Wilwood 16" kit caliper issues

[Elanlover]

I have a few concerns about swapping out the Wilwood calipers.

1. No dust seals (as Monty suggested). Good calipers for sure but, if I was going to buy new ones I'd be interested in looking into new calipers with dust seals. (subsequent questions to this would include: would this mean new mounting hardware and could a slighty thicker rotor be sourced?)

2. I really want to do something about the rear calipers one day too. Just going to Dormans isn't good enough for me. I'd like a rear caliper that's a match with to the front upgrades. So, if that were ever to be possible I'm betting that the BMC would not be big enough to handle new front and back calipers even if we used a smaller pot front caliper.

There's been a LOT of work done on upgrading the front brakes and I'm not unhappy with what I've bought. I would like to imporove it if i could. But, here's the "possible" problem I see here.

The original upgrade was a reasonably big step that created some problems with pedal travel (for some). "Downsizing" the calipers may help but the same problem might come back to haunt us if one day Brian (or someone else) creates a better rear brake upgrade. If we take little steps towards a better overall brake system we are always going to find something to be unhappy about along the way unless we look at the whole system. That means calipers, rotors and BMC (and possibly proportioning valves).

So, is it worth taking the time now to look at the possibility of upgrading the whole system? I could certainly live with the current setup fo a bit longer if I knew that a better, more complete soluiton was on the way.

I almost shudder to throw out this idea only because it means I'm basically suggesting that someone else give up their time to look into this. I don't have a lot of knowledge or experience here and can help where I can (likely very little) but it lilely to be someone else's precious time I'm suggesitng get's consumed

Thoughts? (or curses )

[F1 LOTUS]

It would be nice to upgrade to something with dust seals, but this appears to add width in the caliper design which almost certainly leads to non-standard wheel offset...

[Doug]

Blair, you're worrying about something that you shouldn't need to worry about.
-get the proper caliper and you shouldn't have a pedal travel issue
-keep the car and brakes cleaned periodically (as I'm sure you do) and you won't have to worry about dust cake build-up
-you won't ever need a rear brake upgrade

[Nige]

I still have Hi-Spec Billet 4 calipers Red stuff pads with a 300x28mm disc on the front and standard calipers with green stuff pads and grooved and spotted discs on the rear. I'm using silkolene pro race fluid. I don't know the detailed specs of the Hi-Spec calipers without research but provided the system is fully and properly bled and the fluid changed regularly (I do it annually) I have a pretty solid pedal once the initial travel of no more than half inch has been taken up (this is the same as it was with a standard setup). I only ever intentionally practice extreme braking on the track and the weight transfer forward when I do is significant and the car does go light and a little 'squirrely' at the rear but it is perfectly controlable, particularly when you are expecting it. Without any intention of scoring points or bragging on the occasions when I've been on the track with other Elans I've found I've been able to out brake both Wilwood and modified stock set ups and track day etiquette and rules have prevented me from passing. I do however also accept that the R888 track day tyres I'm using also give me a brakeing advantage. The downside is I've had to compromise on the offset in order to clear the calipers, with S2 wheels I use a 5mm spacer on the front only giving me an offset of 55mm and my track wheels are a 17" with a 48 mm offset all round.

The point I'm making (and I defer to those who can do the maths) is that a front upgrade does not necessarily upset the braking balance of the car to the point of making it unsafe. Without wanting to misquote ESM he did an analysis of my set up (based on a similar summary to that above) and concluded that the additional friction from the grippier rear pads compensated to some degree for the increased braking performance at the front. Less dive on the front under braking would also reduce the weight transfer and thus leave the rears better able to do their job.

[GeoffSmith]

Nige, the issue is the diameter of the pistons. I believe that ESM, Brian and Bob have all calculated the optimum Wilwood piston caliper to be 120-6806 with a diameter 35.1mm but somewhere along the line it's become 120-6816 which has a diameter of 44.5mm. Although this is only a ~26% increase in diameter, it is a 60% increase in area and this puts far to much emphasis on the fronts.

