# BigD 36er



## ktm520 (Apr 21, 2004)

Looking at building a 36er for my brother who is 6'4"/300lb. Would appreciate a sanity check on what I've got so far.

front center - 750
rear center - 475
hta - 69.5
fork offset - 80
fork AC - 510
trail - 85
bb height - 318

Fork tubes:
blades - 1.25 x .049
crown - 1.13 x .049

Frame tubes:
dt - 1.5 x .049
tt - 1.25 x .035
st - 1.38 x .065
cs - .75 x .049
ss - .75 x .035

Yoke has clearance for a 22t at 44mm chainline, but would primarily run a gxp direct mount 26t at 50mm chainline.

The big thing I'm missing is dimensions on the tires. What's the true diameter? Location of widest point of tread? Casing width? Does anyone have tire dimensions?


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## todwil (Feb 1, 2007)

Im not 6'4 but I hit...a...pounce the scale at about the 300# mark so Im close to his size and the frames Ive done are similar the differences being I used .035 for all the tubing even the ST but adding a slug made from .065 turned down at one end to slip inside .035. The tire rim dont quite make it to 36" and the widest part using the VEE tire is 17.5" and the Nimbus maybe closer to 17.750"


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## ktm520 (Apr 21, 2004)

Thanks todwil. Haven't been to worried about weight, but looks like there might be room to optimize. Main reason for sticking with .065 for the full length of the st is due to the knee. How long did you make your seat collar slug? How did you join it to the seat tube?

I ran a crude model of the front triangle to check for stress levels at the knee and they are pretty low compared to the tt-st junction. 035 would probably be ok without supporting the knee, but I'd feel much better about it if someone gave me the head nod on that. I can't find any examples of anyone using a st like that.


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## Walt (Jan 23, 2004)

I've done them that way, mostly for FS bikes, and you'll be fine assuming you are very good at fusion butt welds on thin tubing. If you are worried about it, or not a fantastic welder, you can make a little gusset for the backside of the joint.

For the slug, you'll need a lathe - just turn down the .065" some to slip-fit into the .035", then fuse, then join your TT and seatstays. Done.

-Walt


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## ktm520 (Apr 21, 2004)

Sounds good. I can handle all that.


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## todwil (Feb 1, 2007)

Heres a couple pics showing the slug I believe Paragon sells these slugs now so it can be as easy as click the buy button!!


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## ktm520 (Apr 21, 2004)

I hear you need to silver braze the crown race after tig'ing the bottom. Is the 56% silver wire and flux from henry james what I need? Hoping I can use map gas for this.


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## Eric Malcolm (Dec 18, 2011)

You can use either 56 or 45% silver for that application. MAPP will do it. Just be patient in getting the temp up but once there, all good.

Eric


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## ktm520 (Apr 21, 2004)

Probably a dumb question and surprisingly found no info on this subject, but would standard plumbing type solder not work on this specific application? It is basically there to fill the gap between the crown and steer to keep it from fatigue cracking, right. Seems pretty non structural and purely a filler. For that matter, it is really even necessary to tig the bottom of the race? It's captured by the crown segments and can't really go anywhere.


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## Eric Malcolm (Dec 18, 2011)

ktm520 said:


> Probably a dumb question and surprisingly found no info on this subject, but would standard plumbing type solder not work on this specific application? It is basically there to fill the gap between the crown and steer to keep it from fatigue cracking, right. Seems pretty non structural and purely a filler. For that matter, it is really even necessary to tig the bottom of the race? It's captured by the crown segments and can't really go anywhere.


Fill with silver. You can do this with Silver only - no Tig. I have several times. Ridden bikes that have been Tig'ed without problems. Nothing wrong with brass either.

Your choice. Use what you have.

Eric


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## ktm520 (Apr 21, 2004)

This is going to happen. He just ordered rims/spokes/tires.

I was looking at the Paragon seat tube collar and it is only 2.38" long. That seems awful short to me, especially for a big guy. Would it be worth making a longer collar or are my concerns unwarranted? I really think a longer collar, maybe 4" at least, would transfer the load into the st better.

