Brake servo upgrade? would like some extra assistance....
Discussion
ok so my brakes feel pretty s
t no initial bite and really have to push hard on the pedal to slow it and just feels all wrong (dead with no feeling)The pads might aswell be just blocks of wood!
the rear calipers had a rebuild with new seals, and I have fitted a new master cylinder.
front calipers are brembos (Porsche) front discs are Audi can not remember the exact size or model but something like 320x30
rear discs are mondeo 280x12mm and stock rear esprit calipers (carries had to be ground wider to allow extra disc thickness)
this setup should be great and its just not working?
as far as I can tell the servo checks out ok? when I start the engine with my foot on the pedal it goes down a touch, but when driving it feels like I have no assistance?
pedal is firm and have to push really hard to get the brakes to work.
done searches on Google for checking the servo like:
engine running apply brake pedal , turn off engine hold pedal for 30 seconds no movement = servo good
foot on brake pedal start engine pedal goes down a touch = good servo
etc, etc, all checks out but don't feel like its working when I drive the car?
do I need a bigger servo? or is something wrong that I have missed?
forgot to mention, the discs were new, front and back and the pads used but really thick with hardly any use so reused them.
I did place a sheet of sand paper on a flat surface and gave the pads a gentle clean just to true them up with a new flat surface.
Have driven maybe 150 miles so should have been enough to start working by now but still crap.
I did place a sheet of sand paper on a flat surface and gave the pads a gentle clean just to true them up with a new flat surface.
Have driven maybe 150 miles so should have been enough to start working by now but still crap.
Just a couple of things that may or may not help.
Your flat on the pads may not be the same as the flat on the discs, so they may need a LOT of bedding in, I would change them for good quality new ones personally as they could be contaminated, also were the discs cleaned first, as they have an oily residue for rust protection from new.
Your flat on the pads may not be the same as the flat on the discs, so they may need a LOT of bedding in, I would change them for good quality new ones personally as they could be contaminated, also were the discs cleaned first, as they have an oily residue for rust protection from new.
It might just be the pad material rather than bedding in. You should be able to see the contact area on the discs where the pads are meeting after a hundred miles or so, and if it's a full depth contact patch then maybe look at the actual pad material rather than changing servo's.
When I bought my Elise S1 I really couldn't get on with the brakes, they may have been perfect on track but felt just as you describe on the drive to work in a morning. So I swopped them for Mintex with a different pad material - the difference was like night & day. Lots of initial bite and they felt transformed. No doubt a softer pad and more likely to fade on a track day, but ideal for road use.
When I bought my Elise S1 I really couldn't get on with the brakes, they may have been perfect on track but felt just as you describe on the drive to work in a morning. So I swopped them for Mintex with a different pad material - the difference was like night & day. Lots of initial bite and they felt transformed. No doubt a softer pad and more likely to fade on a track day, but ideal for road use.
Is the piston area different in the new callipers? If so you will have changed the mechanical advantage at the pedal. Are the master cylinder bores the same as stock of different? The master cylinder bores need to be chosen to match the callipers.
Putting a bigger servo on will just be masking the problem, best to try and sort it I'd say.
Putting a bigger servo on will just be masking the problem, best to try and sort it I'd say.
thanks for the help guys I will try and answer some more questions and add more info which may or may not help.
The pads are factory oem road pads, I had already checked to make sure they did not have race/track pads (I also had that problem before on another car) I have not ruled out the option of changing them yet and putting in new pads just to make sure they are not at fault but as already said they are road pads and in good condition.
The complete system has been changed about a lot, the stock brakes were poor when I brought the car, and as I was ripping it all apart and fitting the V8 engine had already planned to upgrade the brakes. The rear calipers are original (but have been rebuilt with new seals) and so is the servo and brand new stock master cylinder.
I have asked other owners of Esprits who have also changed calipers upgrading to 4 pots etc and they have all kept the stock servo and master cylinder?
so no the master cylinder bore is not matched to the front calipers, and I would not know how to do that?
The servo is getting vacuum but if its enough I don't know? the engine is twice the size now and the servo take off being used is the same location on the V8 engine?
I think part of the problem could even be me! I am used to driving newer cars which all have great brakes (easy and over assisted) and driving this old 34 year old car! is just more work to push the pedal down hard?
