Front disk brake possibility
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  1. #1
    Senior Member flyhunter3825's Avatar
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    Ive got 3 89 xt350s and one 85 xt350 Parts bike. I dont plan on needing the spare forks. Both the tw and the xt have 36 front spokes. Any ideas about how to get the right spokes? The hubs are different and the xt hub will be too small for the tw spokes (too short). The fork tubes are a tiny bit bigger so the tripples will need to be bored out, but thats minor. The xt forks have air caps and are 35" top to axle hole vs tw 30" top to air hole. Any input on this? mainly the spoke issue?

  2. #2
    Senior Member TW-Brian's Avatar
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  3. #3
    Senior Member flyhunter3825's Avatar
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    Good call, thanks!

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  5. #4
    Senior Member lizrdbrth's Avatar
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    I have an XT350. A swap this drastic wouldn't be my thing, but I did size it up once a long time ago.



    Devil's advocate stuff. Not trying to rain on your parade at all. Nothing mentioned below can't be solved with a bit of machine work, munny and creativity, but you may not have taken them all into account.



    If I read your post correctly you're proposing using the TW triples, XT fork legs and 21" rim on a TW hub:



    You're talking a 6" height increase up front, which will call for a corresponding 6" height increase in the rear, and a seat height upward of 36".



    Early XT350 fork tubes are "stepped". They're not the same diameter for their entire length but are larger where the tubes clamp into the top and bottom triples and smaller in between. IIRC the "fat" part is 36 or 37mm, a bit of a stretch for bored out TW triples. The "step" means they can't be lowered in the triples to shorten the front end. But even if you could the tire would then hit the lower triple on hard hits.



    Clearance between the disc and the left lower fork tube is kinda tight on the TW, but fortunately the lower tubes on the XT are only a couple of mm fatter. Only reduces disc clearance few mm's but may affect caliper centering. Not sure there's enough inboard/outboard movement in the XT caliper.



    The XT caliper mount is set back 5mm further than the TW, so you can't use a TW disc. The XT brake disc is 10mm larger in diameter than the TW and has a less effective, single-puck old school caliper. But I think the XT disc bolt pattern is the same as your TW hub, so it may not present a huge issue. The two-piston TW caliper can not be made to fit on an XT350 fork leg, nor can any two-pot caliper I've been able to find, so you're effectively stuck with the same braking as the TW. No better, but probably no worse.



    The axle diameters are different. A bearing swap may or may not correct this, but where you gunna find an axle that long?



    The axle support castings are wider on the XT lower tubes. New shorter spacers should solve it, but the speedo drive will no longer fit. There may be slimmer ones but I think they're all pretty much identical except for the axle hole.



    You'll need new steering stops welded to the neck.



    Then of course there's the price of custom spokes, etc.



    If you can live with the height increase and feel that you need all that travel the complete XT350 front end is almost a bolt-on. It uses the same headlight mounts and front cowling and all your TW instruments will bolt right to it. The only issues you're likely to face are the steering stops and the fact that that it will probably bang the tank at full lock. Prolly a lot less work involved for the same result.



    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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  6. #5
    Senior Member joeband's Avatar
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    Quote Originally Posted by lizrdbrth View Post
    I have an XT350.



    Devil's advocate stuff. Not trying to rain on your parade at all. Nothing mentioned below can't be solved with a bit of machine work and creativity, but you may not have taken them all into account.



    If I read your post correctly you're proposing using the TW triples, XT fork legs and 21" rim on a TW hub:



    You're talking a 6" height increase up front, which will call for a corresponding 6" height increase in the rear, and a seat height upward of 36".



    Early XT350 fork tubes are "stepped". They're not the same diameter for their entire length but are larger where the tubes clamp into the top and bottom triples and smaller in between. IIRC the "fat" part is 36 or 37mm, a bit of a stretch for bored out TW triples. The "step" means they can't be lowered in the triples to shorten the front end.



    If you use the TW tube spacing (triples) and fatter tubes the distance between them at the axle will be about 4-5mm narrower than a TW hub by virtue of the tubes, the axle lugs on the lower tubes on the XT are wider and the lower legs are fatter, narrowing the space between tubes further. This can be cured with custom spacers, but you'll lose the TW speedo drive. There won't be room for it. The XT drive may have a slimmer casting. Can't remember, but that may be a solution.



