front end shimmy due to loaded rear rack?

[Christopher Young]

Hi All,

I have a 61.5 cm AHH with a rear rack installed by Riv when I bought the bike. The rack looks great, but I've noticed that when I have it loaded, I often get a front-end shimmy when I am riding fast and take my hands of the grips, and people riding behind me have confirmed the rack is moving a lot. It sounds exactly like what Paul M described in a 2024 post about his 64 cm Clem:

"I also experienced a front-end shimmy if I took both hands off the handlebars with a loaded rear rack trunk mounted on the top of the rack". Exactly!!

Because of the size of the frame and the way it's installed (see picture), my theory is that those vertical supports are very long and hence not so rigid and I'm getting some sort of harmonic motion (like a mini-version of the Tacoma Narrows bridge). Anyway, I've tried some minor adjustments to try to make the rack supports shorter and hence more rigid, but with only minor (if any success). At this point, I'm thinking of a couple of options:

1. more radically changing the attachment points for the rack to get those longer supports a lot shorter. This could get tricky though, working around the rear brake.

2. Removing the basket (it can go on my newly acquired 64 cm Clem L) and changing to a rear bag (e.g. Sackville Bagboy) that hangs from the saddle and hence doesn't really rest all its weight on the rack. I can still strap lighter stuff on the rack.

I'm strongly leaning toward option #2 because I like the look of the rack as is and I think the behind the seat bag might look very nice. I guess another option is to install a different rear rack with more rigid supports, but again, I like the look of this rack and this isn't my bike for hauling heaving loads (that's be the Clem).

Have others experienced this sort of problem and if so, how did you fix it?

thanks

Chris Young

ABQ

[tom butcherboy]

Beware of free advice..but.  I think your rack might benefit from some 'fore/aft' connection. it seems mostly side to side. And as the load get taller, center of gravity rises.  Your seat stay eyelets are both raising their hands looking for work. I had a similar issue when downhill braking and rebalancing some sort of front-end load was helpful.  Tom.

[Eric Daume]

Riv did a poor job of installing that rack. The forward struts should go to the forward/upper attachment points on the seatstays. That will increase the triangulation and stability.

Eric

--
You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group.
To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bun...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/b0c1484f-a662-4193-8f21-d74e892a3a71n%40googlegroups.com.

[Brian Turner]

I have to agree with Eric - that’s an awfully wonky mounted rack, and I would not feel comfortable riding with it like that. It surprises me they would do it that way, especially when they’ve always seemed overly cautious with the way racks are mounted.

Brian
Lexington KY

[Christopher Young]

Thanks Eric! I think your assessment is right. Looking at this rack installation vs. others, what really stands out are those very long vertical struts, which don't form anything like a triangle (though there is a diving board attachment, so 5 total contacts with the frame). Anyway, I like your solution, but there is an issue that might not be apparent from the photo. There are indeed attachment points higher up on the seatstays, but they blocked by the brake, which sticks out a bit on either side. It's going to take some pretty creative bending (a bend one way and then another back) to get those struts to attach to those upper points. I'm thinking it can be done, but was wondering if anyone else had already dealt with this on an AHH so I don't end up demonstrating how poorly I can bend struts. Ironically, I installed a rack (I think the same model) on my wife's 60 cm Platy and because it has V brakes that aren't in the way I was able to have the upper/forward struts go almost horizontally from the front of the rack to the seatstays, so no bending. It doesn't look as elegant as this installation, but it definitely has that triangular strut setup and she doesn't have any vibration from the rack.

Something I tried but that didn't fix it was to lower the rack a bit (no fender, so plenty of clearance) and I brought it forward, sliding more of the diving board under the rack. I hoped that might make that connections shorter/stronger and stiffen things, but if it did, it wasn't enough. 

I will not be too upset if going for a Sackville Bagboy is a good solution (just looking for an excuse to buy one of those). For this bike, I think that would look really nice and then the rack is just a backup to keep the bag of the wheel. 

Chris

[Christopher Young]

BTW, to be fair to the Riv guys, as part of my attempt to fix this problem, I also moved the back strut attachment points up a little from the attachment points right at the dropout to the next ones, a few inches higher. I was thinking that would make them a little shorter/stiffer and make the angle a little different, but it didn't help.

