madscot13

I'm thinking of converting a mountain bike to a road bike. I know a little bit about bike mechanics after switching the drive train and converting the downtube shifters to brake/ shifters on my old trek 520. My inclination is to start with a trek 850 and change the drive train and shifters.


My big question to start with is how possible is this? I am new to new mountain bikes. Will I be able to fit a 9 speed cassette on a mountain bike from the early 90's? what wheel span do I need to fit a larger cassette? I might consider an internal hub if that would fit as well.

Does anybody have any caveats on doing this to a mountain bike? does anyone know a steel frame that this would work with as well?

For those who are questioning my logic, I would like a slightly smaller bike with 26" wheels. the surly I was looking at did not fit me too well- mostly because the top tube was really short. And overall, I was not very impressed. I thought for the cost of a new frame I could get an old mountain frame with a longer top tube and might fit me a little better from the get go and have a few hundred to spare for new parts. I love my trek 520- the components on it are perfect for me and the ride is pretty great, but I like projects and this sounds like a fun one.

thanks in advance

PJCB

You are going to come out with a frankenbike, but if its what you want to do, and you like projects, I'd say go for it.

You're going to get a lot of naysayers responding, mixing road and MTB in one bike doesn't mesh well with a lot of folks.

ThermionicScott 

It's very possible, but you'll need to do a lot of parts-swapping and maybe some frame-bending.

Shimagnolo

Mtn drivetrain with brifters can be done: https://shell.forethought.net/~ryoder...e-cross-v2.jpg

But note this is using canti's so there is no V-brake vs road-brake-lever issue.

jimc101

Few answers to your questions, and cautions

Can you fit a 9 speed cassette, yes if you currently have a 8 speed cassette, possibly if you have a 7 speed cassette, no if you have a freewheel; 8 speed freehubs can accept 7/8/9/10 speed cassettes with no issues, 7 speed freehubs will most likely need a new freehub.

If you are looking to buy / build a road bike today, would not consider 9 speed, as it's almost obsolete, and getting good parts is getting harder, where as 10 speed is much easier to find as Tiagra (4600) went 10 speed this year.

Internal hub gearing - that won't give you a road bike, not sure what you are trying to achieve with this. can you frame even accept this?

The biggest issue you will have will be the crank, you will probably find that you can't fit a road crank, as the chainrings will not pass / hit the chainstays.

Another issue is the shifters, an MTB frame doesn't have the required downtube routing, so you will have to resolve this somehow.

What ever you do, it will be a compromise, and will probably end up being as or much more expensive that just buying a complete road bike with compromises on component sizing and fit, if you are looking at Surly, the only road bike they do is the Pacer, and that is made as a 42cm frame, are you too short to fit that?

Puget Pounder

People have done it many times before. Some like it, some don't like it. I tried it before and I was not a fan. The geometry is pretty strange for drop bars so the bike is too sluggish to be a true road machine. They work well as fast trail bikes though.

madscot13

I guess I should have searched frankenbike and not conversion first. I've ridden the smallest sizes on the surly lht and I just didn't like it. I can't put my finger on it. It did feel sluggish but I am not sure if it was the components or if it was the frame or if it wasn't dialed in.

well the geometry on the 850 is different from the surly lht. Longer top tube, which I like, about a half degree off on the seat tube, less rake, which I don't like. I didn't think the half degree would ruin the ride. Do others think differently? I am sure someone does.

I'm really just looking for technical help.

fietsbob

I think you will find top tubes on MTB's are longer.. so stem has to be shorter with drop bars..

I have converted to Trekking bars, they work as a simpler touring adaptation of MTBs
because the tube is the same as MTB bars [1"center, 7/8" rest of the bar],
so you don't have to swap out the whole kit
Stem, bars, levers brake and shift, 4 cables, and housing, grips> tape, and all that..

brake levers can go on the inside rear center of trekking bars, slip right on.
with open face stems
you can take them out without disturbing the grip-sleeves or tape job,

useful in pre trip packing..

bobotech

I did it for fun and its well, fun. I did it first to a Trek 830 Mountain Track but the frame was too tall for me so I tore it down and rebuilt it on a Fuji Appalachian. I originally used 700c wheelset but the spacing problems in the rear were slightly annoying. The 700c rear wheel had 126mm spacing but a mountain bike is spaced for 135mm. I didn't feel like cold setting the MTB frame so I rebuilt another wheel. I had a 27 1/4 set that I wasn't using. The hub was old and a freewheel which I don't like. So I went an replaced the freewheel hub with a mountain bike freehub. It was spaced for 135mm. I also rebuilt the front wheel with a nicer newer front hub as well.

So I now have a nice set of 27 1/4 wheels with a 135mm spaced freehub in the rear and put them under the Fuji frame. I used a stem shifter just because I had it and it was cheap. I mounted it on a threaded to threadless adapter. It is now tight and works fine.

I am going to post some pics after they are uploaded to photobucket.

