Sportster/Cabrio Chassis Similarities

[Mike]

Whilst discussing Marlins with a very knowledgable member he advised me the Sportster and Cabrio share the same basic chassis - obviously the anchorage points have changed for the BMW, but the base chassis is still the same.

I find this an interesting proposition, and would like to check a few key dimensions, as I had always assumed the Sportster had more room in both the engine bay and cabin?

Obviously all the GRP panels, doors and bonnet can be different, possibly giving more engine space at the front, and certainly more arm room over the top of the doors.

But is the cabin the same internal width?
And the boot? - is it the same as the old Cabrio without a lid?

What is the clear space between chassis rails:
just before they arch over the rear wheel?
over the rear wheel?
where the fuel tank fits?
at the front where it joins the cross member?

What is the wheel base of the LWB Sportster?
Again, I've been informed the Sportster had its wheelbase extended when the Cabrio was increased in length, because it shares the same chassis, so presumably some of the early Sportsters are SWB?

[Chris Cussen]

I know Marlin did a special build, which was a Sportster front end and Cabrio back end.

[GreatOldOne]

I'll take some accutrate measurements for you later today, after the welder's been. All my bodywork is off, so it should be easy to do.

[peterux]

There certainly was a SWB Sportster. The first hood Marlin supplied me was for a SWB. The cabin is about 2" shorter.
I suspect the Sportster chassis is built on the same jig as the Cabrio as it looks very similar, but is probably an evolution to suit the Sportster body panels. The 'superstructure' is different and the suspension mounting points were changed to suit the BMW running gear. Indeed, the e36 chassis is different at the back to the e30 chassis and the latest e36 chassis's are different at the front to the early ones built in 2004.

I assume you've seen my chassis pictures?


Chassis by marlinpeter, on Flickr

[Mike]

Originally Posted by Chris Cussen

I know Marlin did a special build, which was a Sportster front end and Cabrio back end.

It was really only a Cabrio, with Sportster front suspension. Gerry Haines on the South coast ordered it specially.
I really like it, but I know some of the (purist) Sportster owners are not so keen!! - (no names Peter from Uxbridge!)

[GreatOldOne]

I'll get those measurements tomorrow Mike - I want the paint to dry on the chassis before I start mucking around with a tape measure.

[GreatOldOne]

I will get those measurements for you Mike, but not today. I've only just got back from MK where Pauline has spent all day shopping for swimwear for a holiday in June...

I'm feeling both drained in mind, body & wallet, but I have been told that as I've been such a good boy I can play in the garage all day tommorow.

[GreatOldOne]

Right, here you are:

Cockpit width - min 1020mm, max 1200mm
Boot width - 1160mm
Rear chassis width (between rails) - 880mm at all the points you mentioned
Front cross member 740mm
Wheel base (centre hub to centre hub) - 2620mm

[Mike]

Originally Posted by GreatOldOne

Right, here you are:

Cockpit width - min 1020mm, max 1200mm : Cabrio 1020 - 1120mm
Boot width - 1160mm : Cabrio 1160mm
Rear chassis width (between rails) - 880mm at all the points you mentioned : Cabrio 880mm
Front cross member 740mm : 750mm
Wheel base (centre hub to centre hub) - 2620mm : Cabrio 2700mm

Are your cockpit dims between internal rails? - is the rear one correct?

[GreatOldOne]

Pretty sure it's right... But can double check tommorow. I measured the cockpit at the front of the rear of the scuttle, it narrows more toward the engine bay.

The max cockpit figure is just behind the seats, and is across the metal flanges that stick upright. These are in effect extensions of the outside of the chassis rail. The front cross member figure is also to the outer edges of the rails.