Bicycle Mechanics - Triple chain wheels
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I am looking to install a triple chain wheel on my old road bike. The frame is a custom 531 db sport tourer built around 1980 and I think it has an english bottom bracket. My thoughts are to rob a crankset off of a mtb to install on my road bike. Will any of the mtb cranksets interchange with my current crankset? I have been away from cycling too long so the technology has passed me by.
Thanks for your help.
06-17-08, 07:37 PM
If you got a double crankset on your bike, chances are you'll need a longer bb as well. Select the crankset, and it'll tell you what length bb goes with it for the correct chainline.
THen you can measure your current one and determine if you need a new one or not.
Now that seems to be a fair enough offer and I appreciate it. Thanks
I am going to do the same thing. I put the triple on one old road bike and when tightening the cranks onto the spindle it had a wierd feeling like the spindle had a different taper than the crank arms. Today I plan on taking the triple and transfering it to the road bike that fits me and that I ride most of the time. It only takes a few minutes to make the transfer and then you know if the chain line is acceptable. If everything looks good I may even rob the long deraileur off the mountain bike.
You may, or may not, have trouble with the front derailleur. To many unknowns to say definitively at this point.
MTBs and road bikes have different length hanger tubes (where the BB screws in). MTB is 73mm and road is 68mm. Yours is almost certainly 68mm. MTB cranks often have to clear much wider chain stays as well.
Look for your new crank among road cranks.
I got the triple installed. The chain line looks ok but the front deraileur will have to be swapped as well. The road deraileur can't be setup so that it wont rub the chain when either in the small ring or in the large ring. I got it setup to work in the small and middle ring so that I can go out and give it a test this afternoon.
06-18-08, 01:50 PM
The curve of the cage on your road derr will likely be to suit a larger outer ring. This may give you problems when mated with a MB triple which has a smaller outer ring.
The curve on the road FD did not fit the smaller chainwheel very well and the distance between the deraileur plates was close together compared to the FD on the mountain bike. This causes more chain rub than I like and causes more trimming of the FD than I like. So I put the FD and RD from the mountain bike on the road bike and now things are much better. The mountain bike FD cage is much longer than the road bike FD cage. When I set the heigth of the FD I got it as low as it would go without hitting the chainstay. Now my final test will be riding for a few weeks to see if I am going to have any chain drop problems.
I am very pleased with the new lower gears that I now have. I now have a 1:1 ratio as the lowest gear and I can now maintain 5.5 mph on some of the hills that previously slowed me down to 3.5 mph. Also my heart rate stays in a much narrower range now since I am not having to push so hard.
06-19-08, 04:56 PM
"When I set the heigth of the FD I got it as low as it would go without hitting the chainstay"
I assume you meant ring?
If it shifts fine, you're good to go. If it doesn't, don't be afraid to try moving it up a few MM.
My brothers 10 speed simply won't "digest" the "correct" setting. I wondered why it came from the factory set too high! Because it works!
No Bill the FD could not be moved down low enough to touch the chainring. The bottom of the deraileur cage hit the chainstay before it would hit the chainring. So I set it up with the bottom of the cage about 1/8" above the chain stay which leaves it about 1/4" above the chainring. If I have the chain dropping off of the large ring when shifting I will have to do some more adjusting. Everything is working great on the work stand so unless the road test shows problems I am good to go.
I want to thank all responders to this thread. I cheesed out and took the bike to "The Wheel" LBS and asked him to do the triple deed. Considering the current chain rings, he asked me if it would be OK to use a mtb crankset which would allow some smaller rings than the typical road triple so I said sure. He is also going to put a sealed bb to replace my old non-sealed one. I should be able to climb these hills now even with these old, out of shape legs.
I just did the conversion you described. It worked fine for me crossing parts with different era, different brands, etc. The derailure was a challenge, of course.
Your LBS should have fun with it. Glad to see you are getting the hardware put on. Of course, it would have given you great satisfaction if you could have done it yourself, but hats off to you for giving it a try and following through with your LBS.
I did the original frame up build including building the wheels. Many changes have taken place in the technology since I last rode so I just was not sure what parts might work together and for the few dollars that lbs is going to charge it just didn't make sense to do it myself. It even seems that there are some different tools required in this modern day. The LBS even thinks that he can make my old neuvo record rear gear changer work. I hope so since it works so well but I am guessing that it will need to be changed out along with the front gear changer. Just for my information, what bb did you use?
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