Jump to content
Click here if you are having website access problems ×

Jack Webb big brakes


timb2117

Recommended Posts

Just thought I'd share fitting of Jack Webb big brake kit to an imperial sv roadsport. I chose them after advice on the forum and Caterham were struggling at the time with Covid supply chain.

Supply was super fast and email response likewise from Jack - V helpful - only thing I needed extra was part number 77209f braided lines from caterham (wish I'd known at time as I would have ordered together.)

Took hub off and re greased bearings too took about 2 hours per side including a major clean up- one hassle was the copper sealing washer for caliper end was a touch big and off centre so didn't seal first time I bulked the thread up with a bit of PTFE tape so it centred perfectly and cinched up well.

Bleeding dead simple and pedal feel and power much nicer than the old 15 year old Girlings. I have retained the original master cylinder after reading the threads on here and it seems A1 and a quality bit of kit..... Now for the track acid test. 

brakes.JPG.da6bc4acf4cfd1e42731b8f07c7faa70.JPG

Link to comment
Share on other sites

I was advised that they were the same. Most impressive was the bolt on bolt off nature of them really an easy match up to the hubs and no difference in lining up (which is just as well because the steering rod end joint has barely 2mm clearance to disc!)

Link to comment
Share on other sites

Re #6:

I agree.  But it won't be needed when the OP removes the washer and relies on the adaptor for a seal.

ETA: Re-reading post #1, I think the OP used PTFE simply to centre the washer rather than apply it to the thread of the adaptor.  But it won't be needed anyway.

JV

Link to comment
Share on other sites

Yeah totally agree ptfe is ok for taps but that's it :)

Its only role was to get the pesky washer to line up centrally and stay that way as I tightened it up. I had already checked re the sealing with Jack as a an engineer this end queried the practice and validity, he works on v8 supercars and warned me that they get up to 700lbs of pressure - he cannot even press the brake pedal hard enough with both feet! 

 

Link to comment
Share on other sites

Re #9:

Apologies, I think I've got my fronts and rears mixed up.  Looking at my AP 4-pots, there is indeed a washer between the adaptor and caliper body.  I assume the Jack Webb calipers are the same.

But I'm still puzzled why the washer should be a slack fit over the adaptor.

JV 

 

Link to comment
Share on other sites

Usually there is an undercut of the thread to ensure the adapter mating surface is flat beyond where the thread ends, this means that the washer inner diameter is no smaller than the thread outer diameter, but the undercut diameter is less than the thread root diameter. This is why the washer can move around in the undercut, but normally it shouldn't move much off centre if it starts concentric to the adapter to begin with when tightening.

Link to comment
Share on other sites

What he said :) ha ha. Many thanks James that is exactly it, wish the washer were tighter but it isn't for that reason. The ptfe tape is essentially redundant in terms of sealing the washer doing all the work.

I would have been a  bit happier with a more substantial mating surface but am guessing thats the point its small therefore under high torque, hence does the job. Jack said it has been done for a long long time by Caterham like this so I suspect whilst we all have our own incarnations of this brake kit they all use the same principles/ washers.

thankyou all I appreciate the attention to detail.

Link to comment
Share on other sites

  • 5 weeks later...

Ok got a few road kms and one track day in, reliable but with the supplied ferodo's do squeal a bit coming to gentle stop, however good stopping power, but the rears are still doing more work.

I am going to pop in a valve to the brake line to rear, just as it goes into the tunnel under the bonnet then I can tune out the backs a bit- I am not super feeling on the set up so will fit/ test then forget, without the need to fettle in cab, mid track session. 

Link to comment
Share on other sites

  • Area Representative

"but the rears are still doing more work"

 timb2117,

What makes you say that?

As Simon says, I'd be very surprised if you need LESS rear braking after fitting big fronts!

What pads do you have front and rear? Additionally, what type and size tyres are you running.

Link to comment
Share on other sites

Hi Richard I know it sounds odd but -The rears prior to (and after) fitting of the bigger fronts easily and by far heat up more than the fronts, also under aggressive "test" braking the rear locks up sooner.

Sorry not sure about the rear pads but standard caliper, tyres toyo proxxes r888 and wheel size 205/45 r16. - I realise they're big but came on the car and I can get enough heat into the nearly new soft tyres on track for them to work well.

Front pads are the ferodo "race"that came with the brake set up.....Any thoughts

Link to comment
Share on other sites

When I fitted big brakes many years ago and changed to Mintex 1144 pads all round, I found that the rears locked up even more than with standard fronts. I deduced that the weight transfer to the front was unloading the rears and causing this.

Link to comment
Share on other sites

Looking at it simplistically, and ready to be corrected, if you significantly improve the front you’ll increase the rate of weight transfer and provoke rear locking by taking the weight off the rear. Improving the rear in proportion will maintain the rate of transfer and balance and keep things in order? 

 

Link to comment
Share on other sites

  • Area Representative

 

"Front pads are the ferodo "race"that came with the brake set up.....Any thoughts"

It would be helpful to understand exactly what front pads you are running. Both DS2500 and particularly DS3000s require some heat in them to work effectively (with DS3000's working best when the discs are glowing red hot!)

If you have a standard pad in the rear, but a competition based pad in the front, you may well have brakes that work from cold in the back, but not the front. If its a track only car, and you know that, then that's not a problem, where as you build heat, the balance will improve, but, for a road car, that is not very safe....

You comment that the rear brakes get hot. That is not unusual, and, in itself, not as much a problem as a characteristic. Quite a lot of the available stopping power of our cars actually comes from the rear brakes, but, on standard cars, the discs are solid and cooling is poor. By increasing the disc and pad size, and adding vented discs that dissipate the head better, you exaggerate the temperature imbalance between front and rear.

In an ideal world, the brake sizes would be specified so that heat built up and was dissipated at the same rate on both axles. However, there is not "one size fits all" solution to suit all 7's. Overall weight, weight distribution, along with tyre sizes and and compounds all affect that "ideal". ECR's car have a heavy Vauxhall XE in the front, where the 'Busa car that I've driven this year has a vastly different dynamic......

I'd really want to fully understand exactly what you have before making any other change.

For optimum braking performance, front to rear balance is paramount. To that end, I've been running a modified pedal box with dual master cylinders and a bias bar to enable adjustable front/rear balance for the last ten years.

 

 

 

 

 

 

Link to comment
Share on other sites

  • Area Representative

Oops.

It's just been pointed out to me that my opening statement in the above post did not make sense,....

I've just edited it to correct it.

If you look at the chart below, you see that DS3000s have close double the stopping power at 500°C that they do when stone cold (note that the chart starts at 150°C, but road cars will often be braking from stone cold).

Additionally, DS3000s are at their optimum between 500 and 700°C (that is in the range where the discs are glowing red hot)

In contrast, a typical standard pad will work at its best from cold, typically getting worse the hotter they get.

So, if you have different pads front and rear, whatever front/rear balance you cold is unlikely to be what you have warm, and different again when hot. 

https://www.ferodoracing.com/products/car-racing/racing-brake-pads/ds3000/

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...