!!* Attention lowered 172’s *!!

[Cord-172]

Hey guys,

I have had problems recently when braking at 60-70mph where the arse of my car starts weaving about and skipping on the road behind me. This doesnt happen on a dead straight but will do on the slightest turn.

I also noticed that my rear pads are nearly gone (which for 27K is a bit excessive!!) Apparently this is because I have lowered my car!!

Underneath the car is a load sensor which apparently compensates for rear braking depending on the weight in the car. By lowering it I have somehow tricked the sensor into thinking there is more weight in the car than there actually is - consequently it is putting more effort into rear braking.

I have found this to be quite dangerous because sudden braking can often end up in me fighting with the wheel (and coming off the brakes) to stop the arse of the car from skipping about.

The plan is to speak to Renault today and see if they will do it for me (bet they dont due to the car not being standard any more). If not I will find out how to adjust it and get a mechanic mate to do it for me.

Will keep you posted. Anyone else had similar probs?

 

[R3OBC]

hehehe...............

 

[BRUN]

the 16v has a brake bias valve that needs to be adjusted when lowered.....it might be a similar thing....

 

[Simon172]

Hi cord172 - my car does that and its standard. Brake a little on a fast corner ( i know youre not supposed to but if someone cuts you up...) and the back end starts to overtake. Maybe mines biased wrongly too?

 

[McBunny]

mine did it lots on the trip especially on the ring oh and once in brussles as i was following roamer on the wrong side of the road with cars coming at me lol i was hoping a set of coilovers would fix it but maybe not lol

 

[Cord-172]

I will speak to them this afternoon. If renault wont adjust it they can at least tell me which way to adjust it (maybe its clockwise or anti) then I( can get a mate to do it.

Apparently the rear brakes are only supposed to contribute 30% of the braking. Any more and it gets twitchy. I expect the brake bias valve thingy is the same thing (or related)

 

[Cord-172]

Well suprise suprise Renault wont touch it!! They say they have no specifications to set the vehicle to because it has been modified - however they will show me where the adjustable valve is.

I spoke to R-Tec who said they wont touch it (Wouldnt trust extreme) and recommended Race/Track car engineers. I only know one place in Sandy/Beds that might be able to help with this but if not I am going to take matters into my own hands to adjust the thing very slightly and see the effects!!

 

[BenR]

Um, the rear load compensator is there on all disc braked rears.

Its a little device under the rear and adjusting it is easy. you can do it yourself but there are no set amount.

EITHER, go to a MOT place where they test the brakes on a RR thing. jsut keep slackening it off till it dont lock under heavy brakign or do it on a straight rd. Keep adjusting it till it dont lock under full braking.

Its a MUST do when lowering, surprised you didnt get it done!

 

[Cord-172]

R-Tec said they have NEVER had to do it when lowering a car!! It is difficult to imagine that people dont get it done when it can have these effects

My Mechanic mate is going to adjust if for me tomz. I dont think the brakes are locking but certainly are gripping harder than they should. My rear pads totally need replacing!!

 

[JJ172]

Sounds like a complete red herring to me! Most std 172 Mk2 I know of twitch under heavy braking...a result of a very light rear and a not-so-perfect spring/damper setup.

However, try the same trick on the track and the car brakes very safely, indicating a spring/damper issue. The racers have much the same problem and most of them moan about the twitchness of the car. There is a known cure, which isnt too expensive, and entails a mod to setup of the rear suspension. Im about to have it done to mine (its a Clio Cup Race mod) so will let you know how I get on. In the meantime, the Eibachs have helped no end with sorting the stability out.

 

[R3OBC]

my mate wrapped TWO VTRS due to this!!!! its bloody dangerous

 

[BenR]

huh????

suspension, its KNOWN to be the brake comensator......

the 172 is twitchy, but shouldnt send the rear to cathc the front when braking. Cliocup racer mod....all they have dont to the rear geometry wise are plates which you bolt inbetween teh stub axle to increase camber.

 

[R3OBC]

well all i know is, drove his vtr standard.........braked fine.........lowered 60mm.............arse end locks up and stepped out............

 

[BenR]

and he did it twice!!!

whats that about a fool dont make the same mistake twice?

 

[Cord-172]

JJ172: Yeah but having to come off of the brakes to stop the car from wrapping up on itself is a bit dangerous!! If I had to brake because someone stopped suddenly infront of me I would end up crashing either way!!


Maybe this is why some lowering kits lower the rear less than the front? (like Pi F-25mm, R-15mm)

 

[Cord-172]

Ok - guess what?

My Mk1 172 has no adjustable rear brake bias valve!! Even Renault thought it did until I told them the chassis number. It looks like some (and all Mk2s Id expect) have this valve and some dont.

I can buy a univeral bias valve and hav it fitted (dunno how much this would cost) - Or buy better front brakes to take the stress off the rear brakes.

As it turned out my discs are in fairly good nick and my mate reckoned that 25K for rear pads is quite good anyway.

 

[jimblive]

i had my vtr slammed at r-tec, just 40mm and they told me that they had adjusted the brake balance. if they did or didnt i never had any problems with my rear brakes, just monster lift off oversteer.

 

[BenR]

adj mine today, 5 min job.....jsut need to test it.

 

[Cj/Denmark]

The cars suspension is set up to steer as neutral as possible. Which means that if you brake during hard cornering (or at high speeds), the back end will step out because of the weight transmission. No magic in that - unless, of course, that it really is to biased towards rear braking (is that a term???). Many a french car will do that (oversteer if you lidt off or brake in corners)..



-CJ

 

[BenR]

nope, its got a compensator to adj for carrying load in the rear.

Simple......yes weight transfer durign cornering can affect the rear, but not in the way specified.