Folding Bikes - Best headtube angle for old folder.

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badmother
11-23-08, 05:20 PM
Could somebody tell me the best headtube angle for an old "R20 like" detatchable? Looks much like the famous R20, so I think they can be compared.

I am going to put a new fork and since I find the headtube (and seattube) angle wery "relaxed" I was thinking of cutting off approx 1 1/2 cm of the lower part of the head tube before cutting it to the right lenght for the new fork.

What makes me think twice is that I`we got a similar bike, only 24" wheels. I rode it for a short time with a 26" rear and a 24" front just to test out the lowered front. Found the steering "twitchy" and strange. What is the best angle for such bikes?

http://i277.photobucket.com/albums/kk51/badmother-bikes/Lillafolder1.jpg

The purple bike is mine, but picture is not good,

http://i277.photobucket.com/albums/kk51/badmother-bikes/Butcheredfolder.jpg

Blue /green bike is not mine and picture is not mine but same type bike and better picture.

http://i277.photobucket.com/albums/kk51/badmother-bikes/Dogbike20411-1.jpg

Brown bike is my 24" that I tryed with lower front to change angle.

What do you think?

faffer
11-23-08, 05:39 PM
I can't answer your question, but I want to know more about the last bike. Is that a frame extension or is the bike originally like that?
badmother
11-23-08, 11:55 PM
I can't answer your question, but I want to know more about the last bike. Is that a frame extension or is the bike originally like that?

That is "Dogbike2", a DIY longtail /extracykel-like bike. Wanted a detatchable one since the first one I built is a bit difficult to transport on a small Toyota. Use it to ride ith my dog and to give him a lift when I go further than what is ok for him to run, or for shopping. This bike started out just like the others, but with 24" wheels instead of 20".

http://i277.photobucket.com/albums/kk51/badmother-bikes/Dogbike20411-3.jpg

timo888
11-24-08, 05:42 AM
What makes me think twice is that I`we got a similar bike, only 24" wheels. I rode it for a short time with a 26" rear and a 24" front just to test out the lowered front. Found the steering "twitchy" and strange. What is the best angle for such bikes?

The Xootr Swift's 72 degree angle doesn't feel twitchy to me.

If you were building the frame and intending to have a 26" rear 24" front: if you started with a 72 degree angle on the 26" front wheel, and then you swap in a 24" front wheel, you are tilting the head-tube forward about 3 degrees (assuming a 41" wheelbase), to around 75 degrees, shortening the trail. So you'd need to compensate by about 3 degrees. You'd want to weld the new headtube at a more acute angle, about 69 degrees, so that it would tilt forward to 72 when you install the smaller-diameter front wheel and the larger diameter rear wheel.

Regards
T
badmother
11-24-08, 10:51 AM
The Xootr Swift's 72 degree angle doesn't feel twitchy to me.

If you were building the frame and intending to have a 26" rear 24" front: if you started with a 72 degree angle on the 26" front wheel, and then you swap in a 24" front wheel, you are tilting the head-tube forward about 3 degrees (assuming a 41" wheelbase), to around 75 degrees, shortening the trail. So you'd need to compensate by about 3 degrees. You'd want to weld the new headtube at a more acute angle, about 69 degrees, so that it would tilt forward to 72 when you install the smaller-diameter front wheel and the larger diameter rear wheel.

Regards
T

Ok, thank you. I am mainly working on the 20" at the moment and want to do the same with the 24" later. I am keeping same size wheels on the 24".

I`ll stick to 72 degrees, I`ll post pix when done.