I'm going to stick with .75x.049 on the chainstays. There is an approximate 10% in crease in stiffness for only a 100g weight penalty. I think it's worth it.

Tubing is on order. Only variation from original list is the .035 st and dt.

Fork tubes:
blades - 1.25 x .049
crown - 1.13 x .049

Frame tubes:
dt - 1.5 x .035
tt - 1.25 x .035
st - 1.38 x .035
cs - .75 x .049
ss - .75 x .035

One other questions, steerer tube for fork, Nova 2.35/1.5 or HJ 2.1/1.6 or HJ 1.65/1.14 OXP?


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## todwil (Feb 1, 2007)

The reason for the slug being this length is it keeps the seem captured by the TT and SS. The one I have made are have 2" exposed. Post up pics of your progress.


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## Francis Buxton (Apr 2, 2004)

ktm520 said:


> Probably a dumb question and surprisingly found no info on this subject, but would standard plumbing type solder not work on this specific application? It is basically there to fill the gap between the crown and steer to keep it from fatigue cracking, right. Seems pretty non structural and purely a filler. For that matter, it is really even necessary to tig the bottom of the race? It's captured by the crown segments and can't really go anywhere.


If all else fails on that, you can mail the fork to your brother without the crown race on it and I can silver it on for Zac (assuming I know your brother).

I also have a steerer tube I can sell your brother for $25 that doesn't need a crown race brazed on b/c it's built into it. It's a custom run a friend of mine had done several years ago.


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## ktm520 (Apr 21, 2004)

todwil said:


> The reason for the slug being this length is it keeps the seem captured by the TT and SS. The one I have made are have 2" exposed. Post up pics of your progress.


I kinda of follow your theory. My thoughts are that the more post insertion/contact with the id of the st, the strong/stiffer the joint all the way down to the point that the post ends. With a short collar, the effective insertion length is only as long as the collar. It's similar to a composite joint although the surfaces aren't bonded. Again, I may be over designing the joint as your experience has proven it to hold up. Maybe it's more to have the butt joint captured by the tt, but I'm not seeing it.

You said your collar has 2" exposed, how far does the shoulder protrude into the st?

Will definitely post up progress. Will be a week or two before I get started though. Waiting on detailed measurements of the tire and have another frame to finish first. I have a few design details to finish up on the yoke, but other than that will be a straight forward build. It's going to barely fit in my jig.

Francis Buxton, I'd like to see some more details on this custom steerer you have. Either way, I don't have any issues silver brazing the crown race. Got a pipe fitter buddy that's going to learn me.


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## todwil (Feb 1, 2007)

The slug is 3" long with an inch inserted! I think this is long enough especially since I went to 31.6 diameter seat post.


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## ktm520 (Apr 21, 2004)

Thanks todwil. I bought a 12" piece of 1.38x.065 when I ordered all the other tubing, so i think I will make my own vice buying the Paragon 30.9 collar. Ya, I like 3" alot more than 2.38".


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## ktm520 (Apr 21, 2004)

I hope this fork crown segment pattern works.


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## ktm520 (Apr 21, 2004)

Making good progress. BB/yoke/chainstays/drops are welded. I started welding the fork crown last night and it's about 40% done. The crown race I got from Nova is really tight on the steerer. Tight enough I will probably have to hammer it into position. Two questions: is this normal and does there have to be a certain amount of clearance/gap between the two for silver to properly flow? I have some races coming from Paragon that might be here today. Interested to see what they look like.

This fork looks ridiculously beef with the 1.25" legs. The qr drops look like tooth picks sticking out of the end of the leg.

Another tight deadline. I was going to try and finish it before xmas and surprise him, but I inadvertently ruined the surprise.


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## Live Wire (Aug 27, 2007)

It should be an easy slip fit, hammering it on means the fit is way too tight for good brazing....its normal to have to work on the race a bit to get it to fit right.
The Paragon races will be better though.


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## todwil (Feb 1, 2007)

Yea I use drimmel with a drum sander to make it fit easier. Got any pics of your progress?


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## ktm520 (Apr 21, 2004)

BB/yoke in the fixture is for a different frame. Got my Anvil dummy axles tonight. Very nice. Finally get to use the post punk I picked up last spring. Not my best welding on the crown. It proved a little trickier to get torch/hand positioning right than I was thinking.


