Open V's LSD

[johno]

Has anyone driven one of each on the S series.

Namely a car with a LSD and a car with the standard open Diff.

If so, any opinion on whether it makes a noticeable difference ???

[LeeBee]

Yes, didn't notice any difference whatsoever, I am fitting one to mine but you know why!

Cheers

Lee

[Greenv8s]

quote:Has anyone driven one of each on the S series.

Namely a car with a LSD and a car with the standard open Diff.

If so, any opinion on whether it makes a noticeable difference ???

I've tried three sorts of diff so far. The difference is only significant if you're accelerating hard enough to start breaking traction, while cornering. (If you're cornering hard it doesn't take much acceleration to do this, but a doubt many people would be crazy enough to do this often on public roads.)

With an open diff, there's an unhappy point where the car can either spin the inside rear wheel and shed the excess power, leading to horrible understeer, or spin both rear wheels, leading to loverly oversteer. I found my S2 would often flip between these two 'modes' as the car rolled and pitched, and it was a bit of a guessing game which way it was going to go. I believe it would be possible to vary the balance between these modes using conventional tuning techniques eg softening the rear would make it more likely to slide both rear wheels together so more predictable, but I didn't experiment with this.

With the viscous diff that was standard on the V8S (and on the S4 I guess?) you get the same situation but as soon as the inside wheel spins up a little the diff loads up the outer wheel. As before you get two 'modes' but the result is either loads of tyre squeal followed by oversteer, or a more predictable oversteer. Much better.

With the friction diff that I have now (Chimaeras and Griffiths use a diff that behaves the same I think) both wheels slide together and oversteer is totally controlled by the right foot. None of this doubt about whether it is going to spin the inside wheel up or not, far better traction and more predictable handling.

Hope this helps,
Peter Humphries (and a green V8S)

[mhibbins]

That sounds superb - I *love* oversteer but would definitely like it to be a little bit more predictable.

I rather suspect I don't have a LSD on my s3 but how can I test it to be sure (one wheel on the grass, one on the road)?

What donor car does my rear diff come from and can I get a LSD for it from a different version of the same donor or am I looking at a new one?

Thanks,

--
Mark

[johno]

Jack one side of the car up and attempt to turn the rear wheel by hand (handbrake off, fronts chocked etc etc) If the wheel spins freely then you have an open diff.

If it takes some force to move the wheel but you still can then you have a LSD.

This save on chewing the grass up !!

I think this is right, please someone correct me if I'm wrong.....

[JSG]

My 91 S3xc has a LSD. The original TVR sales brochure shows it as standard equipment.



Edited by JSG on Thursday 25th October 15:52

[Paul V]

In the S book it says the cat models came with the LSD as standard.

[mhibbins]

quote:I've tried three sorts of diff so far. The difference is only significant if you're accelerating hard enough to start breaking traction, while cornering. (If you're cornering hard it doesn't take much acceleration to do this, but a doubt many people would be crazy enough to do this often on public roads.)

Holds hand up

I had one hell of a moment today while accelerating out of a 40-50mph corner when the back end just shot out of line. I just caught it and it swung the other way. I caught that and we were on our way again.

It's my own fault really as I was getting really cocky doing powerslides around roundabouts all morning but at 40-50mph and on a left turn it was a different kettle of fish altogether.

What I think happened is that one of the wheel hit some mud and spun up and all the power went to that wheel leaving the other dead in the water and very suddenly we weren't facing the same way any more.

So, I am even more keen to get a lsd installed. Has anyone done this to an s? Anyone have any idea where I would get the bits and what bits I would need to fit? Anyone?

Thanks,

--
Mark

[JSG]

Mark,

I think the bits you need are 'TVR' and not Ford etc so will harder to find. A specialist breakers may be able to help or try one of the TVR specialists (Thames Valley Racetech are your nearest in Berks). When I was there earlier in the year Steve had various cars in states of canibalism including Ss (?). I have to say that a week ago the yard was alot tidier (Harry's influence) but its worht a call.

The LSD on my S3C worked well - although I have to admit that when I took a mate out in the V8 just after I got it earlier this month the back stepped out even with LSD .

Cheers,
JSG

[mhibbins]

Thanks for that, I'll look into it. I was rather hoping I could raid a sierra.

Don't get me wrong though, I like the back end stepping out, I'd just like power to still be at both wheels so I can control it rather than just save it.

--
Mark

[Paul V]

I presume the cosworth would be fitted with a LSD, possibly the XR4i

[mhibbins]

I've just spoken to thames valley racetech and the part is a modified ford diff from tvr. It's a pretty big job too so could be up to 1k.

They were very helpful though and offered to check over the car and make sure everything else is spot on and then suggest the best way forward.

I'll take a trip over there in the new year.

--
Mark

[LeeBee]

In what way is it modified? ratios etc? as far as I was concerned a Sierra item is a straight swap (not like the item fitted to the V8S though), Peter H may know more?

Cheers

LeeBee
P.S I know of an LSD for £150 if it does turn out to be a straight swap

[mhibbins]

Oooo, dunno. It says in the bible a sierra one should work but the flange sizes might be different and the prop might not be the right length and I have to take it all off to measure it - which kind of put me off that route . I'll try and get more info.

