Newbie question

[DeanB]

2 hours ago, duncx said:

Listen to Dean, he is a driving God and my personal hero 

Dunc is obvs taking the p***! 

🤣🤣🤣

[Oakman]

1 hour ago, DeanB said:

Dunc is obvs taking the p***! 

🤣🤣🤣

Don't think so Dean - he's even got a pic of you on his wall.....

 

😉

[Andy wright]

Today’s fun centred on filling the cooling system and then bleeding it. Nice easy ten minute job. 90 minutes later and finally both sides of the radiator warmed up and the heater did what it was supposed to do ( heat ) . And no leaks . But I am still not certain that I have  all the air out so will resume that fight another day . Front calipers now on and connected, but I forgot about the pad retaining pins so had to clean those . I should have bought new ones but the novelty of spending more on it has definitely worn off. Even though I do  keep looking at exhaust systems and nice dampers and Yokohama A0 52 tyres ………..

[Lithopsian]

Locking the fronts can be an issue, but a lot of it is in how your apply the brakes.  The braking system on the Elises is heavily biased to the front, partly through the hydraulics and partly the big(-ish) front calipers vs the measly rear ones.  It works well if you apply the brakes progressively and transfer weight to the front, but stamping on the brakes can easily lock them which is quite hairy!  If you ever get chance to test the brakes on a rolling road (like the UK MOT) or even just to watch, it is comical how easily the front calipers lock with no weight transfer, and all-but-impossible to lock the rears without un-weighting the back end (maybe with a stronger right leg than mine?).

[Lithopsian]

Bleeding the coolant can be fairly easy, but it can also be a pain.  On the S1, which is largely the same, I don't have much trouble with the following method:

1 Fill the engine, just pour it in with the top pipe bleed screw out until water starts to come out.  Shouldn't have a problem with this.  Make sure you can reach the front bleed screw for later.  Easy with the clam off, but you might need to remove the radiator fence or arch liner if you have bulky arms.

2. Run the engine until the heater matrix (the bypass circuit on the K-series) gets warm.  You might need to increase revs to a fast idle to push any air through.  If the matrix has been drained, it will help a lot to manually fill it before you attach the hoses.

3. Wait for the coolant to reach your stat opening temperature.  If this happens very fast, double-check that you don't have an airlock in the heater circuit.  I use this time to raise the front of the car.  My drive has a convenient slope for this.  This can take quite a while at idle, you can move it along with a few more revs.

4. Open the front bleed screw and let any air out.  Let the coolant temperature rise until the fan kicks in (on the S1 you can check the fan works beforehand by unplugging the coolant sensor, I think the S2 is the same).  Keep an eye on the temperature and if the radiator won't warm up then try the bleed screw again.  This should all work smoothly with the front of the car raised, otherwise you might have to play around squeezing hoses to move air-locks.

5. When the fan goes off, try the bleed screw again.  You should be done.  Cycle the temperature again if you're unsure.  At all times, make sure you keep the header tank topped up so you don't suck any air in.  The K-series has some self-bleeding capability that should take tiny bubbles out of the system over time, so long as you don't have any air-locks.

Things might work slightly differently if you have a PRRT, electric pump, or other mods in the circuit.

[Andy wright]

Afternoon. Thank you for both of your above posts. Very helpful. I think I more or less stumbled on your bleed process by trial and error. Certainly upping the revs helped and yes, it took an age for the airlock to leave the heater matrix, but by the end of my session, the rad was hot at both ends and the heater was hot. Header tank was pretty full until the last few moments so I need to top up before attempting a re start . 
As for the brakes , the rears are 38mm piston ( I think ) and the fronts 44mm so yes, I see your point on the front bias . I have o.e m Calipers, ditto discs ( which ere bloody heavy ) and Mintex 1144 pads so an almost stock system. When I drove the car before pulling it apart I thought that the brakes felt pretty decent ( almost to my surprise ) . Some two piece lighter rotors from ‘ Seriously Lotus ‘ would be nice, but they will have to wait. 

[Lithopsian]

The piston size doesn't entirely tell the story.  The front calipers are two-pot, the rears a single sliding piston, and the front calipers each have a feed from the master cylinder while the rears share a single feed of the same diameter.  The overall difference is pretty big, mostly by design; you really don't want the rears locking up first.

[Andy wright]

