Replace 650c front wheel/fork on funny bike with 700c?
 

I recently put together a very sweet street-fixie from a TT "funny bike" frame. It came with a 650c tubular front wheel and fork etc. The tire installed was, admittedly, old and worn and I wondered just how much life it might have left with a bit of tread totally sheared off of one side....

So this morning it got a flat in a rather unspectacular manner (I didn't even notice it until I was on the train). Now I'm wondering if riding a tubular, 650c front tire on the street isn't asking for trouble just due to scarcity and the apparent fragility of tubulars.

My tire of choice on the rear of this bike and on my other 700c bikes has been Rubinos of late- they seem quite flat resistant, cheap, etc. I cringe a little at the thought of the rear tire being a no-brainer and gingerly dodging tiny glass shards in the gutter with the front.

So my questions are thus: can one replace a front fork with one of a different tire diameter (650c to 700c) without throwing geometry and handling totally out of whack? Would I be better off simply sourcing a new 650c clincher front wheel? Are there tubulars out there that aren't too pricey that can be counted on for flat resistance (within reason), or are they all a little milquetoast?

Bummer, really, I love the feel of that front wheel.. The fork is really sweet, too.

Oh yes, and who has really good prices on tubulars, in case I decide to stay the course?

Thanks,
rcc

I have been using tubulars for over 15 years. My very well considered opinion is that it is a bad idea to try to ride them daily. Especially in the rain, they catch flats all too often. I still race on them because the wheels are lighter, the tires grip better, and they are more responsive. By using Tufos with the sealant, you can minimize flats. www.worldclasscycles.com is a good source.

You cannot simply change the fork without disturbing the handling of the bike. Don't do it, it would at best ruin it, at worse be grossly unsafe. You could try to find a 650C clincher, I'm sure that they are out there. That is what I would recommend.

depends on what you mean by "totally out of whack" i've never done it so i can't really say how it would feel... but it will definately give it a relaxed geometry. what i would do personally is go to an LBS, borrow some old 700c fork and tire they have sitting around and put it on, see how it looks, feels. then you'll know for sure...

650c is still a fairly common rim size. i know mavic and velocity both make a few 650c versions of their other clinchers. i think you should leave the frame and fork as it is, and have a new 650c clincher rim laced up to your existing hub. 650c clincher tires aren't that big of a pain to find either... front wheels are the easiest to build, so this could also be your first wheel build... or you can also always check ebay for a used front wheel as well. consider yourself lucky you don't have one of the weirder sized pursuit/tt front wheels.

putting a taller fork on that frame will slack the headtube angle out too much, aside from how weird it would look, i think it's a bad idea...

just get a 650c clincher and re-lace the hub to it.

Sounds like a plan, all. Haha, wheelbuilding, here I come! The stock wheel is this fruity radial-laced bladed-spoke mavic thing with an ambrosio rim.. I'm not sure if I should keep that pattern/spoke type around or just get create a new front wheel altogether.

650cc Velocity deep-v clincher. What kind of frame is it? Sounds awesome. Post some pics when you get an opportunity.

it can cause problems to re-lace a hub using a different lacing pattern...

TT and tri bikes use 650C fronts [and sometimes rears] all the time. You should be able to buy a 650C wheel easily, and Vittoria makes a 650x23C Rubino Pro as well. So do Michelin, Conti and most road tire mfgrs.

I switched from a 24" front to a 650c without too much problem. Then again, with 24", it was REALLY REALLY REALLY steep, so now it's just pretty darn steep.

As for tubs, a lot of people ride them daily without problems. It depends on how handy you are with a sewing kit. You didn't notice you had a flat because unlike a clincher, you can ride a flat tubular all the way home without incident. Furthermore, if you carry around a spare tubular, you can mount a new one faster than you would change a tube on a clincher. Also, just as you don't throw away the whole tire when you get a flat on a clincher, you don't throw away the whole tire when you get a flat on a tub. You can buy repair kits from most decent bike shops (basically, big needle, dental floss thread, and some tube patch stuff). It's actually kind of fun repairing them. Here's a link to the instructions:

http://www.yellowjersey.org/tubfix.html

As for changing the fork, I'll trade you a regular road conversion with 2 700c wheels for your funny bike.

As an aside, I don't think you can use the Tufo tire sealant with anything other than Tufo tires. The downside to Tufos on the street is that you can't repair them using traditional means.

If only there was a viable method to swap wheels over the pond :( . I would love to get your Mavic/ Ambrosio wheel for equally good and light Mavic Open 4CD(rim)/Campy C-record(hub) 650c clincher.

That way I could restore my Gianni Motta TT funny bike to its original state.

I 2nd the idea to try the 700c fork/wheel. Just borrow a set and see how it works out. Yea, the ride may suddenly turn to complete crap, but it may also give you some angles that just work out killer for you.

Did this over the past weekend, pics to follow.

Let me say this, generalizations are just that. Much will depend on the original geometry and the type of fork and offset of said fork.

While I didn't check the change of the angle of the headtube pre-install, the seattube went from a 73.5 with the 650C to a 72.5 degree with the 700C in place. So, if the frame is a typical "square" frame, the headtube will change acordingly.

The Bike: Marinoni TT set up as fixie.

The Ride: With 650C in place, it is the typical TT bike ride. Twitchy when you stand or climb. With the 700C, the ride and handling is like my road bike with a much more aggressive position. Climbing, sprinting, no-handed riding are all very stable.

At this point, I've got about 50 miles on the bike and will give the final verdict in about another 50.

As to the question of why, I simply had a straight blade 700C fork and an extra headset (orginal fork was threaded, alternate was threadless) and the 'what-if' question had been on my mind as of late.

26" tubulars go for next to nothing when they show up on ebay. i've never paid more than $10. continental sprinters seem to do the trick nicely.

holy thread rez batman, i just totally found the 'noni on ebay !
http://www.ebay.com/sch/gillamonster...p2047675.l2562

****

Def gonna have a nightmare because of this.

:thumb:

Yeah this is going no where.