Which Bike gets the new crankset?

May 15, 2008 7:33 PM

MTBFilter: Which of my two bikes should get the new LX Hollowtech II Crankset I just bought and should I use an XTR Rear derailler on my commuter?

In follow-up to my question last month I took action on some of the great advice given.

Here's the dilemma:

1. I bought a bunch of stuff to convert my Commuter ('94 LX 7 speed cassette) to XT level 8 speed.

2. I also bought a brand "new" bike, a pristine 2001 GF Hoo Koo E Koo Disc
which will be my new trail bike. This bike is practically bike shop new and has never seen a mile of off-road riding. This is going to be my new off-road rig.

Included in the stuff I bought for my commuter is an FC-M542 Hollowtech Crankset and bottom bracket. Now I'm wondering if it might not be a better choice to take the practically new Bontrager Sport off the GF to use on the commuter and beef up the off-road bike with the new Hollowtech II crankset?

I also bought a used XTR RD-M950 for the commuter to replace the '94 LX rear that has served me so well(the '94 LX has aluminum Carmichael pullies). I've heard/read that the '94 7 speed LX also works for 8 speed. Would leaving the '94 LX on the commuter with the new 8 speed cassette be more prudent than sending an(albeit used) XTR out in the rain?

Oh one more, please. I've read that "facing" your bottom bracket shell is important with these new external bearing cranksets. Is that something I really have to go to a bike shop for or can I just sand the paint off the edge of the bottom bracket shell with a block of wood and some sand paper?

Thanks in advance for your help in bringing my bike knowledge into the 21st century.

posted by Rafaelloello to sports, hobbies, & recreation (14 comments total)

Maybe try a bike forum?
posted by artdrectr at 8:56 PM on May 15, 2008

Or a bikeforum. God knows they've got opinions on other people's bikes.
posted by mendel at 9:06 PM on May 15, 2008 [1 favorite]

Let's tackle the easy question first. Facing the BB shell or headtube means to grind the end surfaces such that they are perfectly parallel with each other, to within some insanely tight tolerances, let's say 1/1000 of an inch. The tools for facing and chasing (recutting the threads) BBs and headsets are easily the most expensive in any bike shop by far -- several hundred dollars for each. The BB and headset are the two most stressed points on your bike -- if the interfaces aren't faced properly then your BB and headset bearings will die VERY quickly and you'll be replacing . Block of wood and sandpaper...hmm...ARE YOU ON CRACK?????

As for what parts to put one which bike, it's really a matter of preference. My thinking is that heavy duty, durable parts go on the commuter, light and shiny on the other bike. That doesn't necessarily mean that the commuter gets the cheap stuff -- durable stuff is usually more expensive.
posted by randomstriker at 12:02 AM on May 16, 2008

The BB and headset are the two most stressed points on your bike -- if the interfaces aren't faced properly then your BB and headset bearings will die VERY quickly and you'll be replacing . Block of wood and sandpaper...hmm...ARE YOU ON CRACK?????

OK, I guess my facetiousness escaped some. No worries. The implied question was meant to be:

How well are bottom bracket shells factory faced on pre-external bearing BB shells

If the intended recipient was an early 90's era Somerville Merlin frame, I would be confident installing this crank without any preparation whatsoever to the bb shell, as I know that it would already be paintless and unrusted (Titanium) and that precise facing and cutting of the bb threads was the very last manufacturing operation performed on the frame and would still be true today. I was thinking that if it was actually the last manufacturing step prior to painting a chro-moly or aluminum frame, that determining the edge of the shell to still be painted would seem to imply that the facing is still precise beneath the paint?

It would have been a little pithier if you asked if I was on CRANK.
posted by Rafaelloello at 4:50 AM on May 16, 2008

I would definitely replace the Bontrager crankset with the Hollowtech. It's going to be waaay better. Facing is only necessary on new frames. If a crankset has already been installed it's going to be fine. If you meet resistance when installing the outboard bearings you can take it down to the local bike store to get faced, but I'd be amazed if it was necessary.

