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A few mtb/road compatability Q?'s(15 posts)

A few mtb/road compatability Q?'stimfire
Feb 22, 2003 6:22 PM
1. I know this has been asked before, but I had some trouble finding the answers with a search, so here we go again: Will mtb derailers work with STI/road shifters?

2. Will road cranks work with a mtb BB? I ask because I will be building up a mtb bike as a commuter for my fiance and I want to put some 165 cranks on the bike. So if someone makes 165 mtb cranks, that will work as well. (This question is unrelated to the first.)

Thanks in advance!

--Tim Kleinert
re: A few mtb/road compatability Q?'sbludoggy
Feb 22, 2003 7:36 PM
1. Yep. provided its all 9 speed or all 8 speed, etc.

2. yep. provided its all octolink (spined) or all square taper (standard).
re: A few mtb/road compatability Q?'srussw19
Feb 22, 2003 7:51 PM
Tim, as long as you are not using a Dura-Ace Sti Shifter, it will work. Dura-Ace shifters only work properly with Dura-Ace derailleurs (If I remember right it has to do with the angle they set the parallelogram on the derailleur, so the shifters don't work properly with other groups) but a Shimano Ultegra Shifter will work with any of the mountain derailleurs (provided you don't mix 7, 8, or 9 speed parts up with each other.) That's how cyclecross setups usually work.. road sti shifters with either long cage road, or mountain derailleurs.
As for the second question, the answer is not a simple one. If you use a mountian BB and road crank, chances are you will have a messed up chain line. It will throw off your shifting. Maybe not enough that you will care, but it will affect it. If you know you are using a road crank for sure, your best bet will be to match the bottom bracket to it. Otherwise you may run into problems with your front derailleur not being able to function properly and your chain to run an extreme angle on the rear cluster causing excessive and premature wear. If you mate it to a road bottom bracket, you may save some of those problems, but it may work as you describe it. Shimano has an FAQ section on their website that should cover this question if you are using their stuff.
Dura-ace with XT or XTR - no problem...seyboro
Feb 23, 2003 6:26 PM
...for guys around here in the flats, anyways. Going to the mountains, most riders in our club use their dura-ace setups and swap the rear derailleur for an XT or XTR unit to allow 32 or 34 teeth as the lowest gear. Shifting is absolutely flawless.
re: A few mtb/road compatability Q?'sFORT-Cyclist
Feb 23, 2003 4:11 AM
1. yes, but not with V-brakes
road bike brake levers will work with v brakes!!!!!!the bull
Feb 23, 2003 6:33 AM
All you need is a v brake adapter.
You can find them for about 20 bucks.
this will let you use a non-linear pull lever with a linear pull brake.
road bike brake levers will work with v brakes!!!!!!FORT-Cyclist
Feb 23, 2003 10:15 AM
yes of course.
an adapter like this one:

but without that sti's don't work with v-brakes, as i said.
rear derailler no problem, but front derailler could bejiggs
Feb 23, 2003 7:40 AM
for a couple of reasons. The road derailler is specific to the road crank and the mtb derailler to that crank, even on the road derailler a double won't work well with a triple crank, depending on the difference from small to large ring. So make sure you know the crank type/size before buying the derailler. Also the chainline issue is usually spec'd by the frame manufacturer so once you establish this(usually 47.5) you get the spindle length that puts the crank on the right chainline.
If you have the stuff build it and see!the bull
Feb 23, 2003 1:42 PM
I think it will all work if:
1. your using 9 speed stuff.
2. you use the right size bottom braket to get you chain line correct.

I dont think 10mm or less (cranks) is going to matter on a commuter bike.Use what you have.
Thanks Seyboro!russw19
Feb 23, 2003 9:37 PM
I checked into what you said about Dura-Ace to XT/XTR compatibility... you are right and I stand corrected, it will work and seamlessly at that.
Thanks for the correction.
There are several crank issues.Spoke Wrench
Feb 24, 2003 7:03 AM
Regarding crank/ BB compatability:
1. With the exception of XTR, Shimano mountain cranks use different splines than road cranks. Consequently, they will not interchange.
2. Most mountain bikes have 73mm wide bottom bracket shells. Most rosd bikes have 68mm bottom brackets. The bottom bracket has to match the bike frame as well as the crankset. My QBP catalogue lists recommended bb spindle lengths for every crankset they sell.
3. Most mountain bike cranksets today use "micro drive" chainrings with a 42 or 44 tooth big ring. The arc on a road front derailleur cage will be wrong.
4. I've not tried to match an STI shifter with a mountain crank and front derailleur. I have gone the other way and had good results matching a mountain shifter with a road crank and derailleur. Many new bikes today come that way. Consequently, I assume the reverse would be true but, like I say, I've not done it yet.
sorry but I have to ask a question, on thejiggs
Feb 24, 2003 6:26 PM
statement that "many new bikes today come with mtb shifter and road crank and derailleur". Are you sure this is the case because I'm surprised at this.
Also the statement that most mtbs come with 73 MM BB doesn't sound right. Specialized changed a few years ago from 73 to 68 and any c'dale I've had had 68mm. I don't have any reason to be sure about this but would like to know from where your info comes.
Why do you ask?Spoke Wrench
Feb 26, 2003 10:19 AM
1. Mountain shifters with road cranks are found on most straight bar tandems, like my daughter and son-in-law's Burley and on many of the "fast hybrid" style bikes, like my wife's Specialized Crossroads Elite.

2. I've got better things to do with my time than to research every mountain bike manufacturer's frame specs., but I've worked on enough mountain bikes to be confident of the 73mm BB width. I will grant you that this is one of the things that I like to measure myself before I order a replacement part. I have encountered 68mm mountain bike BB shells, but I still think they are the exception rather than the majority.
don't get upset, that was an honest question, you saidjiggs
Feb 26, 2003 2:49 PM
that you see many bikes with mtb shifters and road cranks, and I assume you meant road crank/drailler with mtb shifters and I wanted to know more about it. I had trouble with my ultegra derailler and road crank with mtb shifter so went to the shimano SL-R440 flat bar shifters and it works ok. I wondered if the xt rapidfire would work as well because shimano says no,the throw is different for the 10/10 mtb crank vs the 10/12 road crank.
don't get upset, that was an honest question, you saidSpoke Wrench
Feb 27, 2003 7:33 AM
My wife's bike has LX shifters and a Tiagra front derailleur. I think that my daughter's tandem is the same, but I'm not positive because it's at their house and I can't look. I think that it originally came with Grip Shifters but they asked me to change them to rapidfire. I do all of the maintenance on both, and they both work fine.

I've heard that story before that you weren't supposed to be able to mix mountain shifters with road front derailleurs, but I haven't had any more trouble getting that combination to work than setting up a road triple using STI's.