A week or so ago I had to brake heavily on a bend for a cow stood in the middle of the road and I was quite alarmed at how the rear end began to snap out of line, even though I wasn't going particularly fast. For the majority of the time on the road and even on trackdays, heavy braking is likely to be in a straight line, so a bit of rear end drift is unlikely to be a problem. My worry is what would happen in a high speed emergency if someone was braking hard and taking avoiding action as the back end is unlikely to hold the high lateral g forces. Thinking about it, didn't Monty have a 180° flip in Pinky I?

Bob and Brian both concur that the 120-6816 calipers are wrong, so I have new calipers on order.

[Doug]

A week or so ago I had to brake heavily on a bend for a cow stood in the middle of the road and I was quite alarmed at how the rear end began to snap out of line, even though I wasn't going particularly fast. For the majority of the time on the road and even on trackdays, heavy braking is likely to be in a straight line, so a bit of rear end drift is unlikely to be a problem. My worry is what would happen in a high speed emergency if someone was braking hard and taking avoiding action as the back end is unlikely to hold the high lateral g forces. Thinking about it, didn't Monty have a 180° flip in Pinky I?

to overanalyze, I remember ESM's brilliant explanation of braking and friction, etc. The point was you can only improve braking so much. It's likely that any problem would not be from "too much" front braking. Maybe it is due to the car's front weight bias? too little rear braking is not going to make the rear end wander or come loose, is it!??

my conclusion = it was the cow's fault

[algirdas]

Dear All:

I realize that I am late in coming to this party, so please forgive me if I plow territory that has already been plowed.

First, if my recollection is correct, one of the American car magazines did a road test on the Elan when it was first introduced to the American market or shortly thereafter and they commented that the car had spun while braking in a turn. They made it sound like it was some freak occurrence. What is the value of this historical nugget? I don't know, but I figure I better mention it in case there is another demon at work here.

Second, emergency braking is a big deal. I live in a fence-out jurisdiction which means you fence out animals where you don't want them to go. Just last Sunday, my wife and I came around a bend in the mountains just west of town and there were three bovine bad boys having lunch on the shoulder of the road. All one of them needed to do was decide to have desert on the other side of the road and LEC would have been sans yours truly and my better half. Geoff's rectum clenching moment must be taken seriously.

Third, I spoke with Wilwood yesterday and explained our situation. Off the bat, they are willing to knock $10USD of each caliper (as in 6806s) if we buy directly from them. I think we can work the discount some depending on the numbers.

Fourth, I agree with Blair about taking a global look at our braking systems. As laudable such an effort may be, and we are blessed to have a full compliment of true brainiacs, it is going to take time. Its going to re-kindle the whole rear brake debate. And perhaps better systems are out there. Perhaps not. But in the meantime, I'm probably going to drop $250 on a pair of 6806s if for no better reason than insurance. Wouldn't you know it? I just got the last of the air out of my brake lines! Bummer.

Fifth, if for no reason other than curiosity, I'd like to know the details of Marie's Brembo setup. My understanding is that it is even more "rad" than 6816s. I haven't heard her complain about her ass end passing her under hard braking (cue the locker room banter).

Sincerely,

Algirdas

[bobbrown]

Fifth, if for no reason other than curiosity, I'd like to know the details of Marie's Brembo setup. My understanding is that it is even more "rad" than 6816s. I haven't heard her complain about her ass end passing her under hard braking (cue the locker room banter).

The common Brembo caliper size seems to be something like a 38mm and a 34mm piston (two of each) so that gives a piston area of 4048sq mm.
Standard is 3324sq mm
Wilwood 6816's 6221sq mm

[Paul.P]

Bob and Brian both concur that the 120-6816 calipers are wrong, so I have new calipers on order.

Geoff, where from, Rally Design ?, & how much ?, am i right in presuming the new calipers use the same pads ?.

[a5gcd]

Count me in for a group buy

[GeoffSmith]

Before everyone from the first batch goes diving in, it would be worth checking to see which calipers you have. After the great site meltdown a few years ago, the original thread has gone, but it looks like at least John_W managed to get the right ones. The only current record of either number is the incorrect one on the second group buy thread so it could have happened any time in between.

I believe the calipers are outwardly identical and will take the same pads.

[theelanman]

just a quick one.....anyone know where the serial number is stamped???....I ditched my boxes ages ago

cheers
G

[nitroman]

just a quick one.....anyone know where the serial number is stamped???....

