I've been testing the prototype spitfire for a few months now, and figured that it was time to post up all the small tweaks and changes that I am making to the frame for production.
I have really enjoyed riding the spitfire this summer, partly because it was just great to get back on a bike again after surgery, but also because the spitfire kind of took me back to my roots of riding. When I was around14-15 I took my first real biking trip with a couple of mates up into the highlands of Scotland. I was on a full ridged back then that probably weighed significantly more than my spitfire, and was nowhere near as much fun. Over last 6-8 years I've been doing mainly free ride/ DH / DJ riding, so felt great to get back out in to the hills and enjoy the scenery with mates.
The blue points at the rear axle show the top out and bottom out positions for both geometry settings.
The spitfire has been the perfect bike to do this on, as it just makes climbing easy, and kills fast singletrack descents! I've really pushed the bike beyond what it is designed for to make sure that it is up to the challenge, and it has just shrugged everything off so far, and coped well with a whole variety of terrain. But the prototype was not perfect, It didn't quite feel the way I wanted it to despite getting close with some changes to suspension components etc. So I went back to the drawing board, and started altering it to further improve feel and performance. I also received a lot of help with ideas and suggestions from many a member of the bike community. I would like to thank everyone who has contributed to the design by throwing in ideas and suggestions. (A special shout out goes to the guys who have been actively contributing to the Spitfire thread on the mtbr forum, you guys got me considering options again, and pushed me to achieve the final version of the Spitfire.)
All changes have been made to improve performance and build options for riders, whilst taking into account strength, stiffness, weight and aesthetics. So what are the major changes to the Spitfire for production?
- I dialed in the suspension linkage to work better with 2010 shock options. The proto felt slightly dead due to leverage curve shape. So I made the rate of leverage ratio change a bit more gradual, and a touch more progressive throughout, whilst adjusting the subtle pedal platform to be a little bit further into the travel.
- The proto had an issue fitting some front derailleurs at bottom out, which was a stupid oversight on my part, so I fixed that, as well as making the axle path slightly more rearward to help the bike soak up harsh square edge bumps, as well as marginally increasing antisquat in early part of travel.
- The production Spitfire will have a tapered head tube (ZeroStack 1 1/8" top and traditional 1.5" bottom). This was not done for strength reasons, as there really is not improvement in strength no matter what you read (Unless you use massively wide tubes like new giants, where you can achieve a little bit more weld area, although I've achieved this with the hydroformed shape). There were 2 main reasons why I finally made this decision. Firstly, for 2010 nearly all single crown forks from major manufacturers will be offered with tapered steerers. And secondly, If people want to run a larger 160mm fork they can do if they have a straight 1 1/8" steerer, and a zero stack lower cup on the headset, whilst not throwing out the geometry. It also means that you can choose between zero stack and external bearing bottom race for different forks to fine tune your angles and BB height.
- Head angle has been slackened very slightly. It would seem that a lot of people have been waiting for a short travel, light weight, slack bike, and who am I to disappoint them?
- I've slackened the seat angle by 0.5 degrees to better suit riders who are running shorter a2c forks, but will still offer a great angle for those with larger travel forks. This also makes the front end slightly shorter. (My large proto felt a tad long for me 6'2" with a 70mm stem)
- Geometry adjust is still there, but now I have slightly increased range of adjustment to 1.1degrees... yeah, OK not a big increase, but I felt I just wanted that tiny bit more while testing.
- I increased the tire clearance. I haven't actually had any issues with my prototype, but just wanted to offer that bit more room for when the mud is gloopy.
- I changed the shock bolts to 8mm diameter from 6mm. I think the strength gain is worth the weight gain.
- The down tube shock mounts are a bit more splayed to further spread the load (again this shouldn't really be necessary, but I'd rather be safe than sorry).
- The cable guides on the rear triangle have been switched to run underneath the seat stays, just to keep a cleaner look.
- Added a brace between the downtube and the BB to help dissipate stress concentrations at this location. (again probably a little over the top, but worth the extra few grams I feel). I realise that a lot of people want this bike as a really aggressive trail bike, so I would rather make it overly strong than not strong enough.
- Weight should stay around the same, I've saved material in some places and added slightly to others. My large prototype frame weighed in at 6.52lbs with shock seatpost clamp and all hardwear.
Thanks again to everyone who e-mailed me their thoughts or contributed to discussions. I have taken everything on board and tried me best to follow the general consensus.
The spitfire will be available in early 2010, stay tuned to the blog for more details on colour and build options, and costs, and confirmed weights closer to the time.