Wilwood 16" kit caliper issues

[ailwyn]

OE single is a floating/sliding design and thus the piston has to travel more, as it is moving for both sides--while the pistons on each side of a fixed will move less distance than would that OE one.

Doug,

In theory this would point to an equals when it comes to fluid/pressure required to stop, but the evidence seems to be that the wilwoods push the BMC to the extremes of it's capabilities. I can only assume that the fluid capacity of the is that much greater, therefore more fluid needs to be forced into the system to pressurise it.

Don't get me wrong, I'm more than happy with the performance of the wilwoods, but not happy that I have to put my foot almost to the floor to get them to work.

Bob,

If you are planning on having a different BMC then presumably this is going to be a better performer than the stock... not sure I'm convinced about the lack of servo though... reminds me of some of my father's old cars, my leg has got quite lazy since then .... but I would assume that your replacement could be used with the wilwoods as a better match.

Ailwyn

[bobbrown]

[quote="Elanlover
I can state for a fact that the cars stops significantly faster than with the stock setup. [quote]

So you think you can not lock the wheels with the stock brakes. I know this is not true, you can get the stock system to perform the differance is it takes more effort (you have to press the pedal harder)
Plus it does not work well if pushed on a track or hard driving on the road
Remember its NOT the brakes that stop the car its the tyres the brakes only stop the tyres/wheels turning.
Any one that has done anything with cars on a race track will tell you that the backs are as important ans the front!
With the front bias these brakes give you could very easily come unstuck and have a nasty accident, the car must be very unstable pushed really hard.

I was not saying go for something the same as stock uping the caliper some 30% and and the upping the size of the disc will certaily improve things but conversly taking them too far will make matters worse.

I was not advocating changing the whole setup just the calipers them selves at around £210.00 $420.00 for the pair
so $200 for a BMC and $100 for pipes etc + tools + time you have to be past the $400 for this

Bob

[bobbrown]

I really not trying to stir the pot (and I'm no brake engineer), but since you all are getting technical on the pistons, remember that the OE single is a floating/sliding design and thus the piston has to travel more, as it is moving for both sides--while the pistons on each side of a fixed will move less distance than would that OE one.

I had taken the fact that the stock system is like a two piston system with both pistons on one side and the force transmitted across.
Hence the 3324sq mm area but there are aome losses in this type of system.

The main reason it has been adopted so widely is it is cheap and is very tollerant of misalignment etc

[Elanlover]

So you think you can not lock the wheels with the stock brakes. I know this is not true, you can get the stock system to perform the differance is it takes more effort (you have to press the pedal harder)

Uhmmm................pretty sure I didn't say that anywhere. What I did say was that the car stops a lot faster. That's about it. I haven't ever locked up the rears (or fronts) yest with the new setup. Have driven the car on the track a few times - pretty hard. Have yet to find the car unstable or any less stable than with the OE brakes. I don't think anyone else with larger calipers has either but that's for them to say not me.

I was not saying go for something the same as stock uping the caliper some 30% and and the upping the size of the disc will certaily improve things but conversly taking them too far will make matters worse.

Ok. I've no idea what you're thinking in terms of caliper size as it relates to what the OE or Wilwoods are and what the effect might be. I was only saying that new calipers with more pots but essentially the same braking force isn't for me. I wasn't implying that's what you were suggesting.

I was not advocating changing the whole setup just the calipers them selves at around £210.00 $420.00 for the pair
so $200 for a BMC and $100 for pipes etc + tools + time you have to be past the $400 for this

Well, if you're adding "my time" to the pipe manufacturing then do it too for the caliper install. Plus the custom mounting gear unless an exact fit can be found. That's got to equal $700 maybe? (I WISH the exchange rate was still 2:1 ). You do mention bigger rototrs above as well (and in you earlier posts) so I'm was just asuming that it'd be part of a package of calipers, rotors, hats and mounting gear - just like the Wilwood upgrade. If that' the case then its got to be close to the same cost. Thus my comment about it being way cheaper to replace the BMC and fabricate some new pipes. BUT , way harder. The BMC can be had for $150 - I was just rounding.

