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HiSpec Ultralite 4-pots - early views


Myles

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I replaced my std. front calipers with HiSpec Ultralite 4-pots (and grooved solid discs and 1144 pads) just before this w/e's Tour7 Haggis tour - many thanks to Frank for bleeding them one-step closer to working properly, by the way...

 

They've now done 1000ish miles - most of which have been m-ways, but also some hard Tour7 driving (admittedly mostly on wet roads...)

 

My initial thoughts are that they are taking a hell of a long time to bed in (I've nothing to base this on as I've never started with completely-new discs/pads and calipers... - it just feels that they should be working better by now).

 

I've also been experiencing rear-end bias - not sure if this is entirely due to the bed-in (rear discs are unchanged, rear pads were changed for bog-standard items a few weeks ago) - this was damned-scary, especially in the wet. It has improved a bit with useage, but I still think the rears will lock before the fronts.

 

Rears are std. Sierra - the only recent change was to fit flexi hoses at the same time as the front-upgrades.

 

THe pedal has also been quite spongey and requires a fairly-long push under hard braking - this is with the standard MC and high-ratio pedal (I think - I understand these were standard-fitment on Academy cars...)

 

I'm not unconvinced that the pedal gets spongier with heavy useage too - but this might be something to do with the bedding-in as well...(?)

 

The piston-area is not too-far different from the JW Alcons - and *these* are designed for the standard MC and rear brakes, AFAIK.

 

It has been suggested that as the rears are still receiving the same amount of fluid - but the fronts have a larger area - the rears will *not* be balanced and I'm not actually going to get to the point of really using the fronts without the rears locking up...

 

Sooo - so far, not so impressive. How long should I wait before investigating fitting any of the following:

 

i) Brake-bias valve

ii) Uprated MC (would also need the valve...)

iii) Pagids.

 

*confused*

 

Project Scope-Creep is live...

 

Alcester Racing 7's Equipe - 🙆🏻

 

Alcester-Racing-Sevens.com


 

Edited by - Myles on 23 May 2005 20:33:16

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but try fitting the CC big brake kit and uprated m/c and I don't think you'll complain

 

I dunno... I'd start with the cost and the weight.... *wink*

 

I think I'll probably take a bit more time to get them bedded-in - with luck, that's all that should be necessary. But if not....

 

Project Scope-Creep is live...

 

Alcester Racing 7's Equipe - 🙆🏻

 

Alcester-Racing-Sevens.com


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I think you may have something with the larger area if this is correct. My understanding of maintaining a decent pedal travel is not to go more than 10% bigger on total piston area a side.

 

It does sound as though you need a different M/C to be able to shift enough fluid to make the fronts work properly.

 

Bri

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It has been suggested that as the rears are still receiving the same amount of fluid - but the fronts have a larger area
I did some fag-packet calculations, comparing the total area of the Triumph 2-pots to the HiSpec 4-pots, and am pretty sure they came to more or less the same value, so the bias should be preserved.

 

Bite me 😬

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The only mod I've done to my brakes is the uprated master cylinder and some expensive pads (Pagid RS15), the master cylinder alone is worth a go even with std calipers taking out almost all of the sponge so would think it would do great things with 4 pots. Not sure how they compare to the mintex but RS15's certainly give a high degree of initial bite and all the confidence that goes with it fwiw *thumbup*
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Myles

 

I've fitted Hi-Spec 4 pots with solid 250 mm discs to my car but have yet to drive with them on. If thought a lot about the balance between the front and rear brakes. If there is a problem with the rears locking up I will put a limiting valve on the rear brake line. I think this is very sensible!

 

You may require a bit more brake pedal travel to operate the front calipers. By the time the fronts start to work the rears are locked.

 

I think a limiting valve is a good idea as you can tailor the brakes according to the conditions.

 

For example, the way to set up a race Mini is to jack up the rear and have somebody press hard on the brake pedal. Adjust the brake limiting valve so you can just turn the rear wheels by hand. If it rains switch the rears off altogether.

 

Also check that your hand brake has sufficient slack when off. Not sure, but this may have an effect on the rears if not properly set up.

 

Good luck. Hope you get it sorted.

 

AMMO

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We fitted some JW Alcon fronts a few weeks ago - yet to update the website with installation and initial thoughts etc, but so far I am very impressed. When we first fitted them I found the pedal travel to be a bit dissapointing - however, whilst playing around with the pedal box we found a slight leak in our brake master cylinder - it was seeping from the front where the push rod exits the cylinder - coming out from the rubber bellows.

Now this cylinder is at least 10 years and 82,000 miles old, and we have certainly never touched it, so I bought new one and fitted it - instant great pedal feel, and much reduced travel.

At the moment I have the greenstuff pads in the fronts, as supplied by JW - I'll use these to get a benchmark then try something else - always been pleased with the mintex stuff, maybe I'll stretch to padgids in the future, just to see what all the fuss is about.

 

Our set up is standard master cylinder, standard brake pedal (as far as I know) standard discs (new) - so far I am very pleased - heel n' toeing has become much easier and the pedal feels great.

