How to fit a rear rack on a full suspension bike?

BillH: Old Man Mountain was bought out by The Robert Axle Project. Not sure of your rear axle diameter, but I see they list a 12mm rear axle in various lengths; from 172mm long, 167mm and 160mm. These axles are made to fit their racks. Link: https://oldmanmountain.com/product/12-mm-rear-thru-axle-1-0-mm-thread-pitch-and-167-160-or-154-mm-length/


Smorgasboard: I too would question attaching that seat post mounted rack on a dropper post. For one thing, you need to reef down on the attaching bolts pretty good to prevent the rack from fish tailing on you.

Before I settled on the front and rear Old Man Mountain Racks, I went for a good long time running a front OMM rack to fit my side panniers and a rear seat post rack and bag.

I settled on the Portland Design Works Bindle Rack with the Revelate Designs Terrapin dry bag, which is designed to fit and work with the PDW rack. It worked just fine, then again, I don't have a dropper seat post as you do. But the main thing is, you are really constrained on what you can bring along. On a warm day going long distance, I like to carry extra water, my ultralite seat to rest up in as well as the standard air pump, tire patching kit and spare fat bike tire tube. And that back is pushing the limits on the amount of stuff you can carry. For your purposes, it sounds like it would work.

But beware: Reaching full tire shock compression, my back tire would hit the bag where it fits on the seat post in the below picture. Your ideas of putting your rack even lower then what I have will definitely result in the rear tire hitting your rack.
 

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BillH

Member
Seems like it'd be really hard to swing a leg over the Arkel loaded up that way.
In that stock photo it's angled pretty high. Depends on back seat stay angle. Mine is not nearly as vertical as the one in the photo. My bag actually sits only an inch above the top of the seat, and I have a small frame which is an easy enough 28" step over height. That picture is also of the 15L bag, I got the 9L.
 

BillH

Member
BillH: Old Man Mountain was bought out by The Robert Axle Project. Not sure of your rear axle diameter, but I see they list a 12mm rear axle in various lengths; from 172mm long, 167mm and 160mm. These axles are made to fit their racks. Link: https://oldmanmountain.com/product/12-mm-rear-thru-axle-1-0-mm-thread-pitch-and-167-160-or-154-mm-length/


Smorgasboard: I too would question attaching that seat post mounted rack on a dropper post. For one thing, you need to reef down on the attaching bolts pretty good to prevent the rack from fish tailing on you.
I was aware of the buy out. My bike has a 12mm x 200mm axle. During our back-and-forth conversation they admitted to being a niche product and simply could not accommodate every configuration out there, mine being one of them sadly.

The Arkel has a bracket attached to seat stays and braced to seat post. There is no side sway at all with this bag and it is designed to work with dropper posts, albeit with 1" of dropper length lost.

Edit: Meant to comment on aspect of bag size. You're right Mike I'm limited with 9L, pretty much essentials and a few extras. I use the Arkel trunk bag on another bike, it works for what I need but yeah, tight fit at times. The Seatpacker has similar volume.

I have 5" of rear travel on my bike and bottom of bag to top of tire is also right at 5". The dropper deployed = tire rub for sure.

BTW....love the FullFat6
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smorgasbord

Active Member
But beware: Reaching full tire shock compression, my back tire would hit the bag where it fits on the seat post in the below picture. Your ideas of putting your rack even lower then what I have will definitely result in the rear tire hitting your rack.
Yeah, I questioned that as well. There are, however, racks that are elevated above the seat post mounting point. For instance:

ra308a02.jpg



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So I think the stress on the dropper post itself is my biggest concern.
 

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I agree with going with the Old Man Mountain if you can. I'll explain.

I placed an order for one for my BH Atom X Lynx 5. They got back to me for verification of thru axle bolt length and thread pitch. I was ok for the axle length, but BH, at least my bike, uses a 1.0 thread pitch and the more common pitch is 1.75 for split axles. So, for me it was a no go. I was bummed.

Ended up with an Arkel Seatpacker 9. In retrospect it turned out to be the better choice for my trunk bag sized needs.
I got the same response when I inquired about my BH Rebel Lynx, the thread pitch is uncommon.

Any other ideas for getting a rear rack on my bike?
 

BillH

Member
I got the same response when I inquired about my BH Rebel Lynx, the thread pitch is uncommon.

Any other ideas for getting a rear rack on my bike?
The only other option for a rear rack, other than seat post ones, is the Thule that I could find. It's why I went the way I did.

Maybe now that they have had some additional inquiries they may actually go ahead and make another axle that will accommodate our bikes. Wishful thinking at least.
 
The only other option for a rear rack, other than seat post ones, is the Thule that I could find. It's why I went the way I did.

