OzVMX Forum

Clubroom => Tech Talk => Topic started by: Ray Kricker on May 11, 2010, 05:55:30 pm

Title: Model 120 Bultaco wheel offset
Post by: Ray Kricker on May 11, 2010, 05:55:30 pm

I re-laced the front and back wheel of the Mk7 250 Pursang I am restoring.  My question is, with the wheels mounted in the bike should they both be central in the forks and swingarm?

Title: Re: Model 120 Bultaco wheel offset
Post by: Moto on May 11, 2010, 08:07:23 pm

  Yes.

Title: Re: Model 120 Bultaco wheel offset
Post by: Ji Gantor on May 11, 2010, 11:23:34 pm

Hi Rayk,
As Moto said Yes.
The problem is the rear wheel is hard some times to determine where the centre is due to chain offset.
The front is easy as it should line up in the middle between the forks.
Even when you get your wheels back from the wheel builders they some times do not line up.
Just measure from a known position on the forks and true the rim on the bike. This is the best way to do it and after every ride you may have to true it again as spokes loosen or stretch.

Ji

Title: Re: Model 120 Bultaco wheel offset
Post by: Ray Kricker on May 12, 2010, 07:27:13 am

Thanks guys.  Luckily I haven't 'trued' the rear wheel yet - just laced it.  The front - well looks like I am about 3-4mm out.

Title: Re: Model 120 Bultaco wheel offset
Post by: Ji Gantor on May 12, 2010, 07:29:50 am

Most bikes are out 3mm.
It is easy to true with only that much unalignment.

Ji

Title: Re: Model 120 Bultaco wheel offset
Post by: vmx42 on May 12, 2010, 08:49:51 am

And don't forget that not all bikes have symmetrical swingarms. So be careful where you take your measurements from. The centre of the swingarm and the centre of the axle mounts are not always in a line

I would check with other Bultaco owners.
Thanks
VMX42

Title: Re: Model 120 Bultaco wheel offset
Post by: jerry on May 12, 2010, 08:53:27 am

Ring Peter Schoene Bultaco Parts 03 51489191 or 0427507861 Cheers Jerry

Title: Re: Model 120 Bultaco wheel offset
Post by: Ray Kricker on May 12, 2010, 12:00:51 pm

Ok, I rang Peter, he said that the front always had a slight offset to the left (when sitting on bike) but not sure why.  He suggested centering the front in the forks and then string lining to the back.  Cheers.

Title: Re: Model 120 Bultaco wheel offset
Post by: Ray Kricker on June 20, 2010, 06:45:12 pm

Asked Donny Newell also he said the same as Peter, so reset the front in middle of the forks.  Strange thing though, when lacing up the back it would have ended up the same as the front with 5mm offset to the left.  So did it as did the front and centered it in the swing arm.