Thinking of installing the PNM Parts Big front brakes

[bxs]

I have the '91 turbocharged Lotus Elan M100 with ~14,000 original miles with the original stock exhaust replaced with a Piper 2.25-inch straight pipe with single rear muffler (It's CATless).

I'm wanting to improve the Elan's braking performance, and with this in mind have been exploring replacing the stock front brakes with the FRONT BIG BRAKE KIT - PNM Parts pre-order ELAN M100 283mm (16" +) front 4 piston brake kit. The PNM website lists these for £624.95 currently.

For anyone here who has replaced their stock fronts with these PNM Parts 'Big' brakes I'd like to get some feedback on how much better they are compared to the stock front brakes. For example, let's say the stock fronts will completely consume all of the kinetic energy of the Elan traveling at 60 mph in 150 feet. After installing the BIG BRAKE KIT with the Elan traveling at 60 mph, how many feet would the Elan travel before stopping.

Thanks.

[Tuga2112]

i dont think you will find any scientific data like that.

everyone who has upgraded is super happy with the upgrade.

i dont have the upgrade and can lock both front wheels when braking. it is scientifically impossible to brake harder than that. as when you reach that point. its not the calipers your bottleneck. its the tires.


i also know the type of force needed to make the front wheels lock. and i suspect the amount of pressure on the pedal is where the difference lies. (potentially giving you better control, which is just as important)

i would strongly advise you to buy the upgrade, because despite the fact "matematically" it cannot be better than the (well maintained) stock brakes . its very obvious from all the reports of all the owners that have it. they are very happy with it and recommend it.

[MPx]

Yep - I agree with Joao...but from the standpoint of someone who has had an upgrade. I didn't get mine from PNM but my kit was also based on the HiSpec disc/caliper just the same as Pete Musgrove's. The original brakes never inspired confidence for me - mostly fast road but occasional track use. The HiSpecs do - positive bite and nicely progressive with no fade on track albeit during no more than 20 min sessions. I also uprated the rears (originally HiSpecs own, now with the PNM kit) and that works well, but important not to go to far with that as there's very little weight in the back and locking the back end first is recipe for disaster! (Yes proven )

[bxs]

@Tuga2112 and @MPx thanks for such a quick response to my enquiry about the BIG BRAKE KIT from PNM.

I'm coming from the aspect that my stock front brakes do a reasonable job today, but do hesitate when on the road that they need more stopping performance to give me greater confidence they will stop the car when needed.

At this time knowing the braking system design dates back to the late '80s into the early '90s they do show their age with respect to quickly stopping the Elan in precarious traffic conditions that require sudden unexpected stops. Yea, the current stock brakes do stop the car reasonably well, require greater brake pedal effort compared to a modern car's brake design, and they do show their age and lack of performance. I personally require more confidence I can stop the car when needed.

The current braking performance for my Elan is such that I take great care when driving keeping my distance from cars in front of me and maintain safe speeds at all times. It's the sudden situations that require quick braking that bothers me.

I sent my posted enquiry here to PNM, and I received a response which I share below....

"Hi,

I don't have any figures but I can tell you from driving these cars that the difference is huge in performance and feel. Personally, I wouldn't drive one far without a front kit, the original brakes are very poor. I have had a customer from the USA who was contemplating one of these kits for two years. He did later contact us to say he wished he'd bought the kit as he was involved in a collision where his brakes were utterly inadequate. Fortunately, he did manage to fix the damage to his car and fit the kit. He just wished he'd bought it earlier. With modern car brakes being so efficient, the brakes on these older models are just not up the job. These calipers are so much more efficient and combined with the larger discs, they just give you more confidence in normal driving as well as fast road driving and emergency situations.

But I would recommend having a look on somewhere like www.lotuselancentral forum and seeing what other people who have the kit say. I can only say I've sold hundreds of kits and the feedback I have had is universally positive.

