# Anyone thought of this, yet? 20mm front thru-axle for a fixed rear hub?



## Squidward (Dec 18, 2005)

I've read with great interest the modifications folks have made to mountain bike ISO disk front hubs to convert them into a fixed rear hub using a bolt-on sprocket. The problem with this is that the front hubs typically use 9mm axles while rear wheels use 10mm axles. That 1mm difference is not something that is trivial as the 9mm axle is weaker compared to the 10mm axle and you cannot thread a 9mm cone on to a 10mm axle.

The thought occurred to me that if someone were to make some adapters for a 20mm thru-axle to adapt it to be used on the rear of a fixie, the possibilities are endless. Typically, 20mm thru-axle hubs have a 110mm OLD so threaded spacers with a 5mm wide (for 120mm OLD frames) or 10mm wide (for a converted road bike) or even mixed size shoulders to allow for adjusting the chainline could be made easily and cheaply by someone with a lathe for a few dollars.

Anyone see any flaws in this idea? I was thinking of making four collars, two without shoulders to be threaded on to the axle to support the middle (held in place with Loctite or locknuts) and two with shoulders to support the ends and to provide the spacing needed to space it for the frame. I guess an extra collar can be placed on the drive side for extra stability if needed or the drive-side collar could be made a lot longer for the support. Shimano just introduced a new 15mm thru-axle standard with a 100mm OLD dimension that could be interesting for something like this, too.

Unfortunately, I'm not a fixed rider so I don't have a need for something like this or else I would have done so already. I'm just throwing ideas out there.


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## naawillis (Oct 6, 2004)

Squidward said:


> The thought occurred to me that if someone were to make some adapters for a 20mm thru-axle to adapt it to be used on the rear of a fixie, the possibilities are endless. Typically, 20mm thru-axle hubs have a 110mm OLD so threaded spacers with a 5mm wide (for 120mm OLD frames) or 10mm wide (for a converted road bike) or even mixed size shoulders to allow for adjusting the chainline could be made easily and cheaply by someone with a lathe for a few dollars.
> 
> Anyone see any flaws in this idea?


  

20mm thru axles are front hubs for big-hit mountain bikes. the first problem is that there is no place to attach a cog (but im assuming you're already on board with this thread). anyway, if that doesnt stop you, 20mm thru axles are not threaded. how will you tighten it down? if the point is a conversion there is NO WAY doing something like this could possibly be cheaper or most long lasting than the alternatives (parts actually designed to fit on the frame in question). if the point is to have something uncommonly DIY, i would gently suggest that you find another more feasible project.


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## Zero Signal (Feb 8, 2008)

Yeah a 20mm axle is huge. My Rock Shox Pike has one and it takes a special dropout. The Maxle system IS threaded with a QR lever, so it kind of acts like a cigar sized skewer. It would be done with a custom built dropout and using a 20mm TA mountain bike hub in the rear with one of those cogs that bolts to the disc brake mounts. It would probably increase the rear end stiffness some, but it would be marginal and I don't see any other conceivable benefits.


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## Dave Hickey (Jan 27, 2002)

Zero Signal said:


> Yeah a 20mm axle is huge. My Rock Shox Pike has one and it takes a special dropout. The Maxle system IS threaded with a QR lever, so it kind of acts like a cigar sized skewer. It would be done with a custom built dropout and using a 20mm TA mountain bike hub in the rear with one of those cogs that bolts to the disc brake mounts. It would probably increase the rear end stiffness some, but it would be marginal and I don't see any other conceivable benefits.



to the OP: I don't see a problem with a 9 mm rear axle... the old Keirin bikes were running 8mm rear axles without problem...


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## Squidward (Dec 18, 2005)

Dave Hickey said:


> to the OP: I don't see a problem with a 9 mm rear axle... the old Keirin bikes were running 8mm rear axles without problem...


Yeah, but those Keirin guys are running on a smooth indoor track, right? I'm talking about riding out on the roads complete with potholes and other obstacles that threaten to taco our rims and bend our axles. Remember when we were running freewheels on our old Suntour/Shimano/Campagnolo/Sanshin or whatever hubs and we would bend the axles even though they were 10mm in diameter?

The point is that this may be an alternative to someone trying to piece something together and doesn't want to deal with lockrings. The problem is that thin 9mm axle used on front hubs requires that you find a way to convert the hub to a thicker 10mm bolt-on or hollow axle. Using this you simply bolt the adapters to a 10mm axle and mount the cog. Done.

Maybe I _should_ try a fixie just so I can piece one of these together?