Maybe now that they have had some additional inquiries they may actually go ahead and make another axle that will accommodate our bikes. Wishful thinking at least.
Old Man Mountain can still do a rack for the front, just not the rear with the BH split pivot design. They did say that if demand is high enough, they will make a rack for us BH users - so email Old Man Mountain at

info@oldmanmountain.com

To request they put an Old Man Mountain rear rack for full suspension BH bikes into production!
 
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PDoz

Well-Known Member
So I think the stress on the dropper post itself is my biggest concern.
I came across a guy recently with one of those racks on his trek full suspension -7000 km trouble free. He had the topeak trunk mpx with tools / clothes etc in the bag and the option of unzipping the panniers for extra stuff. I think he mostly rides rail trails / easy dirt rather than hardcore mtb stuff. My concern would be hitting the rack with the rear wheel at full compression ( my little seat bag got ripped off when I landed from a jump)

For what it's worth, I have a trax towing device mounted to my dropper post ( https://traxmtb.com/en/trax-2/ ) , I suspect towing 90 kg of child / bike up hills puts a bit more strain on the post than a rack? A replacement dropper post is relatively cheap if something goes oops.
 
Just a couple thoughts for BillH and Bikeman24 and their BH bikes & their search of a thru axle fitted rear rack: a thought and suggestion.....

Due to the non-response from the original owner of OMM in my desire to buy his rear phat Sherpa for the Haibike Full FatSix, I kept my eyes out on Ebay for an OMM fatbike rear rack. I contacted Robert Axle about my axle fitment and they were quick to respond back with the size I needed. Lucky for me, a frame mounted OMM Phat Sherpa rear rack became available. I already had the rear support arms and axle mount rack legs, so I was all set.

Now, back to your problems. Looking at my original rear thru axle tonight, it got me to thinking why you cannot adapt your present thru axle to fit this rack? Does your rear axle have a means of removing the locking lever as mine does (3mm hex head cap socket)? Basically, what needs to happen is the thru axle needs to be drilled and tapped on-center to fit the 2 stainless steel Robert Axle ends that thread into the thru axle. Any competent machine shop or bike shop should be able to help you in doing this.

I've enclosed a few pics I took while trying to cobble together my OMM/Robert Axle rear Phat Sherpa Rack with all parts bought off Ebay. Take note of my Robert Axle Thru Axle. This axle is made to fit 12mm rear hubs with a total length of 217-229 mm. This is done by the supplied spacers they supply with this particular axle. Note, on the right side of the thru axle, you will find a flat washer and spacer right next to that stainless steel axle end that is threaded into the thru axle. On my Full Fat6, I removed that spacer and flat washer. I'm thinking for a home modified thru axle, one stainless steel axle end (brake caliper side) will be threaded into your thru axle. I recommend a thread locker compound on this end. It is then inserted into your rear drop out and hub and threaded into your derailleur side dropout.

Photo 2: An appropriate sized allen wrench is used to turn the stainless steel axle end into the drop out into which it seats itself.

Photo 3: Then it's just a matter of threading on the derailleur side stainless steel axle end. I believe I used loctite on this side as well. This too, is turned into your threaded thru axle end using an allen wrench through the holes in the axle end....

Photo 4: This pic is of the legs which then get attached to the stainless steel Robert Axle ends using metric cap screws (forget which size and pitch I used).....as well as the long support struts. Note the small diameter hole and the larger diameter hole....the larger diameter hole goes over that extended nipple of the stainless axle end. The smaller hole lines up with the inside cut threads within the nipple. All a very smart, neat way to put the pack weight upon the axle.

Robert Axle Project/OMM make a great product and those thru axles are sweet. So if it's possible they can make a run of BH axles to fit your bike, that is the way to go. But this all here could be a good Plan B as long as that rear axle lever can be removed and a machine shop will work with you.

To take this one step further, I wonder if a machine shop could procure the appropriate sized 12mm bar stock and drill and tap the appropriate sized inside threads to accept those two s/s axle ends that Robert Axle uses on these thru axles......I don't see why not.
 

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BillH

Member
So if it's possible they can make a run of BH axles to fit your bike, that is the way to go. But this all here could be a good Plan B as long as that rear axle lever can be removed and a machine shop will work with you.
First, thanks for helping out. Appreciated.

This will be the only way I'll go to be honest. You are way..way..way more ambitious than I am. Take it as the compliment it is intended to be.

My Arkel Seatbacker 9 is my current Plan B 🙂
 

rich c

Well-Known Member
BillH: Old Man Mountain was bought out by The Robert Axle Project. Not sure of your rear axle diameter, but I see they list a 12mm rear axle in various lengths; from 172mm long, 167mm and 160mm. These axles are made to fit their racks. Link: https://oldmanmountain.com/product/12-mm-rear-thru-axle-1-0-mm-thread-pitch-and-167-160-or-154-mm-length/


Smorgasboard: I too would question attaching that seat post mounted rack on a dropper post. For one thing, you need to reef down on the attaching bolts pretty good to prevent the rack from fish tailing on you.

