43 replies to this topic

[Ricky2772]

...after much mulling over the poor ABS performances, I might want to experiment altering the braking distribution.... I have noted that my rear pads wears out FASTER than the front ones.... ...and that is not completely right, even considering rear engine and traction, still, braking happens mostly in the front, so worse-case scenario, I shoud experience 65f%-45r% wear, and not 40-60.... another thing, on track, ABS cut off, I oftentimes experience rears locking up before the fronts... logic tells me that an overly rear-biased braking power might disrupt ABS funcioning....do you agree with me here?!? so, how the change in ratio gets done? do I need Opel machinery (hence grease-monkeys... ) to do it?

Edited by Ricky2772, 23 November 2004 - 02:58 PM.

[PaulCP]

Ricky sounds like you have some set up problems if the rears are locking. Would be interesting to hear from others who have different size wheels on the front to see if that is part of the problem Rear pads certainly should.t wear before fronts even allowing for the fact that there is less material on the rears when new. Paul

[garyk220]

I remember reading an article that said the braking system has a load proportioning valve on the rear circuit to prevent the rears locking up under emergency braking. I'm sure Lotus tuned this valve as part of ABS brake updates. I'll see if I can dig out the article (it was one of the S2 Exige magazine articles with a side bar feature on the ABS system and interview with Matt Becker). It is possible that changing the weight distribution, the front to rear grip bias (195/225 tyres), and adding downforce with your rear wing has upset the balance of this. We just need someone who knows what they are talking about to help

Edited by garyk220, 23 November 2004 - 03:42 PM.

[Jase_MK]

I oftentimes experience rears locking up before the fronts...

Presumably running wider tyres at the front would be a contributor to this? I wouldn't expect it to happen on a std VX running skinny 175s at the front.

We just need someone who knows what they are talking about to help

Sorry

How about running different pads at the front? RS15 front, RS14 rear

[MikeS]

A friends' Elise has always worn out more rear pads than fronts from the day it was new, so I'd hazard a guess that it's a trait of the car. The rear pads I threw out of my NA when I changed to RS14's were pretty well worn in comparison to the fronts even though the car had only done 6k. It's something ShinyAndy and Performance Braking are looking into though I believe, which is why he's running RS15's in the back with 14's at the front, in comparison to mine running 14's all round. Mine noticeably dives at the front under braking, whereas his now squats on all 4 wheels, so maybe that's a solution of sorts??

[clipping_point]

Isn´t that what we shall use DucatiSennas balance bar for, when it is finished? Also when a car is lowered and stiffened the force will be distributed more evenly. And aren´t the rear pads skinnier than the fronts? That will make them wear faster if it is not set up accordingly.

[Ricky2772]

I was informed by cicastrol that AP racing offers two force valves a lever one and a screw-type...
pretty interesting stuff!!

I might go for one of those....
not sure where to install it...and how difficult it might be...

(in italian)
http://www.gieffesrl...5&type_cat_id=1
http://www.gieffesrl...50-1cd-iss6.pdf

[cyberman]

I have just commented elsewhere that I have the same problem with SBS pads when running without ABS. Lock-ups (only in the wet) occur at the rear first. Fortunately my LSD has stopped this turning into anything drastic as yet. This condition can induce 180 flips if not careful. A good ABS should deal with this but I am reluctant to use the standard ABS because of its other faults. A DucattiSenna balance bar seem a good alternative. Not sure about pressure reducing valves. Earlier experience mixing pads from front to rear on Lotus Elans put me off it a bit - similar problem when cold. However, if front can be guaranteed to work better than rear at all times then experiment not unreasonable. Kind regards - Ian

[Jase_MK]

It's something ShinyAndy and Performance Braking are looking into though I believe, which is why he's running RS15's in the back with 14's at the front

Wouldn't using more grippy pads at the back increase the likelihood of rear lockup, instead of decreasing it?

[barrybethel]

Ricky I have the same wheels and tyres as you for track use and I don't have this problem at all. I pull the abs fuse on track and it's always the fronts that lock up, never the back. Front pads also wear out quicker. I have ebc greens on at the moment by the way. Will be fitting pagids shortly. It's a mystery to me.

[cyberman]

Wouldn't using more grippy pads at the back increase the likelihood of rear lockup, instead of decreasing it?

You would have to think so. And the effect can be very temperature dependent if the pad characteristics change as they warm up.

I am going to change all my disks to get as much pad activation as possible and try some Mintex 1144s in the front to change the balance front to rear in favour of the front. I might then start screwing with mixed pads at the rear to bring back to a better balance (i.e. inside pad = SBS outside pad = Mintex).

What you can't afford is to be locking rears. Without something to protect you from the 180 flip that can be very dangerus indeed. Been there at an earlier time, done that, don't want to again.

