I’ve recently fitted plus 2 brakes to the front of my sprint. The results are somewhat disappointing- the car stops but doesn’t exactly inspire confidence particularly when compared to the std setup with the servo. I should add that I’ve removed the servo.
I used new calipers, discs and pads so any faults/problems with these can probably be discounted. Comments on this conversion from others who’d done the same conversion suggested that it was a worthwhile mod.
Is it a case of my being too used to a servoed system and that I’ll “adjust” in time or could it be something as simple as me using the wrong pad material- I’ve fitted plus 2 pads but these are probably for a servoed system also- are there alternatives with softer linings. Admittedly I’ve only covered around 20 miles with the new setup so is it likely that the pads/discs require “bedding in” before improved stopping results?
I would say that the pedal pressure required is definitely higher now for a given stopping rate and I’m not sure I could even lock the wheels on a dry road (I’ve not tried yet). The pedal has the usual amount of free movement in it before feeling any resistance, there is no pad knock-off caused by too loose wheel bearings and none of the hoses are ballooning and I’m 100% certain there’s no air in the system.
I’ve been running your exact set-up for a couple of years and it works fine; pedal feels “firm” compared to how it was before. I’m using standard pads and can lock the front wheels in the dry.
Steve WW also converted around the same time as myself; there is quite a bit of discussion in the archive.
I would give it some time to bed in.
We have a +2 which we rebuilt everything a couple years back. Removed the servo, rebuilt all calipers, changed rubber line to aeroflex, turned rotors and all new pads and converted to silicon fluid. At first it took a bit to bed all pads in, but it will stop on a dime with a very solid pedal. I think it is more firm than with the boosters, might be just in my mind.
I would agree with Pete and let them work in a while.
I know it is not the same as puting them on a baby Elan but thought it might help.
Did you keep the same master cylinder? If so, you will have a noticeably less sensitive pedal than you did with the booster. If you change the master to a smaller diameter (I think 5/8’ from the 3/4" with the booster) you will have an appropriate effort level and a nice firm pedal. I did this when I removed the leaking unobtanium boosters from my plus 2 and am delighted with the result.
I think I’ll follow your advice and give the system a chance to “settle”. The comment about reducing the master cyl to 5/8ths is interesting- do you know if the standard (ie non se) S4 was equipped with the smaller unit as I once owned one (my first elan)- this was unservoed but I don’t recall ever having problems with stopping it.
Hi John
A 5/8 " master brake cylinder was used on early S1’s and Lotus went to a .7 inch master when the front brakes were were changed from SP12 to LF14 front calipers at 26/4108. The Sprint (RHD) used a .7 inch master also, I do not think your issue is with the hydraulics but going to a 5/8 inch master will make the brake pedal easier to push on. I would guess that a good set of after market pads would help alot. My first idea of what to try is the same as the others, that is to go and use the brakes for a while and see if they improve. If they do not, then buy a decent set of high performance pads from a company that does nothing but brake pads.
I have completed the same change as you about a year ago and had much the same thoughts as you…since then I have changed my front pads and use the ‘green stuff’ with a noticable difference to my braking. I must also add that if you change from a 3/4" to 5/8" master cyl you will increase the amount of pedal travel for the same braking. The plus 2 calliper pistons are of a larder diamiter and so need more volume of fluid to push them forward…if you use a smaller dia master cyl then you have to push it alot further to dispace the same amount of fuid and even more for the increased use of the larger calipers. hope this assists, regards George…
Hi George
There is not a lot of brake fluid volume to move with the Elan, the pads ride next to the rotors and don’t need to move far to work well (unless you have a warped rotor that causes the pads to be knocked back into the caliper bore). This is pressure related for the most part and not volume dependent. If the Elan had drums in the back (like the Europa) it would be more of an issue.
I did everything I could think of to reduce volume, areoquip lines, new discs, helper springs under the pistons. I put in a 5/8" master, but to me the pedal travel was excessive, so I went back to 7/8"
BTW Tilton do a range of master cylinders which fit the +2
I also have this set up on my +2, I have greenstuff pads, no servo, goodridge hoses and mineral brake fluid.
With the .7" m/cyl the brakes were very wooden and inspired little confidence on initial application, since fitting the .625" m/cyl they have been transformed the pedal efforts are now very similar to the servo’d system and the pedal is rock hard with no excessive travel, if you have too much travel I would check the disc run out and the rear calipers, mine were in a real state neeeding 4 new pistons, also the pedal box pivots can wear causing a suprsing amout of free travel.
