IRD Double Roller Drive 1" Threaded Headset

[Mike Ullmer]

My low-trail 650b Fitz has a bad case of the shimmies when I'm using a loaded rando bag and I'm hoping to try out one of these double roller drive headsets from IRD. I currently am using a 1" King Headset.

Anyone know of a source for these? It seems like they're sold out everywhere (hopefully not discontinued!).

Mike in Minneapolis

[eric moss]

Tange-Seiki makes the IRD headsets, and I see 1” threaded on eBay, Rivendell, and Somafab.

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[Michael Wong]

My experience with one of these was interesting. I felt they were almost like how I imagine pneumatic trail is, only without the lag. Or to put another words, they seem to effectively reduce trail. It was hard for me to believe that bearings could do so much, I used to scoff at the idea of roller bearings to help with front end issues, but they really seemed to change the steering.

Personally, I found the sensation distasteful, but for @Mike Ullmer's situation it could be helpful.

I'm curious how much rake you have Mike. Did you try pneumatic trail? How wide are your tires? 

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[satanas]

FWIW, I had a Stronglight Delta headset on The Dreaded GR (v1) and this did nothing to prevent shimmy. A new fork with less offset was the only solution. A needle roller headset may help - or not; YMMV...

Note that needle bearing headsets typically require the steerer tube to be at least 38mm longer than the head tube - more if there will be a centerpull hanger in there, so existing forks may or may not be long enough if there are no extra spacers.

Later,

Stephen (who has Stronglingt needle bearing headsets on other bikes, none of which have shimmied)

[Anthony Pappalardo]

I've found the double needle bearing roller drive to control the shimmy on my Boulder All Road low trail bike. It seems, to me, that the needle bearings lend themselves to running a mite snugger than ball bearings, without brinelling, which in itself goes a long way in calming shimmy.

I've built two low trail bikes since that one and just go right to needle bearing headsets.

TonyP

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Sent: Saturday, March 2, 2024 4:07 PM
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Subject: Re: [650B] IRD Double Roller Drive 1" Threaded Headset

 

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[Stephen Poole]

Needle bearing headsets inherently have a little more drag than do other headsets (when correctly adjusted), however intentionally over-tightening them can result in very disconcerting low speed handling; I don't recommend doing this! (I did it accidentally once, and the change in handling was IME much more drastic than with ball bearings - and not in a good way.)

Later,

Stephen

[David Cummings]

All my road frames are 60 - 62 cm.  Nearly all of them have speed wobble/shimmy regardless of trail.  I have found that a double roller bearing headset can calm it, but not eliminate it.  I now descend with one of my knees touching the top tube as a matter of course (it disrupts the resonance causing the shimmy).

The one frame that doesn't shimmy is my '92 Serotta Colorado TG (pictured below - please ignore the horrible brake lever/bar positioning).  It has the classic tapering OS DT and ST - the diameter gets larger near the bottom bracket.  This bike never wobbles at speed and it has a standard Shimano 600 HS.  It can handle 28-30 mm tires and is an absolute joy to ride.  It doesn't have the capability for fenders or racks, which I normally fit to my bikes, but it flat out flies down the road (in fair weather).  Every time I have tried to sell it, I take it for a spin, return with permagrin, and it immediately gets lovingly placed back in the stable.

Back on topic: If you don't follow Henry Wildberry on youtube, three years ago he did a deep dive into frame design and its contributions to shimmy. Here are videos related to that topic.  (Fair warning - his videos are more conversational rather than slickly edited, so they are longer than some other youtubers' videos - but I still enjoy them.)

A mere mortal obviously doesn't have the resources to do an in-depth, real-world comparative analysis, but the upshot is this: changing the resonant frequencies of the frame affects shimmy.  Henry was able to do it with an OS top tube, Serotta achieved it with OS DT and ST around the BB.  Many others have been able to dampen it with a roller bearing HS. There are likely other ways to do it as well, but so far the only post-build method of addressing shimmy is to change the headset (or to be sure to bring your knees with you).