Anyway, I think what Brian did with the Wilwood upgrade was fabulous and I think anyone's who's installed it would agree. The ONLY nagging issue seems to be pedal travel thus my original comment (which has REALLY led this post all over) that any big brake upgrade should probably include a BMC upgrade - especially if the rears are done too (which I desperately want to replace).

[bobbrown]

ailwyn

Remember that a liquid does not compress so if the pedal is moving a long way then something else must also be moving.
If the caliper/pad was tight against the disc then only a very small movement of the pedal would be required to increase the preasure.

Also brakes operate in the 1000/2000 psi + we are not talking small pressures here,

[bobbrown]

Elanlover

My point as far as calipers was concerned is that the Wilwood 120-6806 os the same as the 120-6816 but with smaller pistons so it should be a straight swap no new discs no new hats no new brackets just the calipers

Also no more long pedal travel but still good brakes

If the experts (AP Racing) do not go for masive pistons on their brake upgrade for cars that are a lot heavier than the Elan and for competition use why should ther be any need for them to be that big

[Elanlover]

Elanlover

My point as far as calipers was concerned is that the Wilwood 120-6806 os the same as the 120-6816 but with smaller postons so it should be a straight swap no new discs no new hats no new brackets just the calipers

Also no more long pedal travel but still good brakes

If the experts (AP Racing) do not go for masive pistons on their brake upgrade for cars that are a lot heavier than the Elan and for competition use why should ther be any need for them to be that big

That's an interesting suggestion that perhaps Brian can look into. I've no idea if they'll suit the rotor size we have and Brian's custom mounting gear. Did you say they had dust seals (haven't read all the posts before replying)? Worth considering if it all fits.


EDIT: same caliper, difference piston bore = no dust seals but same mounting gear. Like the stopping power of the current setup though (bigger pistons). Just not the pedal travel. New BMC = no change in caliper which I'm ok with - just not all the work

[ailwyn]

Bob,

I've set and re-set the calipers, my mechanic has set and re-set the calipers, he's checked the discs, removed and re-fitted the discs, the system has been bled and bled and bled and bled. The brakes work really well, but my foot is practically on the floor to get them to work well, and there's a lot of travel before they bite. The fluid isn't leaking. There is no loss visible in the reservoir, the pedal isn't spongy.

I've changed the front brakes, I fitted refurbed calipers to the back, Changed the fluid. Everything should be working at it's optimum, except once the wilwoods went on the car the pedal travel increased significantly... I initially put this down to a coincidental demise of the bmc, so changed the bmc, exactly the same.

Remember that a liquid does not compress so if the pedal is moving a long way then something else must also be moving.

I don't think I suggested it did, but if the capacity of the caliper is that much more having the two chambers then for each mm or otherwise of movement a greater percentage of fluid being forced into the caliper is required, hence a given bmc will only be able to displace a finite amount of fluid, in this case not enough to move the caliper fully against the disc until the piston in the bmc is pushed further into the bore... remember a full swing on the brake pedal is only going to translate into an inch or so of movement in the bmc, so relatively small changes to the amount of fluid that needs to be moved in order to exert enough pressure on the caliper pistons can translate into quite a dramatic change on the brake pedal.

[RayD]

Ailwyn,

It might be worth exploring how much, and how quickly the pistons retract after braking.

Is it possible to get a shorter travel by repeatedly pumping the brake with the engine off?

Ray

[bobbrown]

ailwyn

my feeling is that these calipers are retracting further than they need too when the pressure is released and because they are so large it takes a lot of fluid to move them back in to contact with the disc.
IF my calculations are correct excluding the rear then the calipers will move 0.6mm (.024")for a movment of 10mm of the BMC which is not a lot
My possible solution would be to fit residual pressure valves in to the brake line between the BMC and the caliper (only on the front)
These only keep 2psi in the line after the pressure is released, it is the lowest cost starting point.
It is not that uncommon in race applications to see either residual pressure valves or springs with in the calipers.

Cost should only be £50.00

I do not think the changing of the master cylinder as a straight swap would be an option as it is fitted to the servo and it is required to be a specific mounting

Bob

[Elanlover]

Bob, my pads, when the brake pedal is at rest, are very close to the rotor. There is virtually no or very little play between the pad and rotor. I don't know what should be expected in this regard but I never got the impression that the pads are too far away from the rotor when the brakes are off. Could be wrong here though. As for a new BMC, finding a 1" bore unit that matches the mounting hole spacing and will simply "bolt on" is no issue at all. I already have several models picked out that will work. the only two issues are: 1) the port connections are different sizes requiring new brakes lines to be made and 2) is the booster up to snuff.

