassette model with 130mm dropouts, and 7-speed brifters. Along the way, the rear wheel got damaged, or one of it's owners wanted a wheel upgrade, and installed the 8/9 rear wheel or a set of wheels, and added the spacer so he'she could retain the 7-speed drive train.

It's also possible that you bike had a 8-speed cassette and brifter drivetrain, and at some point for some reason an owner decided to replace the right side brifter with a 7-speed version. Maybe a "Flipper" got his hands on a bike with a bad right side brifter, the owner wanted the 8-speed brifters for use on a different bike, and he/she swapped the brifters for 7-speed versions.

Or, at sometime, the bike may have been stripped to the frame and rebuilt with whatever parts the owner had laying around in the garage. With a used bike, you never know what happened to it before you got it.

I see Sellers offering bikes that have upgraded and downgraded components and groups on Craigslist and eBay all the time.

Sounds like you may be able to upgrade to a 8-speed cassette by simply buying an 8-speed cassette and installing it (removing the spacer) on the rear wheel. and changing the right side brifter from a 7-speed to a 8-speed version. As I wrote previously you can find a 8-speed RSX brifter on eBay, and sell your 7-speed RSX brifter (and 7-speed cassette) after they are off the bike.

nfmisso

Robot Check plus 8 speed cassette is all you need IF your current set up is 7 speed cassette plus spacer.

And for $15- more you can get 9 speed: https://www.amazon.com/Shimano-Sora-S...4SF764QN2Y0RXB

kwcahart

As I wrote previously, I know the original owner quite well, and he bought the bike brand new and has never changed anything. It has the original Mavic 195 wheels that the Cannondale '95 catalog says it should have. Every measurement I make on the cassette set says 8 speed, spacing, center to center of cogs, etc.

alcjphil

As has been pointed out, the difference in cog spacing between 7 and 8 speed is quite small, only .2mm It would be hard to measure the difference.You can make 8 speed shifters work on a 7 speed cassette, just not perfectly. The fact that your bike has 130 mm dropout spacing is immaterial, what counts is the length of the cassette body. If you have a 7 speed cassette and you are sure that there have been no component upgrades since the bike was new, there would have been no possible reason why the manufacturer would have installed more expensive 8 speed shifters with a 7 speed cassette. They would have installed the correct shifters in order to have the best possible shift performance. As for the cassette body, that is something else again. They could probably buy wheels with 8 speed cassette bodies for the same price as 7 speed wheels, and they might have had less trouble finding 8 speed wheels. Then they could have simply used a spacer behind the 7 speed cassette. This is actually good news if true, it makes upgrading to 8, 9, or 10 speed very easy. In the same way now that 11 speed has become the new standard for the 3 top groups, it will become more and more common for wheels with 11 speed compatible cassette bodies to be standard equipment even on bikes that have fewer cassette cogs.

dabac

So, are you trying to pinpoint the spec of your bike as opposed to finding out your upgrade options now?
Either way, I'm having trouble figuring out what you're going at. There are seven sprockets, right? Do you think you have 7 sprockets of an 8 speed cassette on a 7-speed freehub body? Possible, but wouldn't make any sense from a supplier's perspective.
And while there's a bit of reported cross-compatibility between 7/8-speed I seriously doubt that any bike has ever been sold out of a store with such a mismatch. And if a supplier still had to put an 8-speed shifter on to reach sellable performance, it really doesn't make sense to use a bodged-up cassette/freehub combo.
Measuring center-to-center etc isn't done any old how. You'd need a decent vernier caliper at least.
Someone else already suggested unhooking the derailer, then counting the number of clicks. 6 klicks = 7 speed shifter. 7 klicks = 8-speed shifter.