Author Topic: Drive train/gearing changes  (Read 9089 times)

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Offline txbevo

Drive train/gearing changes
« on: October 15, 2007, 12:19:38 am »
 I have a new 2007 Bianchi Volpe with the stock drivetrain (48/38/28, 11-32, Tiagra STI shifters and FD, Deore RD). I want to get some lower gearing options as my lowest gear right now is 28x32. I am definitely looking at getting one of Sheldon Brown's custom touring cassettes, probably the 13-34. I also want to go lower in the front with either a 22 or 24 possibly a XT trekking cassette. I am also looking at upgrading to either an LX or XT RD. I have done some minor work on my bikes in the past, but do not consider myself a mechanic and I do not want to get into a job I can't handle. So I will probably let the LBS do the change out for me. However, I do want to know what I am speaking about when I go in.

My question is this: Will I only need the new crankset and cassette to accomplish my objective or will there be any other parts I will need.?
   


Offline Seel

Drive train/gearing changes
« Reply #1 on: October 15, 2007, 06:38:31 am »
I did exactly what you are asking to my Volpe with great results! What I learned: the LX rear cassette bent early on so I changed it for a Scram 11-34. The SCRAM is steel and built to take abuse. The LX RD I purchased is a bottom pull and that in combination with my 35mm tire creates a problem; in order to take off or put on the rear tire it cannot be fully inflated; the RD is in the way. Doesn't cause any problems went the tire is fully inflated just getting the wheel into the dropouts. Also, can't use a fender because the RD is in the way.

It's a great combination that has proven very reliable and very easly on the legs. I also switched out the STI's for barcons.

SEEL


Offline biker_james

Drive train/gearing changes
« Reply #2 on: October 15, 2007, 08:28:23 am »
A quick check of the net shows the cranks as having a 74/110 BCD, meaning you should be able to just change the inside ring for a 24 tooth. Most Shimano stuff works pretty well, even the stuff cheaper than Deore. I think I'd leave the rear deraulleur until it becomes a problem. I have a Sram cassette that has been going a long time, and they are reasonably priced and you can get either 11-32 or 11-34.


Offline RussellSeaton

Drive train/gearing changes
« Reply #3 on: October 15, 2007, 10:53:27 am »
Why not just leave the bike more or less alone and ride it?  Why the urge to change and "upgrade" everything before you even ride it?  Put a 24 tooth inner chainring on the crankset.  Cheap and simple to do and you get lower useful gears.  I did this long ago.  Had the shop do it before I bought the bike so it cost me nothing.  Your low gear will now be 24x32=20".  A 24x34=19".  Big deal.  You can't tell the difference.  After you wear out the current rear derailleur in 10-20-30,000 miles you can "upgrade" it.

If your goal is to build and rebuild bikes, instead of riding them, then you should have started with a bare frame.  Then buy all of the parts individually.  Its fun.  But costly.  Most expensive option of all is to do what you are doing.  Buy a complete bike and then "upgrade" everything on it in the first year or two.


Offline staehpj1

Drive train/gearing changes
« Reply #4 on: October 15, 2007, 03:54:31 pm »
> Why not just leave the bike more or less alone and ride it?

I agree with that.  I would just put on a 24 tooth inner ring and forget about it.  It's your bike though so do what makes you happy.


Offline txbevo

Drive train/gearing changes
« Reply #5 on: October 15, 2007, 07:38:21 pm »
You guys are right. I have gotten caught up in upgrading, etc... and have forgotten about why I bought the bike in the first place. Not only has the upgrade fever kept me from riding it has definitely been more expensive. I should have negotiated any changes when I bought the bike, but I was ignorant about some of what I wanted/needed and I was also impatient. Hopefully lesson learned. I will get the 24 tooth ring and just enjoy riding. I will worry about other changes if or when they are warranted. Thanks for the blunt advice. Sometimes I need a whack to the head to get me seeing clearly.


Offline staehpj1

Drive train/gearing changes
« Reply #6 on: October 15, 2007, 08:34:59 pm »
Good move!

FWIW: We bought three stock bikes changed the cranks (the smallest ring the original one took was 39T) and rode the transamerica route (4200+ miles) with everything else box stock except the addition of fenders and racks.  It all worked out great.


Offline DaveB

Drive train/gearing changes
« Reply #7 on: October 16, 2007, 09:06:49 pm »
What I learned: the LX rear cassette bent early on so I changed it for a Scram 11-34. The SCRAM is steel and built to take abuse.

You bent an LX cassette?  LX cassettes are steel too and, since they are mountain bike components, they are intended to take abuse also. SRAM cassettes are no more rugged than any of the Shimano offerings.  


Offline Seel

Drive train/gearing changes
« Reply #8 on: October 17, 2007, 06:10:49 am »
"SRAM cassettes are no more rugged than any of the Shimano offerings."  

Maybe my wording was not proper; here's what happened. While training for an extended ride I was pulling my BOB trailer with 30lbs of gravel loaded. I was going up a hill and was in my middle ring on the front and the 34T in the rear. I stood to pedal and the 34T bent and the chain broke.

