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91yesprit

Front Brake Upgrade

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You’ve changed the capilers and the pads though have you not?


Only here once

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I would be pleased to read any accounts of ongoing developments in this most informative thread! Ian, do you have more to tell since the swap of front components?

I have been reviewing aspects of my S2 upgrade project which is in an early stage at this time. On the matter of brake bells, or hats, it seems all and sundry are quite content to market pieces made from 6061, a readily machined and affordable alloy. The late, great Carroll Smith flatly dismissed 6061 for the purpose, declaring 2024 to be the sound choice for such an application. What have our group found in regard to choice of material for this? 

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On ‎29‎/‎07‎/‎2018 at 22:52, CHANGES said:

 My first upgrade was with the PNM  4 pots all round.  What I found was the spot brake for the hand brake was crap,  almost not capable of MOT standards.   I changed to the 4 pot rear with the full pad hydraulic hand brake , much better but not perfect.  The biggest problem i found was the brake squeal on the front when using decent pads like Mintex 1144 .. The braking was very good but the squeal unbearable , with lesser pads like green stuff the brakes were better than standard but in my opinion still lacking. but virtually no squeal.. After discussing in depth the problem with PNM then Hi Spec, I moved over to the 6 pot front with larger thicker disc.   To my surprise ' No change'  , squealed like hell , bloody amazing  braking but could not cope with the squeal , fitted green stuff , squeal only slight.   All this time I had no issue with squeal on the rears when fitted with M1144 .  However to give you an idea of the difference between the pads,  When M1144 fitted to rear and green stuff in the front , under medium to firm braking when you threw the clutch in to come down a gear, the rear wheels would lock and send you sideways ..  To initially compensate this I fitted a bias valve to balance out using M1144 on the rear and green stuff front.. this was better than green stuff all round..   As time passed the only thing i could think could be causing the issue was the mounting bell for the front discs. This was PNM 's own unit to facilitate the two piece disc on the SE front hub rear mount.  I questioned PNM on the possibilities that it induced harmonics due to its design.. The reply was no one else had complained. 

My only assumption was it was the pad type and the bell as a combination that caused the problem .. Over a period of time I asked those with the same conversion if they had similar issues.. Strangely enough only those who used pads like the M1144 had suffered squeal..   So what to do ..  Choice 1.   is to fit forward hub mounting bell , same as on the S4 onward.  Problem  here is the hubs are different and the concentric wheel mount gets used with the mounting bell. also the extra 8mm acts as a spacer which changes the front handling characteristics . So a pair of S4 front hubs would also be needed..  An added factor that does not effect me as i have changed wheel size , would be brake size restriction as you go more outboard with the smaller SE wheels..  Choice 2.  to fit a different design bell in same place, problem here is no one does them . PNM could not help and no other suppliers had anything close..  So on to the drawing board to design bespoke unit.. At this point it must be said that the large brake set up PNM supplied with the 10mm std mounting bell caused the disc to foul the steering arm , initially the arm had to be spaced to clear it.. I believe the set up now comes with an 8mm bell to correct this error.  However the track rod end is still bloody close to the disc to a point that the rubber gator failed from heat off the disc.. The new design will have to also address this point..      

The outcome was the new mounting bell with M1144 has virtually no squeal , just a bit on warm up as the green stuff did. the braking is amazing with no heat related issues..       all of the above only applies to those using SE type front hubs..  I hope my experiences help you with you choices.. 

original PNM set up 

IMG_20180308_175946960_HDR.thumb.jpg.caafdcd06a398c74f3134200066b1ab8.jpg

bespoke set up . 

IMG_20180308_180000421.thumb.jpg.2b2bdb8981cb6971b727d65db8f589dc.jpg

  

I have solved my squealing issue with a new bell just like yours. Thanks!

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5 hours ago, hspeck said:

I have solved my squealing issue with a new bell just like yours. Thanks!

Its nice to know that others are benefiting from this new option design.  Thank you for trying it and confirming my results..   

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I might be jumping on this bandwagon. I see PNM does a different kit to your original 'spider's web' bell, Dave. http://www.pnmparts.co.uk/esprit/esprit-s4-s4s-s300-gt3-93-99/esprit-s4-s4s-s300-gt3-93-99-j/lotus-upgrade-disc-kit-8938

A two-piece 320mm, as opposed to my original one-piece 323mm with all the holes around the periphery. I suspect it will accommodate the 6-piston Hi-Specs, but I'll be having a word with them in due course.

 


Margate Exotics.

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34 minutes ago, Chillidoggy said:

I might be jumping on this bandwagon. I see PNM does a different kit to your original 'spider's web' bell, Dave. http://www.pnmparts.co.uk/esprit/esprit-s4-s4s-s300-gt3-93-99/esprit-s4-s4s-s300-gt3-93-99-j/lotus-upgrade-disc-kit-8938

A two-piece 320mm, as opposed to my original one-piece 323mm with all the holes around the periphery. I suspect it will accommodate the 6-piston Hi-Specs, but I'll be having a word with them in due course.

 

I think you will find this is for the later S4 onward, with the mounting bell on the outside of the hub..   It has always been an option but needed front hub change to do correctly..   They will accommodate the 6 pot which is what i have on mine .. The only thing people have to look out for is the interference  on the wheel sizes they use.. .  Not an issue with 17 inch ..   

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9 minutes ago, CHANGES said:

I think you will find this is for the later S4 onward, with the mounting bell on the outside of the hub..   It has always been an option but needed front hub change to do correctly..   They will accommodate the 6 pot which is what i have on mine .. The only thing people have to look out for is the interference  on the wheel sizes they use.. .  Not an issue with 17 inch ..   