They are not stamped into the metal casting. The entire part# starting with 120- (in both cases) is stamped in paint on the body of the caliper; but, if you had your calipers painted or powder-coated that is now covered up!

I believe the calipers are outwardly identical and will take the same pads.

Da.

Algirdas, count me in for the group buy.
Thanks, Matt

[theelanman]

thanks for that......
I had a better thought just after Id posted.....
'go and look at the invoice'......

DOH!!!!!!

invoice reads 2No....120-6816

DOH!!!!!!!

better have a chat with Rally Design

[nitroman]

Just one other bit of tid: Anyone/everyone with the 16" Wilwood kit astern of Brian & Doug has the 120-6816 (i.e., larger) caliper. The only caveat would be fluid dynamic/mechanical engineers or professional race car drivers who did their own calculations & bought differently.

My basic thought on the matter is that shite happens, and certainly more serious shite than this. For me this has not manifested itself as a safety issue, and you even get used to the longer pedal travel. If you go back to basic physics you can easily argue that it requires less pedal effort and therefore gives more tactile feel (it's like bone/muscle relationships in the body... the "fulcrum/lever" effect). For instance, take a hydraulic car jack. It gives a person the strength to lift a car, but the car only moves a small distance relative to each downward stroke of the jack handle. However, think how RELATIVELY little muscle effort is required VS lifting your car "weightlifter" fashion. By not having to recruit both a higher proportion of motor units and larger & larger muscle fibers in your quadriceps & tibialis muscles you gain more precise control of your brake pedal. This explains how the same hand that picks up a feather can also bitch-slap someone!

[theelanman]

thats all good....I think the point was about the balance rather than the ability to stop......
its all about braking hard whilst turning the wheel....should you need to...

mine have been on for 2 years and theyve been great...real good stopping power....bit twitchy now and again but I now know where that twitchy point is.........

oh I dunno......


twist or stick??????

[paulrwebster]

I have the 6816 callipers. Normal weather conditions they are fine, however in heavy rain on the motorway the car is extremely twitchy under braking and I have to be very careful how I drive and brake.

[DeeAitch]

For road use I'm with Doug on this one

you won't ever need a rear brake upgrade

For me, if you improve the front performance you will get increased weight transfer, which effectively means you would need less rear brake effort to avoid them locking up under severe conditions, pretty much the same effect you get if you lift off in a bend on the limit of rear adhesion - lift off oversteer
If you are set on improving the rears then remember they are only using something like 15% of their full capability and that is capped due to the nature of the pressure limiting valves - ESM did explain this very well when he developed the original 15" Willwood kits with Brian IIRC.
I'm sure someone on here - Dave M with AP's ? - has replaced these valves with adjustable ones so he could tweek the balance - for track use only. Would be interesting to hear what he thinks of this.

Anyway, whats wrong with sliding calipers

[bobbrown]

I feel a lot of you are missing the point, the amount of braking that can be achieved on the front is no different on the standard brakes as it is on an upgrade it just takes more effort (pedal input) to achieve.
The amount of weight transfered during braking is down to the tyres you have fitted not the brakes.
It is the tyres that stop the car!!!!!!!!!!!!!!!!!!!!!!

With out the back brakes operating correctly then the cars stopping distance will go up, this is a fact not just a theory more so in the wet.

On a dry road you will get more weight transfer than on a wet road due to the extra grip from the tyres, note the tyres not the brakes.
The car would have been engineered to give good brake ballance in wet and dry conditions so this is always a compromise.
That is also why race and rally cars have adjustable brake bias to "dial in" the brakes for track/ stage conditions.

Bob

[RayD]

...In the past I've used tyre width to exaggerate the point. If you fitted the car with cycle tyres any system would lock the wheels up, whereas if the tyres were 18” wide the car would stop at the same time as the wheels, generally speaking.

Rear brakes have a tendency to pull the back of the car down, you will have noticed while applying the handbrake on the move.

All other things being equal, the pedal travel on all 44mm callipers will be the same. My standard calliper pedal moves 1½”. If I calculated it properly the 44mm pedal moves 2¾” out of an available 4”

The thing I find strange is how Élan brakes seem to perform less well than the cars they took the brakes from

Ray