Morning. Don’t want to get into a massive debate here, but single vs double piston makes no material difference  to clamping force * force, though it does to pedal feel as the sliding caliper is less rigid. Ditto single vs double line feed as the hydraulic pressure will be exactly the same whether split or bridged. As it happens , on my S2 there is a separate feed to each caliper via the abs unit. . What does have an effect is pad  swept area and effective disc radius as both of those influence braking torque along with maximum line pressure and piston area. Front and rear discs are the same diameter but the rears have much less pad depth and a smaller piston so yes, I agree, the system is front biased.The rear pad area will also influence the rate of heat transfer . In the end , Lotus will have done their sums very carefully when they designed the S1 , along with lots of testing. On my S2 , the system evolved with a servo, different master cylinder bore to suit  and the abs ( Kelsey Hayes ) , but I guess with the same caliper and disc geometry as the S1 and on a heavier car. 
Given other comments I have read about fitting different rear calipers and keeping the o.e caliper as a handbrake, with consequent handbrake lock on track days due to heat build up, the rears must be doing quite a bit of braking . As I don’t know the roll centre height relative to the c of g height, it’s hard to know what the weight transfer will be under braking. On my friends Elise race car , we have fitted four pots on the front and moved the front two pots to the rear, but , as it’s a race car, no need for a handbrake . It’s pedal box, balance bar and two master cylinders and on AO52 tyres the brakes hold up very well with excellent balance and modulation. But all that is a very different story from our ‘ everyday cars’. I agree that I do not want the car to swap ends under braking. I guess the abs doesn’t want that either, but I don’t plan to try to find out any time soon. 

[Lithopsian]

Fair enough, but I think you'll still find a strong front bias to your brakes

I'm curious though.  Why do bigger pistons make a difference, but more pistons don't?  I think the OEM Brembo calipers are 36mm, but can be machined out to 38mm.  EP used to sell them, but I just looked and they're showing as out of stock.  Probably best for my bank balance that way

On the S1, the front wheels are too small for bigger rotors (well maybe a few mm), but I think you have space for them? There are spacers for the calipers so you're actually increasing the swept area.  Still, the stock S1 brakes are quite capable of locking all four wheels on road tyres, so not much worth changing.  Except maybe weight!  One of the nice things on the early S1s was the MMC disks even if it is near impossible to get pads for them now.

[Oakman]

I believe Elise parts still do pads for MMC brake discs, I bought a full set from them a couple of years ago as I managed to source the discs for my '99 model year car.  Well worth doing if you can.  So much lighter still on the front end and the pedal feel is terrific.

The pads supplied are the newer ones made in America and work much better in the wet which was an issue with the original pads apparently.  I spoke with the American manufacturers about them, Elise Parts are their only reseller here.

 

[Andy wright]

15 minutes ago, Lithopsian said:

Fair enough, but I think you'll still find a strong front bias to your brakes

I'm curious though.  Why do bigger pistons make a difference, but more pistons don't?  I think the OEM Brembo calipers are 36mm, but can be machined out to 38mm.  EP used to sell them, but I just looked and they're showing as out of stock.  Probably best for my bank balance that way

On the S1, the front wheels are too small for bigger rotors (well maybe a few mm), but I think you have space for them? There are spacers for the calipers so you're actually increasing the swept area.  Still, the stock S1 brakes are quite capable of locking all four wheels on road tyres, so not much worth changing.  Except maybe weight!  One of the nice things on the early S1s was the MMC disks even if it is near impossible to get pads for them now.

Your S1 has those very nice rotors. The rest of us are stuck with the single piece jobs that are distinctly not light. Seriously Lotus do some very nice two piece rotors for both front and rear but my bank balance cannot tolerate that shock either. As for single vs multiple pistons , a single piston sliding caliper of, say, 36mm diameter will create exactly the same clamping force as a dual opposed piston caliper with the same piston dimensions. The sliding caliper is less rigid than the dual opposed caliper and often tend to run a bit more pad knock back, but not by much. Increasing the piston diameter will increase the force on the pad and therefore on the rotor given the same hydraulic line pressure. Going to a smaller piston  size but increasing the number to ,say, a 4 pot gives a number of advantages, including greater total piston area ( see 2 valve vs 4 Valve cylinder head designs ) but also much more even clamping force on the ( now longer ) pad. Having said all that , as you so rightly observe, if the system can lock up all four wheels , the job is more or less done . 
And on another note, brakes fitted and bled so now it’s time to replace the front clam .

[Andy wright]

Today was clamshell fitting day. So the front of the car got its clothes back on. As always, jobs take much longer, much longer than planned. The clam itself dropped into place quite easily and I had all the new bolts ready and all the captive nuts thread - chased and, in one case, drilled out a sheared 6mm bolt and re-tapped the thread. The drama started when I began to tighten up the bolt at secures the ‘A’ post edge of the clam to the rear edge of the ‘A’ post cover . I dropped my spanner which immediately ran off and hid in the gap between the inner sill and the ‘A’ post cover. Bother, have to take the cover off the retrieve spanner.Yes, the bottom two bolts that screw into captive nuts both sheared, despite my best efforts with ‘Plus Gas ‘ and care . Drilling those out and re- tapping was more joy . 

[Andy wright]

Back on its wheels test day afternoon. The bolts for the clamshell on the A post still need tightening but I need the car outside to do that with the doors wide open. Tracking to check before the diffuser goes back on and the hardtop needs its headlining  replacing. But otherwise, a trial drive up the road early next week if it is dry. 

[Andy wright]

And it needs a windscreen wiper and the inspection access covers . Oh, and a good clean inside and out . So not quite there yet …………

[Andy wright]

And it needs a windscreen wiper and the inspection access covers . Oh, and a good clean inside and out . So not quite there yet …………