Dan?..... Dan? Are you there, Dan?
Right here, Peter!
To see what effect changes in trail can have on handling (specific to my late Sherpa, but the same principles wrt to trail apply to other frame/fork/tire combinations as well), see my article titled "Sherpa handling, Sherpa hacking, and a little bicycle science" here:
http://www.thorncycles.co.uk/forums/index.php?topic=4245.0- - - - - - -
Looking at the SJS Cycles website, I see the older (discontinued) Club Tour forks are available in rakes of 50mm and 55mm; I don't see them in current stock. See:
http://www.sjscycles.co.uk/page/find/?name=Thorn%20club%20tour%20fork&page=1I see the standard Audax Mk3 forks (matte black; sizes are more limited in other colors) are available in rakes of 43, 46, 50, and 55mm. See:
http://www.sjscycles.co.uk/thorn-audax-mk3-1-1-8-inch-ahead-steel-fork-matt-black-prod27193/ Depending on your current Club Tour rake, I would expect an Audax fork of the
same rake to
handle much the same as your present CT fork. Changing to a different rake would change trail and therefore your bicycle's handling.
Please note, the forks referenced above are
the standard-issue ones. According to the Audax brochure (
http://www.sjscycles.com/thornpdf/Thorn_Audax_Mk3.pdf pg.4), there are
two optional forks. One is an 853c, described by Andy Blance thusly...
Reynolds made the 853c blades and lightweight 853 steerer especially for us Reynolds even made the tooling for the tight-radius bend that I’d requested. These are a premium product offered at a premium price.
853c forks, with a 46mm offset, are suitable for [Audax Mk3] sizes 525, 550, 570 and 600, they’re available in Matt Black, Blue, Red and Gunmetal Imron. 853c forks, with a 52mm offset, suitable for sizes 495S and 555S are only available in Matt Black or Gunmetal.
NOTE 853c forks allow direct fitting of mudguards but they don’t have lo-loader bosses. As reliable as they are, you must never try to fit a front carrier to them. The tight-radius bends flex beautifully and I didn’t want a mudguard boss brazed on the bend, therefore we recommend that you use an SKS Secu clip. Max tyre size with mudguards 28c.
Weight 805g with steerer cut to 300mm. (Steerer weighs 0.71g per mm and is 380mm at full length). 2 x 5mm bosses for the direct mounting of mudguards.
There is a second optional fork made of carbon fiber which Andy Blance describes this way...
We have a carbon fork available, which works well with the geometry of all the Mk3 frame sizes, apart from sizes 495S and 555S.
This carbon fork can save up to 400g* We are in two minds about recommending a carbon fork because the trouble with carbon is that you can’t necessarily see when it has been damaged by an impact. (* Depending upon steerer length.)
We’d only advise you to choose the carbon fork upgrade, if you never lend the bike to anybody and if you’re also prepared to destroy and dispose of the carbon fork responsibly, if it’s ever subjected to an impact.
Peter, your question is much the same one jags asked when he was pondering a carbon fork in hopes of making his Sherpa lighter and more lively.
It is my feeling a carbon or lightweight steel fork *in the same rake* will make a bike lighter overall and can often change the *feel* of the bike by being more flexible or by having better shock-damping characteristics or a tighter bend for the same rake, but so long as the actual rake is identical to your present fork, the *handling* should remain the same. If you change the fork rake and keep the frame's same head angle, then you are effectively changing trail, and that
would affect handling.
I would suggest contacting SJS Cycles/Thorn and asking this same question. They really are very good at providing solid answers, and Andy Blance is surprisingly available to give the Designer's Word on what will work or not, either directly or through staff via their email responses to queries.
If you are curious as to how a fork with
different rake *might* affect your bike's handling, you must first accurately determine your head tube angle and the rake of your current fork. From these, you can determine your current trail using one of the online trail calculators references at my "Sherpa handling, Sherpa hacking" link above. You can then plug-in the rake of the fork(s) you are considering and the calculator will spit out the trail of that new combo for comparison to your present fork/frame trail. You can then check the result against my trail-based handling descriptions in that same article for a prediction of how your bike might be expected to ride with the new fork.
A number of people ask me the same question each year, and most have found the proven course to making a heavier bike feel both faster and more lively is to fit it with a pair of lighter wheels and tires. The reduced rotating mass at the outside of the wheel will accelerate faster and will feel (and be) more responsive. Often, lighter tires are also narrower. Given the common near-1:1 height/width profile of bike tires, those same narrow tires will affect handling a bit also by being lower, typically resulting in less trail. If you're used to running your Club Tour on wider/higher profile tires, you can make it more stable and resistant to rider input at lower speeds and a bit less stable/more vague at high speeds by switching to narrower/lower tires (most suitable when riding unladen on good roads).
A heavier, touring-oriented bike can be made lighter and/or more lively in feel to a degree by changing the fork or wheels/tires, but there is ultimately only so much you can do as the die has been cast with frame geometry, materials, and tube diameter and wall thickness; it will still be a touring bike at heart, rather than a true Audax bike. That said, my Audax (randonneur) bicycle started life as a tourer, and with the addition of fairly light but very strong wheels (Mavic 20.3mm MA-2 rims, Phil Wood hubs, 36-1.8mm spokes, lightweight tubes and 32mm road slicks), has become my favorite all-'rounder and long-distance day-rider, carrying me comfortably on mountainous 400K day rides and snaps off 300K runs like clockwork, never leaving me feeling achey or beat-up afterwards. I can tour on very rough gravel roads with a pretty reasonable maximum load of 25kg and come out fine.
It might be worth borrowing a set of lighter wheels/tubes/tires to try on your Club Tour to see how much difference it makes for Audax rides.
I hope this helps.
All the best,
Dan.
