p@ul250

Hi Stu,

 Just seen your post in which you say you think your chair is a Beamish. If so your chair was designed to use an 18" wheel and yes you will have a lot less ground clearance than you will have with a more modern sidecar design. This is Chris Newsham  with a Beamish chair fitted to a modern Gas Gas. He ran it for one year before coming to me for a newer chair (second photo)

Hi Stu, sorry for the delay in replying (I don't come on this forum very often).  CDS tube is fine as long as it's not HP hydraulic tube. I use BS 4 T45 tube which is MSA approved for role cages)tube (25mm x 1.5mm) for the main frame tubes on the chairs I build and ERW tube (20mm x 1.5mm) for the nose and rear deck. 

All modern trials sidecars use a 17" wheel, ether one from a Honda cub C90 with a hub brake or a more modern 17" alloy rim laced to a Hope mountain bike hub with a disc brake set up. The disadvantage of an 18" wheel is it's extra weight  

What bike are you fitting the chair to?  have you tried razing the nose of the chair up?  you will will find that this will push the wheel down and should increase the ground clearance.  Call me on 07491642421 or email me at pdjtcollins@yahoo.co.uk

yellow outfit has Cub wheel and the green one a Hope MTB hub with disc

 If you really get stuck I do do a sidecar fitting service 

Regards Paul C

Hi Stuart, Yes over the wheel base of the bike. What I used to do before I got my jig set up was to draw a straight line on the workshop floor longer than the bike and stand the bike on it with the steering straight and the bike upright ( a small digital & magnetic level on the rear disc works well). Use a large square to drop a line down from the center of the rear axle and then measure 9.5" forward from it and mark a line at 90 degrees out from the first line (this marks the centre line for the sidecar wheel spindle. Measure out 34.5" along this second line from the first line and this marks the minimum track center of sidecar wheel ( You can make it wider that 34.5" if you like, but not thinner and comply with the ACU's rules). With the sidecar set up on these marks use a long straight edge set against the sidecar wheel as near to spindle height as you can and measure from the center of the front and rear wheel out to the straight edge. Front measurement should be 1.5" less than rear.

 I hope this helps and I'm not teaching granny to suck eggs. Out of the nine outfits in the attached photo I built six of them.

Regards   

Paul.