gthyni Posted July 25, 2003 Posted July 25, 2003 Updated with some ideas in the replies Read this excellent article Interesting facts about shortering the wheel base, but what really interested me was the answers about weight. Cippi says that the MG engine is 25kg heavier than a air-cooled Ducati twin + 10 kg for the drive shaft. No lower than 160kg is possible. Certainty the difference is considerable. I suffice to think you but between an engine entire Guzzi of change and an engine Ducati two valves there are 25 kg of difference to which go added other 8-10 kg of transmission cardanica. Today a Guzzi gotten ready for the contests can arrive at the utmost to 160kg but is necessary worker on every detail and to lighten everything that is possible to lighten. The weight is almost always in the shadow of engine tuning when performance of street bikes is discussed, but is just as - if not more - important than raw HPs. The cheapest way to loose some weight is probably to loose the extra 10 kg around our waists , but besides that I listed some points where kgs can be lost: First we want to loose some unsprung weight Lighter alu rims, magnesium rims, carbon rims - lots of kilos to loose. The selection is limited by the MG specific rear drive, but who says front and rear must be identical. break rotors - thinner, lightened, carbon racing calipers - lighter fork - surely there must be lighter (and better) forks than the Marchozzi out there. How about the Öhlins unit? Swing arm - heavy steel construction - alu profiles? Tyres - there are some diffences between tyres of different brands and profiles Shaft to chain conversion - but is it a Guzzi after that?? And more general weight loss: Exhaust system - OEM is very heavy, both the x-over and the muffler Replace rear subframe with something lighter - carbon or alu structure Air filter box and side panels - loose them and install pods Inner rear fender - loose it Carbon replacement - seat bank, tank, fairing (if not naked), front fender Lighter battery (and alternator) Smaller light head beam and other lamps And then for a race bike: Loose the starter motor Loose the battery and alternator (only a small ones to drive ECU, ignition, fuel pump and injectors] Loose all lights and signal horns Losts of titanium - fork clamps, exhaust pipes, bolts and so on and on And what about the engine/gearbox? What can be done? And what have I missed? Comments? Let's have a discussion and make this a How-to.
jrt Posted July 25, 2003 Posted July 25, 2003 I like 'unfeathered' I've always heard it refered to as 'unsprung' weight. Lose the carbon canisters and half a kilometer of tubing under the tailpiece- that's good for 2-3 kg, I think (6ish pounds). And they make a nice wall hanging. I know the flywheel is considerably lightened compared to earlier bikes, but the crank isn't as far as I know. What are the considerations in lightening a crankshaft? Other than robustness, of course. One could go with Carillo rods, lighter pistons. But ultimately you're right gthyni, it's the waist for many of us. J
dlaing Posted July 25, 2003 Posted July 25, 2003 How about a Ghezzi and Brian frame? Handlebar weights. The glass and steel headlight could be replaced by a short lived plastic headlight, possibly an enduro headlight, assuming you want to be slightly road legal. Fenders, do you really need them? You could take of the rear cowling. The seat, take off passenger section, and cover with wet suit material rather than vinyl. Passenger pegs. Tool kit, who needs a tool kit on our so reliable bikes? How small of a battery could we get away with? I'll bet our starter is a lot heavier than a Ducati's, but that might be an expensive conversion with the conversion box adding weight. Remove oil cooler. This will shorten engine life, but you could probably make up for it with more frequent oil changes. Alternator. there has to be a lighter one out there. Rear transmission or whatever it is called, might be replaced by one from a small block guzzi???? Expensive and short lived modification Or get a much lighter Breva and see how big you fast you can make it
callison Posted July 25, 2003 Posted July 25, 2003 Are you planning to race or ride this on the street?
zebulon Posted July 25, 2003 Posted July 25, 2003 As i told my special SuperTwin is 199 kg with 4 L oil , full tank (only 15 L). This is a special Ghezzi&Brian modified frame for 4v engine with a 1400 mm wheel base. This frame is the number 2 / 2 produces , the other is the Pro Thunder. With alumimium forged wheel, all the elelctrical for road (light , turn signal etc etc ) Lot of alumium & special parts saving weight and a small exhaust under gear box with save also a lot of weight etc so it depends of what you wanted to do with your bike. For a road use , i think that it will be really hard to go under a real 190 kg with a big block engine For racing this is another question, my guzzi mechanic (with is a friend) got is race guzzi bike with had quite some years as engine basis is a 850 T3 where it put ducati ignition. This bike which have been done between 90-91 only weight 165 kg for a 1060 cm3 engine. This bike as run in the Daytona in 92 (if my memory is good) riding till 258 km/h .