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## Squidward (Dec 18, 2005)

Zero Signal said:


> Yeah a 20mm axle is huge. My Rock Shox Pike has one and it takes a special dropout. The Maxle system IS threaded with a QR lever, so it kind of acts like a cigar sized skewer. It would be done with a custom built dropout and using a 20mm TA mountain bike hub in the rear with one of those cogs that bolts to the disc brake mounts. It would probably increase the rear end stiffness some, but it would be marginal and I don't see any other conceivable benefits.


No, no, no, I'm not suggesting that we actually use the 20mm axle and have to modify the frame to make it work. I'm, saying to make a set of simple aluminum adapters that slide into the hub axle like the 20mm axle but with a steel 10mm axle running through it. The adapters are threaded so they are held in place by the axle and they even provide the proper spacing to allow the proper chainline on the back end. Do I have to draw a picture?


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## naawillis (Oct 6, 2004)

Squidward said:


> Do I have to draw a picture?


no. i can picture it, but i cant picture it working well or figure why you would want to do it. if you are actually trying to figure this out, at least post what hub you're going to use - they're not all the same and there are some differences between thru axles and qr20 hubs. but basically, the only way you could have safe and well adjusted hub was if you could cnc those adapters yourself. otherwise, there is no way you're just going to find something which can press fit perfectly into the hub. you would have to adopt a tophat design for the spacers, fitting them down inside the 20mm at least 1cm or more (w/ expanding locktite). otherwise you would stress the 20mm too much. that is where the ENTIRE load of the rear wheel would be, negating ANY reason to use a 20mm axle. anyway, you would have to thread the spacers onto the axles so it wouldnt rotate (with locktite). then cone style locknuts for the spacers, and more spacers for the chainline you desire. i can see it working, but only in a machine shop. 

at this point you just have to hope your wheel is close enough that you can redish it with the same spokes. now you're ready to ride to the bar on the only bike in town with two rear axles. :idea:


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## FlintPaper (Dec 28, 2006)

It seems to miss the point too.

Somewhere along the line, you're going to lose the strength of the 20mm TA "skewer" or bolt (dependent on fork) and have to step it down to 10mm to get it into the dropouts. So you'll still have 10mm axles that you have found a complicated way to center in a 20mm tube. Unless you're planning to make a solid 20mm cylinder and weld 10mm dropouts to either end.

It's a creative idea, but even executed well I don't see it being stronger than a bolt on 10mm axle.


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## FlintPaper (Dec 28, 2006)

Correct me if I'm wrong, but this is what you're thinking of:

http://www.universalcycles.com/shopping/product_details.php?id=3955&category=2140

Right?


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## naawillis (Oct 6, 2004)

FlintPaper said:


> Correct me if I'm wrong, but this is what you're thinking of:
> 
> http://www.universalcycles.com/shopping/product_details.php?id=3955&category=2140
> 
> Right?


thats for truing stands. problems: 1) no axle, cant bolt into frame. 2) not threaded, so they cant fit onto an axle. could you run that with a regular qr? (deathwish)

but, yes, thats the idea. you could drill those out for 10mm axles, tap them, and it would be pretty much what i described above. but, the part circled in red might need to be smaller for maximum adjustability. you still need room for locknuts.

the problem of the wheel dish still applies.


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## FlintPaper (Dec 28, 2006)

naawillis said:


> (deathwish)


I think you captured one requirement to try this idea.


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## PeanutButterBreath (Dec 4, 2005)

Squidward said:


> Maybe I _should_ try a fixie just so I can piece one of these together?


Good idea. But before you piece one of these together you should see if you can bend the stock axle on a modern track hub. IIRC, freewheel hub axles were prone to bending because there was a long, unsupported section between the hub shell and the drop-out. Track hubs (and MTB front hubs) do not suffer from this design flaw, and as such do not likely need the "solution" that you are offering.

If you want to do this because you can, I am sure there are folks who will think it is a neat mod even if it doesn't serve any practical purpose.


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## FlintPaper (Dec 28, 2006)

I do think that it would be powerfully cool to have a Marzocchi TA front hub with a tommi cog on my track bike.

I just don't think it's worth the risk to personal health to be the one trying to make it happen.


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## Pablo (Jul 7, 2004)

Squidward said:


> I'm talking about riding out on the roads complete with potholes and other obstacles that threaten to taco our rims and bend our axles.


Sounds like a solution in need of a problem. I can't imagine bending an axle, certainly not before destroying a rim. It boggles the mind how rough, potholed, and obstacled a road would have to be to bend an axle.


