Folding Bikes - Brompton & 406mm wheels

The more I look at the Brompton, the more impressed I am with it just based on the folded package.

As I'll be touring in rural Canada, the 349mm wheels aren't an option.

Before you say, "no, this isn't possible", can anyone think of a way to convert a Brompton to 406mm wheels?

The difference between a 349 and 406 is only 57mm total. Call that 3cm added to the radius.

Would that 3cm of extra wheel/tire interfere with ANYTHING on a Brompton - any part of the frame, folded or unfolded? Maybe there's some kind of bridge between the chain stays that's too close?

I wouldn't be riding with fenders so that's one less thing to worry about.
I imagine a front fork swap might be needed. Does the Brompton take standard forks?

If I had access to a Brompton, I'd be able to figure it out but there don't seem to be any locally. :\

Thanks all,
Chris

If the bike is geared right for the tire size, what difference does it make? I'll bet you can get 16" tires almost anywhere, they're used on a lot of bike trailers and jogging prams, or just bring a spare with.

I wouldn't say it's impossible, but I think you'd have to make too many mods to use 406mm wheels. You'd have to get a longer fork and a larger rear triangle. You'd have to make sure that when folded, the seatpost would be able to clear the folded rear tire (this is what "locks" the fold, kind of like what the Swift does). Then you'd have to make sure the wheels could fold and tuck under the main frame monotube, so you might have to adjust the main frame by creating a longer, curvier main frame. More trouble than it's worth, imo.

I wouldn't say it's impossible, but I think you'd have to make too many mods to use 406mm wheels.

You'd have to get a longer fork and a larger rear triangle. You'd have to make sure that when folded, the seatpost would be able to clear the folded rear tire (this is what "locks" the fold, kind of like what the Swift does). Then you'd have to make sure the wheels could fold and tuck under the main frame monotube, so you might have to adjust the main frame by creating a longer, curvier main frame. More trouble than it's worth, imo.

A new front fork makes sense.

Do we know it would require a new rear triangle though? Case in point: the KHS Cappucino folding bike comes with 18" wheels. It will fit 20" wheels however - measured and confirmed.

Again, I see how the rear wheel could interfere but I think it would take some measurements or testing to figure this out definitively.

FWIW, the 20" wheel on my bike, with a 20x1.5 tire installed, measures 490mm in diameter including the inflated tire at 100psi. :)

Cheers,
Chris

There's only one person who would even attempt this type of work and he lives in England. From what I know, he never attempted a job such as this and for probably good reason. You would have to rebuild a new rear wheel, new brakes, new rear triangle etc.

I suspect the cost of all these mods (even if they could be done) would cost about as much as a new folder. Are you intending to board many buses every day in this trip? If you don't have to board a bus two or three times a day, then convert your KHS into a multigeard bike using the SRAM Dual Drive.

The folding package is only important if you are touring with buses having to board one each day. If this is not the case, then low gears and comfort are your primary concerns.

Dahon.Steve,

Indeed, anytime I ride my bike in winter, it involves taking a bus, hence the look toward the Brompton but with 406's.

The KHS is fine in all aspects (16-speed, wide gearing, comfortable) but the smaller package of the Brompton would be helpful.

:)

Would that 3cm of extra wheel/tire interfere with ANYTHING on a Brompton - any part of the frame, folded or

Don't forget about if the brake pads will have enough adjustability to hit the rims, ie. 700c wheels often fit in a mountain frame, but the brakes won't reach.

There's only one person who would even attempt this type of work and he lives in England. From what I know, he never attempted a job such as this and for probably good reason. You would have to rebuild a new rear wheel, new brakes, new rear triangle etc.

.
His name is Steve Parry, he specialises in souping up Bromptons.

I think you would be able to solve the brake issue. Paul Components makes a V-brake arm that gives you a huge adjustability, made for putting 700c wheels in 26" frames. So 3cm of movement should be a cinch. Good Luck I am sure you could do it, but I don't know about the effect on the folding of the bike.

For 3 times already I have "upgraded" hold bicycles 24 inch wheel x 1 3/8 to 26 x 1.something but the distance between the sizes is not that wide (6 mm radius)

http://www.sheldonbrown.com/tire-sizing.html

Once I repaced an 18 inch by a 20 inch in a children bicycle and it fitted ok, but mudgard had to be removed and caliper replaced. With this bicycle's frame I am building a velocar.

Now, replacing a 16 wheel by a 20, I think you need to remove mudgard, and try to fit the wheel in the original Brompton's frame. Try diferent tires and probably, just probably you will be lucky.

Impossible to fit 406 wheels in a Brompton IMHO. There is less than 10mm clearance (down to zero) at several points around the rear wheel when folded. If you are stuck on using big wheels, start with another bike.