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## ktm520 (Apr 21, 2004)

Managed to keep tt copes in phase this match.


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## todwil (Feb 1, 2007)

Looking good the fork turned out great!


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## ktm520 (Apr 21, 2004)

Thanks man! It was a huge relief to get that fork crown finished. When I asked my brother if he was ok with being my fork test dummy, his his response was "maybe I'll get a full face."


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## life behind bars (May 24, 2014)

Very nice work on the fork, tubing specs?


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## ktm520 (Apr 21, 2004)

tiretracks said:


> Very nice work on the fork, tubing specs?


See post #11


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## todwil (Feb 1, 2007)

So did he get it for X-mas? Any more pics of progress?


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## ktm520 (Apr 21, 2004)

Finished it up late Tues. Brother even got to lend a hand finishing the fork. I lived and breathed that frame for 10 days. Was a little hard to see it go. Of course it's been raining the last three days so probably no dirt before he heads home. A urban ride is planned for tomorrow. Dad, brother, and my son, three generations of mtb'ers. Three of us on Marklar frames.

I've got a ton of pics to upload later. For now, it's the couch and a few beers.


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## ktm520 (Apr 21, 2004)

Turning the crown race


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## todwil (Feb 1, 2007)

NICE! Yea beers and couch sounds deserving!


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## ktm520 (Apr 21, 2004)

https://flic.kr/s/aHsk71RH5P


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## ktm520 (Apr 21, 2004)

This is what it looks like after a tacked front triangle falls off the bench.


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## unterhausen (Sep 28, 2008)

did it work? how did you generate it?



ktm520 said:


> I hope this fork crown segment pattern works.
> 
> View attachment 947143


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## ktm520 (Apr 21, 2004)

Yep, perfect. Its cad generated. Modeled the tube as thin sheet metal and then flatten for the pattern. Used same technique for seatstays.


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## ktm520 (Apr 21, 2004)

This is what I ended up with on geometry.

front center - 750
rear center - 475
hta - 69.5
fork offset - 90
fork AC - 510
trail - 75
bb height - 324

Fork tubes:
blades - 1.25 x .049
crown - 1.13 x .049
Nova steerer 2.35/1.55

Frame tubes:
dt - 1.5 x .035
tt - 1.25 x .035
st - 1.38 x .035
cs - .75 x .049
ss - .75 x .035

I'm glad I dropped the trail from 85 to 75. Ended up using the Paragon 30.9 seat collar. 

Really only had one issue with the build and that was the brake mount on the the fork. It was the last thing on the list to finishing the frame and in hast I didn't do a test fit after tacking. Had to space the brake adapter in ~1mm. Not sure what happened. I used a Anvil Post punk to position the mount and it stayed put after welding. I must have setup the jig wrong, but I don't see how.

I'm really anxious to get some feedback on wheel stiffness (142 hub with no offset) and frame stiffness. He didn't notice anything thus far but thanks to rain, we were limited to urban riding. The more I think about it, if I did it again, I would more seriously consider using a 83mm bb and offset the rear end to allow for better bracing angle of the driveside spokes. Maybe not necessary depending on how much rider weight and how aggressive of a rider, but that is one big'o hoop. The Nimbus rims are so over built, there is a good chance it is of minimal advantage.

Here's a thought:
When I cap the ends of the chainstays, the weld between the cap and drop plate causes the plates to pull in on the opposite tip. It's pretty small and you'd probably never notice it unless you put the frame in a jig. I thought about not even welding that seam and using it as a drain. Feedback?


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## Sasquatch1413 (Nov 6, 2008)

The frame was being built for me and I just got it out last night and rode it on some rocky singletrack. Not a lot of sustained climbs so I can't really comment on that but the bike was amazing. Its still a rigid bike so don't think the big wheels make up for suspension but there is a crazy amount of smoothness from the big diameter. Momentum is amazing once you are moving, it rolls right through rough chatter. It takes more effort to get the wheels spooled up and the front end is not very easy to pull up but I rode it through all my favorite techy trails with rock ledges and it just ate them up. Felt slightly clumsy through some stuff but I'd say overall its more nimble than my fat bike. Came out awesome and was giddy the entire time I was pedaling.


