43 replies to this topic

[ShinyAndy]

I actually think it's more to do with the fronts doing too much work and the rears not enough. The front dives massively under heavy braking (highlighted even more by using wider grippier tyres to the front), the rears have a tendency to lock due to the weight transfer to the front. By balancing the braking ability (increasing rear brake performance) the car tends not to dive and thus reduces the tendency to lock the rears The ideal situation would indeed be to change the brake bias via an adjuster to get it right for your brake/tyre/wheel combination and the road/track conditions. However if a simple change of pad material can almost offer the same results then it's surely worth a shot ?

[Pidgeon]

I think we would all agree there is more weight transfer with the Turbo's than N/A's. I am happy with my distribution and have no plans for 15's on the back. If dive is THE problem, then perhaps stiffening up the front is the way to go

[cyberman]

The rears locking first is a big safety issue. It needs to be avoided if at all possible. An active ABS which knocked them off would be OK. My limited slip diff helps to stop it becoming a problem. But lock 'em hard and you can be very badly out of order. I would much prefer the fronts to bottle out and lock just before the rears because its a lot more manageable just to come off the brakes and deal with the issue than it is to have to deal with the thing doing 70 mph steering through the rear window... I agree about the dive issue though. It is a bit soft when provoked - not that I ever really see it on mine. Ian

[MikeS]

If dive is THE problem, then perhaps stiffening up the front is the way to go

That's fine if you plan to switch to Nitrons or something, but for those of us happy with the suspension why stiffen it up when a simple change of brake pad could do the trick?

FWIW though on my NA I've not had an issue with the rears locking up, it's always the front that triggers the ABS and to do that I've really got to be trying, even braking very late into the hairpin at Anglesey didn't trigger it very often.

[cyberman]

Well, its taken me a little while to report on the experiment but a number of things got in the way. A complete review of why I feel the Moon has been in Uranus (or rather mine) is available on submission of a pint of best. I had an accumulation of things I wanted doing, fit new uprated drive shafts, sort the brakes, twiddle with the suspension so saved them all up till second week of Dec and took everything up to Steve, Wayne and Dave at Scared Stiff. Paul (Ducati996Senna) produced some excellent uprated drive shafts and these were fitted without bother. Steve got the full spec from GKN and it is impressive. I think the splines were slightly "pinched" to reduce play and this made fitting not quite a hand push but it all went in OK. They look superb. If anyone needs some OEM drive shafts let me know please. The developing problem with my brakes (didn't work worth a pinch of sn*t, locked the rears) turned out to be cross contamination. The SBS pads had been fitted previously as a quick experiment and instead of getting better as they ran in got worse. I had plain disks which had built up a surface layer of the OEM pad material. This had transferred onto the new pads building high spots which effectively stopped the pads working until they were deglazed. It had got to the state where after a certain point it didn't matter how hard you pressed the pedal you didn't get any more braking. The alternative strategy is to spend 2 hours with wet n dry cleaning up the disks before putting the new pads in. I had decided to fit some Pagid 16 groove disks whilst I am checking out getting aluminium bell disks made and these have solved any remaining problem. I think if I had grooved disks fitted in the first place the problem likely wouldn't have arisen. The interface between disk and pad is quite active - they moan at you when used in quieter moments. I have no doubt pad wear rate is likely higher - but thats a small price to pay for the brakes working properly all the time. I also had the brake hoses converted to stainless braided type and the brake fluid changed to 5.1. There is still some mechanical slop in the system but once the pressure comes on the pedal is hard and the braking effective. Even the ABS seems to work reliably (not that I am fond of ABS but trying it was part of the experiment). The balance to front may be a little excessive but I can now lock wheels with the best. Not quite at any speed but from about 60mph no bother. On a dry road the ABS will cut in from about that speed. I need to do some comparative stopping distances. The SBS pads don't seem any problem from cold - they seem to be at good efficiency by the time you have the pedal down, they don't pull. They don't seem to throw a lot of brake dust (although maybe the rain is keeping the wheels clean). They do squeak quietly at low speed / low pressure sometimes - certainly not squeal. I didn't suffer from fade with them at Bedford on the 11th December. And I was using them hard (it was the long circuit). Presumably the ceramic backing helps to keep heat from the slave piston. There was a chap there with a supercharged NA who had the horrid experience of boiling his brake fluid. I think he said he was running Mintex and 4.1 but I can't swear to it. Steve and I had discussed fitting Oehlins to the car but without some sort of spec or a trial I was bit reluctant just to bolt them on (they aren't cheap). In the end we compromised on Nitrons and Eibach springs as selected by Steve. Ride heights and geometry have been adjusted to suit and the set-up tested around the excellent roundabouts of Daventry... For track work the set up is very good. Unfortunately I could only do 12 laps at Bedford before my alternator belt departed so I didn't really have time to settle to consistent lapping on what to me was a new circuit and a near new car. But it was enough to get the flavour even if I am 28 years out of practice. I did find I didn't "learn" the circuit anywhere near as well as I remember doing in the past. Whether thats old age or lack of practice I am not sure - the latter I suspect (hope). The standard VXT setup suffers from roll oversteer which isn't tidy. The new set up doesn't. Basically between the increased spring and damping rate and realignment the car is operating in the linear region before roll starts to reduce rear end grip. It feels incredibly well planted. Even under extreme provocation I never felt it wasn't entirely predictable. The standard VXT can also suffer from poor front end bite and turn in and that seems to be largely cured. The car turns in precisely and steers excellently on the throttle. The only remaining serious handling issue is that on full bore coming out of opening bends there is a tendency to push wide at the front. This is mainly 3rd gear territory above about 200 ftlbs I guess - but with 270 on tap that can be wasted acceleration. As I'm still on Potenzas this may cure somewhat with a tyre with a bigger contact patch. Otherwise downforce on the front it will have to be. 16 inch fronts next stop I guess. For road use I find the set-up a little firm. There is more high frequency energy communicated to the chassis (and the cervical vertebrae and teeth). If one isn't planning to race then it could really do with a switch selectable road / track setting control for damper / spring rate / ride height. We will do a little work on this. But if you want to push it on the road then it is ultimately quick and safe and, as wellying it flat out on bends in third is unlikely (well around Henley) the handling is spot on at all times. So, overall, I am very pleased with the outcome of the experiment. The Pagid 16 groove disk, stainless braided pipes, 5.1 brake fluid and SBS pads have fixed the brakes into the pretty good category. The Nitrons and Eibach springs with the Scared Stiff alignment have done wonders for the handling. The real bonus was doing a couple of laps with Steve in his "training BMW". Relentless aggression and commitment, consistent speed and bold precise car control. I haven't had such a good time in years and I'm a lousy passenger. I'm a bit cross with Vauxhall about the alternator belt. That was likely the only day for me to go on a track till February because of my chemotherapy schedules. 12 laps. I could have done 40 easy. Its a known problem with a simple fix. They could have told us so we could have had it done. I'd have paid for it even. Ba****ds. BTW, I found I suffered from fuel starvation on the back straight on anything less than half a tank. I suppose the fuel tank is unbaffled? It must be the rather good left hander which goes on and on unwinding into that straight slinging the fuel to the right and the air bubble in the pipe catches up with you a couple of hundred yards later. Oh yes, and the battery moves about as well even though nominally clamped. It needs some packing either side in the tray to stabilise it. Plastic container or something similar each side maybe? Phew. Well I hope that was interesting. It has been fun for me. Without the enthusiastic support and help of the guys at Scared Stiff I would never have got it together. Kind regards - Ian