I have just brought a BMW 7 Series servo and master cylinder on greedbay, will have a play with fitting the servo first as it looks like the double servo type so will give a lot of assistance and maybe use/try the master cylinder as well. Its not costing much just time making it fit with some brackets/adaptor brake pipes etc. Building these Frankenstein cars are a lot of trail and error getting things to work right or how you would like them to be.
I also plan to upgrade the rear calipers to some bigger units as the V8 engine is a touch heavier than the old 4 pot that got jettisoned!
Its not built for track days or chasing lap records just fun. So any upgrade that makes life easier driving it is welcome. Being able to stop really quick with little effort is high on the list of upgrades!
The pads are factory oem road pads, I had already checked to make sure they did not have race/track pads (I also had that problem before on another car) I have not ruled out the option of changing them yet and putting in new pads just to make sure they are not at fault but as already said they are road pads and in good condition.
The complete system has been changed about a lot, the stock brakes were poor when I brought the car, and as I was ripping it all apart and fitting the V8 engine had already planned to upgrade the brakes. The rear calipers are original (but have been rebuilt with new seals) and so is the servo and brand new stock master cylinder.
I have asked other owners of Esprits who have also changed calipers upgrading to 4 pots etc and they have all kept the stock servo and master cylinder?
so no the master cylinder bore is not matched to the front calipers, and I would not know how to do that?
The servo is getting vacuum but if its enough I don't know? the engine is twice the size now and the servo take off being used is the same location on the V8 engine?
I think part of the problem could even be me! I am used to driving newer cars which all have great brakes (easy and over assisted) and driving this old 34 year old car! is just more work to push the pedal down hard?
I have just brought a BMW 7 Series servo and master cylinder on greedbay, will have a play with fitting the servo first as it looks like the double servo type so will give a lot of assistance and maybe use/try the master cylinder as well. Its not costing much just time making it fit with some brackets/adaptor brake pipes etc. Building these Frankenstein cars are a lot of trail and error getting things to work right or how you would like them to be.
I also plan to upgrade the rear calipers to some bigger units as the V8 engine is a touch heavier than the old 4 pot that got jettisoned!
Its not built for track days or chasing lap records just fun. So any upgrade that makes life easier driving it is welcome. Being able to stop really quick with little effort is high on the list of upgrades!
s1v8esprit said:
the rear calipers are original (but have been rebuilt with new seals) and so is the servo and brand new stock master cylinder. I have asked other owners of Esprits who have also changed calipers upgrading to 4 pots etc and they have all kept the stock servo and master cylinder? so no the master cylinder bore is not matched to the front calipers, and I would not know how to do that?
I'm not familiar with OEM Esprit front calipers or the ones you've gone for but as a rule of thumb, if you change the front calipers for ones which have either larger or more pistons, then they'll need more fluid to activate - logical ? This might mean that you get excessive travel at the brake pedal, in which case you'll need a larger bore master cylinder. But equally you might find that the extra travel isn't a big deal and gives more feel to the brake progression - it's a personal thing.It's easy to calculate because it's just a volume calc for each piston movement and then you cross reference back to how much travel & fluid displacement you get at the m/cyl. But most folks just do the "suck & see" method, especially if you're following a path someone else has travelled before.
The trouble is modern cars are just so good and we're used to light brake pedals which happen over a short travel. That's not always the case with cars from ye olden days.....
b2hbm said:
I'm not familiar with OEM Esprit front calipers or the ones you've gone for but as a rule of thumb, if you change the front calipers for ones which have either larger or more pistons, then they'll need more fluid to activate - logical ? This might mean that you get excessive travel at the brake pedal, in which case you'll need a larger bore master cylinder. But equally you might find that the extra travel isn't a big deal and gives more feel to the brake progression - it's a personal thing.
It's easy to calculate because it's just a volume calc for each piston movement and then you cross reference back to how much travel & fluid displacement you get at the m/cyl. But most folks just do the "suck & see" method, especially if you're following a path someone else has travelled before.
The trouble is modern cars are just so good and we're used to light brake pedals which happen over a short travel. That's not always the case with cars from ye olden days.....
indeed, I think the master cylinder is ok? I don't have excessive travel in the pedal I thinks its just me needing a better servo for my spoilt lazy weak leg!It's easy to calculate because it's just a volume calc for each piston movement and then you cross reference back to how much travel & fluid displacement you get at the m/cyl. But most folks just do the "suck & see" method, especially if you're following a path someone else has travelled before.
The trouble is modern cars are just so good and we're used to light brake pedals which happen over a short travel. That's not always the case with cars from ye olden days.....
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