Chris

[Mike Rossi]

Ahh, I see the diving board, but vertical attachments to those seat stay bosses will help. Harbor Freight sells a tubing bender (Pittsburgh 1/4”-3/8” tubing bender) for $10. One of my favorite “bike tools”. Get perfectly matched bent struts and stop looking for odds and ends around the house to bend the struts around!

Mike

On Nov 27, 2025, at 4:41 PM, Christopher Young <nmtr...@gmail.com> wrote:

BTW, to be fair to the Riv guys, as part of my attempt to fix this problem, I also moved the back strut attachment points up a little from the attachment points right at the dropout to the next ones, a few inches higher. I was thinking that would make them a little shorter/stiffer and make the angle a little different, but it didn't help.

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/e07cb869-3f31-4799-ab40-258612b0a2ean%40googlegroups.com.

[Christopher Young]

Oooh! I'm getting one of those tools! I guess regardless of whether I got the Bagboy route it would still be nice to get that rack more solid. What's the limit on how much you can bend a strut? E.g., would 90 degrees be too much? It's going to take some significant bends to get around the brake, at least on the left side.

Chris

You received this message because you are subscribed to a topic in the Google Groups "RBW Owners Bunch" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/rbw-owners-bunch/G8tosK9y08k/unsubscribe.
To unsubscribe from this group and all its topics, send an email to rbw-owners-bun...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/E9C30FCE-8CAC-4324-9D5F-E49284BC7CDC%40gmail.com.

[Mike Rossi]

What's the limit on how much you can bend a strut?

I’m not sure. I used this scrap, but it was already a little wonky.

[Guy Jett]

So many questions:

* Would be nice to see the original Riv installation. 

* Did that installation include the basket or did you add the basket?

*  Was the rack initially that high above the rear tire?

Additional Observation:

* There is basically no triangulation in this setup, especially with the near vertical angle of the diving board.   As a result fore and act movement may be a contributing factor to the lateral motion and shimmy. 

Suggestions:

* Get rid of the basket. That only contributes extra weight very high up that exaggerates the shimmy. 

* Reduce the height of the rack to 1 cm or less above the tire. Will shorten the rear stays a bit. 

* Connect the forward stays directly to the fittings above the brake.  They will be much shorter and provide better triangulation to the rack system. 

* Get rid of the bend in the left rear stay. Alternatively consider bending both rear stays inward as this may counteract the lateral motion. 

Hope you find a solution, 

GAJett

--

You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group.
To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bun...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/15fae32a-4bd1-464d-b5a9-13b304bd8de9n%40googlegroups.com.

Guy

[Christopher Young]

Guy,

Great questions. 

• Attached is a picture showing the original installation, as done by Riv. As you can see the back strut connects to a point near the dropout, so those struts were even longer. And the rack was even higher above the rear tire. I've got it a bit down and can go a little further. Maybe they put it high thinking I might add a fender?
• I did add the basket and agree that's contributing to the problem. i'm planning to move it to the Clem, but note that it's the wald "racing" basket, so pretty minimal. Note also that in this earlier picture, the basket isn't there, but I'm pretty darn sure the shimmy had already shown up.
• I'm definitely going to try to figure a way to connect those forward struts to the the higher connection points, by the brake. That's going to be challenging.
• If i do that, and I've still got issues, I may also move the back struts up to the connection point where the forward ones currently are. That would seem to be more in line with other installations I've seen in photos on the Riv site and elsewhere.
• bottom line: I think this weird installation has everything to do with the brake blocking easy access to the higher attachment points. You'd use those if you could get to them. I'm a little surprised the Riv guys didn't tell me this might be a problem and suggest a different rack setup, but maybe they thought I wouldn't put much weight on the rack (not that I've been really loading it up). Anyway, I definitely don't blame them. I'm the one that picked that rack and said to put it on the back. I could have asked them what they'd recommend for that bike.

I appreciate all the suggestions! The basket is going for sure, and I'm very likely going to get a Bagboy, but I still want to try to fix this issue. It just shouldn't be like this.