Many Thanks
PNM Parts"

[Tuga2112]

i am disappointed with PMN refering to an unfortunate scenario like that in the reply.

there is a fine line between marketing and scaremongering. this is too close to that line in my opinion.

i have full confidence in the quality of the parts they sell and customer service. but as far as actual experience driving and working on these, I have my doubts...

1 direct interaction with them. and one "footnote"
my rear springs were purchased from them.. the website says "OEM replacement" but they sent me some that work for the different shocks they sell.. their "resistance" to admiting they messed up and demanding pictures to prove they sent me springs that didnt fit the car was not appreciated. i understand they have no reason to assume i am competent at doing work on the car. but the way the messages was worded could have been nicer.
however as soon as they got the pictures they arranged for the swap ASAP... that doesnt stop the fact the car was another week off the road as a result.

the second case is related to my NA
it had the timing belt changed by them (a invoice included in the sale is proof) however around 2 years after that date (about 6 months after purchase) i started investigating the "running rich" issue with the car and found out the timing couldn’t be adjusted to be within the manual's range.
I eventually pinpointed the issue to the fact the exhaust cam was 1 tooth out of alignment... the work was done prior to my ownership. to i have no actual right to complain, but for a £1400 a total in the invoice the previous owner had paid them. I would have been fuming.

i never called them about it. 2 reasons..
1 - it wasnt my car when they did the work.
2 - the investigative process was already done and by the time you can see the problem. the belt was ready to be adjusted.. nothing they could do about it

with all that said.

I would not say this experiences are enough evidence to advise against using their services, at the end of the day i have no reason to believe them to be dishonest or unfair (unlike a different established lotus specialist) and mistakes are bound to happen when you operate for whatever long they have (more than 12 years at least). I believe near Manchester they will be the best you can get.... while at the same time I am convinced i can do a better job by myself

[rip]

i dont think you will find any scientific data like that.

everyone who has upgraded is super happy with the upgrade.

i dont have the upgrade and can lock both front wheels when braking. it is scientifically impossible to brake harder than that. as when you reach that point. its not the calipers your bottleneck. its the tires.

Wrong. It is not that simple.
Locking brakes is skidding, which is not an effective way of stopping the car. (F1 cars go wide when they lock up). A tyre grips the road a lot better when it is revolving, so the ideal braking force is just a little short of locking the wheel. This is MUCH easier to feel & control with less pressure, just like when something is stuck it suddenly gives when released & you end up slipping, but you can control it if you have more leverage.
Friction brakes turn kinetic energy into heat. They then have to dissipate this heat. This last part can be improved massively with a brake upgrade, which makes them less susceptible to brake fade on a long downhill or a track session.

If you still doubt me, you are welcome to try my Elan sometime (Castle Combe next year?). Mine has the Vectra/Subaru combination. You will be surprised at how much better the feel is & how much more confidence it gives you.

[Tuga2112]

Wrong. It is not that simple.
Locking brakes is skidding, which is not an effective way of stopping the car. (F1 cars go wide when they lock up). A tyre grips the road a lot better when it is revolving, so the ideal braking force is just a little short of locking the wheel. This is MUCH easier to feel & control with less pressure, just like when something is stuck it suddenly gives when released & you end up slipping, but you can control it if you have more leverage.
Friction brakes turn kinetic energy into heat. They then have to dissipate this heat. This last part can be improved massively with a brake upgrade, which makes them less susceptible to brake fade on a long downhill or a track session.

If you still doubt me, you are welcome to try my Elan sometime (Castle Combe next year?). Mine has the Vectra/Subaru combination. You will be surprised at how much better the feel is & how much more confidence it gives you.

just for the sake of digging my hells in.

if you can lock the wheels with the standard calipers. the rest is a skill issue

but as i said in my first reply.

i suspect the amount of pressure on the pedal is where the difference lies. (potentially giving you better control, which is just as important)

and yes would like to take up the oportunity of trying the upgrade, i suspect it will be the most expensive experience of the year. because if its as good as everyone says, its a bill i am not looking forward to.
PS.
i just read my reply and realised when reading it may not be clear.
i agree with you generally, the reply is a mixture of jest and personal opinion.

