Towards the end of 2013, Laura asked me to build a custom steel mountain bike for her. Laura wanted a special memento of her time here in South Africa – a bike to remind her of the Cape’s unique off-road riding when she returns to her home country: France.
The brief was relatively simple: Laura wanted a capable, all-rounder mountain bike. She wanted to be able to run longer travel forks but specified that the bike would need to be based around standard 26 inch wheels. Laura is not tall. She’s not exceptionally short either, but large wheels would definitely pose stand-over problems for her – her decision to stick with 26 inch wheels may seem retrogrouchy but while new wheel-size-fever grips and maims the wallets of the cycling populace, the old standard is unlikely to disappear completely and old stock abounds.
Laura wanted the ride comfort that’s usually associated with good steel frames but she also wanted the bike to be as light as sensibly possible. She didn’t want to fuss with brake adapters – she was keen on post mounts for the rear brake and her European sensibilities called for traditional down tube cable routing. She also wanted a stainless steel head-badge.
The rest was up to me.
After taking some basic measurements I’d worked out a plausible design. One of the biggest challenges in designing small frames is to get the stack height low enough – this in turn not only affects the stand-over height but it also affects weight distribution. Many smaller bikes have overlong head tubes that push the bars well above saddle height – this is most noticeable on bigger wheeled bikes. This tends to push the rider’s weight back and onto the saddle. Women also tend to have a shorter reach than men. Conventional small bikes often have very steep seat angles to effectively shorten the top tube and thus shorten the reach. The wheel base is usually untouched and can result in a bike that’s very difficult to maneuver over obstacles as the rider is unable to use her weight effectively to loft the front end.
In designing Laura’s bike I decided to use a very short (100mm) 44mm diameter head-tube. This allows for a semi integrated upper headset bearing which in turn helps to lower the bars a smidgen. The top tube was given an aggressive slope for added stand-over clearance and the chainstays were made shorter than usual to help with weight distribution. I gave the frame a lower-than-normal bottom bracket since Laura will ideally end up riding 165mm cranks instead of 170 -175mm standard offerings.
I chose a combination of Columbus Zona and Life tubing for the frame. The down tube is a standard oversized 35mm Life tube – this has thinner walls than the Zona tubing and is constructed of a finer grain of alloy (it’s also more expensive). For the top tube I decided to stick with a Zona road oversized tube – this is a thinner diameter than a standard mountain bike top tube but I felt that it would help to accentuate the ‘feel of steel’ that Laura so coveted. The seat stays were also ordered in a thinner than normal guage and a sinuous s-bend to help dissipate bumps in the rear. I gave the bike a relatively slack head angle of 68 degrees with a 140mm fork at 30% sag – this should ensure that the frame can run anything between 100 – 140mm of travel upfront without becoming a barge.
The frame dimensions correspond roughly to a 14″ standard MTB. This meant using a very short seat tube. I was concerned that since I was removing the butted section of the seat tube it may be weaker than intended: to add some extra reinforcement at the BB junction I created a carved sleeve to strengthen the join.
Most of my frames sport chainstay gussets. By using gussets I can do away with the usual chainstay brace which limits mud clearance especially on small frames. I also think it just looks better. I drilled some holes in the seat tube sleeve and added similar details to the gussets. The drilled holes echo the relieved design of the dropouts – I was very pleased with the final result.
Before long, Laura’s new frame was nearing completion. The seat stays were added after checking the rear alignment and just a few finishing touches remained to be added. There was still one thing missing – Laura’s bike needed a name.
Soon the little frame was being fussed over by Jared at BMC as he applied one of his famous coats of paint. Laura had chosen a base of sunset orange and a complimentary blood red for the highlights. Jared polished the stainless head tube badge until I could see my reflection in it and then he performed his magic.
The frame back from Jared’s booth resplendent in it’s new colours – I spent a day building it up and then it was time to introduce it to Laura. Laura wasted no time in putting her bike through it’s paces and when next I saw her, her little bike was proudly wearing some fresh Table Mountain Dirt.
And the name?
Before paint Laura finally decided on “Bokkie”. A bokkie in South Africa means a little buck. It’s also used to refer to one’s sweetheart and in Cape gang culture it can be a deadly juvenile assassin.
I hope this Bokkie lives up to it’s name.