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Rim choice


slowrider
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Restoring a 199B bultaco for twin shock competition and curious if converting to the type of rim that uses the external type spoke as opposed to the through the rim type spoke would be an advantage? 

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Does not look right in my opinion.

The original Acront rims with red label are super light. 

The original rear rim is a bit narrow, (1.85) it would be of much more useful traction effect to use a slightly broader rim (2.15) from Acront which is now named Morad.

You can mount tubless IRC or tube type IRC on classic trials rims, these will stay on the bed and are as good as Michelin.

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The practical advantage of the flanged tubeless rim is that eliminates the possibility of losing air through the spokes which can happen on normal tubeless rims if the seal isn't good (I use silicon sealer instead of a rubber band, the type used on aluminium window frames)  However, with some tyres either type can leak from the tyre bead so flangeless doesn't 100% guarantee that a tyre won't deflate slowly over days/weeks

Others like them because of appearance which is just personal choice

The problem lacing to a Bultaco hub is the length of the spokes on the sprocket side can be a problem. I've seen Fantics with them so it can be done. I think though that they are hard to find now.

If you buy a used rim make sure you see it first as they can corrode on the inside so if there is a tyre fitted you won't see it, as outwardly they look fine

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many thanks for the info, still on the fence about how to go, depending on how bad the old rims are, looking to build a really nice looking bike, but also want to compete in twin shock trials so it needs to be able to mount the best rubber.

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12 hours ago, b40rt said:

Depends to the "size" and the type of the rim, back in the early to mid 80's there where most trials bike fitted
with rims from Acront and of these where of type TR.

This type was the lightest rims available for the trials tire and legal for use in traffic,
back then labeled with a red sticker by Acront.

TR model rims are not manufactured anymore, instead TXR  and TC type,
(back the labeled with a yellow sticker by Acront).

The measurement are made inside the rim the outside might differ and is not regulated.

Here a comparison from LoLo in Austria about the TC (WM) type rims with each cut and where to measure them.

Between the 1.85 and the 2.15 is a difference of 15%, what this difference does is that the broader gap result in
steeper tire walls and thus gives a better bigger and better foot print.

 

Felgen.jpg

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Lots to digest from you guys! many thanks! Think I may start out with trying the tub route in the old rim for now, but would like to have what looks best and works best for competition after I get some miles on it. 

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  • 2 weeks later...

Well I think I screwed up, the rims were beyond what I wanted to use so I broke down the rims to just the hubs so I could get them powder coated and realized I have no way of knowing the off set for when I have the rims put on, is there a spec I can use when rebuilding the wheels? I know the clearance is tight and it needs to be right.

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I can look at the bike but my measurements will not be exact as the wheels are now mounted.

The notice sheet I made wlth all the drawings how to put on the spokes got lost during the rebuild a couple of years ago.

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  • 2 weeks later...

Bad new, good news, bad news! My wheel builder here in the states says he cannot get rims right now due to the supply chain issue and is 3 months back ordered! On a good note, he said they can polish out my rims with minimal damage showing the bad news is $800 dollars for new spokes polish and build! ouch! Hands are tied, so I am shelling out the bucks for now.

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4 hours ago, slowrider said:

Bad new, good news, bad news! My wheel builder here in the states says he cannot get rims right now due to the supply chain issue and is 3 months back ordered! On a good note, he said they can polish out my rims with minimal damage showing the bad news is $800 dollars for new spokes polish and build! ouch! Hands are tied, so I am shelling out the bucks for now.

$20 + per spoke ?

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5 hours ago, slowrider said:

Bad new, good news, bad news! My wheel builder here in the states says he cannot get rims right now due to the supply chain issue and is 3 months back ordered! On a good note, he said they can polish out my rims with minimal damage showing the bad news is $800 dollars for new spokes polish and build! ouch! Hands are tied, so I am shelling out the bucks for now.

 

47 minutes ago, b40rt said:

$20 + per spoke ?

I read it as the $800 includes the spokes, rim refurb labour and wheel build labour. That sounds like normal commercial rates to me and a good reason to do it yourself

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23 minutes ago, feetupfun said:

 

I read it as the $800 includes the spokes, rim refurb labour and wheel build labour. That sounds like normal commercial rates to me and a good reason to do it yourself

If I had the skills and tools...

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