Newbie wants safety - DT250 disc front project?

[Catbird]

I've been becoming increasingly enamoured with the stupidly fun '75(I think) Yamaha DT250. However, for practical street use, I think I'd be more comfortable with, among other things, a disc front brake.

I was convinced of the magic of discs when I did a conversion in the front-end of my old '65 Tempest last year over the summer. However, I realize this is a different kind of project, and understand the kind of differences it entails.

The idea I have in mind, therefore, is to replace the triple-tree and front wheel with those off of a motorcycle that has a front disc brake. This obviously means that everything is already ready to go, caliper brackets, disc, calipers, cables, et-cetera.

HOWEVER, I don't know what to look for when trying to find a compatible triple-tree. I did a couple searches on Google to try to locate similar builds, but was unsuccessful.
Is there some kind of universal compatibility between certain measurements, or are all fittings proprietary to individual bikes?

 

[Big R]

Check out the steering stem diameters:
http://www.dotheton.com/forum/index.php?topic=20951.0


Also, you can check AllsBalls site. Find your stem bearings and you can cross reference them to other bikes. Find one that fits with a disc brake and you can ask ebay sellers the stem length (if you don't feel like swapping stems).


Hopefully somebody can give you more/better details than that......

 

[Tim]

My suggestion would be to find a disc front end with forks in the same diameter as yours and run them in your stock tree. You'd have to deal with spacing issues potentially to center the wheel and move the caliper in/out to line with the rotor (and/or space the rotor off the hub if needed).

What diameter fork tubes do you have?

The other solution is you take your stock tree and do a stem swap. Take the stem off your stock tree and have it welded into the triple of the new front end.

There's a fork tube listing on this board - it's the topic at the top of the list. You should be able to see a list of compatible fork tubes, but I've never seen a cross-reference of triple tree compatibility - too many possible combinations.

 

[crazypj]

You can probably slide an 80's model Yam front end in there (XT 350 maybe?)
XR200 may fit as it has relatively small diameter forks.
You'll probably find most are too long though as twin shock DT had pretty short forks for an 'enduro' bike

 

[bradj]

No keep your triple tree. A dt250 has 34mm fork tubes the spread is a 3/8 narrower than a 75 rd350 which is also 34mm. so there is your fork tubes and front wheel. plus the rd forks are 28in the dt is 31.5in. less dirt bikeee. it will get you away from a dumb ass 21 up front. So being that you will be 3/8 narrower you could most likely run a 96 fzr600 320mm rotor. fzr rotor offset 3/8, rd rotor offset 7/8 the bolt patern is the same put a 1/8 spacer behind the rotor. make a adapter to move up an rd caliper. i have a rd and im working on a early dt at the moment so ive held and measured all the parts im speeking of, with a little tinkering it will work, 1 fzr rotor and a rd master and caliper will be more than enuff to stop ya
DTs KICK ASS!!! Good call

 

[crazypj]

Cool idea, convert it to Supermoto ;D

 

[Catbird]

I like that! "More than enough" is enough for me.

I'm gonna look into how feasible this is gonna be for me, as from what it looks like right now, any fabrication I'd have to do with bradj's solution is *probably* well within my capabilities.

Now, do I have to find a new front wheel with the disc on it, or simply a "blank" wheel on which to mount the disc?


((This is why I love you guys. Any other bike forum would have *instantly* flamed me along the lines of either 1. WHY U NO BUY REAL MOTORBIEK THAT HAVE BAJILLION HORSEPOWERS AND DISC BRAKE ALREADY U RETARD, MELT UR STUPID TOY DOWN FOR SCRAP AND POUR THE BURNING SLAG ON HOMELESS PEOPLE AND BUY GSXR1300, or 2. HOMG YOU DESECRATE SACRED DT250 THAT ONLY ANOTHER HALF-MILLION EXIST NEVER MIND THE FACT THAT YOU RESCUED IT FROM A BARN AND IT WOULD HAVE ROTTED INTO NOTHING ANYWAY))

 

[bradj]

Get a set of forks, caliper, front wheel off a rd250/350 and a 96 fzr600 front rotor. ( note you will use your triple trees all your changing is the fork legs.) The only real snag you may hit is geting rid if the 3/8 difference in un needed spacer and keep every thing centered i put xs wheels on my rd and ran into the same thing but there was enuff meat on the speedo drive that i could thin it a bit and cut the rotor side spacer down. Seems to fit fine