Wilwood 16" kit caliper issues

[John_W]

... the Wilwood 120-6806 os the same as the 120-6816 but with smaller postons ...

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. ...it's difficult to know exactly how many people might have bought the '6816' caliper in error? Sorry

OK, I have changed the reference number in the WikiLEC article to show 120-6806 and referenced F1Lotus's comments on this thread.

However I'm not happy the explanation is as simple as a typo in Geoff's 16" Wilwood upgrade write-up on the Wiki, and in Elanman Gareth's thread on a repeat 16" order. Before everybody with 16" kits panics, I think we need some info from ESM and Monty.

As Brian says, Monty has used the 6816 Wilwood kit hard on track and can provide empirical evidence. Since both the 16" Wilwood upgrade thread and the later 15" upgrade thread have disappeared from the LEC site without trace, there is no way of checking caliper specs that way. Therefore any contemporary information from F1Lotus or ESM is the best we can hope for. {edited to say I thought ESM put the original 16" UK kit together, however he did not, as corrected by F1 lotus below}.

I have saved much information on the 15" upgrade, since that is what I have, but nothing on the 16". However I think Monty is right that everybody with the 16" kit bought the 6816 caliper. The only piece of evidence I have for that is a question of mine to ESM in Sep 2005 about rear brake upgrades where I ask:

In the rear-brake discussion were you referring to the 16" brake upgrade as the one using dynalites (as you quote a 44.5mm pot, and are replying to a USA member who has 16" wheels)?

Now, this implies that ESM quoted a 44.5 mm pot for a front Wilwood caliper. The Wilwood caliper with that pot size is the 6816. This implies that the 6816 was the caliper used in the 16" upgrade kit from May 2005. The fact that all other surviving threads refer to 6816 and none refer to 6806 also points to the 6816 being specified.

If Brian or Alan can find any contemporary supporting information, that might settle things.

John

PS: for reference, the 15" kit uses four-pot Powerlite calipers (120-8729) which hav 35.1mm pots, however no dust seals (as there is no room behind a 15" wheel to fit a dust-sealed caliper like the Dynalite).
The 16" kit uses Dynalite calipers which do (I think) have dust seals. As shown in the Wilwood URL referenced, the only difference between the 6806 and the 6816 is the size of the pistons (6806 = 35.1mm; 6816 = 44.5mm); accepted disc widths are the same.
As the 16" kit also uses a larger diameter disc than the 15", even the smaller pot 6806's should provide greater braking force than the 15" kit.
I have the 15" kit and think the braking is very good; furthermore the pedal travel is small and rock-solid - no complaints.

[bobbrown]

All though this is highly relevant for those with Wilwood 120-6816 calipers this appears to have gone a little off the original topic.

As far as I am concerned having very large front brakes that have the effect of reducing the brake force to the rear is unacceptable and in my view down right dangerous.

If you work the figures out without the pressure proportioning valves in the equation then there is some real concern here
Assuming my calculations are correct

As standard the split is 64% front 36% rear,
With 1.38” 4 piston fronts this becomes 73% front and 27% rear
With 1.75” 4 piston fronts this becomes 81% front and 19% rear

If you add in the pressure proportioning valves then at 30Bar the figures become
Standard the split is 76% front 24% rear
With 1.38” 4 piston fronts this becomes 83% front and 17% rear
With 1.75” 4 piston fronts this becomes 88% front and 12%

And at 85bar
Standard the split is 83% front 17% rear
With 1.38” 4 piston fronts this becomes 89% front and 11% rear
With 1.75” 4 piston fronts this becomes 93% front and 7%

These calculations are by no means the whole story but they do give you some idea of just what changing the fronts do and as you can see the large bore (1.75”) fronts do bring in some figures that should cause concern.
Manufacturers no doubt spent hours of testing to get the balance right we come along and upgrade the fronts with out any concern for the rears

Bob

[John_W]

Bob,
Yup, your calculations and concerns mirror those of ESM on the original (lost) Wilwood front brake upgrade threads (15" & 16") and in the also lost rear brake upgrade thread I refer to above. ESM graphed up brake response front & rear for the different options.

I also agree that we're way off topic, but this new-found ambiguity in the front 16" brake upgrade is worth bottoming out if possible.

Can a moderator perhaps create a new "Wilwood 16" upgrade issues" thread by copying or transferring the relevant parts of this thread, then maybe this one can get back on track?

John

[ailwyn]

Can a moderator perhaps create a new "Wilwood 16" upgrade issues" thread by copying or transferring the relevant parts of this thread, then maybe this one can get back on track?

Done.

[ailwyn]

Brian,

I think that everyone that has the wilwoods will agree that the we are happy with the performance of the brakes... but it still leaves us with the issue of the long pedal.

Ailwyn

[F1 LOTUS]

Firstly - ESM was only involved with the 15" brake development.

Without getting bogged down with a witch-hunt, how can we resolve this?

Replacing the calipers is the simplest solution.

The most economic opportunity I can think of is to organize a group-buy of calipers here in the States - list price is approximately $135 each but I'd guess a discount could be negotiated? Freight - possibly some LEC members going to the 60th anniversary could hand-carry a pair or two??? Another possiblilty would be to talk with Rally Design in the UK to see if they have a sympathetic ear for our business a second time around?