For Mike: I'm curious. Henry had Fitz build his bikes.  Did the conversation about shimmy ever come up during your Fitz' build process? Or was this built more than three years ago?

I love all of my bikes, my headset and/or knees address shimmy when it happens (I'm very familiar with the conditions in which it occurs more frequently), so I'm not willing to sell them just because they shimmy at high speeds.  I hope you find a good IRD headset, practice using your knee on a top tube when descending, and continue to enjoy your custom Fitz.

David "Shakin', Shakin' Shakes" in MT 

[njh...@gmail.com]

I think shimmy is as much due to the rider as the frame. I also ride 60-62cm frames - I have never experienced shimmy on any of them, and I must have owned and ridden several dozen different frames over the past half century - old skinny steel, modern slightly larger diameter steel, several Ti, aluminium, and carbon-fibre. And everything from out-and-out lightweight racing frames to heavy-duty touring frames.

Nick

[Stephen Poole]

Sorry, but I disagree; I've had three frames that shimmied persistently:

One was a touring bike (~57cm, 531 ST) which had low mounted bags front and rear. Doing away with the low rear rack and fitting a normal Blackburn fixed that one.

The next was a very short wheelbase (John Olsen trials style) MTB which had a very rigid 531-tubed above-the-tyre front rack attached to the frame, not the fork. If there was anything on the rack the bike shimmied on descents. (AMs used to be available with a special front rack and Zzipper fairing ex-factory, but carrying any load on the frame-attached front rack was not recommended due to the likelihood of shimmy, so I'm  not the only one with reservations about frame-mounted front racks. However, AMs had both low trail and small, light wheels.)

The other was The Dreaded GR, which *always* shimmied above ~28km/h. Usually this was just (very!) annoying, but on one occasion in Wales I was descending at a fairly high speed in the rain/mist with heavy passing traffic and had a "tank slapper" type event - very scary.

None of the other bikes I've owned or test ridden have ever shimmied at all, so I don't  think I can be blamed in this case...

Later 

Stephen

[njh...@gmail.com]

At the other end of the scale, I've known a rider who fairly often suffered shimmy on just about every bike they rode. They got very practised at clamping their knees to the top tube to damp it out. And yet I rode a couple of those bikes, and they didn't shimmy for me. So most of the problem must have been the interaction of the frame and rider, and not just the frame, producing shimmy.

Nick

[David Cummings]

Load may well be another factor - whether it is the load of the rider or the load on a front rack.  Some factors seem to simply be anecdotal, while others are more be predictable. It’s hard to argue with the unnerving, real world experience we have each had. It’s good that we have found some ways to address it and can share them. It’s a very YMMV situation. 

David “Shake it up baby” in MT

[jeffwc...@gmail.com]

This is a very timely discussion for me - I just finished building up a Crust Canti Bolt, and took it for a short shake down ride in Brooklyn.  There isn't a lot of descending to speak of in Brooklyn, but I decided to try an aero tuck on a short downhill, and immediately experienced shimmy, which stopped when I switched to the drops.  I'm running a Chris King headset.  

I will experiment with either the knee to the top tube, or unweighting the saddle.  Weight on the saddle acts as an anchor point on the bicycle that contributes to the shimmy.  If either of these don't work, I will look into a roller bearing headset.

As explained in this really good Marginal Gains podcast episode, shimmy on a bicycle is a phenomenon known as "Hopf Bifurcation".
https://silca.cc/blogs/marginalgains/bifurcation-and-marginal-gains?_pos=1&_psq=bifurcation&_ss=e&_v=1.0

You might have already read these articles on shimmy, but if not they are good resources.
https://www.sheldonbrown.com/shimmy.html
https://www.sheldonbrown.com/brandt/shimmy.html

Best,

Jeff C

[Michael Wong]

I'll just reiterate: My IRD double needle bearing turned my quick steering, low trail Elephant into a slower steering, effectively higher trail bike.

So that could solve your shimmy problem but you have to decide if you want that possible side effect.