i find it much harder to skid the rear wheel on my bike than my girlfriend's bike. which of these do you think is the biggest culprit?

1. wheel diameter: 20" vs. 700c
2. tire width: 35mm vs. 28mm
3. tire material (??): irc metro vs. continental grand sport
4. gear inches: 75 vs. 70
5. geometry: swift folder vs. kona paddy wagon

hopefully not 1 or 5, because i can't change those. but if you think it is, i'd still be happy to get a good explanation for why.

4 for sure and maybe 5.

2 and 5

2,4,5

2 and 5

4.

Which bike is easier, the paddy wagon or the folder?

1, 2, 4, 56, 2235, 666, 109566, 548348, oh and 5

the paddy wagon is way easier.

i'm inclined to think that the gear inches don't have that much to do with it, because it's not that different from when the swift was at 69". skidding just feels way smoother on the paddy wagon: it takes less effort to break traction, and the sensation of skidding is much smoother, i would even say gummy, whereas on the swift it's much rougher.

why do you think geometry has an effect? is it something i could correct for by adjusting my body position?

4 is the easiest fix and a likely culprit

Wider, nubbier tires will produce more friction. I'm not sure why the geometry makes it so different. My guess would be that the center of gravity is further back on the folder due to the frame design, so it's harder to lift the back end as much as a road frame. I'd guess that the balance would be better on a road frame as well, and balance is a big part of the ease of skidding.

this part is true. friction force is determined by the relevant coefficient of friction and the surface area (contact patch) involved; on pavement or other smooth surface your maximum contact patch will be on a fat slick with medium air pressure. knobbies prevent the full surface of the tire from touching the ground, thereby reducing available frictional force.

2-5

1,2,4

skill

Good point. Do knobs drag in a way that produces more friction though? I would expect them to have a higher coefficient of friction than the slick rubber; I realize it's the same compound, but it seems like the knobs (being solid rubber and not a pressurized shell) would be gummier and thus drag more.

With that said, I had no trouble skidding on my 82 gear inches with 700x32 treaded tires, so there's more to it than just tires and gear inches.

1, 3 and 4

mostly 4

5

those gearings are kind of close, so i'm guessing geometry has more to do with it. i'm about 6'1" and i'm used to skidding from just out of the saddle (more about function skids lately) at 73.5 gear inches. i tried skidding on my friend's bike (she is much smaller) who has a lower gearing and it was toughhhhhhh to get used to. geometry made a big difference there.

and about the tires, i still switch mine up a lot, partly to figure out what i like, partly because i don't always have money...but i notice a big in how skidding feels, even to the point where it takes more effort to skid on some of the same size tires.

I find it much harder to skid on my girlfriends 50cm Jamie Roy. [I ride an Angus]
Same ratio, but i think its just the geometry that messes with me, it's probably because I'm just not used to it.

[This is the complete opposite of your problem, sorry ]

6. not enough vaseline

gear inches matters, but it just means that the heavier the gearing the more committed you have to be. heavy gearing will want to kick you more, but you can lock it up just as easy if you are forward enough.
Bullhorns will help a LOT. You can get forward another 6 inches or so.
Small gearing will help makes things a bit easier for now, even if that sounds like a contradiction to what I just typed.
Vittoria Randonneur tyres skid like crazy, and are strong and cheap.
A bigger frame that fits will help a lot too, because the bars will not hit your knees.

geometry and gear inches are the only two that i think are affecting your skid.

WHEELBASE! On your swift, the wheels are probably about 5" closer together than the Kona. The gearing difference is probably secondary. But I say wheelbase more than anything.

those of you who said "geometry" get a gold star! i switched my stem from 90mm to 130mm and it's noticeably easier now. i suppose because i'm further forward, i can unweight more effectively.

i'll find out about tire width soon too, as i'm switching from 33mm to 28mm tires.

Seems the type of bars made a huge difference with my skidding endeavors... from the bullhorns (i got great ease of skidding) to chopped flat bars... much more difficult...