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## Squidward (Dec 18, 2005)

naawillis said:


> no. i can picture it, but i cant picture it working well or figure why you would want to do it. if you are actually trying to figure this out, at least post what hub you're going to use - they're not all the same and there are some differences between thru axles and qr20 hubs. but basically, the only way you could have safe and well adjusted hub was if you could cnc those adapters yourself. otherwise, there is no way you're just going to find something which can press fit perfectly into the hub. you would have to adopt a tophat design for the spacers, fitting them down inside the 20mm at least 1cm or more (w/ expanding locktite). otherwise you would stress the 20mm too much. that is where the ENTIRE load of the rear wheel would be, negating ANY reason to use a 20mm axle. anyway, you would have to thread the spacers onto the axles so it wouldnt rotate (with locktite). then cone style locknuts for the spacers, and more spacers for the chainline you desire. i can see it working, but only in a machine shop.
> 
> at this point you just have to hope your wheel is close enough that you can redish it with the same spokes. now you're ready to ride to the bar on the only bike in town with two rear axles. :idea:


I have a miniature mill in my garage and I can make the adapters myself. I haven't done anything with this because I was throwing the ideas out there. I haven't decided if I want to even try fixed gear, yet. Yes, I know the spacers need to be threaded on and Loctited on.



FlintPaper said:


> It seems to miss the point too.
> 
> Somewhere along the line, you're going to lose the strength of the 20mm TA "skewer" or bolt (dependent on fork) and have to step it down to 10mm to get it into the dropouts. So you'll still have 10mm axles that you have found a complicated way to center in a 20mm tube. Unless you're planning to make a solid 20mm cylinder and weld 10mm dropouts to either end.
> 
> It's a creative idea, but even executed well I don't see it being stronger than a bolt on 10mm axle.


The point wasn't that I wanted to use a larger 20mm axle for strength, it was for the ease of conversion. Anyone with a lathe can whip one of these up fairly quickly compared to trying to convert a conventional disk front MTB hub to a 10mm axle. Further, if I did try this and found that I didn't like it I could use the hub for my buddy's mountain bike that uses a 20mm thru-axle.



PeanutButterBreath said:


> Good idea. But before you piece one of these together you should see if you can bend the stock axle on a modern track hub. IIRC, freewheel hub axles were prone to bending because there was a long, unsupported section between the hub shell and the drop-out. Track hubs (and MTB front hubs) do not suffer from this design flaw, and as such do not likely need the "solution" that you are offering.
> 
> If you want to do this because you can, I am sure there are folks who will think it is a neat mod even if it doesn't serve any practical purpose.


Back in the day I used to bend 3/8" chrome moly axles on my BMX bikes fairly regularly. These were 120mm OLD spacing and I was about half the weight that I am now. If I do this it's going to be a road bike conversion so 130mm OLD and, yes, I did gain some weight since I was 12 years old.



Pablo said:


> Sounds like a solution in need of a problem. I can't imagine bending an axle, certainly not before destroying a rim. It boggles the mind how rough, potholed, and obstacled a road would have to be to bend an axle.


So, I guess this guy and this guy were working on solutions in need of a problem. I actually got my idea from reading the first one I linked. 

I really like the idea of bolting on a cog instead of worrying about stripping the threads on an old-style freewheel hub to try fixed and I don't like the idea of using a lockring to hold it in place. If someone were to make a 6-bolt ISO fixed rear hub then I would buy it and try it but this seels to be an elegant solution to me. Maybe I should just stick with geared bikes...


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## FlintPaper (Dec 28, 2006)

Ok, now I start to understand why this might be desirable.

Given my lack of access to machining tools and the fact that I own a chain whip and lockring tool, it would be silly for me to attempt this. But perhaps not you.

I must admit, I only ride single speed, generally with White Industries freewheels. Thus the idea of threaded hubs must not bother me. I haven't had a problem with them yet, but I'm sure the first time I strip or cross-thread an expensive hub I'm going to think back to this thread and see the light.

If I did ride fixed (maybe someday?), I think I would still choose to emulate one of those links directly and not use a TA front hub.

A neat idea. Thanks for bringing it to my attention.


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## PeanutButterBreath (Dec 4, 2005)

Squidward said:


> Back in the day I used to bend 3/8" chrome moly axles on my BMX bikes fairly regularly. These were 120mm OLD spacing and I was about half the weight that I am now. If I do this it's going to be a road bike conversion so 130mm OLD and, yes, I did gain some weight since I was 12 years old.


How much weight did you gain!? Because most of us are grown-ups around here AFAIK, and I am not seeing much buy-in on you plan to solve the bent-axle-on-fixed-gear problem. Not in this thread, not on RBR, not on MTBR, not anywhere.

I have ridden full rigid MTBs with 135mm OLD 10mm axles on the rear and hollow 9mm QR axles on the front all over the Sierras and Rockies with no bent axles.

As was mentioned, any impact that is going to bend your axle will blow your tire and trash your rim first. Replacing an axle is the cheapest of those problems to fix.

I'm not saying you shouldn't do this just for yucks. I guess I am saying you should probably just fire up that lathe rather than try to sell anybody on the necessity of this project.