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## shirk (Mar 24, 2004)

ktm I was looking at your pics and like your frame jig. I am planning on one the same style.

Did you make a custom shim to align the bb to the centre line of your jig? Also did you make cones for your headtube? 

I have a friend that has offered up some free lengths of the 1" wide 1010 profile, I am debating on using it vs buying the wider 3" wide 1530 profile.


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## unterhausen (Sep 28, 2008)

this is a really neat thread, thanks for posting


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## DualRollers (Apr 24, 2014)

I work with Zach and just saw pics of this thing today... excellent work! I can't wait to see it out on the trails, its a beast.


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## unterhausen (Sep 28, 2008)

ktm520 said:


> Yep, perfect. Its cad generated. Modeled the tube as thin sheet metal and then flatten for the pattern. Used same technique for seatstays.


I tried to replicate this today with solidworks and I found out my skills are really rusty


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## ktm520 (Apr 21, 2004)

shirk said:


> Did you make a custom shim to align the bb to the centre line of your jig? Also did you make cones for your headtube?
> 
> I have a friend that has offered up some free lengths of the 1" wide 1010 profile, I am debating on using it vs buying the wider 3" wide 1530 profile.


Yes, I made shouldered bushings to slip in the bb shell that are the correct size to center the shell on the beam. The beam is 3030 and the trunk is 1530. 1010 will work for ancillary supports, seat tube, seat stays, etc., but I wouldn't use it for the main beam or trunk. I've got ~200$ in 8020 parts and it was worth every penny. Bought it all from their ebay store. I don't have much room in my shop (small two car garage) so this fixture is perfect for me as it is really small and easy to throw up in the attic when not being used.


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## ktm520 (Apr 21, 2004)

unterhausen said:


> I tried to replicate this today with solidworks and I found out my skills are really rusty


I have very little experience with solid works, but have access to a seat. I'll see if I can figure it out if I get bored.


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## todwil (Feb 1, 2007)

Ride report?.....Trail pics?


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## Sasquatch1413 (Nov 6, 2008)

Below is a link to my Flikr album of the complete bike after powder coat. I went with Kawasaki Green and love it. Total build came out to just over 36 lbs.

https://www.flickr.com/photos/[email protected]/sets/72157647909315904/

I've put about 50 dirt miles on it in the past couple weeks and it is my favorite bike by far. Probably mostly due to it being a new bike and so different but the ride qualities are astounding. There is some flex but not sure if its due to the frame or the big wheels, nothing that causes chain drops or hurts handling in any way though. When you mash it doesn't feel like power is laid down as efficiently, I'm thinking this may be due to spoke windup or wheel flex? Not a big deal, just a little different feeling.

It has a crazy smooth feel for a rigid. And the heavy hoops roll like crazy if the trails starts pointing downhill. Feels like if you keep it at a certain speed, the momentum just carries you through everything. If you slow down you start to feel the heavy wheels though. I don't have any extended climbs in KC so climbing isn't an issues at ll.

We nailed the steering with 75mm trail, front end feels quick with no huge difference from a 29er. You get a slight sluggish feeling from the long wheelbase I think. Its harder to whip through corners and takes more effort to pull the front end but after riding it for a week, I've mostly adapted to its manerisms. When I ride with other people they are always amazed at how fast it is.

In short, this bike if farking awesome and it makes me giddy every time I swing a leg over it. If you've been thinking about having a 36er built....DO IT!


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## Francis Buxton (Apr 2, 2004)

We were all pretty disappointed that you did not bring it with you last night Zac.


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## Sasquatch1413 (Nov 6, 2008)

Would have loved to, I hate leaving it in the garage. Hopefully will get a replacement Hadley freehub this week and will have it out this weekend. Maybe next possum trot.


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## todwil (Feb 1, 2007)

Great choice of color........yeh the first hub I laced in lasted 7 1/2 miles (Shimano 525) I didnt think it would last forever but I was hopin for further....Now CK and Industry9 with no problems.


