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  #1  
Old 30-08-10, 18:47
beggers beggers is offline
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Will Ford internals fit a BMC live axle?

May seem a silly question but seen it mentioned on a couple of Mallock and Clubmans ads that people have done it.

My Fireblade engine has internal gearbox reduction of 1.52 and means with 13" wheels i'm only going to see 70mph at 12,000rpm in 6th so was looking at cheap ways to up it and a Capri 3.09 english interals would give me 88mph.

http://www.westgarage.co.uk/calculat...les/BECrwd.xls

Good spreadsheet for calculating your speed in each gear.

Cheers
Pete
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  #2  
Old 30-08-10, 18:52
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The normal mod is just to replace the diff carrier & planets because they are bigger & stronger. Of course this means the CWP & hence ratio is the same as before, which doesn't help your problem. However you can get 3.7 & even 3.55 BMC diffs.
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Old 30-08-10, 18:56
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Quote:
Originally Posted by dennis.doyle View Post
The normal mod is just to replace the diff carrier & planets because they are bigger & stronger. Of course this means the CWP & hence ratio is the same as before, which doesn't help your problem. However you can get 3.7 & even 3.55 BMC diffs.
Any idea what the 3.55 BMC units were fitted to?
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Old 30-08-10, 19:18
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Sorry, no idea, but everyone says they are very rare, perhaps a Special Tuning bit? Moss Europe offer one, but that is exchange, so not much use in this case.
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Old 30-08-10, 19:52
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Pete,
What current diff ratio do you have?
What year fireblade?
I put the 1998 cbr1000rr ratios into my spreadsheet and got reasonable figures using a 3.62: 1 final drive.
115mph in 6th with 13x20" rear tyres and 126mph on 13x22" rear tyres.
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  #6  
Old 30-08-10, 20:09
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Quote:
Originally Posted by minitici View Post
Pete,
What current diff ratio do you have?
What year fireblade?
I put the 1998 cbr1000rr ratios into my spreadsheet and got reasonable figures using a 3.62: 1 final drive.
115mph in 6th with 13x20" rear tyres and 126mph on 13x22" rear tyres.
95 Blade and I believe its a 3.9 going to count it out tomorrow evening.

I believe you need to adjust your spreadsheet so the rolling dia is 13" as width has no impact on speed only corner grip?
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Old 30-08-10, 20:17
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As attached.
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Old 30-08-10, 20:17
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Quote:
Originally Posted by beggers View Post
95 Blade and I believe its a 3.9 going to count it out tomorrow evening.

I believe you need to adjust your spreadsheet so the rolling dia is 13" as width has no impact on speed only corner grip?
13 is the diameter of the wheel without the side wall of the tyre, a 13x20 has a "rolling" diameter of 20, therefore you can adjust your top speed by fitting larger diameter tyres..
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Old 30-08-10, 20:35
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Quote:
Originally Posted by Radical View Post
13 is the diameter of the wheel without the side wall of the tyre, a 13x20 has a "rolling" diameter of 20, therefore you can adjust your top speed by fitting larger diameter tyres..
Ah, of course!!! Little knowledge is a dangerous thing!

It did seem quicker than 70mph on my shakedown day at Bruntingthorpe.
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Old 30-08-10, 20:39
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Quote:
Originally Posted by beggers View Post
Any idea what the 3.55 BMC units were fitted to?
Yes, as it happens, the 3.55 diff was fitted to Morris Minor vans with the Post Office being the biggest users. I had one fitted to my DNC 750.
I did know where there was a spare one lurking, a well known hillclimber had it as a doorstop or similar.
As dennis has remarked they were quite rare.
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