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Michael’s Titanium Fatbike from XACD

At 6′ 7″ Michael’s pretty tall, and he likes his bikes on the chubby side. As you might imagine finding something off the peg is going to be a stretch in every sense…

I am a strong advocate of the N+1 philosophy of bike ownership, and when fat biking took off I rented one and found I loved it! I rode an RSD Mayor for a season and while there was nothing really wrong with it, I did think there were a few areas that needed tweaking. Even though it was one of the larger XL frames on the market the bike was really too small. It was stable, but a bit slow and plodding. The bike used a 190mm BB axle and with 57mm pedals to clear my boots the Q factor was insane and hurt my knees!

Custom bike to the rescue (of Michael’s knees)!

So I started playing around on SketchUp, designing my ultimate fat bike frame. I wanted to have a short stem for quick steering, so that meant a longer top tube. To avoid a super long wheelbase, short chainstays were in order.
I wanted to fit the biggest tyres around, Vee Tires Snow Shoe 2XL, which need a 197mm hub to clear the chain. I wanted to reduce the chainstay length by an inch over the Mayor, and take the BB axle down to 170mm for a 20mm narrower Q factor.
When I looked at all these wants, it was clear the chainstay wouldn’t be able to articulate around all these set points, so I decided to do a full plate horseshoe yoke, problem solved!

I’ve just looked up pictures of the Snow Shoe 2XL, it’s a monster even by fat bike standards! You also often forget that super fat tyres mean longer bottom brackets and axles to fit everything in, they were doing this long before ‘Boost’ was a thing!

Some people say that you can’t have a 197mm rear hub with a 170mm BB axle as the chainline doesn’t work. This is nonsense. With a Race Face Turbine crank and a flipped chainring the chainline is absolutely perfect. In fact, better than the Mayor so I’m not sure where this rumour comes from!
I knew I would used a T47 bottom bracket, it just makes so much sense. It can clear a 30mm axle and still use internal bearings. I could make the BB shell 125mm wide, allowing the chainstays to be braced further apart for a stiffer rear end.
I designed the frame to use a 450mm 30.9 post at the height I needed. The top tube and support mast are as low as possible to accommodate this. I also made sure if I ever use a dropper, the insertion and collar height works.
I thought about internal cable routing but decided against it. It is pretty simple and clean having a single boss that holds 3 cables under the top tube so I went with that. I didn’t want to start drilling holes in the frame!

Large T47 shell and plate yoke compliment the design nicely!

Michaels’ nailed the details there, a fine insight into the things you should be thinking about with your own frame designs. Although with larger frames you might not want to worry too much about the chainstay length, I’ll say more about that later!

With that sorted it was time to pick a fabricator:

I shopped it around to the usual suspects. Titan didn’t respond. Waltly said that they couldn’t do the yoke, but gave a very low price, and then there was XACD…
Porter responded with a full CAD drawing based on my model, a pretty high price, and a demand for approval and deposit! You gotta love this guy! He is super aggressive, but also super on the ball.
I read reviews. Everything negative about XACD revolves around Porter’s attitude, but there was nothing negative about the quality of their frames, I felt I could manage Porter!

As always it’s about feeling comfortable about who you’re working with, and as Michael says, XACD are known for their quality fabrications. I’m surprised Titan didn’t reply though as I’m sure they would have been able to take the job on, an old email address being used perhaps?

So we negotiated the price down a bit; $1500 inc shipping to Canada. This included the plate yoke, T47 BB, thru axle and tapered head tube with CNC engraving, the extras started to add up!
Porter would provide a revised drawing within hours of my design change requests. We revised the plan at least 10 times before production and he never seemed annoyed at my constant tweaks!

This is a recurring theme with all the fabricators, even Porter appears to have good patience for revising drawings. It’s only when he doesn’t hear straight back from you that he starts to get a little ‘nervous’!

I let Porter suggest the tubing thickness as he had some strong opinions in this area. As I weigh 250lbs (113kg) we ruled out using butted tubing as it might flex too much. He recommended using 1.55mm wall thickness for the chainstays, 1.3mm for the seatstays and 0.9mm for the other main tubes.
I designed an intricate logo to be engraved on the head tube. Porter said he didn’t think he could do the elaborate English font. I asked him to please try to which he replied “OK, we will try”! He sent me a picture and it was perfect!
I panicked at the last minute thinking my huge winter SPD boots would rub the chainstay, so he actually put my boot, in CAD with 5 degree float, I was very impressed!
He did the same when I was looking for confirmation about clearance for a 180mm brake rotor, again no problem; he put it on the CAD plan!
They finished the frame and sent me a pic. It looked perfect but unfortunately the Chinese New Year massively delayed shipping.