Edited by cyberman, 19 December 2004 - 06:49 PM.

[ShinyAndy]

whilst I am checking out getting aluminium bell disks made

Ian,

I'm still in the process of getting these sorted, as far as I'm aware the disks have been cast and the bells are being machined (of course Xmas is in the way so things will probably grind to a halt - pun intended )

Let me know if you're interested in a set ?

[cyberman]

Let me know if you're interested in a set ?

Oh, yes, probably. There seems no point in getting two lots made if the first is to scratch. I had missed any discussion of these. Do you have a spec? Grooved? Weight? Cost? Point me at where this is all set out?

I have been talking to Geary at Elise Parts and the one we have been discussing is based on the Elise Series 2 design they have. Same braking element just a different bell.

Regards - Ian

[barrybethel]

Ian, that was a very interesting post. Keep us posted on any developments on the "road and track" suspension settings. I find the springs that came with my nitrons are far too hard for the road. I am toying with the idea of going softer and fitting an adjustable roll bar that can be firmed up along with the dampers for track days. What do you think?

[Thorney]

I'd be interested to see what spring rates on the Eibach were? Interestingly enough I've found the aero pack has stopped the rears locking (only one test so hardly scientific), see other thread on wing test for the details. I get the AP kit on the car in Jan so we'll see how they shape up. Bottom line I don't think stock set up is capable for the car, is was designed for the S2 which weighs 100kg's less so I fundamanetally think we need more if we're going to track them.

[cyberman]

I am toying with the idea of going softer and fitting an adjustable roll bar that can be firmed up along with the dampers for track days. What do you think?

I think it would be a very interesting experiment. It was my initial thought on the subject too. But like all things, sometimes its the "easy to do" rather than the best which happens.

I don't think there currently is a rear roll bar (is there?) so how are you going to mount it? Making a front adjustable arrangement would be no trouble and IIRC Lotus have something suitable on the shelf (5 settings - probably of an Exige but I would need to check).

