Bicycle Mechanics - Is It Feasable To Add A Different Chainring (Chaingear) To A Raleigh Venture ?

(This is my first post.)

Without doing my homework I purchased a Raleigh Venture (the basic model not a 3.0 or 4.0) from a bike store in early 2009 and, after not using the bike much, I put it up until just the past few weeks. (If I'd known then what I'm realizing now I would have purchased a Venture 4.0.)

Now I have begun to ride the bike every day (usually just after Sunrise in an attempt to escape the scorching summer weather we're having here in the Dallas area) and have come to the conclusion that the gearing isn't well chosen.

(I don't know 'bicycle-ese' so please forgive if I drop into 'Engineering-speak'.)

As best I can tell the bike is set up with far too low gearing ratios. The Venture has only a single sprocket (40 teeth) on the crankshaft and the rear gearing consists of 7 gears (14 through 34 teeth).

I never use the lower 3 gears as they are totally unusable and spend 90 percent of the time in gears 7 (highest) and 6.

The Venture was not built to accept a replacement Chainring (Chaingear) but it looks to me as though it wouldn't take much to bolt a new Chainring up against the existing assembly (the protective shrouds around the gear are attached with mounting holes that are almost exactly 110 mm spacing - they appear to be slightly less than 3 mm greater in radius).

My intent is to get a replacement Chainring with 50 teeth and bolt it up against the existing 40 tooth gear (the teeth of which are an integral part of the hub). The 50 tooth Chainring will have a radius 25 percent greater than the existing teeth and so should stick out-in-the-clear.

(I think that there may be sufficient available chain to accommodate the 50 tooth gear's diameter but if not I'll put a longer chain on.)

Is there anything about this idea that won't work ? It looks to me like a pretty straightforward thing to do. (The bike shop, where I bought the bike 2 years ago, wants to replace the entire crank assembly and that seems completely unnecessary to me; also rather expensive.)

Thanks;

Paul (WB5AGF)
Garland, Tx

Your shop is right ,the only way to do this is to crank assembly with the chainring you are looking for .

If there is not a removable chainring then , as I understand
you want to bolt one on directly,
as if it were, relying on it being bigger ..
Chain line will be further to the right,
shifting to the Low gear in back will be that much harder..
further offset.

a different crankset with demountable chainrings is where you need to go..

Or like Brompton /Stronglight makes the same sort of swaged arm
on the chainring single speed
in 50t , and a 44t too

It's an unconventional solution that should certainly work, though the chainline will be moved slightly at the front. This will cause a small amount of extra wear when in the lowest gear, but nothing too major. You will probably need a longer chain to accomodate the increase in size.

Paul, You might also consider the rear gearing. Much less expensive: http://www.google.com/products/catalog?hl=en&q=7+speed+shimano+cassette&bav=on.2,or.r_gc.r_pw.&biw=1104&bih=487&wrapid=tlif131107869909210&um=1&ie=UTF-8&tbm=shop&cid=3408390572363276303&sa=X&ei=OHklTuSwEsjl0QHy8rj2Cg&ved=0CD0Q8wIwAg# . With a cassette swap you won't run into a possible off center replacement/add on chainring.

Brad

I agree. While the highest gear won't be much higher with that cassette (13t vs 14t) the gears will be closer together and so more useful to you. Of course, with a 7-speed you first need to determine if you have a cassette or screw-on freewheel.

(Oh no .... the software apparently logged me out while I was entering a reply and it's all lost.)

Well my nicely thought out response has been eradicated (it seems).

I'll let you gentlement know what (if anything) I end up doing.

Best Regards;

Paul (WB5AGF)