Gravity racer - Calling all daredevils!

[Philphine]

it's not just finding hills, it's also feeling like it will be a safe run. i think i'll be trying one of the last two i mentioned this weekend if i get up early enough and traffic seems light on it.

another thing is i'm by myself so i'm either leaving my truck at the bottom and pushing the bike up for the ride down, or leaving it at the top and having to push the bike back up after the ride down. a bigger hill will also mean a longer walk. the hill i'm thinking about trying this weekend i may take a regular bike too. that way i can pedal up for the ride down, if the speed doesn't feel that great then i may not bother with pushing the g-bike up.

[Philphine]

the half mile run i mentioned was no good. i'm glad i went ahead and took a regular bike with me.

i took an old ten speed to pedal up the hill, but the coast down was nothing. i had to pedal a a few times to keep going, so it was nowhere near as good as it looked. if the weather holds i may scope out the park loop run for later. again trying to figure out getting back and forth.

and heres a few pics of the other bike (i call it "the poseur, but 'til the other comes up with better numbers, i guess they both are). i need a few things to finish it i have to buy, but this is up to the no money (or really couple dollars) stage.

[Fej]

I just got into gravity bikes in the last couple days (partially thanks to this thread) and finally decided what to do with the bmx bike i've been failing at selling.

Yesterday it looked like this:


And after I finished with it today it looks like this:

[Philphine]

is the bungee chord supposed to be like a steering stablizer? i've been looking at youtbues and picture galleries but i haven't seen that. does it work? since i was making guesses at the rake i might need to try that, if i get a chance to go faster and get some wobbles.

[Fej]

Yeah, its a "ghetto" steering damper. I've seen people using steering dampers from street bikes and dirt bikes to dampen the steering. As far as I know it works, no wobble and there is a bit more steering resistance.

[Philphine]

what's a good size tire to use? i've been looking on ebay and seeing high pressure 20" tires from about 1.35"-2.3". just from trying to look at g-bike pics it looks like they're around the 2" range.

nothing i have around the house is more than the usual 40-60lb range, except a 1.5" 100psi i got for a specific bike that i don't want to take off, and a flea market find (hoffman 110psi 1.9") i put on the poseur 'cause it had white letters like the occ tire.

since i'll have to buy them i might as well be looking for the best size. thanks.

[breakurnees]

Schwalbe Marathons are the standard. I am buying Primo Comets.

[Philphine]

looked at the primos on ebay. the price isn't too bad and they come in sizes i think i'll want. i may try for a pair.

unless someone recommends against it, i'm meaning to get two different sizes 'cause the front rim i've found is a little narrower than the rear. i think i'm gonna try for a 1.5" front and somewhere around 2" for the rear.

[kingfish254]

I was playing around with the mock up of my Fugsley (folding Pugsley) build and thought you guys would get a kick out of it in this config. Has anyone tried using a Dahon folder frame for a gravity bike? You could even attach two Dahon frames together front to back and have a double folding gravity racer.

[Philphine]

i can see it. push everything down for aerodynamics going down, pull it all up to pedal back up the hill.

i'm on hold for tires. i got what i think are decent to pretty good wheels over the last few weeks.

looks like all i'll be doing is trying the same hill again when i get the new tires/wheels on, like an a-b test to see if it's any faster. still haven't found another hill i want to try.

[breakurnees]

That's basically what I am doing. I took a kids full suspension MTB and flipped it, removed the shock and will be replacing it with a couple of heim joints and a turnbuckle. I can extend it until the seat post drags the ground.

[snydur]

IM DONE!! not just with the build, but with going 32 that low to the ground. went to the beach today, would i bring a beach cruiser? nahh, ill toss my gravity bike on the storage rack. about 1 30 or so, roll into my dads boss's beach house over looking a cliff. see the street out front and about a third mile back theres a speedo on a pole. swam, bbq'd and decided to try it out an hour or so ago. held onto my sisters cruiser going up the hill, and came down the other side. it was wobbly, and fast, shoes were scraping, people were looking and half a breath laster i was flying by the speedo pole, kept on going down a bigger hill and decided to call it luck and stop. . . ish. brakes dont help alot. so i got a good rush, sister has a picture of the sign on her ipod ill post it when she's home. but i think this one is just going to stay up on the shelf for a while. haha oh and an fyi, two piece twist bars are a horrible idea.

[breakurnees]

Way to GO!

[Philphine]

you're a faster man than i gunga din

my spare cash has kinda dried up, so i may not get more tires before the deadline. unless i find another hill or get the faster wheels/tires on (which may not make much difference anyway), i guess my 22mph is all i'll have by the deadline.

[Three-Wire]

Well, you guys have inspired me... The Coaster's are hosting a Gravity Shoot-Out in a few weeks and I thought it looked interesting, but Philphine's, Fej's, and Snydur's bikes along with Snydur's experience put me over the edge. I'm in. May not get to run it until after the deadline, but we'll see.

I don't have the gear or time right now for welding, so it'll all be bolt-on stuff. We'll see how my ideas for that play out.... Here's where we are tonight: