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]
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
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]
unless your going for a zx12 or the busa i wouldnt think you'll need anything more than a 3.6* diff
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...
We have a 3.62 LSD in ours and top speed on Dyno was 129.7mph.
Fast enough for me. (for now)
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.
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]
that, of course, is the other reason you might want a 3.14 diff - if you want to fit 13" wheels not 15"
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
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
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
Cossie Diff and CBR1000 anyone... oh no, that's just me!
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
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]
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?
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
quote:
Originally posted by andygtt
I have to say I always worry when people keep quoting wheel sizes as if thats what decides gearing.
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
nowt like abit a banter! 
Yep, all said in good spirits, didnt mean to seem like it was attacking anyone if thats how it came across
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.
quote:
Originally posted by ChrisGamlin
Yep, all said in good spirits,
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.
And i was getting worried about you lads over here on the dark side so.............whats the answer then????
I'm not sure the answer myself..... I'm using an R1 engine with 215/40/17s and have a few diffs that I could install.
1 is out of Mr masons R1 indy with LSD.
2 is an open diff with no LSD.
3 is a big rwd cossie diff.
I'm favouring the open diff initially as whilst I'm used to this kind of car and much prefer an LSD, however the wife will be driving this
also and she's not.... so the safer handling with the open diff may be a good break in for her.
The open diff also saves in excess of 10kgs over the LSD one and the cossie is heavier still.
Do you have to strip the diff to find out the ratio?
[Edited on 22/10/05 by andygtt]
Ran some calcs on my ZX12R powered car and got the following...
205/50x15 tyres so (102.5mm/25.4)x2 + 15 = 4.035 then multiply by 2 and add 15 inches for the wheel... 23.07 inches diameter... x 3.142 = 72.5 rolling
circumference...
12,000 rpm rev limit /1.596 primary ratio / 1.033 secondary ratio in top / 3.62 diff ratio = 2011 revolutions of wheels at full speed...
2011 x 72.5 = 145797.5 inches per minute / 63,360 inches per mile x 60 minutes in an hour for max speed...
138mph theoretical
Well that seems quick enuff for me looks like ill take out me 3.38 and put me 3.6 in. think i may go back to no lsd,having now tried both now,
having lsd dont make a quicker car. and yeh the weight saving meens i can eat a few more pies
You guys should really use manufacturer's specs for tire size. The OD of the actual tire will always be a bit different then doing the math.
Or just take our Dyno figures as being somewhere near. 129.7mph with 3.62 diff and 195x55x15's 
quote:
Originally posted by Hellfire
Or just take our Dyno figures as being somewhere near. 129.7mph with 3.62 diff and 195x55x15's
As originally put before it was edited.......quote:
and yes an lsd wont make you faster..
Bit of a sweeping statement that aint it, that an LSD won't make you faster?
In most cases an LSD will make the car faster because it gives you more grip coming out of corners and allows you to use full throttle earlier,
although obviously it does depend on the setup of the car and the ability to get the right diff / setup so as not to compromise turn in, and also
depends on the type of driving you are doing, on the road it will make sod all difference in 99% of situations, and the other 1% you probably shouldnt
be in those situations on the road anyway
On track though, it can make a huge difference to the car's lap time, without an LSD my live axle'd car used to spin up the inside wheel on
the exit of corners all the time, eating the tyre and allowing anything with decent grip to pull several car lengths on me going onto the straight.
Chris
[Edited on 23/10/05 by ChrisGamlin]
quote:
Originally posted by ChrisGamlin
Bit of a sweeping statement that aint it, that an LSD won't make you faster?
In most cases an LSD will make the car faster because it gives you more grip coming out of corners and allows you to use full throttle earlier, although obviously it does depend on the setup of the car and the ability to get the right diff / setup so as not to compromise turn in, and also depends on the type of driving you are doing, on the road it will make sod all difference in 99% of situations, and the other 1% you probably shouldnt be in those situations on the road anyway
On track though, it can make a huge difference to the car's lap time, without an LSD my live axle'd car used to spin up the inside wheel on the exit of corners all the time, eating the tyre and allowing anything with decent grip to pull several car lengths on me going onto the straight.
Chris
Errr........
quote:
and yes an lsd wont make you faster..
it may make you push on in a corner, but it will make the back end well driftable..
oh fgs
sometimes I wonder about IQ's
I'll edit it to make it clearer for the numpties who couldnt understand...
[Edited on 23/10/05 by G.Man]
Likewise!!!
Read it out of the context you seem too have meant it. When saying "it wont make you faster"the logical conclusion to come to is that you
mean round a track / down a bendy road, its so bloomin obvious that it wont make a jot of difference to top speed so why would anyone think thats what
you meant??
Chris
If you are going to be pedantic, then I will add that the extra weight will make you slower...
Im not being perdantic at all, you seem to write stuff which could be misleading (presumably unintentionally), but get upset when people question what
you say.
Anyone with an ounce of mechanical knowledge will know that the only thing that is going to affect top speed is the actual gear ratio of the diff
itself, whether its an LSD or not has absolutely no bearing on that. Your post made the statement about an LSD not making you quicker then listed a
reason why (because it pushes you on in the corners), so the logical conclusion is that you're talking about an LSD not making you quicker
through corners!! 
[Edited on 23/10/05 by ChrisGamlin]
quote:
Originally posted by billy
W having lsd dont make a quicker car.
LOL!!! 
I may be wrong but in exactly the same way, I think most will assume that billy was talking about his overall experience with an LSD, that he found
that it didnt make his car faster overall, which may well be true for his particular setup / driving style etc, Im not arguing that.
However, I really fail to see the logic of your penultimate comment, if you can put the power down better, the car WILL BE QUICKER, it will get from
point A to point B in a faster time than it would without the LSD, so by definition its QUICKER!!!!!
Its not just control of the back end that it gives you, its outright grip. If one wheel is spinning with an open diff you are not accelerating as the
wheel not spinning is not receiving drive. With an LSD this doesnt happen, the (usually outside) wheel that isnt trying to spin still receives a
portion of drive whatever the inside wheel is trying to do, so you're always gettign drive and accelerating.
To borrow a GIF from the WSCC site
Jeez
:patronise mode off:
I don't need a lesson in how an LSD works and the benefits...
With an LSD both wheels can spin up, so they are NOT always driving... Extra weight means the car may be slower in a straight line... all sorts of
other factors come into account...
Potentially the car may be quicker on a lap... thats as far as it goes... there is no WILL about it...
I should have known that with an avatar like yours, you could NEVER EVER be wrong about anything
Hands up, I did say the wheels were always driving and the car always accelerating, which although technically accurate (unless the tyres have zero
coefficient of friction when spinning), I can see what you are saying. What I meant to highlight was that both wheels are ALWAYS receiving drive,
unlike an open diff that does give virtually zero traction in certain circumstances, with one wheel spinning with no weight on it, and the other
freewheeling. As Im sure you know, if an LSD is working, you need to overcome the grip of both tyres before they will spin up, and because the sum of
weight on the tyres will always be significant (ie one tyre might be lightly loaded but the other will be heavily loaded), there will always be an
element of significant forward traction even if its reduced due to both wheels spinning, and the occasions when spinning will occur will be far less
compared to an open diff and an unloaded inside wheel, so less occasions where you lose effective drive.
Apart from that, nowhere did I claim that in all circumstances an LSD WILL be quicker though, and in a previous post actually said that in certain
circumstances it wouldnt.
[Edited on 23/10/05 by ChrisGamlin]
Don't know what you mean about my avatar, but whatever....
There is absolutely no point in arguing over your misinterpretation of what I wrote...
Technically you are correct as am I so we are just arguing with no gain...
I am just adult enough to let it drop...
"G Man"
If it was my misinterpretation then I apologise, but I dont apologise for questioning it because Im sure that 99% of people that read the comment drew
the same conclusion.
Up until the point where you started personal digs at me such as questioning my IQ, it was a perfectly light hearted thread, so please do not insult
me further by saying that you're the one thats "adult enough to let it drop"
Sorry chaps... I only asked what I thought was a simple question.
40 odd postings later... I feel so guilty..I have decided to part with it. I only got it the other day.
http://www.locostbuilders.co.uk/viewthread.php?tid=33267
Anyone interested see the above link.
Grrrrrrrrr you ungrateful........
Well i will say this.......i think the viscous lsd on the sierra diffs are shite!!! only seems to be noticable when doing dohnuts on the local
roundabouts, nice little argument by the way when i ment it didnt make it any faster i ment overall with my tame kina driving
When judging an technical setup (an car)
you have to look at minimum laptime you can get. In the same circumstances (trackstate,driveining line etc.)
then with LSD you are faster wy? because an inside tire loses weight due to the roll effect... also the roll on an Seven is much less then on an
cossie....
Also i saw some one saying topspeed
and weight.... but those 2 haven't todo with eachother....
only acceleration does...
(99,9% of topseepd is down to power/ aire resistance==> aero dynamics)
power means engine power but also gearing offcourse.... in fact we talk about force ==> Torque!
i will have an great problem.....
i Have an BEC
with an 3,92 diff (LSD)
and i use 195/45/R15 Tyres...
i think i should be lucky to top out at 100Mph?
p.d. i don't know my primary gear ratio..in my hayness it doesn't talk about it with any word..only the rest of the gears i can find
beginning the chapter..
Tks
p.d. what i do know is the bike sprockets size and the rear tyre size.. this could be usefull, also i know its topspeed..
(245Km/h)
how much does an fireblade (900) has??
[Edited on 26/10/05 by tks]
Its a Pan Euro engine you have isnt it?
If so a quick Google brings this up
Primary reduction 1.829
Gear ratio
1st 2.266
2nd 1.500
3rd 1.142
4th 0.916
5th 0.758
Works out at around 122mph with a 3.38 diff, or 105mph with your diff.
Why such low profile tyres though?
Edited to add, those figures assume (a total guess of) a 9,000rpm red line.
[Edited on 26/10/05 by ChrisGamlin]
i used an V4 the VFR 800 '98 injection.
hope google will still do the trick..
wy? they came with the rims (TWS IMOLA) and are brandly new i could pull the samll pieces of wire of them..
Tks
Ah sorry, knew it was a V4 but got the wrong one!
The reason I ask about tyres is that on such a light car, low profile tyres can really hurt the handling, big wheels for show, small wheels for go
[Edited on 27/10/05 by ChrisGamlin]
Primary reduction 1.939 (64/33)
Gear ratios 1 2.846 (37/13)
Gear ratios 2 2.062 (33/16)
Gear ratios 3 1.578 (30/19)
Gear ratios 4 1.291 (31/24)
Gear ratios 5 1.111 (30/27)
Gear ratios 6 0.965 (28/29)
Final reduction 2.687 (43/16)
Dunno if they are through.. but if they are right..i will deffo need another diff....
Tks
3.6 will be the way to go.. the only bad news is that i have remounted one mounting for my diff on my Velocity XT...
7inch?7,5inch diff?
3.38 from a sierra diesel and space the diff
I think i can be lucky that i have an bike with overdrive in the box...
Think its time for 55 tyres and an 3,62 diff....
In this setup it tops out at 168Km/h hitting the limiter in top gear!
but at cruising (would be main goal for me, daily use)
i need 8400Rpm for 120Km/h max speed here.. think the fuel consumption will be high at that engine speed.
If i fit 55 tyres and an 3,62 diff.
It will top out at an nice 195km/h (hitting rev limit)
And 7200rpm for cruise speed (120Km/h)
Can anyone confirm this?
if this looks to much for my engine (782cc) then maybe 3,62 and 50will be the combo.. 189Km/h hitting limiter and 7500rpm for 120km/h....
What tyres do we use over here???
Chris??
If you download the spreadsheet I use from here, just edit it for the figures you have for
your engine and tyres etc, and it should give you a good idea.
Chris