January 17, 20224 yr 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?
January 18, 20224 yr The advantage you are talking about is going to a tubeless tire. That can be done with several different rims.
January 18, 20224 yr 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.
January 18, 20224 yr 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
January 18, 20224 yr Author 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.
January 19, 20224 yr 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.
January 20, 20224 yr Author 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.
January 29, 20224 yr Author 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.
January 29, 20224 yr 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.
February 9, 20224 yr Author 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.
February 9, 20224 yr 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 ?
February 9, 20224 yr 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
February 9, 20224 yr Author 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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