Bicycle Mechanics - Mountainbike crankset on a roadbike
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07-14-02, 05:13 PM
I have a roadbike with Sora 8 speed 48/38/28 crankset and a 12-32 cassette.I'm thinking of putting on a 44/32/22 for touring by suggestion of a bike shop.Can anyone tell me what problems I might have with chain length or front derailleurs or anything else?
07-14-02, 05:21 PM
Yes, your chain will indeed need to be shortened.
I don't think that you can use a mountain front derailleur with an STI shifter but I might be wrong. I also don't know if your current derailleur will function correctly with the smaller chainrings, but I would try that first.
You may also require a new bottom bracket to maintain a decent chainline, depending on the crankset.
07-14-02, 05:32 PM
mmm,I hadn't thought about the bottombracket.Also I forgot to mention I have downtube shifters.
A MTB crank and 32 cog in Indiana???HFC ............if you are 90 and use an oxyogen bottle I will cut you some slack.Otherwise........ well,you get my drift. 12 year old girls ought to be able to handle anything in indiana with your present setup.So maybe you are touring outside indiana?? I hope. Bikerider is a sharp guy for this place. Your road derailer may not work well with a compact crank. Different spindle length is a possibility,but absoulte correctness in chainline is not as critical as some would have you believe if the chainrings clear the stays and the derailer will shift to the big and small rings. Downtubers will work fine. Shorter chain maybe.
Frankly. there is no reason for you to go to smaller Chainrings. With the gearing you now have, even if your bike is loaded with 60 pouinds of gear, there isn't a hill or mountain that will give you trouble --if your legs are in any kind of shape. If they aren't, smaller CR's will make no difference. Save your money!
07-14-02, 11:38 PM
A 44 x 12 highest gear would be rather easy to max out, too. I use a 46 x 11 on my touring bike and I wouldn't want anything lower than that.
Are you running into stiff headwinds, is that the motivation for lowering the gearing perhaps?
07-15-02, 03:00 AM
Oddly I put a 48/38/28 crankset on my MTB for road work, but it's low enough off road, so should be fine on a tourer :confused:
07-15-02, 03:06 AM
38 and 48 are good for touring.
Can you take your granny gear down a tooth or 2 with your current crank ? I can fit a 26t onto my Campy road triple
If Shimano dont make a 26t (or lower) then look for one by Specialities TA. Better still, just fit the TA one, they are better.
The front mech should handle it OK.
07-15-02, 09:13 AM
Hey, there's a good plan :) The inner bolt-circle diameter is the 74mm size that many "full-size" triple cranks used until compact-drive came out, so there should be chainrings in 26 and even 24 teeth available.
Ok, am I seeing things, or does his signature say
Will mechBgon be at the 35th Hilly Hundred Weekend October 4,5 and 6, 2002 http://www.hillyhundred.org/ Indiana's Biking Adventure
Sorry, but I won't be there :(
07-17-02, 07:18 AM
I have Suntour chainrings and my bike shop says they don't sell parts in the US. Suntour has its own bolt pattern so I can't get a smaller granny gear. Thats when they suggested either going with a different brand chainrings(maybe with mountainbike gearing for ultimate touring) or going 9 speed and putting on a 36 cassette. Yes my gearing is great, but I can only ride 1 or 2 days a week and I don't sit behind a desk for a living. I like to load up and head out on vacations. Anyone who doesn't believe we have some steep hills here in Southern Illinois and Indiana is invited to come here to So. Il. for a spin across our Ozarks, or to go to the Hilly Hundred and brag as we are riding how easy it is for them:D
07-17-02, 11:37 AM
Now I'm a bit confused, because you said you had a Sora crankset in your first post. Is it a Sora-equipped bike but with a Suntour crankset, or :confused:
To simply put together a complete wide-range replacement drivetrain, you could get an 11-34T 9sp cassette, a DeoreLX crankset with 44-32-22 rings, a Hollowtech bottom bracket, 9sp DeoreLX derailleurs, a 9sp chain (I'm partial to Sachs), and 9sp STI or bar-end shifters. That would give you the same high gear you have now, but a low gear that is about 25% lower. That's like having about 2 1/2 more downshifts past the low gear you have now! :)
The parts listed are going to cost a bit, so perhaps we can also find out more about your present crankset, and determine whether it uses a common bolt-circle diameter that's interchangeable. I wish to heck that I had a Quality Bicycle Products catalog on hand... think I'll run down to the nearby LBS and ask them to order me the no-prices version for reference. I don't think there's any currently-available crankset on a quality-made bike that one cannot get rings for, unless they're riveted to the arms.
