11/22/2006

Dumbest rear wheel ever...

My bridgestone picnica has one weird rear wheel. Wheels on folders are often weird, but this one is really odd.

First it is a nice 14" 253mm size. Which is not all that common. Stock tires are 14x1.75" slicks. I found some 14x2.25 knobbies in my LBS to replace em. But if you are looking for them online: bicycle south carries them, Dahon uses them for their sweet pea bike and can supply them. If you want your LBS to order them the supplier Hawley has the slicks and J&B looks like they carry the knobbies. There look like there are a bunch of 14" sizes, so be careful, you probably want the 253mm size (sometimes listed as 254mm). The helpful guys at bicycle south told me it is common on wheelchairs and scooters. So there you go...

Second it is a 20 hole hub and rim. Then there is the odd shimano single speed mini cassette hub.
And it has a drum brake. And it has chain tugs. And the kickstand mounts on the rear wheel. Whoo. Lots going on there.




click for big

Unfortunately it is really hard to get the rear wheel out without taking the chain off the chainring, which normally is not that big a deal, except it is darn near impossible to rerail the chain while it is in the chaincase. So I took it off. Here is what the 51t chainring looks like under that chainguard:


click for bigger view of the drivetrain

Thats a 51x14 drivetrain with a 14" tire for a 51 odd inch gear. mashing.

Now reactionary mechanics are probably smugly saying how superior forward facing dropouts are. I call BS. They are, in this case, useful for only one thing. Getting the rear wheel out without having to derail the off the chainring. I am not convinced that the chain would not fall off the chainring anyway while you were working on it. Secondly, the wheel might bonk the chainguard on the way out. Just like the wheel often will hit fenders or chainstay bridge on the way out the front facing dropout. Not always. But often it does. Finally the rear facing dropout inline with the chainstay gives, by far, the most options for gear changes. Not that I can ever change the gear ratio on this fairly obscure hub and crank, but I love the utility of rear facing dropouts. Especially with fixies, coasters and hub braked bikes that don't run rim brakes. If you angle the dropout, you loose some of the effective lenght. If you have angled short horizontals that face forward you loose a considerable amount of rear wheel adjustability. Short front facing horizontal dropouts is one of my least favorite specs on frames. I would much prefer that my wheel hits the rear of the fender as I pull the wheel out rather than bottom out on the immovable chainstay bridge or front fender. Anyhow, these are some nice utilitarian dropouts, I like em:



click for big

Chaintugs however, are utter travesties of bicycle gear. I kept em on in this case as they are a stock chunk on this bike, but whoo boy, they may make tensioning the chain easier, but they sure don't make it easier to get the wheel out. You have to undo the chaintug almost completely to get the wheel far enough forward to get the chain off. Stupid for a bolt on chaintug, that makes two wrenches to get the rear wheel out. Yuk. Is it that hard to get chains tensioned? Does it help the simplicity of your cool fixie? Nope. Like I said though, there is so much going on with this rear wheel that there is little reason to make things better. I think this is a prime candidate for a coaster hub. That would eliminate the huge drum brake attachment, the cable run to the rear and would allow me to change gear ratios. If I can find some, uh, high quality aluminum 14" rims I might do it. Or maybe a nice 12" rim. I read somewhere that the japanese version of the picnica has 12" rims. I would love to cram a 16" 305mm rim in there as you can get some nice maxis hookworm tires in that size among other high pressure wide slicks, but I am pretty sure I am running tight on the front already and might not have room in the rear. A project for another day...

I guess the only way to make the stock rear wheel dumber is by running it with bobnutz, you know so I could pull a bob trailer behind. Anything else I could do?

The tires went in pretty easily. They did not seat like champs. I spent some time getting the front seated, but got lazy on the rear and paid for it as now I need to get it reseated while on the bike, or take it off again. I also slimed the tubes AND duct taped in some Mr. Tuffies so that I can avoid taking it off if at all possible. Here is a shot of the whole bike with its new tuff looking knobbies:



click for big


Here are a few more photos of the bikes quirks:

Handlebar reflector and bell:


Fork Crown:



Some photos of the bike in it's mostly stock condition here.

7 comments:

Olyfixie said...

Heck, Tarik. There's lots of scope yet for tomfoolery. Crowsfoot spoking. Spokeydokes. Ooh, ooh! with four-cross spoking, so that the spokes cross the flanges at right angles!

Maybe you can convince Grant to bet the future of Rivendell on a run of 1,000 SpeedBlend tires in this size. He could name them Teeney Weenies.

You could supplement that drum with an under-the-bb U brake.

And, dude, where are your grinder pegs?

Doug said...

Tarik, it looks like Schwalbe has a Big Apple in this size. Not cheap for a tiny tire, but surely the nicest thing available for all around use...

Doug

Anonymous said...

Hello!

Did you figure it out if it's a cassette or freewheel or what? I have a Decathlon B'Fold which is exactly the same bike, maybe the only difference is the V-Brake on the front. Mine has an 11T sprocket rear, with 46T crank. It would be great to add a 15t and a 21t sprocket and change the crank to 52, but I can't recognise this rear mechanism.
TomBdigger from Hungary

Tarik Saleh said...

Tom,

I was wondering where all the Hungary traffic was coming from...

I am pretty sure it is a little casette,t bu I have not taken it off since these pics, although I broke a few spokes recently and the rear tire is getting worn, so it is time to re-explore. In the US you can get these rims (steel only it seems) through J&B, I think your best bet is to lace up new wheels rather than working with these...

Tarik

Anonymous said...

Hey Tarik!

Thanks for the quick response! As I see there would be enough space for a 16" wheel there, because the main problem is that I couldn't find any 20 hole hub, only 28, 32 and 36. But the OLD is less than 120mm, and I don't know if a cassette hub could be respaced so narrow. Isn't it possible, that this hub would accept a normal sized freehub body? A 7 speed one is not that wide. There is another option. Some months ago a hungarian guy tried to setup some kind of speed record behind a truck, and he also had a smaller wheel bike, maybe 20" or so. He said it's better. He solved the small wheel - low ratio problem with an other cassette hub. He welded a console between the rear wheel and the chainring, and put in a rear hub, without spokes and wheel. It had only 2 sprocets, the smaller was in connection with the chainring, the bigger with the rear sprocket. It has deraileur possibilities within by my opinion.
If you're interested or didn't understand I can find it on the internet or draw a picture.
So far I found that the Sturmey-Archer has a three speed internal gear hub with 114 or 117 mm OLD, accepts 13t sprocket and it's the middle speed, the other two are -33% and +33%. But it costs itself, with shifter but without the new rim and spokes double the price I bought this bike.

Tom

Tarik Saleh said...

Tom,

I think the bike was made to take 14" or 12" wheels, (at least the bridgestone version). 14 for the export market 12" for theJapanese market. In the US, you can get pretty high quality aluminum rims and tires in the 12" size. If I were to change the rear wheel I would probably put in a coaster brake, or maybe a 2 speed kickback hub... I don't think I would mess around with the gear ratio too much. If you are committed to gear getting a bigger gear, look at what Dahon and bike friday are doing. I think an internal hub would be the way to go, but it will not, as you point out, be cheap.

Good luck, let me know what you end up doing.

Anonymous said...

As I promised, the hungarian speed chasing guy:
http://kerekagy.blog.hu/2011/04/07/illegalis_sebesseghajhaszas_100_folott_biciklivel
Sorrily his bike has been stolen yesterday :(

Tom