Chris

You received this message because you are subscribed to a topic in the Google Groups "RBW Owners Bunch" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/rbw-owners-bunch/G8tosK9y08k/unsubscribe.
To unsubscribe from this group and all its topics, send an email to rbw-owners-bun...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/CAMHQv6XuTqMO%2BrWJshbJrWuwx96zSZk%3DQP8fAobxrZOou%2Boh6Q%40mail.gmail.com.

[TOM CUNNINGHAM]

If the side pull is in the way...that's only on the cable side. The other side is open to experiment with a single strut (HD if available) to see if that seems to make a difference.

https://groups.google.com/d/msgid/rbw-owners-bunch/CAC_3U-3xe9wvm-ty827XMGgRH1FccqM9tN4LiZwKNtcH9MAVGA%40mail.gmail.com

.

[Tyler Johnson]

Hi, Chris.

I agree with Tom – experiment with those upper bosses even though one of the two bosses is currently blocked by the sidepull of the brake caliper. Before you bend the aluminum strut, determine if a triangle will stop the side-side shimmy. 

On the unblocked side, mount the strut normally to the outboard of the boss. On the blocked side, mount one of the struts from the inside of the boss. If it's still a bit blocked by the sidepull, you can use old V-brake cone & cup parts to shim it clear of the brake. (I can't recall how blocked the boss was when I saw it last month.) 

If that solves the wobble, then bend the strut. You probably only get one chance to bend the aluminum strut before it weakens when you bend it twice.

Another possibility is to temporarily switch out the rear brake so you can do your experiment with normal, straight struts with no shims. Next time we meet, I can lend you an old centerpull brake with enough clearance for your chunky tire that will free up lots of space for the struts. If that experiment works, then you have an excuse to buy a Paul Racer for the rear. 😀

Tyler

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/722853842.1544627.1764309835320%40mail.yahoo.com.

[Paul M]

The issues with how the front struts attach to the rear eyelets definitely needs to be addressed. But even then, there is a good possibility that the front end of the bicycle will experience a shimmy while riding with your hands off the handlebar. I've experienced this with proper rear racks attached (Nitto, Salsa Wanderlust HD steel, Jannd) with moderate loads (rack trunk or panniers) and still experience the front-end shimmy when removing my hands from the handlebars. This happens when peddling <10 mph. I sense that it has to do with the long wheelbase/longer rear-end that certain Rivendells have and probably affects the taller/larger frames more. It's happened on a 64cm Clem L, Platypus 60cm but even a double top tube Rosco Bubbe 56cm. Not to confuse this with a speed wobble that happens at much higher speeds even when your hands are on the handlebars. All the bikes mentioned are rock solid when descending at high speeds. 

[Eric Daume]

Random thought: can you flip the rear brake caliper and mount it on the underside of the seat stays? Like a Havnoonian. 

To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscribe@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/15fae32a-4bd1-464d-b5a9-13b304bd8de9n%40googlegroups.com.

Guy

--
You received this message because you are subscribed to a topic in the Google Groups "RBW Owners Bunch" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/rbw-owners-bunch/G8tosK9y08k/unsubscribe.

To unsubscribe from this group and all its topics, send an email to rbw-owners-bunch+unsubscribe@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/CAMHQv6XuTqMO%2BrWJshbJrWuwx96zSZk%3DQP8fAobxrZOou%2Boh6Q%40mail.gmail.com.

--

You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group.

To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscribe@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/CAC_3U-3xe9wvm-ty827XMGgRH1FccqM9tN4LiZwKNtcH9MAVGA%40mail.gmail.com.

[J J]

Christopher, just to build on Paul M’s point. Have you tried riding the Homer without the rack? I had the same shimmy issue on a Hunqapillar. Grant and Mark at Riv first had me remove the Nitto 33R (Big Back Rack). The shimmy remained. Next, Grant suggested tightening the headset to add friction. That helped, but only once I tightened it more than felt reasonable, which hinted at a headset/steerer issue.

The final fix was swapping the stock FSA (ball bearings) for an IRD DoubleRoller Drive headset with roller/needle bearings top and bottom. That eliminated the shimmy entirely, with or without the rack, loaded or not. Grant said shimmy can be mysterious and varies by frame, so starting with a rack-free test is worthwhile. Grant also said, “Keep your hands on the bar — don’t ride no-hands!”

