HG70 vs HG90 cassettes

[Tootyred]

Whilst this will be old news to most of you old timers, I've noticed a lot of cassettes on ebay recently being mis sold as HG90 or HG70 when they are not. These cassettes now go for premium ( or silly as i call it) money. I would hate to see a fellow retrobiker end up dissapointed.

The 7 speed era cassettes from around 1990 have different finishes to them, although this can be hard to see in isolation or if dirty.

Whilst i have one of each cleared up, i thought i would post a picture of the difference.

The main thing is the finish coating on the cassette as all the cogs are stamp formed in the same way.

HG90 XT spec, have an chrome mirror finish to them. The cogs are no different and the finish is purely for advanced corrosion resistance..

HG70 Deore spec are still shiner than the lower grade cassettes, but are zinc / nickel plated.

Both weigh in at around 320g

Keep you eyes open. If want a genuine XT HG90 i know bicyclist.cc did have them a while back for reasonable money.

All the best.

 

[JimBob22]

Cheers good info..
Are there no id numbers anywhere on cassette??
Came across this for identifying year of manufacture but don’t know where these numbers are,perhaps someone with more knowledge could help..
Bicyclist are out of stock..

 

[Tootyred]

I dont think cassette had a date stamp.....well not that I've noticed! There are E numbers, but i assume this is for identifying the cogs? All shimano cassettes seem to have these regardless of age. There are also other random nunbers and letters, but they dont seem to be date codes.

In fact the one above is stamped FE, but i doubt its may 81 or 07!

 

[JimBob22]

Cheers
Yeah stared out as a simple I need a 7 speed cassette replacement..bit of a minefield with people claiming it’s a hg70 of 90 and some clearly not..
The xtr stuff is clearly marked..
I’ve decided that year date table is useless..

 

[Tootyred]

It works on most components.....so dont bin it yet!

 

[Tootyred]

Why not put up a "wanted" ad.? Im sure we can find you one between us!

 

[Woz]

AFAIK each cog is stamped with at least one letter to identify which cog "group" it belongs too.
A cog with two letters means the cog is suitable for two cog groups, three letters for three cog groups.

The different cog groups are generally specific to the model and speed. The cog group letters have been re-used overtime, so
it can get confusing if say you have a box of loose cogs and are attempting to rebuild a cassette, or swap a worn sprocket for a newer one.

The cog group letter as nothing to do with the finish, it's purpose is really to help identify the teeth profile positions, so in some cases it is feasible to say use a sprocket from an Ultegra cassette and plonk it in a 105 cassette.

To help get your head around this, it's best to look at the exploded diagrams. There are tonnes of old Shimano techdocs here:
https://www.paul-lange.de/de/service/downloads/explosionszeichnungen.html

 

[JimBob22]

 

[Tootyred]

Is it not also true that the ramping etc is different if the jump is 1, 2 or 3 etc cogs difference......i was told that by a rep years ago, but ive never paid close attention as i rarely swap out cogs in a cassette.?

 

[Woz]

Oh yeah. Just to add. Shimano in their great wisdom generally put the cassette model name only on the lockring, which of course
is arguably the most interchangeable element of the cassette and thus can be mixed up.

The other thing is how the cassettes are marketed in groupsets. HG50 for example spans Deore, Alivio and Tiagra, Sora and Claris over several speeds, and the only difference being a few cog groups to account for the different largest sprocket between MTB and Road.

The second hand cassette market is full of minefields.