I've had some new tyres fitted which will hopefully make it all a bit more predictable - p6000s. The old viking tech 500s (ahem) that came with it were fun in the dry but rather alarming in the cold and damp. The alignment was all over the place too - the front were aligned ok but not with the rears. Doh.

--
Mark

Edited by mhibbins on Thursday 20th December 19:25

[shpub]

P6000's hmmm. Yep they make anything predictable. As soon as it is wet, they slide. It's that predictable! Only slightly better than Goodyear NCT2s.. If you have crap tyres on the car, it is no wonder the thing slides everywhere!

Get some Bridgestones.

Steve
www.tvrbooks.co.uk

[mhibbins]

I've been using p6000s for 2 years on another car and like them. Like I said before, I like the fact that it slides but would like it to be more progressive and less snappy. That's why I don't like really grippy tyres. I'm not out to beat anyone else in a race, just to have fun.

--
Mark

Edited by mhibbins on Thursday 20th December 23:48

Edited by mhibbins on Thursday 20th December 23:50

[shpub]

To me if the car is continually breaking away and sliding, then it is not coping with the conditions and the car is effectively out of control.

Anyway
let's not bicker about this ... it is your car and NCB.

Steve

[mhibbins]

I didn't think we were bickering - I thought we were having a discussion. Blimey people are so touchy these days

In my opinion the earlier a tyre breaks away the easier it is to control when it does. Clearly this can happen too early such that it breaks away all the time and as you such make no progress. However, I prefer it to happen earlier than many people whose aims are to get everywhere as fast as is humanly possible.

I've always liked the feel of a rwd car and the way it breaks away under power. I have in the past tried to go the way of really stick tyres and removed this element of fun from a car as it did not have sufficient power to break traction cleanly and safely. I don't think the s3 has *that* much power such that if I put on really sticky tyres it would take monumental cornering speed to unstick it and then it would extremely difficult to catch. So I try and go for the middle ground to achieve that balance. If I had a griff or something else a lot more powerful then I would indeed get something a lot stickier.

I would still like a lsd as it would add that extra dimension of control - or so I'm told.

Motorcycles though are a different kettle of fish and I go for the stickiest possible tyre for my fireblade. I *really* don't like it when it skips sideways

--
Mark

[shpub]

quote:
I didn't think we were bickering - I thought we were having a discussion. Blimey people are so touchy these days

I thought so as well but it can degrade so quickly. Emails can also be a little difficult to assess the mood/intent. Back to the discussion...

The problem with less grippy tyres is that the threshold for the car letting go is a lot slower which is why you like it. The problem is that the tyre grip will also determine stopping distances. The less grip the easier it will be to lock up. In slippery conditions, the grip is even less and the onset of a potential skid/slide/tail out is even lower and the ability to control it by opposite lock etc is less as there is less grip on the front tyres.

So I find it strange that someone would deliberate reduce the car's grip and ability to stay on the road and stop. In addition, by default the car must be driven slower because the tyre grip will effectively set its speed threshold so why have a TVR is the first place?

For me, the key to driving safely (and quickly)on public roads is to keep the car/driver well within the envelope so that it is not continually on the edge so that there is enough margin to help get out of a sudden situation. Driving with lower performance grip means that the scope for doing this is greatly reduced. Make an error and it will be a lot harder to recover.

In the end it is a matter of choice, but I wouldn't do it or recommend it.

Steve
www.tvrbooks.co.uk

[mhibbins]

quote:The problem with less grippy tyres is that the threshold for the car letting go is a lot slower which is why you like it. The problem is that the tyre grip will also determine stopping distances. The less grip the easier it will be to lock up. In slippery conditions, the grip is even less and the onset of a potential skid/slide/tail out is even lower and the ability to control it by opposite lock etc is less as there is less grip on the front tyres.

I completely agree. What I'm trying to do is get it somewhere in the middle. The vikings were superb in the dry as you could drift the car really easily yet still make progress. In the wet they weren't too bad but now it has got cold the braking was appaling. I personally like the p6000 and think they give the feel I'm looking for combined with pretty good braking. I do conceed though that I am sacrificing ultimate braking and cornering ability for a bit of fun.

quote:So I find it strange that someone would deliberate reduce the car's grip and ability to stay on the road and stop. In addition, by default the car must be driven slower because the tyre grip will effectively set its speed threshold so why have a TVR is the first place?

I don't get speed thrills from the tvr. I get those from my 150bhp fireblade motorcycle. I can do all the things possible to my tvr and it still won't get even vaguely close. What I'm after is that fun feel I used to get from my old opel manta (don't laugh) combined with great looks, great sound, easy maintenance and a convertible. I don't care about ultimate performance at all.

quote:
For me, the key to driving safely (and quickly)on public roads is to keep the car/driver well within the envelope so that it is not continually on the edge so that there is enough margin to help get out of a sudden situation. Driving with lower performance grip means that the scope for doing this is greatly reduced. Make an error and it will be a lot harder to recover.

I completely agree with you. When I do any distance I either go in the mondeo with the family or on the bike. I use the tvr for a bit of fun and this is the way I like my cars to be to achieve that fun aspect.

--
Mark