How soft were you thinking of making the springs? Taking them back to OEM would probably be too soft on pitch even though, as you would have the roll under control, it would not be quite so significant from a handling point of view. Steve was showing me some V expensive dampers the other day (£800 a corner) which have both high and low speed bleed settings. These might be good within this context for extra damping the essentially slow roll and pitch whilst leaving the high speed surface control intact. I'll talk to him about it this week.

I will also investigate what might be made / procured for remote ride control (ugh) as the idea of changing wheels each end of a track day and making multiple mechanical adjustments starts to take the gloss of things a bit. It starts to make buying a Radical and a trailer definitely more attractive.....

But if you were minded to make the experiment I'd be with you on that.

Ian

[cyberman]

I will also investigate what might be made / procured for remote ride control

Well things have come on. I have been looking at magnetic rheolytic dampers. I have .pdf file here to upload. BTW what is the official way to do this? It can't be right I have to upload them to my website and then crosslink, there must be a file repository on here somewhere. If someone can put me out of my misery of ignorance I'll upload it.

Regards - ian

[Ducati996Senna]

Ian, the tank is baffled.

[barrybethel]

Ian Have you seen the thread on spring rates? It would be very useful if you could add yours to it. If you don't mind that is. I was thinking of perhaps going back to something about as hard as a standard vxr, which you will see from the other thread is still quite a bit softer than mine. You're right, there is no rear bar available AFAIK. I already do swap wheels each end of a track day and it's not that much of a pain really. It will be even easier when I get a trolley jack that will go under the car without having to reverse it onto bricks first! Paul How do you find your adjustable bar? Have you had the chance to play about with it a bit on track?

[cyberman]

Ian,

the tank is baffled.

Paul

Oh dear, then so am I, as I was definitely suffering fuel starvation until I filled up above half a tank. The problem only arose on the long straight following the big left hand corner down on the south circuit.

Those laps with no fuel starvation VMax 140+ indicated. With fuel starvation coughing and banging at about 100mph.

As it was only my first 4 laps or so I didn't have the problem (the alternator belt came off almost immediately after filling up) I rather hope to see 150+ next time out.

I wonder if there is anyway to make it more baffling (like get some foam into the tank) without cutting it open? I guess not but if anyone has done it it would be good to know. I suppose the other question is "has anyone else had the problem"?

Ian

[cyberman]

I have been looking at magnetic rheolytic dampers.

These here magneto-rheological dampers look very interesting. Basically a damper where the viscosity of the working fluid is directly controlled by a magnetic field. I think they are fitted to this years Corvette.

The magnetic field is generated by an electric current (max 5A per damper). Its a DC effect with a response time of the order 2mSec (err, 1/500th of a second). Microprocessor controlled for semi-active suspension if you want it.

I haven't yet found enough hard tech stuff to decide whether they have the working viscosity range we would need but prima facie it looks like it. This seems a much better solution than a damper with two stacks of disks which can be alternately selected or sticking a motor on the side of a damper to wind it up and down.

I haven't found after market product yet but the company who holds the IPRs does do after market and is pushing into European car manufacture with it. I think it may be time to interest a specialist damper manufacturer in the topic if they haven't already noticed.

As to springs, I haven't yet decided if I like the idea of running a compressor in the car... It might be possible to do a two setting spring with an extra torsional spring in each corner that could be run clamped or free dependent on track or road use. However, this still leaves the ride height unaddressed and that seems the nastiest problem without the compressor. I'll continue looking / cogitating.

These guys had interesting product but not quite as we need it: www.varishock.com as do www.delphi.com (magneride).

Regards - ian

[cyberman]

Have you seen the thread on spring rates?

I already do swap wheels each end of a track day and it's not that much of a pain really.

Nope, where does it lurk? I don't actually know exactly what they are as Steve fitted and set them up when I wasn't present. However, if it isn't his trade secret, I'll find out and post it. I have a reasonable idea what they are.

How do you get the wheels home? They can't possibly go in the boot and I don't really see them going where the blonde should be fitted.

Ian

[Timbo]

Ian, i would be interested to know what settings you have your nitrons on. Cheers Tim

[ShinyAndy]

think that's the least of your worries mate Ian, I'll get full details to you about the brakes in the New Year

[cyberman]

Ian, i would be interested to know what settings you have your nitrons on.

I refer you to the answer given above about springs. However, I have reason to believe that the rears are on 6 clicks. The fronts are definitely softer. I'll check and find out. Trouble is its not much use without knowing the spring rate.

I actually think the rears pretty near spot on as long as you aren't driving on pave. Then the communication is quite direct... I am getting used to the set-up too.

Ian

[Thorney]

I'd have thought playing with the suspension settings would be better first step than 'magneto-rheological dampers'