I was fortunate to get a ride to my LBS and there I compared the Shimano LX cassette to a SRAM. Take a look - you'd be amazed at the difference in the construction of the two. Where the Schimano is designed for durablility it also sacrifices some of that durability due to it's lightweight design - especially on the larger rings. The SRAM is heavier but it's design lends itself to be stronger - my opinion only. The design difference is in the support of the large ring. Take a look on the websites.

Since changing over I have climbed the same hill in the same gear with even more weight, put 100's of miles on the bike and have not had any breakdowns.

That's my story and I'm sticking to it!  :)


Offline MichaelTheWingN

Drive train/gearing changes
« Reply #9 on: October 17, 2007, 01:00:28 pm »
I have been watching this topic with interest, I have a background in automotive high performance engine building and quite frankly, what I see is material issues. The brand name or the construction of things makes little difference if theres microscopic stress fractures in the material. Something the manufacturer has little control over. I ride a very stock Specialized, I have always ridden off the show room floor bikes and put 10's of thousands of miles on them from time to time. I have had no issues with parts. I am more then willing to trust a stock SCRAM from Specialized as readily as I am prone to trust a $300 Deore, but it still boils down to material quality and thats something that no one can predict! Is it possible to bend a particular part from any one? Absolutly...Just as it is very possible to put 2,000 miles of touring on a Walmart Roadmaster!

I get the gearing issue, but I don't get why that wasn't addressed at the time of purchase when you have a qualified bike mechanic to bounce questions off of. Now, with my background I fully understand gearing, it's everything in touring. But dealing with gearing is like dealing with tires or clip in peddles, it is a personal choice. For example, I tour with Walmart Pyramid tires. They cost $15 a piece and I get 4,000 miles out of a pair (with rotation). Could I go with a set of $150 Continentals? Sure, but why? I will get the same mileage out of both. Granted, I loose certain things like grip and what not, but tires for a bike are very much like tires for your car.

My impression concerning this thread is it's a choice that should have been made at the time of purchase and it's just material defects that don't show up until that component is under load. But, from an educational stand point, we could all use the opinions put forth!

Have a good ride!

Get a bicycle. You will not regret it. If you live. Mark Twain
Get a bicycle. You will not regret it. If you live. Mark Twain

Offline DaveB

Drive train/gearing changes
« Reply #10 on: October 18, 2007, 08:44:28 pm »
I stood to pedal and the 34T bent and the chain broke.
OK, but I wonder about the sequence of events.  You believe the cog bent and then the chain broke.  I wonder if the chain broke and that bent the cog.

The cog, either Shimano or SRAM. should be plenty strong enough to take the load you describe.  The limiting factor would be rear tire grip, not cog strength.  The rear wheel should slip before you should be able to bend a cog. I expect the chain broke and that caused the resulting damage.

This message was edited by DaveB on 10-18-07 @ 4:44 PM

Offline MichaelTheWingN

Drive train/gearing changes
« Reply #11 on: October 19, 2007, 03:01:04 am »
DaveB:

That theory makes no sense, let me explain.

The chain and the cog make a single mechanical apparatuses, there is little force for the chain to operate independently of the cog to generate that much force. A bicycle is a machine of torque amplification, not horse power (The average human only develops about 1/8 of a horse power). Even if the chain broke first it would continue to follow through the stroke until it reached it's last link as a single unit. More likely, it would have let the energy go in a way that caused the chain to jump the cog and bind in other places. In such a case it would not hold the load possible to bend steel, even in a weakened state. As the tire is the weakest point of the three, it would give long before the cog or chain did. Thus, it is very probable that the cog went first causing sufficient stress on the chain to cause a link to snap. considering that a 34T produces an incredible amount of torque at the rear hub (When a small gear drives a larger gear, torque is multiplied), it is much more plausible that the cog went prior to the chain. But, this is indeed as much conjecture as your theory! :)

Have a good ride!

Get a bicycle. You will not regret it. If you live. Mark Twain

This message was edited by MichaelTheWingN on 10-18-07 @ 11:06 PM
Get a bicycle. You will not regret it. If you live. Mark Twain

Offline TCS

Drive train/gearing changes
« Reply #12 on: October 19, 2007, 02:27:45 pm »
"Why not just leave the bike more or less alone and ride it?  Why the urge to change and "upgrade" everything before you even ride it?  Put a 24 tooth inner chainring on the crankset."

Uh...that would be an "upgrade".  :)

TCS

"My name is Pither.  I am at present on a cycling tour of the North Cornwall area taking in Bude and..."

Offline TCS

Drive train/gearing changes
« Reply #13 on: October 19, 2007, 05:35:09 pm »
When Frank Bowden returned from his first bicycle tour in France, he knew he wanted his touring bike to have lower gears.  Of course, this was in 1887, and it would take him 16 more years to found Sturmey-Archer!

Touring cyclists' quest for lower gears has continued through the decades, and AC's own technical guru John Schubert has written about the too high lowest gears on some of today's factory touring bikes.

TCS

"My name is Pither.  I am at present on a cycling tour of the North Cornwall area taking in Bude and..."

Offline staehpj1

Drive train/gearing changes
« Reply #14 on: October 20, 2007, 08:13:24 am »
> Uh...that would be an "upgrade".

Which is probably why he said "to leave it more or less alone".  There certainly a big difference between changing hundreds of dollars worth of completely functional components for higher end ones and changing a $10 inner ring to get a more suitable granny gear.