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 8V gearing options.....

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barry.b
StuartEvans
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Pete Roper
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PostSubject: 8V gearing options.....   8V gearing options..... Icon_minitime1Mon May 17, 2021 7:46 pm

Just to follow on from the other thread where I was saying that a 1200 Sport gearbox had fallen into my shopping cart from whence it is going to fall into my GRiSO I thought it might interest people to learn what the ratios in the various boxes are. I haven't done the sums on the Stelvio yet but I'm pretty certain it uses the same ratios as the GRiSO. I'll confirm later.

OK, so there are basically two sets of primary gears. These are the only helically cut gears in the box. The first one is on the clutch shaft. The second one on the primary shaft of the box. (I'll insert pics later if people wish.)

The way you calculate a gear ratio is taking the number of teeth on the driven gear and dividing it by the number of teeth on the driver. Now the GRiSO uses a 26 tooth clutch shaft gear and a 35 tooth primary. This gives you a ratio of 1.35 to 1.

Both Sport and Norge use a 24 tooth clutch and a 35 tooth primary giving a ratio of 1.46 to 1

(Edit.) Actually looking at those figures is weird as it seems to indicate the GRiSO has the higher primaries, which is weird because the Sports are definitely taller geared. I think I'll have to just take the boxes apart and looksee.

Now after that all the boxes use the same ratios for the first four gears. They are.

1st- 17/38 giving a ratio of 2.235 to one.

2nd- 20/34.         1.7 to one.

3rd- 23/31.          1.35 to one

4th- 26/29.           1.115 to one.

So the primaries in the Sport and Norge box make the overall gearing higher than the GRiSO but other than that everything is the same.

From there things change a bit. In 5th and 6th both the Sport and the GRiSO retain the same ratios with tooth counts of.

5th- 31/30             1.03 to one. Essentially a direct drive.

6th- 29/25.            0.86 to one. A substantial overdrive.

Looking at the Norge though fifth is already an overdrive!

5th- 31/29.            0.935 to one.

And sixth is higher again!

6th- 30/24.            0.8 to one!

ALL the CARC bevelboxes use the same ratio so from the point of this investigation can be ignored.

So, what we can see from this is that the GRiSO is the lowest geared of the lot. This means that it will have, at least in theory, the fastest acceleration and lowest top speed. This is irrelevant in the real world of everyday riding though as you're rarely, if ever, going to be hitting the rev limiter in 6th. I have done it once, maybe twice, the Speedo was saying 247kph! Given wheel slip etc. a more realistic figure might be 220 but I can tell you when it goes 'Blurp-Blurp' at that velocity it is a bowel emptying experience as GRiSO will get very squirrelly if it hits bumps at that speed!

Next cab off the rank is the Sport. I've long liked the slightly taller gearing of the sport. It doesn't seem to make the bike appreciably slower in the lower gears due to the 8V's prodigious Torque but it turns sixth into a true overdrive and if you're wanting to get off the line quickly I actually find that I don't seem to run out of revs and find myself grabbing another gear in a frantic hurry like I can do on a GRiSO. Top speed will probably be little different as the power produced and the parasitic factors, (Wind resistance, the fact the rider is a great fat bastard etc.) won't change. It might even be a bit slower! Who cares? If you're caught doing 200kph here you are going to gaol and your bike is being confiscated and anyway, riding GRiSO over 150 kph for any length of time is tiring! That's why I'm swapping to a Sport box on mine.

Finally we come to the Norge. This has the benefit of the taller primaries but also has those two taller top gears. It just so happens there was one of those boxes sitting around for cheap in Holland as well as my Sport box. Well this morning it fell into my cart as well and it's going to get flung behind the engine in a certain black and Orange 1400cc GRiSO that sometimes lurks around these parts.....

For all the noise and bollocks spouted about 'Getting more power' out of the 8V there are plenty of other interesting, enjoyable and really pretty inexpensive ways of customising and improving your ride!

If you want 130hp? Buy a TV4! Betcha we'll only be half a beer behind you at the pub at the end of the ride and we'll be a lot more relaxed as welll Very Happy

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StuartEvans
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sun May 30, 2021 8:25 am

I have a Norge, which replaced a Ducati ST2. I've been disappointed with the short gears (as compared to the ST2), but after reading your post, perhaps I'm imagining things? Apart from your post, I haven't done any reading on the subject, so I have no real reference. I absolutely think the Norge top gear is too short, particularly at my typical highway speed. I contemplated looking into different gearing - that's not going to happen as you've already done the work. Thanks for that. :-)
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Pete Roper
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sun May 30, 2021 3:34 pm

I'm still a bit perplexed by the fact that the Sport and Norge seem to have lower primaries?? One thing I'd always felt when riding them is that Sports seem a lot more relaxed and, without actually doing any serious comparisons, I'd just assumed that they were higher geared. Anyway it matters not. If I'm wrong the world won't end. It's not like it would be the first time I've goofed up? Laughing

The Sport and Norge boxes will be here soon and I'll be able to lay it all to rest one way or the other. Any-which-way I don't think the differences will be earth shattering but it's always interesting confirming stuff by real world experimentation.
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barry.b
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sun May 30, 2021 7:00 pm

Peter: ignore me, I just wanted to add some fuel to the fire.

