Road Cycling - mtb derailleur on a road bike?

Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.



PDA

View Full Version : mtb derailleur on a road bike?

asterisk
05-19-04, 09:50 PM
sorry for the newb question, bu i've seen plenty of road bikes spec-ed out with a road front derailleur but a mtb on back.

why do this? does it cause the ride to act any different than if a road derailleur were back there?

Fixed Up North
05-19-04, 09:56 PM
A mtb derailleur might come in handy if you had a big cog in the back for hills. Other than that, the ride quality should be the same.
CRSO
05-19-04, 10:04 PM
A mtb derailleur might come in handy if you had a big cog in the back for hills. Other than that, the ride quality should be the same.

Big cog sounds right here. They are different though. Compare two of them side by side.

asterisk
05-19-04, 10:42 PM
the machine im talking about here has a Deore rear on a HG-50 8-Speed 11-30t cassette, to put it in context.
Raiyn
05-19-04, 10:55 PM
the machine I'm talking about here has a Deore rear on a HG-50 8-Speed 11-30t cassette, to put it in context.
That's typically a MTB cassette gear range so yes the MTB dérailleur makes sense due to it's longer cage.
Al.canoe
05-20-04, 06:29 AM
Normally one would use a mtn Bike derailleur to cove a large range of cog diameters. I use an 11 to 34 XT cassette on my road bike with an LX der. Same goes for the front. I use 22/32/44 chain rings so I use an XTR mtn bike front der. Works very well with STI's.

The original road 105 der did work, but not as well as the XTR.

Al
capsicum
05-20-04, 11:54 AM
Is it a double or triple crank? Most slack comes from the major size difference of the 24t-50t chain rings as far as slack adjusters are concerned. The rear derailer its self may need to take a different path as it moves side to side because of the steep slope from smallest to largest cog. The Rear derailer doesn't just move side to side it also needs to go up and down to approximate the slope of the cogset. road =shallow, close ratio; mtb= steep, wide ratio.
You could mix em to fit the situation if nessesary, with a short road style slack adjuster on a mountain rear derailer if you had a close ratio double crank and a wide ratio cogset and wanted to save a little weight and clearance. Or a road style rear derailer with a long slack adjustor for a close ratio rear and a triple crank. Note I haven't tried these combos its still theory so don't come to me if it dosen't work.