If you can find a precise model number on the cranks, or measure the distance between the centers of two adjacent chainring bolts on the inner chainring, I can probably nail down the bolt-circle diameter and suggest some chainring options. Combined with a new 11-34T 8sp cassette, a Megarange derailleur such as DeoreLX, and a new chain, you could get some of the improvements for a fraction of the cost of a full-blown upgrade.
07-17-02, 01:07 PM
TA make rings for just about any BCD. (Bolt Circle Diameter)
07-17-02, 03:34 PM
All I know is I have a new Motobecane Mirage thats listed as having Sora.Thats what the rear derailleur is anyhow.As for the Suntour crankset my LBS said that was common on Sora bikes and showed me several new Treks that were set up the same way.Anyway I just want to put on a ATB 8 speed crankset.I just mainly want to know if it will fit on my triple bottombracket and if the stock front derailleur will shift it.I just rolled the dice and ordered a closeout Shimano STX crank for standard 94/58 BCD (Whatever that means?).If it doesn't work I only blew $25.
07-17-02, 04:59 PM
[i]Originally posted by hillyman
I have Suntour chainrings and my bike shop says they don't sell parts in the US. Suntour has its own bolt pattern so I can't get a smaller granny gear.
I think that your bike shop is mistaken about the bolt pattern in this case. Only the Suntour MicroDrive aka 'Compact' cranks (for mountain bikes) had a different bolt circle diameter than Shimano (Suntour's 94/56 was actually the standard until Shimano came along with 94/58). Even then, you could seek out an Avid MicroAdapter to convert it to use 58T rings which are widely available.
However, your cranks are almost definitely Standard (110/74) and 24 or 26 tooth chainrings are still available in the 74 mm BCD though they may have to be ordered, either by your shop or by yourself. You can verify this by measuring two adjacent outer bolts - if they measure about 65mm (about 2-9/16") then you are dealing with 110. I am quite sure nobody ever made a 110 crank with a granny less than 74 but if you want to be certain, remove the crank and check the inner BCD. Two adjacent bolts will measure about 44mm (1-11/16").
The only other possibility is that it is a low end crank where the rings were all riveted together and in this case your shop is correct, you will need to replace the crank to change the gearing at the front.
Thats when they suggested either going with a different brand chainrings(maybe with mountainbike gearing for ultimate touring) or going 9 speed and putting on a 36 cassette.
I think you mean 34. This will make some difference, but not quite as much as reducing the granny by two teeth. If you do indeed have 110/74 cranks KEEP THEM as they are by far the most versatile, especially for touring, and current Shimano mountain cranks use yet ANOTHER 4-bolt 'standard' to make life more difficult for the aftermark industry. Changing to 9-speed is no minor task and would be very expensive considering that there is little, if any, gain. Frankly, I would be suspicious of the motives of that bike shop.
Yes my gearing is great, but I can only ride 1 or 2 days a week and I don't sit behind a desk for a living. I like to load up and head out on vacations. Anyone who doesn't believe we have some steep hills here in Southern Illinois and Indiana is invited to come here to So. Il. for a spin across our Ozarks, or to go to the Hilly Hundred and brag as we are riding how easy it is for them:D
There is no need to justify your choice in gearing to anyone else. A 28/32 is not an especially low gear for loaded touring. I think a 24 tooth chainring would be adequate. If you decide to change to Compact cranks to get a 22T ring, the 5-bolt standard has 46T rings available. With an 11-32 on the back this would work well overall. I don't know about chainring availability in the 4-bolt.