I haven't measured it (and the manuals don't specify this) but I'm guessing that the booster is a 7" model. If so, there's a possibility that it won't be able to supply enough boost to make the pedal feel as "soft" as the stock one does. By "soft" I mean you'll have to apply more presure to the pedal to get the same pressure at the calipers as the BMC bore is larger. This is a complete unknown right n ow but a number of threads in other forums where people have upgraded their BMC from 7/8" to 1" as part of a larger caliper upgrade seem to indicate this isn't a concern. So, I'm going on the assumption it shouldn't be that big a deal for us.

[bobbrown]

There is close and very close, but you have to take the position of the pistons in to account like if you had 0.01" between the pad and the disc and another 0.01" between the piston and the pad then you would have to take up 0.02" before the pad came into contact with the disc never mind taking up any flex there may be in the caliper
Note the loads exerted in the caliper are high with a 44.5mm pistoned caliper it is the region of 3 to 4 tons. yes that much. each piston can exert a force in excess of 1 ton, I'm not saying that is the force that is applied when the brakes are applied as it is progressive but the load required when the car is traveling at high speed is higher than at low speeds.
You have a lot of kinetic energy to stop!

The main problem with the BMC is not just where it bolts on but how it is connected to the servo.
I think it is similar to the picture, and the length of the push rod would be critical, I know this is not quite the same as the Elan but it gives you the idea.
You can not for example use a tandum BMC that is designed to connect to the brake pedal and with a ball end push rod, the one in the Elan is designed to be pushed in a straight line.
This I am fairly certain is a GM (Vauxhall) unit but I do not know of one that is 1" in their range. Most of the parts in the GM range cover a number of models, it may be that the Vectra is a good starting point as the V6 model had larger brakes (288m discs with a 55mm single pot caliper)

As for the servo it's self these are normally designed to increase the pressure at the master cylinder for a given input on the brake pedal.
If you look at the pedal ratio it is probably in the order of 3.5/4:1 where as a system with out a servo would be 6.2:1 but never less than 5.5:1
I think the servo would be fine on a 1" BMC it is just a case of trying to find one that will fit (also the space available is very limited on RHD cars)

There is another factor in brake upgrades that people seem to forget, if you increase the size of the disc then the amount of braking force that needs to be applied is less, so the same caliper will give better results on a 310mm diameter disc than on a 256mm disc

(“Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.” Archimedes, 220 BC)

In this instance a 44.5mm caliper and a 310mm disc for road use is over kill by some considerable margin and I feel the same caliper with 35.1mm pistons with give very similar results without the BMC issue
But it could also be a caliper issue
If it was me I would not spend any time, energy or effort trying to fix the issue with the BMC, I would just swap out the calipers and sell the old ones on Ebay
OR try the residual pressure valves, they can be fitted in the stainless brake hoses by simply cutting the hose and using two 1/8 NPT straight male fitting.

Bob

[F1 LOTUS]

Elanlover

My point as far as calipers was concerned is that the Wilwood 120-6806 os the same as the 120-6816 but with smaller postons so it should be a straight swap no new discs no new hats no new brackets just the calipers

Also no more long pedal travel but still good brakes

If the experts (AP Racing) do not go for masive pistons on their brake upgrade for cars that are a lot heavier than the Elan and for competition use why should ther be any need for them to be that big

The correct caliper part # is 120-6806. Please change Wiki
(I chose mine and Doug's piston size based on the AP kit)

Somewhere [don't know when] the part number got mis-quoted. I only became aware there may be an anomaly when someone was having an issue with ordering piston seals. Prior to this, installations received positive reviews with just a few reports of 'bleeding' / 'long pedal' problems? Due to the way information gets spread around it's difficult to know exactly how many people might have bought the '6816' caliper in error? Sorry

[ailwyn]

It's likely then as I got my part no's from (IIRC) the "Another run of..." thread it's likely that anyone on that run would have the same problems.