    The axle diameters are different. A bearing swap may or may not correct this, but where you gunna find an axle that long?



    The XT caliper mount is set back 5mm further than the TW. It's brake disc is 10mm larger in diameter than the TW and has a less effective, single-puck old school caliper. The two-piston TW caliper can not be made to fit the XT lower legs nor can any modern caliper that I've encountered. The disc has the same bolt pattern as your TW hub, but may be too close to the fork leg for caliper clearance once you're done.



    You'll need new steering stops welded to the neck.



    Then of course there's the price of custom spokes, etc.



    If you can live with the height increase and feel that you need all that travel the complete XT350 front end is almost a bolt-on. It uses the same headlight mounts and front cowling and all your TW instruments will bolt right to it. The only issues you're likely to face are the steering stops and the fact that that it will probably bang the tank at full lock.


    mr lizrd,

    i've never ceased to be amazed at the insight you have into motorcycles in general and tw's in particular.

    ride on sir!
    1994 TW226- 6spd. 10w-40 synthetic, XTHidden Content , XT225 stainless header, +2" Joemama swingarm, lizrd cooler, +20% fork springs, +25% rear spring, 2001 speedo w/ trip odo, pro taper atv bars, bark busters, shinko 241 front tire, front fender w/ mr bracket bracket, Hidden Content , o-ring chain, ricochet skid plate, Hidden Content , XT225 rear brake cam lever, folding-tip shifter, cycle rack, kolpin 1.5 aux tank & 1450 pelican case. Hidden Content or Hidden Content

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  7. #6
    Senior Member flyhunter3825's Avatar
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    Damn. Ur right, i forgot about that stepped tubing. I was gonna lace the tw rim on the xt hub and go that route but the forks would still be an issue. I have an 89 tw so any disk is better than that lazy drum brake. Maybe i can fab the spare xt tripples i have to be wider for the fat tire up front? Ive got the rear banshee or blaster shock that makes the rear sit up high, so i kinda wanna level it out. The rake on this bike is pretty ridiculous but i like the rear height.

  8. #7
    Senior Member flyhunter3825's Avatar
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    For such an odd bike, this is the best forum ive ever come across. The knowledge, availability, and rapid responses is unbelievable.

  9. #8
    Senior Member lizrdbrth's Avatar
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    Quote Originally Posted by flyhunter3825 View Post
    I have an 89 tw so any disk is better than that lazy drum brake....


    Mark Twain did a few frontend swaps and came up with the following quote:



    “Good judgement is the result of experience and experience the result of bad judgement.”



    I ain't no smarter than the next dude, I've just done a few swaps.



    I'll let you in on a little secret, since all you've known so far is a TW with a drum.



    The disc is no better. It just feels "grabbier" because it lacks modulation and takes less hand effort. Doesn't stop any shorter in the real world, eats tires quicker on pavement and even adds a few pounds to the bike.



    With the possible exception of wet brakes after water crossings you ain't missing a thing.



    I own both.



    YZ tubes won't add travel but they'll level it out in less than an afternoon's work and can be had for as little as 25 bucks if you shop around. You may or may not need a longer brake cable. I've never done the swap on a drum frontend.



    I hadda rewrite my post up above cuz I gots my eyelids propped open and was using screwy math. You guys were too quick on the button. lol.



    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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  10. #9
    Senior Member r80rt's Avatar
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    I have a disc, and I'd rather have a drum. The drum gives me a better feel on the gravel roads that I run.
    Only a fool would attempt it, and God help me, I am that fool!

  11. #10
    Senior Member joedirt1970's Avatar
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    I am sure there are plenty members out there that would trade their drum for your disc.
    Hidden Content [/IMG]It's not why, but why not. Do it for the right reason now, versus the wrong reason later.
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    2008 TDub--Jimbo Shield, Lizard Oil Cooler, Blaster Shock, YZ Hybrid Forks, Supermoto front fender, ATV Bars, Acerbis Brake Cover, 1460 Pelican Case, Cycle Rack, Power Core, Gold Chain.

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