(We also bled the brakes quite a few times, including after the first few hundred miles) - but maybe worth checking your master cylinder for any sign of wear Myles?

 

Big update!

here

80,000miles in 3 years plus

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Also check that your hand brake has sufficient slack when off. Not sure, but this may have an effect on the rears if not properly set up.


 

My handbrake really doesn't work anyway... I should have taken this opportunity to sort it, but didn't have time - it's a problem in the calipers, not adjustment (see threads passim

 

What's the rough cost difference between Hi-spec calipers, new discs, new pads, brake bias valve, uprated m/c compared with a straight swap Caterham brake kit at c.£650

 

Batsrad! It's (minus) the cost of the bias-valve basically - my setup was just under £500 delivered - so adding in an MC brings you to £650 (and a couple of extra kilos ;o) ) - however, the CC kit is £650 +theft etc. so I've still got the best part of £300 to 'fund' the MC/valve (if needed) before I start to look like a proper chump *wink*

 

Project Scope-Creep is live...

 

Alcester Racing 7's Equipe - 🙆🏻

 

Alcester-Racing-Sevens.com


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Interesting thread for me as I am still trying to get used to the Caterham spec 4 pot calipers. I was very surprised at the amount of pedal travel but was assured by Simon Lambert that matters would improve as the brakes bedded in.

 

Now I was none too convinced about this as I can't for the life of me see how the brakes bedding in will lessen the pedal travel *confused* and sure enough, although pedal feel has improved, the travel hasn't changed and is still too long IMO.

 

I originally thought, mistakenly as it turns out, that in speccing the big brakes I would automatically get the uprated master cylinder to go with them but Simon tells me that is a separate upgrade in it's own right.

 

Heel & toeing isn't easy with the pedal travel as it is and I really can't believe they are right with such a long pedal. Although they stop the car ok, confidence inspiring they are not.

 

So would I benefit from re-bleeding the brakes 🤔 When I built the car, I spent ages bleeding and re-bleeding until all the air appeared to be gone but I am wondering if and, indeed, how there is more air in the system.

 

 

 

Brent

 

2.3 DURATEC SV

R 417.39 😬

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I know DT aren't renowned for the keenest prices - but the (admittedly old) catalogue I have here shows them at £633+ theft - given that DT usually seem to charge just above everyone else to allow for a small discount, I'm surprised if the CC price *does* include theft - wheredya get the info?

 

If you add in the MC price to that which you quote, you get back to the £800 including theft that I was working on...

 

Project Scope-Creep is live...

 

Alcester Racing 7's Equipe - 🙆🏻

 

Alcester-Racing-Sevens.com


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Now I was none too convinced about this as I can't for the life of me see how the brakes bedding in will lessen the pedal travel

 

Nor me - the only thing I can think of is that this is a poor-description of what's actually happening - i.e. with new brakes, they are ineffective until bedded in - therefore you need to push harder and further to get anything out of them...

 

Project Scope-Creep is live...

 

Alcester Racing 7's Equipe - 🙆🏻

 

Alcester-Racing-Sevens.com


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It has been suggested that as the rears are still receiving the same amount of fluid - but the fronts have a larger area - the rears will *not* be balanced and I'm not actually going to get to the point of really using the fronts without the rears locking up...

 

This suggestion does not take into account the internal workings of a master cylinder. The only thing you need to give a damn about is cross-sectional area and pad material and shape. The fluid pressure in each circuit is controlled by the sizes of the primary and secondary pistons in the m/c. In the m/c used on Caterhams, these are the same size. Same size, same pressure. The job of the m/c is to keep those pressures the same.

 

Your problem lies elsewhere. Start by being completely obsessive about the brake bleeding - nothing will work right until you get this sorted.

 

FWIW, the brake balance should be least likely to lock up the rears in the wet and most likely in the dry. Maybe you have such a brake bleeding issue that the long pedal is resulting in the mechanical failsafe in the m/c coming into play (whereby front and rear pressures can be mismatched).

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I originally thought, mistakenly as it turns out, that in speccing the big brakes I would automatically get the uprated master cylinder to go with them but Simon tells me that is a separate upgrade in it's own right.


 

...but maybe not including the MC....

 

Project Scope-Creep is live...

 

Alcester Racing 7's Equipe - 🙆🏻

 

Alcester-Racing-Sevens.com


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When I fitted the JW Alcons I found the pedal feel disappointing. An upgrade to the bigger M/C (bought Chelspeed's old unit) improved things dramatically.

 

I may be completely wrong (probably) but if you fit harder pads on the front and leave the rears standard, won't the effect be that the rears will 'bite' first because the material is 'softer' but then fade as they get hotter, while the fronts will bite more slowly but be much less prone to fade? The overall effect on the road at least will be to have more braking from the back end.

 

Solution: either brake limiting valve or harder pads on the rear too.

 

Andy

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You could well be right there Myles, according to Simon Lambert the big brake upgrade has never included the MC unless specifically asked for.

 

Brent

 

2.3 DURATEC SV

R 417.39 😬

 

Edited by - BRENT CHISWICK on 24 May 2005 20:57:07

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