61.62 km per hour (38 mph).

Comparatively I may be the slow kid on the block compared to many of you but 60 k + felt pretty freaking fast to me today.

Did it on the Dahon Speed P8 and right when I saw the computer hit 60 km the front wheel started with the tiniest bit of wobble.

I betcha lunch I could have tucked early on and squeezed a few more kph out of that run. I backed off when I felt the wobble.

Anyway it was a blast and me and this hill have some business with my Dahon Speed TT.

Don't read too much into the numbers. I don't carry my GPS on every ride. Only new routes. When I first bought it I wanted to record every bike mile but the fact is its a PITA to set it up for each bike, especially when I'm just running to the store for milk or something.

John

Now try holding that speed and more while cornering on a mountain......SWEET

Well done... the max I did on my Speed Pro is only abt 63km/h and though the bike still had gears left, I didnt!

My max was 65kmh on my Dahon. I was scared ****less. LOL

Wow - Having gears left at that speed is amazing to me. Today, I ran out of gearing downhill at only 46 Kmh.

The Speed Pro has a gear range of 124 inches... compared to the usual 80-90 inches for a normal 8 speed folder. But you do need the strength to exploit that

I don't have a computer on my Birdy, but two weeks ago on the way back from a camping trip I rode past one of those roadside speed traps that said "Your speed is 36 mph". The bike would happily have gone faster, but it was a rather bumpy & twisty downhill so I was braking a fair bit. The bike still felt solid and confidence inspiring at that speed, even with a full touring set up.

[I am deliberately resurrecting this zombie thread so this data is in one place. Are any of the folks still here?]

I hit 38.8mph (62.4km/h) on the Pocket Rocket today. Long downhill, fully tucked. Felt super stable. I must be getting old though because I feathered the brakes a couple of times.

Next time, I'll shoot for 40mph.

I managed 37mph on my Helix on a steep downhill last November. I should know better at my age but I still love to go as fast as I can whenever I manage to delude myself that it's safe to do so. What is it that makes us want to go as fast as possible? Does it go back to sibling rivalry?

I have a similar experience with my Bike Friday All-day: its also very stable and allow very high speed, downhill and on flat roads too.

From my several folding bikes, its the most stable one: the Brompton 1" is the worst, the Birdy is pretty good but I never reached as high speed as with the All-day. My Moulton Speed is as good as the All-day but its not a folding bike!

What is also excellent with the All-day is that its very agile, it allow to take fast very sharp curves.

Over 25 mph is too fast for me on 20" and smaller wheels!

I'd feel more comfy on a BF at those speeds.

Bifold... not so much.

I used to reach speeds of up to 57 kph routinely on my minivelo; it is more stable than the Helios (I can't quite remember how fast I went during COVID).

With 40 cm gravel handlebars, it felt fine, although I would run out of gear with the 60x11 or 69x11 setups. However, after making the switch to a time trial (TT) setup with a 38 mm bar and a longer stem, it doesn't feel as controllable. Interestingly, while using the clip-on TT bars, the bike feels stable, but it’s not ideal for making quick evasive maneuvers.

I haven't hit anywhere near that fast on my Dahon Speed; Top gear is only 85 gear inches, can't pedal down fast hill. Feels inherently less stable, I hold the bars firm. No wobble if I stay seated or seat clamped between thighs if standing to create drag, off seat and it can wobble. I'll brake before fast turns, that's what wears my brakes and rim sidewalls, why I want discs, plus for rain.

On my 700C racer, crit geometry but felt rock solid at speed, on a mild downhill, long, straight, I topped out the computer at 64 or 65 kph. Original Scott clip-on time trial bars. That Cannondale frame was very torsionally rigid, I think that's why I never felt anything approaching speed wobble, I was ignorant of that then.

I just looked at my data on this same descent from 2014 on what I think was my 650c Serotta - max speed 40.5mph (65.2kph). So ~1.7mph faster on a bigger-wheeled bike.

This confirms what I've been thinking, smaller-wheeled bikes don't descend as quickly. Is the reduced rotational inertia? Or something with the aerodynamics of smaller wheels spinning faster? Frictional losses in the faster-spinning bearings?

I think I hit 36mph downhill on the 20-inch Dahon Boardwalk (11-38 with the stock 52 ring upfront). With the stock straight bars it was a little squirrelly. With the bull-bars and more of a road bike riding position it is more stable.

On my bodgey 16" Dahon Getaway V (now a 7-speed with 11/28 back and 60 teeth upfront) I have flirted with 30mph but it does not inspire confidence above 24mph.

I've done 41 mph (66 kph) on my stock Brompton (S type) and found it quite stable. That was down the Laguna Seca corkscrew during the Brompton World Championships, which was loads of fun, but have hit similar speeds on regular roads too. There are enough potential wiggly bits in any folding bike though that one may handle differently than another.

That's a wild speed! I've been on the Corkscrew; I'd be surprised if you can hit that speed there. How did you measure? If GPS, if the data interval is too long, it could straighten out the Corkscrew out and report a higher than expected speed

But if that's a legit speed on a 15" Brommie, wow!

I've only recently learned that smaller wheels and tires are less efficient overall even with the aerodynamic bonus.

I think it's due to the contact patch.
The smaller the diameter, the shorter distance the contact pressure increases over a specific distance.
(Smaller tire, less eccentric the oval shaped contact patch)
((so the tire has to deform more going from more round to contacting flat))

I think, with a skinny enough tire and high enough pressure, the deforming loss no longer negates the mass and aerodynamic advantages.

Then the ride would suuuuuuuuuuuuck.

current record on strava is 80.5kph average and I saw a max speed @82.9kph on fast gravel bikes @ sea otter.
there are several 67kph (ave) with 77kph max done on race bike during critt races.