wilkingj
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 posted on 19/10/05 at 05:31 PM |
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Which Diff for BEC? (now for sale)
Hi, I am thinking of doing a BEC next. I know that the High Ratio Sierra Diffs (3.38 & 3.13) are like hens teeth. So whilst I am finishing off the
Viento, I thought it would be worth keeping an eye out for a Sierra Diff of a suitable ratio.
So whats best?
Whats the going rate?
Do they come with LSD?
Do the come with Lobro shafts?.
ie what are the variants to look out for, and roughly what would I expect to pay as a min or max.
Which cars / models are the ones to watch for?
Namely I want to ensure that I know what to buy, and what to expect to pay for it.
Thanks in afdvance
[Edited on 19/10/2005 by wilkingj]
[Edited on 23/10/2005 by wilkingj]
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
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billy
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| posted on 19/10/05 at 06:27 PM |
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Diff
I got hold of a 3.3 sierra diff, then had a LSD from another 3.6 fitted. most of lsd sierra diffs have bolt on drive shafts. keep a look out for a
sierra diesel as there the ones with the 3.3 ratio
luego-lo-cost finished,vauxhall 16v 2.0,twin 45s de-dion rear set up
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JoelP
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| posted on 19/10/05 at 08:20 PM |
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a diesel ended on ebay, in peterbugger, for £42 the other day (i got outbid ) this would've had a 3.38 diff (note, only 2.3d, NOT in the
1.8td). However, after collecting and stripping, you'd be looking at paying £75 upwards. IMHO 75 is a bargain for one of these, and 100
reasonable. Any more is a bit steep.
LSDs are usually the same, 75 to 125. Much cheaper in a scrappy etc, but that involves pissing about. LSDs are in ALL 4x4s, 3.6 in the v6s and 3.92 in
the 4 pots. All bolt on as standard.
3.14s are MUCH harder than even the 3.38s to find. You might pay £250 if you were seriously after one. Target cars are old 2.3 v6 petrol autos. Thats
the only car i have seen them in. Even then its chancy. Some very old 2 litre autos (im mean like '83 old) have 3.38s fitted.
just to add, im fairly sure that all 3.14 and 3.38 diffs are pushfit.
[Edited on 19/10/05 by JoelP]
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OX
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| posted on 19/10/05 at 09:13 PM |
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unless your going for a zx12 or the busa i wouldnt think you'll need anything more than a 3.6* diff
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G.Man
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| posted on 19/10/05 at 09:32 PM |
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My zx12r is having a cossie lsd...
will see what its like as the lsd may cause some "pushing on" understeer...
think its a 3.62:1 so acceleration biased... fine by me as top speed is way beyond what I will need...
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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Hellfire
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| posted on 20/10/05 at 11:15 AM |
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We have a 3.62 LSD in ours and top speed on Dyno was 129.7mph.
Fast enough for me. (for now)
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smart51
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| posted on 20/10/05 at 11:40 AM |
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I have a 3.62 LSD. The top speed, with my R1 engine, is 120 at 11750 RPM in 6th. In 1st it is 50 MPH.
With a 3.38 diff that would be 54 in 1st and 129 in 6th
With a 3.14 diff that would be 58 in 1st and 138 in 6th.
With bigger wheels and a 3.14 diff you could get to 60 in 1st which would give the best 0-60 if you are a boaster. It is perhaps of more use to those
with 1200cc bike engines, those who want to do more touring (lower revs at motorway speeds) or those who want to go over 120MPH on a race track.
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ChrisGamlin
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| posted on 20/10/05 at 12:32 PM |
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OX, it depends on the engine's gearing and how high it can rev as much as the power, not all bikes are geared the same.
For example a CBR1000 needs the highest diff it can get, with a 3.5 and 185/60-13 tyres it would barely hit 105mph, whereas a blade with the same
setup would hit well over 120mph.
According to my figures the ZX12 appears to come out top when looking at a gearing/rev limit table
 
Comparison of gearing on BECs
I wish this forum would allow Tabs in the text, then you could write up little tables like this and still retain the spacing / layout!
