Bicycle Mechanics - compatability questions

Hi all, I am a newbie to this forum. So, it has been a real long time since I have ridden my Klein pulse comp. (Shimano Alevio throughout, trigger shifters and 7 speed). So anyway, I brought my old broken chain into a bike store around a year ago and they gave me a shimano hg chain. Well I just got around to replacing it and noticed that my large cog in the front says ig chain only. I need to replace the front and rear cogs / cassettes anyway. Not sure what to call them.
Question 1: Can I upgrade to 8 speed without changing shifters and deraileurs?
2: can I upgrade to hg cogs/cassetes and keep it a 7 speed, since I allready have a hg chain?
3: what is the difference between hg and ig anyway?

So I am finally motivated to ride my bike again and since I have replaced the chain it deels like the chain skips a little. Once in a while. So since I know my cogs are just really old and worn and should be replaced anyway I thought I would ask for some wise advice as to the best way to get it up and running again. I would like to replace as little as possible and I can do the work myself. ( hobby mechanic on my car, industrial designer model maker) So, I am handy and motivated. What do you all recomend.

Thanks in advance, any help is appreciated.

Kyle

7spd-8spd requires:
new shifters
new wheel/hub in back
new cassette
most likely at least a new rear derailleur

Also, the frame spacing is different on a 7spd hub vs an 8spd hub, and since you have an aluminum Klein, its very unlikely it could be spread to accomodate a 8spd hub safely.

Check http://sheldonbrown.com/k7.html

Basically, your bike has a note about "ig chain only" to keep you away of the wider 5-speed chains. I don't even think such chains exist anymore.

HG (Hyperglide) is the next design improvement by Shimano. It is supposed to improve shifting a bit over the IG or Uniglide. Depending on the design of the hub, you probably should be able to replace the cassette by any new 7-speed cassette that has a 12 (or 13 or 14) small cog.

If you really want the extra cog, you could go for a narrow-spaced 8 speed hub towards the end of Sheldon's page). Basically, you need a 9-speed chain (i.e. new one), a 9-speed cassette that you butcher away, and new, 9-speed shifters.

Derailleurs. I know that current (post 1997 or 1998) Shimano derailleurs are all compatible with eachother, and that indexing is solely defined by the levers. IOW, if you move from 7 to 8 to 9 speeds, the only things to change are cassette, chain and shifters; derailleur is OK. Hub is also different between 7 and 8/9.

So the cheapest would be to buy a new 7-speed cassette and keep your bike as is.

Ah yes, the venerable Klein Pulse Comp. Have one myself, except mine came (in 1996) with an 8-spd Shimano/Grip Shift drivetrain. The free space between rear dropouts is about 5.5 inches, roughly 139 mm. I would bet you could upgrade to 8- or 9-spd if you wanted. I have bikes with both 8- and 9-, but I'd bet 7- is fine. I agree with the last post, find a 7-spd cassette on Ebay and you'll be back on the bike quickly. If you do upgrade, though, just remember that 8-spd stuff is getting harder to find (I know this too well) as 9-spd is the new standard.

If you do get a new 7-spd rear cassette, just make sure to get a wide-enough gear ratio to suit your riding. The battle rages on about how many total gears are needed, but I'd argue that having the RIGHT gears are better than MORE. My 8- and 9-spd bikes have basically the same ratios anyway.

If you do upgrade, it gets a bit tricky since 8- and 9 spd have different chain/chainring thicknesses...not sure if 7- and 8 spd are the same.

Thank you all very much for the super quick replies. I do believe that all my questions have been answered. I will go with just replacing my 7 speed stuff. Why rock the boat right? Everything else works and I've never ridden a 8+ speed bike so I don't know to miss anything. My old ratio was 11-30 and worked for me. Is there a ratio that others find better for 7 speed? I can only find that in IG components and I thought that since my chain is HG that I would put all HG cogs on.

Anyway, thanks very much,
Kyle