Paul Minnaert Posted July 25, 2003 Posted July 25, 2003 weight can be saved on a lot of places, some more expensive than others. You can end up having spend 2 times the new price, on extra's, if you go all the way. My friend has replaced all bolts with titanium, something like 5 $ for a small bolt, are you counting? The battery can go to 9AH, if you buy the right one. The oil sump with cooler can go if you buy a V shape sump, that's lighter. I had a alu swingarm here from a german special builder, It looked lighter, even feels lighter, ony it was the same weight:-) The tailframe is heavy, when you don't need to be with 2 persons with lugage on it you can loose a lot here with an alu subframe. The moere you do, the more expensive it gets. Wheels are an interesting thing, only one brand makes them with a shockabsorber in the rearwheel: PVM, count 2200 euro for a set. I just got a front wheel from ebay, see the picture, this is only 3.7 kg. Now looking for a rearwheel:-)
gthyni Posted July 25, 2003 Author Posted July 25, 2003 Paul, thanks for the tip about PVM Yes one could easily go to extremes to loose the last kilo, the battery was on my mind but I forgot to list it, the rear frame (is this what is also called subframe?) idea I'll note. Zebulon, your bike looks extremely nice. It is good to have people like you and Paul onboard who go for "the full monty". I think the article ppints out how to get handling like a G&B frame from a stock frame. Of course it involves cutting and welding your frame wish is not for the faint of heart. Also I think G&B frame doesn't fit the 6-speed gearbox everybody(?) says is much better then the old 5-speed. I am talking about a street bike and think going down to 190kg dry weight is a realistic goal conbined with 100-110 HPs (on the crankshaft) it should be easily handled and give a good push in the back. And yeah I lost the tool kit already About the under-gearbox-exhaust: I am not sure it really is lighter than 2-to-1 system with a light megaphone or slipon, it at least does not look as good as one IMHO. I'll updated my first post to include your tips, keep'em coming.
Mike Stewart Posted July 25, 2003 Posted July 25, 2003 I weighed my Dymags last year when I installed them on my V11 Sport and the weight savings were about 13 lbs. Most of the weight was saved on the rear wheel around the cush drive. Now that is 13 lbs. I don't have to loose around my waist! Mike
Murray Posted July 26, 2003 Posted July 26, 2003 I think it still would be more effective if I lost at least 10kg and learnt how to ride properly before I seriously start worring about the bike. Athough if you make the bike too light 1. you have to review your suspension settings. 2. on rough roads (which are just about the only type around here) bike is less settled and stable. Much to the displeasure of a couple of current 954, SP1 and GSXR owners who find on sweepers a 7 year old Guzzi keeping pace
gthyni Posted July 26, 2003 Author Posted July 26, 2003 Athough if you make the bike too light 1. you have to review your suspension settings. 2. on rough roads (which are just about the only type around here) bike is less settled and stable. Much to the displeasure of a couple of current 954, SP1 and GSXR owners who find on sweepers a 7 year old Guzzi keeping pace You are right and you are wrong, a heavier bike can be less sensitive to suspension settings but a lighter bike with correct setup is always better. I also run a lot on bumpy roads and my compression damping is set very low. Sure the fork dives quiet a bit more on heavy braking than with factory settings but it is still a long way from the bottom and bumps and roughnesses is "eaten" by the suspension as it should be. Too stiff settings and you loose contact with the ground, probably what's wrong with your friends sportbikes. When going longer trips on high speed roads I dial up the compression settings a few notches. Especially the unsprung weight is important to minimize since that is mass "outside the suspension". You have to use stiffer settings to control this mass and then you loose some ground contact.
Mike Stewart Posted July 26, 2003 Posted July 26, 2003 After installing lighter wheels on my 00 V11 Sport, the bike felt different in a negative way. On high speed sweepers 80 mph. plus the bike felt very nervous and unstable. I thought it was the tire size and I went down to a 170/60 rear tire on the 5.5 inch. rim. Slightly better but not as stable with the stock wheels. I believe the problem is due to the less gyro effect of the lighter wheels. I have talked to Lance at Hare racing and he had the same problem on a RC51 when they installed carbon wheels. The bike just was unstable. The solution for the RC51 was to readjust the suspension settings and head angle. This is the main reason for going with a Penske rear shock so I can play with shock length which will effect the head angle. Mike
Baldini Posted July 27, 2003 Posted July 27, 2003 Eh? I miss them big wheels too. Get the suspension sorted. Get rid of the FI glitches & ride it. 190Kg - 220Kg??? On the road? It don't matter. Spend the money on an RS250 /Jap 400... Mike, I thought to maybe go to a smaller tyre on the std 5.5" rim. The std 180 /55seems to me to roll side to side v slow, seems overtired. Do you recommend 170/60 w/std front 120/70? KB, Wales
callison Posted July 27, 2003 Posted July 27, 2003 I like the 170/60 w/std front 120/70 combo. Dave Richardson of Moto International recommends a 160/60 - 110/70 combo for even lighter handling. That is, if my memory recollects correctly.
gthyni Posted July 27, 2003 Author Posted July 27, 2003 that is on the 5.5" rim??? I should not go lower than 170 on a 5.5" rim on a 4.5" rim you could go down to 150 recommended ranges 5.5" 170-190 4.5" 150-170 3.5" 110-130 Personally I think fat tires on street bikes are only for posing proposes and would go for the lower end and recommended ranges.
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