jonwvara 

Does anyone here know what headset would have come as original equipment on a 1985 Miyata 610? I need to know the stack height for a bike that's not in my possession at the moment. And yes, I know this isn't going to be as reliable as measuring directly, but I'd like to have a general idea of what my options might be.

revcp 

I have '85 610. Coincidentally, I haven't been crazy about the original HS so I ordered last week and should receive in the mail today the Tange-Seiki Levin CDS headset with a stack height of 33.3mm. There are very, very few headsets out there that are such a low stack height.

I should mention too that there is a bar stem reflector/cable hanger as original equipment. I removed that and use a fork mounted cable hanger. I can't remember what mm spacer I put in to compensate, but it can't be more than a few millimeters.

jonwvara 

When you get the old headset out, will you let me know if there are any identifying marks on it so I can figure out what it is? Thanks!

revcp 

Will do, but it may be a while. Exchanging headsets will be a winter project for me. Do you need to know what the headset was (beyond it being a sealed Tange) or are you just interested in he stack height? I can measure the stack height this evening and get back to you.

jonwvara 

I'm interested in knowing the stack height of the original headset--I'm wondering whether a Miche Primato roller-bearing headset will work as a replacement, or whether it will be too high at about 39 mm. There's also a Tange/IRD roller-bearing headset that's a bit lower, at 36 mm or so.

revcp 

I'll measure it for you tonight. I looked at the Miche Primato. It's almost certainly too high. The IRD I looked at as well and decided it would be too close for comfort. For my '90 Team Miyata (a NOS frame that I build up) I bought a Stronglight A9 (also roller bearing). IIRC, that's a 34mm stack height. If you can find one it's a great headset. I went with the Levin CDS for the 610 because the weight of steel vs aluminum (which the Stronglight is) with a touring bike was of no concern to me.

jonwvara 

Yeah, it's nerve-wracking to order a headset when you suspect that it will barely fit if it fits at all. I also suspect that the Primato might be too high. I've heard good things about the out-of-production roller-bearing A9 (to make things confusing there's a current-production A9 that has sealed bearings, not roller bearings), but most of the sources I've consulted say the roller-bearing version has a stack height of 38 mm, not 34.

TimmyT 

The original was probably a Tange Nova. I have one in the bin.

revcp 

Well, color me surprised. Stack height measures out around 40. Pretty sure the original was not a tange Nova. I have that on a '91 Stumpjumper and it's quite different from what's on the 610. Also, I received my Levin CDS in the mail yesterday. Very nice

SSeems you're set on roller bearings. Why?

JohnDThompson 

Roller bearings are better suited to the thrust loads a headset carries than is a ball bearing.

jonwvara 

It's not my bike. It belongs to a friend who likes it a lot but is sometimes troubled by a really alarming shimmy when descending at speed. From what I've read, the causes of this sort of thing are not entirely clear--although they're evidently not caused by a misaligned frame, which had been my first guess. But there also seems to be some evidence that replacing a standard ball-bearing headset with a roller-bearing headset often makes the problem go away, or at least minimizes it. I don't understand why, but for $30 or so for a new headset, it seems worth a try.

I'm assuming that the cups are ISO, possibly with a JIS crown race--I've run into that on other Miyatas. Facing the fork crown to ISO in that case should be easy enough to do.

revcp 

Yep. 26.4, 30.2.