[Edited on 20/10/05 by ChrisGamlin]
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smart51
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| posted on 20/10/05 at 01:56 PM |
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that, of course, is the other reason you might want a 3.14 diff - if you want to fit 13" wheels not 15"
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ChrisGamlin
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| posted on 20/10/05 at 02:23 PM |
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Those figures are with 13" wheels though, so from that I would say that only the CBR1000 really needs a much higher diff, and if you wanted to
raise the figures a bit you could obviously fit 205/60's rather than 185s
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OX
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| posted on 20/10/05 at 02:59 PM |
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yes ,sorry,im just going from what iv tried and not worked out on the pc i just take it for granted that not many use 13" wheels .
bill and otto with blade engines are running a 3.62 with 15" wheels and they top out at around 120 ish but once they hit 100mph both cars are
slugish to hit the max speed,a diff of 3.3 would kill it.
i had a 3.62 diff in my r1 kit but with 17 " wheels and that maxed out at 125 but that was slugish from 100 mph,a happy medium.
shed with the r1 and 15" wheels has a 3.92 diff and that screams all the way to the red line but with only a 115 mph .he needs a 3.62 ,i think a
3.3diff might be to much after 100mph for the engine.
my busa screams to 120 with 15" wheels and a 3.62 diff ,i have a 3.14 to go in it but i still think im gonna have to uprate 5th and 6th gear,god
damn the busa gear box .
i bet the zx12's power could easily pull a 3.14 and not lose out to much on exceleration.
people say there not bothered about top speed,,cool,,im not either but when you put your foot down and before you know it your poor little engine is
screaming its tits off you start thinking ,i could do with another gear
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ChrisGamlin
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| posted on 20/10/05 at 03:29 PM |
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Yep, but we'd all need more than ~180bhp to get significantly above 130mph (or a lot better aero like a Pheonix or Fury), so if geared for
around that speed you should never be in that situation
Except for the busa and possibly the CBR1000, I think a 3.38 diff is perfectly high enough for most engines, assuming you're not building a
motorway cruiser . According to the old spreadsheet, a Busa with 205/50-15" tyres and a 3.38 would top out at 130mph almost exactly. My
mate's westie Megabusa has pretty much this combo and he couldnt max it out at Spa, Donington or Bruntingthorpe (on a trackday obviously, not
the entire 2 mile runway ). Whacking a 3.14 and say 205/50-15" tyres onto a ZX12 car will gear it to 152mph in top, and 138mph in 5th,
making those two gears almost unusable on track, the only benefit will be a lazy cruising RPM.
BTW, bear in mind that using 13" wheels doesnt necessarly mean low gearing, ISTR a 205/60-13" is the same rolling radius as
195/50-15" for example.
cheers
Chris
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TimC
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| posted on 20/10/05 at 05:13 PM |
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Cossie Diff and CBR1000 anyone... oh no, that's just me!
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OX
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| posted on 20/10/05 at 05:23 PM |
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ok i dont think a 3.38 will be suitable for a blade or r1 with 15" wheels on 60 or 50 profile tyres ,on the track or the road . .
my busa is a little under geared for oulton park and thats how the r500 just got past me ,,but he did tell me after that his car wasnt running that
well hehe .
but we're not just on about the track are we
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ChrisGamlin
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| posted on 20/10/05 at 06:06 PM |
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Hi OX
Im a bit confused why you say it wouldnt be suitable for a blade / R1, because its too high or to low?
Ive had mine geared for under 110mph before using a 3.89 and the 185/60-13 tyres and although it felt quicker (because of all the gearchanges), side
to side compared to a mate's Megablade on both occasions it made no noticable difference to acceleration. You will get through the box quicker
and hit the limiter in top much earlier so the perceived acceleration is greater, but then if Im geared for 125mph or so, 5th gear also hits the
limiter at ~110mph so overall the car would be pulling just as hard in 5th up to the llimiter at ~110mph as in 6th to 110mph with the lower 3.89 diff.
This would be the same if using 15" tyres of normal size rather than my 13s because the rolling radius is very similar.
Chris
[Edited on 20/10/05 by ChrisGamlin]
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andygtt
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| posted on 20/10/05 at 06:51 PM |
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I have to say I always worry when people keep quoting wheel sizes as if thats what decides gearing. As Chris says, its the tyre size that denotes the
RR and thus the gearing.
