Bergz

I got a 1993 Trek 950 MTB in rough but sound condition a few weeks back. Paint gouged and rust appearing.
I stripped the paint and sprayed the bare frame with salt and vinegar solution to produce rust. Coated that with Tung oil.
I swapped the wheels, cranks, saddle and other parts from another MTB that the Trek was replacing. As I'm only riding this on trails and forestry roads I decided to lower the BB 25 mm by welding in another bb from the bike I was discarding.
This has turned out really well, the bb is the same height now as my road bike and it feels like I'm in the Trek rather than perched on top.
Looking forward to lots of trails on this.

TenGrainBread 

How do you plan on preventing the frame tubes from continuing to corrode until failure?

Bergz

They have been oiled on the exterior, you can see the sheen and treated with fish oil sprayed inside. I also live in a medium dry climate and the bike will be stored inside.

abdon 

Seems like a weird exercise to me. The entire frame geometry was dialed in around the bottom bracket being where it was, the fork rake was set taking that into account. Heck you'll be scrapping the pedals a whole lot more, those went down as well.

bark_eater 

Funny thing, I j picked up a Trek 750 frame yesterday, with the cantilevers moved to fit 26" wheels.

I had been considering doing this to a 750 frame I already had, and when I brought it up here, there was some consensus to just get a Trek 950, because the geometry's the same except for the bottom bracket height. Of course lowering the bottom bracket height was sort of the point.

So when a previously converted 750 come up for sale I went for it, saving a bit of time and money verses doing it my self. The frame I bought came with a different fork and maybe 5mm more rake, but the owner figured he had ended up with the same geometry as a Rivendell Atlantis.

Lots of ways to skin a cat, but grafting on a lower bottom bracket shell is impressive problem solving

Hobbiano 

Interesting with the road bike bottom bracket height. It would be nice to see, say weekly updates, on how the rust/ Tung oil surface treatment is holding up. What part of the country do you live in?

Jeff Neese

Seems a shame to destroy one of the more desirable rigid steel MTB frames ever made, just for this exercise. The fact that it's one of the earlier lugged frames makes it even worse. You turned a Classic/Vintage, highly desirable bicycle into scrap metal.

It would have cost $150-200 to have the frame media-blasted and powder coated. Then you'd have something worth showing off.

John Nolan 

Your bike, your time, not mine!

rccardr 

Not something I would do, but admire the inventiveness and ambition.
Please keep is informed regarding ride quality, road worthiness and how well the surface treatment holds up.

AdventureManCO 

I like it!

Bergz

Thanks for all the replies, I'm sorry for those I've upset...
In New Zealand old MTB have no value whatsoever and this Trek was destined for the steel furnace when "rescued". The local recycling center has 30+ old steel MTB's, many similar quality to this. They've been there months... I was quoted $650NZ to sandblast and primercoat, insane money as it needed a complete drivetrain replacement too.
The geometry has not been changed, what I have done is like going from 160mm cranks to 180mm cranks and lowering the seat to compensate. It's for trail/path use, not off road and will not get more pedal strikes. So far I consider it a great success, it's no longer "tippy" and feels much more "planted".
I'm not a complete bike criminal, I've restored many NZ manufactured racing bikes to as good as new condition.

dmark 

Why am I not surprised?

abdon 

I don't think you offended anybody, you do you. But if you went both 25mm lower on the bottom bracket and extended the cranks by another 20mm, that puts the bottom of your pedals 45mm closer to the ground. Clearance was a reason why mountain and trail bikes had the bottom bracket higher than road bikes, it just feel that you took the frame a big step back on that regard. I guess if all you are doing is flat gravel paths that will be fine but I have clunked quite a few things with my pedals while mountain biking.

nlerner

Wow, this takes gugificazione to a whole new level; @gugie needs to weigh in.

gugie 

Bergz

To be clear, only the bb was lowered, the crank length remains the same at 175mm. I did substitute a lower Q crankset from the Shimano LX with it's splayed out arms.

repechage

Why the forward oriented vent hole in the new shell? Was designed for venting to one of the main tubes, perhaps one is set to the internal gap.

SkinGriz

How long is the effective chain stay length?

SkinGriz

MTB tire size clearance with road bike BB height. I hear that’s the hot trend the roadies are transitioning to.

SkinGriz

I like the idea OK.
I think if you used that glass flap disc on the angle grinder to remove paint, you removed more metal than you realize.

smd4

The effective chain stay length in probably only a few millimeters longer. I agree, the main frame geometry is the same. Head angle the same, seat tube angle the same. Lower bottom brackets do make bikes feel more stable.

I spend a lot of time and effort trying to prevent rust, so the “finish” isn’t my style. And mountain bikes, lugged or otherwise, are of no interest to me, and they’re a dime a dozen anyway, so I have no problems with any modifications.

Hobbiano 

Say ten hail Mary's and you will be forgiven.

bark_eater 

Bergzing is the new Drewing... with brand new extra more fun added!

Bergz

So I'm forgiven then?
The tube vent hole in the "new" bb will be covered with a patch of heavy duty waterproofing tape, good spotting.

eeuuugh

The finish isn't my cup of tea, but bravo for doing something really weird. If you like riding it, that's what matters. This bike could go in the "the horror..." frankenbike thread.