Jim

[Patrick Moore]

+1 for seeing if the shimmy remains without (1) the basket and (2) the rack.

I’ve had shimmy come and go on at least 2 bikes from things as minor as changing tires. My 2003 Riv road custom shimmied with 240 gram 1.25”  Paselas but not with 400 gram 1.35” Kojaks (and this had stout tubing; 58 cm c-c size), and the current Matthews (much lighter tubing) replacement shimmies with 41 mm 300 gram Naches Passes but didn’t with 29 mm 175 gram Elk Passes. Slow or cruising speed shimmy in both cases, and only when riding no-hands.

I seem to recall another instance of shimmy that disappeared when I replaced or removed a rack, but I can’t remember it clearly.

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/eaf1515a-8d13-431c-94f0-b2acfb63f195n%40googlegroups.com.

--

Patrick Moore

Alburquerque, Nuevo Mexico, Etats Unis d'Amerique, Orbis Terrarum

-------------------------------------------------------------------------------------------------------

Executive resumes, LinkedIn profiles, bios, letters, and other writing services

-------------------------------------------------------------------------------------------------------

When thou didst not, savage, know thine own meaning,

But wouldst gabble like a thing most brutish,

I endowed thy purposes with words that made them known.

[Danny]

FWIW, I have a 61.5 Homer without racks, and I get shimmy with both hands off the bars. I was planning to experiment with a roller bearing headset and tire swap this spring, so thanks for sharing your experiences Jim and Patrick.

Danny

Madison, WI

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/CALuTfgv1c7mTuv6P11U-fwAQk5w7FJgXzZsF6yN6zeO8ppubRQ%40mail.gmail.com.

[Gregory Johnson]

Chris,

Another option is to try a different rack.

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/e07cb869-3f31-4799-ab40-258612b0a2ean%40googlegroups.com.

[Pam Bikes]

I've never had a shimmy and ride w/lots of weight on my rack but I ride a 50 and I have bags so I try to get ,my loaded weight down as low as possible to lower my center of gravity.  The basket keeps it up high in addition to you already having a high center of gravity on a 60.  Maybe I've never noticed a shimmy b/c I rarely ride no hands and certainly not w/heavy loads.  I used to have a front basket on the front on a bike and it never handled well this the rack and panniers set up I have now.  Or w/heavier loads I use a Burley Travoy getting the weight even lower and only trailing.

[Christopher Young]

So I have apparently solved this problem, though I think it's more like I finessed it rather than actually got to the bottom of it.

I removed the basket from the back rack on the AHH and went ahead and bought a Sackville Bagboy, which hangs from the back of the seat, and actually has more volume than the bag I had in the basket. Hence the rack is now a safety measure to ensure the Bagboy never hits the rear tire (I don't have fenders). I did a 45 mile ride yesterday with plenty of stuff in the bag and had no shimmy, even going fast down hills! I'm thinking I could strap something light like a jacket on the rack and it would still be OK, but we'll see.

Meanwhile, I have moved the basket to the rear rack of my new (to me) 64 cm Clem and today I rode that with the same bag in the basket that I had been using on the AHH when I had the shimmy and......no shimmy! So I've got 2 big bikes that can carry stuff on the back with no shimmy. I still want to work on redoing the forward struts on the rack on the AHH, but in the meantime, I'm riding smoothly and happily on both bikes. I guess not everyone approves, but I like to ride without hands on the bars when I'm on a smooth, safe road or path (it gives my hands and arms a break), and the shimmy was really spoiling that.

Somewhere in this chain someone said that rack shimmies are mysterious, and I strongly agree with that. Some bikes seem to have them and others don't, even with (seemingly) similar setups. But it does seem like bigger bikes are more likely to have the issue. I'm just glad to not be dealing with this anymore. Fingers crossed!

Thanks for all the discussion and suggestions.

Chris Y.

ABQ

[Laing Conley]

I don’t think that I saw anyone suggest this, but it is many times possible to attach the rear upper rack struts to the inside of the fittings on the frame. I seem to have dozens of Allen wrenches (many parts come with a cheap Allen wrench) so I shortened one in order to mount a rack strut to the inside of the frame - the first one is easier than the second one if you want to do only one side. This enables the strut to clear the brake cable. 