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## Sasquatch1413 (Nov 6, 2008)

Todwil I hope I don't have to upgrade the rear hub already. I went with Hadley as they have a great reputation with clydes. Hoping the new freehub with three pawls that all engage at once will be the fix. 

Lacing up those big hoops were the hardest wheels I've built. Didn't come up to tension very straight. Don't really want to lace in another one.


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## unterhausen (Sep 28, 2008)

This is a really cool thread, I'm glad the owner is posting



ktm520 said:


> I have very little experience with solid works, but have access to a seat. I'll see if I can figure it out if I get bored.


I got to the point where I flatten the part and solidworks crashes every time. I have one more thing to try before giving up


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## ktm520 (Apr 21, 2004)

It was depressing to see it leave town and not get to ride it on dirt. Might be visiting KC sooner than later. This was an extremely rewarding build. Not a single thing I would do different design wise.

unterhausen, solid edge was also a little finicky with how I setup up the cuts. For example, the steere cut on the crown segment also gets the fwd ear cut where the two segments meet at the front of the steerer. I originally made the circular and ear cut in one feature and it didn't like that. Separated them into two separate features and it computed. I also found that if the joining tube is the same diameter as the mitred tube, I had to cut off the sharp points on the ears to get the pattern to compute. I'm getting ready to print some patterns for another fork I'm starting on today.


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## Sasquatch1413 (Nov 6, 2008)

After even more miles on the Yarder and taking it on a bike trip for some different riding conditions this weekend, I couldn't be happier with this bike. I went down and rode Lake Leatherwood, Slaughter Penn Hollow, and Blowing Springs in Northern Arkansas. There are small mountains down there with some extended steep climbing. Once you get to the top, its very flowy singletrack back down with loose gravel corners. The Yarder did great climbing. Technical climbing with rocks and roots was so much easier as the big wheel just rolled over everything and it was easier to keep a constant speed. The rolling factor outweighed the disadvantage of the heavier wheels. Headed downhill, its not as nimble as a 29er but its something you can adjust for fairly easily. I was keeping up with other riders on full suspension 29ers and sometimes gaining on them. I even sometimes forgot that it was a fully rigid bike until I'd do small drops and remember once I slammed the ground. It is such a capable bike. Even on very fast windy trails, I could feel some flex but it wasn't anything that I disliked. 

The wheels have been holding up ok so far, I'm still doing random tweaks to spoke tension to get the rear dialed in. I have both ends setup tubeless, front is ghetto, rear uses strapping tape and foam. Both methods seems to be holding up well with the strapping tape being slightly lighter than the ghetto. I used foam as I could not get the tire to seal up with just tape. The wire bead and two ply sidewall was too rigid and crooked that the the air gaps where too big. It never popped up on the bead. With the ghetto tube or the foam it aired up great.

In the past, rigid bikes have really taken a toll on my hands, arms, and shoulders but this bike is smooth enough that it doesn't seem to bother me. Even after a 30 mile weekend, my upper body was great. The 36" wheels are very smooth.


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## Sasquatch1413 (Nov 6, 2008)

I've got a few hundred miles on the Yarder now (moved away from BigD as it was too douchey). I can't explain how much I love this bike. Its my new norm and I rarely notice it being too long or hard to handle. I ride it solely on dirt with lots of rocky technical trails. I ride this **** out of it and love it. After a long 20+ mile ride it does start to wear on you a little bit especially on techy trails where you have to pull up the front end a lot. Its funny how amazed people are when i ride it fast. 

I ended up with a narrow wide chain ring and Zee clutched derail to stop chain drops. Running a 26t front ring. In KC with limited downhill runs, the 200mm front/rear rotors and Deore hydraulics have been stopping just fine. I'd probably like to run a dual piston caliper front/rear if I was riding in areas with lots of elevation. 

Front wheel has been holding up great, rear wheel not so much. First 100 miles was great then spokes started to come loose every ride. Only brake side spokes, drive side held tension just fine. I bumped up tension to 120kfg to see if they would help hold the spokes better but doesn't seem to help. I'm either going to relace with Sapim spokes (running unicycle.com spokes now) or rebuild with spoke prep or maybe even use some whicking loctite.