[dapinky]

Just to throw in my (unasked for) 2p worth.....

Locked wheels WILL give the shortest stopping distance - on an unbroken dry road. That is where there is the maximum coefficient of friction between the tyre and the tarmac/concrete.

However, due to some old bloke called Isaac (lets blame him for this!), it is also the conditions where you have the least ability to exercise control of the direction of travel (Newtons 1st law of motion).

BUT, as soon as that inertia overcomes the friction (wet road, or loose surface) then you will get reduced friction and braking by having the wheels locked.

So, for all intents and purposes, a car which is exactly at the point of locking the wheels will give very nearly the shortest overall stopping distance for any given friction coefficient, and the fact that the wheel still rotates means that you can still apply some directional control with steering inputs.

Modern cars use ABS to keep the car at a point just below wheel- lock..... whilst us old gits still remember Cadence Braking.

When all is said and done, it is a matter of what you are happy, comfortable and confident with. I have Hi-Specs on Angies car, and I have OE callipers on mine - mine will stop in a shorter distance due solely to the tyres being 'stickier' - but it is marginal. I can lock my wheels if I push hard enough, but with the narrower bore master cylinder it is easy to regulate the braking to just below that point.

[cellaway]

I put PNM’s on the front, Bob Browns on the back. I changed the master cylinder, cleaned the proportioning valves. Replaced all the flexible pipes. I’ve got 16” wheels. The car stops OK but probably not as well as the Qashqai but at least I don’t have to book up in advance to stop. Maybe a more efficient servo would help If there is one.

[peter canepa]

Welcome to the site, glad to see another Fed version being restored. How can anybody compare this car to a Mazda Miata? Anyway, I was thinking about ordering the same thing from PNM See my post Wed 27.10.2021 Cheapest way to fix the brakes. It was not enough vacuum. Brakes are fine, my car does not have the chip. I just like the look of a real proper upgrade. If you can afford it, or like I just did scroll though 100 pages of brake upgrades, and still can make up your mind.

[Tuga2112]

or like I just did scroll though 100 pages of brake upgrades, and still can make up your mind.

and thats exactly why im still running the factory calipers...

interestingly enough. just last night i had to use the brakes properly (without time to plan) and after clearing the situation without any problems... apart from brown undies.. there was smell of rubber. and the low fuild light came on... i need to top up the reservoir i guess.

[dapinky]

.. there was smell of rubber. and the low fuild light came on... i need to top up the reservoir i guess.

Joao, whilst the low fluid level could well be just fluid sloshing around in the reservoir and it needs topping up, I would suggest looking at it quite soon..... it may be that a very sudden and hard shove on the pedal could have caused a pipe/hose/joint to fail somewhere on the car leading to fluid loss...... at least do a visual check of the level, top it up and look for any suspicious puddles under the car.

[Tuga2112]

.. there was smell of rubber. and the low fuild light came on... i need to top up the reservoir i guess.

Joao, whilst the low fluid level could well be just fluid sloshing around in the reservoir and it needs topping up, I would suggest looking at it quite soon..... it may be that a very sudden and hard shove on the pedal could have caused a pipe/hose/joint to fail somewhere on the car leading to fluid loss...... at least do a visual check of the level, top it up and look for any suspicious puddles under the car.

thanks Dave.

just to note, the light did come on and gone off straight after.

i will do a visual check anyway both for that as well for any potential small leaks. i suspect i have a tiny leak somwhere as i now had to top up the fluid twice since the last time i done work on the brakes.

[dapinky]

just to note, the light did come on and gone off straight after.

i will do a visual check anyway both for that as well for any potential small leaks. i suspect i have a tiny leak somwhere as i now had to top up the fluid twice since the last time i done work on the brakes.

Ah, that makes more sence for being fluid sloshing about in the reservoir more than a burst in the system...... still, at least you know that the warning system works for if you do get a leak!!!!