[ailwyn]

Brian,

Nobody is interested in a witch-hunt... well I'm certainly not, it will achieve nothing.

What I do want to do is resolve the issue once and for all.

Blair,

Are you willing to organise a group buy on these calipers, or at least find out what sort of discount we can expect?

I guess for starters there's Monty, Me, you, tigerdog...

Thanks

Ailwyn

[Dico]

Group buy? Group buy? Count me in

[tigerdog]

I'm planning to call Wilwood on Monday. Fortunately for me (sorry guys) my Wilwoods have never been installed and I've located the original order number. I'm hoping if I drive to their doorstep and beg (Camarillo is about 130 miles from here) I may get them to exchange mine. I will also ask about a group buy. The current price list shows the 120-6806 caliper at $134.94 each. Shipping, import duty and dog biscuits will increase this.

[Monty]

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?

Brian,

No witch hunt here, just a bloody knife to cuts somebodys Nutz off lol Only kidding

To be truthfull i`ve not been completely happy with the Wilwoods although they are a big improvement on the stocksetup and are fine for normal driving.
But for trackdays they`ve been a bit off a pain as i`ve
1. get about 2" movement on the pedal
2. always suffered with the soft brake pedal
3. since there`s no dust seals, you can`t just swap pads easly as the calipers need a good clean each time and with me doing trackdays it`s a pain in the Ass as i`ve been through about 4/5set off pads.
4. I don`t exactly kill the brake on track anymore as on my 3rd trackday i warped the disc

Like i said for road use there great as you don`t need to change pads that often, so the soft pedal is down to the wrong piston size and with the correct calipers i`m sure most would be very happy with them

The brakes came up good on the brake test for the MOT
Here's the results

.....................N/S.........O/S
Rear................90..........90
Handbrake......160........160
Front..............330........360
Balance..........200........200


Can`t see me buying another set of wilwood calipers as i think i need to change to something with dust seals and thicker disc for the trackdays

[tigerdog]

Thanks for this feedback, Monty. I'll definitely postpone my own install until after I get the 6806s more due to the pedal travel issue than anything else.

[bobbrown]

Monty

I understand where your issues come from when on track and this is one of the areas I am working on to resolve, a Wilwood caliper with dust seals + a thicker disc.
Also I am working on a two master cylinder system (with bias bar) to allow the front to rear bias to be adjusted from the dash for track use and minus the servo.

As far as the MOT figures are concerned they are slightly ambiguous as the MOT only measures front and then back in terms of them working (e.g. how much it takes to stop the wheels turning) and if they are in balance side to side but not front to back.
I would expect to see a standard brakes with the same tyres on the same brake tester give exactly the same results.

Bob

[bobbrown]

Just as a note

Some figures with regard to master cylinder movement per 1/64" (0.015625") of pad movement (rears not taken into account as they are the same in all cases)
1.75" 4 pot 0.25"
1.38" 4 pot 0.155"
Standard 0.122"

If you assume pedal ratio between 3:1 and 4:1 then this multiplies up the movement

Bob

[F1 LOTUS]

Thanks for the understanding guys

Monty - I'd have to sew them back on first

Caliper deal - Possibly a call to one of the dealers will get a better price than Wilwood direct?

[tigerdog]

I spoke to Wilwood's sales department. Turns out they direct individual sales to distributors; if a group buy is to happen, it will likely be through Rally Design for our UK members. I'm on my own as far as sourcing my 6806 here in San Diego. I'm deeply grateful to everyone for finding this discrepacy before mine went on the car.

[Doug]

went back to my records and the LEC page I never published about the upgrade kit and found the correct part number . . .

Bore Size
1.75” 44.5 mm

Disc Width
.81” 20.6 mm

Part Number
120-6806

[ailwyn]

and the LEC page I never published....Part Number 120-6806

So really speaking, it's all Doug's fault Who's bringing the bolt cutters to Hethel?

[bobbrown]

went back to my records and the LEC page I never published about the upgrade kit and found the correct part number . . .

Bore Size
1.75” 44.5 mm

Disc Width
.81” 20.6 mm

Part Number
120-6806

so how come the bore size is stated as 1.75" part numbert 120-6806 should be bore size 1.38"

[John_W]

Doug,
I'm afraid that adds to the ambiguity. The Wilwood site shows the following sizing for Dynalite calipers:

Bore Size : Disc Width : Part Number
1.75"  44.5 mm : .81"  20.6 mm : 120-6816
1.38"  35.1 mm : .81"  20.6 mm : 120-6806
John

[theelanman]

well.......

Ive just read all that.......
not sure what happened there then.....
Ive got the caliper stated on the 'another run' thread......and when I posted that thread all I did was cut and paste from the old thread

I must say Ive not had any problems with mine......I can almost stand it on its nose and the rear does go a bit light but compared to the original set up I had that worked on telepathy I was much happier.....
at least I knew I was gonna stop with the wilwoods.......
I assumed the tail happiness was just a trait of having better front brakes...



dont know what to do