Sprayman

likebike;
Thanks. I'm beginning to think this Diamond Back would require a bit too much tweaking to convert--long stem, raised seat, etc. I think I should just hold out for a bigger frame. Fortunately, there are a lot of old rigid frame MTBs looking for a good home.

Sprayman

frantik

yeah i'm glad old mtbs have managed to avoid the price inflation that have hit road bikes big time. Can still find top of the line mtbs for $100 or less around these parts. There's 9 mtbs in my apartment right now, all with Deore or better components, and only the carbon fiber one did i pay more than $100 for

likebike23

No problem. I think WRK101's advice is a good rule of thumb for picking a conversion candidate. I ride a 15-16" MTB and a 21" road bike, so when picking a conversion bike I shoot for 18-19" frames.

wintermute

Keep in mind that alot of MTBs have a llloooonnnnnngggggg top tube, so if you go for a larger frame, you may be stretched out. I've been planning out my drop bar conversion for a long time, involving multiple reads through this thread - notice that a lot of the bikes have alot of seat post and alot of stem sticking out. I've been doing alot of geometry calcs on my proposed build-out and it's definitely going to involve alot of tweaking and finagling. Right now I'm trying to decide between the shorter, 26mm Dirt Drop stem and the longer, 25.4mm Dirt Drop (and the 80mm and 100mm extension options on both).

himespau 

Is there a source for new dirt drop stems, or are these just a "as they come up on the used market" kind of things. I have a new build up of an older conversion in the queue (originally used a soma hi-rise threadless converter and a threadless stem, but would like to go quill this time), and currently plan on using a nitto technomic, but am trying to figure out what to do if that doesn't give enough rise. It's a ways down in the queue of projects (both bike and other), but am wondering if I should start keeping an eye out now.

Edit: answered myself with a little google. Looks like they're still for sale, but only in 80-100 mm. Bummer, was looking for something longer as the height pushes the stem back so far. I guess I'll just hope my technomic is tall enough.

frantik

yeah with a long top tube you may need a short stem which could make things "twitchy".. it all depends on the bike and the person though. It also depends on the bars. Some dirt drop bars have less extension in the drops compared to road bars

The main thing as far as size goes, as other have said, is you gotta get the drops up high. A smaller mtb isn't going to work with most stems. I recommend going one 1" up from the "medium" size mtb you might ride

kaliayev

I've been seriously considering doing one of these conversions for a dirt road/winter bike. Instead of using 26" wheels I was wondering about the possibility of using 650B wheels. Having never owned a mountain bike is this even a possibility with out doing major modifications?

Darth Lefty 

Out of sheer perversity, or is there a better reason? This would seem to negate many of the advantages of starting from a mountain bike in the first place, especially the cheap parts, universally available tire size, and the huge clearance for fat tires and fenders.

neo_pop_71

Hey kaliayev,

To avoid a long response to your question, I suggest reading this write up from a few months ago on BikeRadar, it addresses the 26" to 650B conversion you're wondering about.

Here is the link:

https://www.bikeradar.com/gear/articl...to-650b-36241/

kaliayev

Well if I do this it will be with a frame or frame/fork that I will build up. I already have a set of 650B wheels. I also don't plan on using really wide tires, probably 42 or 45s. Most of my riding will be on the street with some light gravel road use.

Thanks for the link neo. Seems like the biggest issue is with suspension forks which I have no intention of using.

avzay66

I may be interested in building one of those for my winter commute.

How much heavier are these vintage mountain bike steel frames compared to mid-high range road bikes? I am looking for bike to not become a boat anchor.

due ruote 

The Bianchi posted below (#2400) is a shade over 27#. I'm hoping it will drop a bit when I lose the knobby tires and steel bar. Some people have gotten their bikes below 24# but I think 26-28 is probably more typical.

gt eunuch

My bike (Giant Rincon 1 page back) weighs in at a SOLID 36.4lbs. Seatpost, stem, bars, are all steel and the frame is straight gauge chromoly.

LesterOfPuppets

Mine's about 24 lbs like this. Should be a little lighter now that I've gone to barcons and brake levers. It's a hair over 25 lbs with cheap 26" fork w/ long-reach caliper and fatter CX tires.


Untitled by Wheel Deals Vancouver, WA, on Flickr

I guess this is the only pic in CX mode, have to get more when I go back to that this weekend.

Sixty Fiver

The frame weights will actually be comparable if you match levels... the difference in weight between my handbuilt Moulden XC (23 pounds) and my hand built Proctor road bike (21 pounds) comes with the difference in the tyre weight.

Another place where weight gets added is in suspensions.

A nice mid to high level mtb frame will be made of some pretty lightweight tubes and if it is rigid the frame and fork will come in close to a comparable road bike... you might gain half a pound because of heavier gauge tubes.

WNG

LesterofPuppets, Nice bike, but what am I looking at?
We need a detailed write up of what you have built there. Very cool!

Sprayman

Wintermute;
Thanks for the comments. I suppose if I go for a larger frame (but not much larger) I'll have to keep an eye on the top tube, as I don't think being stretched out would be much more comfortable than being crunched up. I rode my old MTB tonight as it is, and came home with my hands hurting (and my daughter laughing because I look so damn silly on the thing). Even when I raise the stem on it (pre-conversion), I think my knees will still be close to hitting my elbows. It just feels too small.

There's one bonus to such a small frame, though. I took it out on the local pump track tonight for the first time and had a blast. Too bad I break too easily and heal too slowly now to really thrash around.

