Stelvio / SBW chair

[Hairyjohn]

Just the beginning
Just started to prepare My 2010 Stelvio for its up and coming SBW chair. First off is the wheels, I have am going for a car wheel conversion, so first off choose the wheels, After a lot of thought I have gone for 16" x 6.J alloys with 32mm offset and 5 x 100mm stud pattern, I want to use them on both the bike and the chair so need to build adapters for the 4x80m Guzzi wheel and the 5 x 120mm BMW hub used on the chair, Starting with the bike it looks like a two part affair, I have drawn it up and made a wood mock up and it looks like I will need to run about 1/4" out of centre to clear the top bolt that clamps bevel box to the swing arm. Bit of a shame but the pay off is a good choice of tyres which will allow me to run close to standard gearing or drop almost 10% just with rubber.
Anybody done this ?
Next I hope to build a set of forks that will use another same size wheel so that carrying a spare is possible
Pictures to come if I can work out how to post them
HJ

[FR700]

Originally Posted by Hairyjohn

Just the beginning
After a lot of thought I have gone for 16" x 6.J alloys ... Starting with the bike it looks like a two part affair, I have drawn it up and made a wood mock up and it looks like I will need to run about 1/4" out of centre ... Bit of a shame but the pay off is a good choice of tyres which will allow me to run close to standard gearing or drop almost 10% just with rubber.

HJ

You'll never notice the offset. Granted your diff bearings will see a higher side load but handling will not suffer.

16 X 6 rim and tyre ... have you taken into consideration how much the two will weigh compared to the stock setup ? Weight ( inertia ) will kill acceleration more than you think




What do you mean by " two part adapter " ?



.

[Hairyjohn]

The alloy weighs in at 8.5KG which is the lightest one I could get. I have not weighed the Guzzi wheel yet, With a Tyre I am up about 4KG on the BM wheel plus the adapter which is not yet made.
The adapter in two parts basically will have a billet about 60mm thick which holds the discs / ABS ring in place and is bolted on with the stock wheel bolts, then a further billet which holds the 5 wheel bolts is bolted to the first with 9 M8 bolts
This way all the bolts will have enough meat around them to be strong, I will use helicons to add strength.
HJ

[FR700]

I can visualize that. Thanks for the clarification.

Looking forward to seeing progress pictures to see your ideas come to life.


For reference purposes , I made two adapters for my K series bm'. The first one steel as I had nothing to compare it to from first hand experience. The second one from alloy. The weight/inertia difference is noticeable. Not a deal killer , but there none the less which could be addressed by using a lighter rim.

These were used in conjunction with the same 15x4 steel rim.

.

[jaydmc]

We have a Stelvio due in the shop in 4 weeks, we will be developing both left and right side mounts as well as a car rear wheel for this bike.
Jay G
DMC sidecars
www.dmcsidecars.com
jay@dmcsidecars.com
866-638-1793

[Hairyjohn]

Originally Posted by FR700

I can visualize that. Thanks for the clarification.

Looking forward to seeing progress pictures to see your ideas come to life.


For reference purposes , I made two adapters for my K series bm'. The first one steel as I had nothing to compare it to from first hand experience. The second one from alloy. The weight/inertia difference is noticeable. Not a deal killer , but there none the less which could be addressed by using a lighter rim.

These were used in conjunction with the same 15x4 steel rim.

.

I certainly agree that unsprung weight needs to be kept to a minimum, But as with everything sidecar compromises have to be made. Not being an engineer I worry more about strength, Ie losing a bit of performance against sudden failed is no contest.
Have you ever checked a wire wheel against a stock bike alloy ? I suspect the alloy will weigh more.
HJ