I picked up a 2006 (2v) Norge a month ago with low kms, expecting- being designed for long haul highways - that it would either (a) have at least one ovwrdrive ratio or (2) have exactly the same gearbox as a Breva 1200 and/or (c) have no difference in gearbox betwewn the Norge 1200 GT (2V) and GTL (8V).

Your results have flumoxxed me.

I've been reading the work of fiction the Norge Use and Maintenance Book, while waiting in line for a COVID jab (as yer do) ... and on page 97 ...

17/38 = 1 : 2.235
20/34 = 1 : 1.700
23/31 = 1 : 1.137
26/29 = 1 : 1.115
31/30 = 1 :  0.967
29/25 = 1 : 0.862

So are you really saying that Guzzi - a modest operation of not world conquering manufacturing units per year - piss around changing the gearbox bwtween 2v and 8v engines ... and then further refuse to reuse and standardise across models?

(I would have thought 4v heads of Breva 1200 = 1200 Sport = Norge GTL, and GRiSO = Stelvio)

Are these machines bloody individually autographed by the assembler like vintage Fender guitars back in the day?

Heaven help the parts warehouse manager ..[You must be registered and logged in to see this image.]

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Pete Roper
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sun May 30, 2021 7:28 pm

There are big differences in the gearbox between the 2VPC models and the 4VPC models. Apart from the input shaft splines being different the 2V models still had the face cam shock absorber on the input shaft. This disappeared on the 4VPC models.

I haven't bothered cross referencing the actual ratios and tooth counts yet for the earlier bikes. Don't be fooled though. Just because the cases look the same doesn't mean the internals are.

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Oz1200Guzzi
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sun May 30, 2021 8:02 pm

About time we had a good technical discussion, that isn't oil or tyres or incredible horsepower...

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beetle
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sun May 30, 2021 9:06 pm


I accept full responsibility.

When Pete said he was getting a Sport box for his GRiSO, I barged in and said I want one too! Then he used his soothing and suggestive voice that a Norge gearbox with this taller ratios could be mine. I swooned.

Then I went I to full nerd mode and screeched at him, red-faced, spittle flying, “you’ll have to change the primaries or this will be a pointless exercise! Wah! Waaah!”


More work for Pete.


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Oz1200Guzzi
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sun May 30, 2021 9:18 pm

we will find out soon...
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sun May 30, 2021 9:38 pm

Changing out the primaries is no big deal. Once the box is split it's just a matter of yanking the shafts out and playing 'Musical Gears'. I've always liked gearboxes, most people don't find them sexy enough I guess. I think 'Torque Multipliers' are fun.

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Grisonut
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sat Jun 05, 2021 3:37 pm

Funny you guys mentioned that, I always felt like the GRiSO needed an extra gear or a taller 6th..
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beetle
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sat Jun 05, 2021 4:44 pm


If my calculations are correct (and they usually are -> insert "smug" emoji), then:

GRiSO stock box = 111.6 km/h @ 4000 RPM in 6th
Norge box with GRiSO primary = 120.3 km/h @ 4000 RPM in 6th


cheers




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Oz1200Guzzi
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sat Jun 05, 2021 8:17 pm

Ooh, speedy!
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beetle
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sat Jun 05, 2021 11:12 pm


I look forward to utilising the throbbing torque of the embiggening to cruise at lower RPM, thus consumptioning less fat per kilometreage.




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Oz1200Guzzi
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sun Jun 06, 2021 1:32 am

Once I thought I was turning my Sport into a GRiSO. However you are trying to turn your GRiSO into a Sport/Norge. Very confusing - is this like the other man's grass is always greener?

I would concur with the 120 km/h/4000 rpm numbers. However at 4500 rpm everything is just that much sweeter. And it gets more betterer after that, however that is a tale for around a campfire, or in a restaurant with steak and beer.

See you Tuesday.
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beetle
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sun Jun 06, 2021 1:45 am


Well..that would be $1.35

What's the issue? Very Happy

scratch



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Bill Dee
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PostSubject: Re: 8V gearing options.....   8V gearing options..... Icon_minitime1Sun Jun 06, 2021 1:16 pm

I sold my 4V Sport and got the 8V GRiSO. Besided the greatly different power between the 2 bikes I noticed the gearing different right away. I think Pete and I had a discussion back then about the gearing differences. For me the Sport gearing is better.

Took GRiSO out for a ride with my buddy George yesterday. George turned 80 and wanted to go for a Birthday ride. We had a good time as the weather was perfect and the hamburgers at A&W were just fine.
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