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MountainBikeReview.com's Forum Archives - 29inch Wheeled Bikes
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offtopic - Help, changing wheels on a 29er with disc brakes (13 posts)
|  offtopic - Help, changing wheels on a 29er with disc brakes | Edil
Jan 9, 2004 8:23 PM | | This is a little off-topic but please be patient with me. I want to use my bike on roads during weekdays and changing tires each weekend will be a pain in the neck so, for convenience, my idea is to have a second set of wheels with road tires and a road cassette. I bought a brand new Mavic SpeedCity wheelset over eBay at a good price, $165. A second set of disc rotors are on their way too. I still have to buy the road cassette and tires.
The thing is that I was told that I can run into troubles because differences between hubs and pad calibration. To avoid that I have to re-calibrate the pads each time I swap wheels or shim the rotors on the Mavic's to match my current setup. Since I have no idea how to calibrate the pads, can you explain in very simple terms how to do that shim thing and where to find all the parts necessary to do the job? I did a search over the brake forum but the posts that I found are confusing. I will like to do this myself to learn more, with your help of course.
Anything else that I should take in consideration
Thanks! |
| Swapping is easiest if you use identical stuff.... | AK Ken
Jan 9, 2004 10:31 PM | | including hubs and cassettes.
Avid mechanical disc brakes are the most forgiving, and I swap wheels all the time and rarely do more than turn the big red knob a click or two.
If your hubs and rotors are slightly different, just loosen 2 bolts on the Avids, recenter, and retighten the bolts when you change wheels.
I don't know if you want to shim the rotors out from the hub; if you use much shim you'll need a longer set of bolts to get adequate grip.
Shifting is a nuisance unless you use identical cassettes--I had a 34/11 on one wheelset and a 32/11 on the other for awhile, but I was always messing with the barrel adjuster to try to get things shifting right. Your 'road cassette' won't have anything faster than an 11 tooth cog anyway, will it?
Ken |
| Swapping is easiest if you use identical stuff.... | lute mile
Jan 11, 2004 11:31 AM | | On my disc crossbike I run two different wheelsets with two very differnt cassettes. Aside from adjusting the red knobs on the avids I have had no problem what so ever. The hubs are American Classic mtb discs and and King Disc-Go-Techs, and the cassettes are 23/11 and 34/11. I have not had to mess with the RD adjustments between wheelsets to make this work. With this setup I have used my cross bike as a road bike as well. It takes about 5 minutes to switch wheels and make minor adjustments to the discs. This is a great setup and has allowed me to run only one bike since 10/2002, as I rode it on all the mtb rides last season as well. I hope this helps.
THE BUG |
| re: offtopic - Help, changing wheels on a 29er with disc brakes | BruceBrown
Jan 10, 2004 6:57 AM | | What kind of disc brakes do you have? I assume this is for a two niner specific frame, right? It couldn't be easier with the Avid brakes to use an allen wrench and quickly adjust the alignment with the rotors. Certainly a lot quicker than changing the tires/tubes for a road riding set. Loosen the allen bolts holding the caliper to the frame and fork, dial in the red knobs to line up the caliper, tighten the allen bolts and then dial out the red knobs until the wheel rotates freely without any rotor scraping on the pads. 1 to 2 minutes a wheel should be your target goal after the first few initial times. That's for Avids. I don't know what the adjustment process is for other brakes.
That being said, I ran the similar program you are about to do on my 26" wheeled Trek8000. My 26" wheels were DT/Hügi disc hubs laced to Mavic disc 317 rims. The Mavic SpeedCity's with the same size rotors fit in perfectly when I did the wheel change for road riding on that bike without having to make any adjustments on the orientation of the calipers outside of a 1/4 to 1/2 turn with the red knobs that adjust the pads. No allen wrench required and I loved the ability to change my wheelset for the demands of the intended ride on the fly. Try your SpeedCity's on your frame to see how close they actually are as it might be spot on and you will have no difficulties.
On another note - do you think you will have any difficulties with your chain if using a larger sprocket mountain bike cluster and a smaller sprocket road cassette in terms of proper # of chain links for the most "ideal" chain length? Again, it depends on how much difference there is between your granny cog on the mountain bike cluster and your granny cog on the road cluster. What size granny cogs on both will you be using?