ThermionicScott 

Is this Trek new enough to have suspension? I would personally only convert a "hardtail" model -- they'll be more road-like.

bobotech

PJCB

That bike looks pretty sweet! Tough as nails, too?

dbg

I'm currently doing the same thing to a 1988 Trek 850. I'll call it a touring build and it will have brifters and slick tires. But the geometry is a bit more relaxed and stretched out than a road racer. Room for panniers, lots of rack accommodations as well. The 88 had 130 rear drops. If yours is newer it probably has 135 and maybe a suspension fork (I would not have suspension forks on road bike). I'm doing it from scratch --including a new powder coat paint job.

bikemeister

I've done it. I made my hybrid from an older 2003 Schwinn Sierra frame. Used 700c wheels, 35c tires, Huret deraillers, SRAM chain, a 7-speed Sachs freewheel and a double Sugino crank with steel rings. Friction shifting is no problem for me. More comfortable geometry of an MTB with less weight and complexity of road components. And using 700c wheels allows many choices of tires and widths.
Had to do some engineering to get the bottom pull FD to work on a frame set up for top pull, but, it works like a charm.

Retro Grouch 

"Early 90's" That tells me that it probably preceeds V-brakes and probbly preceeds top tube cable routing.

Assuming it's 7-speed you'll have to futz with the rear hub to make 9-speed work. The first thing that you should do is to measure the distance between your rear dropouts. If it's 135 mm. That's good. It means that you can buy a new freehub wheel with a 8/9/10 speed freehub body.

Straight handlebars and down turned handlebars usually have different clamp diameters so, if you are going to make a switch, you'll want to be sure your stem clamp matches.

Crankset/front derailleur/shifter needs to be thought through before you start buying parts. Mountain derailleurs don't usually work well with chainrings bigger than 48t. Indexed mountain shifters sometimes don't work well with road front derailleurs. Road front derailleurs need bottom pull cable routing.

Be sure to put a lock on your list. Reworked non-suspension mountain bikes are highly desirable for commuters. That makes them more theft prone.

Werkin

I suggest keeping it simple, purchase a complete 26 in. mountain bike, replace straight bar with Jones H-bar or full loop, adjust reach with longer stem if needed, taller seat post if needed, road tires, and largest outer ring that will fit. Depending on the BCD & spider arm, big ring tooth count my be limited. I have 7 speed on my conversion, that's not an issue. A drop bar is a hurdle you don't need to jump right away. You may or may not like the handling mountain bike geometry imparts at high speed; trail in particular.

MyBikeGotStolen

Bobo, thanks for the pics you uploaded! Is there any way you could upload some more detailed pics of how you attached the shifters to your stem?

I also did a mtn bike to road bike conversion (early 90's Raleigh, no pics right now). I used a stem shifter as well, and already had a threaded-threadless adapter, but couldnt figure out how to make it work. I ended up going with the stock mtn bike stem, and slooooowly bending it to accept the 26 mm road bars.

bobotech

Here you go

bobotech

The stem shifter I used was originally designed to be used inbetween the locking nut and the adjusting nut and washer for a quill style neck. It isn't the more common type that clamps around the quill itself.

It came off of a mid '80s Schwinn Traveler.

Kimmo 

IMO the OP should weigh up whether it's worth all the hassle to make something that'll be inferior to the 650c road bike he/she seems to really be after...

madscot13

thanks this was a lot of the information to look for. Also thanks for not hating on the idea. I understand it will be a big hassle and a money drain. But at least I am not looking to change the wheels to 700.

bradtx

madscot13, If you get out of the project what you want, then it's not so much a hassle. If you want a drop bar configuration the easiest route includes bar end shifters, handle bar, brake levers matched to brake design, a stem and bar tape. If you wnat integrated brake levers include a road group's FD. Most likely an 800 series Trek mountain bike from the early to mid '90s will have a 7S and possibly 130 mm spacing, depending on model year.

Many of these non suspension mountain bikes have been given a new lease on life with a commuter or touring rebuild.

Brad

DCB0

It is possible, but I would put a drop bar and drop bar levers on first to make sure you get an acceptable fit.

Also, I would go with bar end shifters. It might be tough to find 7 speeds, though. Friction shifters are always an option.
However, you could put a 10 speed road hub laced to a 26" rim, then the world is your oyster regarding shifters.

Ira B

This can work and be a good solution depending on you specific use and needs.

My commute is about 14 miles. When it will be daylight and the weather good I ride a road bike but for during winter months when the weather is bad and I'll be riding at nigh I wanted something more bullet proof and did a Mt. Bike conversion on an 80's Shogun.
Expect a lot stiffer ride and to run out of gears on the steeper down hills and a bit less overall speed as the trade off.

dave s

I did it on a early 90's trek 950. I used a Sugino AT crank, 48-38-28, 9 speed Tiagra brifters, a Deore RD, a Tiagra 4503 FD . the hardest part was trying to figure out a spindle length. i consulted S Brown's site, but after I bought 2 BB that did not work, just gave it to the LBS to find the correct BB. I had to convert the cable routing form a top pull to a bottom pull for the FD, just drilled and tapped a small whole in the BB shell to mount a cable guide. I could not find a top pull FD that would work with the 48T chain ring. worked like a charm, obviously the TT is longer and I used a much shorter stem. used as my winter bike till I bought a CC bike.