April 10, 201313 yr MMMmmmm, I have 2 bikes, 1 with 1.85 rim the other with 2.15 rim...can't tell the difference, the profile looks identical and the tyres both measure exactly 4 inches.
April 10, 201313 yr Maybe the difference come from the tire themself . On the 1.85 rim I mounted a 400/18 TT IRC and on the 2.15 a 400/18 TT Michelin. I will take the old measuring tape and confirm . Guy
April 12, 201313 yr I went in the shed with the caliper and the measuring tape this morning. The IRC mounted on the 1.85 rim is a little more than 1/4 inch narrower than the Michelin mounted on the 2.15, both tire at about 4.5 p.s.i. Guy
April 12, 201313 yr Hi Guys, Has I have said, a 4 inch tyre is 4 inches wide, a 350 tyre is 3 1/2 inches wide. So if you run a modern 4 inch tyre in a standard wide sports Cub swinging arm you are going to get clearance issues .you can lengthen the arm by 1 inch. I do it by extending the spindle plates, Rather than cutting and extending the tubes, this helps with clearance at the front of the arm. And makes for a better wheelbase. But has I have said using a Triumph Cub frame is has it always has been a compromise , has the bike was not designed has a trials bike. If you want to get over this problem you have to spend a little more money and buy either a Faber Otter frame or one from Armac. There are a few more who make fames for a Cub engine but I have not had dealings with these. One is in the IOM and one in Devon has I know of. I have built the Top Cat Cub frame using the dimensions from Pat Slinns BSA trials bike and using the same WD BSA B 40 swinging arm., has he did. And I still recon this is one of the best little bikes that I have built. Take a look at www.bsaotter.com for the full build. Regards Charlie.
April 15, 201313 yr Author Well i havent been on here in a while and it appears ive opened up a hornets nest. i did as duncan suggested and offset the rim from the centre line of the bike,i bought an armac swingarm (great piece of kit) cheers Duncan again. i used a 5mm ring to push the rear cog over for more room and offsett the engine as well,not by a lot maybe 2mm, i have now got great clearance and the bike rides and handle with no problems as feeling any different to standard set up regards C/G problems, hope this clears some things up and opens up new areas of discourse. as it alll makes my bike get marginally better ty all for the answers and replies ill have to visit more often regards dan
April 15, 201313 yr Author Im just in the process of making a narrower lighter rear subframe lets see how that goes,oh and widening the rear hub to do away with the spacer ring used at the moment,i do so like this hobby,ill get to ride it more soon,lol Dan
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