The Vee tires that Walt and friends got made are really good. Tread works great even in slick conditions. I have cut a tire surprisingly enough but it wasn't so bad that I couldn't patch from the inside and keep it rolling. Rims are super burly and show no signs of wear even after some good hits from bottoming out the tire. They set up tubeless pretty well too.


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## Sasquatch1413 (Nov 6, 2008)

A short video of some trail riding at Swope Park in Kansas City.


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## todwil (Feb 1, 2007)

Yea Sapim spokes and prep should yield a better result Ive settled on a 26t up front and a oneup 42 on the rear and this seams to work in most places. Glad your still liken your bike after all the miles these bikes are a lot of fun to ride.


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## Drew Diller (Jan 4, 2010)

@Sasquatch1413, seeing that short video is very helpful, the bike really looks like it scales to your body. I wouldn't necessarily have realized anything was out of the ordinary if I was presented that video with no context.

Very nice!


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## G-reg (Jan 12, 2004)

Where are you guys seeing huge Sipam spokes available? Uncut blanks? On my Yardbike the rear end is pretty flexy, if I could rebuild the rear wheel into a 170 hub I think I would. Thinking the single length uni spokes were all that's available limited hub choice.


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## Sasquatch1413 (Nov 6, 2008)

I just contacted Sapim directly and they would sell straight gauge 400mm blanks. You can have a shop order them or they said they'd sell them direct to the public. I contacted Dans Comp to see if they could cut spokes at 370mmish and their machine went up to 360 but they thought they could fudge to 370. Not sure who else has the capability to cut them accurately.


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## ktm520 (Apr 21, 2004)

G-reg, what did you use for chain/seat stays on your 36? I got to borrow the Yarder for a couple weeks and rode it on my local trails which are faster/tech'ish trails, were my bro's trails are little bitter slower and much more tech. Granted, I'm only 170lb, but the rear end was solid. It took me a couple laps to really get used to the handling characteristics of the circus wheels, but after that I was ripping around just as fast as my normal wheel'ed bikes. Even hit our dj line on it. I was surprised how much I liked it. Anquious to see how it rides in the KC chunk next time I'm out there.


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## Sasquatch1413 (Nov 6, 2008)

Well the unicycle.com spokes aren't holding up. Just broke two drive side spokes in the rear. Broke at the hub. Time to get some Sapim blanks and rebuild the wheel.

Front wheel seems to be holding up OK, will wait for it to start spitting spokes before I rebuild it.


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## todwil (Feb 1, 2007)

Yea I could only get about 500 miles on the Unicycle ones Im getting twice the distance on the others. I have the Hozan threader and it works good it takes a little longer than Phil threader but it does the job and it was around $125


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## Sasquatch1413 (Nov 6, 2008)

todwil said:


> Yea I could only get about 500 miles on the Unicycle ones Im getting twice the distance on the others. I have the Hozan threader and it works good it takes a little longer than Phil threader but it does the job and it was around $125


What do you use to cut the spokes accurately?


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## Eric Malcolm (Dec 18, 2011)

Use a steel rule and put the zero end into the J of the spoke and measure from there. I cut with wire cutters then finish off on a bench grinder. Been doing it that way since the '70's. It's not really precision, but then it doesn't have to be. It's nice to be manufactured perfect, but not absolutely so. Run-out can be dealt with as you tension the wheel up.

Eric


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## todwil (Feb 1, 2007)

Real similar as Eric has said I use an aluminum ruler that I drilled a hole in at zero line measure to length mark with a fine point sharpie snip with wire cutters grinder clean up then into the hozan it goes. there is a couple of good youtubed ids on this.


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## Sasquatch1413 (Nov 6, 2008)

Slight complication with the 36er. Curious on input regarding failure mode. CS too rigid transferring all the stress to the dropout? Tube cap weld on backside of break weakened area? Or just not strong enough for my big ass?

Chainstay is 0.75"x0.049". Dropout is paragon slider.

I'm thinking just bevel the break, weld it up, and add gussets.


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## life behind bars (May 24, 2014)

Broken along the backside weld? Paragons bullets might be the answer.


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