Laing Conley 

Delray Beach FL

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/767cbfe7-4d2e-49b7-acdc-a124e82f76b2n%40googlegroups.com.

[Christopher Young]

Thanks Laing. I think that's what I'm going to try if/when I get around to remounting that rack.

Chris

[JohnS]

2nd Laing's suggestion to cutting an Allen wrench down so that it fits into a tight space. I've done that to a 3.5mm Allen to loosen the upper pulley on a rear derailleur, like an older Deore XT. I keep it in the tool box just for that purpose.

JohnS

[Patrick Moore]

Just a thought, but with a large Homer frame and a sub 2” tire, you might want to see if your large Homer has enough clearance between underside of saddle and top of rear tire to accommodate a Bagboy without a support. Me, I like transverse saddlebags precisely when they don’t need supports; if I use a rack, it’s to accommodate panniers which have much more volume and on/off flexibility.

Perhaps some added stiffening — I’ve got some spare Coroplast — would keep the load off the tire.

Here’s a 30 lb load in a Medium Sackville circa 2010 with plenty of clearance over rear tire and no support or even a cinch strap around the bag. And, the bag was mounted on a home-made QR bag mount that put the bag an inch or so lower down compared to strapping it directly to the saddle.Granted, 26 X 1.4” wheel (~25” tall) on a 58 cm c-c frame (that 2003 RBW Curt), but I think that modern Sackvilles have been improved for even better tire clearance, and your Homer is considerably bigger than the Curt.

[Peter White]

Back in the pre-cambrian epoch, I did an experiment. I took a pack of SRAM chains, ten to a pack, and put it inside the rack-top pack on my touring bike. I placed it at the rear of the pack, and put a down vest at the front of the pack. The bike shimmied horribly. The bike was unrideable. About 50 yards down the road, I stopped and moved the chains to the front of the bag, and the down vest at the rear. There was no shimmy. It's all about weight distribution.

--

You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group.
To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bun...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/CALuTfguVRBziz5M6n0EtxYShx%2B-C9y252teiOfJyLigW_J5mYw%40mail.gmail.com.

--

Peter White

[Bill Lindsay]

That's a solid experiment, Peter, and your observation is consistent with the math of mechanical resonance.  If a bike shimmies and one wants to make it stop, add some weight, remove some weight, or move some weight around and try again.  That's not the only possible remedy, but it's the simplest recommendation and ought to be effective the vast majority of the time.  

Bill Lindsay

El Cerrito, CA

[Christopher Young]

This is all consistent with what I'm seeing (which is maddeningly variable). Saturday I had the AHH working with no shimmy by switching to using the Bagboy hanging from the seat instead of strapped to the rack. Monday I had the Clem working with no shimmy with a load on the rear rack very similar to loads that have caused problems on the AHH. Yesterday I rode the Clem with what I thought was a nearly identical load (same bag in back basket, same contents, even riding the same route), but somehow the shimmy showed up! It seems that small differences in amount and distribution of load can make all the difference. Peter's example shows that perfectly.

I'm thinking that bigger frames are more prone to this, but that's just a guess as I don't have shorter bikes to test the theory. Have people with smaller frames also had these problems?

Chris

You received this message because you are subscribed to a topic in the Google Groups "RBW Owners Bunch" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/rbw-owners-bunch/G8tosK9y08k/unsubscribe.
To unsubscribe from this group and all its topics, send an email to rbw-owners-bun...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/ddb83cd5-9437-44f5-8d4e-20ebd05ebbe5n%40googlegroups.com.

[Guy Jett]

I have a 54cm Homer.  Large handlebar bag on the front.  Rack on back usually carries only lightweight stuff on top or panniers for heavy stuff.  At higher speeds (e.g., over 25 mph coasting downhill) if I move my own weight to the back of my saddle and tuck into a more aero position I do get a shimmy.  If I am in a more normal and upright position -- no shimmy.  Seems to correlate Peter White's experiment.  

GAJett

To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/CAC_3U-1MGj5NiV9EoRZ48QEVr4_Qty7_8qSyWEM%3DBUOaVkqmYQ%40mail.gmail.com.