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Final gear ratio, Top Speed
Zoophoria - 16/6/04 at 08:36 PM

Wich final gear ratio would be good for a bec with a blade, r1 or a zx9 engine? I'm planning on using a differential from a donor veichle. I'm also wondering how fast becīs go, I dont mean those who got turbos and nitrous etc, etc,.. but the "normal" bec.


Hellfire - 16/6/04 at 08:40 PM

Ours is good for 115'ish mph with a Sierra 3.62 LSD from a 4x4. Engine is a 1995 (pre-cat) 893 Fireblade. I've heard a 3.38 gives more legs...

[Edited on 16-6-04 by Hellfire]


Zoophoria - 16/6/04 at 09:04 PM

Hellfire: Where can I find seats like that?
They look light!


alister667 - 16/6/04 at 09:50 PM

Pop along to THIS thread and download 'Speedcalc.xls'. Its in the 5th post down.
It's a spreadsheet that shows you the top speed in various gears of many different bike engines, allowing you to play with different diff, and (importantly) wheel and tyre sizes.
It's well worth playing with as cruising at 60mph can be a little harsh if you don't get your calcs right!
All the best
Ali


spunky - 16/6/04 at 09:53 PM

Gave mine a 'nudge' after failing SVA again yesterday. Moved up to top about 95, but bottled out around 115, still had a few revs left. 3.62 open diff, 14" wheels on 185/60 yokos.

John


JoelP - 16/6/04 at 10:20 PM

remember you can take the LSD bit from a nonslip diff and add it to any diff if needed. at least, someone said they had done it...

also, diesel or auto sierras have the lowest (highest?) ratios, 3.38 and 3.1something.

all IIRC of course...


Zoophoria - 17/6/04 at 06:12 AM

quote:
Originally posted by JoelP
all IIRC of course...


What is "IIRC"?


timcrasher - 17/6/04 at 06:53 AM

My MK ZX9R does 105.2 mph flat out on the rev limiter in top. Spot on for trackdays but crap on the road. Very impressive top gear roll on acceleration figures though.
I had a problem with my original diff when it was damaged during the reverse box locking up. My neighbour got me out of the sh#t with the one from his old 1.8 cvh Sierra. It turns out it's a 3.92 and when matched to the low gearing of the ZX9R, it makes it flippin' stupid on acceleration.
I need to find a 3.38 or lower pronto


gys - 17/6/04 at 07:38 AM

quote:
Originally posted by Zoophoria
What is "IIRC"?


If I Recall Correctly


Zoophoria - 17/6/04 at 08:09 AM

I can't really decide wich way I should go, either I use a sierra diff and mount it with some sort of a flex coupling directly to the sprocket of the engine wich I think would be the easiest way or I go for a chaindrive wich will be easy to change the final gear ratio on but harder to build and more expensive I think, with the lsd in mind.


PeterGT4 - 18/6/04 at 04:24 AM

quote:
Originally posted by alister667
Pop along to THIS thread and download 'Speedcalc.xls'....


I did, but it doesn't seem to do anything, even when I change the variables at the top of the page. I have XL Viewer, is that the problem?


Crazy Jay - 18/6/04 at 10:37 AM

Apparently my diff is from a mk1 sierra which are quite hard to find now, its a 3.14 and to think i found it layin in the corner of a scrapyard. Just remember the near side hub nut is a left thread! Made tht mistake and fecked up the threads on the shaft, luckily tho i got them recut


alister667 - 18/6/04 at 11:08 AM

quote:
Originally posted by PeterGT4
quote:
Originally posted by alister667
Pop along to THIS thread and download 'Speedcalc.xls'....


I did, but it doesn't seem to do anything, even when I change the variables at the top of the page. I have XL Viewer, is that the problem?


If possible try to open it in Microsoft Excel itself. Works fine for me in Microsoft Excel 2000. I think I had difficulty getting it working in Open Office.


phelpsa - 18/6/04 at 03:15 PM

The selector doesn't work in open office.

Adam


Zoophoria - 19/6/04 at 12:02 PM

A customer at work said he had a BMW differential that I could have if I wanted, its from a 525 I think. I donīt know if it has a lsd. Would that be a good diff to use? If it has a lsd that is.

[Edited on 19/6/04 by Zoophoria]


JoelP - 19/6/04 at 09:42 PM

quote:
Originally posted by Zoophoria
I can't really decide wich way I should go, either I use a sierra diff and mount it with some sort of a flex coupling directly to the sprocket of the engine wich I think would be the easiest way or I go for a chaindrive wich will be easy to change the final gear ratio on but harder to build and more expensive I think, with the lsd in mind.


in my opinion, its worth having a go at chain drive cos then you have some experience that will help with any future mad twin engine projects. This is what i intend to do.