Finaly if you decide to change the m/cyl you should realy get one with a larger fluid reservior, I used one where you can screw the reservoir in, the only thing I still need to do is modify a fluid level switch for it.
When I did the conversion it initially took a little while for everything to bed in. I am using EBC Green Stuff on the front and Black on the rear.
The pedal is firmer and requires more shove than with the servo but locking the wheels in the dry is not a problem. The firmer pedal gives more feel and makes doing heel’n’toe down changes so much easier.
See if your current pads bed in first. If not try changing to something like Green Stuff or Mintex do a similar pad but I can not remember the number.
I will be coming at this from the other direction when I switch over to +2 brakes next winter. The S2 has the .7 MC and no servo. The pedal is like stepping on a granite curbstone but the effort is quite high and I’ve never felt the brakes were working as hard as they should for the effort. With the rebuild almost complete, I’ll have freshly reconditioned front calipers for a year. Meanwhile I have +2 components on the shelf for rebuilding and I’ll swap them in as a winter project. I expect a bit more stop for a bit less effort, little or no loss in pedal feel, and better balance. I’ll report back next year.
Excessive clearance in the front wheel bearings is also something to watch for. The Lotus workshop manual is a bit deceiving. IIRC, the manual tells you to run the slotted nut up until a certain end float is measured then back off the nut until a cotter pin can go throught the stub axle. I did this and got a lot of brake pedal travel on first application. Now I run the slotted nut up until I feel some drag in the bearings and then back off to fit the cotter pin. I check to see that there are a few thousandths of end float after doing up the cotter pin. This reduced brake pedal travel quite a bit.
Yes, Russ, you’re right, I forgot to mention this. What the manual says is set the end-float (measured at the hub face) to 0.002 - 0.004 in, then back off a flat, then insert a new split-pin. However, backing off the nut a flat does not guarantee the split-pin will line up with the drilling, and that amount of axial float seems to give a very sloppy fit.
Then, in another section of the manual, it says tighten the hub nut to 5 -6 ft lbs, and again slacken one flat and replace the pin.
You are right again, it makes much more sense to check AFTER replacing the pin. I check for the very minimum at the rim of the brake disc, and file off the face of the nut if necessary to get the pin to line up.
I like the tighten, slacken one flat method. Given the amount of adjustment available, you don’t want to wind up too loose. Key is that the slackening actually frees the bearings from binding. You need to notice this by spinning the rotor with the tire off. And no, this method is still not all that likely to result in the specified amount of runout, which will only be obtained with blind luck.
Going from assisted brakes to unassisted ones can be an adjustment. My Europa requires a seriously mashed pedal to stop. But it does, and I appreciate that I’m very unlikely to lock a wheel inadvertently. Key here is that the extra stress on pedal and mount don’t result in a disastrous failure of either. Absent that, I’ll opine that you can adjust and learn to love the braking.
Not to start another war, but it seems doubtful to me that under anything but race conditions the extra stopping power of the GT6/+2 brakes would amount to a noticeable improvement in stopping capability. The brake set was designed to stop a much heavier car (the Spitfire) and in my recollection from days gone by, did so quite adequately. But I do appreciate the love of fiddling.
The manual procedure for setting up the front hub results in a slack bearing with an amount of play, the hub will spin freely; yet the very similar bearing set up (conical rollers) in the diff pinion has a substantial preload set to give a torque of 9 -11 ft lbs.
I wonder what is the reason for this big difference ?
The increased area of the +2 brake set up dissipates the heat better. It is not down to how hard you can clamp the disk but how quickly you can get rid of the heat produced by the braking effort, hence vented disks.
For me the big advantage of the +2 set up is the loss of the servo (no need for one due to the larger piston area giving better mechanical advantage) and the increase in front bias. You get a better pedal feel with out the servo and the extra front bias reduces the tendency of the rears to lock under extreme braking.
Sean
The end float in the front hubs is to allow for the hub expansion under heat from braking. Not enough end float and you get excessive preload on the bearings the when brakes very hot leading to premature failure.
The diff input bearings do not suffer from high temperatures plus you need precise location between crown wheel and pinion hence the use of a specific preload that eliminates end float but prevents excessive load as the diff warms up.