Brian, what are your thoughts on solving the long pedal problem... bin the calipers and fit the correct parts or is there merit in the large bore BMC theory?... frankly changing the calipers will cost me £400 - somewhere near £300 to get them inc delivery, plus I'll be paying my mechanic to do it... I can do without the hassle of doing it myself - if I've got to spend that much then I may as well go whole hog and get the off the shelf hi-specs with dust seals.

[bobbrown]

Not sure how you get to the cost you do, the calipers from Rally Design are only 89.50 + vat each that makes a total of £210.33 for the pair + delivery
It should not take any good mechanic more than a hour to change them so say + £50.00 labour + brake fluid

So total cost should be no more than £300.00

You could recover some of the cost by selling the calipers on Ebay

Bob

[Monty]

Elanlover

My point as far as calipers was concerned is that the Wilwood 120-6806 os the same as the 120-6816 but with smaller postons so it should be a straight swap no new discs no new hats no new brackets just the calipers

Also no more long pedal travel but still good brakes

If the experts (AP Racing) do not go for masive pistons on their brake upgrade for cars that are a lot heavier than the Elan and for competition use why should ther be any need for them to be that big

The correct caliper part # is 120-6806. Please change Wiki
(I chose mine and Doug's piston size based on the AP kit)

Somewhere [don't know when] the part number got mis-quoted. I only became aware there may be an anomaly when someone was having an issue with ordering piston seals. Prior to this, installations received positive reviews with just a few reports of 'bleeding' / 'long pedal' problems? Due to the way information gets spread around it's difficult to know exactly how many people might have bought the '6816' caliper in error? Sorry

Oh for sake

I`ve just checked the box the calipers came in and i`ve got 6816

Don`t understand this as i was on the original list and IIRC was the 1st to have them fitted in the UK, so can`t understand how i`ve got the wrong caliper

[Monty]

couldn`t find the original thread, but found the one Gareth started for the 2nd group buy of the 16" kit.
http://lotuselancentral.com/forum/viewtopic.php?t=6243


and Gareth listed the parts required so i would imagine everyone bought the 6816 caliper

what you get from brian are
2 'hats' which go on the hub to carry the discs
2 'brackets which hold the calipers
2 stainless steel braided brake hoses
$415 (cheaper if you live in the US IIRC)

for the 16" wheels what you need from from wilwood (or rally design if youre in the UK) is

2No 120-6816 Forged Billet Dynalite Calipers

1No 15Q-6824K Pads

2No 160-5844 Rotors

2No 230-0150 Bolt kit (8pk)

The rotors listed above are only the Plain disc ones but some peeps bought the drilled & grooved version but i don't know the part numbers.
comes to about £300

if you talk to me or someone else who has done this with the last lots of brians stuff then the following bolts should be bought too!!!

High tensile

4No Caliper to Bracket Bolts
Metric M10x1.5 thread x 30mm long
(with .06" thick washer)

4No Bracket to Hub Bolts
Metric M12x1.50mm thread x 35mm long

your total will be about £600-£675 depending on which pads and rotors you decide on..

hope this helps

cheers
Gareth

[tigerdog]

Just checked the bits in the garage for Smaug - Houdini also bought 6816.

Since they're unopened and unused, I wonder what the chances are of Wilwood exchanging them. I strongly suggest everyone use the search function for "120-6816" and change any posts you've made to show the correct part number. This will prevent confusion for those using the site as a reference in the future.

[F1 LOTUS]

Oh for sake

I've just checked the box the calipers came in and i've got 6816

Putting aside the numbers on the box...

Monty, possibly you've put the brakes through more punishment than most owners, doing several track days etc? I believe you've been very happy with the setup - perhaps your feedback prior to my post above could save many owners some heartburn?

[Doug]

My point as far as calipers was concerned is that the Wilwood 120-6806 is the same as the 120-6816 but with smaller pistons so it should be a straight swap no new discs no new hats no new brackets just the calipers

Also no more long pedal travel but still good brakes

interesting cause I was just about to post that my pedal travel was the same or better than stock with no long travel at all--I was going to say that some people must have old/leaky master cylinder bores--but it seems the part differences may account for my shorter pedal travel

I swear I posted the same number as Brian did in the past--that number rings bells loud and clear for me -- never seen the 120-6816 part number before??