Is there any way of telling what the diff ratio is without stripping it down?
Andy
please redefine your limits.
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OX
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| posted on 20/10/05 at 07:09 PM |
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well im going on allround drivability ,,ok sheds r1 with the 3.9 diff ,from a standing start is as quick to 115 mph as mine is but from 70 mph upwards
mine pulls away ,if he had the 3.6 diff ,im sure from a standing start it will still be as quick as mine to 100mph but at a rolling speed of 70
upwards i would of thought i will pull away even more...
when i had my r1 indy with a 3.6 diff,my brother had a 1.8 sierra indy ,now my car blitzed it from a standing start but at cruising speed i was
shocked that there wasnt much in it so i would of thought that with a 3.3 diff in the r1 it would of struggled even more against the 1.8 becouse it
hasnt got the umpff to pull the lower gearing at higher speeds
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smart51
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| posted on 21/10/05 at 07:38 AM |
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quote:
Originally posted by andygtt
I have to say I always worry when people keep quoting wheel sizes as if thats what decides gearing.
so a car with 19" wheels will have the same gearing as one with 12" rims? only if the 12" rims are fitted with 195/100005/12 tyres!
Sure, it's the combination of wheels and tyres that add together to make rolling radius, but most people limit their tyres on their sevens to
the range 185 - 205 with 40 - 60 profile. A 195/50 13" has a smaller laden radius than 195/50 15" and 195/50 17"
You needn't worry, you're just being pedantic. When I say "wheel" what I mean is "rim" AND "tyre" as
I never use one without the other.
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ChrisGamlin
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| posted on 21/10/05 at 08:18 AM |
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Hi Ox
I see what you're saying but with a higher diff to get maximum acceleration you'd generally be in a lower gear at any given road speed, so
overall the gearing at that point would be roughly the same, its only if you did roll on tests from a certain speed in a certain gear that the higher
geared car would lose out significantly (eg if measuring 50-80 in 4th for example).
I guess our expericences must differ though because my experience from having had mine geared in various guises is that it doesnt make much difference
on outright acceleration, Ive been out for a few blasts with a mate who's Megablade has a 3.21 and he uses 185/70-13" as road tyres
(so geared for something silly like 145mph), and his certainly didnt lag behind either.
Smart - I think what Andy was saying is that there's little point in just saying a wheel size, you can specify a tyre size and immediately it
gives you all the info you need, but not with a wheel only so at the end of the day you need to know the tyre size whatever.
Chris
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zzrpowerd-locost
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| posted on 21/10/05 at 08:35 AM |
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nowt like abit a banter! 
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ChrisGamlin
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| posted on 21/10/05 at 02:09 PM |
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Yep, all said in good spirits, didnt mean to seem like it was attacking anyone if thats how it came across
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andygtt
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| posted on 21/10/05 at 10:44 PM |
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quote:
Originally posted by smart51
most people limit their tyres on their sevens to the range . A 195/50 13" has a smaller laden radius than 195/50 15" and 195/50
17"
185 - 205 with 40 - 60 profile
You needn't worry, you're just being pedantic. When I say "wheel" what I mean is "rim" AND "tyre" as
I never use one without the other.
I wasn't having a dig at anyone.
Think my point is that if a 17in rim was fitted it would normally have a lower profile tyre to keep the RR the same and thus potentially not effect
gearing at all.
So I wasn't being pedantic, you need to be specific with tyre size or RR when recomending ratios not just rim size IMO, especially when you are
talking about a range of "185 - 205 with 40 - 60 profile".
Andy
please redefine your limits.
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OX
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| posted on 21/10/05 at 11:28 PM |
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quote:
Originally posted by ChrisGamlin
Yep, all said in good spirits,
hehe yip,,like me,you were just saying
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smart51
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| posted on 22/10/05 at 07:43 AM |
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I've had a bad week. This thread cought me at the wrong time. No offence was intended. Of course each wheel has a range of rolling
circumferences but although these ranges overlap, there is a correspondance between rim size and overall size.
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billy
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| posted on 22/10/05 at 08:01 AM |
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And i was getting worried about you lads over here on the dark side so.............whats the answer then????
luego-lo-cost finished,vauxhall 16v 2.0,twin 45s de-dion rear set up
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