Rigidity of donor bike

[Shahmatt]

But there's no rear suspension

Here's another option.

I've found this Hummer frame sold at a discount and within my budget. They've got a variety of colors as well.

The trouble is that there's no rear suspension. I'm wondering about the importance of this, and if I could mitigate this wider tyres. I won't be riding the bike off road for sure anyway.

The rear dropout spacing is also 135mm meaning that these are set up for disk brakes. Can I still fit V brakes on the rear?

I will have to purchase a suitable 100mm dropout spacing suspension fork.

Advantages:

1. The fold mechanism quick release is very discrete and all the way back. I guess this will give me more room for the seat position.

2. The seat post remains independent of the fold but will need to be loosened. Meaning I will not have to remove the Cruzbike seat in order to fold.

Here's a video of the folding mechanism:

http://www.youtube.com/watch?v=4UwixrhGILo

 

[Shahmatt]

On gear inches of 15 to 99.5

@ Chris,

Your GI small end of 15 seems really low. Are the hills you tackle that steep that you require such a range?

I wonder if I've calculated my gear inches correctly. I used the Sheldon Brown calculator as well. My foldie has a 3 speed Shimano Nexus hub. The gear inches are 42 to 78 based on 20" tyres and a 46 tooth crank wheel and 15 tooth sprocket. I've found that this is fine for the flat route I usually travel and for mild hills.

I've aimed to improve the low end with the Nuvinci to tackle more hilly regions, and hence the drop from 42 to 37. Well maybe I'll bring it down to 30 by choosing a larger sprocket.

 

[Charles.Plager]

Hi Shahmatt,
My low end is

Hi Shahmatt,

My low end is 17" on my Mantis (closer to 16" on my Sofrider). Remember you can't stand on a recumbent and because it's front wheel drive, if you try to go up steep hills in too high a gear, you're more likely to spin your front wheel.

As far as no rear suspension, many conversion have been built with no suspension and have worked fine. Yes, I think you'll want to go with wider tires to help cushion the ride. I do think rear suspension is probably more helpful than front and that suspension is better than no suspension for Cruzbikes, but I do think the frame you found will work. You can connect the seat pan and seat back with something easily removable (like I've done on the Mantis) and so you'll be able to separate them, pull the seat back off, and fold the bike fairly easily.

Cheers,
Charles

 

[chrisblessing]

Low end of 15

Hi Shahmatt,

I can guarantee that 15 is not too low. Kuala Lumpur is a city of hills and grades of 8-12 degrees are common, with some steeper still. When I first built this bike I had a low of 23, and I simply could not power up many of the hills, for the reasons Charles describes. With my current setup I can get up most hills, albeit slowly. There are some very steep hills that I could I can barely get my Dahon up that I won't even attempt with my recumbent. The slowest I can go without tipping over is about 6 or 7 kmh; better to dismount and walk.

Chris

 

[Shahmatt]

Scratch the Hummer option

@ Chris and Charles,

Scratch the Hummer frame option. The option to not remove the seat while folding is attractive. However the fold still requires removal of the front tyre. I thought I could mitigate this by purchasing a shorter front suspension fork but on looking at the geometry again this still doesn't look feasible.

I didn't think this one through properly. Sorry for the trouble guys. Forgive also my endless posts on different frames. My planned start of this project only begins January next year. So I'm still in that brain storming stage.

In order to minimize the front-wheel spinning problem, can change of body position, e.g. moving to the front edge of the seat or leaning forward help to increase the weight balance to the front tyre? Is it even possible to change body position like this whilst riding on a recumbent?

 

[chrisblessing]

Body position on hills

Absolutely, your body position makes a world of difference. Cruzbike riders frequently mention that in their ride experiences. By pulling oneself forward, thereby shifting weight over the front wheel, slipping is mitigated. I find as well that, because my bottom bracket is relatively low, by pulling myself forward it has nearly the same effect as really standing on the pedals on a DF.

 

[Charles.Plager]

 What he said.

What he said.