BTW, what do people think of as the best disk? I have looked at the available units and, apart from getting some combo aluminium bell units made to suit (a la elise parts S2 with different offset / holes), the off the shelf seems to be Black Diamond (grooved / drilled / combi), Pagid 16 grooved, EBC (grooved & pitted). Weight would be a consideration but no one mentions that except the Eliseparts people (who seem keen to do a variation if one wants it). Wear isn't a consideration. Responsive performance is.

Grooved only seems preferred these days for track. However, I used to like a drilled disk and never had any problems. What do people think of the Black Diamond combi for heavy road use? Anyone tried one?

Kind regards - Ian

[Pidgeon]

Ian, two points, any mix of pads will result in unpredictable braking. Although content with SBS, their cold performance is poor compared to Pagids. Last weekend I followed a slow car down the motorway (60ish). First brake application off the motorway resulted in minimal retardation. This has only happened to me a few times with the SBS, usually they warm themselves up, but the lack of predictability is not confidence inspiring. Different pads with differing temperature characteristics will lead to an interesting drive! I do not know the content of the Mintex, but I am not aware they are carbon/ceramic's. If that is correct they will not be as good as the SBS. As for discs, if money is no object, ali bells are worthwhile to reduce unsprung weight. Otherwise, any other coatings/drillings/grooving are mere fashion and will not assist retardation. I paid £20 each for my discs. There is unanimity RS14's are the best pad for the car. Try some before you try anything else. They are that good.

[Pidgeon]

As for the front/rear wear, I am on my fourth set of fronts, and second set of rears since switching to Pagids. Fronts 14's x 3, SBS x 1, rear, 14's x 2. The rears will need changing before the fronts, so a fresh set of Pagids will be on my Christmas list.

[clipping_point]

Otherwise, any other coatings/drillings/grooving are mere fashion and will not assist retardation. I paid £20 each for my discs.

There is unanimity RS14's are the best pad for the car. Try some before you try anything else.

They are that good.

Drilling/grooving will probably reduce the efficiency of the brakes somewhat, due to the reduction of surface area

[Thorney]

RS14's, 16" front wheel, stock disks



Seems to work on the front for me

[Jase_MK]

Ian, I'd be wary of mixing pad compounds too much. I went for about a week with Mintex 1144 at the front and standard pads at the rear and it wasn't too hot - far too much front bias. The Mintex were so much more grippy than the std pads that only a light pedal pressure was enough to activate the fronts. This wasn't enough to get any serious retardation from the rears though so pretty much all my braking was being done through the 175 tyres at the front and the rears basically were doing very little. The result was lots of ABS activity due to the fronts tyres struggling for grip all the time and not very impressive braking distances.

[cyberman]

Thanks for the advice chaps. This is all very interesting. What we need between us to sort this out properly is a hub / caliper with a big electric motor and 1/4 ton fly wheel then we could do some real controlled testing and getting numbers for different pads / different disks. I have never seen anyone using anything like this but it sounds highly desirable. I understand about the reduced surface area with grooving et all, but hope that may be compensated by dynamic effects from pad clean-up and gas/water escape. So I will experiment with some sort of faced disk. I even wonder if the injection of controlled vibration from the disk surface might not beneficially affect some aspects of system performance (I.m not sure I haven't got at least one sticky slave though no one admits to it). What I ought to do is put a bias bar m/c pair in there then the front / rear balance can be adjusted properly. Screwing around with pad mix to adjust the balance is rather a second order effect but quick and easy to do whilst I sort out getting a balance bar made. I know Pagids are very well regarded but I think I will start with a full set of Mintex 1144. These are reported as so grippy from cold that it seems a good trial. I do need overall gain in the braking as getting a lock up in the dry is all but impossible (i.e. I am not hitting maximum retardation). If the balance is still very off (i.e too much to the rear) then I think a judicious substitution of one pad each side at the rear may give a half way house. It should sit mechanically al right and I have reason to believe the SBS characteristic will not cook-up with temperature to match the Mintex in the range I am interested in (road use primarily). So we should achieve reduced rear braking efficiency which may eliminate the rear lock up situation temporarily till a better solution comes along. I am going to do this next week (booked in with Scared Stiff) I'll let you know how it all goes. Kind regards - Ian

[Jase_MK]

What we need between us to sort this out properly is a hub / caliper with a big electric motor and 1/4 ton fly wheel then we could do some real controlled testing and getting numbers for different pads / different disks. I have never seen anyone using anything like this but it sounds highly desirable.

That was my A-Level physics project - different compounds of brake pad for a mountain bike. I pumped the innertube/tyre full of water for the flywheel/inertia thing...

...hmmm, I'll get my coat

[ShinyAndy]

Too much speculation and guessing here.. as MikeS said, I've been running RS15s on the rear and 14's on the front in the hope to balance the brake bias. It HAS worked, the car pulls up much squarer and has even solved a lot of the ABS issues I was having and NO it doesn't make the rears lockup

[Jase_MK]

and NO it doesn't make the rears lockup

Fair enough, nobody disputes that it works well for you. But for those that are already having rear lockup problems, I don't think fitting grippier pads to the back as someone suggested is going to help them. Wouldn't you agree?