Re the XTR derailleur, again I'd probably do it. It's going to be nicer shifting than LX stuff of that era. The LX will work fine for 8-speed though.
posted by unSane at 5:24 AM on May 16, 2008

With some exceptions, a derailer is a derailer is a derailer. Your 94 LX could shift 10-speed cassette if you were so inclined. All the "shift logic" is in the shifter pods---deraillers (generally) don't care. The XTR may be a bit smoother and is most definitely lighter, but I doubt you would notice much difference on the commuter. Either should work fine if they're in decent mechanical shape. IME, front derailers are much more sensitive to group quality than rear ones.
posted by bonehead at 8:23 AM on May 16, 2008

So then The Hollowtech definitely goes on the new trail bike. Would moving the virtually new Bontrager (22/32/44) be a step up or sideways from my venerable '94 LX (22/32/42) ? I just received the XTR deailleur this morning(ebay) and it is medium cage, I presume(not as long as my LX, but not roadie short either, stamped RD-M952). I'm going to be running a brand new 11-28 XT cassette, new chain(of course), but I'm up in the air on swapping the crank, and having to maybe raise the FD a hair for the extra 2 teeth on the big ring. I've been pretty satisfied with my LX crank. I've had to replace the middle chainring a few years ago, but that's about it. I notice the Bicycle Tutor has the same '94 7 speed LX Group on the commuter bike he uses in the videos. I guess the prudent thing to do is to change over to the XT 8 speed shifters, cassette, and chain and see how they do with my old derailleur and crank. Then change out the RD and see how that goes, then finally the crank?
posted by Rafaelloello at 8:40 AM on May 16, 2008

unsane is wrong.

The original concern you had is exactly correct -- going from inboard to outboard BB bearings on an old bike complicates things. If there's paint on the ends of the BB shell, it DEFINITELY has to be faced. The layer of paint itself is likely several times greater than the facing tolerance, plus it is very uneven. The interface has to between bare metal surfaces.

"meeting resistance when installing the outboard bearings" is completely irrelevant to facing (making sure the ends of the BB shell are perfectly parallel). Resistance indicates a problem with the threads, and that's where chasing (recutting the threads) comes in. The words rhyme but they mean two different things.
posted by randomstriker at 10:19 AM on May 16, 2008

Well, I guess since the Hoo Koo E Koo frame is both aluminum(where I could conceivably remove more than paint) and otherwise perfect, I'll probably buckle and bring it to my LBS and ante up for the face and/or chase. I wonder though if some of these obsessions with facing the bottom brackets is really necessary. I imagine all pre-cartridge cup/cone bb shells were faced at the factory for the same reasons that they are faced today (bearing race alignment). The only way it makes sense that you need to re-face(as opposed to removing the paint, and I'm not 100% sure that is truly necessary) for cranksets from the "cartridge era" is that maybe manufacturers were lazy about facing since the one piece bb would keep the bearing races in perfect alignment no matter the shortcut taken by not facing the bb shell. I was trying to ascertain whether mid 90's to early 2000's bb shells are faced at all. I could imagine where corners could have been cut during this period by perhaps only facing the side of the shell where the cartridge threads in.
posted by Rafaelloello at 10:51 AM on May 16, 2008

Well I guess at the end of the day, "necessary" is subjective. At my shop, we think big problems are caused by small problems left for too long, and those small problems are usually caused by cutting corners at the beginning. But then we have high standards -- not everyone does.
posted by randomstriker at 11:02 AM on May 16, 2008

Jeez. After reading this thread on Bikeforums, I'm worried about where to get by bb faced, too. Any suggestions in the Boston Area?
posted by Rafaelloello at 12:17 PM on May 16, 2008

No, but come to La Bicicletta if you're ever in Vancouver :-)
posted by randomstriker at 1:26 PM on May 16, 2008

Ok, thanks to:

randomstriker for convincing me to face my bb(and face my unfortunate drug habit), Unsane for guiding me to putting the new super-stiff crank on my new super-stiff frame instead of the commuter, and bonehead for his derailleur advice. I have at least two more best answers queued up for the right answer to these questions:

1. Commuter bike - replace '94 LX crank with '01 Bontrager Sport or let sleeping dogs lie?
2. Best place to get a BB faced proximal to zip code 02135 (Boston/Newton line)
posted by Rafaelloello at 5:22 PM on May 16, 2008

I'm sure nobody cares about this now, but I put the Hollowtech crank on the GF Hoo Koo E Koo, and along with Avid Ultimate brake levers($110 on eBay), it is my sweet, sweet, hardtail for the trails. Very, very pleased with the power I can put down with the hollowtech. Ride it every weekend on local singletrack.

On the commuter (approaching 2000 commuter miles since April), I did switch to the XTR Rear derailleur, XT cassette, and a new chain. I am considering going back to the LX Rear derailleur for the winter and am currently shopping for studded ice tires. I'm going to commute right through the winter and am actually looking forward to it.

Also took my 1975 Raleigh Competition out of mothballs and outfitted it with new tires(Michelin Orium), tubes, and rimstrips. Put about 60 miles on it over the last few weekends. It still rocks.
posted by Rafaelloello at 7:48 PM on October 5, 2008