I've tried all kinds of pads, currently the car has the 'spaced-out' Brembo set-up fitted, and to be fair I think it's a good, cheapish, upgrade. Plan A is to revert to the Hi-Spec 6-piston set-up soon though, so may well give this new upgrade a go to see if it reduces the noise at all.

Well, that's Plan A, anyway.


Margate Exotics.

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On ‎15‎/‎03‎/‎2019 at 16:09, CHANGES said:

Its nice to know that others are benefiting from this new option design.  Thank you for trying it and confirming my results..   

yes! big thanks to you @CHANGES

sorry did not manage to get a better pic, but the one with holes is originally from PNM, and the 2nd is the one my machine shop fabricated..

although it does still have the occasional squeal, which is common for the mintex pads I'm using... the squeal is softer and not as high pitch 

BrakeBell01.jpg

BrakeBell02.jpg

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Finally fitted my new front solution. 

Alumium bell housing on 330mm vented and grooved disc with CL pads. Just got to bed them in now, hopefully a dedicated run tomorrow and then the trip to slough and back on Saturday will do the trick!! 

 

C9C0CBE1-2633-4A2B-B41D-47971E4BF1B7.jpegMy garage is starting to look like a holiday home for barely used brake discs 😂

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5 hours ago, chris said:

Finally fitted my new front solution. 

Looking good Chris .....  You may want to swap the discs around though , the outer point of the groove should be leading when they are straight .. 

 

163466380_APDiscs.thumb.jpg.afafadbaa9eaa6d6e75f6864ea00ec0b.jpg

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Cheers Dave, I thought that to and usually I would fit them with the groove forward however, these discs have curved vents and the manufacturer reckons both vanes and slots should angle rearwards for cooling and dust evacuation respectively. Done a bit of goggle-ing and couldn’t find anything definitive from the brake manufactures on slot direction as they seem to use both forward and rearward angles (most curved, some not) depending on application and company. 

Vane direction originally seemed counter intuitive to me, had to remind myself that they pump air from centre out and not ram air out to in (my excuse was that it had been a long day, the mrs said it didn’t matter as I was still special!! Starting to think that’s not meant in an endearing way🤔). Suppose we shall soon see if it makes any difference once I get it out on the road lol.

Main reasons for fitting these were:

• they are slightly bigger than the 325’s I was currently trialing.

• they are 20mm thick rather than 23-25 mm giving my aging calipers more room (suspected that one of calipers wasn’t adjusting up to disc properly due to being pushed right back in order to get it to fit).  Bought some spacers for the calipers but saw these discs and thought I’d give them a go.

• with an aluminium bell housing they are considerably lighter than the solid 325mm I had fitted.

• I needed to get the 325’s grooved to consistently work with the more aggressive CL pads but was trying to avoid that noise we have discussed previously from grooved discs (might not make any difference but as these disc’s come grooved from the manufacturer rather than retro machined, thought it might be worth a try).

 

 

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I am about ready to drill the mounting holes for the disk, just wondering how much run out in the radial direction is ok?  I have no cnc machine so the plan is to center the disk as good as possible (with an digital vernier) than clamp them together and drill the 6 holes from the back.  thanks, rick 

 

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56 minutes ago, chris said:

the manufacturer reckons both vanes and slots should angle rearwards for cooling and dust evacuation respectively.

If the manufacturer state that , then i would go with it..  We all tend to generalise  around what AP state, which in the case of other manufacturers may no be so..   I this case I would have fitted as you have, as i feel the vane direction for cooling would be more important than the groove..   It will be interesting to see your results , especially on the squealing front..  :thumbsup:

22 minutes ago, lotus-62 said:

I am about ready to drill the mounting holes for the disk, just wondering how much run out in the radial direction is ok?  I have no cnc machine so the plan is to center the disk as good as possible (with an digital vernier) than clamp them together and drill the 6 holes from the back.  thanks, rick 

 

Answer is very little ..   Any run out will give a vibration be it oh so slight..  Line up for drilling as accurate as possible , If using a 7mm bolt/drill , use a  7.2 or closest through the bell after to give a bit of wiggle room..  Fit everything to the car with the bell /disc bolts only nipped.  Set up a DTI  on outer edge of disc and rotate.  This will show you the run out.. with the bolts only nipped you will be able to tap the disc with copper hammer on the high spot and centralise more or less spot on.. when done tighten bolt to recommended torque and recheck..   This little bit of wiggle room in the bell holes will also help with alignment of any replacement disc's in the future..  hope that helps. 

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Dave, the big question is..... how much is very little LOL,  0,1mm? 0,05mm?  but a big thank you for the reply, back to the workshop for now. 

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2 hours ago, lotus-62 said:

Dave, the big question is..... how much is very little LOL,  0,1mm? 0,05mm?  but a big thank you for the reply, back to the workshop for now. 

I tend to go for 0.05 mm or better.. usually around 0.02 mm ... If the outer edge (the truing up face) is not dead smooth you can see variants which can be misleading..   In cases like that or older disc refit , I use 8 datum point to use .   

You may get away with 0.1mm or more, but i have never tried it so can  not comment..  But its fairly straight forward to do very accurate when you get the knack .. 

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I'm keen to understand all critical points in the use of 2 piece brake rotor assemblies. What is the material of choice for the brake bell? I.E. 6061, 7075, 2024 .

Cheers

 

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