LeSexyFishorse

Hi guys,

I got a new wheelset the other day that has an 8 speed hyperglide rear. I was previously using a 7 speed uniglide with 7402 RD and ST 7400 with the last click limited by limit screws. After installing the 8 speed wheel I was in the process of tuning the indexing following park tools video when I heard a snap downshifting one gear. After that, the right STI upshifts to easier gears perfectly however one click on the downshift drops the gear all the way to the smallest cog. I cannot seem to go down 1 gear at a time it is just straight to the smallest cog on one click no matter what gear I am on. Anyone have this issue before? Fixable?
RJ the bike guys video makes it seem to me like I might have broken one of the catches on 1:56?
If it cannot be repaired I was thinking of going to downtube shifters while I look for another STI. Unfortunately the only thing I have usable right now is an 8 speed suntour superbe pro. I used this with the 7 speed setup before I found the 8 speed STI and it indexed fine. Will it work with 8 speed?

Any insight appreciated.

-Fish

Hondo6

Dunno if that one will work with DuraAce 8 speed or not. But if it doesn't - and if you don't mind using a clamp-on set temporarily - Sunrace makes Shimano-compatible clamp-on downtube shifters in both 7- and 8-speed that are quite reasonable. They can be had on eBay or Amazon for <$20, shipped. They should may (or may not, unfortunately) work with DA 7400 using alternate cable routing C.

For some reason, the braze-on version of the same Sunrace shifter set is considerably more expensive. Plus, the Shimano equivalent braze-on 8-speed set seems to be around $40; ditto Microshift's 8-speed downtube set.

Pretty sure the Shimano and Sunrace 8-speed downtube shifter sets are index only for the rear shifter. I think the Microshift unit has a friction mode for its rear shifter.

Best of luck finding a replacement brifter, or getting yours repaired.

bulgie 

Recycled Cycles in Seattle always has boxes of used brifters. I'd be shocked if they don't have what you need. Maybe give 'em a call?

No connection, just a frequent customer.

daverup 

LeSexyFishorse Any of the older STI shifters can be suspected of being gummed up with sticky old grease. This usually results in sticking pawls. Thoroughly flushing the shifter out with WD40 works for most of these. If you really broke something, this won't help. It's worth a try.

Fivethumbs

It sounds like one of the internal tension springs broke. There is a guy on ebay with the handle "Zigan" who rebuilds 8 speed STIs for around $40 per shifter. You can do a search on ebay for "Shimano lever repair" and it will come up. I'd email him.

RiddleOfSteel

Agreed. It's one thing to have these gum up over time (I use TriFlow as it is a lubricant and de-gummer in one), but another to hear a snap and know that it's not normal. 7400 Dura-Ace has its own pull ratio, so as for compatible downtube shifters, it's either a 7400 unit matched to however many cogs you have out back, or whatever lever it is, just in friction mode (for now).

LeSexyFishorse

daverup RiddleOfSteel Tried the flush method to no avail. I did hear a snap before it went wonky so I think I broke something. I should add that prior to breaking it downshifts would sometimes stall for a bit before shifting (cables & housing was new). Since I was running 7 speed at the time I thought it may have been related to that.

Fivethumbs Is this the guy you are referring to? Shimano 105, RX-100, RSX, 600 7 or 8 speed STI lever rebuild service/repair | eBay

I took a cue from your suggestions and looked around for a local guy who might be able to service it. Turns out my LBS mechanic who used to race in the 80s knows a guy who might be able to repair it. Before that, has anyone tried repairing one of these before? Is it difficult to do or does it require any special tools? If i broke a spring would the part be generic enough to still be sourced? I suppose I wont know unless I know whats broken. I suppose if I cannot get it fixed locally I would probably look to either send it to Zigan or source another one whichever is cheaper considering I am in Asia.

Side note - was it something that I did? Did these shifters have to be babied in certain ways so as to not break them? They look almost NOS condition when I bought them I am surprised to have issues so soon.

Thanks

Fish

Fivethumbs

Several years ago I rebuilt a few 6400 and 1055 STI shifters so it is doable. The first hurdle is that there is a crown nut that needs a special spanner socket to remove. I made my own with a dremel tool. My first attempt was a failure because there were so many small parts and they got mixed together. So the parts went into a baggy. I then tried again with another shifter and took photos of each step and laid everything out in sequence. It was very time consuming but I was able to disassemble, clean, and reassemble the shifters. It's possible you could take it apart just enough to identify and replace the broken spring. I remember taking the shifters completely apart down to the last little clip or spring. However, in doing so I realized you don't usually have to completely disassemble them to replace some parts or gain sufficient access to clean the parts. I don't think I would not want to do it again. If it were me, I would probably contact the ebay guy to see if he could replace the broken part. In my conversations with him, he indicated he had a lot of spare parts. Or just search ebay for a good condition used replacement.

dddd

The one thing that will break STI internals is to force the big lever in if/when the small lever has been pushed inward even slightly.

Movement of the small lever is supposed to "latch" or lock, i.e. prevent the big lever from being pushed in at the same time.
But if a strong or "agitated" rider stabs for a downshift to a larger cog while accidentally bumping the little lever inward even slightly, the latch nub at the upper end of the small lever will be sheared off. The 9s levers were perhaps the most vulnerable in this regard but weren't the only ones.
My Davidson's small lever return spring failed and I keep a tiny rubber band around the big and small lever to effectively return the small lever to it's home position. Surprisingly this works well enough, but I would like to fix it someday since the small lever is relatively easy to access once the lever has been removed from the steel bracket that it is nutted to.

KCT1986

The 8 & 9 speed DA brifters are different from most Shimano brifters of that era. The video that you attached is representative of most of Shimano early brifters.

Do a "google" search for the below term for pics of what the DA looks like. For some reason "Bing" didn't get me the same search results. Review the search result from 'Norvil.net'.

From what I have seen the 7400 is similar to the 7700.

Stripping Dura-Ace 9-Speed STI Levers

LeSexyFishorse

So the sti would be closer to 7700 in mechanism then? Based on Norvil disassembly guide I will need a Shimano service tool TL-ST01 and possibly a thin 9mm flat spanner depending on how deep the teardown will have to go to fix the problem. I suppose at this point it would be more convenient to send it to the local guy. I will email ebay guy as well and ask him of his idea on what the problem might be. I am guessing since the lower lever is for the downshifts, if a spring broke it will be this one?

I guess I will either get a 9 sp sti or use my DT shifters in friction mode for the time being. Such a shame since the upshifts are so smooth with this 8 speed.

LeSexyFishorse

Did the return spring failure give you similar symptoms to mine? What about the shearing of the latch?

Kontact

If you want downtube or STI replacements, any Shimano compatible 9 speed shifter will shift a 7400 derailleur perfectly across 8 speed cassettes.

wrk101

eBay has several sellers who rebuild the 8 speed STI stuff. Read their feedback and choose the one you like. I've had many rebuilt. I'm not a WD40 flush fan, first it removes all the lubrication in the shifter and secondly, it does nothing for broken parts. A good rebuilder will have a stash of parts.