07-17-02, 05:36 PM
I found a picture of the Mirage, and this could be a different year's model, but you can view it here: http://www.motobecane.com/moto_bigmirage.html
From the photo, I can see that the crank has the rings built into it. They don't give the specs, but I think you may need a shorter bottom bracket for your STX crankset. You could pick up a basic Shimano cartridge model for as little as $15-$20 at the LBS, along with a Park Tool CCP-2 or CWP-5 crank extractor (http://www.parktool.com/tool_indexes/catindex_crank.shtml) and a BBT-2 bottom-bracket tool (http://www.parktool.com/tools/BBT_2.shtml) for the bottom bracket, if you need them (and an 8mm allen key).
If you can swing $25 for a Shimano UN-5x (UN-51, UN-52) bottom bracket, they are much smoother and should last proportionately longer too. However, if the resulting gearing layout works well, you might want to consider it an interim solution while you save up for a DeoreLX-level 9sp setup, at which point you would need a new bottom bracket again.
Good luck with the project, let us know how it goes! :)
edit: as a general guideline, if you put your new STX driveside crank onto the existing bottom-bracket spindle and tighten it down, the inside face of the small chainring should be approximately flush with the outside face of the bottom-bracket cup, as you look from above. If it's outboard too far, more than perhaps 3-5mm, your front upshifting may suffer and other problems may surface too, such as the chain falling off the middle ring when you're in low gear in the back. Hope that helps :)
07-18-02, 05:37 PM
THATS MY BABY,or as I call her, Crow. Thanks for the info! I didn't notice the Suntour gears are 'rivoted' together.I'll be darn.I've got a Nashbar Big Tool Kit(I love tools!) and a Bicycle Maintenance and Repair guide.The guide maybe a little outdated cause it shows a lockring style bottombracket like is on my old Diamondback hybrid. I grew up around my Dads auto garage and have worked on cars all my life but don't know much about bike repair.I want to do it all except maybe truing..Are the crankarm fixing bolts lefthand bolts?The book doesn't say.
No. The crank bolts are standard, but the Pedal bolts are Left handed as is the bottom bracket on the ChainRing side. All else is standard.
07-18-02, 07:23 PM
To be precise, the left-hand pedal has left-hand thread, right side is right-hand.
If you have that tool kit you should be set. The cartridge-bearing bb's are pretty easy to install. The spindle cartridge usually incorporates the driveside cup these days, and the other cup supports the unthreaded end of the spindle cartridge. Good plan of attack is to grease everything, thread the spindle cartridge in halfway (usually it's the drive side these days), then get the cup started about 10 threads on the other side. Now run the spindle cartridge in until its flange hits the frame, torque it firmly and then run the cup in the rest of the way on the other side.
If your existing bottom bracket works out, that would be even nicer. Good luck! :)
07-24-02, 04:08 PM
Hey all, I got my crankset from Nashbar today.I put it on and it was way to far out. Tried shifting and the front derailleur worked great shifting from the smallest to the middle ring so I figured I won't have to replace it. Drove to Carbondale and picked up a UN-52 bottombracket.You were right,it is a lot better quality than the stock.Put it together as soon as I got home.Works like a CHAMP! I don't think I will even need to take any links out.Didn't even have to adjust the derailleur. I can't wait to try it out on a big hill.THANKS for the help:D
07-24-02, 04:16 PM
07-25-02, 05:54 PM
No, lovemyswift will not be at the Hilly Hundred. Too many people. Besides, we rode that area on TriRi back in June. I will be at the Old Kentucky Home ride in Sept. Some good climbing on that one too!
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