Folding Bikes - Upgrade a Citizen Gotham

Hello,

I received a Citizen (Gotham model, 20" wheels) folding bicycle as a gift. Yup, I know that this forum views this model as the "Wal-Mart" grade of bike, but the quality of the product seems good enough for my occasional needs. Primarily the size/weight is perfect for my plane. However, the limitation of a 6-speed (Shimano Revo shift) is a problem. That top gear feels like it should be the lowest gear for my long legs!

Hey, I haven't worked on bikes since I was a teenager and the technology has changed a bit. I am thinking of increasing the size of the chainring from the current 48 tooth design to something larger. I have seen some chainrings as large as 58 teeth, but realize that a whole domino effect with changing one component will start. Any suggestions? Will an increase of just a few teeth in the chainring make that much difference in top gear?


Live, love, and laugh,
Dr. Z.

For a while, I considered buying a Gotham. It has a good frame, and certainly is worth the upgrades.

In my case, I would probably be happy with the stock gear ratios, but that's me. I don't like pushing big gears, and prefer instead to "spin" at higher cadences.

Part of the fun of the cycling is to experiment to the point where you are totally satisfied with your bike. It sure is a lot cheaper than customizing cars, trucks, boats, etc.

Edward

Few months ago I got the Gotham (my first folders ever) and they were very good in general. However I had problems with the rear break and the gear. The rear break is not positioned on the radius line of the wheel and as a result the movement of the pads is not parallel to the wheel's surface. This makes it impossible to adjust for a good break on one hand and non binding on the other. As for the gear, it was shifting 4 tiles out of 5 tries which was very annoying. I took them to a LBS for tuneup but this did not help much. After struggling with the setup for a week or two I returned then and ordered a BF NWT.

I believe that these two defect could be fixed by a design change without increasing the manufacturing cost. This would make them an excellent value for the money IMO.

To get a better idea knowing what the rear cog is could help. I think a bigger chainring in front should be easy, longer chain could be the only thing needed.

I am sure that edwong3 is right in suggesting that you could do some research about your present cadence and compare it to the ideal cadence. In the old days we used heavy gears and pushed hard. Now we are told the legs should spin much faster. What shape you are in and what your area looks like also counts a lot.

However I had problems with the rear break and the gear. The rear break is not positioned on the radius line of the wheel and as a result the movement of the pads is not parallel to the wheel's surface. This makes it impossible to adjust for a good break on one hand and non binding on the other..

You mean you couldn't rotate the pads on their brake arms to align them parallel with the rim? A well known brand, Dahon, uses the same type of frame on the "MU" models, and the rear brake is mounted just like the Citizenbike. Also, the shifting issue you were experiencing is not normal if you had it adjusted properly. Any possibility the derailleur hanger was bent? That could cause a problem like you were describing.

Anyway, enjoy that new BF NWT. It seems that is a great bike!

Edward

You mean you couldn't rotate the pads on their brake arms to align them parallel with the rim? A well known brand, Dahon, uses the same type of frame on the "MU" models, and the rear brake is mounted just like the Citizenbike. Also, the shifting issue you were experiencing is not normal if you had it adjusted properly. Any possibility the derailleur hanger was bent? That could cause a problem like you were describing.

Anyway, enjoy that new BF NWT. It seems that is a great bike!

Edward

Attached are pictures of Gotham and MU SL. Noticed the angle of the rear breaks (marked with red lines). Because of the angle of the Gotham's rear breaks, the front and rear ends of the pads have different pivotal radius. This makes the front end of the pad opening/closing more than the rear end. Seems to me as a sloppy design.

As for the derailleur, yes, it was bent and the rear wheel was untrue. My LBS fixed it but it did not help much. The shifting was still non reliable.

I did not want to keep struggling with these problems so I returned them. It was pity because other than these two problems I actually liked that model.

Kam

Generally the brake pads on a linear/V brake, use a washer between them, and the brake arm, that acts as a cam to adjust their angle in relation to the rim. That would have allowed you to make it so that the frontal portion of the brake pads make contact with the rim first, instead of the way it was happening on your bike.

I suspected the shifting problems were due to a bent derailleur, or the hanger. Apparently, the bike was mistreated during shipment, and damage occurred to it.

Regardless, that is behind you, and now you are awaiting on a Bikefriday.

Cheers,
Edward


Attached are pictures of Gotham and MU SL. Noticed the angle of the rear breaks (marked with red lines). Because of the angle of the Gotham's rear breaks, the front and rear ends of the pads have different pivotal radius. This makes the front end of the pad opening/closing more than the rear end. Seems to me as a sloppy design.

As for the derailleur, yes, it was bent and the rear wheel was untrue. My LBS fixed it but it did not help much. The shifting was still non reliable.

I did not want to keep struggling with these problems so I returned them. It was pity because other than these two problems I actually liked that model.

Kam

Thanks for the replies everyone. I realize that swapping out the chainring will be more costly than I had anticipated. So, I hope to change out one or more of the sprockets in the cassette. Here is what is on the rear of the Citizen Gotham now (Shimano MF-TZ20, somehow not found on the Shimano web site):

http://www.sjscycles.co.uk/product.asp?pf_id=18963&src=froogleUS&currency=USD

It's smallest sprocket is a 14 tooth unit (14, 16, 18, 21, 24,28). I have seen Shimano cassettes that have sprockets as low as 9 teeth here:

http://www.sheldonbrown.com/capreo/index.html

However, this is a 9-gear system and I currently have a 6-gear configuration. Is it possible to just change out one or more of the sprockets in what I currently have? Am I missing a complete cassette that will work and is somewhere in the 9-28 range on the Internet? Ha, I work on cars and aircrafts, but somehow this whole bicycle parts searching is a little daunting!


Knowledge is power, but an good attention span can never be replaced,
Dr. Z.

Well first of all, the MF-TZ20 is a "freewheel", unlike the Capreo which is a "cassette". In your current setup, the freewheeling mechanism is inside the cluster of gears itself, while in the other system, it is in the hub. I don't think that you can change out individual cogs on a freewheel, though I believe you could do that with the older SunRace clusters.

In order to use a cassette type gear cluster, you would have to change out the hub, the chain, the shifter...just about EVERTHING on your drivetrain. It's not going to be cheap, especially the Capreo. And from what I understand, those (Capreo) are hard to come by for an individual, though I could be wrong there.

I'm not too sure if you can still get the 7 speed Shimano freewheels with a cog as small as 11 tooth. That would be quite cheaper than going the other route, and just change over to a 7 speed setup.

I know this may not be much help to you, but you could do a search on Google and perhaps come across some suppliers that may still have those 11-28 clusters in stock.

Regards,
Edward


Thanks for the replies everyone. I realize that swapping out the chainring will be more costly than I had anticipated. So, I hope to change out one or more of the sprockets in the cassette. Here is what is on the rear of the Citizen Gotham now (Shimano MF-TZ20, somehow not found on the Shimano web site):

http://www.sjscycles.co.uk/product.asp?pf_id=18963&src=froogleUS&currency=USD

It's smallest sprocket is a 14 tooth unit (14, 16, 18, 21, 24,28). I have seen Shimano cassettes that have sprockets as low as 9 teeth here:

http://www.sheldonbrown.com/capreo/index.html

However, this is a 9-gear system and I currently have a 6-gear configuration. Is it possible to just change out one or more of the sprockets in what I currently have? Am I missing a complete cassette that will work and is somewhere in the 9-28 range on the Internet? Ha, I work on cars and aircrafts, but somehow this whole bicycle parts searching is a little daunting!


Knowledge is power, but an good attention span can never be replaced,
Dr. Z.