Sprayman

Sounds like good advice. I don't want to convert the bike I have now and not enjoy it.

neo_pop_71

Hi Sprayman,

My buddy frantik is spot on about the twitchiness of a short stem if the frame has a long top tube. I'd like to add that if your frame has short chain stays, the shorter stays cancel out the twitchy steering. I've built a number of dirt drop conversions and all but one used a threaded headset and a tall quill stem. For the most recent build I was after the classic dirt drop feel but I wanted to do so with a more modern threadless set up. I went with an uncut threadless Soma Cross fork and a short Azonic stem to achieve the same height and reach of a Nitto Dirt Drop quill stem. The 1990 Nishiki Ariel frame I went with was perfect for the task because the virtual chains stays are very short. So, even though I have a stubby stem, I have no twitchiness in the steering. Going on the idea of shorter chain stays, I would for a late 80's to early 90's frame and avoid the early to mid-80's ATB/MTN frames that will have long chain stays and slack geometry. Compare the difference in distance behind the seat tube to the tire on the 1982 Stumpjumper I picked up awhile back with the 1990 Ariel I used on my dirt drop conversion... the gap is almost twice the size. All these characteristics combined are going to have a major impact on the steering and handling of the bike.

EKW in DC

The sidewall issues I had were tears where the bead and sidewall come together. I had this on multiple tires. There was no brake rub there to cause that, and the tires were never overinflated. I thought it could be something else that was not the tire itself, but I tried hard to rule all those things out - rim, rim compatibility, brakes, overinflation, tire installation...

Mind you I've been through many other tires on my old bike, and never had similar issues. I had this issue on this bike on two different rims - a Mavic and a Sun Rhyno Lite, so I think I can rule that factor out too.

I am a Clyde so maybe the extra weight/load on the tire is responsible, but I hadn't had issues at the same weight with sidewalls on my old 700c bike and my weight isn't going to change overnight so...

So far (two weeks, 150 miles commuted), my new Schwalbes are holding up fine. If they end up having a similar problem I'll retract my negative comments about the Michelins. But given the reviews of others who have had the same issue, I'm inclined to believe it was the tire's fault.

I'm glad you like the build. I'm kind of partial to it myself too. :-)

Hope the Michelins work for you. Despite my and similar problems they're generally well liked judging by Amazon reviewers.

Paramount1973 

Many older mountain bikes have slack headtube angles, 70 degrees or even less. I don't see how you are going to get to 'twitchy' on these as opposed to a road bike with a 73 or 74 degree headtube. My Schwinn High Plains has a 70 degree headtube and even with a short, upright stem the thing steers like a truck. Unless you are using real short reach drop bars, your hands on drop bar hoods or in the drops will be at or beyond where they would have been with a stock stem and flat bars. It's the length of the reach on the bars plus the stem that matter. With my next conversion, I am looking for a bike with a 52 or 54 cm top tube. I have lots of choices for raising the seat and the bars.

EKW in DC

thanks neo_pop! Is that Bridgestone you posted a pictures of yours? Looked nice.

RFC

+1 Like it. What is it?

BTW, what size wheels are those and what are the CX tires?

Thanks

LesterOfPuppets

Thanks. I wish I knew what it is. It was sitting in the shop here for a while but has part of a brake arm stuck to one of the canti posts. I soaked it with PB Blaster and tried to twist it off but had no luck. While digging for a long reach BMX caliper I spotted a MTB wheel I had with wasted rim but LX hub with low miles and thought maybe I could just put some long reach road calipers on and lace a road rim to that wheel.

Bottom pull derailer cable run had me thinking more road parts should go on this frame, so roadie derailer installed. Then I tried a Chorus crank on the first BB I found (dunno what spindle width it had) and the chainrings cleared so that had to stay on.

I thought it was a Marin for a while cuz I remember their bikes with that nickel-plate-looking finish and they seem to have similar headtube lugs but I've found no Marins with stays that slender, so frame is a big question mark again.

A little while ago I gave away my RSX 7-speed brifters thinking I had some working 8-sp ones but nope. The right one clicks great but doesn't pull cable So now I've got some generic brake levers and Suntour barends shifters.

So here's a general parts list:

Mystery nickel plated CrMo frame
Cheap Dimension 26" w/ RSX100 long reach caliper
700c Dimension fork w/ Suntour Cyclone caliper
Front: unknown hub/Mavic Open 4 CD rim
Rear : LX hub/Mavic MA rim
Campagnolo Chorus Cranks 53/39
Suntour barend shifters.
Suntour BL Front Derailleur
Shimano Alivio Rear
VO headset
VO Tallstack stem
ITM Visia Bars
Thomson Seatpost
SDG Belair saddle

Pedals vary between Suntour Cyclone w/clipsnstraps, Shimano 520 SPDs, Odyssey Twisted BMX platforms.

Wheels are 700c. CX tires are vintage Conti 38mm up front and Kenda Kwik 320G in 30mm out back.

Sprayman

Neo pop;

Wow. Thanks for the time and effort it took to write that post. Your technical expertise obviously surpasses mine. I'm really just a hack that tends to get himself in over his head (but has a lot of fun doing it).

So let me ask your opinion on a particular bike. Locally, there's a Trek Antelope 830 for sale, dirt cheap, but it looks to me like it has a long top tube. The gap from the rear tire to the seat tube doesn't look as far as the gap on your Stumpjumper. If you were looking to do another conversion, would you bother with an Antelope?