Before I settled on the front and rear Old Man Mountain Racks, I went for a good long time running a front OMM rack to fit my side panniers and a rear seat post rack and bag.

I settled on the Portland Design Works Bindle Rack with the Revelate Designs Terrapin dry bag, which is designed to fit and work with the PDW rack. It worked just fine, then again, I don't have a dropper seat post as you do. But the main thing is, you are really constrained on what you can bring along. On a warm day going long distance, I like to carry extra water, my ultralite seat to rest up in as well as the standard air pump, tire patching kit and spare fat bike tire tube. And that back is pushing the limits on the amount of stuff you can carry. For your purposes, it sounds like it would work.

But beware: Reaching full tire shock compression, my back tire would hit the bag where it fits on the seat post in the below picture. Your ideas of putting your rack even lower then what I have will definitely result in the rear tire hitting your rack.
I think I'm too old to get a leg over that rear bag!
 
I think I'm too old to get a leg over that rear bag!
I'm no flexible flyer myself anymore! I figured out by rolling the bike to a slow stop, to dismount while still rolling, stand on pedals and with left foot on the pedal, swing the right leg as high up as I can swing it, then dismount. Any hitches to that motion and we have problems. Even with the other panniers I use in the back, that same motion applies.

Between the small frame, the saddle height and those fat bike tires, she's a high rider for sure.
 

Wagonrd

New Member
Yeah, I questioned that as well. There are, however, racks that are elevated above the seat post mounting point. For instance:

View attachment 43450


View attachment 43452


So I think the stress on the dropper post itself is my biggest concern.
I had this rack on my full suspension santa cruz bullit ebike. The battery was a panasonic flat 52v battery. I had two problems that forced me to mount a joyci 48v battery on the downtube. 1). I could not keep the rack lined up with the rear wheel, it would swing a few degrees even tho I locked the rack grip and the seat tube with screws. 2). I could not swing my right leg high enough to clear the rack, especially when dismounting the bike, I had to lay the bike down to get off. A minor problem was the tail wagging caused by the rack and battery, this was a problem when traversing technical terrain.
 

smorgasbord

Active Member
The Topeak MTX BeamRack I ordered arrived an I did a trial fit:

WholeBike.jpg



RackCU.jpg


RackCU-Extended.jpg


I did a full compression on the rear shock and the rack still has good clearance above the tire. Even with the clamp PDT (Pretty Darn Tight) the dropper post action works fine and the rack doesn't seem like it'll rotate, at least with light weight. I need to try it out some, naturally.

The biggest issue for me is that with the seat dropped low (middle photo), the Topeak bags are taller than the seat and so it's hard for me to get on the bike without my leg hitting the bag. This is the "A" rack, which elevates the rack for rear tire clearance, and I don't think I can go with the version of the rack that doesn't elevate on my full suspension bike, although maybe if I attach it a couple inches higher (near the top of the fixed part of the dropper post) it might work.

At any rate, I'm looking for small/low trunk bags. I'm also looking at a new, larger under seat bag and a top tube bag.
 

Theguvna

Member
The Topeak MTX BeamRack I ordered arrived an I did a trial fit:

View attachment 44350


View attachment 44351

View attachment 44352

I did a full compression on the rear shock and the rack still has good clearance above the tire. Even with the clamp PDT (Pretty Darn Tight) the dropper post action works fine and the rack doesn't seem like it'll rotate, at least with light weight. I need to try it out some, naturally.

The biggest issue for me is that with the seat dropped low (middle photo), the Topeak bags are taller than the seat and so it's hard for me to get on the bike without my leg hitting the bag. This is the "A" rack, which elevates the rack for rear tire clearance, and I don't think I can go with the version of the rack that doesn't elevate on my full suspension bike, although maybe if I attach it a couple inches higher (near the top of the fixed part of the dropper post) it might work.

At any rate, I'm looking for small/low trunk bags. I'm also looking at a new, larger under seat bag and a top tube bag.
 

antboy

Active Member
Topeak has their (newer) Tetrarack setups that mount on the seatstays... 26lbs max load (they also have a matching front rack).

 

WalkinTarget

Active Member
I'm using an Ibera PakRak mini on my Haibike FullNine 6.0 and it is just big enough to carry a rainjacket, huge lock, tire pressure gauge, sunglasses, tire pump and a bottled water - well under the 22lb weight limit. I rarely find it to be an issue cornering with it since I don't turn too often on the arrow straight rail trail I primarily ride. Only issue I have is you do have to be aware of it when mounting and unmounting. You had better throw that leg like you mean it, as even the mini bag juts up above the seat height and will catch your leg if you don't fully commit to hopping on or off.

I bought it primarily based on its low price - its about half the price of similar setups from Topeak or OMM.