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## naawillis (Oct 6, 2004)

PeanutButterBreath said:


> I am not seeing much buy-in on you plan to solve the bent-axle-on-fixed-gear problem. Not in this thread, not on RBR, not on MTBR, not anywhere.
> 
> I have ridden full rigid MTBs with 135mm OLD 10mm axles on the rear and hollow 9mm QR axles on the front all over the Sierras and Rockies with no bent axles.
> 
> I'm not saying you shouldn't do this just for yucks. I guess I am saying you should probably just fire up that lathe rather than try to sell anybody on the necessity of this project.


well said. im 200lbs, and i KILL parts. i aint never bent no axles (i keep my hubs well adjusted though). 

squiddy, maybe you can corner the market for extra heavy duty hubs for fixed freestyling and trail riding. 20mm solid axles! NEV-R-BEND!!

seriously, if you dont have one laying around and are going to buy one, i think youll find that a new 20mm hub will be nicer and more expensive than something you'll want to guinea pig on, IMHO. i dont know of any cheap hub-only 20mms, because anyone who needs one needs a decent one. but seriously, fire up that lathe and post some pics. they'll be right at home on fixed gear gallery  

.


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## Pablo (Jul 7, 2004)

Squidward said:


> I So, I guess this guy and this guy were working on solutions in need of a problem. I actually got my idea from reading the first one I linked.


I think that's the definition of a solution looking for a problem. Current products work well without issue. I work the other way. For example, my commuting pants kept rubbing on my chai and ripped, so, i added a button to the new pants and the problem was solved. 

That said, I have no problem with you trying something new. I'm just a guy who'd rather ride bikes than work on them or reinvent them. Have at it. Maybe it'll work and you'll probably have a good time. My point is, however, that there's not a real pragmatic basis for your efforts. Nevertheless, best of luck.


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## Squidward (Dec 18, 2005)

PeanutButterBreath said:


> How much weight did you gain!? Because most of us are grown-ups around here AFAIK, and I am not seeing much buy-in on you plan to solve the bent-axle-on-fixed-gear problem. Not in this thread, not on RBR, not on MTBR, not anywhere.
> 
> I have ridden full rigid MTBs with 135mm OLD 10mm axles on the rear and hollow 9mm QR axles on the front all over the Sierras and Rockies with no bent axles.
> 
> ...


If you read the posts in chronological order you will see that I was answering Dave's posting about using a 9mm axle in the rear. Do they even make a 9mm axle long enough to use in a rear 130mm OLD hub along with threads for the locknuts? I was stating that I've bent 3/8" cro-mo axles back in the day at half the weight I am now. What makes you think I won't bend a thinner 9mm rear axle today? I've bent 10mm axles and most of us here have, too. We just haven't taken our rear hubs apart and checked the axles to see if they are true or not. Oh, and by the way, your 135mm OLD 10mm axles are built on a freehub design, right? Not the older hub and freewheel design, right? As the hub got wider to accomodate the greater cog count the drive-side wheel bearing moves closer and closer to the centerline of the wheel, making it easier to bend it in the middle. The freehub design was introduced to eliminate this as they moved both bearings outwards to change the leverage ratio, making it next to impossible to bend it.

As far as trying to sell anything, no, I'm not trying to sell anything. I was asking if anyone had tried this and what's people's opinions of this are. Did you read my original post? All of it? Now that I see that just about everyone here thinks it's a bad idea then, fine, it's a bad idea. Case closed. I have never had any intent to make this thing nor try to sell it to anyone, not even as an idea. I now have even less desire to try fixed gear because of this thread. Had I wanted to persue this my original post would have had pictures of the completed parts along with flying aluminum chips as a 3/8" end mill cuts the parts out of a chunk of 6061.


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## PeanutButterBreath (Dec 4, 2005)

Juto clarify, I was perfectly aware of the chronolgy of this thread when I wrote my response.

I have never bent a solid 10mm rear axle. Nor have I bent a hollow 10mm rear QR axle. Nor have I bent a hollow 9mm front QR axle riding a rigid mountain bike over terrain that no road-going fixie is ever going to see (unless you like to plow into a lot of curbs). BTW, my 135mm OLD rear hub is a singlespeed freewheel hub.

I know that 3/8" BMX axles can bend. But BMX components in general are usually the cheapest of cheap junk (even the $$$ stuff). Also, I don't huck my fixed gear over 12 stair sets to flat.

By "selling" I mean selling the _concept_ not any product per se. I am just not interested in an axle "improvement" that would only kick in after I crushed my rim (and my tailbone).

All of that said, I still see no reason not to do this. You might also pitch it over on the MTBR Singlespeed board. There are more and more people riding fixed off-road, and some of them might even have a 20mm TA hub sitting around.


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