Reggie3cl said:
I think it needs better forks. Wonder if BMW K series ones fit?
Yes, Reggie. That's what I have on my RGS. 41 mm Showa forks from a K-series BMW.
Simplest option with the BMW front end is to use the BMW triple clamps and wheel because it's basically a bolt-on kit. You'll need to change the steering head bearings to the stock BMW items because it has a larger diameter central pivot tube. Bearings have the same OD so they'll fit into the RGS steering head. BMW steering head is a couple of mm longer than the RGS, so you'll need spacers under the bearings to get everything to fit nicely.
If using the Laverda triple clamps, they'll need to be bored for the larger BMW forks (not sure whether they have enough metal to still be structurally sound when bored though). The Laverda clamps space the forks a bit further apart than the BMW so if going this route you'll need to make a custom length axle for the Beeer forks.
As for steering geometry, if using K-series forks with bored Marzo triple clamps, you'll get about 5mm more trail because the BMW forks have the axle offset to the rear by that amount (for no reason I can fathom). A complete K-series front end transplant will result in about 5mm less trail than the standard Marzochhi front end because the Beemer clamps have about 10 mm more offset than the Marzo items. If you want the exact same trail as the original RGS, you'll need custom triple clamps.
The Beemer forks are longer than the Marzo, so will need to be slid up through the clamps a bit to preserve the RGS ride height.
I obviously like to do things the hard way because I opted to use the original RGS wheel with the BMW front end. Mainly because that's what I had. I thought it would look better anyway because it matches the rear wheel. That meant fitting different wheel bearings for the larger BMW axle, making a bunch of bearing and axle spacers, and making disk carriers with the correct offset for the Beemer caliper spacing. Note that the BMW uses 285mm diameter disks, which is an unusual size. If you want to use the RGS front wheel with original disks, you'll need to reduce the disk offset somehow (machine a bit off the carriers or the wheel), and make up some caliper adaptors to suit the disk diameter. That's in addition to changing the wheel bearing and spacers as mentioned above.
For a road bike, you'll need to work out how to drive the speedo. I dunno what arrangement the BMW wheel has because I don't have one. I fitted a cheapo magnetically oprated bicycle speedo. I don't really care if it works or not. It's just there to keep the roadworthy bloke happy.
Anyway, whatever you choose, it's all do-able. Some options more easily do-able than others.
Only problem at present is that I can't report on how well the K-series forks work with the RGS frame because the bike isn't quite finished. Hopefully in a few weeks ...
Cam
No replacement for both currently on hand, so have to wait until I get a parcel with the parts. Oh - and battery was drained (no wonder after almost a year with no running...).
