Have you placed your credit card at a safe distance away from your current position? Then you may be safe to read on. Custom, titanium, BMX, EXT, DH, Ted James, single speed… no, this is not bike fetish bingo, this is the ‘Ti Bride’, as it has been christened by its owner. Its builder, legendary British frame builder Ted James, talks us through the design and build.
This is a one off custom build for a customer who wanted a single speed downhill bike in titanium with the simplicity of a BMX and no flappy chain, hence the Jack Drive.
The customer is a BMXer and had one a few years ago from me but also rides a Nicolai trail bike which he does a lot of bike park uplifts with. He wanted something like a big BMX , singlespeed and strong, he’s broken a lot of bikes in the past and has the slogan on his top cap ‘monster truck everything’, ha ha!
Ted James
The Jack Drive with two chains running on cogs concentric with the pivot means there’s no chain growth and therefore no need for any kind of sprung tensioner. We have an eccentric BB to tension the first chain from cranks to idler. Ted decided to go for a simple solid type with pinch bolts in the frame to lock position.
The customer wanted to run BMX cranks and after a lot of consideration the best thing was to machine it all myself to get the necessary requirements and I also made the cranks with Reynolds 853 tubing.
Ted James
Don’t you just love it when the simplest thing is just to make it all from scratch? Oh to have those skills.
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You could just say it’s tensioned with a unique horizontal bolt though dropout. But where’s the fun in that? Let’s have more details…
The second chain from idler to rear wheel is tensioned with a horizontal dropout but with bolt through axle. It’s an enclosed 12mm axle slot in the dropout with the 3.5mm recess milled into the inside face to support the wheel. We then have a sliding disk mount and threaded piece for the drive side for the axle to bolt into. Both sides have a tensioner bolt to help set chain tension and wheel alignment. The plates bolt in place and keep the position for removing and re-fitting the wheel.
Ted James
The idler Ted also made, as a spider to use bolt on replaceable cogs (old school granny rings) which can sit offset to help chain clearance with each other.
Ted says the the geometry is pretty long and low as you’d expect from a downhill bike these days. He made comparisons to others on the market and sized it from the customer’s current Nikolai trail bike. The rear shock is custom built by Mojo suspension, who from the start gave Ted ratio values to aim towards with the design. They built an EXT Arma mx 250×67.5 with 5mm negative spring.
Neither of us [Ted nor the customer] have too much knowledge on dampening so working with Mojo and Elro from the start was perfect. My main thoughts were to avoid issues often associated with suspension bikes such as pivot/ bearing housing ovalisation, premature bearing wear , difficult to service pivots and flex.
I used the linkage program to position the pivot, wheel, shock and mounts whilst keeping to the ratios suggested by Marcel at Mojo for the shock. This was a challenge within the space and with thoughts on where and how the pivot and downtube shock mount would fit.
I didn’t want the shock pushing too side-on to the downtube, and kept the force directed along it a bit. I added a gusset under the mount to help spread the load.
For the main pivot, I knew if it was only mounted to the seat tube it would really have a lot of flex so I positioned it so I could mount it braced across both seat and downtube. I thought about additional gusseting but just went for very thick walls on the mounting tube to keep it tidy and fewer places for mud build up.
Ted James
The main pivot uses quite a chunky bearing, same as a Spanish BB, and double bearings each side. There’s a lot to consider with fits of bearing in the frame and to pivot axle etc, again I machined all the various parts to get it how I wanted to minimise the potential for any play to occur.
Even with a relatively simple single pivot design there was so much to think about and consider to make every part as durable and best it could be.
Titanium, although high strength, is more flexible than steel so I chose large diameter tubes and thicker walls than I’ve ever used before. I thought about having an upper link keeping more stiffness and alignment to minimise any side loading to the shock but was keen to not add more parts and bearings, and the spherical eyelets [on the EXT shock] allow for movement there rather than the shock taking the twist.
To keep rear end stiffness I went with 7/8” diameter all round. For the pivot I opted for bearings in the swing arm rather than the frame to keep them wide apart for less loading on the bearings, but also used beefy bearings and two each side. This style can be tricky to drift out when replacing so I went for a slightly easier fit and a cinch bolt with partial slot to nip them in place but not overload them, which a full split clamp style can do.
Ted James
- Fork is Formula Nero C from Paul at Elro distribution, who also gave help and advice on the setup and getting the bike properly balanced.
- The wheels are Enve M930 rear rim, front 730, on Profile Elite hubs to keep it BMX – Ted says there’s also not much choice for a boost single speed rear hub.
- Chris King Dropset headset, Hopetech 4 -pot brakes and pedals, Renthal carbon bars and Schwalbe Magic Mary tyres
- Overall weight of just over 17.5kg
If that’s got you all of a froth and wondering whether you might just need something similar, how much would this cost you? Ted says that when he was asked about building it initially he thought I’d turn it down but then realised a few parts of the design would help him get closer to his own build plans for a full suspension gearbox bike. He quoted £4,000-£4,500 for the frame only. For something titanium, bespoke and complex that doesn’t sound like that much too our ears – and indeed it doesn’t really cover the true cost. After building it he now realises that nowhere near covered the time he spent on it ‘but it’s so tricky when it’s a first and was quite a learning experience’.
Full suspension gearbox bike you say? We look forward to seeing that. Or, form an orderly queue and get in touch with Ted to see if he’ll make your own bespoke bike dreams come true.