BB |
| Something simple is getting complicated here are some bike specs | Edil
Jan 10, 2004 1:44 PM | | My idea was for this to be a simple thing to do and now is getting complicated. I already bought the Mavic Speedcity and those are not the same currently installed on the bike so, I'm going to have to work with that. I already have the second set of rotors which are the same.
Here are some of the bike specs:
Brakes: Hayes HFX-9 hydraulic
Crankset: 48/38/28
Current cassette: 11-34 Sram P970 (9 cogs)
Cassette that I will like to use: Shimano Ultegra 12-27 (9 cogs)
Wheelset/tires: Bontrager 29" Superstock with WTB Motoraptor 29x2.1
Wheelset/tires that I want to use for road: Mavic Speedcity with Specialized All condition Armadillo 700x28
On roads, I'm almost always using the 48 and 38 tooth chainrings, with the first six smaller cogs; very very very rarely use the 28 chainring and almost never the last 2 grainy cogs. I will be swapping wheels at least twice weekly and there are days where I hit the roads just after riding the off-roads trails and I will like to swap wheels. |
| (1) shim the rotors and (2) shim the cassette... | f'nætik (aka næstep)
Jan 10, 2004 2:53 PM | | It'll take a little time to set up initially, but once you get rolling it should be painless.
Whichever rotor (if any) sits in too far, shim out so it has an offset equal to that of the other rotor.
Similarly, you can shim the cassette so they are both lined up correctly. Maybe you'll need a simple twist of the shifter barrel adjuster once you hit the road, but that'll quickly become a no-brainer if it isn't already.
I wouldn't even worry about any excess chain if two different sized cassettes are being used. You'll have no more "slack" chain if you're using the 15T cog of a 34T cassette than if you're using the 15T cog of a 28T cassette, or whatever you end up with.
I'd go for it. It'll work out much nicer than we're leading you to believe. |
| Maybe it's my natural density on display, but | AK Ken
Jan 10, 2004 5:58 PM | | I don't see any significant advantage to running a different cassette on the road, especially since it is one tooth slower on the fastest end than the mountain cassette.
Just changing 2 teeth (from 32 to 34) on mine had me dinking around with the barrel adjusters the whole ride, much less changing 7 teeth with all the different steps in between like he's planning. I understand that the 12/27 cassette is closer ratio than the 11/34, but the nuisance factor would outweigh any powerband advantage for me.
What am I not grasping?
Ken |
| I like the greater "density" of gear ratios... | f'nætik (aka næstep)
Jan 10, 2004 6:12 PM | | ...that a tightly spaced cassette affords, which makes it easier to find that 'perfect' spinning gear on the road. But yeah, just for getting around, I guess it's not that big a deal.
Probably asking too much to suggest he go out and buy two Speedhubs, no? |
| LOL, yeah.... | AK Ken
Jan 10, 2004 6:21 PM | | that may be a bit much for the uninitiated.
Just got back from a dandy ride on my Asylum with sno cat rims and conventional drivetrain...headed for hamburger heaven now, but i'll write it up later.
Ken |
| LOL, yeah.... | Edil
Jan 11, 2004 6:11 AM | | Who's the "uninitiated"?
By the way I saw lot of people writing the letters NM on their posts in this forum, What that means? |
| The 'uninitiated' I'm referring to are | AK Ken
Jan 11, 2004 12:29 PM | | people who do not yet own a Rohloff Speedhub (14 speed internally geared hub that eliminates derailleurs and multiple chain rings/cogs).
Naestep...er...fnaetik has several of them, and I have one.
NM means there's no message other than the topic line.
Ken |
| What parts/tools are requiered to shim? | Edil
Jan 11, 2004 6:08 AM | | As I said in the first post I did a search on the break forum but the posts founded are confusing. Where can I buy those parts on-line? Can you please descrive the process? |
| Shims? Just about any bike shop... | f'nætik (aka næstep)
Jan 11, 2004 9:30 AM | | ...should have a disc brake "support kit" with various small parts, including shims. Online, I'm not sure. But shims aren't bike specific, and I liked the suggestion of the poster in the previous thread who recommended a sheet of material cut into an IS compatible 6-hole pattern.
The cassette shims and spacers, if you need them, you can find on any of the QBP sites such as hammerheadbikes.com or aebike. Shimano makes a .5mm shim that should be enough to shove a cassette into position enough that only a twist or two of the barrel adjuster is necessary after a wheel swap.
All you're doing shoving the shim between the rotor/cassette and the hub so that on two different wheels everything falls into the same plane of alignment. |
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