The finely detailed headtube engraving turned out really well.

Chinese New Year, ‘Tomb Sweeping Day’ (really); you discover a lot about different cultures when you place an order overseas! Now for the exciting bit:

A month later I got the frame; the box was crushed and looked like it had received a soaking at some point too. Luckily the frame was in so much bubble wrap that they could have probably sent it without the box and it would have been fine!
The frame quality and welds were fantastic. I also negotiated in a CNC seat clamp which looked great too.
I began assembly and quickly realised the rear thru axle threads where 1mm x 12 and not the more common 1.5 x 12. My mistake, I should have noticed this. No big deal, I ordered a $30 thru axle from Paragon and it arrived the next day.

Something I’d not known about until recently too – not all thru axles are created equal! Don’t you just love ‘standards’?

The frame is not light, again this is my fault for constantly insisting it is a stiff tank that can take the abuse I will subject it to. It is over 6 pounds. I was a bit disappointed by this, but really if I tweaked everything and used double butted tubing I might get it to 5 pounds in such a huge size so on a 290 pound combo of bike rider and equipment, how much difference does one pound make?

It’s a fair point, well put into perspective by Michael there. Given the size of the frame and the intended use I’m not surprised it’s a 6lb’er. I’d have probably suggested 1.2mm wall thickness tubing for the chainstays and maybe the downtube but the rest of the bike should have been fine with standard 0.9mm. He’s going to be able to put 100% trust in his current frame though which is the important thing!

I built it up in a few hours as everything went together perfectly. The T47 Wheels Manufacturing BB threaded in smoothly. The tapered headset went in fine, the headtube was perfectly faced with no distortion.
I took it for a ride. It is perfect! The geometry is similar to a trail bike so I’ve kept it long, low and slack. It’s super stable at speed and so stiff. There was literally nothing I could do to get the bottom bracket or rear triangle to flex, it’s as if the drivetrain was bolted to a foot thick aluminium plate!
The head tube runs at 67.7 degrees. I think this may have been overkill, I might go 68 next time, but really I am just trying to find fault!

Chain, tyre, boots – there is room for everything!

Sounds like a job well done to me – 67.7 degrees? If you’re going for an odd number why not make it 66.6? 😉 To be fair 68 degrees isn’t that slack these days, I’d cheerly run somewhere between 63-66 degrees on a ‘trail hardtail’.

I am using a Lauf suspension fork which is basically for the bling factor. It does smooth out the ride at speed and takes the edge off bigger hits, but in the end it does only have 1.5 inches of fairly undamped travel. Whatever though! It is super cool looking, needs no maintenance, runs stiction free and is immune to the cold weather!

Now, don’t get me started on Lauf forks and their crimes against general engineering principles…

So in the end I am 100 percent happy! People give Porter a bad rap but I look at it like this; would you rather be coddled by someone who might not be straight with you, or deal with someone who really knows their stuff but might not be so tactful?
I found you need to communicate with him a certain way, just make everything plain and don’t worry about small talk. Eg. “Change headtube from 180mm to 190mm” etc. If you make a mistake he will reply “No your words are wrong!!”. I learnt not to be offended by this as each time he said it he turned out to be right! So, whatever, if you can’t handle this maybe XACD isn’t for you!

One thing to note on the design front – don’t get too hung up on getting those chainstays as short as they can be, especially on a larger frame. Current thinking looks to place the rider more centrally between the wheels for a better balance.

A long seatpost extension is also going to put the rider’s weight further back so look at using a slightly steeper seat angle to compensate for that.

Looking at the size of the stem and handlebar on his bike Michel could have even added another 20mm to the headtube and top tube lengths (and perhaps the chainstays!). We’re seeing a trend now for bikes to get bigger and longer, originally this was to give them better downhill handling but as a side benefit taller riders like Michael are finally finding frames that fit them!

So, another happy customer, Micheal had a good idea of what he was looking for and was able to find someone to work with in Porter to sort out his ‘dream’ frame. Even now, a few months down the line, he’s struggling to think what he would do differently next time – which is a very good sign! He might also have another little project in the pipeline…

Anymore for anymore? Do drop me a line via the contacts page and let us all take a look, thanks!