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Weight savings of disc brake swap to XT500?

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How much weight can be saved with a disc brake swap to an XT500 w drums?  My front/rear weights are a staggering 138/198. 

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How much weight can be saved with a disc brake swap to an XT500 w drums?  My front/rear weights are a staggering 138/198.  I'm so depressed.  

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You  would save more on the back.  my xr500 front wheel and brake was a grand total of 4 lbs heavier than my barnes hubbed replacement.   I think the disk I have on the front of my champion framed xl350 is heavier with a pirelli 19 on it.   I think your biggest savings is on the back.   This is vintage Hurst and Grimeca stuff I am talking about.   The yamaha wheels seem light compared to my cz.  

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It's a swap to the back I'm talking about.  My front wheel is a spool but I meant swapping a disc set up to the rear to replace the massive drum.  

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Those XT's had a pretty heavy damped setup.  Even a tt wheel is lighter.  There are lots of mx hubs,  but something like the barnes etc like I have been using (man talk about something that is scarce now) are lighter.   I haven't done it yet,  but I am going to try an mx wheel and disk.   I have a couple of C and J frames that I plan to put engines in,  and it just seems like all those motocross wheels I have should be doing something.  Way back,  we put a yz drum hub on a tt500 that my friend rode on the ice for years.   That one had a cut aluminum swingarm from the same donor bike that the wheel came from.  We put shock mounts on it.  

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YZ hubs and wheels may be the ticket to making my fat lady XT more balanced.  A lighter gas tank would help - undamaged stock tanks are bringing a pretty penny.  A metal tank comes to mind for fire safety but MXers have plastic tanks and they crash too.  So is a plastic tank an option for flat tracking?   Two laundry baskets and my lying bathroom scales should tell me the weight differences on disc vs. drum set ups as well as Akront vs. YZ wheels, hubs, etc.  Post it here if anybody has done any work on this.  

Update: Stood on my digital scales this morning, it read OMG and went blank.   

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If not already addressed, there's lots of over-engineered heavy steel parts on the back end of those XT's to modify; fender, axle, axle nut, wheel spacers, chain adjusters, footpeg bosses on swingarm, turn signal brackets, brake actuating arm, etc. There's a write-up of a modified '76 TT500 in the March issue of Dirt Bike. Maybe some ideas there.

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The XT wheels are pretty heavy.  The TT500 wheels and similar year YZ wheels are the same wheels. I run a TT500/YZ250 rear hub laced to a 19 X 2.75 Sun rim. With a Dunlop DT2 front tire on the rear end.  

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14 hours ago, 76xtdrvr said:

If not already addressed, there's lots of over-engineered heavy steel parts on the back end of those XT's to modify; fender, axle, axle nut, wheel spacers, chain adjusters, footpeg bosses on swingarm, turn signal brackets, brake actuating arm, etc. There's a write-up of a modified '76 TT500 in the March issue of Dirt Bike. Maybe some ideas there.

A lot of that stuff is already gone but you gave me a couple of ideas for the little things that add up.  An ounce isn't much but sixteen of them do make a pound.  Will get a new tank, plastic maybe?, then work on the little things during a winter rebuild.  The easiest and cheapest thing to do would be to lose twenty pounds off my belly.  I'll go take a nap and think about it.  

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On 3/22/2017 at 7:51 AM, Jimmy Pascol said:

How much weight can be saved with a disc brake swap to an XT500 w drums?  My front/rear weights are a staggering 138/198.  I'm so depressed.  

Are you referring to the weight distribution 138/198?

Seems like a disc brake conversion might be pricy, no?

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On 3/23/2017 at 5:57 PM, 76xtdrvr said:

If not already addressed, there's lots of over-engineered heavy steel parts on the back end of those XT's to modify; fender, axle, axle nut, wheel spacers, chain adjusters, footpeg bosses on swingarm, turn signal brackets, brake actuating arm, etc. There's a write-up of a modified '76 TT500 in the March issue of Dirt Bike. Maybe some ideas there.

A lot of that stuff is already gone but you gave me a couple of ideas for the little things that add up.  An ounce isn't much but sixteen of them do make a pound.  Will get a new tank, plastic maybe?, then work on the little things during a winter rebuild.  The easiest and cheapest thing to do would be to lose twenty pounds off my belly.  I'll go take a nap and think about it.  

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Plan is to use YZ and CR450 parts at hand.  Don't know of a real highest-and-best-use type swap to do what I'm aiming for.  Read of some using KTM stuff for the brakes too.  Wish I had a milion dollar shop and ten engineers to try out all my swap idea once and for all to find the best ones.   I'd settle for beer money and a monkey to hand me wrenches right now.  Challenges beget character and everybody says I'm quite a character.

Edited by Jimmy Pascol

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Aiming for 45/55 front to weight ratio means I'm within striking distance with a few parts swaps.  Looks like YZ hubs and rear brake are on tap for me.   Five pounds off the rear of the bike and ten off my belly should do the trick.  Will advise.

Stock rear XT hub weighs 6.5 lbs.  Inquiring minds will want to know.

Edited by Jimmy Pascol

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On 3/23/2017 at 5:57 PM, 76xtdrvr said:

If not already addressed, there's lots of over-engineered heavy steel parts on the back end of those XT's to modify; fender, axle, axle nut, wheel spacers, chain adjusters, footpeg bosses on swingarm, turn signal brackets, brake actuating arm, etc. There's a write-up of a modified '76 TT500 in the March issue of Dirt Bike. Maybe some ideas there.

Mine's already stripped down to flat track trim.  Replaced some number plate and seat mount hardware with velcro and saved two pounds.  Got a big ol' heavy gas tank on it but a smaller one is on the way to save another pound or two.  It's better to reduce the unsprung weight of wheels, brakes, swingarm, etc.   Handling wise, losing one pound of unsprung weight is like losing 6-7 pounds off the whole bike according to sources.  

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Weight of bulbous XT gas tank is 7 pounds empty.   It's going on Ebay.    

Edited by Jimmy Pascol

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20 hours ago, Jimmy Pascol said:

Weight of bulbous XT gas tank is 7 pounds empty.   It's going on Ebay.    

what color ?

 

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